diff --git a/.gitignore b/.gitignore
index 8521b33af..1d0edde80 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,3 +12,7 @@ packages/core-bridge/releases
 packages/*/package-lock.json
 /sdk-node.iml
 *~
+
+# One test creates persisted SQLite DBs; they should normally be deleted automatically,
+# but may be left behind in some error scenarios.
+packages/test/temporal-db-*.sqlite
diff --git a/packages/common/src/errors.ts b/packages/common/src/errors.ts
index d28368289..aa5dd2c59 100644
--- a/packages/common/src/errors.ts
+++ b/packages/common/src/errors.ts
@@ -20,7 +20,8 @@ export class ValueError extends Error {
 export class PayloadConverterError extends ValueError {}
 
 /**
- * Used in different parts of the SDK to note that something unexpected has happened.
+ * Signals that a requested operation can't be completed because it is illegal given the
+ * current state of the object; e.g. trying to use a resource after it has been closed.
  */
 @SymbolBasedInstanceOfError('IllegalStateError')
 export class IllegalStateError extends Error {}
diff --git a/packages/core-bridge/Cargo.lock b/packages/core-bridge/Cargo.lock
index 2a6782fba..3500e2d98 100644
--- a/packages/core-bridge/Cargo.lock
+++ b/packages/core-bridge/Cargo.lock
@@ -51,9 +51,9 @@ checksum = "55cc3b69f167a1ef2e161439aa98aed94e6028e5f9a59be9a6ffb47aef1651f9"
 
 [[package]]
 name = "anyhow"
-version = "1.0.97"
+version = "1.0.98"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcfed56ad506cb2c684a14971b8861fdc3baaaae314b9e5f9bb532cbe3ba7a4f"
+checksum = "e16d2d3311acee920a9eb8d33b8cbc1787ce4a264e85f964c2404b969bdcd487"
 
 [[package]]
 name = "arbitrary"
@@ -88,9 +88,9 @@ dependencies = [
 
 [[package]]
 name = "async-trait"
-version = "0.1.87"
+version = "0.1.88"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d556ec1359574147ec0c4fc5eb525f3f23263a592b1a9c07e0a75b427de55c97"
+checksum = "e539d3fca749fcee5236ab05e93a52867dd549cc157c8cb7f99595f3cedffdb5"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -179,7 +179,7 @@ dependencies = [
  "miniz_oxide",
  "object",
  "rustc-demangle",
- "windows-targets",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
@@ -203,6 +203,16 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "bridge-macros"
+version = "0.1.0"
+dependencies = [
+ "convert_case",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "bumpalo"
 version = "3.17.0"
@@ -217,9 +227,9 @@ checksum = "1fd0f2584146f6f2ef48085050886acf353beff7305ebd1ae69500e27c67f64b"
 
 [[package]]
 name = "bytes"
-version = "1.10.0"
+version = "1.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f61dac84819c6588b558454b194026eb1f09c293b9036ae9b159e74e73ab6cf9"
+checksum = "d71b6127be86fdcfddb610f7182ac57211d4b18a3e9c82eb2d17662f2227ad6a"
 
 [[package]]
 name = "bzip2"
@@ -242,9 +252,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.2.16"
+version = "1.2.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "be714c154be609ec7f5dad223a33bf1482fff90472de28f7362806e6d4832b8c"
+checksum = "8e3a13707ac958681c13b39b458c073d0d9bc8a22cb1b2f4c8e55eb72c13f362"
 dependencies = [
  "jobserver",
  "libc",
@@ -289,6 +299,15 @@ version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7c74b8349d32d297c9134b8c88677813a227df8f779daa29bfc29c183fe3dca6"
 
+[[package]]
+name = "convert_case"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ec182b0ca2f35d8fc196cf3404988fd8b8c739a4d270ff118a398feb0cbec1ca"
+dependencies = [
+ "unicode-segmentation",
+]
+
 [[package]]
 name = "core-foundation"
 version = "0.10.0"
@@ -340,9 +359,9 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-channel"
-version = "0.5.14"
+version = "0.5.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "06ba6d68e24814cb8de6bb986db8222d3a027d15872cabc0d18817bc3c0e4471"
+checksum = "82b8f8f868b36967f9606790d1903570de9ceaf870a7bf9fbbd3016d636a2cb2"
 dependencies = [
  "crossbeam-utils",
 ]
@@ -374,9 +393,9 @@ dependencies = [
 
 [[package]]
 name = "darling"
-version = "0.20.10"
+version = "0.20.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6f63b86c8a8826a49b8c21f08a2d07338eec8d900540f8630dc76284be802989"
+checksum = "fc7f46116c46ff9ab3eb1597a45688b6715c6e628b5c133e288e709a29bcb4ee"
 dependencies = [
  "darling_core",
  "darling_macro",
@@ -384,9 +403,9 @@ dependencies = [
 
 [[package]]
 name = "darling_core"
-version = "0.20.10"
+version = "0.20.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "95133861a8032aaea082871032f5815eb9e98cef03fa916ab4500513994df9e5"
+checksum = "0d00b9596d185e565c2207a0b01f8bd1a135483d02d9b7b0a54b11da8d53412e"
 dependencies = [
  "fnv",
  "ident_case",
@@ -398,9 +417,9 @@ dependencies = [
 
 [[package]]
 name = "darling_macro"
-version = "0.20.10"
+version = "0.20.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d336a2a514f6ccccaa3e09b02d41d35330c07ddf03a62165fcec10bb561c7806"
+checksum = "fc34b93ccb385b40dc71c6fceac4b2ad23662c7eeb248cf10d529b7e055b6ead"
 dependencies = [
  "darling_core",
  "quote",
@@ -429,9 +448,9 @@ checksum = "da692b8d1080ea3045efaab14434d40468c3d8657e42abddfffca87b428f4c1b"
 
 [[package]]
 name = "deranged"
-version = "0.3.11"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b42b6fa04a440b495c8b04d0e71b707c585f83cb9cb28cf8cd0d976c315e31b4"
+checksum = "9c9e6a11ca8224451684bc0d7d5a7adbf8f2fd6887261a1cfc3c0432f9d4068e"
 dependencies = [
  "powerfmt",
 ]
@@ -529,9 +548,9 @@ checksum = "1435fa1053d8b2fbbe9be7e97eca7f33d37b28409959813daefc1446a14247f1"
 
 [[package]]
 name = "either"
-version = "1.14.0"
+version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b7914353092ddf589ad78f25c5c1c21b7f80b0ff8621e7c814c3485b5306da9d"
+checksum = "48c757948c5ede0e46177b7add2e67155f70e33c07fea8284df6576da70b3719"
 
 [[package]]
 name = "enum-iterator"
@@ -583,9 +602,9 @@ dependencies = [
 
 [[package]]
 name = "errno"
-version = "0.3.10"
+version = "0.3.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "33d852cb9b869c2a9b3df2f71a3074817f01e1844f839a144f5fcef059a4eb5d"
+checksum = "976dd42dc7e85965fe702eb8164f21f450704bdde31faefd6471dba214cb594e"
 dependencies = [
  "libc",
  "windows-sys 0.59.0",
@@ -617,9 +636,9 @@ checksum = "1d674e81391d1e1ab681a28d99df07927c6d4aa5b027d7da16ba32d1d21ecd99"
 
 [[package]]
 name = "flate2"
-version = "1.1.0"
+version = "1.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "11faaf5a5236997af9848be0bef4db95824b1d534ebc64d0f0c6cf3e67bd38dc"
+checksum = "7ced92e76e966ca2fd84c8f7aa01a4aea65b0eb6648d72f7c8f3e2764a67fece"
 dependencies = [
  "crc32fast",
  "miniz_oxide",
@@ -633,9 +652,9 @@ checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
 
 [[package]]
 name = "foldhash"
-version = "0.1.4"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a0d2fde1f7b3d48b8395d5f2de76c18a528bd6a9cdde438df747bfcba3e05d6f"
+checksum = "d9c4f5dac5e15c24eb999c26181a6ca40b39fe946cbe4c263c7209467bc83af2"
 
 [[package]]
 name = "form_urlencoded"
@@ -648,9 +667,9 @@ dependencies = [
 
 [[package]]
 name = "fragile"
-version = "2.0.0"
+version = "2.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6c2141d6d6c8512188a7891b4b01590a45f6dac67afb4f255c4124dbb86d4eaa"
+checksum = "28dd6caf6059519a65843af8fe2a3ae298b14b80179855aeb4adc2c1934ee619"
 
 [[package]]
 name = "futures"
@@ -783,16 +802,16 @@ dependencies = [
 
 [[package]]
 name = "getrandom"
-version = "0.3.1"
+version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "43a49c392881ce6d5c3b8cb70f98717b7c07aabbdff06687b9030dbfbe2725f8"
+checksum = "73fea8450eea4bac3940448fb7ae50d91f034f941199fcd9d909a5a07aa455f0"
 dependencies = [
  "cfg-if",
  "js-sys",
  "libc",
- "wasi 0.13.3+wasi-0.2.2",
+ "r-efi",
+ "wasi 0.14.2+wasi-0.2.4",
  "wasm-bindgen",
- "windows-targets",
 ]
 
 [[package]]
@@ -818,7 +837,7 @@ dependencies = [
  "futures-sink",
  "futures-timer",
  "futures-util",
- "getrandom 0.3.1",
+ "getrandom 0.3.2",
  "no-std-compat",
  "nonzero_ext",
  "parking_lot",
@@ -832,9 +851,9 @@ dependencies = [
 
 [[package]]
 name = "h2"
-version = "0.4.8"
+version = "0.4.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5017294ff4bb30944501348f6f8e42e6ad28f42c8bbef7a74029aff064a4e3c2"
+checksum = "75249d144030531f8dee69fe9cea04d3edf809a017ae445e2abdff6629e86633"
 dependencies = [
  "atomic-waker",
  "bytes",
@@ -842,7 +861,7 @@ dependencies = [
  "futures-core",
  "futures-sink",
  "http",
- "indexmap 2.7.1",
+ "indexmap 2.9.0",
  "slab",
  "tokio",
  "tokio-util",
@@ -889,9 +908,9 @@ dependencies = [
 
 [[package]]
 name = "http"
-version = "1.2.0"
+version = "1.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f16ca2af56261c99fba8bac40a10251ce8188205a4c448fbb745a2e4daa76fea"
+checksum = "f4a85d31aea989eead29a3aaf9e1115a180df8282431156e533de47660892565"
 dependencies = [
  "bytes",
  "fnv",
@@ -910,12 +929,12 @@ dependencies = [
 
 [[package]]
 name = "http-body-util"
-version = "0.1.2"
+version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "793429d76616a256bcb62c2a2ec2bed781c8307e797e2598c50010f2bee2544f"
+checksum = "b021d93e26becf5dc7e1b75b1bed1fd93124b374ceb73f43d4d4eafec896a64a"
 dependencies = [
  "bytes",
- "futures-util",
+ "futures-core",
  "http",
  "http-body",
  "pin-project-lite",
@@ -987,9 +1006,9 @@ dependencies = [
 
 [[package]]
 name = "hyper-util"
-version = "0.1.10"
+version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df2dcfbe0677734ab2f3ffa7fa7bfd4706bfdc1ef393f2ee30184aed67e631b4"
+checksum = "497bbc33a26fdd4af9ed9c70d63f61cf56a938375fbb32df34db9b1cd6d643f2"
 dependencies = [
  "bytes",
  "futures-channel",
@@ -997,6 +1016,7 @@ dependencies = [
  "http",
  "http-body",
  "hyper",
+ "libc",
  "pin-project-lite",
  "socket2",
  "tokio",
@@ -1045,9 +1065,9 @@ dependencies = [
 
 [[package]]
 name = "icu_locid_transform_data"
-version = "1.5.0"
+version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fdc8ff3388f852bede6b579ad4e978ab004f139284d7b28715f773507b946f6e"
+checksum = "7515e6d781098bf9f7205ab3fc7e9709d34554ae0b21ddbcb5febfa4bc7df11d"
 
 [[package]]
 name = "icu_normalizer"
@@ -1069,9 +1089,9 @@ dependencies = [
 
 [[package]]
 name = "icu_normalizer_data"
-version = "1.5.0"
+version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f8cafbf7aa791e9b22bec55a167906f9e1215fd475cd22adfcf660e03e989516"
+checksum = "c5e8338228bdc8ab83303f16b797e177953730f601a96c25d10cb3ab0daa0cb7"
 
 [[package]]
 name = "icu_properties"
@@ -1090,9 +1110,9 @@ dependencies = [
 
 [[package]]
 name = "icu_properties_data"
-version = "1.5.0"
+version = "1.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "67a8effbc3dd3e4ba1afa8ad918d5684b8868b3b26500753effea8d2eed19569"
+checksum = "85fb8799753b75aee8d2a21d7c14d9f38921b54b3dbda10f5a3c7a7b82dba5e2"
 
 [[package]]
 name = "icu_provider"
@@ -1161,9 +1181,9 @@ dependencies = [
 
 [[package]]
 name = "indexmap"
-version = "2.7.1"
+version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8c9c992b02b5b4c94ea26e32fe5bccb7aa7d9f390ab5c1221ff895bc7ea8b652"
+checksum = "cea70ddb795996207ad57735b50c5982d8844f38ba9ee5f1aedcfb708a2aa11e"
 dependencies = [
  "equivalent",
  "hashbrown 0.15.2",
@@ -1219,10 +1239,11 @@ checksum = "4a5f13b858c8d314ee3e8f639011f7ccefe71f97f96e50151fb991f267928e2c"
 
 [[package]]
 name = "jobserver"
-version = "0.1.32"
+version = "0.1.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "48d1dbcbbeb6a7fec7e059840aa538bd62aaccf972c7346c4d9d2059312853d0"
+checksum = "38f262f097c174adebe41eb73d66ae9c06b2844fb0da69969647bbddd9b0538a"
 dependencies = [
+ "getrandom 0.3.2",
  "libc",
 ]
 
@@ -1244,9 +1265,9 @@ checksum = "bbd2bcb4c963f2ddae06a2efc7e9f3591312473c50c6685e1f298068316e66fe"
 
 [[package]]
 name = "libc"
-version = "0.2.170"
+version = "0.2.172"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "875b3680cb2f8f71bdcf9a30f38d48282f5d3c95cbf9b3fa57269bb5d5c06828"
+checksum = "d750af042f7ef4f724306de029d18836c26c1765a54a6a3f094cbd23a7267ffa"
 
 [[package]]
 name = "libloading"
@@ -1255,7 +1276,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fc2f4eb4bc735547cfed7c0a4922cbd04a4655978c09b54f1f7b228750664c34"
 dependencies = [
  "cfg-if",
- "windows-targets",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
@@ -1271,9 +1292,9 @@ dependencies = [
 
 [[package]]
 name = "linux-raw-sys"
-version = "0.4.15"
+version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d26c52dbd32dccf2d10cac7725f8eae5296885fb5703b261f7d0a0739ec807ab"
+checksum = "cd945864f07fe9f5371a27ad7b52a172b4b499999f1d97574c9fa68373937e12"
 
 [[package]]
 name = "litemap"
@@ -1299,9 +1320,9 @@ checksum = "9374ef4228402d4b7e403e5838cb880d9ee663314b0a900d5a6aabf0c213552e"
 
 [[package]]
 name = "log"
-version = "0.4.26"
+version = "0.4.27"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "30bde2b3dc3671ae49d8e2e9f044c7c005836e7a023ee57cffa25ab82764bb9e"
+checksum = "13dc2df351e3202783a1fe0d44375f7295ffb4049267b0f3018346dc122a1d94"
 
 [[package]]
 name = "lru"
@@ -1322,6 +1343,17 @@ dependencies = [
  "crc",
 ]
 
+[[package]]
+name = "lzma-sys"
+version = "0.1.20"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5fda04ab3764e6cde78b9974eec4f779acaba7c4e84b36eca3cf77c581b85d27"
+dependencies = [
+ "cc",
+ "libc",
+ "pkg-config",
+]
+
 [[package]]
 name = "matchers"
 version = "0.1.0"
@@ -1351,9 +1383,9 @@ checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
 
 [[package]]
 name = "miniz_oxide"
-version = "0.8.5"
+version = "0.8.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8e3e04debbb59698c15bacbb6d93584a8c0ca9cc3213cb423d31f760d8843ce5"
+checksum = "3be647b768db090acb35d5ec5db2b0e1f1de11133ca123b9eacf5137868f892a"
 dependencies = [
  "adler2",
 ]
@@ -1484,9 +1516,9 @@ dependencies = [
 
 [[package]]
 name = "once_cell"
-version = "1.20.3"
+version = "1.21.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "945462a4b81e43c4e3ba96bd7b49d834c6f61198356aa858733bc4acf3cbe62e"
+checksum = "42f5e15c9953c5e4ccceeb2e7382a716482c34515315f7b03532b8b4e8393d2d"
 
 [[package]]
 name = "openssl-probe"
@@ -1494,20 +1526,6 @@ version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d05e27ee213611ffe7d6348b942e8f942b37114c00cc03cec254295a4a17852e"
 
-[[package]]
-name = "opentelemetry"
-version = "0.24.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4c365a63eec4f55b7efeceb724f1336f26a9cf3427b70e59e2cd2a5b947fba96"
-dependencies = [
- "futures-core",
- "futures-sink",
- "js-sys",
- "once_cell",
- "pin-project-lite",
- "thiserror 1.0.69",
-]
-
 [[package]]
 name = "opentelemetry"
 version = "0.26.0"
@@ -1531,7 +1549,7 @@ dependencies = [
  "async-trait",
  "bytes",
  "http",
- "opentelemetry 0.26.0",
+ "opentelemetry",
  "reqwest",
 ]
 
@@ -1544,7 +1562,7 @@ dependencies = [
  "async-trait",
  "futures-core",
  "http",
- "opentelemetry 0.26.0",
+ "opentelemetry",
  "opentelemetry-http",
  "opentelemetry-proto",
  "opentelemetry_sdk",
@@ -1561,7 +1579,7 @@ version = "0.17.0"
 source = "git+https://github.com/open-telemetry/opentelemetry-rust.git?rev=e911383#e91138351a689cd21923c15eb48f5fbc95ded807"
 dependencies = [
  "once_cell",
- "opentelemetry 0.26.0",
+ "opentelemetry",
  "opentelemetry_sdk",
  "prometheus",
  "protobuf",
@@ -1573,7 +1591,7 @@ version = "0.26.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c9d3968ce3aefdcca5c27e3c4ea4391b37547726a70893aab52d3de95d5f8b34"
 dependencies = [
- "opentelemetry 0.26.0",
+ "opentelemetry",
  "opentelemetry_sdk",
  "prost",
  "tonic",
@@ -1591,7 +1609,7 @@ dependencies = [
  "futures-util",
  "glob",
  "once_cell",
- "opentelemetry 0.26.0",
+ "opentelemetry",
  "percent-encoding",
  "rand 0.8.5",
  "serde_json",
@@ -1626,7 +1644,7 @@ dependencies = [
  "libc",
  "redox_syscall",
  "smallvec",
- "windows-targets",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
@@ -1652,7 +1670,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3672b37090dbd86368a4145bc067582552b29c27377cad4e0a306c97f9bd7772"
 dependencies = [
  "fixedbitset",
- "indexmap 2.7.1",
+ "indexmap 2.9.0",
 ]
 
 [[package]]
@@ -1708,6 +1726,15 @@ version = "1.11.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "350e9b48cbc6b0e028b0473b114454c6316e57336ee184ceab6e53f72c178b3e"
 
+[[package]]
+name = "portable-atomic-util"
+version = "0.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d8a2f0d8d040d7848a709caf78912debcc3f33ee4b3cac47d73d1e1069e83507"
+dependencies = [
+ "portable-atomic",
+]
+
 [[package]]
 name = "powerfmt"
 version = "0.2.0"
@@ -1716,11 +1743,11 @@ checksum = "439ee305def115ba05938db6eb1644ff94165c5ab5e9420d1c1bcedbba909391"
 
 [[package]]
 name = "ppv-lite86"
-version = "0.2.20"
+version = "0.2.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "77957b295656769bb8ad2b6a6b09d897d94f05c41b069aede1fcdaa675eaea04"
+checksum = "85eae3c4ed2f50dcfe72643da4befc30deadb458a9b590d720cde2f2b1e97da9"
 dependencies = [
- "zerocopy 0.7.35",
+ "zerocopy",
 ]
 
 [[package]]
@@ -1751,9 +1778,9 @@ dependencies = [
 
 [[package]]
 name = "prettyplease"
-version = "0.2.30"
+version = "0.2.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f1ccf34da56fc294e7d4ccf69a85992b7dfb826b7cf57bac6a70bba3494cc08a"
+checksum = "664ec5419c51e34154eec046ebcba56312d5a2fc3b09a06da188e1ad21afadf6"
 dependencies = [
  "proc-macro2",
  "syn",
@@ -1761,9 +1788,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.94"
+version = "1.0.95"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a31971752e70b8b2686d7e46ec17fb38dad4051d94024c88df49b667caea9c84"
+checksum = "02b3e5e68a3a1a02aad3ec490a98007cbc13c37cbe84a3cd7b8e406d76e7f778"
 dependencies = [
  "unicode-ident",
 ]
@@ -1904,11 +1931,12 @@ dependencies = [
 
 [[package]]
 name = "quinn"
-version = "0.11.6"
+version = "0.11.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "62e96808277ec6f97351a2380e6c25114bc9e67037775464979f3037c92d05ef"
+checksum = "c3bd15a6f2967aef83887dcb9fec0014580467e33720d073560cf015a5683012"
 dependencies = [
  "bytes",
+ "cfg_aliases",
  "pin-project-lite",
  "quinn-proto",
  "quinn-udp",
@@ -1918,17 +1946,18 @@ dependencies = [
  "thiserror 2.0.12",
  "tokio",
  "tracing",
+ "web-time",
 ]
 
 [[package]]
 name = "quinn-proto"
-version = "0.11.9"
+version = "0.11.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a2fe5ef3495d7d2e377ff17b1a8ce2ee2ec2a18cde8b6ad6619d65d0701c135d"
+checksum = "b820744eb4dc9b57a3398183639c511b5a26d2ed702cedd3febaa1393caa22cc"
 dependencies = [
  "bytes",
- "getrandom 0.2.15",
- "rand 0.8.5",
+ "getrandom 0.3.2",
+ "rand 0.9.0",
  "ring",
  "rustc-hash",
  "rustls",
@@ -1942,9 +1971,9 @@ dependencies = [
 
 [[package]]
 name = "quinn-udp"
-version = "0.5.10"
+version = "0.5.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e46f3055866785f6b92bc6164b76be02ca8f2eb4b002c0354b28cf4c119e5944"
+checksum = "541d0f57c6ec747a90738a52741d3221f7960e8ac2f0ff4b1a63680e033b4ab5"
 dependencies = [
  "cfg_aliases",
  "libc",
@@ -1956,13 +1985,19 @@ dependencies = [
 
 [[package]]
 name = "quote"
-version = "1.0.39"
+version = "1.0.40"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c1f1914ce909e1658d9907913b4b91947430c7d9be598b15a1912935b8c04801"
+checksum = "1885c039570dc00dcb4ff087a89e185fd56bae234ddc7f056a945bf36467248d"
 dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "r-efi"
+version = "5.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "74765f6d916ee2faa39bc8e68e4f3ed8949b48cccdac59983d287a7cb71ce9c5"
+
 [[package]]
 name = "rand"
 version = "0.8.5"
@@ -1982,7 +2017,7 @@ checksum = "3779b94aeb87e8bd4e834cee3650289ee9e0d5677f976ecdb6d219e5f4f6cd94"
 dependencies = [
  "rand_chacha 0.9.0",
  "rand_core 0.9.3",
- "zerocopy 0.8.21",
+ "zerocopy",
 ]
 
 [[package]]
@@ -2020,23 +2055,23 @@ version = "0.9.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "99d9a13982dcf210057a8a78572b2217b667c3beacbf3a0d8b454f6f82837d38"
 dependencies = [
- "getrandom 0.3.1",
+ "getrandom 0.3.2",
 ]
 
 [[package]]
 name = "raw-cpuid"
-version = "11.4.0"
+version = "11.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "529468c1335c1c03919960dfefdb1b3648858c20d7ec2d0663e728e4a717efbc"
+checksum = "c6df7ab838ed27997ba19a4664507e6f82b41fe6e20be42929332156e5e85146"
 dependencies = [
  "bitflags",
 ]
 
 [[package]]
 name = "redox_syscall"
-version = "0.5.10"
+version = "0.5.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0b8c0c260b63a8219631167be35e6a988e9554dbd323f8bd08439c8ed1302bd1"
+checksum = "d2f103c6d277498fbceb16e84d317e2a400f160f46904d5f5410848c829511a3"
 dependencies = [
  "bitflags",
 ]
@@ -2087,9 +2122,9 @@ checksum = "2b15c43186be67a4fd63bee50d0303afffcef381492ebe2c5d87f324e1b8815c"
 
 [[package]]
 name = "reqwest"
-version = "0.12.12"
+version = "0.12.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "43e734407157c3c2034e0258f5e4473ddb361b1e85f95a66690d67264d7cd1da"
+checksum = "d19c46a6fdd48bc4dab94b6103fccc55d34c67cc0ad04653aad4ea2a07cd7bbb"
 dependencies = [
  "base64",
  "bytes",
@@ -2133,9 +2168,9 @@ dependencies = [
 
 [[package]]
 name = "ring"
-version = "0.17.11"
+version = "0.17.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da5349ae27d3887ca812fb375b45a4fbb36d8d12d2df394968cd86e35683fe73"
+checksum = "a4689e6c2294d81e88dc6261c768b63bc4fcdb852be6d1352498b114f61383b7"
 dependencies = [
  "cc",
  "cfg-if",
@@ -2147,12 +2182,13 @@ dependencies = [
 
 [[package]]
 name = "ringbuf"
-version = "0.4.7"
+version = "0.4.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "726bb493fe9cac765e8f96a144c3a8396bdf766dedad22e504b70b908dcbceb4"
+checksum = "fe47b720588c8702e34b5979cb3271a8b1842c7cb6f57408efa70c779363488c"
 dependencies = [
  "crossbeam-utils",
  "portable-atomic",
+ "portable-atomic-util",
 ]
 
 [[package]]
@@ -2192,9 +2228,9 @@ version = "0.1.0"
 
 [[package]]
 name = "rustix"
-version = "0.38.44"
+version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fdb5bc1ae2baa591800df16c9ca78619bf65c0488b41b96ccec5d11220d8c154"
+checksum = "d97817398dd4bb2e6da002002db259209759911da105da92bec29ccb12cf58bf"
 dependencies = [
  "bitflags",
  "errno",
@@ -2205,9 +2241,9 @@ dependencies = [
 
 [[package]]
 name = "rustls"
-version = "0.23.23"
+version = "0.23.26"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "47796c98c480fce5406ef69d1c76378375492c3b0a0de587be0c1d9feb12f395"
+checksum = "df51b5869f3a441595eac5e8ff14d486ff285f7b8c0df8770e49c3b56351f0f0"
 dependencies = [
  "log",
  "once_cell",
@@ -2250,9 +2286,9 @@ dependencies = [
 
 [[package]]
 name = "rustls-webpki"
-version = "0.102.8"
+version = "0.103.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "64ca1bc8749bd4cf37b5ce386cc146580777b4e8572c7b97baf22c83f444bee9"
+checksum = "fef8b8769aaccf73098557a87cd1816b4f9c7c16811c9c77142aa695c16f2c03"
 dependencies = [
  "ring",
  "rustls-pki-types",
@@ -2323,18 +2359,18 @@ checksum = "cd0b0ec5f1c1ca621c432a25813d8d60c88abe6d3e08a3eb9cf37d97a0fe3d73"
 
 [[package]]
 name = "serde"
-version = "1.0.218"
+version = "1.0.219"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e8dfc9d19bdbf6d17e22319da49161d5d0108e4188e8b680aef6299eed22df60"
+checksum = "5f0e2c6ed6606019b4e29e69dbaba95b11854410e5347d525002456dbbb786b6"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.218"
+version = "1.0.219"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f09503e191f4e797cb8aac08e9a4a4695c5edf6a2e70e376d961ddd5c969f82b"
+checksum = "5b0276cf7f2c73365f7157c8123c21cd9a50fbbd844757af28ca1f5925fc2a00"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2432,15 +2468,15 @@ dependencies = [
 
 [[package]]
 name = "smallvec"
-version = "1.14.0"
+version = "1.15.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7fcf8323ef1faaee30a44a340193b1ac6814fd9b7b4e88e9d4519a3e4abe1cfd"
+checksum = "8917285742e9f3e1683f0a9c4e6b57960b7314d0b08d30d1ecd426713ee2eee9"
 
 [[package]]
 name = "socket2"
-version = "0.5.8"
+version = "0.5.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c970269d99b64e60ec3bd6ad27270092a5394c4e309314b18ae3fe575695fbe8"
+checksum = "4f5fd57c80058a56cf5c777ab8a126398ece8e442983605d280a44ce79d0edef"
 dependencies = [
  "libc",
  "windows-sys 0.52.0",
@@ -2475,9 +2511,9 @@ checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
 
 [[package]]
 name = "syn"
-version = "2.0.99"
+version = "2.0.100"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e02e925281e18ffd9d640e234264753c43edc62d64b2d4cf898f1bc5e75f3fc2"
+checksum = "b09a44accad81e1ba1cd74a32461ba89dee89095ba17b32f5d03683b1b1fc2a0"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2541,13 +2577,12 @@ dependencies = [
 
 [[package]]
 name = "tempfile"
-version = "3.17.1"
+version = "3.19.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "22e5a0acb1f3f55f65cc4a866c361b2fb2a0ff6366785ae6fbb5f85df07ba230"
+checksum = "7437ac7763b9b123ccf33c338a5cc1bac6f69b45a136c19bdd8a65e3916435bf"
 dependencies = [
- "cfg-if",
  "fastrand",
- "getrandom 0.3.1",
+ "getrandom 0.3.2",
  "once_cell",
  "rustix",
  "windows-sys 0.59.0",
@@ -2606,7 +2641,7 @@ dependencies = [
  "itertools",
  "lru",
  "mockall",
- "opentelemetry 0.26.0",
+ "opentelemetry",
  "opentelemetry-otlp",
  "opentelemetry-prometheus",
  "opentelemetry_sdk",
@@ -2648,7 +2683,7 @@ dependencies = [
  "async-trait",
  "derive_builder",
  "derive_more",
- "opentelemetry 0.26.0",
+ "opentelemetry",
  "prost",
  "serde_json",
  "temporal-sdk-core-protos",
@@ -2683,18 +2718,21 @@ dependencies = [
 name = "temporal-sdk-typescript-bridge"
 version = "0.1.0"
 dependencies = [
+ "anyhow",
  "async-trait",
+ "bridge-macros",
  "futures",
  "log",
  "neon",
- "once_cell",
- "opentelemetry 0.24.0",
+ "opentelemetry",
  "parking_lot",
  "prost",
  "prost-types",
+ "serde",
  "serde_json",
  "temporal-client",
  "temporal-sdk-core",
+ "thiserror 2.0.12",
  "tokio",
  "tokio-stream",
 ]
@@ -2757,9 +2795,9 @@ dependencies = [
 
 [[package]]
 name = "time"
-version = "0.3.37"
+version = "0.3.41"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "35e7868883861bd0e56d9ac6efcaaca0d6d5d82a2a7ec8209ff492c07cf37b21"
+checksum = "8a7619e19bc266e0f9c5e6686659d394bc57973859340060a69221e57dbc0c40"
 dependencies = [
  "deranged",
  "num-conv",
@@ -2770,9 +2808,9 @@ dependencies = [
 
 [[package]]
 name = "time-core"
-version = "0.1.2"
+version = "0.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef927ca75afb808a4d64dd374f00a2adf8d0fcff8e7b184af886c3c87ec4a3f3"
+checksum = "c9e9a38711f559d9e3ce1cdb06dd7c5b8ea546bc90052da6d06bb76da74bb07c"
 
 [[package]]
 name = "tinystr"
@@ -2801,9 +2839,9 @@ checksum = "1f3ccbac311fea05f86f61904b462b55fb3df8837a366dfc601a0161d0532f20"
 
 [[package]]
 name = "tokio"
-version = "1.43.0"
+version = "1.44.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3d61fa4ffa3de412bfea335c6ecff681de2b609ba3c77ef3e00e521813a9ed9e"
+checksum = "e6b88822cbe49de4185e3a4cbf8321dd487cf5fe0c5c65695fef6346371e9c48"
 dependencies = [
  "backtrace",
  "bytes",
@@ -2851,9 +2889,9 @@ dependencies = [
 
 [[package]]
 name = "tokio-util"
-version = "0.7.13"
+version = "0.7.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d7fcaa8d55a2bdd6b83ace262b016eca0d79ee02818c5c1bcdf0305114081078"
+checksum = "6b9590b93e6fcc1739458317cccd391ad3955e2bde8913edf6f95f9e65a8f034"
 dependencies = [
  "bytes",
  "futures-core",
@@ -3053,6 +3091,12 @@ version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5a5f39404a5da50712a4c1eecf25e90dd62b613502b7e925fd4e4d19b5c96512"
 
+[[package]]
+name = "unicode-segmentation"
+version = "1.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f6ccf251212114b54433ec949fd6a7841275f9ada20dddd2f29e9ceea4501493"
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.6"
@@ -3090,11 +3134,11 @@ checksum = "b6c140620e7ffbb22c2dee59cafe6084a59b5ffc27a8859a5f0d494b5d52b6be"
 
 [[package]]
 name = "uuid"
-version = "1.15.1"
+version = "1.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e0f540e3240398cce6128b64ba83fdbdd86129c16a3aa1a3a252efd66eb3d587"
+checksum = "458f7a779bf54acc9f347480ac654f68407d3aab21269a6e3c9f922acd9e2da9"
 dependencies = [
- "getrandom 0.3.1",
+ "getrandom 0.3.2",
 ]
 
 [[package]]
@@ -3126,9 +3170,9 @@ checksum = "9c8d87e72b64a3b4db28d11ce29237c246188f4f51057d65a7eab63b7987e423"
 
 [[package]]
 name = "wasi"
-version = "0.13.3+wasi-0.2.2"
+version = "0.14.2+wasi-0.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "26816d2e1a4a36a2940b96c5296ce403917633dff8f3440e9b236ed6f6bacad2"
+checksum = "9683f9a5a998d873c0d21fcbe3c083009670149a8fab228644b8bd36b2c48cb3"
 dependencies = [
  "wit-bindgen-rt",
 ]
@@ -3266,7 +3310,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "12342cb4d8e3b046f3d80effd474a7a02447231330ef77d71daa6fbc40681143"
 dependencies = [
  "windows-core",
- "windows-targets",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
@@ -3278,7 +3322,7 @@ dependencies = [
  "windows-implement",
  "windows-interface",
  "windows-result 0.1.2",
- "windows-targets",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
@@ -3303,15 +3347,21 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "windows-link"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76840935b766e1b0a05c0066835fb9ec80071d4c09a16f6bd5f7e655e3c14c38"
+
 [[package]]
 name = "windows-registry"
-version = "0.2.0"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e400001bb720a623c1c69032f8e3e4cf09984deec740f007dd2b03ec864804b0"
+checksum = "4286ad90ddb45071efd1a66dfa43eb02dd0dfbae1545ad6cc3c51cf34d7e8ba3"
 dependencies = [
- "windows-result 0.2.0",
+ "windows-result 0.3.2",
  "windows-strings",
- "windows-targets",
+ "windows-targets 0.53.0",
 ]
 
 [[package]]
@@ -3320,26 +3370,25 @@ version = "0.1.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5e383302e8ec8515204254685643de10811af0ed97ea37210dc26fb0032647f8"
 dependencies = [
- "windows-targets",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
 name = "windows-result"
-version = "0.2.0"
+version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1d1043d8214f791817bab27572aaa8af63732e11bf84aa21a45a78d6c317ae0e"
+checksum = "c64fd11a4fd95df68efcfee5f44a294fe71b8bc6a91993e2791938abcc712252"
 dependencies = [
- "windows-targets",
+ "windows-link",
 ]
 
 [[package]]
 name = "windows-strings"
-version = "0.1.0"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4cd9b125c486025df0eabcb585e62173c6c9eddcec5d117d3b6e8c30e2ee4d10"
+checksum = "87fa48cc5d406560701792be122a10132491cff9d0aeb23583cc2dcafc847319"
 dependencies = [
- "windows-result 0.2.0",
- "windows-targets",
+ "windows-link",
 ]
 
 [[package]]
@@ -3348,7 +3397,7 @@ version = "0.52.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "282be5f36a8ce781fad8c8ae18fa3f9beff57ec1b52cb3de0789201425d9a33d"
 dependencies = [
- "windows-targets",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
@@ -3357,7 +3406,7 @@ version = "0.59.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1e38bc4d79ed67fd075bcc251a1c39b32a1776bbe92e5bef1f0bf1f8c531853b"
 dependencies = [
- "windows-targets",
+ "windows-targets 0.52.6",
 ]
 
 [[package]]
@@ -3366,14 +3415,30 @@ version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9b724f72796e036ab90c1021d4780d4d3d648aca59e491e6b98e725b84e99973"
 dependencies = [
- "windows_aarch64_gnullvm",
- "windows_aarch64_msvc",
- "windows_i686_gnu",
- "windows_i686_gnullvm",
- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_gnullvm",
- "windows_x86_64_msvc",
+ "windows_aarch64_gnullvm 0.52.6",
+ "windows_aarch64_msvc 0.52.6",
+ "windows_i686_gnu 0.52.6",
+ "windows_i686_gnullvm 0.52.6",
+ "windows_i686_msvc 0.52.6",
+ "windows_x86_64_gnu 0.52.6",
+ "windows_x86_64_gnullvm 0.52.6",
+ "windows_x86_64_msvc 0.52.6",
+]
+
+[[package]]
+name = "windows-targets"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b1e4c7e8ceaaf9cb7d7507c974735728ab453b67ef8f18febdd7c11fe59dca8b"
+dependencies = [
+ "windows_aarch64_gnullvm 0.53.0",
+ "windows_aarch64_msvc 0.53.0",
+ "windows_i686_gnu 0.53.0",
+ "windows_i686_gnullvm 0.53.0",
+ "windows_i686_msvc 0.53.0",
+ "windows_x86_64_gnu 0.53.0",
+ "windows_x86_64_gnullvm 0.53.0",
+ "windows_x86_64_msvc 0.53.0",
 ]
 
 [[package]]
@@ -3382,53 +3447,101 @@ version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "32a4622180e7a0ec044bb555404c800bc9fd9ec262ec147edd5989ccd0c02cd3"
 
+[[package]]
+name = "windows_aarch64_gnullvm"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "86b8d5f90ddd19cb4a147a5fa63ca848db3df085e25fee3cc10b39b6eebae764"
+
 [[package]]
 name = "windows_aarch64_msvc"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "09ec2a7bb152e2252b53fa7803150007879548bc709c039df7627cabbd05d469"
 
+[[package]]
+name = "windows_aarch64_msvc"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c7651a1f62a11b8cbd5e0d42526e55f2c99886c77e007179efff86c2b137e66c"
+
 [[package]]
 name = "windows_i686_gnu"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8e9b5ad5ab802e97eb8e295ac6720e509ee4c243f69d781394014ebfe8bbfa0b"
 
+[[package]]
+name = "windows_i686_gnu"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c1dc67659d35f387f5f6c479dc4e28f1d4bb90ddd1a5d3da2e5d97b42d6272c3"
+
 [[package]]
 name = "windows_i686_gnullvm"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0eee52d38c090b3caa76c563b86c3a4bd71ef1a819287c19d586d7334ae8ed66"
 
+[[package]]
+name = "windows_i686_gnullvm"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ce6ccbdedbf6d6354471319e781c0dfef054c81fbc7cf83f338a4296c0cae11"
+
 [[package]]
 name = "windows_i686_msvc"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "240948bc05c5e7c6dabba28bf89d89ffce3e303022809e73deaefe4f6ec56c66"
 
+[[package]]
+name = "windows_i686_msvc"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "581fee95406bb13382d2f65cd4a908ca7b1e4c2f1917f143ba16efe98a589b5d"
+
 [[package]]
 name = "windows_x86_64_gnu"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "147a5c80aabfbf0c7d901cb5895d1de30ef2907eb21fbbab29ca94c5b08b1a78"
 
+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e55b5ac9ea33f2fc1716d1742db15574fd6fc8dadc51caab1c16a3d3b4190ba"
+
 [[package]]
 name = "windows_x86_64_gnullvm"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "24d5b23dc417412679681396f2b49f3de8c1473deb516bd34410872eff51ed0d"
 
+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0a6e035dd0599267ce1ee132e51c27dd29437f63325753051e71dd9e42406c57"
+
 [[package]]
 name = "windows_x86_64_msvc"
 version = "0.52.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "589f6da84c646204747d1270a2a5661ea66ed1cced2631d546fdfb155959f9ec"
 
+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.53.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "271414315aff87387382ec3d271b52d7ae78726f5d44ac98b4f4030c91880486"
+
 [[package]]
 name = "wit-bindgen-rt"
-version = "0.33.0"
+version = "0.39.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3268f3d866458b787f390cf61f4bbb563b922d091359f9608842999eaee3943c"
+checksum = "6f42320e61fe2cfd34354ecb597f86f413484a798ba44a8ca1165c58d42da6c1"
 dependencies = [
  "bitflags",
 ]
@@ -3447,15 +3560,23 @@ checksum = "1e9df38ee2d2c3c5948ea468a8406ff0db0b29ae1ffde1bcf20ef305bcc95c51"
 
 [[package]]
 name = "xattr"
-version = "1.4.0"
+version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e105d177a3871454f754b33bb0ee637ecaaac997446375fd3e5d43a2ed00c909"
+checksum = "0d65cbf2f12c15564212d48f4e3dfb87923d25d611f2aed18f4cb23f0413d89e"
 dependencies = [
  "libc",
- "linux-raw-sys",
  "rustix",
 ]
 
+[[package]]
+name = "xz2"
+version = "0.1.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "388c44dc09d76f1536602ead6d325eb532f5c122f17782bd57fb47baeeb767e2"
+dependencies = [
+ "lzma-sys",
+]
+
 [[package]]
 name = "yoke"
 version = "0.7.5"
@@ -3482,39 +3603,18 @@ dependencies = [
 
 [[package]]
 name = "zerocopy"
-version = "0.7.35"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1b9b4fd18abc82b8136838da5d50bae7bdea537c574d8dc1a34ed098d6c166f0"
-dependencies = [
- "byteorder",
- "zerocopy-derive 0.7.35",
-]
-
-[[package]]
-name = "zerocopy"
-version = "0.8.21"
+version = "0.8.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcf01143b2dd5d134f11f545cf9f1431b13b749695cb33bcce051e7568f99478"
+checksum = "2586fea28e186957ef732a5f8b3be2da217d65c5969d4b1e17f973ebbe876879"
 dependencies = [
- "zerocopy-derive 0.8.21",
+ "zerocopy-derive",
 ]
 
 [[package]]
 name = "zerocopy-derive"
-version = "0.7.35"
+version = "0.8.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa4f8080344d4671fb4e831a13ad1e68092748387dfc4f55e356242fae12ce3e"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn",
-]
-
-[[package]]
-name = "zerocopy-derive"
-version = "0.8.21"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "712c8386f4f4299382c9abee219bee7084f78fb939d88b6840fcc1320d5f6da2"
+checksum = "a996a8f63c5c4448cd959ac1bab0aaa3306ccfd060472f85943ee0750f0169be"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -3586,9 +3686,9 @@ dependencies = [
 
 [[package]]
 name = "zip"
-version = "2.2.3"
+version = "2.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b280484c454e74e5fff658bbf7df8fdbe7a07c6b2de4a53def232c15ef138f3a"
+checksum = "1dcb24d0152526ae49b9b96c1dcf71850ca1e0b882e4e28ed898a93c41334744"
 dependencies = [
  "aes",
  "arbitrary",
@@ -3597,17 +3697,16 @@ dependencies = [
  "crc32fast",
  "crossbeam-utils",
  "deflate64",
- "displaydoc",
  "flate2",
+ "getrandom 0.3.2",
  "hmac",
- "indexmap 2.7.1",
+ "indexmap 2.9.0",
  "lzma-rs",
  "memchr",
  "pbkdf2",
- "rand 0.8.5",
  "sha1",
- "thiserror 2.0.12",
  "time",
+ "xz2",
  "zeroize",
  "zopfli",
  "zstd",
@@ -3638,18 +3737,18 @@ dependencies = [
 
 [[package]]
 name = "zstd-safe"
-version = "7.2.3"
+version = "7.2.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f3051792fbdc2e1e143244dc28c60f73d8470e93f3f9cbd0ead44da5ed802722"
+checksum = "8f49c4d5f0abb602a93fb8736af2a4f4dd9512e36f7f570d66e65ff867ed3b9d"
 dependencies = [
  "zstd-sys",
 ]
 
 [[package]]
 name = "zstd-sys"
-version = "2.0.14+zstd.1.5.7"
+version = "2.0.15+zstd.1.5.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8fb060d4926e4ac3a3ad15d864e99ceb5f343c6b34f5bd6d81ae6ed417311be5"
+checksum = "eb81183ddd97d0c74cedf1d50d85c8d08c1b8b68ee863bdee9e706eedba1a237"
 dependencies = [
  "cc",
  "pkg-config",
diff --git a/packages/core-bridge/Cargo.toml b/packages/core-bridge/Cargo.toml
index 83aac77c5..1161774f6 100644
--- a/packages/core-bridge/Cargo.toml
+++ b/packages/core-bridge/Cargo.toml
@@ -1,9 +1,12 @@
 [package]
 name = "temporal-sdk-typescript-bridge"
 version = "0.1.0"
-authors = ["Roey Berman <roey@temporal.io>"]
+authors = ["Temporal Technologies Inc. <sdk@temporal.io>"]
 license = "MIT"
 edition = "2024"
+repository = "https://github.com/temporalio/sdk-typescript"
+description = "Core Bridge for the TypeScript Temporal SDK"
+publish = false
 exclude = ["index.node", "sdk-core"]
 
 [lib]
@@ -17,17 +20,20 @@ lto = true
 incremental = false
 
 [dependencies]
+anyhow = "1.0"
 async-trait = "0.1.83"
+bridge-macros = { path = "bridge-macros" }
 futures = { version = "0.3", features = ["executor"] }
 log = "0.4"
 neon = { version = "1.0.0", default-features = false, features = ["napi-6", "futures"] }
-opentelemetry = "0.24"
+opentelemetry = "0.26"
 parking_lot = "0.12"
 prost = "0.13"
 prost-types = "0.13"
+serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
-tokio = "1.13"
-once_cell = "1.19"
 temporal-sdk-core = { version = "*", path = "./sdk-core/core", features = ["ephemeral-server"] }
 temporal-client = { version = "*", path = "./sdk-core/client" }
+thiserror = "2"
+tokio = "1.13"
 tokio-stream = "0.1"
diff --git a/packages/core-bridge/README.md b/packages/core-bridge/README.md
index ae0d9f6ad..e271ae62c 100644
--- a/packages/core-bridge/README.md
+++ b/packages/core-bridge/README.md
@@ -2,4 +2,9 @@
 
 [![NPM](https://img.shields.io/npm/v/@temporalio/core-bridge?style=for-the-badge)](https://www.npmjs.com/package/@temporalio/core-bridge)
 
+
 Part of [Temporal](https://temporal.io)'s [TypeScript SDK](https://docs.temporal.io/typescript/introduction/).
+
+> [!CAUTION] **Important**: This package is not intended to be used directly. Any API
+             provided by this package is internal and subject to change without notice.
+
diff --git a/packages/core-bridge/ai-rules.md b/packages/core-bridge/ai-rules.md
new file mode 100644
index 000000000..fa8a2be0b
--- /dev/null
+++ b/packages/core-bridge/ai-rules.md
@@ -0,0 +1,418 @@
+# Bridge Layer Coding Norms, Best Practices and Pertinent Knowledge
+
+This document captures the coding norms, best practices and key knowledge required to efficiently
+contribute to development of the Rust ↔ TypeScript bridge layer of the Temporal TypeScript SDK.
+This document is meant to guide both human developers and AI tools in maintaining consistency
+and quality of the bridge layer.
+
+## 1. Bridge Layer Design Philosophy
+
+- **The bridge should be easy to maintain and review** — The bridge's code should clearly
+  expose it's actual business logic and types, notably by applying mechanical and systematic
+  coding patterns that are easy to understand and verify.
+
+  - The bridge layer is a fragile interface, as it breaks continuity of type safety guarantees
+    that TypeScript and Rust provide at other levels. The risk of bugs caused by inconsistencies
+    between the TS and Rust API definitions is real — we have in fact identified several such
+    bugs in the past — and we are are highly reliant on developer's and reviewer's thorough
+    scrutinity to catch those inconsistencies.
+
+  - By keeping the bridge's code thin and foccussed, we can significantly improve the
+    reviewability of API definitions between the TS and Rust sides, and therefore reduce
+    the risks of such incoherencies.
+
+  - Care must notably be exercised to avoid drowning the bridge's main logic with JS/Rust
+    object manipulations, tasks scheduling, and other plumbing concerns that add unreasonable
+    complexity, hinder evolution and reviewability, and make it hard for new SDK developers
+    to approach that codebase.
+
+  - Complexity should be moved out of the bridge business logic, preferably to TypeScript
+    user-facing packages or to the Core SDK project. Where complexity is unavoidable, it should
+    be structured in a way that preserves reviewability of the bridge's business logic and
+    types, for example by extracting it to appropriate abstractions and helpers (i.e. like
+    we did with type conversions, errors, Futures, Callbacks, etc).
+
+  - Though not always possible, we should generally strive to align the TS SDK's bridge's logic
+    with that of other official Temporal SDK bridges, as this makes it easier for our engineers
+    to do cross-SDKs maintenance and development.
+
+    - https://github.com/temporalio/sdk-python
+    - https://github.com/temporalio/sdk-dotnet
+    - https://github.com/temporalio/sdk-ruby
+
+- **Bridge APIs are internal** — The bridge itself is an implementation detail and not meant to
+  be used directly. SDK features and APIs are exposed to users exclusively through the user-facing
+  packages: `@temporalio/worker`, `@temporalio/testing` and `@temporalio/common`.
+
+  - The bridge provides absolutely no API stability guarantee, not even across patch-level
+    releases. It is therefore required that the bridge and all public-facing packages be the
+    same version number (i.e. combining SDK packages of different version is not supported).
+
+  - All functions and types exposed by the TypeScript `core-bridge` package are internal.
+    These should never be imported from user code, nor should they be reexported by our
+    own user-facing packages.
+
+- **Objects transferred through the bridge are DTO** — The bridge must define internal
+  types specifically for the TS/Rust interface, independentely of user-facing APIs defined
+  by user-facing packages. These internal types follow the key principles of the well-known
+  Data Transfer Object pattern.
+
+  - As a general rule, bridge transfer types should mirror the corresponding Core SDK types
+    except when doing so would be impractical. Alignment with user-facing types is not an
+    objective. More over, transfer types must adhere to some particular constraints that
+    will be described later in this document.
+
+  - Bridge should only perform the minimal type validations that are strictly required as part
+    of its type conversion and business logic. More comprehensive validations and transformations,
+    including filling-in default values, preserving backward compatibility, converting from
+    user-friendly types and more, belong to user-facing packages.
+
+- **The bridge should be reliable** — As a critical component of the Temporal SDK, the bridge
+  should be highly reliable, notably regarding object lifecycle management, memory usage, and
+  concurrency challenges. Runtime performance should also not be neglected, though this is
+  arguably less of a concern at the bridge level compared to other parts of the SDK.
+
+## 2. Project Structure and Code Organization
+
+- **Module Organization**:
+
+  - On the Rust side, bridge API functions and types are defined in files under
+    the `core-bridge/src` directory. Each major component has its own file
+    (`client.rs`, `worker.rs`, etc).
+
+  - Configuration-related types for each major component are grouped in a nested
+    `config` submodule inside that component's file.
+
+  - Rust side helper functionalities are designed as proper abstractions inside the
+    `helpers` module. Some abstractions are also provided through Derive Macros,
+    defined in the `bridge-macros` crate.
+
+  - On the TS side, bridge APIs (including functions and types) are declared in
+    the `core-bridge/ts/native.ts` file.
+
+  **Bridge API Functions**:
+
+  - Component-specific prefix for API entrypoint functions (e.g., `client_new`,
+    `worker_poll_activity_task`, etc).
+
+  - Functions name are snake-case on the Rust side, but camel-case on the TS side.
+
+- **Bridge API Types**:
+
+  - On the Rust side, bridge types are defined in their respective component files
+    (e.g. client.rs, worker.rs, etc); configuration-related types are contained
+    inside the `config` submodule of the component file.
+
+  - On the TypeScript side, most types are defined in the `native.ts` file,
+    collocated with API functions declarations of the same component.
+
+- **Declaration order**:
+
+  - As a general rule, functions, types and properties of types should have the
+    same names in Rust and TypeScript (save for camel-case/snake-case equivalence
+    where appropriate), and should be listed in the same order. This makes review
+    significantly easier by allowing quick side-to-side comparison.
+
+## 3. Type System
+
+- **Type Conversion System**:
+
+  - The bridge provides a type-safe conversion system between Rust and TypeScript
+    through two main traits:
+
+    - `TryFromJs` for JavaScript to Rust conversions
+    - `TryIntoJs` for Rust to JavaScript conversions
+
+  - These traits are implemented for primitive types, and can be derived for most struct and enums
+    through the `#[derive(TryFromJs)]` and `#[derive(TryIntoJs)]` macros. Custom implementations
+    are also possible to handle special cases.
+
+- **Option Handling**:
+
+  - The bridge uses the TypeScript value `null` (rather than `undefined`) to represent the `None`
+    case of a value defined as `Option<T>` on objects that are sent through the bridge; the
+    TypeScript mapped type `Option<T> = T | null` can be used to model such value.
+
+  - All expected properties must be present and set to a non-`undefined` value on objects
+    that are sent across the bridge; that notably means that properties on bridge types
+    should never be declared with the `?` operator in TypeScript (e.g. there should be no
+    property declared as `someProperty?: number`).
+
+  - This design allows differentiation between "intentionally unspecified" values (`null`, meaning
+    `None`) and "unintentionally missing" properties (`undefined`), which in turn allows early
+    detection of some frequent incoherency patterns between type definition in JS and Rust.
+
+  - Key rules:
+    - Always use `null` for intentionally unspecified optional values
+    - Never use TypeScript's optional property syntax (`prop?: T`)
+    - Explicitly set all properties when sending objects to native code
+
+- **`TryFromJs` and `TryIntoJs` derive macros**
+
+  - When applied to a Rust enum type, the derive macros expects the corresponding JS type
+    definition to contain a discriminator property named `type`, whose value must match the
+    name of the desired enum variant in kebab-case. Other fields of the variant are read from the
+    same JS object (a.k.a. "Internally tagged" in `serde`'s terminology). If an enum variant
+    accepts a tupple composed of a single field, then that field is de/serialized from/into the
+    object containing the `type` property. Refer to type `LogExporter` or `EphemeralServerConfig`
+    for usage examples of these macros with enum types.
+
+  - Note that the `TryFromJs` and `TryIntoJs` derive macros are designed to handle most of the
+    patterns seen commonly in this code base; they are however far from being comprehensive. For
+    more complex use cases, it is generally preferable to implement the desired trait manually.
+
+- **JavaScript Function Exports**:
+
+  - The bridge uses the `#[js_function]` derive macro to simplify the implementation of functions
+    that are exported to JavaScript through Neon. This macro handles all the boilerplate required
+    to safely convert JS arguments to Rust types and return values back to JavaScript.
+
+  - A function decorated with `#[js_function]` must:
+
+    - Accept only arguments that implements the `TryFromJs` trait;
+    - Return a `BridgeResult<T>`, where T implements the `TryIntoJs` trait.
+
+  - The macro actually expands into two functions:
+
+    - The actual JS-facing function, with the original name, which handles JS argument extraction
+      and conversion (i.e. using the `TryFromJs` trait to convert each argument to the specified
+      type), as well as result conversion back to JS (i.e. using the `TryIntoJs` trait for the
+      specified target type). It also ensures outbound conversion of `BridgeError` into Neon's
+      `Throw` type (by using the `IntoThrow` trait).
+
+    - An implementation function with an `_impl` suffix that contains the original function body
+      and operates entirely on Rust types.
+
+  - All functions meant to be called from JavaScript should be marked with this macro. The
+    functions must also be registered on the Neon's `ModuleContext`, using the pattern seen
+    in each component's `init` function:
+
+    ```rust
+    fn init(cx: &mut neon::prelude::ModuleContext) -> neon::prelude::NeonResult<()> {
+        cx.export_function("functionName", function_name)?;
+        // More exports...
+        Ok(())
+    }
+    ```
+
+  - Each component's `init` functions are called by Neon's bootstrap code, on initialization
+    of the native module. See `core-bridge/src/lib.rs`.
+
+- **Common Type Mappings**:
+
+  The bridge supports the following type conversions between TypeScript and Rust:
+
+  **TypeScript → Rust** (using `TryFromJs` trait):
+
+  | TypeScript Type                             | Rust Type                                                   |
+  | ------------------------------------------- | ----------------------------------------------------------- | --- |
+  | `number`                                    | `u16`, `i32`, `f32`, `u64`, `f64`, `usize`                  | x   |
+  | `number`                                    | `Duration` (from ms as `u64`)                               | x   |
+  | `string`                                    | `String`                                                    | x   |
+  | `boolean`                                   | `bool`                                                      | x   |
+  | `T[]` or `Array<T>`                         | `Vec<T>`                                                    | x   |
+  | `Record<string, T>` or `{[key: string]: T}` | `HashMap<String, T>`                                        | x   |
+  | `string`                                    | `SocketAddr`                                                | x   |
+  | `string`                                    | `Url`                                                       | x   |
+  | `T \| null`                                 | `Option<T>`                                                 | x   |
+  | `Buffer`                                    | `Vec<u8>`                                                   | x   |
+  | `unknwon`                                   | `()` (empty tuple)                                          | x   |
+  | `[T1, T2, ...]` - to be confirmed           | `(T1, T2, ...)` (tuple)                                     |
+  | Function<Result, Args> - to be reworked     | `JsCallback<Args, Result>`, `JsAsyncCallback<Args, Result>` |
+  | `OpaqueHandle<T>` - to be reworked          | `OpaqueInboundHandle<T>`                                    |
+
+  **Rust → TypeScript** (using `TryIntoJs` trait):
+
+  | Rust Type                                  | TypeScript Type            |
+  | ------------------------------------------ | -------------------------- | --- |
+  | `String`                                   | `string`                   | x   |
+  | `bool`                                     | `boolean`                  | x   |
+  | `Vec<T>`                                   | `T[]`                      | x   |
+  | `SystemTime`                               | `bigint` (as nano seconds) | x   |
+  | `()` (unit tuple)                          | `undefined`                | x   |
+  | `(T1, T2, ...)` (tuple) - to be confirmed  | `[T1, T2, ...]`            |
+  | `Option<T>`                                | `T \| null`                | x   |
+  | `Vec<u8>`                                  | `Buffer`                   | x   |
+  | `HashMap<String, T>` - to be confirmed     | `Record<string, T>`        |
+  | `BridgeFuture<T>` - to be reworked         | `Promise<T>`               |
+  | `OpaqueOutboundHandle<T>` - to be reworked | `OpaqueHandle<T>`          |
+
+  These mappings form the foundation of the interoperability between TypeScript and Rust in the bridge.
+
+  For more complex cases, manual implementations of the `TryFromJs` and `TryIntoJs` traits may be needed.
+
+## 4. Error Handling
+
+- **Error Types and Results**:
+
+  - The bridge defines the `BridgeError` enum, as well as an associated `BridgeResult<T>` type
+    alias, which are the prefered types to report and propagate errors in the bridge layer.
+    The `BridgeError` enum notably provides the following advantages:
+
+    - They can transparently encapsulate an already "thrown" `Throw` object, thus allowing
+      propagation through intermediate function calls that are not JS `Context` aware,
+      then rethrow the `Throw` when appropriate.
+
+    - They can be emitted from a non-`Context`-aware function, and may even be sent across
+      threads to be finally converted to a `Throw` object if/once propagation reaches a
+      `Context` aware parent. The JS Error type is automatically determined based on the
+      variant of the `BridgeError`, including the possibility of sending some bridge specific
+      error types (see Custom JS Error Classes below).
+
+    - They allow enrichment of errors with contextual informations that are provided while
+      propagating the error up through the call stack, either through `anyhow`'s `.context(...)`
+      method, or the `BridgeError`'s specific `.field(...) method.
+
+  - Functions that return a `JsResult` or `NeonResult` (which implies they have access to
+    a live `Context`), such as implementations of the `TryIntoJs` and `js_function` traits,
+    are responsible for converting back `BridgeResult` into `Throw`, e.g. by calling
+    `BridgeResult::into_throw(result, cx)?`.
+
+  - Note that Neon's `Throw` objects can't be `Send`, _not even when wrapped in a `BridgeError`_
+    (there is anyway rarely use cases that would implies such thing). With very few exceptions
+    (noted in Neon's typedocs), once a `Throw` object has been created, the Node's thread is in
+    a "throwing" state, and any further call to any `Context` object will cause a panic; the
+    "throwing" state remains until the `Throw` object is finally propagated back to the JS caller.
+
+- **Error Context**:
+
+  - Always use the `.field()` method on `BridgeResult` to add context to errors when accessing
+    object properties on JS objects; each call to `field()` _prepends_ a path component, resulting
+    in a complete path to problematic value once the error has propagated all the way up
+    (e.g. `fn some_func.args[4].foo.bar: ...`). Note that the `TryFromJs` and `js_function`
+    derive macros, and most existing helpers already add field context; extra work is only
+    required when manually implementing the `TryFromJs` trait or when reaching for helpers
+    that do not add context.
+
+  - Always use the `.context()` method on `BridgeResult` to add context to errors that are
+    automatically converted from foreing errors or `BridgeResult` that are propagated up
+    through the caller stack, unless the error itself already provides sufficient context.
+
+- **Custom JS Error Classes**:
+
+  - The Neon's API provide built-in support for the following standard JS errors: `Error`,
+    `TypeError` and `RangeError`. The bridge also add support for the following custom JS
+    errors: `IllegalStateError`, `UnexpectedError`, `TransportError` and `ShutdownError`.
+
+  - Custom JS error classes are defined in `core-bridge/ts/errors.ts` file (for the TS class
+    definition and name-to-class conversion) and in `core-bridge/src/helpers/errors.rs` (for
+    the Rust counterpart). Both of these files must be be kept in sync.
+
+  - Note that the Rust code do not actually instantiate the proper JS classes, as those are
+    not accessible from the native code (i.e. they are not exposed as globals or on any object
+    currently accessible to the native bridge). Instead, the Rust code create instances of the
+    `Error` class, then simply override the `name` property of the error object. Those error
+    objects are then replaced instances of the appropriate Error classes by a pure-JS wrapper
+    that is added on load of the native library (see `core-bridge/index.js`).
+
+## FIXME: Anything below this point is incomplete / not reviewed
+
+## 5. Asynchronous Operations and Thread Safety
+
+- **Future and Promise Handling**:
+
+  - Consistent use of `future_to_promise()` to convert Rust futures to JS promises
+  - Extension trait `RuntimeExt` to simplify working with futures
+  - Clear distinction between sync and async functions
+  - Proper typing of Promise results
+  - Careful handling of async error propagation
+
+- **Thread Safety**:
+
+  - Strict separation between JS and Rust threads
+  - Careful handling of JS contexts to avoid using them across threads
+  - Use of the `enter_sync!` macro when entering tokio context
+  - Proper synchronization of shared resources
+  - Use of `Arc` and `Mutex` for thread-safe data sharing
+  - Clear documentation of thread safety requirements
+
+- **Concurrency Patterns**:
+  - Consistent patterns for handling concurrent operations
+  - Clear documentation of thread safety guarantees
+  - Proper handling of cancellation and timeouts
+  - Careful management of async resources
+
+## 6. Resource and Handle Management
+
+- **Handle Types**:
+
+  - Use of `OpaqueInboundHandle<T>` and `OpaqueOutboundHandle<T>` to safely pass Rust objects to/from JS
+  - TypeScript interfaces for handles with type discriminators
+  - Consistent patterns for borrowing (`borrow_inner()`) and taking ownership (`take_inner()`)
+  - Implementation of `Finalize` trait for proper cleanup
+
+- **Resource Lifecycle**:
+
+  - Clear patterns for resource creation and destruction
+  - Proper cleanup in error cases
+  - Thread-safe resource management
+  - Documentation of resource ownership and lifetime
+
+- **Memory Management**:
+  - Careful management of object lifecycles
+  - Proper cleanup of resources in error cases
+  - Efficient memory usage patterns
+  - Clear documentation of memory management requirements
+
+## 7. Code Style and Naming Conventions
+
+- **Rust Code Style**:
+
+  - Use of `/////` line separators to visually divide sections of code
+  - Standard library imports first, external crate imports next, internal imports last
+  - Organized by category with blank lines between groups
+  - Consistent parameter ordering (handles first, then configuration)
+  - Clear module organization and file structure
+
+- **TypeScript Code Style**:
+
+  - Consistent use of TypeScript features
+  - Clear type definitions and interfaces
+  - Proper use of type aliases and enums
+  - Consistent file organization
+
+- **Naming Conventions**:
+  - PascalCase for types (`BridgeWorkerOptions`, `EphemeralServer`)
+  - snake_case for Rust functions and variables
+  - camelCase for TypeScript functions and variables
+  - Consistent naming patterns (`Core` prefix for sdk-core types)
+  - Clear and descriptive names for all identifiers
+
+## 8. Documentation, Testing, and Review
+
+- **Code Documentation**:
+
+  - Doc comments on public functions and types
+  - Clear explanations of complex patterns
+  - Comments for non-obvious code sections
+  - Use of `// FIXME: ...` comments for issues that need attention
+  - Examples of proper usage
+
+- **Testing Guidelines**:
+
+  - Unit tests for all bridge functions
+  - Integration tests for complex interactions
+  - Tests for error cases and edge conditions
+  - Performance tests for critical paths
+  - Clear test organization and naming
+
+- **Review Guidelines**:
+  - Function names must match exactly (camelCase in TypeScript, snake_case in Rust)
+  - Parameter order must be identical on both sides
+  - Field names must match exactly (camelCase in TypeScript, snake_case in Rust)
+  - Field order should match to make review easier
+  - Nested structures must maintain the same hierarchy
+  - Comments and documentation should be consistent
+  - Type definitions should be in the same order for easy review
+  - Thread safety considerations must be documented
+  - Resource cleanup must be verified
+
+============
+
+Extra notes:
+
+- It is not immediately obvious that implementing Neon's `Finalize` for our types provides
+  any real advantage over implementing `Drop` (or just doing nothing!). Finalize provides a
+  `Context` and therefore execute on Node's thread, which could be pertinent for some operations,
+  but doesn't seem fit our use cases. Implementing `Drop` should be sufficient in most cases,
+  and may feel more natural to Rust developers.
diff --git a/packages/core-bridge/bridge-macros/Cargo.toml b/packages/core-bridge/bridge-macros/Cargo.toml
new file mode 100644
index 000000000..795195223
--- /dev/null
+++ b/packages/core-bridge/bridge-macros/Cargo.toml
@@ -0,0 +1,16 @@
+[package]
+name = "bridge-macros"
+version = "0.1.0"
+edition = "2024"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = { version = "2.0", features = ["full", "extra-traits"] }
+quote = "1.0"
+proc-macro2 = "1.0"
+convert_case = "0.6"
+
+[dev-dependencies]
+temporal-sdk-typescript-bridge = { path = ".." }
diff --git a/packages/core-bridge/bridge-macros/src/derive_js_function.rs b/packages/core-bridge/bridge-macros/src/derive_js_function.rs
new file mode 100644
index 000000000..ba9a007ba
--- /dev/null
+++ b/packages/core-bridge/bridge-macros/src/derive_js_function.rs
@@ -0,0 +1,126 @@
+use quote::format_ident;
+use quote::quote;
+use syn::GenericArgument;
+use syn::Pat;
+use syn::PathArguments;
+use syn::Type;
+use syn::{FnArg, ItemFn, PatType, ReturnType, parse_macro_input};
+
+pub fn js_function_impl(
+    _attr: proc_macro::TokenStream,
+    item: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    let input = parse_macro_input!(item as ItemFn);
+
+    let vis = &input.vis;
+    let fn_name = &input.sig.ident;
+    let generics = &input.sig.generics; // Is this still pertinent?
+    let args = &input.sig.inputs;
+    let return_type = &input.sig.output; // Can we avoid in some cases?
+    let fn_block = &input.block;
+
+    let fn_impl_name = format_ident!("{}_impl", fn_name);
+
+    // Extract function arguments
+    let args = args
+        .iter()
+        .filter_map(|arg| {
+            if let FnArg::Typed(PatType { pat, ty, .. }) = arg {
+                if let Pat::Ident(pat_ident) = &**pat {
+                    Some((pat_ident.ident.clone(), (*ty).clone()))
+                } else {
+                    None
+                }
+            } else {
+                None
+            }
+        })
+        .collect::<Vec<_>>();
+
+    // Extract return type
+    let (result_return_type, inner_return_type) = match return_type {
+        ReturnType::Type(_, ty) => match extract_bridge_result_type(ty) {
+            Some(inner_type) => (ty, inner_type),
+            None => panic!("Return type must be a BridgeResult"),
+        },
+        ReturnType::Default => panic!("Return type must be a BridgeResult"),
+    };
+
+    // Generate argument conversions
+    let arg_conversions = args.iter().enumerate().map(|(i, (name, ty))| {
+        quote! {
+            use crate::helpers::*;
+            let #name = cx.argument_into::<#ty>(#i).field(format!("fn {}", stringify!(#fn_name)).as_str()).into_throw(&mut cx)?;
+        }
+    });
+
+    // Generate implementation function arguments
+    let impl_args = args.iter().map(|(name, ty)| {
+        quote! { #name: #ty }
+    });
+
+    // Generate argument names for impl function call
+    let arg_names = args.iter().map(|(name, _)| quote! { #name });
+
+    let expanded = if args.is_empty() {
+        // No arguments case
+        quote! {
+            // Bridge function
+            #[allow(clippy::significant_drop_tightening, clippy::unnecessary_wraps)]
+            #vis fn #fn_name #generics(
+                mut cx: FunctionContext #generics
+            ) -> JsResult<<#inner_return_type as crate::helpers::TryIntoJs>::Output> {
+                let result = #fn_impl_name().into_throw(&mut cx)?;
+                result.try_into_js(&mut cx)
+            }
+
+            // Implementation function
+            #[allow(clippy::unnecessary_wraps)]
+            #vis fn #fn_impl_name #generics() -> #result_return_type {
+                #fn_block
+            }
+        }
+    } else {
+        // With arguments case
+        quote! {
+            // Bridge function
+            #[allow(clippy::significant_drop_tightening, clippy::unnecessary_wraps)]
+            #vis fn #fn_name #generics(
+                mut cx: FunctionContext #generics
+            ) -> JsResult<<#inner_return_type as crate::helpers::TryIntoJs>::Output> {
+                #(#arg_conversions)*
+
+                let result = #fn_impl_name(#(#arg_names),*).into_throw(&mut cx)?;
+                result.try_into_js(&mut cx)
+            }
+
+            // Implementation function
+            #[allow(clippy::unnecessary_wraps)]
+            #vis fn #fn_impl_name #generics(#(#impl_args),*) -> #result_return_type {
+                #fn_block
+            }
+        }
+    };
+
+    // Uncomment this line to print the expanded macro
+    // eprintln!("=== fn {} ===\n{}\n======", fn_name.to_string(), expanded);
+
+    proc_macro::TokenStream::from(expanded)
+}
+
+fn extract_bridge_result_type(ty: &Type) -> Option<&Type> {
+    if let Type::Path(type_path) = ty {
+        if let Some(last_segment) = type_path.path.segments.last() {
+            // Check if it's BridgeResult
+            if last_segment.ident == "BridgeResult" {
+                // Extract the type parameter T from BridgeResult<T>
+                if let PathArguments::AngleBracketed(generic_args) = &last_segment.arguments {
+                    if let Some(GenericArgument::Type(inner_type)) = generic_args.args.first() {
+                        return Some(inner_type);
+                    }
+                }
+            }
+        }
+    }
+    None
+}
diff --git a/packages/core-bridge/bridge-macros/src/derive_tryfromjs.rs b/packages/core-bridge/bridge-macros/src/derive_tryfromjs.rs
new file mode 100644
index 000000000..6f0103c74
--- /dev/null
+++ b/packages/core-bridge/bridge-macros/src/derive_tryfromjs.rs
@@ -0,0 +1,152 @@
+use convert_case::{Case, Casing};
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{DeriveInput, FieldsNamed, FieldsUnnamed};
+
+pub fn derive_tryfromjs_struct(input: &DeriveInput, data: &syn::DataStruct) -> TokenStream {
+    let struct_ident = &input.ident;
+    let generics = &input.generics;
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    let field_conversions = if let syn::Fields::Named(ref fields) = data.fields {
+        field_conversions_for_named_fields(fields)
+    } else {
+        panic!("Only named fields are supported")
+    };
+
+    let expanded = quote! {
+        impl #impl_generics crate::helpers::TryFromJs for #struct_ident #ty_generics #where_clause {
+            fn try_from_js<'cx, 'b>(cx: &mut impl neon::prelude::Context<'cx>, js_value: neon::prelude::Handle<'b, neon::prelude::JsValue>) -> crate::helpers::BridgeResult<Self> {
+                use crate::helpers::*;
+
+                let obj = js_value.downcast::<neon::prelude::JsObject, _>(cx)?;
+                Ok(Self {
+                    #(#field_conversions),*
+                })
+            }
+        }
+    };
+
+    // Uncomment this line to print the expanded macro
+    // eprintln!(
+    //     "=== struct {} ===\n{}\n======",
+    //     struct_ident.to_string(),
+    //     expanded
+    // );
+
+    TokenStream::from(expanded)
+}
+
+pub fn derive_tryfromjs_enum(input: &DeriveInput, data: &syn::DataEnum) -> TokenStream {
+    let enum_ident = &input.ident;
+    let enum_name = enum_ident.to_string();
+    let variants = &data.variants;
+    let generics = &input.generics;
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    let variant_conversions = variants.iter().map(|v| {
+        let variant_ident = &v.ident;
+        let discriminant = variant_ident.to_string().to_case(Case::Kebab);
+        let js_discriminant = variant_ident.to_string().to_case(Case::Camel);
+
+        match &v.fields {
+            syn::Fields::Unit => {
+                // e.g. "otel" => Ok(MetricsExporter::Otel)
+                quote! {
+                    #discriminant => Ok(#enum_ident::#variant_ident),
+                }
+            }
+            syn::Fields::Unnamed(FieldsUnnamed { unnamed, .. }) => {
+                if unnamed.len() != 1 {
+                    panic!("Enum variant must have a single unnamed field that implements the TryFromJs trait");
+                }
+                let ty = unnamed.first().map(|f| f.ty.clone()).unwrap();
+                match ty {
+                    syn::Type::Path(path) => {
+                        // Example output:
+                        //
+                        // "otel" => {
+                        //    <OtelConfig>::try_from_js(cx, js_value).field("otel").map(MetricsExporter::Otel)
+                        // }
+                        quote! {
+                            #discriminant => {
+                                <#path>::try_from_js(cx, js_value).field(&#js_discriminant).map(#enum_ident::#variant_ident)
+                            },
+                        }
+                    },
+                    _ => panic!("Enum variant must have a single unnamed field that implements the TryFromJs trait"),
+                }
+            }
+            syn::Fields::Named(fields) => {
+                // Example output:
+                //
+                //   "console" => Ok((|| {
+                //       Ok::<LogExporter, BridgeError>(LogExporter::Console {
+                //           filter: { obj.get_property_into(cx, "filter")? },
+                //       })
+                //   })()
+                //   .field(format!("type={}", type_str).as_str())?),
+                //
+                // The inner closure is required so that we can use the `field` method on the result.
+                // An alternative would be to do that at the field level, but then that concern would
+                // spill into the field_conversions_for_named_fields function, which is used in
+                // other places.
+                let field_conversions = field_conversions_for_named_fields(fields);
+                quote! {
+                    #discriminant => Ok(( || {
+                        Ok::<#enum_ident #ty_generics, crate::helpers::BridgeError>(#enum_ident::#variant_ident {
+                            #(#field_conversions),*
+                        })
+                    })()
+                    .field(&#js_discriminant)?),
+                }
+            }
+        }
+    });
+
+    let expanded = quote! {
+        impl #impl_generics crate::helpers::TryFromJs for #enum_ident #ty_generics #where_clause {
+            fn try_from_js<'cx, 'b>(cx: &mut impl neon::prelude::Context<'cx>, js_value: neon::prelude::Handle<'b, neon::prelude::JsValue>) -> crate::helpers::BridgeResult<Self> {
+                use crate::helpers::*;
+
+                let obj = js_value.downcast::<neon::prelude::JsObject, _>(cx)?;
+                let type_str: String = obj.get_property_into(cx, "type")?;
+
+                match type_str.as_str() {
+                    #(#variant_conversions)*
+                    _ => Err(crate::helpers::BridgeError::InvalidVariant {
+                        enum_name: #enum_name.to_string(),
+                        variant: type_str,
+                    }),
+                }
+            }
+        }
+    };
+
+    // Uncomment this line to print the expanded macro
+    // eprintln!(
+    //     "=== enum {} ===\n{}\n======",
+    //     enum_ident.to_string(),
+    //     expanded
+    // );
+
+    TokenStream::from(expanded)
+}
+
+fn field_conversions_for_named_fields(
+    fields: &FieldsNamed,
+) -> impl Iterator<Item = TokenStream> + '_ {
+    fields.named.iter().map(|f| {
+        let field_ident = f
+            .ident
+            .as_ref()
+            .expect("FieldsNamed.named must have an identifier");
+        let js_name = field_ident.to_string().to_case(Case::Camel);
+
+        quote! {
+            #field_ident: {
+                obj.get_property_into(cx, #js_name)?
+            }
+        }
+    })
+}
diff --git a/packages/core-bridge/bridge-macros/src/derive_tryintojs.rs b/packages/core-bridge/bridge-macros/src/derive_tryintojs.rs
new file mode 100644
index 000000000..e3fe94301
--- /dev/null
+++ b/packages/core-bridge/bridge-macros/src/derive_tryintojs.rs
@@ -0,0 +1,154 @@
+use convert_case::{Case, Casing};
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{DeriveInput, FieldsNamed};
+
+pub fn derive_tryintojs_struct(input: &DeriveInput, data: &syn::DataStruct) -> TokenStream {
+    let struct_ident = &input.ident;
+    let generics = &input.generics;
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    let field_conversions = if let syn::Fields::Named(ref fields) = data.fields {
+        field_conversions_for_named_fields(fields)
+    } else {
+        panic!("Only named fields are supported")
+    };
+
+    let expanded = quote! {
+        impl #impl_generics crate::helpers::TryIntoJs for #struct_ident #ty_generics #where_clause {
+            type Output = neon::types::JsObject;
+
+            fn try_into_js<'a>(self, cx: &mut impl neon::prelude::Context<'a>) -> neon::result::JsResult<'a, Self::Output> {
+                let obj = cx.empty_object();
+                #(#field_conversions)*
+                Ok(obj)
+            }
+        }
+    };
+
+    TokenStream::from(expanded)
+}
+
+pub fn derive_tryintojs_enum(input: &DeriveInput, data: &syn::DataEnum) -> TokenStream {
+    let enum_ident = &input.ident;
+    let generics = &input.generics;
+    let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+    let variant_conversions = data.variants.iter().map(|v| {
+        let variant_ident = &v.ident;
+        let js_discriminant = variant_ident.to_string().to_case(Case::Camel);
+
+        match &v.fields {
+            syn::Fields::Unit => {
+                quote! {
+                    #enum_ident::#variant_ident => {
+                        let obj = cx.empty_object();
+                        let type_str = cx.string(#js_discriminant);
+                        obj.set(cx, "type", type_str)?;
+                        obj
+                    }
+                }
+            }
+            syn::Fields::Unnamed(fields) => {
+                if fields.unnamed.len() != 1 {
+                    panic!("Enum variants with unnamed fields must have exactly one field");
+                }
+
+                quote! {
+                    #enum_ident::#variant_ident(inner) => {
+                        let obj = cx.empty_object();
+                        let type_str = cx.string(#js_discriminant);
+                        obj.set(cx, "type", type_str)?;
+
+                        let inner_js = inner.try_into_js(cx)?;
+                        if inner_js.is_a::<neon::types::JsObject, _>(cx) {
+                            // If inner is a JsObject, copy its properties to our object
+                            let inner_obj = inner_js.downcast::<neon::types::JsObject, _>(cx).unwrap();
+                            let prop_names = inner_obj.get_own_property_names(cx)?.to_vec(cx)?;
+
+                            for key_handle in prop_names {
+                                let value = inner_obj.get_value(cx, key_handle)?;
+                                obj.set(cx, key_handle, value)?;
+                            }
+                        }
+
+                        obj
+                    }
+                }
+            }
+            syn::Fields::Named(fields) => {
+                let field_names = fields.named.iter().map(|f| {
+                    let field_ident = &f.ident;
+                    let js_name = field_ident.as_ref().unwrap().to_string().to_case(Case::Camel);
+                    (field_ident, js_name)
+                });
+
+                let pattern_fields = field_names.clone().map(|(field_ident, _)| {
+                    quote! { #field_ident }
+                });
+
+                let field_sets = field_names.map(|(field_ident, js_name)| {
+                    quote! {
+                        let js_value = #field_ident.try_into_js(cx)?;
+                        obj.set(cx, #js_name, js_value)?;
+                    }
+                });
+
+                quote! {
+                    #enum_ident::#variant_ident { #(#pattern_fields),* } => {
+                        let obj = cx.empty_object();
+                        let type_str = cx.string(#js_discriminant);
+                        obj.set(cx, "type", type_str)?;
+
+                        #(#field_sets)*
+
+                        obj
+                    }
+                }
+            }
+        }
+    });
+
+    let expanded = quote! {
+        impl #impl_generics crate::helpers::TryIntoJs for #enum_ident #ty_generics #where_clause {
+            type Output = neon::types::JsObject;
+
+            fn try_into_js<'a>(self, cx: &mut impl neon::prelude::Context<'a>) -> neon::result::JsResult<'a, Self::Output> {
+                Ok(match self {
+                    #(#variant_conversions),*
+                })
+            }
+        }
+    };
+
+    // Uncomment this line to print the expanded macro
+    // eprintln!("=== enum {} ===\n{}\n======", enum_ident.to_string(), expanded);
+
+    TokenStream::from(expanded)
+}
+
+fn field_conversions_for_named_fields(
+    fields: &FieldsNamed,
+) -> impl Iterator<Item = TokenStream> + '_ {
+    fields.named.iter().map(|f| {
+        let field_ident = f
+            .ident
+            .as_ref()
+            .expect("FieldsNamed.named must have an identifier");
+        let js_name = field_ident.to_string().to_case(Case::Camel);
+
+        // Ignore PhantomData fields
+        if let syn::Type::Path(path) = &f.ty {
+            if let Some(segment) = path.path.segments.last() {
+                if segment.ident == "PhantomData" {
+                    return quote! {};
+                }
+            }
+        }
+
+        quote! {
+            let js_value = self.#field_ident.try_into_js(cx)?;
+            obj.set(cx, #js_name, js_value)?;
+        }
+    })
+}
diff --git a/packages/core-bridge/bridge-macros/src/lib.rs b/packages/core-bridge/bridge-macros/src/lib.rs
new file mode 100644
index 000000000..f3e31a682
--- /dev/null
+++ b/packages/core-bridge/bridge-macros/src/lib.rs
@@ -0,0 +1,39 @@
+mod derive_js_function;
+mod derive_tryfromjs;
+mod derive_tryintojs;
+
+use derive_js_function::js_function_impl;
+use derive_tryfromjs::{derive_tryfromjs_enum, derive_tryfromjs_struct};
+use derive_tryintojs::{derive_tryintojs_enum, derive_tryintojs_struct};
+use proc_macro::TokenStream;
+use syn::{DeriveInput, parse_macro_input};
+
+/// Procedural macro for defining bridge types with compile-time field name conversion
+#[proc_macro_derive(TryFromJs)]
+pub fn try_from_js(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+
+    match &input.data {
+        syn::Data::Struct(data) => derive_tryfromjs_struct(&input, data).into(),
+        syn::Data::Enum(data) => derive_tryfromjs_enum(&input, data).into(),
+        syn::Data::Union(_) => panic!("Unions are not supported"),
+    }
+}
+
+/// Procedural macro for defining bridge types with compile-time field name conversion
+#[proc_macro_derive(TryIntoJs)]
+pub fn try_into_js(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+
+    match &input.data {
+        syn::Data::Struct(data) => derive_tryintojs_struct(&input, data).into(),
+        syn::Data::Enum(data) => derive_tryintojs_enum(&input, data).into(),
+        syn::Data::Union(_) => panic!("Unions are not supported"),
+    }
+}
+
+/// Generates a function that can be called from JavaScript with the given name
+#[proc_macro_attribute]
+pub fn js_function(attr: TokenStream, input: TokenStream) -> TokenStream {
+    js_function_impl(attr, input)
+}
diff --git a/packages/core-bridge/index.js b/packages/core-bridge/index.js
index 2c6e92aba..3ca13a77f 100644
--- a/packages/core-bridge/index.js
+++ b/packages/core-bridge/index.js
@@ -2,30 +2,86 @@ const { getPrebuiltPath } = require('./common');
 const typescriptExports = require('./lib/index');
 const { convertFromNamedError } = require('./lib/errors');
 
+/**
+ * Wraps calls to native functions to convert "named errors" to the correct error types.
+ */
 function wrapErrors(fn) {
   return (...args) => {
     try {
-      // Some of our native functions expect callback functions. When present, these callbacks are
-      // always the last argument passed to the function, and always adhere to the signature
-      // `callback(err, result)`. If a callback is present, then make sure that errors sent
-      // to it are also converted.
-      if (typeof args[args.length - 1] === 'function') {
-        const callback = args[args.length - 1];
-        args[args.length - 1] = (e, x) => callback(convertFromNamedError(e, false), x);
+      let res = fn(...args);
+      if (res instanceof Promise) {
+        return res.catch((e) => {
+          throw convertFromNamedError(e, false);
+        });
       }
-      return fn(...args);
+      return res;
     } catch (e) {
       throw convertFromNamedError(e, true);
     }
   };
 }
+let wrapper = (f) => wrapErrors(f);
+
+/**
+ * Wraps calls to native functions to add tracing logs.
+ *
+ * IMPORTANT: This is meant for internal SDK debugging only.
+ *            Always disable this block before committing back to the repo.
+ */
+// FIXME(JWH): DO NOT COMMIT THIS LINE
+if (process.env.TEMPORAL_TRACE_NATIVE_CALLS?.toLowerCase() === 'true') {
+  // Generate a random 4-character ID for the current execution
+  let execId = Math.random().toString(36).substring(2, 6);
+  let callSequence = 100000;
+
+  function wrapDebug(fn, fnname) {
+    // Functions names looks like `temporal_sdk_typescript_bridge::logs::get_time_of_day`
+    // Strip the path to retain only the function name
+    fnname = fnname.substring(fnname.lastIndexOf('::') + 2);
+
+    // Do not trace these functions, they are way too verbose
+    const ignored = ['get_time_of_day', 'poll_logs'];
+    if (ignored.includes(fnname)) return fn;
+
+    return (...args) => {
+      let callid = `${execId}:${String(callSequence++).substring(1)}`;
+
+      try {
+        console.log(`${new Date().toISOString()} @@@@ ${callid} ${fnname}() - calling in`);
+
+        let res = fn(...args);
+
+        if (res instanceof Promise) {
+          console.log(`${new Date().toISOString()} @@@@ ${callid} ${fnname}() - received promise`);
+          return res.then(
+            (x) => {
+              console.log(`${new Date().toISOString()} @@@@ ${callid} ${fnname}() - promise resolved`);
+              return x;
+            },
+            (e) => {
+              console.log(`${new Date().toISOString()} @@@@ ${callid} ${fnname}() - promise rejected with ${e}`);
+              throw convertFromNamedError(e, false);
+            }
+          );
+        } else {
+          console.log(`${new Date().toISOString()} @@@@ ${callid} ${fnname}() - returned`);
+        }
+
+        return res;
+      } catch (e) {
+        console.log(`${new Date().toISOString()} @@@@ ${callid} ${fnname}() - threw an error ${e}`);
+        throw convertFromNamedError(e, true);
+      }
+    };
+  }
+
+  wrapper = (f) => wrapDebug(wrapErrors(f), f.name);
+}
 
 try {
   const nativeLibPath = getPrebuiltPath();
-  const nativeExports = Object.fromEntries(
-    Object.entries(require(nativeLibPath)).map(([name, fn]) => [name, wrapErrors(fn)])
-  );
-  module.exports = { ...typescriptExports, ...nativeExports };
+  const native = Object.fromEntries(Object.entries(require(nativeLibPath)).map(([name, fn]) => [name, wrapper(fn)]));
+  module.exports = { ...typescriptExports, native };
 } catch (err) {
   throw err;
 }
diff --git a/packages/core-bridge/src/client.rs b/packages/core-bridge/src/client.rs
new file mode 100644
index 000000000..76bce1dac
--- /dev/null
+++ b/packages/core-bridge/src/client.rs
@@ -0,0 +1,209 @@
+use std::{collections::HashMap, sync::Arc};
+
+use neon::prelude::*;
+
+use temporal_client::{ClientInitError, ConfiguredClient, TemporalServiceClientWithMetrics};
+use temporal_sdk_core::{ClientOptions as CoreClientOptions, CoreRuntime, RetryClient};
+
+use bridge_macros::js_function;
+
+use crate::runtime::Runtime;
+use crate::{helpers::*, runtime::RuntimeExt as _};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+type CoreClient = RetryClient<ConfiguredClient<TemporalServiceClientWithMetrics>>;
+
+pub struct Client {
+    // These fields are pub because they are accessed from Worker::new
+    pub(crate) core_runtime: Arc<CoreRuntime>,
+    pub(crate) core_client: CoreClient,
+}
+
+impl Finalize for Client {}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub fn init(cx: &mut neon::prelude::ModuleContext) -> neon::prelude::NeonResult<()> {
+    cx.export_function("newClient", client_new)?;
+    cx.export_function("clientUpdateHeaders", client_update_headers)?;
+    cx.export_function("clientUpdateApiKey", client_update_api_key)?;
+    cx.export_function("clientClose", client_close)?;
+
+    Ok(())
+}
+
+/// Create a connected gRPC client which can be used to initialize workers.
+#[js_function]
+pub fn client_new(
+    runtime: OpaqueInboundHandle<Runtime>,
+    config: config::BridgeClientOptions,
+) -> BridgeResult<BridgeFuture<OpaqueOutboundHandle<Client>>> {
+    let runtime = runtime.borrow_inner()?.core_runtime.clone();
+    let config: CoreClientOptions = config.try_into()?;
+
+    runtime.clone().future_to_promise(async move {
+        let metric_meter = runtime.clone().telemetry().get_temporal_metric_meter();
+
+        let res = config.connect_no_namespace(metric_meter).await;
+
+        let core_client = match res {
+            Ok(core_client) => core_client,
+            Err(ClientInitError::SystemInfoCallError(e)) => Err(BridgeError::TransportError(
+                format!("Failed to call GetSystemInfo: {e}"),
+            ))?,
+            Err(ClientInitError::TonicTransportError(e)) => {
+                Err(BridgeError::TransportError(format!("{e:?}")))?
+            }
+            Err(ClientInitError::InvalidUri(e)) => Err(BridgeError::TypeError {
+                message: e.to_string(),
+                field: None,
+            })?,
+        };
+
+        Ok(OpaqueOutboundHandle::new(Client {
+            core_runtime: runtime,
+            core_client,
+        }))
+    })
+}
+
+/// Update a Client's HTTP request headers
+#[js_function]
+pub fn client_update_headers(
+    client: OpaqueInboundHandle<Client>,
+    headers: HashMap<String, String>,
+) -> BridgeResult<()> {
+    client
+        .borrow_inner()?
+        .core_client
+        .get_client()
+        .set_headers(headers);
+    Ok(())
+}
+
+/// Update a Client's API key
+#[js_function]
+pub fn client_update_api_key(client: OpaqueInboundHandle<Client>, key: String) -> BridgeResult<()> {
+    client
+        .borrow_inner()?
+        .core_client
+        .get_client()
+        .set_api_key(Some(key));
+    Ok(())
+}
+
+#[js_function]
+pub fn client_close(client: OpaqueInboundHandle<Client>) -> BridgeResult<()> {
+    // Just drop the client; there's actually no "close" method on Client.
+    let _client = client.take_inner()?;
+    Ok(())
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+mod config {
+    use std::collections::HashMap;
+
+    use anyhow::Context as _;
+
+    use temporal_client::HttpConnectProxyOptions;
+    use temporal_sdk_core::{
+        ClientOptions as CoreClientOptions, ClientOptionsBuilder, ClientTlsConfig,
+        TlsConfig as CoreTlsConfig, Url,
+    };
+
+    use bridge_macros::TryFromJs;
+
+    use crate::helpers::*;
+
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) struct BridgeClientOptions {
+        url: Url,
+        sdk_version: String,
+        tls: Option<TlsConfig>,
+        proxy: Option<ProxyConfig>,
+        metadata: Option<HashMap<String, String>>,
+        api_key: Option<String>,
+        disable_error_code_metric_tags: bool,
+    }
+
+    impl TryInto<CoreClientOptions> for BridgeClientOptions {
+        type Error = BridgeError;
+
+        fn try_into(self) -> Result<CoreClientOptions, Self::Error> {
+            let mut builder = ClientOptionsBuilder::default();
+
+            if let Some(tls) = self.tls {
+                builder.tls_cfg(tls.try_into()?);
+            }
+
+            if let Some(proxy) = self.proxy {
+                builder.http_connect_proxy(Some(proxy.try_into()?));
+            }
+
+            let client_options = builder
+                .target_url(self.url)
+                .client_name("temporal-typescript".to_string())
+                .client_version(self.sdk_version)
+                .headers(self.metadata)
+                .api_key(self.api_key)
+                .disable_error_code_metric_tags(self.disable_error_code_metric_tags)
+                .build()
+                .context("Invalid client options")?;
+
+            Ok(client_options)
+        }
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    struct TlsConfig {
+        server_name_override: Option<String>,
+        server_root_ca_certificate: Option<Vec<u8>>,
+        client_cert_pair: Option<ClientTlsConfigPair>,
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    struct ClientTlsConfigPair {
+        crt: Vec<u8>,
+        key: Vec<u8>,
+    }
+
+    impl TryInto<CoreTlsConfig> for TlsConfig {
+        type Error = BridgeError;
+
+        fn try_into(self) -> Result<CoreTlsConfig, Self::Error> {
+            Ok(CoreTlsConfig {
+                server_root_ca_cert: self.server_root_ca_certificate,
+                domain: self.server_name_override,
+                client_tls_config: self.client_cert_pair.map(|pair| ClientTlsConfig {
+                    client_cert: pair.crt,
+                    client_private_key: pair.key,
+                }),
+            })
+        }
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    struct ProxyConfig {
+        target_host: String,
+        basic_auth: Option<ProxyBasicAuth>,
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    struct ProxyBasicAuth {
+        username: String,
+        password: String,
+    }
+
+    impl TryInto<HttpConnectProxyOptions> for ProxyConfig {
+        type Error = BridgeError;
+
+        fn try_into(self) -> Result<HttpConnectProxyOptions, Self::Error> {
+            Ok(HttpConnectProxyOptions {
+                target_addr: self.target_host,
+                basic_auth: self.basic_auth.map(|auth| (auth.username, auth.password)),
+            })
+        }
+    }
+}
diff --git a/packages/core-bridge/src/conversions.rs b/packages/core-bridge/src/conversions.rs
deleted file mode 100644
index 2c2da9d07..000000000
--- a/packages/core-bridge/src/conversions.rs
+++ /dev/null
@@ -1,698 +0,0 @@
-use crate::helpers::*;
-use neon::{
-    context::Context,
-    handle::Handle,
-    prelude::*,
-    types::{JsBoolean, JsNumber, JsString},
-};
-use slot_supplier_bridge::SlotSupplierBridge;
-use std::{collections::HashMap, net::SocketAddr, sync::Arc, time::Duration};
-use temporal_client::HttpConnectProxyOptions;
-use temporal_sdk_core::api::{
-    telemetry::{HistogramBucketOverrides, OtlpProtocol},
-    worker::{PollerBehavior, SlotKind},
-};
-use temporal_sdk_core::{
-    ClientOptions, ClientOptionsBuilder, ClientTlsConfig, ResourceBasedSlotsOptions,
-    ResourceBasedSlotsOptionsBuilder, ResourceSlotOptions, RetryConfig, SlotSupplierOptions,
-    TlsConfig, TunerHolderOptionsBuilder, Url,
-    api::telemetry::{Logger, MetricTemporality, TelemetryOptions, TelemetryOptionsBuilder},
-    api::{
-        telemetry::{
-            OtelCollectorOptionsBuilder, PrometheusExporterOptionsBuilder, metrics::CoreMeter,
-        },
-        worker::{WorkerConfig, WorkerConfigBuilder},
-    },
-    ephemeral_server::{
-        TemporalDevServerConfig, TemporalDevServerConfigBuilder, TestServerConfig,
-        TestServerConfigBuilder,
-    },
-    telemetry::{build_otlp_metric_exporter, start_prometheus_metric_exporter},
-};
-
-mod slot_supplier_bridge;
-
-pub enum EphemeralServerConfig {
-    TestServer(TestServerConfig),
-    DevServer(TemporalDevServerConfig),
-}
-
-pub trait ArrayHandleConversionsExt {
-    fn to_vec_of_string(&self, cx: &mut FunctionContext) -> NeonResult<Vec<String>>;
-    fn to_vec_of_float(&self, cx: &mut FunctionContext) -> NeonResult<Vec<f64>>;
-}
-
-impl ArrayHandleConversionsExt for Handle<'_, JsArray> {
-    fn to_vec_of_string(&self, cx: &mut FunctionContext) -> NeonResult<Vec<String>> {
-        let js_vec = self.to_vec(cx)?;
-        let len = js_vec.len();
-        let mut ret_vec = Vec::<String>::with_capacity(len);
-
-        for i in js_vec.iter().take(len) {
-            ret_vec.push(i.downcast_or_throw::<JsString, _>(cx)?.value(cx));
-        }
-        Ok(ret_vec)
-    }
-
-    fn to_vec_of_float(&self, cx: &mut FunctionContext) -> NeonResult<Vec<f64>> {
-        let js_vec = self.to_vec(cx)?;
-        let len = js_vec.len();
-        let mut ret_vec = Vec::<f64>::with_capacity(len);
-
-        for i in js_vec.iter().take(len) {
-            ret_vec.push(i.downcast_or_throw::<JsNumber, _>(cx)?.value(cx));
-        }
-        Ok(ret_vec)
-    }
-}
-
-type BoxedMeterMaker = Box<dyn FnOnce() -> Result<Arc<dyn CoreMeter>, String> + Send + Sync>;
-
-pub(crate) type TelemOptsRes = (TelemetryOptions, Option<BoxedMeterMaker>);
-
-pub(crate) trait ObjectHandleConversionsExt {
-    fn set_default(&self, cx: &mut FunctionContext, key: &str, value: &str) -> NeonResult<()>;
-    fn as_client_options(&self, ctx: &mut FunctionContext) -> NeonResult<ClientOptions>;
-    fn as_telemetry_options(&self, cx: &mut FunctionContext) -> NeonResult<TelemOptsRes>;
-    fn as_worker_config(&self, cx: &mut FunctionContext) -> NeonResult<WorkerConfig>;
-    fn as_ephemeral_server_config(
-        &self,
-        cx: &mut FunctionContext,
-        sdk_version: String,
-    ) -> NeonResult<EphemeralServerConfig>;
-    fn as_hash_map_of_string_to_string(
-        &self,
-        cx: &mut FunctionContext,
-    ) -> NeonResult<HashMap<String, String>>;
-    fn as_hash_map_of_string_to_vec_of_floats(
-        &self,
-        cx: &mut FunctionContext,
-    ) -> NeonResult<HashMap<String, Vec<f64>>>;
-    fn into_slot_supplier<SK: SlotKind + Send + Sync + 'static>(
-        self,
-        cx: &mut FunctionContext,
-        rbo: &mut Option<ResourceBasedSlotsOptions>,
-    ) -> NeonResult<SlotSupplierOptions<SK>>;
-}
-
-impl ObjectHandleConversionsExt for Handle<'_, JsObject> {
-    fn as_hash_map_of_string_to_string(
-        &self,
-        cx: &mut FunctionContext,
-    ) -> NeonResult<HashMap<String, String>> {
-        let props = self.get_own_property_names(cx)?;
-        let props = props.to_vec(cx)?;
-        let mut map = HashMap::new();
-        for k in props {
-            let k = k.to_string(cx)?;
-            let v = self.get::<JsString, _, _>(cx, k)?.value(cx);
-            let k = k.value(cx);
-            map.insert(k, v);
-        }
-        Ok(map)
-    }
-
-    fn as_hash_map_of_string_to_vec_of_floats(
-        &self,
-        cx: &mut FunctionContext,
-    ) -> NeonResult<HashMap<String, Vec<f64>>> {
-        let props = self.get_own_property_names(cx)?;
-        let props = props.to_vec(cx)?;
-        let mut map = HashMap::new();
-        for k in props {
-            let k = k.to_string(cx)?;
-            let v = self.get::<JsArray, _, _>(cx, k)?.to_vec_of_float(cx)?;
-            let k = k.value(cx);
-            map.insert(k, v);
-        }
-        Ok(map)
-    }
-
-    fn as_client_options(&self, cx: &mut FunctionContext) -> NeonResult<ClientOptions> {
-        let url = match Url::parse(&js_value_getter!(cx, self, "url", JsString)) {
-            Ok(url) => url,
-            // Note that address is what's used in the Node side.
-            Err(_) => cx.throw_type_error("Invalid serverOptions.address")?,
-        };
-
-        let tls_cfg = match js_optional_getter!(cx, self, "tls", JsObject) {
-            None => None,
-            Some(tls) => {
-                let domain = js_optional_value_getter!(cx, &tls, "serverNameOverride", JsString);
-
-                let server_root_ca_cert = get_optional_vec(cx, &tls, "serverRootCACertificate")?;
-                let client_tls_config =
-                    match js_optional_getter!(cx, &tls, "clientCertPair", JsObject) {
-                        None => None,
-                        Some(client_tls_obj) => Some(ClientTlsConfig {
-                            client_cert: get_vec(
-                                cx,
-                                &client_tls_obj,
-                                "crt",
-                                "serverOptions.tls.clientCertPair.crt",
-                            )?,
-                            client_private_key: get_vec(
-                                cx,
-                                &client_tls_obj,
-                                "key",
-                                "serverOptions.tls.clientCertPair.crt",
-                            )?,
-                        }),
-                    };
-
-                Some(TlsConfig {
-                    server_root_ca_cert,
-                    domain,
-                    client_tls_config,
-                })
-            }
-        };
-
-        let proxy_cfg = match js_optional_getter!(cx, self, "proxy", JsObject) {
-            None => None,
-            Some(proxy) => {
-                let target_addr = js_value_getter!(cx, &proxy, "targetHost", JsString);
-
-                let basic_auth = match js_optional_getter!(cx, &proxy, "basicAuth", JsObject) {
-                    None => None,
-                    Some(proxy_obj) => Some((
-                        js_value_getter!(cx, &proxy_obj, "username", JsString),
-                        js_value_getter!(cx, &proxy_obj, "password", JsString),
-                    )),
-                };
-
-                Some(HttpConnectProxyOptions {
-                    target_addr,
-                    basic_auth,
-                })
-            }
-        };
-
-        let retry_config = match js_optional_getter!(cx, self, "retry", JsObject) {
-            None => RetryConfig::default(),
-            Some(ref retry_config) => RetryConfig {
-                initial_interval: Duration::from_millis(js_value_getter!(
-                    cx,
-                    retry_config,
-                    "initialInterval",
-                    JsNumber
-                ) as u64),
-                randomization_factor: js_value_getter!(
-                    cx,
-                    retry_config,
-                    "randomizationFactor",
-                    JsNumber
-                ),
-                multiplier: js_value_getter!(cx, retry_config, "multiplier", JsNumber),
-                max_interval: Duration::from_millis(js_value_getter!(
-                    cx,
-                    retry_config,
-                    "maxInterval",
-                    JsNumber
-                ) as u64),
-                max_elapsed_time: js_optional_value_getter!(
-                    cx,
-                    retry_config,
-                    "maxElapsedTime",
-                    JsNumber
-                )
-                .map(|val| Duration::from_millis(val as u64)),
-                max_retries: js_value_getter!(cx, retry_config, "maxRetries", JsNumber) as usize,
-            },
-        };
-
-        let mut client_options = ClientOptionsBuilder::default();
-        if let Some(tls_cfg) = tls_cfg {
-            client_options.tls_cfg(tls_cfg);
-        }
-        client_options.http_connect_proxy(proxy_cfg);
-        let headers = match js_optional_getter!(cx, self, "metadata", JsObject) {
-            None => None,
-            Some(h) => Some(h.as_hash_map_of_string_to_string(cx).map_err(|reason| {
-                cx.throw_type_error::<_, HashMap<String, String>>(format!(
-                    "Invalid metadata: {}",
-                    reason
-                ))
-                .unwrap_err()
-            })?),
-        };
-        client_options.headers(headers);
-        client_options.api_key(js_optional_value_getter!(cx, self, "apiKey", JsString));
-
-        Ok(client_options
-            .client_name("temporal-typescript".to_string())
-            .client_version(js_value_getter!(cx, self, "sdkVersion", JsString))
-            .target_url(url)
-            .retry_config(retry_config)
-            .disable_error_code_metric_tags(js_value_getter!(
-                cx,
-                self,
-                "disableErrorCodeMetricTags",
-                JsBoolean
-            ))
-            .build()
-            .expect("Core server gateway options must be valid"))
-    }
-
-    fn as_telemetry_options(&self, cx: &mut FunctionContext) -> NeonResult<TelemOptsRes> {
-        let mut telemetry_opts = TelemetryOptionsBuilder::default();
-
-        if let Some(ref logging) = js_optional_getter!(cx, self, "logging", JsObject) {
-            let filter = js_value_getter!(cx, logging, "filter", JsString);
-            if get_optional(cx, logging, "console").is_some() {
-                telemetry_opts.logging(Logger::Console { filter });
-            } else if get_optional(cx, logging, "forward").is_some() {
-                telemetry_opts.logging(Logger::Forward { filter });
-            } else {
-                cx.throw_type_error(
-                    "Invalid telemetryOptions.logging, expected either 'console' or 'forward' property",
-                )?;
-            }
-        }
-
-        let mut meter_maker = None;
-
-        if let Some(ref metrics) = js_optional_getter!(cx, self, "metrics", JsObject) {
-            telemetry_opts.metric_prefix(js_value_getter!(cx, metrics, "metricPrefix", JsString));
-
-            let global_tags = match js_optional_getter!(cx, metrics, "globalTags", JsObject) {
-                None => None,
-                Some(global_tags) => Some(global_tags.as_hash_map_of_string_to_string(cx)?),
-            };
-
-            telemetry_opts.attach_service_name(js_value_getter!(
-                cx,
-                metrics,
-                "attachServiceName",
-                JsBoolean
-            ));
-
-            if let Some(ref prom) = js_optional_getter!(cx, metrics, "prometheus", JsObject) {
-                if js_optional_getter!(cx, metrics, "otel", JsObject).is_some() {
-                    cx.throw_type_error(
-                        "Invalid telemetryOptions.metrics: can't have both premetheus and otel at the same time",
-                    )?
-                }
-
-                let mut options = PrometheusExporterOptionsBuilder::default();
-
-                let addr = js_value_getter!(cx, prom, "bindAddress", JsString);
-                match addr.parse::<SocketAddr>() {
-                    Ok(addr) => options.socket_addr(addr),
-                    Err(_) => {
-                        return cx.throw_type_error(
-                            "Invalid telemetryOptions.metrics.prometheus.bindAddress",
-                        )?;
-                    }
-                };
-
-                options.counters_total_suffix(js_value_getter!(
-                    cx,
-                    prom,
-                    "countersTotalSuffix",
-                    JsBoolean
-                ));
-
-                options.unit_suffix(js_value_getter!(cx, prom, "unitSuffix", JsBoolean));
-
-                options.use_seconds_for_durations(js_value_getter!(
-                    cx,
-                    prom,
-                    "useSecondsForDurations",
-                    JsBoolean
-                ));
-
-                if let Some(global_tags) = global_tags {
-                    options.global_tags(global_tags);
-                }
-
-                if let Some(histogram_bucket_overrides) =
-                    js_optional_getter!(cx, prom, "histogramBucketOverrides", JsObject)
-                {
-                    options.histogram_bucket_overrides(HistogramBucketOverrides {
-                        overrides: histogram_bucket_overrides
-                            .as_hash_map_of_string_to_vec_of_floats(cx)?,
-                    });
-                }
-
-                let options = options.build().map_err(|e| {
-                    cx.throw_type_error::<_, TelemetryOptions>(format!(
-                        "Failed to build prometheus exporter options: {:?}",
-                        e
-                    ))
-                    .unwrap_err()
-                })?;
-
-                meter_maker =
-                    Some(
-                        Box::new(move || match start_prometheus_metric_exporter(options) {
-                            Ok(prom_info) => Ok(prom_info.meter as Arc<dyn CoreMeter>),
-                            Err(e) => Err(format!("Failed to start prometheus exporter: {}", e)),
-                        }) as BoxedMeterMaker,
-                    );
-            } else if let Some(ref otel) = js_optional_getter!(cx, metrics, "otel", JsObject) {
-                let mut options = OtelCollectorOptionsBuilder::default();
-
-                let url = js_value_getter!(cx, otel, "url", JsString);
-                match Url::parse(&url) {
-                    Ok(url) => options.url(url),
-                    Err(e) => {
-                        return cx.throw_type_error(format!(
-                            "Invalid telemetryOptions.metrics.otel.url: {}",
-                            e
-                        ))?;
-                    }
-                };
-
-                if js_value_getter!(cx, otel, "http", JsBoolean) {
-                    options.protocol(OtlpProtocol::Http);
-                } else {
-                    options.protocol(OtlpProtocol::Grpc);
-                }
-
-                if let Some(ref headers) = js_optional_getter!(cx, otel, "headers", JsObject) {
-                    options.headers(headers.as_hash_map_of_string_to_string(cx)?);
-                };
-
-                if let Some(metric_periodicity) =
-                    js_optional_value_getter!(cx, otel, "metricsExportInterval", JsNumber)
-                        .map(|f| f as u64)
-                {
-                    options.metric_periodicity(Duration::from_millis(metric_periodicity));
-                }
-
-                options.use_seconds_for_durations(js_value_getter!(
-                    cx,
-                    otel,
-                    "useSecondsForDurations",
-                    JsBoolean
-                ));
-
-                match js_value_getter!(cx, otel, "temporality", JsString).as_str() {
-                    "cumulative" => options.metric_temporality(MetricTemporality::Cumulative),
-                    "delta" => options.metric_temporality(MetricTemporality::Delta),
-                    _ => {
-                        return cx.throw_type_error("Invalid telemetryOptions.metrics.otel.temporality, expected 'cumulative' or 'delta'");
-                    }
-                };
-
-                if let Some(global_tags) = global_tags {
-                    options.global_tags(global_tags);
-                }
-
-                if let Some(histogram_bucket_overrides) =
-                    js_optional_getter!(cx, otel, "histogramBucketOverrides", JsObject)
-                {
-                    options.histogram_bucket_overrides(HistogramBucketOverrides {
-                        overrides: histogram_bucket_overrides
-                            .as_hash_map_of_string_to_vec_of_floats(cx)?,
-                    });
-                }
-
-                let options = options.build().map_err(|e| {
-                    cx.throw_type_error::<_, TelemetryOptions>(format!(
-                        "Failed to build otlp exporter options: {:?}",
-                        e
-                    ))
-                    .unwrap_err()
-                })?;
-
-                meter_maker = Some(Box::new(move || match build_otlp_metric_exporter(options) {
-                    Ok(otlp_exporter) => Ok(Arc::new(otlp_exporter) as Arc<dyn CoreMeter>),
-                    Err(e) => Err(format!("Failed to start otlp exporter: {}", e)),
-                }) as BoxedMeterMaker);
-            } else {
-                cx.throw_type_error(
-                    "Invalid telemetryOptions.metrics, missing `prometheus` or `otel` option",
-                )?
-            }
-        }
-
-        Ok((
-            telemetry_opts.build().map_err(|reason| {
-                cx.throw_type_error::<_, TelemetryOptions>(format!("{}", reason))
-                    .unwrap_err()
-            })?,
-            meter_maker,
-        ))
-    }
-
-    fn as_worker_config(&self, cx: &mut FunctionContext) -> NeonResult<WorkerConfig> {
-        let namespace = js_value_getter!(cx, self, "namespace", JsString);
-        let task_queue = js_value_getter!(cx, self, "taskQueue", JsString);
-        let enable_remote_activities =
-            js_value_getter!(cx, self, "enableNonLocalActivities", JsBoolean);
-        let max_concurrent_wft_polls =
-            js_value_getter!(cx, self, "maxConcurrentWorkflowTaskPolls", JsNumber) as usize;
-        let max_concurrent_at_polls =
-            js_value_getter!(cx, self, "maxConcurrentActivityTaskPolls", JsNumber) as usize;
-        let sticky_queue_schedule_to_start_timeout = Duration::from_millis(js_value_getter!(
-            cx,
-            self,
-            "stickyQueueScheduleToStartTimeoutMs",
-            JsNumber
-        ) as u64);
-        let max_cached_workflows =
-            js_value_getter!(cx, self, "maxCachedWorkflows", JsNumber) as usize;
-
-        let max_heartbeat_throttle_interval = Duration::from_millis(js_value_getter!(
-            cx,
-            self,
-            "maxHeartbeatThrottleIntervalMs",
-            JsNumber
-        ) as u64);
-
-        let default_heartbeat_throttle_interval = Duration::from_millis(js_value_getter!(
-            cx,
-            self,
-            "defaultHeartbeatThrottleIntervalMs",
-            JsNumber
-        ) as u64);
-
-        let max_worker_activities_per_second =
-            js_optional_getter!(cx, self, "maxActivitiesPerSecond", JsNumber)
-                .map(|num| num.value(cx));
-        let max_task_queue_activities_per_second =
-            js_optional_getter!(cx, self, "maxTaskQueueActivitiesPerSecond", JsNumber)
-                .map(|num| num.value(cx));
-
-        let graceful_shutdown_period =
-            js_optional_getter!(cx, self, "shutdownGraceTimeMs", JsNumber)
-                .map(|num| Duration::from_millis(num.value(cx) as u64));
-
-        let nonsticky_to_sticky_poll_ratio =
-            js_value_getter!(cx, self, "nonStickyToStickyPollRatio", JsNumber) as f32;
-
-        let tuner = if let Some(tuner) = js_optional_getter!(cx, self, "tuner", JsObject) {
-            let mut tuner_holder = TunerHolderOptionsBuilder::default();
-            let mut rbo = None;
-
-            if let Some(wf_slot_supp) =
-                js_optional_getter!(cx, &tuner, "workflowTaskSlotSupplier", JsObject)
-            {
-                tuner_holder.workflow_slot_options(wf_slot_supp.into_slot_supplier(cx, &mut rbo)?);
-            }
-            if let Some(act_slot_supp) =
-                js_optional_getter!(cx, &tuner, "activityTaskSlotSupplier", JsObject)
-            {
-                tuner_holder.activity_slot_options(act_slot_supp.into_slot_supplier(cx, &mut rbo)?);
-            }
-            if let Some(local_act_slot_supp) =
-                js_optional_getter!(cx, &tuner, "localActivityTaskSlotSupplier", JsObject)
-            {
-                tuner_holder.local_activity_slot_options(
-                    local_act_slot_supp.into_slot_supplier(cx, &mut rbo)?,
-                );
-            }
-            if let Some(rbo) = rbo {
-                tuner_holder.resource_based_options(rbo);
-            }
-            match tuner_holder.build_tuner_holder() {
-                Err(e) => {
-                    return cx.throw_error(format!("Invalid tuner options: {:?}", e));
-                }
-                Ok(th) => Arc::new(th),
-            }
-        } else {
-            return cx.throw_error("Missing tuner");
-        };
-
-        match WorkerConfigBuilder::default()
-            .worker_build_id(js_value_getter!(cx, self, "buildId", JsString))
-            .client_identity_override(Some(js_value_getter!(cx, self, "identity", JsString)))
-            .use_worker_versioning(js_value_getter!(cx, self, "useVersioning", JsBoolean))
-            .no_remote_activities(!enable_remote_activities)
-            .tuner(tuner)
-            .workflow_task_poller_behavior(PollerBehavior::SimpleMaximum(max_concurrent_wft_polls))
-            .activity_task_poller_behavior(PollerBehavior::SimpleMaximum(max_concurrent_at_polls))
-            .nonsticky_to_sticky_poll_ratio(nonsticky_to_sticky_poll_ratio)
-            .max_cached_workflows(max_cached_workflows)
-            .sticky_queue_schedule_to_start_timeout(sticky_queue_schedule_to_start_timeout)
-            .graceful_shutdown_period(graceful_shutdown_period)
-            .namespace(namespace)
-            .task_queue(task_queue)
-            .max_heartbeat_throttle_interval(max_heartbeat_throttle_interval)
-            .default_heartbeat_throttle_interval(default_heartbeat_throttle_interval)
-            .max_worker_activities_per_second(max_worker_activities_per_second)
-            .max_task_queue_activities_per_second(max_task_queue_activities_per_second)
-            .build()
-        {
-            Ok(worker_cfg) => Ok(worker_cfg),
-            Err(e) => cx.throw_error(format!("Invalid worker config: {:?}", e)),
-        }
-    }
-
-    fn set_default(&self, cx: &mut FunctionContext, key: &str, value: &str) -> NeonResult<()> {
-        let key = cx.string(key);
-        let existing: Option<Handle<JsString>> = self.get_opt(cx, key)?;
-        if existing.is_none() {
-            let value = cx.string(value);
-            self.set(cx, key, value)?;
-        }
-        Ok(())
-    }
-
-    fn as_ephemeral_server_config(
-        &self,
-        cx: &mut FunctionContext,
-        sdk_version: String,
-    ) -> NeonResult<EphemeralServerConfig> {
-        let js_executable = js_optional_getter!(cx, self, "executable", JsObject)
-            .unwrap_or_else(|| cx.empty_object());
-        js_executable.set_default(cx, "type", "cached-download")?;
-
-        let exec_type = js_value_getter!(cx, &js_executable, "type", JsString);
-        let executable = match exec_type.as_str() {
-            "cached-download" => {
-                let version = js_optional_value_getter!(cx, &js_executable, "version", JsString)
-                    .unwrap_or_else(|| "default".to_owned());
-                let dest_dir =
-                    js_optional_value_getter!(cx, &js_executable, "downloadDir", JsString);
-                let ttl = js_optional_value_getter!(cx, &self, "ttlMs", JsNumber);
-
-                let exec_version = match version.as_str() {
-                    "default" => {
-                        temporal_sdk_core::ephemeral_server::EphemeralExeVersion::SDKDefault {
-                            sdk_name: "sdk-typescript".to_owned(),
-                            sdk_version,
-                        }
-                    }
-                    _ => temporal_sdk_core::ephemeral_server::EphemeralExeVersion::Fixed(version),
-                };
-                temporal_sdk_core::ephemeral_server::EphemeralExe::CachedDownload {
-                    version: exec_version,
-                    dest_dir,
-                    ttl: ttl.map(|ttl| Duration::from_millis(ttl as u64)),
-                }
-            }
-            "existing-path" => {
-                let path = js_value_getter!(cx, &js_executable, "path", JsString);
-                temporal_sdk_core::ephemeral_server::EphemeralExe::ExistingPath(path)
-            }
-            _ => {
-                return cx.throw_type_error(format!("Invalid executable type: {}", exec_type))?;
-            }
-        };
-        let port = js_optional_getter!(cx, self, "port", JsNumber).map(|s| s.value(cx) as u16);
-
-        let server_type = js_value_getter!(cx, self, "type", JsString);
-        match server_type.as_str() {
-            "dev-server" => {
-                let mut config = TemporalDevServerConfigBuilder::default();
-                config.exe(executable).port(port);
-
-                if let Some(extra_args) = js_optional_getter!(cx, self, "extraArgs", JsArray) {
-                    config.extra_args(extra_args.to_vec_of_string(cx)?);
-                };
-                if let Some(namespace) = js_optional_value_getter!(cx, self, "namespace", JsString)
-                {
-                    config.namespace(namespace);
-                }
-                if let Some(ip) = js_optional_value_getter!(cx, self, "ip", JsString) {
-                    config.ip(ip);
-                }
-                config.db_filename(js_optional_value_getter!(cx, self, "dbFilename", JsString));
-                config.ui(js_optional_value_getter!(cx, self, "ui", JsBoolean).unwrap_or_default());
-                config.ui_port(
-                    js_optional_getter!(cx, self, "uiPort", JsNumber).map(|s| s.value(cx) as u16),
-                );
-                if let Some(log) = js_optional_getter!(cx, self, "log", JsObject) {
-                    let format = js_value_getter!(cx, &log, "format", JsString);
-                    let level = js_value_getter!(cx, &log, "level", JsString);
-                    config.log((format, level));
-                }
-
-                match config.build() {
-                    Ok(config) => Ok(EphemeralServerConfig::DevServer(config)),
-                    Err(err) => {
-                        cx.throw_type_error(format!("Invalid dev server config: {:?}", err))
-                    }
-                }
-            }
-            "time-skipping" => {
-                let mut config = TestServerConfigBuilder::default();
-                config.exe(executable).port(port);
-
-                if let Some(extra_args_js) = js_optional_getter!(cx, self, "extraArgs", JsArray) {
-                    let extra_args = extra_args_js.to_vec_of_string(cx)?;
-                    config.extra_args(extra_args);
-                };
-
-                match config.build() {
-                    Ok(config) => Ok(EphemeralServerConfig::TestServer(config)),
-                    Err(err) => {
-                        cx.throw_type_error(format!("Invalid test server config: {:?}", err))
-                    }
-                }
-            }
-            s => cx.throw_type_error(format!(
-                "Invalid ephemeral server type: {}, expected 'dev-server' or 'time-skipping'",
-                s
-            )),
-        }
-    }
-
-    fn into_slot_supplier<SK: SlotKind + Send + Sync + 'static>(
-        self,
-        cx: &mut FunctionContext,
-        rbo: &mut Option<ResourceBasedSlotsOptions>,
-    ) -> NeonResult<SlotSupplierOptions<SK>> {
-        match js_value_getter!(cx, &self, "type", JsString).as_str() {
-            "fixed-size" => Ok(SlotSupplierOptions::FixedSize {
-                slots: js_value_getter!(cx, &self, "numSlots", JsNumber) as usize,
-            }),
-            "resource-based" => {
-                let min_slots = js_value_getter!(cx, &self, "minimumSlots", JsNumber);
-                let max_slots = js_value_getter!(cx, &self, "maximumSlots", JsNumber);
-                let ramp_throttle = js_value_getter!(cx, &self, "rampThrottleMs", JsNumber) as u64;
-                if let Some(tuner_opts) = js_optional_getter!(cx, &self, "tunerOptions", JsObject) {
-                    let target_mem =
-                        js_value_getter!(cx, &tuner_opts, "targetMemoryUsage", JsNumber);
-                    let target_cpu = js_value_getter!(cx, &tuner_opts, "targetCpuUsage", JsNumber);
-                    *rbo = Some(
-                        ResourceBasedSlotsOptionsBuilder::default()
-                            .target_cpu_usage(target_cpu)
-                            .target_mem_usage(target_mem)
-                            .build()
-                            .expect("Building ResourceBasedSlotsOptions can't fail"),
-                    )
-                } else {
-                    return cx
-                        .throw_type_error("Resource based slot supplier requires tunerOptions");
-                };
-                Ok(SlotSupplierOptions::ResourceBased(
-                    ResourceSlotOptions::new(
-                        min_slots as usize,
-                        max_slots as usize,
-                        Duration::from_millis(ramp_throttle),
-                    ),
-                ))
-            }
-            "custom" => {
-                let ssb = SlotSupplierBridge::new(cx, self)?;
-                Ok(SlotSupplierOptions::Custom(Arc::new(ssb)))
-            }
-            _ => cx.throw_type_error("Invalid slot supplier type"),
-        }
-    }
-}
diff --git a/packages/core-bridge/src/conversions/slot_supplier_bridge.rs b/packages/core-bridge/src/conversions/slot_supplier_bridge.rs
deleted file mode 100644
index 6b418f8dd..000000000
--- a/packages/core-bridge/src/conversions/slot_supplier_bridge.rs
+++ /dev/null
@@ -1,288 +0,0 @@
-use crate::helpers::{get_optional, js_getter};
-use log::{error, warn};
-use neon::types::JsNull;
-use neon::{
-    context::Context,
-    context::FunctionContext,
-    event::Channel,
-    handle::{Handle, Root},
-    object::Object,
-    prelude::{JsBuffer, JsFunction, JsObject, JsPromise, JsUndefined, JsValue, NeonResult, Value},
-};
-use prost::Message;
-use std::{cell::RefCell, marker::PhantomData, sync::Arc, time::Duration};
-use temporal_sdk_core::api::worker::{
-    SlotKind, SlotKindType, SlotMarkUsedContext, SlotReleaseContext, SlotReservationContext,
-    SlotSupplier, SlotSupplierPermit,
-};
-use tokio::sync::oneshot;
-
-pub struct SlotSupplierBridge<SK> {
-    inner: Arc<Root<JsObject>>,
-    reserve_cb: Arc<Root<JsFunction>>,
-    try_reserve_cb: Arc<Root<JsFunction>>,
-    mark_used_cb: Arc<Root<JsFunction>>,
-    release_cb: Arc<Root<JsFunction>>,
-    channel: Channel,
-    _kind: PhantomData<SK>,
-}
-
-impl<SK> SlotSupplierBridge<SK> {
-    pub(crate) fn new(cx: &mut FunctionContext, obj: Handle<'_, JsObject>) -> NeonResult<Self> {
-        Ok(Self {
-            inner: Arc::new(obj.root(cx)),
-            // Callbacks for each function are cached to reduce calling overhead
-            reserve_cb: Arc::new(js_getter!(cx, &obj, "reserveSlot", JsFunction).root(cx)),
-            try_reserve_cb: Arc::new(js_getter!(cx, &obj, "tryReserveSlot", JsFunction).root(cx)),
-            mark_used_cb: Arc::new(js_getter!(cx, &obj, "markSlotUsed", JsFunction).root(cx)),
-            release_cb: Arc::new(js_getter!(cx, &obj, "releaseSlot", JsFunction).root(cx)),
-            channel: cx.channel(),
-            _kind: PhantomData,
-        })
-    }
-}
-
-struct BridgePermitData {
-    permit: Arc<Root<JsObject>>,
-}
-
-struct CallAbortOnDrop {
-    chan: Channel,
-    aborter: oneshot::Receiver<Root<JsFunction>>,
-}
-
-impl Drop for CallAbortOnDrop {
-    fn drop(&mut self) {
-        if let Ok(aborter) = self.aborter.try_recv() {
-            let _ = self.chan.try_send(move |mut cx| {
-                let cb = aborter.to_inner(&mut cx);
-                let this = cx.undefined();
-                let _ = cb.call(&mut cx, this, []);
-                Ok(())
-            });
-        }
-    }
-}
-
-static PERMIT_DATA_FIELD: &str = "permit_data";
-
-#[async_trait::async_trait]
-impl<SK: SlotKind + Send + Sync> SlotSupplier for SlotSupplierBridge<SK> {
-    type SlotKind = SK;
-
-    async fn reserve_slot(&self, ctx: &dyn SlotReservationContext) -> SlotSupplierPermit {
-        loop {
-            let inner = self.inner.clone();
-            let rcb = self.reserve_cb.clone();
-            let task_queue = ctx.task_queue().to_string();
-            let worker_identity = ctx.worker_identity().to_string();
-            let worker_build_id = ctx.worker_build_id().to_string();
-            let is_sticky = ctx.is_sticky();
-
-            let (callback_fut, _abort_on_drop) = match self
-                .channel
-                .send(move |mut cx| {
-                    let context = Self::mk_reserve_ctx(
-                        task_queue,
-                        worker_identity,
-                        worker_build_id,
-                        is_sticky,
-                        &mut cx,
-                    )?;
-                    let (aborter_tx, aborter) = oneshot::channel();
-                    let abort_on_drop = CallAbortOnDrop {
-                        chan: cx.channel(),
-                        aborter,
-                    };
-                    let aborter_tx = RefCell::new(Some(aborter_tx));
-                    let abort_func = JsFunction::new(&mut cx, move |mut cx| {
-                        let func: Handle<JsFunction> = cx.argument(0)?;
-                        if let Some(aborter_tx) = aborter_tx.take() {
-                            let _ = aborter_tx.send(func.root(&mut cx));
-                        }
-                        Ok(cx.undefined())
-                    })?
-                    .upcast();
-
-                    let this = (*inner).clone(&mut cx).into_inner(&mut cx);
-                    let val = rcb
-                        .to_inner(&mut cx)
-                        .call(&mut cx, this, [context, abort_func])?;
-                    let as_prom = val.downcast_or_throw::<JsPromise, _>(&mut cx)?;
-                    let fut = as_prom.to_future(&mut cx, |mut cx, result| match result {
-                        Ok(value) => {
-                            let permit_obj = JsObject::new(&mut cx);
-                            permit_obj.set(&mut cx, PERMIT_DATA_FIELD, value)?;
-                            Ok(Ok(permit_obj.root(&mut cx)))
-                        }
-                        Err(_) => Ok(Err(())),
-                    })?;
-                    Ok((fut, abort_on_drop))
-                })
-                .await
-            {
-                Ok(v) => v,
-                Err(e) => {
-                    warn!("Error reserving slot: {:?}", e);
-                    continue;
-                }
-            };
-
-            match callback_fut.await {
-                Ok(Ok(res)) => {
-                    let permit = SlotSupplierPermit::with_user_data(BridgePermitData {
-                        permit: Arc::new(res),
-                    });
-                    return permit;
-                }
-                // Error in user function
-                Ok(Err(())) => {
-                    // Nothing to do here. Error in user's function (or an abort).
-                    // Logging handled on the JS side.
-                }
-                Err(e) => {
-                    error!(
-                        "There was an error in the rust/node bridge while reserving a slot: {}",
-                        e
-                    );
-                }
-            }
-            // Wait a beat to avoid spamming errors
-            tokio::time::sleep(Duration::from_millis(1000)).await;
-        }
-    }
-
-    fn try_reserve_slot(&self, ctx: &dyn SlotReservationContext) -> Option<SlotSupplierPermit> {
-        let inner = self.inner.clone();
-        let rcb = self.try_reserve_cb.clone();
-        let task_queue = ctx.task_queue().to_string();
-        let worker_identity = ctx.worker_identity().to_string();
-        let worker_build_id = ctx.worker_build_id().to_string();
-        let is_sticky = ctx.is_sticky();
-
-        // This is... unfortunate but since this method is called from an async context way up
-        // the stack, but is not async itself AND we need some way to get the result from the JS
-        // callback, we must use this roundabout way of blocking. Simply calling `join` on the
-        // channel send won't work - it'll panic because it calls block_on internally.
-        let runtime_handle = tokio::runtime::Handle::current();
-        let _entered = runtime_handle.enter();
-        let callback_res = futures::executor::block_on(self.channel.send(move |mut cx| {
-            let context = Self::mk_reserve_ctx(
-                task_queue,
-                worker_identity,
-                worker_build_id,
-                is_sticky,
-                &mut cx,
-            )?;
-
-            let this = (*inner).clone(&mut cx).into_inner(&mut cx);
-            let val = rcb.to_inner(&mut cx).call(&mut cx, this, [context])?;
-            if val.is_a::<JsUndefined, _>(&mut cx) || val.is_a::<JsNull, _>(&mut cx) {
-                return Ok(None);
-            }
-            let permit_obj = JsObject::new(&mut cx);
-            permit_obj.set(&mut cx, PERMIT_DATA_FIELD, val)?;
-            Ok(Some(permit_obj.root(&mut cx)))
-        }));
-
-        // Ignore errors, they'll be logged by JS
-        callback_res.ok().flatten().map(|res| {
-            SlotSupplierPermit::with_user_data(BridgePermitData {
-                permit: Arc::new(res),
-            })
-        })
-    }
-
-    fn mark_slot_used(&self, ctx: &dyn SlotMarkUsedContext<SlotKind = Self::SlotKind>) {
-        let inner = self.inner.clone();
-        let cb = self.mark_used_cb.clone();
-        let permit_data = ctx
-            .permit()
-            .user_data::<BridgePermitData>()
-            .map(|d| d.permit.clone());
-        // Get the slot info as bytes
-        let slot_info_bytes = ctx.info().encode_to_vec();
-
-        self.channel.send(move |mut cx| {
-            let context = JsObject::new(&mut cx);
-            if let Some(permit_obj) = permit_data {
-                let ph: Handle<JsObject> = permit_obj.to_inner(&mut cx);
-                let pd = ph.get_value(&mut cx, PERMIT_DATA_FIELD)?;
-                context.set(&mut cx, "permit", pd)?;
-            }
-            let slot_info = JsBuffer::from_slice(&mut cx, &slot_info_bytes)?;
-            context.set(&mut cx, "slotInfo", slot_info)?;
-            let context = context.as_value(&mut cx);
-
-            let this = (*inner).clone(&mut cx).into_inner(&mut cx);
-            let val = cb.to_inner(&mut cx).call(&mut cx, this, [context])?;
-            if val.is_a::<JsUndefined, _>(&mut cx) {
-                return Ok(None);
-            }
-            let as_obj = val.downcast_or_throw::<JsObject, _>(&mut cx)?;
-            Ok(Some(as_obj.root(&mut cx)))
-        });
-    }
-
-    fn release_slot(&self, ctx: &dyn SlotReleaseContext<SlotKind = Self::SlotKind>) {
-        let inner = self.inner.clone();
-        let cb = self.release_cb.clone();
-        let permit_data = ctx
-            .permit()
-            .user_data::<BridgePermitData>()
-            .map(|d| d.permit.clone());
-        // Get the slot info as bytes
-        let slot_info_bytes = ctx.info().map(|m| m.encode_to_vec());
-
-        self.channel.send(move |mut cx| {
-            let context = JsObject::new(&mut cx);
-            if let Some(permit_obj) = permit_data {
-                let ph: Handle<JsObject> = permit_obj.to_inner(&mut cx);
-                let pd = ph.get_value(&mut cx, PERMIT_DATA_FIELD)?;
-                context.set(&mut cx, "permit", pd)?;
-            }
-            if let Some(slot_info_bytes) = slot_info_bytes {
-                let slot_info = JsBuffer::from_slice(&mut cx, &slot_info_bytes)?;
-                context.set(&mut cx, "slotInfo", slot_info)?;
-            }
-            let context = context.as_value(&mut cx);
-
-            let this = (*inner).clone(&mut cx).into_inner(&mut cx);
-            let val = cb.to_inner(&mut cx).call(&mut cx, this, [context])?;
-            if val.is_a::<JsUndefined, _>(&mut cx) {
-                return Ok(None);
-            }
-            let as_obj = val.downcast_or_throw::<JsObject, _>(&mut cx)?;
-            Ok(Some(as_obj.root(&mut cx)))
-        });
-    }
-}
-
-impl<SK: SlotKind> SlotSupplierBridge<SK> {
-    fn mk_reserve_ctx<'a, C: Context<'a>>(
-        task_queue: String,
-        worker_identity: String,
-        worker_build_id: String,
-        is_sticky: bool,
-        cx: &mut C,
-    ) -> NeonResult<Handle<'a, JsValue>> {
-        let context = JsObject::new(cx);
-        let slottype = cx.string(match SK::kind() {
-            SlotKindType::Workflow => "workflow",
-            SlotKindType::Activity => "activity",
-            SlotKindType::LocalActivity => "local-activity",
-            SlotKindType::Nexus => "nexus",
-        });
-        context.set(cx, "slotType", slottype)?;
-        let tq = cx.string(task_queue);
-        context.set(cx, "taskQueue", tq)?;
-        let wid = cx.string(worker_identity);
-        context.set(cx, "workerIdentity", wid)?;
-        let bid = cx.string(worker_build_id);
-        context.set(cx, "workerBuildId", bid)?;
-        let is_sticky = cx.boolean(is_sticky);
-        context.set(cx, "isSticky", is_sticky)?;
-        let context = context.as_value(cx);
-        Ok(context)
-    }
-}
diff --git a/packages/core-bridge/src/ephemeral_server.rs b/packages/core-bridge/src/ephemeral_server.rs
new file mode 100644
index 000000000..5a86abee5
--- /dev/null
+++ b/packages/core-bridge/src/ephemeral_server.rs
@@ -0,0 +1,251 @@
+use std::{process::Stdio, sync::Arc};
+
+use anyhow::Context as _;
+use neon::prelude::*;
+
+use temporal_sdk_core::ephemeral_server::{
+    EphemeralServer as CoreEphemeralServer, TemporalDevServerConfig as CoreTemporalDevServerConfig,
+    TestServerConfig as CoreTestServerConfig,
+};
+
+use bridge_macros::js_function;
+use temporal_sdk_core::CoreRuntime;
+
+use crate::helpers::*;
+use crate::runtime::{Runtime, RuntimeExt as _};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub struct EphemeralServer {
+    core_runtime: Arc<CoreRuntime>,
+    core_server: CoreEphemeralServer,
+}
+
+impl Finalize for EphemeralServer {}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub fn init(cx: &mut neon::prelude::ModuleContext) -> neon::prelude::NeonResult<()> {
+    cx.export_function("startEphemeralServer", start_ephemeral_server)?;
+    cx.export_function("getEphemeralServerTarget", get_ephemeral_server_target)?;
+    cx.export_function("shutdownEphemeralServer", shutdown_ephemeral_server)?;
+
+    Ok(())
+}
+
+/// start an ephemeral temporal server
+#[js_function]
+pub fn start_ephemeral_server(
+    runtime: OpaqueInboundHandle<Runtime>,
+    config: config::EphemeralServerConfig,
+) -> BridgeResult<BridgeFuture<OpaqueOutboundHandle<EphemeralServer>>> {
+    let runtime = runtime.borrow_inner()?.core_runtime.clone();
+    let config: CoreEphemeralServerConfig = config.try_into()?;
+
+    runtime.clone().future_to_promise(async move {
+        // Node intentionally drops stdout/stderr on process fork for security reasons,
+        // which is causing various issues with ephemeral servers. To work around that
+        // behavior, we explicitly force stdout/stderr on the child process.
+        let stdout = Stdio::from(std::io::stdout());
+        let stderr = Stdio::from(std::io::stderr());
+
+        let core_server = config
+            .start_server(stdout, stderr)
+            .await
+            .context("Failed to start ephemeral server")?;
+
+        Ok(OpaqueOutboundHandle::new(EphemeralServer {
+            core_runtime: runtime,
+            core_server,
+        }))
+    })
+}
+
+/// get the ephemeral server "target" (address:port string)
+#[js_function]
+pub fn get_ephemeral_server_target(
+    server: OpaqueInboundHandle<EphemeralServer>,
+) -> BridgeResult<String> {
+    Ok(server.borrow_inner()?.core_server.target.clone())
+}
+
+/// shutdown an ephemeral server - consumes the server
+#[js_function]
+pub fn shutdown_ephemeral_server(
+    server: OpaqueInboundHandle<EphemeralServer>,
+) -> BridgeResult<BridgeFuture<()>> {
+    let mut server = server.take_inner()?;
+    let runtime = server.core_runtime;
+
+    runtime.future_to_promise(async move {
+        server
+            .core_server
+            .shutdown()
+            .await
+            .context("Failed to shutdown ephemeral server")?;
+        Ok(())
+    })
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+enum CoreEphemeralServerConfig {
+    TimeSkipping(CoreTestServerConfig),
+    DevServer(CoreTemporalDevServerConfig),
+}
+
+impl CoreEphemeralServerConfig {
+    async fn start_server(
+        self,
+        stdout: Stdio,
+        stderr: Stdio,
+    ) -> anyhow::Result<CoreEphemeralServer> {
+        match self {
+            Self::TimeSkipping(config) => config.start_server_with_output(stdout, stderr).await,
+            Self::DevServer(config) => config.start_server_with_output(stdout, stderr).await,
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+mod config {
+    use std::time::Duration;
+
+    use anyhow::Context as _;
+
+    use temporal_sdk_core::ephemeral_server::{
+        EphemeralExe, EphemeralExeVersion, TemporalDevServerConfig as CoreTemporalDevServerConfig,
+        TemporalDevServerConfigBuilder, TestServerConfig as CoreTestServerConfig,
+        TestServerConfigBuilder,
+    };
+
+    use bridge_macros::TryFromJs;
+
+    use crate::helpers::BridgeError;
+
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) enum EphemeralServerConfig {
+        TimeSkipping(TimeSkippingServerConfig),
+        DevServer(DevServerConfig),
+    }
+
+    impl TryInto<super::CoreEphemeralServerConfig> for EphemeralServerConfig {
+        type Error = BridgeError;
+
+        fn try_into(self) -> Result<super::CoreEphemeralServerConfig, Self::Error> {
+            match self {
+                Self::TimeSkipping(config) => Ok(super::CoreEphemeralServerConfig::TimeSkipping(
+                    config.try_into()?,
+                )),
+                Self::DevServer(config) => Ok(super::CoreEphemeralServerConfig::DevServer(
+                    config.try_into()?,
+                )),
+            }
+        }
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) struct TimeSkippingServerConfig {
+        executable: EphemeralServerExecutableConfig,
+        port: Option<u16>,
+        extra_args: Vec<String>,
+    }
+
+    impl TryInto<CoreTestServerConfig> for TimeSkippingServerConfig {
+        type Error = BridgeError;
+
+        fn try_into(self) -> Result<CoreTestServerConfig, Self::Error> {
+            let mut config = TestServerConfigBuilder::default();
+            let config = config
+                .exe(self.executable.try_into()?)
+                .port(self.port)
+                .extra_args(self.extra_args)
+                .build()
+                .context("Bulding Test Server config")?;
+
+            Ok(config)
+        }
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) struct DevServerConfig {
+        executable: EphemeralServerExecutableConfig,
+        ip: String,
+        port: Option<u16>,
+        ui: bool,
+        ui_port: Option<u16>,
+        namespace: String,
+        db_filename: Option<String>,
+        log: DevServerLogConfig,
+        extra_args: Vec<String>,
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) struct DevServerLogConfig {
+        format: String,
+        level: String,
+    }
+
+    impl TryInto<CoreTemporalDevServerConfig> for DevServerConfig {
+        type Error = BridgeError;
+
+        fn try_into(self) -> Result<CoreTemporalDevServerConfig, Self::Error> {
+            let mut config = TemporalDevServerConfigBuilder::default();
+            let config = config
+                .exe(self.executable.try_into()?)
+                .ip(self.ip)
+                .port(self.port)
+                .ui(self.ui)
+                .ui_port(self.ui_port)
+                .namespace(self.namespace)
+                .db_filename(self.db_filename)
+                .log((self.log.format, self.log.level))
+                .extra_args(self.extra_args)
+                .build()
+                .context("Bulding Dev Server config")?;
+
+            Ok(config)
+        }
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    enum EphemeralServerExecutableConfig {
+        CachedDownload(CachedDownloadExecutable),
+        ExistingPath(ExistingPathExecutable),
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    struct CachedDownloadExecutable {
+        download_dir: Option<String>,
+        version: String,
+        ttl: Duration,
+        sdk_version: String,
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    struct ExistingPathExecutable {
+        path: String,
+    }
+
+    impl TryInto<EphemeralExe> for EphemeralServerExecutableConfig {
+        type Error = BridgeError;
+
+        fn try_into(self) -> Result<EphemeralExe, Self::Error> {
+            match self {
+                Self::CachedDownload(config) => Ok(EphemeralExe::CachedDownload {
+                    version: match config.version.as_str() {
+                        "default" => EphemeralExeVersion::SDKDefault {
+                            sdk_name: "sdk-typescript".to_owned(),
+                            sdk_version: config.sdk_version,
+                        },
+                        _ => EphemeralExeVersion::Fixed(config.version),
+                    },
+                    dest_dir: config.download_dir,
+                    ttl: Some(config.ttl),
+                }),
+                Self::ExistingPath(config) => Ok(EphemeralExe::ExistingPath(config.path)),
+            }
+        }
+    }
+}
diff --git a/packages/core-bridge/src/errors.rs b/packages/core-bridge/src/errors.rs
deleted file mode 100644
index e92318531..000000000
--- a/packages/core-bridge/src/errors.rs
+++ /dev/null
@@ -1,38 +0,0 @@
-use neon::prelude::*;
-
-/// An unhandled error while communicating with the server, considered fatal
-pub static TRANSPORT_ERROR: &str = "TransportError";
-/// Thrown after shutdown was requested as a response to a poll function, JS should stop polling
-/// once this error is encountered
-pub static SHUTDOWN_ERROR: &str = "ShutdownError";
-/// Something unexpected happened, considered fatal
-pub static UNEXPECTED_ERROR: &str = "UnexpectedError";
-/// Used in different parts of the project to signal that something unexpected has happened
-pub static ILLEGAL_STATE_ERROR: &str = "IllegalStateError";
-
-pub fn make_named_error_from_string<'a, C>(
-    cx: &mut C,
-    name: &str,
-    message: impl Into<String>,
-) -> JsResult<'a, JsError>
-where
-    C: Context<'a>,
-{
-    let error = cx.error(message.into()).unwrap();
-    let name = cx.string(name);
-    error.set(cx, "name", name)?;
-
-    Ok(error)
-}
-
-pub fn make_named_error_from_error<'a, C, E>(
-    cx: &mut C,
-    name: &str,
-    err: E,
-) -> JsResult<'a, JsError>
-where
-    C: Context<'a>,
-    E: std::error::Error,
-{
-    make_named_error_from_string(cx, name, format!("{:?}", err))
-}
diff --git a/packages/core-bridge/src/helpers.rs b/packages/core-bridge/src/helpers.rs
deleted file mode 100644
index 4054c013c..000000000
--- a/packages/core-bridge/src/helpers.rs
+++ /dev/null
@@ -1,297 +0,0 @@
-use crate::errors::*;
-use neon::{prelude::*, types::buffer::TypedArray};
-use std::{fmt::Display, future::Future, sync::Arc};
-
-/// Send a result to JS via callback using a [Channel]
-pub fn send_result<F, T>(channel: Arc<Channel>, callback: Root<JsFunction>, res_fn: F)
-where
-    F: for<'a> FnOnce(&mut TaskContext<'a>) -> NeonResult<Handle<'a, T>> + Send + 'static,
-    T: Value,
-{
-    channel.send(move |mut cx| {
-        let callback = callback.into_inner(&mut cx);
-        let this = cx.undefined();
-        let error = cx.undefined();
-        let result = res_fn(&mut cx)?;
-        let args: Vec<Handle<JsValue>> = vec![error.upcast(), result.upcast()];
-        callback.call(&mut cx, this, args)?;
-        Ok(())
-    });
-}
-
-/// Send an error to JS via callback using a [Channel]
-pub fn send_error<E, F>(channel: Arc<Channel>, callback: Root<JsFunction>, error_ctor: F)
-where
-    E: Object,
-    F: for<'a> FnOnce(&mut TaskContext<'a>) -> JsResult<'a, E> + Send + 'static,
-{
-    channel.send(move |mut cx| {
-        let callback = callback.into_inner(&mut cx);
-        callback_with_error(&mut cx, callback, error_ctor)
-    });
-}
-
-/// Call `callback` with given error
-pub fn callback_with_error<'a, C, E, F>(
-    cx: &mut C,
-    callback: Handle<JsFunction>,
-    error_ctor: F,
-) -> NeonResult<()>
-where
-    C: Context<'a>,
-    E: Object,
-    F: FnOnce(&mut C) -> JsResult<'a, E> + Send + 'static,
-{
-    let this = cx.undefined();
-    let error = error_ctor(cx)?;
-    let result = cx.undefined();
-    let args: Vec<Handle<JsValue>> = vec![error.upcast(), result.upcast()];
-    callback.call(cx, this, args)?;
-    Ok(())
-}
-
-/// Call `callback` with an UnexpectedError created from `err`
-pub fn callback_with_unexpected_error<'a, C, E>(
-    cx: &mut C,
-    callback: Handle<JsFunction>,
-    err: E,
-) -> NeonResult<()>
-where
-    C: Context<'a>,
-    E: Display,
-{
-    let err_str = format!("{}", err);
-    callback_with_error(cx, callback, move |cx| {
-        make_named_error_from_string(cx, UNEXPECTED_ERROR, err_str)
-    })
-}
-
-/// When Future completes, call given JS callback using a neon::Channel with either error or
-/// undefined
-pub async fn void_future_to_js<E, F, ER, EF>(
-    channel: Arc<Channel>,
-    callback: Root<JsFunction>,
-    f: F,
-    error_function: EF,
-) where
-    E: Display + Send + 'static,
-    F: Future<Output = Result<(), E>> + Send,
-    ER: Object,
-    EF: for<'a> FnOnce(&mut TaskContext<'a>, E) -> JsResult<'a, ER> + Send + 'static,
-{
-    match f.await {
-        Ok(()) => {
-            send_result(channel, callback, |cx| Ok(cx.undefined()));
-        }
-        Err(err) => {
-            send_error(channel, callback, |cx| error_function(cx, err));
-        }
-    }
-}
-
-macro_rules! js_optional_getter {
-    ($js_cx:expr, $js_obj:expr, $prop_name:expr, $js_type:ty) => {
-        match get_optional($js_cx, $js_obj, $prop_name) {
-            None => None,
-            Some(val) => {
-                if val.is_a::<$js_type, _>($js_cx) {
-                    Some(val.downcast_or_throw::<$js_type, _>($js_cx)?)
-                } else {
-                    Some($js_cx.throw_type_error(format!("Invalid {}", $prop_name))?)
-                }
-            }
-        }
-    };
-}
-
-pub(crate) use js_optional_getter;
-
-macro_rules! js_getter {
-    ($js_cx:expr, $js_obj:expr, $prop_name:expr, $js_type:ty) => {
-        match get_optional($js_cx, $js_obj, $prop_name) {
-            None => $js_cx.throw_type_error(format!("{} must be defined", $prop_name))?,
-            Some(val) => {
-                if val.is_a::<$js_type, _>($js_cx) {
-                    val.downcast_or_throw::<$js_type, _>($js_cx)?
-                } else {
-                    $js_cx.throw_type_error(format!("Invalid {}", $prop_name))?
-                }
-            }
-        }
-    };
-}
-
-pub(crate) use js_getter;
-
-macro_rules! js_optional_value_getter {
-    ($js_cx:expr, $js_obj:expr, $prop_name:expr, $js_type:ty) => {
-        js_optional_getter!($js_cx, $js_obj, $prop_name, $js_type).map(|v| v.value($js_cx))
-    };
-}
-
-pub(crate) use js_optional_value_getter;
-
-macro_rules! js_value_getter {
-    ($js_cx:expr, $js_obj:expr, $prop_name:expr, $js_type:ty) => {
-        match js_optional_getter!($js_cx, $js_obj, $prop_name, $js_type) {
-            Some(val) => val.value($js_cx),
-            None => $js_cx.throw_type_error(format!("{} must be defined", $prop_name))?,
-        }
-    };
-}
-
-pub(crate) use js_value_getter;
-
-/// Helper for extracting an optional attribute from [obj].
-/// If [obj].[attr] is undefined or not present, None is returned
-pub fn get_optional<'a, C, K>(
-    cx: &mut C,
-    obj: &Handle<JsObject>,
-    attr: K,
-) -> Option<Handle<'a, JsValue>>
-where
-    K: neon::object::PropertyKey,
-    C: Context<'a>,
-{
-    match obj.get_value(cx, attr) {
-        Err(_) => None,
-        Ok(val) => match val.is_a::<JsUndefined, _>(cx) {
-            true => None,
-            false => Some(val),
-        },
-    }
-}
-
-/// Helper for extracting a Vec<u8> from optional Buffer at [obj].[attr]
-pub fn get_optional_vec<'a, C, K>(
-    cx: &mut C,
-    obj: &Handle<JsObject>,
-    attr: K,
-) -> Result<Option<Vec<u8>>, neon::result::Throw>
-where
-    K: neon::object::PropertyKey + Display + Clone,
-    C: Context<'a>,
-{
-    if let Some(val) = get_optional(cx, obj, attr.clone()) {
-        let buf = val.downcast::<JsBuffer, C>(cx).map_err(|_| {
-            cx.throw_type_error::<_, Option<Vec<u8>>>(format!("Invalid {}", attr))
-                .unwrap_err()
-        })?;
-        Ok(Some(buf.as_slice(cx).to_vec()))
-    } else {
-        Ok(None)
-    }
-}
-
-/// Helper for extracting a Vec<u8> from optional Buffer at [obj].[attr]
-pub fn get_vec<'a, C, K>(
-    cx: &mut C,
-    obj: &Handle<JsObject>,
-    attr: K,
-    full_attr_path: &str,
-) -> Result<Vec<u8>, neon::result::Throw>
-where
-    K: neon::object::PropertyKey + Display + Clone,
-    C: Context<'a>,
-{
-    if let Some(val) = get_optional(cx, obj, attr.clone()) {
-        let buf = val.downcast::<JsBuffer, C>(cx).map_err(|_| {
-            cx.throw_type_error::<_, Option<Vec<u8>>>(format!("Invalid {}", attr))
-                .unwrap_err()
-        })?;
-        Ok(buf.as_slice(cx).to_vec())
-    } else {
-        cx.throw_type_error::<_, Vec<u8>>(format!("Invalid or missing {}", full_attr_path))
-    }
-}
-
-// Recursively convert a Serde value to a JS value
-pub fn serde_value_to_js_value<'a>(
-    cx: &mut impl Context<'a>,
-    val: serde_json::Value,
-) -> JsResult<'a, JsValue> {
-    match val {
-        serde_json::Value::String(s) => Ok(cx.string(s).upcast()),
-        serde_json::Value::Number(n) => Ok(cx.number(n.as_f64().unwrap()).upcast()),
-        serde_json::Value::Bool(b) => Ok(cx.boolean(b).upcast()),
-        serde_json::Value::Null => Ok(cx.null().upcast()),
-        serde_json::Value::Array(vec) => {
-            let arr: Handle<'a, JsArray> = JsArray::new(cx, vec.len());
-            for (i, v) in vec.into_iter().enumerate() {
-                let v = serde_value_to_js_value(cx, v)?;
-                arr.set(cx, i as u32, v)?;
-            }
-            Ok(arr.upcast())
-        }
-        serde_json::Value::Object(map) => hashmap_to_js_value(cx, map).map(|v| v.upcast()),
-    }
-}
-
-pub fn hashmap_to_js_value<'a>(
-    cx: &mut impl Context<'a>,
-    map: impl IntoIterator<Item = (String, serde_json::Value)>,
-) -> JsResult<'a, JsObject> {
-    let obj: Handle<'a, JsObject> = cx.empty_object();
-    for (k, v) in map {
-        let k = cx.string(snake_to_camel(k));
-        let v = serde_value_to_js_value(cx, v)?;
-        obj.set(cx, k, v)?;
-    }
-    Ok(obj)
-}
-
-fn snake_to_camel(input: String) -> String {
-    match input.find('_') {
-        None => input,
-        Some(first) => {
-            let mut result = String::with_capacity(input.len());
-            if first > 0 {
-                result.push_str(&input[..first]);
-            }
-            let mut capitalize = true;
-            for c in input[first + 1..].chars() {
-                if c == '_' {
-                    capitalize = true;
-                } else if capitalize {
-                    result.push(c.to_ascii_uppercase());
-                    capitalize = false;
-                } else {
-                    result.push(c.to_ascii_lowercase());
-                }
-            }
-            result
-        }
-    }
-}
-
-#[allow(dead_code)]
-// Useful to help debug JSObject contents
-pub fn log_js_object<'a, 'b, C: Context<'b>>(cx: &mut C, js_object: &Handle<'a, JsObject>) {
-    let global = cx.global_object();
-    let console = global
-        .get::<JsObject, _, _>(cx, "console")
-        .expect("Failed to get console object");
-
-    let log = console
-        .get::<JsFunction, _, _>(cx, "log")
-        .expect("Failed to get log function");
-
-    let args = vec![js_object.upcast()]; // Upcast js_object to JsValue
-    log.call(cx, console, args)
-        .expect("Failed to call console.log");
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn snake_to_camel_works() {
-        assert_eq!(snake_to_camel("this_is_a_test".into()), "thisIsATest");
-        assert_eq!(snake_to_camel("this___IS_a_TEST".into()), "thisIsATest");
-        assert_eq!(
-            snake_to_camel("éàç_this_is_a_test".into()),
-            "éàçThisIsATest"
-        );
-    }
-}
diff --git a/packages/core-bridge/src/helpers/abort_controller.rs b/packages/core-bridge/src/helpers/abort_controller.rs
new file mode 100644
index 000000000..094fa5a10
--- /dev/null
+++ b/packages/core-bridge/src/helpers/abort_controller.rs
@@ -0,0 +1,152 @@
+use std::sync::{Arc, OnceLock};
+
+use neon::{
+    handle::{Handle, Root},
+    object::Object,
+    prelude::{Context, JsResult},
+    types::{JsFunction, JsObject, JsValue},
+};
+
+use super::{BridgeResult, JsCallback, TryIntoJs, errors::IntoThrow as _};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub type JsAbortSignal = JsValue;
+
+/// An object that modelizes a JavaScript `AbortController`, and its corresponding `AbortSignal`,
+/// allowing the Rust side to fire that signal if/when needed, e.g. when dropped from the Rust side.
+///
+/// The JS counterpart objects are lazily intantiated when the signal gets converted to JS; this ensures
+/// that the Rust side can be created without waiting for acquisition of the JS execution lock.
+pub struct AbortController {
+    inner: Arc<AbortControllerInner>,
+    drop_abort_reason: String,
+}
+
+impl AbortController {
+    /// Create a new `AbortController` and `AbortSignal` pair.
+    ///
+    /// The `drop_abort_reason` string will be used as the reason for the abort
+    /// if the controller is dropped from the Rust side.
+    #[must_use]
+    pub fn new(drop_abort_reason: String) -> (Self, AbortSignal) {
+        let inner = AbortControllerInner {
+            js_counterpart: OnceLock::new(),
+            aborted: OnceLock::new(),
+        };
+        let inner = Arc::new(inner);
+        (
+            Self {
+                inner: inner.clone(),
+                drop_abort_reason,
+            },
+            AbortSignal { inner },
+        )
+    }
+
+    pub fn abort(&self, reason: impl Into<String>) {
+        self.inner.abort(reason);
+    }
+}
+
+impl Drop for AbortController {
+    fn drop(&mut self) {
+        self.abort(self.drop_abort_reason.clone());
+    }
+}
+
+/// An object that models the signal of a JavaScript `AbortController`.
+pub struct AbortSignal {
+    inner: Arc<AbortControllerInner>,
+}
+
+impl TryIntoJs for AbortSignal {
+    type Output = JsAbortSignal;
+
+    fn try_into_js<'cx>(self, cx: &mut impl Context<'cx>) -> JsResult<'cx, JsAbortSignal> {
+        let signal = self.inner.ensure_js_initialized(cx).into_throw(cx)?;
+        Ok(signal)
+    }
+}
+
+/// The inner state of an `AbortController`, shared between the Rust and JS sides.
+struct AbortControllerInner {
+    // The fact that we require a `Context` in `ensure_js_initialized` means that we are running on
+    // the Node's thread, which guarantees that there can't be multiple threads calling into that
+    // function concurrently; that should in theory aleviate the need to use a lock on `js_counterpart`.
+    //
+    // It is however possible for the rust-side controller to get aborted from a non-Node thread
+    // while the JS-side controller is being created on the Node thread, in which case we don't
+    // want the Rust-side thread to get blocked for the JS-side to complete instantiation.
+    //
+    // By modelling the "JS initialization" and "is aborted" states as two distinct independant
+    // structures, we ensure that we're never blocking execution of either thread. This however
+    // means that either step may happen before the other, so we need to be careful not to miss
+    // sending the abort signal. The good news is that nothing bad will happen if we call the JS
+    // abort callback multiple times.
+    js_counterpart: OnceLock<Arc<AbortControllerJsCounterpart>>,
+    aborted: OnceLock<String>,
+}
+
+struct AbortControllerJsCounterpart {
+    signal: Root<JsObject>,
+    abort: JsCallback<(String,), ()>,
+}
+
+impl AbortControllerInner {
+    /// Create the JS `AbortController` if it hasn't been created yet.
+    /// Returns a reference to the signal object that can be passed to JS.
+    fn ensure_js_initialized<'cx, C: Context<'cx>>(
+        &self,
+        cx: &mut C,
+    ) -> BridgeResult<Handle<'cx, JsValue>> {
+        if let Some(js_counterpart) = self.js_counterpart.get() {
+            // Already initialized, return the signal
+            return Ok(js_counterpart.signal.to_inner(cx).upcast());
+        }
+
+        // Not initialized yet, create the JS AbortController
+        let global = cx.global_object();
+        let abort_controller_class = global.get::<JsFunction, _, _>(cx, "AbortController")?;
+
+        let abort_controller = abort_controller_class.construct(cx, [])?;
+        let signal = abort_controller.get::<JsObject, _, _>(cx, "signal")?;
+        let abort_fn = abort_controller.get::<JsFunction, _, _>(cx, "abort")?;
+
+        let abort_cb = JsCallback::new(cx, abort_fn, Some(abort_controller));
+
+        let js_counterpart = Arc::new(AbortControllerJsCounterpart {
+            signal: signal.root(cx),
+            abort: abort_cb,
+        });
+
+        let js_counterpart = match self.js_counterpart.set(js_counterpart.clone()) {
+            Ok(()) => {
+                // If the Rust controller has already been aborted, call the JS abort callback now
+                // VALIDATE: Do we need a memory barrier here to ensure that js_counterpart and aborted are coherent?
+                //           I assume that the get() call ensures visibility of the js_counterpart
+                if let Some(aborted) = self.aborted.get() {
+                    // Fire and forget
+                    let _ = js_counterpart.abort.call_on_js_thread((aborted.clone(),));
+                }
+                js_counterpart
+            }
+            Err(js_counterpart) => js_counterpart,
+        };
+
+        Ok(js_counterpart.signal.to_inner(cx).upcast())
+    }
+
+    /// Immediately abort the `AbortController`, causing the JS side `signal` to fire.
+    fn abort(&self, reason: impl Into<String>) {
+        let reason = reason.into();
+        if self.aborted.set(reason.clone()) == Ok(()) {
+            // If we haven't created the JS AbortController yet, there's nothing to abort
+            // VALIDATE: Do we need a memory barrier here to ensure that js_counterpart and aborted are coherent?
+            if let Some(js_counterpart) = self.js_counterpart.get() {
+                // Fire and forget
+                let _ = js_counterpart.abort.call_on_js_thread((reason,));
+            }
+        }
+    }
+}
diff --git a/packages/core-bridge/src/helpers/callbacks.rs b/packages/core-bridge/src/helpers/callbacks.rs
new file mode 100644
index 000000000..c67b73756
--- /dev/null
+++ b/packages/core-bridge/src/helpers/callbacks.rs
@@ -0,0 +1,300 @@
+use std::{marker::PhantomData, sync::Arc};
+
+use neon::{
+    event::Channel,
+    handle::{Handle, Root},
+    object::Object,
+    prelude::Context,
+    types::{JsFunction, JsFuture, JsObject, JsPromise, JsValue, Value as _},
+};
+
+use super::{BridgeError, BridgeResult, TryFromJs, TryIntoJs, errors::IntoThrow as _};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// A callback is a JS function that is meant to be called by the Rust side.
+/// A `JsCallback` is a callback that returns a value synchronously.
+///
+/// Note that at this level, a callback is a pure function, not a method on an object;
+/// that is, the callback will be called with `this` set to `undefined`. If the JS side
+/// API presents the callback as a method on some object, then the function should be
+/// `bind(this)`'d on the JS side before passing it to the Rust side.
+#[derive(Debug)]
+pub struct JsCallback<Args, Ret>
+where
+    Args: TryIntoJsArgs + Send + Sync,
+    Ret: TryFromJs + Send + Sync,
+{
+    inner: Arc<CallbackInner<Args, Ret>>,
+}
+
+impl<Args, Ret> Clone for JsCallback<Args, Ret>
+where
+    Args: TryIntoJsArgs + Send + Sync,
+    Ret: TryFromJs + Send + Sync,
+{
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
+        }
+    }
+}
+
+impl<Args, Ret> JsCallback<Args, Ret>
+where
+    Args: TryIntoJsArgs + Send + Sync + 'static,
+    Ret: TryFromJs + Send + Sync + 'static,
+{
+    pub fn new<'cx, C: Context<'cx>>(
+        cx: &mut C,
+        func: Handle<JsFunction>,
+        this: Option<Handle<JsObject>>,
+    ) -> Self {
+        Self {
+            inner: Arc::new(CallbackInner {
+                this: this.map(|t| t.root(cx)),
+                func: func.root(cx),
+                func_name: func
+                    .to_string(cx)
+                    .map_or_else(|_| "anonymous func".to_owned(), |s| s.value(cx)),
+                chan: cx.channel(),
+                _marker: PhantomData,
+            }),
+        }
+    }
+
+    /// Call the callback on the JS thread and return a handle to the result.
+    pub fn call_on_js_thread(&self, args: Args) -> BridgeResult<neon::event::JoinHandle<Ret>> {
+        let inner = self.inner.clone();
+
+        let ret = inner
+            .chan
+            .clone()
+            .try_send(move |mut cx| inner.call(&mut cx, args).into_throw(&mut cx))
+            .map_err(|e| BridgeError::Other(e.into()))?;
+
+        Ok(ret)
+    }
+
+    pub fn call_and_block(&self, args: Args) -> BridgeResult<Ret> {
+        let join_handle = self.call_on_js_thread(args)?;
+
+        // This is... unfortunate but since this method is called from an async context way up
+        // the stack, but is not async itself AND we need some way to get the result from the JS
+        // callback, we must use this roundabout way of blocking. Simply calling `join` on the
+        // channel send won't work - it'll panic because it calls block_on internally.
+        let callback_res = futures::executor::block_on(join_handle);
+
+        match callback_res {
+            Ok(x) => Ok(x),
+            Err(e) => Err(BridgeError::Other(e.into())),
+        }
+    }
+}
+
+/// Unfortunately, the `TryFromJS` trait doesn't have access to the containing object, and therefore
+/// can't preserve the `this` context. If the JS side API presents the callback as a method on some
+/// object, then the function should be `bind(this)`'d on the JS side before passing it to Rust.
+impl<Args, Ret> TryFromJs for JsCallback<Args, Ret>
+where
+    Args: TryIntoJsArgs + Send + Sync + 'static,
+    Ret: TryFromJs + Send + Sync + 'static,
+{
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        let func = js_value.downcast::<JsFunction, _>(cx)?;
+        Ok(Self::new(cx, func, None))
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub struct JsAsyncCallback<Args, Ret>
+where
+    Args: TryIntoJsArgs + Send + Sync,
+    Ret: TryFromJs + Send + Sync + 'static,
+{
+    inner: Arc<CallbackInner<Args, JsFuture<BridgeResult<Ret>>>>,
+}
+
+impl<Args, Ret> JsAsyncCallback<Args, Ret>
+where
+    Args: TryIntoJsArgs + Send + Sync + 'static,
+    Ret: TryFromJs + Send + Sync + 'static,
+{
+    pub fn new<'cx, C: Context<'cx>>(
+        cx: &mut C,
+        func: Handle<JsFunction>,
+        this: Option<Handle<JsObject>>,
+    ) -> Self {
+        Self {
+            inner: Arc::new(CallbackInner {
+                this: this.map(|t| t.root(cx)),
+                func: func.root(cx),
+                func_name: func
+                    .to_string(cx)
+                    .map_or_else(|_| "anonymous func".to_owned(), |s| s.value(cx)),
+                chan: cx.channel(),
+                _marker: PhantomData,
+            }),
+        }
+    }
+
+    pub async fn call(&self, args: Args) -> BridgeResult<Ret> {
+        let inner = self.inner.clone();
+
+        let join_handle = inner
+            .chan
+            .clone()
+            .try_send(move |mut cx| inner.call(&mut cx, args).into_throw(&mut cx))
+            .map_err(|e| BridgeError::Other(e.into()))?;
+
+        // Wait for the JS function to return a Promise...
+        let res = join_handle.await;
+        let fut = res.map_err(|e| BridgeError::Other(e.into()))?;
+
+        // ... and then wait for the Promise to resolve
+        let res = fut.await;
+        let res = res.map_err(|e| BridgeError::Other(e.into()))??;
+        Ok(res)
+    }
+}
+
+/// Unfortunately, the `TryFromJS` trait doesn't have access to the containing object, and therefore
+/// can't preserve the `this` context. If the JS side API presents the callback as a method on some
+/// object, then the function should be `bind(this)`'d on the JS side before passing it to Rust.
+impl<Args, Ret> TryFromJs for JsAsyncCallback<Args, Ret>
+where
+    Args: TryIntoJsArgs + Send + Sync + 'static,
+    Ret: TryFromJs + Send + Sync + 'static,
+{
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        let func = js_value.downcast::<JsFunction, _>(cx)?;
+        Ok(Self::new(cx, func, None))
+    }
+}
+
+impl<R: TryFromJs + Send + Sync + 'static> TryFromJs for JsFuture<BridgeResult<R>> {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        let prom = js_value.downcast::<JsPromise, _>(cx)?;
+        let fut = prom.to_future(cx, |mut cx, result| match result {
+            // to_future() expects a function that throws a JS ,
+            Ok(value) => {
+                // Promise resolved, but there might still be an error trying to
+                // convert the promise's returned value to the desired type.
+                let val = R::try_from_js(&mut cx, value);
+                match val {
+                    Ok(val) => Ok(Ok(val)),
+                    Err(e) => Ok(Err(e)),
+                }
+            }
+            Err(e) => {
+                // Promise failed to resolve
+                let err_str = e.to_string(&mut cx)?.value(&mut cx);
+                Ok(Err(BridgeError::UnexpectedError(err_str)))
+            }
+        })?;
+
+        Ok(fut)
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+#[derive(Debug)]
+struct CallbackInner<Args, Ret>
+where
+    Args: TryIntoJsArgs + Send + Sync,
+    Ret: TryFromJs + Send + Sync,
+{
+    this: Option<Root<JsObject>>,
+    func: Root<JsFunction>,
+    func_name: String,
+    chan: Channel,
+    _marker: PhantomData<(Args, Ret)>,
+}
+
+impl<Args: TryIntoJsArgs + Send + Sync, Ret: TryFromJs + Send + Sync> CallbackInner<Args, Ret> {
+    fn call<'a, C: Context<'a>>(&self, cx: &mut C, args: Args) -> BridgeResult<Ret> {
+        let this: Handle<'a, JsValue> = self
+            .this
+            .as_ref()
+            .map_or(cx.undefined().upcast(), |t| t.to_inner(cx).upcast());
+
+        // Convert the arguments to a JS array using the new trait
+        let js_args = args.try_into_js_args(cx)?;
+
+        // Call the function with the JS arguments directly
+        let ret = cx
+            .try_catch(|cx| self.func.to_inner(cx).call(cx, this, js_args))
+            .map_err(|e| {
+                let err_str = format!(
+                    "Error calling JS callback '{}' on JS thread, {:?}",
+                    self.func_name, e
+                );
+                log::info!("{err_str}");
+                BridgeError::UnexpectedError(err_str)
+            })?;
+
+        <Ret>::try_from_js(cx, ret)
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// A trait to build an arguments array for a JS function call from a tuple.
+pub trait TryIntoJsArgs {
+    fn try_into_js_args<'cx, 'a>(
+        self,
+        cx: &mut impl Context<'cx>,
+    ) -> BridgeResult<Vec<Handle<'a, JsValue>>>
+    where
+        'cx: 'a;
+}
+
+impl TryIntoJsArgs for () {
+    fn try_into_js_args<'cx, 'a>(
+        self,
+        _cx: &mut impl Context<'cx>,
+    ) -> BridgeResult<Vec<Handle<'a, JsValue>>>
+    where
+        'cx: 'a,
+    {
+        Ok(Vec::new())
+    }
+}
+
+impl<T0: TryIntoJs> TryIntoJsArgs for (T0,) {
+    fn try_into_js_args<'cx, 'a>(
+        self,
+        cx: &mut impl Context<'cx>,
+    ) -> BridgeResult<Vec<Handle<'a, JsValue>>>
+    where
+        'cx: 'a,
+    {
+        let js_value = self.0.try_into_js(cx)?;
+        Ok(vec![js_value.upcast()])
+    }
+}
+
+impl<T0: TryIntoJs, T1: TryIntoJs> TryIntoJsArgs for (T0, T1) {
+    fn try_into_js_args<'cx, 'a>(
+        self,
+        cx: &mut impl Context<'cx>,
+    ) -> BridgeResult<Vec<Handle<'a, JsValue>>>
+    where
+        'cx: 'a,
+    {
+        let v0 = self.0.try_into_js(cx)?;
+        let v1 = self.1.try_into_js(cx)?;
+        Ok(vec![v0.upcast(), v1.upcast()])
+    }
+}
diff --git a/packages/core-bridge/src/helpers/errors.rs b/packages/core-bridge/src/helpers/errors.rs
new file mode 100644
index 000000000..327f13eb9
--- /dev/null
+++ b/packages/core-bridge/src/helpers/errors.rs
@@ -0,0 +1,294 @@
+use std::cell::RefCell;
+
+use anyhow::Error as AnyhowError;
+use neon::{handle::DowncastError, prelude::*, result::Throw};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// A specialized Result type for errors that can be rethrown as a JS error.
+pub type BridgeResult<T> = Result<T, BridgeError>;
+
+/// Errors that can be rethrown by the Bridge as JS errors.
+#[derive(Debug, thiserror::Error)]
+#[allow(clippy::option_if_let_else)]
+pub enum BridgeError {
+    /// General error related to conversion between JS and Rust types.
+    ///
+    /// Use `BridgeResult::field()` to prepend a field name to the error while
+    /// while propagating the error up through call stack.
+    ///
+    /// Becomes a JS `TypeError`.
+    #[error("{}{message}", field_prefix(.field))]
+    TypeError {
+        field: Option<String>,
+        message: String,
+    },
+
+    /// A specific variant of type errors that indicates that a JS provided object
+    /// that is expected to be an enum variant carries an invalid `type` value.
+    ///
+    /// Use `BridgeResult::field()` to prepend a field name to the error while
+    /// while propagating the error up through call stack. Doing so will implicitly
+    /// convert the error into the more generic `TypeError` variant.
+    ///
+    /// Becomes a JS `TypeError`.
+    #[error("Invalid variant '{variant}' for enum {enum_name}")]
+    InvalidVariant { enum_name: String, variant: String },
+
+    /// Error when a transport error occurs.
+    ///
+    /// Becomes a JS `TransportError`.
+    #[error("{0}")]
+    TransportError(String),
+
+    /// Error when a resource is still in use while it shouldn't be.
+    ///
+    /// Becomes a JS `IllegalStateError`.
+    #[error("{what} still in use{}", details_suffix(.details))]
+    IllegalStateStillInUse {
+        what: &'static str,
+        details: Option<String>,
+    },
+
+    /// Error when a resource is already closed while it shouldn't be.
+    ///
+    /// Becomes a JS `IllegalStateError`.
+    #[error("{what} already closed")]
+    IllegalStateAlreadyClosed { what: &'static str },
+
+    /// Something unexpected happened, considered fatal.
+    ///
+    /// Becomes a JS `UnexpectedError`.
+    #[error("Unexpected error: {0}")]
+    UnexpectedError(String),
+
+    /// An error used to inform the JS side that a worker has completed draining
+    /// pending tasks of a certain type. This is really just a poison pill, not
+    /// an actual error.
+    ///
+    /// Becomes a JS `ShutdownError`.
+    #[error("Worker has been shutdown")]
+    WorkerShutdown,
+
+    /// Generic wrapper for other errors.
+    ///
+    /// Becomes a JS `Error`.
+    #[error(transparent)]
+    Other(#[from] AnyhowError),
+
+    /// Wrapper for errors that have already been _thrown_ from the JS context.  This requires
+    /// special handling because while a JavaScript thread is throwing, its context cannot be used;
+    /// doing so would result in a panic.  That notably means that we cannot use `cx.throw_error` to
+    /// throw a different error at that point.
+    ///
+    /// Though this case is technically unavoidable due to most Neon's APIs returning either
+    /// `NeonResult` or `JsResult`, and is better than just panicking from `.unwrap()` those, code
+    /// should strive as much as possible to detect potential errors in a way that will not result
+    /// in a JS exception being thrown.
+    ///
+    /// Unfortunately, it is not possible to extract the message or the type of the thrown error, so
+    /// this error will always have a message of "Error thrown from JS".
+    #[error("Error thrown from JS")]
+    JsThrow { thrown: RefCell<Option<ThrowBox>> },
+}
+
+// Append Field Context ////////////////////////////////////////////////////////////////////////////
+
+pub trait AppendFieldContext {
+    /// Add context to a `TypeError` by prepending a field name.
+    ///
+    /// This is useful when converting from JS to Rust types, where the field name is known and can
+    /// be added to the error message to guide the user in the right direction. It is expected that
+    /// field name context will be provided on `BridgeResult` _after_ the conversion that may fail,
+    /// while propagating the error through the `BridgeResult` chain, hence the fact that fields
+    /// are _prepended_, not _appended_.
+    #[must_use]
+    fn field(self, prepend_field: &str) -> Self;
+}
+
+impl<T> AppendFieldContext for BridgeResult<T> {
+    fn field(self, prepend_field: &str) -> Self {
+        match self {
+            Ok(value) => Ok(value),
+            Err(e) => Err(e.field(prepend_field)),
+        }
+    }
+}
+
+impl AppendFieldContext for BridgeError {
+    fn field(self, prepend_field: &str) -> Self {
+        match self {
+            Self::TypeError {
+                field: previous_field,
+                message,
+            } => Self::TypeError {
+                field: match previous_field {
+                    Some(previous_field) => Some(format!("{prepend_field}.{previous_field}")),
+                    None => Some(prepend_field.to_string()),
+                },
+                message,
+            },
+            Self::InvalidVariant { enum_name, variant } => Self::TypeError {
+                field: Some(prepend_field.to_string()),
+                message: format!("Invalid variant '{variant}' for enum {enum_name}"),
+            },
+            e => e,
+        }
+    }
+}
+
+// Conversions from other errors ///////////////////////////////////////////////////////////////////
+
+impl<F: Value, T: Value> From<DowncastError<F, T>> for BridgeError {
+    fn from(error: DowncastError<F, T>) -> Self {
+        Self::TypeError {
+            field: None,
+            message: error.to_string(),
+        }
+    }
+}
+
+// Conversion to/from Throw ////////////////////////////////////////////////////////////////////////
+
+impl From<Throw> for BridgeError {
+    fn from(throw: Throw) -> Self {
+        Self::JsThrow {
+            thrown: RefCell::new(Some(ThrowBox(throw))),
+        }
+    }
+}
+
+pub trait IntoThrow {
+    type Output;
+    fn into_throw<'a, C: Context<'a>>(self, cx: &mut C) -> NeonResult<Self::Output>
+    where
+        Self: Sized;
+}
+
+impl<T> IntoThrow for BridgeResult<T> {
+    type Output = T;
+
+    fn into_throw<'cx, C: Context<'cx>>(self, cx: &mut C) -> NeonResult<Self::Output> {
+        match self {
+            Ok(value) => Ok(value),
+            Err(err) => err.into_throw::<C, Self::Output>(cx),
+        }
+    }
+}
+
+impl BridgeError {
+    fn into_throw<'cx, C: Context<'cx>, T>(self, cx: &mut C) -> NeonResult<T> {
+        match self {
+            Self::TypeError { .. } => cx.throw_type_error(self.to_string()),
+            Self::InvalidVariant { .. } => cx.throw_type_error(self.to_string()),
+
+            Self::TransportError(..) => throw_custom_error(cx, TRANSPORT_ERROR, self.to_string()),
+
+            Self::IllegalStateStillInUse { .. } => {
+                throw_custom_error(cx, ILLEGAL_STATE_ERROR, self.to_string())
+            }
+
+            Self::IllegalStateAlreadyClosed { .. } => {
+                throw_custom_error(cx, ILLEGAL_STATE_ERROR, self.to_string())
+            }
+
+            Self::UnexpectedError(..) => throw_custom_error(cx, UNEXPECTED_ERROR, self.to_string()),
+
+            Self::WorkerShutdown => throw_custom_error(cx, SHUTDOWN_ERROR, self.to_string()),
+
+            Self::Other(e) => {
+                if let Some(thrown) = underlying_js_throw_error(&e) {
+                    // FIXME: Send to logger
+                    eprintln!("Error thrown from JavaScript side: {e:?}");
+                    Err(thrown)
+                } else {
+                    cx.throw_error(format!("{e:#}"))
+                }
+            }
+
+            Self::JsThrow { thrown } => Err(thrown.take().expect("Throw already consumed").0),
+        }
+    }
+}
+
+/// Extracts a `Throw` from an `AnyhowError` chain.
+fn underlying_js_throw_error(error: &AnyhowError) -> Option<Throw> {
+    for cause in error.chain() {
+        if let Some(BridgeError::JsThrow { thrown }) = cause.downcast_ref::<BridgeError>() {
+            return Some(thrown.take().expect("Throw already consumed").0);
+        }
+    }
+    None
+}
+
+/// A wrapper around a `Throw` that implements `Send` and `Sync`. This is necessary because we need
+/// `BridgeError` to be `Send`, but `BridgeError::JsThrow` contains a `Throw`, which isn't `Send`.
+///
+/// We however know for sure that `BridgeError::JsThrow` will never be sent across threads, because
+/// a `Throw`'s lifetime is attached to that of the JS `Context`, which itself isn't `Send`.
+#[repr(transparent)]
+pub struct ThrowBox(Throw);
+
+/// SAFETY: We know for sure that this type will never actually be sent across threads.
+#[allow(clippy::non_send_fields_in_send_ty)]
+unsafe impl Send for ThrowBox {}
+
+/// SAFETY: We know for sure that this type will never actually be sent across threads.
+unsafe impl Sync for ThrowBox {}
+
+impl std::fmt::Debug for ThrowBox {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+// Message formatting utilities ////////////////////////////////////////////////////////////////////
+
+fn field_prefix(field: &Option<String>) -> String {
+    match field {
+        Some(field) => format!("{field}: "),
+        None => String::new(),
+    }
+}
+
+fn details_suffix(details: &Option<String>) -> String {
+    match details {
+        Some(details) => format!(": {details}"),
+        None => String::new(),
+    }
+}
+
+// Custom JavaScript errors ////////////////////////////////////////////////////////////////////////
+
+/// Signals that a requested operation can't be completed because it is illegal given the
+/// current state of the object; e.g. trying to use a resource after it has been closed.
+const ILLEGAL_STATE_ERROR: &str = "IllegalStateError";
+
+/// Something unexpected happened, considered fatal
+const UNEXPECTED_ERROR: &str = "UnexpectedError";
+
+/// An unhandled error while communicating with the server, considered fatal
+const TRANSPORT_ERROR: &str = "TransportError";
+
+/// Thrown after shutdown was requested as a response to a poll function, JS should stop polling
+const SHUTDOWN_ERROR: &str = "ShutdownError";
+
+/// Instantiate and throw a custom JS Error object with a given name and message.
+///
+/// Note that this do not actually instantiate the proper JS classes, as those
+/// are not accessible from here (i.e. they are not exposed as globals). Instead,
+/// we simply override the `name` property of the error object; the bridge adds
+/// a JS-side wrapper around native calls that will look at the `name` property
+/// of every thrown errors, and replace them by proper instances of the custom
+/// Error classes if appropriate. Refer to `core-bridge/ts/errors.ts`.
+fn throw_custom_error<'cx, C: Context<'cx>, S: AsRef<str>, T>(
+    cx: &mut C,
+    name: &str,
+    message: S,
+) -> NeonResult<T> {
+    let error = cx.error(message)?;
+    let name = cx.string(name);
+    error.set(cx, "name", name)?;
+
+    cx.throw(error)
+}
diff --git a/packages/core-bridge/src/helpers/future.rs b/packages/core-bridge/src/helpers/future.rs
new file mode 100644
index 000000000..8c128fdf0
--- /dev/null
+++ b/packages/core-bridge/src/helpers/future.rs
@@ -0,0 +1,45 @@
+use std::pin::Pin;
+
+use neon::{prelude::Context, result::JsResult, types::JsPromise};
+
+use crate::helpers::{BridgeError, IntoThrow, TryIntoJs};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub struct BridgeFuture<R: TryIntoJs + Send + 'static> {
+    future: Pin<Box<dyn Future<Output = Result<R, BridgeError>> + Send + 'static>>,
+    tokio_handle: tokio::runtime::Handle,
+}
+
+impl<R: TryIntoJs + Send + 'static> BridgeFuture<R> {
+    #[must_use]
+    pub fn new(
+        future: Pin<Box<dyn Future<Output = Result<R, BridgeError>> + Send + 'static>>,
+    ) -> Self {
+        Self {
+            future,
+            tokio_handle: tokio::runtime::Handle::current(),
+        }
+    }
+}
+
+impl<R: TryIntoJs + Send + 'static> TryIntoJs for BridgeFuture<R> {
+    type Output = JsPromise;
+
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsPromise> {
+        let cx_channel = cx.channel();
+        let (deferred, promise) = cx.promise();
+
+        self.tokio_handle.spawn(async move {
+            let result = self.future.await;
+            let send_result = deferred.try_settle_with(&cx_channel, move |mut cx| {
+                result.into_throw(&mut cx)?.try_into_js(&mut cx)
+            });
+            if let Err(err) = send_result {
+                eprint!("Failed to complete JS Promise: {err:?}");
+            }
+        });
+
+        Ok(promise)
+    }
+}
diff --git a/packages/core-bridge/src/helpers/handles.rs b/packages/core-bridge/src/helpers/handles.rs
new file mode 100644
index 000000000..554e99bcd
--- /dev/null
+++ b/packages/core-bridge/src/helpers/handles.rs
@@ -0,0 +1,106 @@
+use std::{
+    any,
+    cell::{Ref, RefCell},
+    sync::Arc,
+};
+
+use neon::{prelude::*, types::JsBox};
+
+use super::{BridgeError, BridgeResult, TryFromJs, TryIntoJs};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// Opaque Handles are native structures that are sent into the JS side but without exposing
+/// their internal structure; i.e. they are only meant to be passed back to the Rust side
+/// on appropriate API calls.
+///
+/// Due to very different ownership models and usage patterns, and to avoid unnecessary
+/// complexity, Opaque Handles are split into two variants:
+///
+/// - `OpaqueOutboundHandle` - for sending an opaque handle that was just created by the Rust
+///                            side to the JS side (e.g. as the return value of an API call).
+/// - `OpaqueInboundHandle` - for accepting an opaque handle sent from the JS side to the Rust
+///                           side (e.g. as an argument to an API call).
+pub struct OpaqueOutboundHandle<T: Finalize + 'static> {
+    inner: T,
+}
+
+impl<T: Finalize + 'static> OpaqueOutboundHandle<T> {
+    // We late-wrap into Arc<Box<RefCell<>>> so that T can be send across threads without mutex.
+    pub const fn new(inner: T) -> Self {
+        Self { inner }
+    }
+}
+
+impl<T: Finalize + 'static> TryIntoJs for OpaqueOutboundHandle<T> {
+    type Output = JsBox<Arc<RefCell<Option<T>>>>;
+    fn try_into_js<'cx>(self, cx: &mut impl Context<'cx>) -> JsResult<'cx, Self::Output> {
+        Ok(cx.boxed(Arc::new(RefCell::new(Some(self.inner)))))
+    }
+}
+
+/// Opaque Handles are native structures that are sent into the JS side but without exposing
+/// their internal structure; i.e. they are only meant to be passed back to the Rust side
+/// on appropriate API calls.
+///
+/// Due to very different ownership models and usage patterns, and to avoid unnecessary
+/// complexity, Opaque Handles are split into two variants:
+///
+/// - `OpaqueOutboundHandle` - for sending an opaque handle that was just created by the Rust
+///                            side to the JS side (e.g. as the return value of an API call).
+/// - `OpaqueInboundHandle` - for accepting an opaque handle sent from the JS side to the Rust
+///                           side (e.g. as an argument to an API call).
+pub struct OpaqueInboundHandle<T>
+where
+    T: 'static,
+{
+    inner: Arc<RefCell<Option<T>>>,
+}
+
+impl<T> TryFromJs for OpaqueInboundHandle<T>
+where
+    T: 'static,
+{
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        let boxed = js_value.downcast::<JsBox<Arc<RefCell<Option<T>>>>, _>(cx)?;
+        Ok(Self {
+            inner: Arc::clone(&boxed),
+        })
+    }
+}
+
+impl<T: 'static> OpaqueInboundHandle<T> {
+    pub fn borrow_inner(&self) -> BridgeResult<std::cell::Ref<'_, T>> {
+        match Ref::filter_map(self.inner.borrow(), std::option::Option::as_ref) {
+            Ok(inner_ref) => Ok(inner_ref),
+            Err(_guard) => Err(BridgeError::IllegalStateAlreadyClosed {
+                what: any::type_name::<T>()
+                    .rsplit("::")
+                    .next()
+                    .unwrap_or("Resource"),
+            }),
+        }
+    }
+
+    pub fn map_inner<U>(&self, f: impl FnOnce(&T) -> U) -> BridgeResult<U> {
+        Ok(f(&*self.borrow_inner()?))
+    }
+
+    pub fn take_inner(&self) -> BridgeResult<T> {
+        // It is safe to ignore risks of conflicting borrows as OpaqueInbound are only
+        // accessed while holding a Neon Context (indirectly), which itself guarantees
+        // we are running synchronously with the single Node thread.
+        match self.inner.borrow_mut().take() {
+            Some(x) => Ok(x),
+            None => Err(BridgeError::IllegalStateAlreadyClosed {
+                what: any::type_name::<T>()
+                    .rsplit("::")
+                    .next()
+                    .unwrap_or("Resource"),
+            }),
+        }
+    }
+}
diff --git a/packages/core-bridge/src/helpers/inspect.rs b/packages/core-bridge/src/helpers/inspect.rs
new file mode 100644
index 000000000..c76f62b75
--- /dev/null
+++ b/packages/core-bridge/src/helpers/inspect.rs
@@ -0,0 +1,20 @@
+use neon::{context::Context, handle::Handle, prelude::*};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// Print out a JS object to the console.
+///
+/// Literally: `console.log(obj)`.
+pub fn log_js_object<'a, 'b, C: Context<'b>>(
+    cx: &mut C,
+    js_object: &Handle<'a, JsValue>,
+) -> NeonResult<()> {
+    let global = cx.global_object();
+    let console = global.get::<JsObject, _, _>(cx, "console")?;
+    let log = console.get::<JsFunction, _, _>(cx, "log")?;
+    let args = vec![js_object.upcast()]; // Upcast js_object to JsValue
+
+    log.call(cx, console, args)?;
+
+    Ok(())
+}
diff --git a/packages/core-bridge/src/helpers/json_string.rs b/packages/core-bridge/src/helpers/json_string.rs
new file mode 100644
index 000000000..69c7ceed9
--- /dev/null
+++ b/packages/core-bridge/src/helpers/json_string.rs
@@ -0,0 +1,47 @@
+use std::marker::PhantomData;
+
+use neon::{prelude::Context, result::JsResult, types::JsString};
+use serde::Serialize;
+use serde_json;
+
+use super::{BridgeError, TryIntoJs};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// A newtype wrapper for a T serialized as a JSON string.
+///
+/// Creating objects through NAPI is incredibly slow in Node due to the fact that object data
+/// layout is recalculated every time a property is added. So much that, surprisingly, transferring
+/// Rust objects to JS by serializing them to JSON strings then deserializing them back in JS
+/// using `JSON.parse` is on average twice as fast as creating those objects using NAPI calls
+/// (claim from the Neon's author, circa April 2025).
+///
+/// This newtype wrapper allows specifying values that will be serialized to a JSON string
+/// when being transferred to JS using the `TryIntoJs` trait. The JSON serialization happens
+/// on the caller Rust thread, therefore limiting the time spent in the JS thread.
+#[derive(Debug, Clone)]
+pub struct JsonString<T> {
+    json: String,
+    _phantom: PhantomData<T>,
+}
+
+impl<T> JsonString<T>
+where
+    T: Serialize,
+{
+    pub fn try_from_value(value: T) -> Result<Self, BridgeError> {
+        let json = serde_json::to_string(&value)
+            .map_err(|e| BridgeError::Other(anyhow::Error::from(e)))?;
+        Ok(Self {
+            json,
+            _phantom: PhantomData,
+        })
+    }
+}
+
+impl<T> TryIntoJs for JsonString<T> {
+    type Output = JsString;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsString> {
+        Ok(cx.string(&self.json))
+    }
+}
diff --git a/packages/core-bridge/src/helpers/mod.rs b/packages/core-bridge/src/helpers/mod.rs
new file mode 100644
index 000000000..ae959c6c2
--- /dev/null
+++ b/packages/core-bridge/src/helpers/mod.rs
@@ -0,0 +1,20 @@
+pub mod abort_controller;
+pub mod callbacks;
+pub mod errors;
+pub mod future;
+pub mod handles;
+pub mod inspect;
+pub mod json_string;
+pub mod properties;
+pub mod try_from_js;
+pub mod try_into_js;
+
+pub use abort_controller::{AbortController, AbortSignal};
+pub use callbacks::{JsAsyncCallback, JsCallback};
+pub use errors::{AppendFieldContext, BridgeError, BridgeResult, IntoThrow};
+pub use future::BridgeFuture;
+pub use handles::{OpaqueInboundHandle, OpaqueOutboundHandle};
+pub use json_string::JsonString;
+pub use properties::{FunctionContextExt as _, ObjectExt as _};
+pub use try_from_js::TryFromJs;
+pub use try_into_js::TryIntoJs;
diff --git a/packages/core-bridge/src/helpers/properties.rs b/packages/core-bridge/src/helpers/properties.rs
new file mode 100644
index 000000000..1a362fb53
--- /dev/null
+++ b/packages/core-bridge/src/helpers/properties.rs
@@ -0,0 +1,45 @@
+use neon::prelude::*;
+
+use super::{AppendFieldContext as _, BridgeError, BridgeResult, TryFromJs};
+
+/// Extension trait for `JsObject` that adds a method to get a property and convert
+/// it to a value using `TryFromJs`.
+///
+/// Type errors will be reported with `field` set to the name of the property being
+/// accessed; it is expected that caller will prepend any additional path components
+/// that led to this object, to help identify the object that failed.
+pub trait ObjectExt: Object {
+    fn get_property_into<'cx, C: Context<'cx>, T: TryFromJs>(
+        &self,
+        cx: &mut C,
+        key: &str,
+    ) -> BridgeResult<T> {
+        let value = self.get_value(cx, key)?;
+        if value.is_a::<JsUndefined, _>(cx) {
+            return Err(BridgeError::TypeError {
+                message: format!("Missing property '{key}'"),
+                field: Some(key.to_string()),
+            });
+        }
+        <T>::try_from_js(cx, value).field(key)
+    }
+}
+
+impl ObjectExt for JsObject {}
+
+/// Extension trait for `FunctionContext` that adds a method to get an argument and
+/// convert it to a value using `TryFromJs`.
+///
+/// Type errors will be reported with field name `args[index]`; it is expected that
+/// caller will prepend the function name to the error message's `field` to help identify
+/// the function that failed.
+pub trait FunctionContextExt {
+    fn argument_into<T: TryFromJs>(&mut self, index: usize) -> BridgeResult<T>;
+}
+
+impl FunctionContextExt for FunctionContext<'_> {
+    fn argument_into<T: TryFromJs>(&mut self, index: usize) -> BridgeResult<T> {
+        let value = self.argument::<JsValue>(index)?;
+        <T>::try_from_js(self, value).field(format!("args[{index}]").as_str())
+    }
+}
diff --git a/packages/core-bridge/src/helpers/try_from_js.rs b/packages/core-bridge/src/helpers/try_from_js.rs
new file mode 100644
index 000000000..a3c2ab016
--- /dev/null
+++ b/packages/core-bridge/src/helpers/try_from_js.rs
@@ -0,0 +1,222 @@
+use std::{collections::HashMap, net::SocketAddr, time::Duration};
+
+use neon::{
+    handle::Handle,
+    object::Object,
+    prelude::Context,
+    types::{
+        JsArray, JsBoolean, JsBuffer, JsNull, JsNumber, JsObject, JsString, JsValue, Value,
+        buffer::TypedArray,
+    },
+};
+use temporal_sdk_core::Url;
+
+use super::{BridgeError, BridgeResult};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// Trait for Rust types that can be created from JavaScript values, possibly throwing an error.
+pub trait TryFromJs: Sized {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self>;
+}
+
+// TryFromJs implementations for primitives and other basic types //////////////////////////////////
+
+impl TryFromJs for () {
+    fn try_from_js<'cx, 'b>(
+        _cx: &mut impl Context<'cx>,
+        _: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        Ok(())
+    }
+}
+
+impl TryFromJs for String {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        Ok(js_value.downcast::<JsString, _>(cx)?.value(cx))
+    }
+}
+
+impl TryFromJs for bool {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        Ok(js_value.downcast::<JsBoolean, _>(cx)?.value(cx))
+    }
+}
+
+impl TryFromJs for u16 {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
+        Ok(js_value.downcast::<JsNumber, _>(cx)?.value(cx) as Self)
+    }
+}
+
+#[allow(clippy::cast_possible_truncation)]
+impl TryFromJs for i32 {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        Ok(js_value.downcast::<JsNumber, _>(cx)?.value(cx) as Self)
+    }
+}
+
+#[allow(clippy::cast_possible_truncation)]
+impl TryFromJs for f32 {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        Ok(js_value.downcast::<JsNumber, _>(cx)?.value(cx) as Self)
+    }
+}
+
+#[allow(clippy::cast_possible_truncation)]
+impl TryFromJs for u64 {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        #[allow(clippy::cast_sign_loss)]
+        Ok(js_value.downcast::<JsNumber, _>(cx)?.value(cx) as Self)
+    }
+}
+
+impl TryFromJs for f64 {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        Ok(js_value.downcast::<JsNumber, _>(cx)?.value(cx))
+    }
+}
+
+// impl TryFromJs for u128 {
+//     fn try_from_js<'cx, 'b>(
+//         cx: &mut impl Context<'cx>,
+//         js_value: Handle<'b, JsValue>,
+//     ) -> BridgeResult<Self> {
+//         Ok(js_value.downcast::<JsNumber, _>(cx)?.value(cx) as Self)
+//     }
+// }
+
+impl TryFromJs for usize {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
+        Ok(js_value.downcast::<JsNumber, _>(cx)?.value(cx) as Self)
+    }
+}
+
+impl TryFromJs for Duration {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
+        Ok(Self::from_millis(
+            js_value.downcast::<JsNumber, _>(cx)?.value(cx) as u64,
+        ))
+    }
+}
+
+impl<T: TryFromJs> TryFromJs for Option<T> {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        if js_value.is_a::<JsNull, _>(cx) {
+            Ok(None)
+        } else {
+            Ok(Some(T::try_from_js(cx, js_value)?))
+        }
+    }
+}
+
+impl TryFromJs for Vec<u8> {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        Ok(js_value.downcast::<JsBuffer, _>(cx)?.as_slice(cx).to_vec())
+    }
+}
+
+impl<T: TryFromJs> TryFromJs for Vec<T> {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        let array = js_value.downcast::<JsArray, _>(cx)?;
+        let len = array.len(cx);
+        let mut result = Self::with_capacity(len as usize);
+
+        for i in 0..len {
+            let value = array.get_value(cx, i)?;
+            result.push(T::try_from_js(cx, value)?);
+        }
+        Ok(result)
+    }
+}
+
+#[allow(clippy::implicit_hasher)]
+impl<T: TryFromJs> TryFromJs for HashMap<String, T> {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        let obj = js_value.downcast::<JsObject, _>(cx)?;
+        let props = obj.get_own_property_names(cx)?.to_vec(cx)?;
+
+        let mut map = Self::new();
+        for key_handle in props {
+            let key = key_handle.to_string(cx)?.value(cx);
+            let value = obj.get_value(cx, key_handle)?;
+            map.insert(key, T::try_from_js(cx, value)?);
+        }
+        Ok(map)
+    }
+}
+
+impl TryFromJs for SocketAddr {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        let addr = js_value.downcast::<JsString, _>(cx)?;
+        addr.value(cx)
+            .parse::<Self>()
+            .map_err(|e| BridgeError::TypeError {
+                field: None,
+                message: e.to_string(),
+            })
+    }
+}
+
+impl TryFromJs for Url {
+    fn try_from_js<'cx, 'b>(
+        cx: &mut impl Context<'cx>,
+        js_value: Handle<'b, JsValue>,
+    ) -> BridgeResult<Self> {
+        let url = js_value.downcast::<JsString, _>(cx)?;
+        url.value(cx)
+            .parse::<Self>()
+            .map_err(|e| BridgeError::TypeError {
+                field: None,
+                message: e.to_string(),
+            })
+    }
+}
diff --git a/packages/core-bridge/src/helpers/try_into_js.rs b/packages/core-bridge/src/helpers/try_into_js.rs
new file mode 100644
index 000000000..ae456f86a
--- /dev/null
+++ b/packages/core-bridge/src/helpers/try_into_js.rs
@@ -0,0 +1,106 @@
+use std::{
+    sync::Arc,
+    time::{Duration, SystemTime, UNIX_EPOCH},
+};
+
+use neon::{
+    object::Object,
+    prelude::Context,
+    result::JsResult,
+    types::{JsArray, JsBigInt, JsBoolean, JsBuffer, JsString, JsUndefined, JsValue, Value},
+};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// Trait for types that can be converted to JavaScript values, possibly throwing an error.
+pub trait TryIntoJs {
+    type Output: Value;
+    fn try_into_js<'cx>(self, cx: &mut impl Context<'cx>) -> JsResult<'cx, Self::Output>;
+}
+
+// TryIntoJs implementations for primitives and other basic types //////////////////////////////////
+
+impl TryIntoJs for bool {
+    type Output = JsBoolean;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsBoolean> {
+        Ok(cx.boolean(self))
+    }
+}
+
+impl TryIntoJs for String {
+    type Output = JsString;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsString> {
+        Ok(cx.string(self.as_str()))
+    }
+}
+
+impl<T: TryIntoJs> TryIntoJs for Vec<T> {
+    type Output = JsArray;
+
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsArray> {
+        let array = cx.empty_array();
+        for (i, item) in self.into_iter().enumerate() {
+            let item = item.try_into_js(cx)?;
+            #[allow(clippy::cast_possible_truncation)]
+            array.set(cx, i as u32, item)?;
+        }
+        Ok(array)
+    }
+}
+
+impl TryIntoJs for Vec<u8> {
+    type Output = JsBuffer;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsBuffer> {
+        JsBuffer::from_slice(cx, &self)
+    }
+}
+
+impl TryIntoJs for SystemTime {
+    type Output = JsBigInt;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsBigInt> {
+        let nanos = self
+            .duration_since(UNIX_EPOCH)
+            .unwrap_or(Duration::ZERO)
+            .as_nanos();
+        Ok(JsBigInt::from_u128(cx, nanos))
+    }
+}
+
+impl<T: TryIntoJs> TryIntoJs for Option<T> {
+    // Output really is (T::Output | JsNull), hence JsValue
+    type Output = JsValue;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsValue> {
+        if let Some(value) = self {
+            Ok(value.try_into_js(cx)?.upcast())
+        } else {
+            Ok(cx.null().upcast())
+        }
+    }
+}
+
+impl<T: TryIntoJs + Clone> TryIntoJs for Arc<T> {
+    type Output = T::Output;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, T::Output> {
+        self.as_ref().clone().try_into_js(cx)
+    }
+}
+
+impl TryIntoJs for () {
+    type Output = JsUndefined;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsUndefined> {
+        Ok(cx.undefined())
+    }
+}
+
+impl<T0: TryIntoJs, T1: TryIntoJs> TryIntoJs for (T0, T1) {
+    type Output = JsArray;
+    fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsArray> {
+        let v0 = self.0.try_into_js(cx)?;
+        let v1 = self.1.try_into_js(cx)?;
+
+        let array = cx.empty_array();
+        array.set(cx, 0, v0)?;
+        array.set(cx, 1, v1)?;
+        Ok(array)
+    }
+}
diff --git a/packages/core-bridge/src/lib.rs b/packages/core-bridge/src/lib.rs
index e4da6a8ce..fd2e0b86f 100644
--- a/packages/core-bridge/src/lib.rs
+++ b/packages/core-bridge/src/lib.rs
@@ -1,47 +1,32 @@
-mod conversions;
-mod errors;
-mod helpers;
+#![warn(
+    clippy::pedantic,
+    clippy::nursery,
+    clippy::cargo,
+    clippy::perf,
+    clippy::style
+)]
+#![allow(
+    clippy::missing_errors_doc,
+    clippy::too_long_first_doc_paragraph,
+    clippy::option_if_let_else,
+    clippy::multiple_crate_versions
+)]
+
+pub mod helpers;
+
+mod client;
+mod ephemeral_server;
+mod logs;
 mod runtime;
-mod testing;
 mod worker;
 
-use crate::runtime::*;
-use crate::worker::*;
-use neon::prelude::*;
-use testing::*;
-
 #[neon::main]
-fn main(mut cx: ModuleContext) -> NeonResult<()> {
-    cx.export_function("getTimeOfDay", get_time_of_day)?;
-    cx.export_function("newRuntime", runtime_new)?;
-    cx.export_function("newClient", client_new)?;
-    cx.export_function("clientUpdateHeaders", client_update_headers)?;
-    cx.export_function("clientUpdateApiKey", client_update_api_key)?;
-    cx.export_function("newWorker", worker_new)?;
-    cx.export_function("newReplayWorker", replay_worker_new)?;
-    cx.export_function("pushHistory", push_history)?;
-    cx.export_function("closeHistoryStream", close_history_stream)?;
-    cx.export_function("workerInitiateShutdown", worker_initiate_shutdown)?;
-    cx.export_function("workerFinalizeShutdown", worker_finalize_shutdown)?;
-    cx.export_function("clientClose", client_close)?;
-    cx.export_function("runtimeShutdown", runtime_shutdown)?;
-    cx.export_function("pollLogs", poll_logs)?;
-    cx.export_function(
-        "workerPollWorkflowActivation",
-        worker_poll_workflow_activation,
-    )?;
-    cx.export_function("workerPollActivityTask", worker_poll_activity_task)?;
-    cx.export_function(
-        "workerCompleteWorkflowActivation",
-        worker_complete_workflow_activation,
-    )?;
-    cx.export_function("workerCompleteActivityTask", worker_complete_activity_task)?;
-    cx.export_function(
-        "workerRecordActivityHeartbeat",
-        worker_record_activity_heartbeat,
-    )?;
-    cx.export_function("startEphemeralServer", start_ephemeral_server)?;
-    cx.export_function("shutdownEphemeralServer", shutdown_ephemeral_server)?;
-    cx.export_function("getEphemeralServerTarget", get_ephemeral_server_target)?;
+fn main(mut cx: neon::prelude::ModuleContext) -> neon::prelude::NeonResult<()> {
+    runtime::init(&mut cx)?;
+    client::init(&mut cx)?;
+    worker::init(&mut cx)?;
+    logs::init(&mut cx)?;
+    ephemeral_server::init(&mut cx)?;
+
     Ok(())
 }
diff --git a/packages/core-bridge/src/logs.rs b/packages/core-bridge/src/logs.rs
new file mode 100644
index 000000000..26e7cf556
--- /dev/null
+++ b/packages/core-bridge/src/logs.rs
@@ -0,0 +1,114 @@
+use std::{
+    collections::HashMap,
+    time::{Duration, SystemTime, UNIX_EPOCH},
+};
+
+use neon::prelude::*;
+
+use serde::{Serialize, ser::SerializeMap as _};
+use temporal_sdk_core::api::telemetry::CoreLog;
+
+use bridge_macros::js_function;
+
+// use crate::helpers::primitives::JsonString;
+use crate::helpers::{BridgeError, BridgeResult, IntoThrow, JsonString, TryIntoJs};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub fn init(cx: &mut neon::prelude::ModuleContext) -> neon::prelude::NeonResult<()> {
+    cx.export_function("getTimeOfDay", get_time_of_day)?;
+
+    Ok(())
+}
+
+/// Helper to get the current time in nanosecond resolution. Nano seconds timestamps are
+/// used to precisely sort logs emitted from the Workflow Context, main thread, and Core.
+#[js_function]
+pub fn get_time_of_day() -> BridgeResult<SystemTime> {
+    Ok(SystemTime::now())
+}
+
+#[derive(Debug, Clone, Serialize)]
+pub struct LogEntry {
+    pub level: String,
+    pub timestamp: String, // u128 as a string - JSON doesn't support u128 numbers
+    pub message: String,
+
+    #[serde(serialize_with = "serialize_map_as_camel_case")]
+    pub fields: HashMap<String, serde_json::Value>,
+    //
+    // CoreLog has a `target` field, but we don't want to expose it to JS
+    // pub target: String,
+}
+
+impl TryFrom<CoreLog> for JsonString<LogEntry> {
+    type Error = BridgeError;
+
+    fn try_from(core_log: CoreLog) -> BridgeResult<Self> {
+        let timestamp = core_log
+            .timestamp
+            .duration_since(UNIX_EPOCH)
+            .unwrap_or(Duration::ZERO)
+            .as_nanos();
+
+        Self::try_from_value(LogEntry {
+            level: core_log.level.to_string(),
+            timestamp: timestamp.to_string(),
+            message: core_log.message,
+            fields: core_log.fields,
+        })
+    }
+}
+
+fn serialize_map_as_camel_case<S>(
+    value: &HashMap<String, serde_json::Value>,
+    serializer: S,
+) -> Result<S::Ok, S::Error>
+where
+    S: serde::Serializer,
+{
+    // let mut map = serializer.serialize_map(Some(value.len()))?;
+    let mut map = serializer.serialize_map(Some(value.len()))?;
+    for (k, v) in value {
+        map.serialize_entry(&snake_to_camel(k), v)?;
+    }
+    map.end()
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+fn snake_to_camel(input: &str) -> String {
+    match input.find('_') {
+        None => input.to_string(),
+        Some(first) => {
+            let mut result = String::with_capacity(input.len());
+            if first > 0 {
+                result.push_str(&input[..first]);
+            }
+            let mut capitalize = true;
+            for c in input[first + 1..].chars() {
+                if c == '_' {
+                    capitalize = true;
+                } else if capitalize {
+                    result.push(c.to_ascii_uppercase());
+                    capitalize = false;
+                } else {
+                    result.push(c.to_ascii_lowercase());
+                }
+            }
+            result
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn snake_to_camel_works() {
+        assert_eq!(snake_to_camel("this_is_a_test"), "thisIsATest");
+        assert_eq!(snake_to_camel("this___IS_a_TEST"), "thisIsATest");
+        assert_eq!(snake_to_camel("éàç_this_is_a_test"), "éàçThisIsATest");
+    }
+}
diff --git a/packages/core-bridge/src/runtime.rs b/packages/core-bridge/src/runtime.rs
index dd13cc2cc..cf74ddc7f 100644
--- a/packages/core-bridge/src/runtime.rs
+++ b/packages/core-bridge/src/runtime.rs
@@ -1,557 +1,440 @@
-use crate::{conversions::*, errors::*, helpers::*, worker::*};
-use neon::{context::Context, prelude::*};
-use std::{
-    cell::{Cell, RefCell},
-    collections::HashMap,
-    ops::Deref,
-    process::Stdio,
-    sync::Arc,
-    time::{Duration, SystemTime, UNIX_EPOCH},
-};
-use temporal_client::{ClientInitError, ConfiguredClient, TemporalServiceClientWithMetrics};
+use std::{sync::Arc, time::Duration};
+
+use anyhow::Context as _;
+use futures::channel::mpsc::Receiver;
+use neon::prelude::*;
+
 use temporal_sdk_core::{
-    ClientOptions, CoreRuntime, RetryClient, TokioRuntimeBuilder, WorkerConfig,
-    api::telemetry::CoreTelemetry,
-    ephemeral_server::EphemeralServer as CoreEphemeralServer,
-    init_replay_worker, init_worker,
-    replay::{HistoryForReplay, ReplayWorkerInput},
-};
-use tokio::sync::{
-    Mutex,
-    mpsc::{Sender, UnboundedReceiver, UnboundedSender, channel, unbounded_channel},
-    oneshot,
+    CoreRuntime, TokioRuntimeBuilder,
+    api::telemetry::{
+        CoreLog, OtelCollectorOptions as CoreOtelCollectorOptions,
+        PrometheusExporterOptions as CorePrometheusExporterOptions, metrics::CoreMeter,
+    },
+    telemetry::{build_otlp_metric_exporter, start_prometheus_metric_exporter},
 };
-use tokio_stream::wrappers::ReceiverStream;
 
-pub type CoreClient = RetryClient<ConfiguredClient<TemporalServiceClientWithMetrics>>;
+use bridge_macros::js_function;
+use tokio_stream::StreamExt as _;
 
-#[derive(Clone)]
-pub struct EphemeralServer {
-    pub(crate) runtime: Arc<RuntimeHandle>,
-    pub(crate) core_server: Arc<Mutex<CoreEphemeralServer>>,
-}
-pub type BoxedEphemeralServer = JsBox<RefCell<Option<EphemeralServer>>>;
-impl Finalize for EphemeralServer {}
+use crate::{helpers::*, logs::LogEntry};
 
-pub struct RuntimeHandle {
-    pub(crate) sender: UnboundedSender<RuntimeRequest>,
-}
+////////////////////////////////////////////////////////////////////////////////////////////////////
 
-/// Box it so we can use the runtime from JS
-pub type BoxedRuntime = JsBox<Arc<RuntimeHandle>>;
-impl Finalize for RuntimeHandle {}
+pub struct Runtime {
+    // Public because it's accessed from all other modules
+    #[allow(clippy::struct_field_names)]
+    pub(crate) core_runtime: Arc<CoreRuntime>,
 
-#[derive(Clone)]
-pub struct Client {
-    pub(crate) runtime: Arc<RuntimeHandle>,
-    pub(crate) core_client: Arc<CoreClient>,
+    log_exporter_task: Option<Arc<tokio::task::JoinHandle<()>>>,
+    metrics_exporter_task: Option<Arc<tokio::task::AbortHandle>>,
+
+    // For some unknown reason, the otel metrics exporter will go crazy on shutdown in some
+    // scenarios if we don't hold on to the `CoreOtelMeter` till the `Runtime` finally gets dropped.
+    _otel_metrics_exporter: Option<Arc<dyn CoreMeter + 'static>>,
 }
 
-pub type BoxedClient = JsBox<RefCell<Option<Client>>>;
-impl Finalize for Client {}
+impl Finalize for Runtime {}
 
-/// A request from JS to bridge to core
-pub enum RuntimeRequest {
-    /// A request to shutdown the runtime, breaks from the thread loop.
-    Shutdown {
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to create a client in a runtime
-    CreateClient {
-        runtime: Arc<RuntimeHandle>,
-        options: ClientOptions,
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to update a client's HTTP request headers
-    UpdateClientHeaders {
-        client: Arc<CoreClient>,
-        headers: HashMap<String, String>,
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to create a new Worker using a connected client
-    InitWorker {
-        /// Worker configuration e.g. limits and task queue
-        config: WorkerConfig,
-        /// A client created with a [CreateClient] request
-        client: Arc<CoreClient>,
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to register a replay worker
-    InitReplayWorker {
-        runtime: Arc<RuntimeHandle>,
-        /// Worker configuration. Must have unique task queue name.
-        config: WorkerConfig,
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to drain logs from core so they can be emitted in node
-    PollLogs {
-        /// Logs are sent to this function
-        callback: Root<JsFunction>,
-    },
-    StartEphemeralServer {
-        runtime: Arc<RuntimeHandle>,
-        config: EphemeralServerConfig,
-        callback: Root<JsFunction>,
-    },
-    ShutdownEphemeralServer {
-        server: Arc<Mutex<CoreEphemeralServer>>,
-        callback: Root<JsFunction>,
-    },
-    PushReplayHistory {
-        tx: Sender<HistoryForReplay>,
-        pushme: HistoryForReplay,
-        callback: Root<JsFunction>,
-    },
-    UpdateClientApiKey {
-        client: Arc<CoreClient>,
-        key: String,
-        callback: Root<JsFunction>,
-    },
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub fn init(cx: &mut neon::prelude::ModuleContext) -> neon::prelude::NeonResult<()> {
+    cx.export_function("newRuntime", runtime_new)?;
+    cx.export_function("runtimeShutdown", runtime_shutdown)?;
+
+    Ok(())
 }
 
-/// Builds a tokio runtime and starts polling on [RuntimeRequest]s via an internal channel.
-/// Bridges requests from JS to core and sends responses back to JS using a neon::Channel.
-/// Blocks current thread until a [Shutdown] request is received in channel.
-pub fn start_bridge_loop(
-    telemetry_options: TelemOptsRes,
-    channel: Arc<Channel>,
-    receiver: &mut UnboundedReceiver<RuntimeRequest>,
-    result_sender: oneshot::Sender<Result<(), String>>,
-) {
-    let mut tokio_builder = tokio::runtime::Builder::new_multi_thread();
-    tokio_builder.enable_all().thread_name("core");
-    let telem_opts = telemetry_options.0;
-    let meter_maker = telemetry_options.1;
-    let tokio_builder: TokioRuntimeBuilder<Box<dyn Fn() + Send + Sync>> = TokioRuntimeBuilder {
-        inner: tokio_builder,
-        lang_on_thread_start: None,
-    };
-    let mut core_runtime =
-        CoreRuntime::new(telem_opts, tokio_builder).expect("Failed to create CoreRuntime");
-
-    core_runtime.tokio_handle().block_on(async {
-        if let Some(meter_maker) = meter_maker {
-            match meter_maker() {
-                Ok(meter) => {
-                    core_runtime.telemetry_mut().attach_late_init_metrics(meter);
-                }
-                Err(err) => {
-                    result_sender
-                        .send(Err(format!("Failed to create meter: {}", err)))
-                        .unwrap_or_else(|_| {
-                            panic!("Failed to report runtime start error: {}", err)
-                        });
-                    return;
-                }
-            }
+/// Initialize Core global telemetry and create the tokio runtime required to run Core.
+/// This should typically be called once on process startup.
+#[js_function]
+pub fn runtime_new(
+    bridge_options: config::RuntimeOptions,
+) -> BridgeResult<OpaqueOutboundHandle<Runtime>> {
+    let (telemetry_options, metrics_options, logging_options) = bridge_options.try_into()?;
+
+    // Create core runtime which starts tokio multi-thread runtime
+    let mut core_runtime = CoreRuntime::new(telemetry_options, TokioRuntimeBuilder::default())
+        .context("Failed to initialize Core Runtime")?;
+
+    let _guard = core_runtime.tokio_handle().enter();
+
+    // Run the metrics exporter task, if needed
+    // Created after Core runtime since it needs Tokio handle
+    let (prom_metrics_exporter_task, otel_metrics_exporter) = match metrics_options {
+        Some(BridgeMetricsExporter::Prometheus(prom_opts)) => {
+            let exporter = start_prometheus_metric_exporter(prom_opts)
+                .context("Failed to start prometheus metrics exporter")?;
+
+            core_runtime
+                .telemetry_mut()
+                .attach_late_init_metrics(exporter.meter);
+
+            (Some(exporter.abort_handle), None)
         }
-        result_sender
-            .send(Ok(()))
-            .expect("Failed to report runtime start success");
-
-        loop {
-            let request_option = receiver.recv().await;
-            let request = match request_option {
-                None => break,
-                Some(request) => request,
-            };
+        Some(BridgeMetricsExporter::Otel(otel_opts)) => {
+            let exporter = build_otlp_metric_exporter(otel_opts)
+                .context("Failed to start OTel metrics exporter")?;
 
-            let channel = channel.clone();
-
-            match request {
-                RuntimeRequest::Shutdown { callback } => {
-                    send_result(channel, callback, |cx| Ok(cx.undefined()));
-                    break;
-                }
-                RuntimeRequest::CreateClient {
-                    runtime,
-                    options,
-                    callback,
-                } => {
-                    let mm = core_runtime.telemetry().get_temporal_metric_meter();
-                    core_runtime.tokio_handle().spawn(async move {
-                        match options
-                            .connect_no_namespace(mm)
-                            .await
-                        {
-                            Err(err) => {
-                                send_error(channel.clone(), callback, |cx| match err {
-                                    ClientInitError::SystemInfoCallError(e) => {
-                                        make_named_error_from_string(
-                                            cx,
-                                            TRANSPORT_ERROR,
-                                            format!("Failed to call GetSystemInfo: {}", e),
-                                        )
-                                    }
-                                    ClientInitError::TonicTransportError(e) => {
-                                        make_named_error_from_error(cx, TRANSPORT_ERROR, e)
-                                    }
-                                    ClientInitError::InvalidUri(e) => {
-                                        Ok(JsError::type_error(cx, format!("{}", e))?)
-                                    }
-                                });
-                            }
-                            Ok(client) => {
-                                send_result(channel.clone(), callback, |cx| {
-                                    Ok(cx.boxed(RefCell::new(Some(Client {
-                                        runtime,
-                                        core_client: Arc::new(client),
-                                    }))))
-                                });
-                            }
-                        }
-                    });
-                }
-                RuntimeRequest::UpdateClientHeaders {
-                    client,
-                    headers,
-                    callback,
-                } => {
-                    client.get_client().set_headers(headers);
-                    send_result(channel.clone(), callback, |cx| Ok(cx.undefined()));
-                }
-                RuntimeRequest::UpdateClientApiKey { client, key, callback } => {
-                    client.get_client().set_api_key(Some(key));
-                    send_result(channel.clone(), callback, |cx| Ok(cx.undefined()));
-                }
-                RuntimeRequest::PollLogs { callback } => {
-                    let logs = core_runtime.telemetry().fetch_buffered_logs();
-                    send_result(channel.clone(), callback, |cx| {
-                        let logarr = cx.empty_array();
-                        for (i, cl) in logs.into_iter().enumerate() {
-                            // Not much to do here except for panic when there's an error here.
-                            let logobj = cx.empty_object();
+            let exporter: Arc<dyn CoreMeter + 'static> = Arc::new(exporter);
+            core_runtime
+                .telemetry_mut()
+                .attach_late_init_metrics(exporter.clone());
 
-                            let level = cx.string(cl.level.to_string());
-                            logobj.set(cx, "level", level).unwrap();
+            (None, Some(exporter))
+        }
+        None => (None, None),
+    };
 
-                            let ts = system_time_to_js(cx, cl.timestamp).unwrap();
-                            logobj.set(cx, "timestamp", ts).unwrap();
+    // Run the log exporter task, if needed
+    // Created after Core runtime since it needs Tokio handle
+    let log_exporter_task = if let BridgeLogExporter::Push { stream, receiver } = logging_options {
+        let log_exporter_task = Arc::new(core_runtime.tokio_handle().spawn(async move {
+            let mut stream = std::pin::pin!(stream.chunks_timeout(
+                config::FORWARD_LOG_BUFFER_SIZE,
+                Duration::from_millis(config::FORWARD_LOG_MAX_FREQ_MS)
+            ));
+
+            while let Some(core_logs) = stream.next().await {
+                // We silently swallow errors here because logging them could
+                // cause a bad loop and we don't want to assume console presence
+                let core_logs = core_logs
+                    .into_iter()
+                    .filter_map(|log| JsonString::<LogEntry>::try_from(log).ok())
+                    .collect::<Vec<_>>();
+                let _ = receiver.call_on_js_thread((core_logs,));
+            }
+        }));
+        Some(log_exporter_task)
+    } else {
+        None
+    };
 
-                            let msg = cx.string(cl.message);
-                            logobj.set(cx, "message", msg).unwrap();
+    Ok(OpaqueOutboundHandle::new(Runtime {
+        core_runtime: Arc::new(core_runtime),
+        log_exporter_task,
+        metrics_exporter_task: prom_metrics_exporter_task.map(Arc::new),
+        _otel_metrics_exporter: otel_metrics_exporter,
+    }))
+}
 
-                            let fieldsobj = hashmap_to_js_value(cx, cl.fields);
-                            logobj.set(cx, "fields", fieldsobj.unwrap()).unwrap();
+/// Stops the bridge runtime. In practice, this simply drops the RuntimeHandle out of the
+/// BoxedRuntimeRef, and is therefore almost the same as just waiting for the lang-side GC
+/// to drop the JS counterpart of BoxedRuntimeRef, but this function gives us a bit more
+/// control on when that happens (b/c we don't have to wait for the JS GC), which is useful
+/// when starting/stopping runtimes at a high pace, e.g. during tests execution.
+#[js_function]
+pub fn runtime_shutdown(runtime: OpaqueInboundHandle<Runtime>) -> BridgeResult<()> {
+    std::mem::drop(runtime.take_inner()?);
+    Ok(())
+}
 
-                            let target = cx.string(cl.target);
-                            logobj.set(cx, "target", target).unwrap();
+impl Drop for Runtime {
+    fn drop(&mut self) {
+        if let Some(handle) = self.log_exporter_task.take() {
+            handle.abort();
+        }
 
-                            logarr.set(cx, i as u32, logobj).unwrap();
-                        }
-                        Ok(logarr)
-                    });
-                }
-                RuntimeRequest::InitWorker {
-                    config,
-                    client,
-                    callback,
-                } => {
-                    let client = (*client).clone();
-                    match init_worker(&core_runtime, config, client) {
-                        Ok(worker) => {
-                            core_runtime.tokio_handle().spawn(start_worker_loop(
-                                worker,
-                                channel,
-                                callback,
-                                None,
-                            ));
-                        }
-                        Err(err) => send_error(channel.clone(), callback, move |cx| {
-                            make_named_error_from_error(cx, UNEXPECTED_ERROR, err.deref())
-                        }),
-                    }
-                }
-                RuntimeRequest::InitReplayWorker {
-                    runtime,
-                    config,
-                    callback,
-                } => {
-                    let (tunnel, stream) = HistoryForReplayTunnel::new(runtime);
-                    match init_replay_worker(ReplayWorkerInput::new(config, Box::pin(stream))) {
-                        Ok(worker) => {
-                            core_runtime.tokio_handle().spawn(start_worker_loop(
-                                worker,
-                                channel.clone(),
-                                callback,
-                                Some(tunnel),
-                            ));
-                        }
-                        Err(err) => send_error(channel.clone(), callback, move |cx| {
-                            make_named_error_from_error(cx, UNEXPECTED_ERROR, err.deref())
-                        }),
-                    };
-                }
-                RuntimeRequest::StartEphemeralServer {
-                    runtime,
-                    config,
-                    callback,
-                } => {
-                    core_runtime.tokio_handle().spawn(async move {
-                        let stdout = Stdio::from(std::io::stdout());
-                        let stderr = Stdio::from(std::io::stderr());
-                        let result = match config {
-                            EphemeralServerConfig::TestServer(config) => {
-                                config.start_server_with_output(stdout, stderr).await
-                            }
-                            EphemeralServerConfig::DevServer(config) => {
-                                config.start_server_with_output(stdout, stderr).await
-                            }
-                        };
-                        match result {
-                            Err(err) => {
-                                let err_str = format!("Failed to start ephemeral server: {}", err);
-                                send_error(channel.clone(), callback, |cx| {
-                                    make_named_error_from_string(cx, UNEXPECTED_ERROR, err_str)
-                                });
-                            }
-                            Ok(server) => {
-                                send_result(channel.clone(), callback, |cx| {
-                                    Ok(cx.boxed(RefCell::new(Some(EphemeralServer {
-                                        runtime,
-                                        core_server: Arc::new(Mutex::new(server)),
-                                    }))))
-                                });
-                            }
-                        }
-                    });
-                }
-                RuntimeRequest::ShutdownEphemeralServer { server, callback } => {
-                    core_runtime.tokio_handle().spawn(async move {
-                        void_future_to_js(
-                            channel,
-                            callback,
-                            async move {
-                                let mut guard = server.lock().await;
-                                guard.shutdown().await
-                            },
-                            |cx, err| {
-                                make_named_error_from_string(
-                                    cx,
-                                    UNEXPECTED_ERROR,
-                                    format!("Failed to start test server: {}", err),
-                                )
-                            },
-                        ).await
-                    });
-                }
-                RuntimeRequest::PushReplayHistory {
-                    tx,
-                    pushme,
-                    callback,
-                } => {
-                    core_runtime.tokio_handle().spawn(async move {
-                        let sendfut = async move {
-                            tx.send(pushme).await.map_err(|e| {
-                                format!(
-                                    "Receive side of history replay channel is gone. This is an sdk bug. {:?}",
-                                    e
-                                )
-                            })
-                        };
-                        void_future_to_js(channel, callback, sendfut, |cx, err| {
-                            make_named_error_from_string(
-                                cx,
-                                UNEXPECTED_ERROR,
-                                format!("Error pushing replay history {}", err),
-                            )
-                        }).await
-                    });
-                }
-            }
+        if let Some(handle) = self.metrics_exporter_task.take() {
+            handle.abort();
         }
-    })
+    }
 }
 
-// Below are functions exported to JS
-
-/// Convert Rust SystemTime into a JS array with 2 numbers (seconds, nanos)
-pub fn system_time_to_js<'a, C>(cx: &mut C, time: SystemTime) -> NeonResult<Handle<'a, JsArray>>
-where
-    C: Context<'a>,
-{
-    let nanos = time
-        .duration_since(UNIX_EPOCH)
-        .unwrap_or(Duration::ZERO)
-        .as_nanos();
-    let only_nanos = cx.number((nanos % 1_000_000_000) as f64);
-    let ts_seconds = cx.number((nanos / 1_000_000_000) as f64);
-    let ts = cx.empty_array();
-    ts.set(cx, 0, ts_seconds).unwrap();
-    ts.set(cx, 1, only_nanos).unwrap();
-    Ok(ts)
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+#[macro_export]
+macro_rules! enter_sync {
+    ($runtime:expr) => {
+        if let Some(subscriber) = $runtime.telemetry().trace_subscriber() {
+            temporal_sdk_core::telemetry::set_trace_subscriber_for_current_thread(subscriber);
+        }
+        let _guard = $runtime.tokio_handle().enter();
+    };
 }
 
-/// Helper to get the current time in nanosecond resolution.
-pub fn get_time_of_day(mut cx: FunctionContext) -> JsResult<JsArray> {
-    system_time_to_js(&mut cx, SystemTime::now())
+pub trait RuntimeExt {
+    fn future_to_promise<F, R>(&self, future: F) -> BridgeResult<BridgeFuture<R>>
+    where
+        F: Future<Output = Result<R, BridgeError>> + Send + 'static,
+        R: TryIntoJs + Send + 'static;
 }
 
-/// Initialize Core global telemetry and create the tokio runtime required to run Core.
-/// This should typically be called once on process startup.
-/// Immediately spawns a poller thread that will block on [RuntimeRequest]s
-pub fn runtime_new(mut cx: FunctionContext) -> JsResult<BoxedRuntime> {
-    let telemetry_options = cx.argument::<JsObject>(0)?.as_telemetry_options(&mut cx)?;
-    let channel = Arc::new(cx.channel());
-    let (sender, mut receiver) = unbounded_channel::<RuntimeRequest>();
-
-    // FIXME: This is a temporary fix to get sync notifications of errors while initializing the runtime.
-    //        The proper fix would be to avoid spawning a new thread here, so that start_bridge_loop
-    //        can simply yeild back a Result. But early attempts to do just that caused panics
-    //        on runtime shutdown, so let's use this hack until we can dig deeper.
-    let (result_sender, result_receiver) = oneshot::channel::<Result<(), String>>();
-
-    std::thread::spawn(move || {
-        start_bridge_loop(telemetry_options, channel, &mut receiver, result_sender)
-    });
-
-    if let Ok(Err(e)) = result_receiver.blocking_recv() {
-        Err(cx.throw_error::<_, String>(e).unwrap_err())?;
+impl RuntimeExt for CoreRuntime {
+    fn future_to_promise<F, R>(&self, future: F) -> BridgeResult<BridgeFuture<R>>
+    where
+        F: Future<Output = Result<R, BridgeError>> + Send + 'static,
+        R: TryIntoJs + Send + 'static,
+    {
+        enter_sync!(self);
+        Ok(BridgeFuture::new(Box::pin(future)))
     }
+}
 
-    Ok(cx.boxed(Arc::new(RuntimeHandle { sender })))
+impl RuntimeExt for Arc<CoreRuntime> {
+    fn future_to_promise<F, R>(&self, future: F) -> BridgeResult<BridgeFuture<R>>
+    where
+        F: Future<Output = Result<R, BridgeError>> + Send + 'static,
+        R: TryIntoJs + Send + 'static,
+    {
+        self.as_ref().future_to_promise(future)
+    }
 }
 
-/// Shutdown the Core instance and break out of the thread loop
-pub fn runtime_shutdown(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let runtime = cx.argument::<BoxedRuntime>(0)?;
-    let callback = cx.argument::<JsFunction>(1)?;
-    let request = RuntimeRequest::Shutdown {
-        callback: callback.root(&mut cx),
-    };
-    if let Err(err) = runtime.sender.send(request) {
-        callback_with_unexpected_error(&mut cx, callback, err)?;
-    };
-    Ok(cx.undefined())
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+#[derive(Debug, Clone)]
+pub enum BridgeMetricsExporter {
+    Prometheus(CorePrometheusExporterOptions),
+    Otel(CoreOtelCollectorOptions),
 }
 
-/// Request to drain forwarded logs from core
-pub fn poll_logs(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let runtime = cx.argument::<BoxedRuntime>(0)?;
-    let callback = cx.argument::<JsFunction>(1)?;
-    let request = RuntimeRequest::PollLogs {
-        callback: callback.root(&mut cx),
-    };
-    if let Err(err) = runtime.sender.send(request) {
-        callback_with_unexpected_error(&mut cx, callback, err)?;
-    }
-    Ok(cx.undefined())
+pub enum BridgeLogExporter {
+    Console,
+    Push {
+        stream: Receiver<CoreLog>,
+        receiver: JsCallback<(Vec<JsonString<LogEntry>>,), ()>,
+    },
 }
 
-/// Create a connected gRPC client which can be used to initialize workers.
-/// Client will be returned in the supplied `callback`.
-pub fn client_new(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let runtime = cx.argument::<BoxedRuntime>(0)?;
-    let opts = cx.argument::<JsObject>(1)?;
-    let callback = cx.argument::<JsFunction>(2)?;
+////////////////////////////////////////////////////////////////////////////////////////////////////
 
-    let client_options = opts.as_client_options(&mut cx)?;
+// IMORTANT: Any struct or enum below this point must be kept in sync with the type of the same name
+//           in native.ts. Similarly,
 
-    let request = RuntimeRequest::CreateClient {
-        runtime: (**runtime).clone(),
-        options: client_options,
-        callback: callback.root(&mut cx),
-    };
-    if let Err(err) = runtime.sender.send(request) {
-        callback_with_unexpected_error(&mut cx, callback, err)?;
+mod config {
+    use std::{collections::HashMap, net::SocketAddr, sync::Arc, time::Duration};
+
+    use anyhow::Context as _;
+
+    use neon::prelude::*;
+    use temporal_sdk_core::{
+        Url,
+        api::telemetry::{
+            HistogramBucketOverrides, Logger as CoreTelemetryLogger, MetricTemporality,
+            OtelCollectorOptions as CoreOtelCollectorOptions, OtelCollectorOptionsBuilder,
+            OtlpProtocol, PrometheusExporterOptions as CorePrometheusExporterOptions,
+            PrometheusExporterOptionsBuilder, TelemetryOptions as CoreTelemetryOptions,
+            TelemetryOptionsBuilder,
+        },
+        telemetry::CoreLogStreamConsumer,
     };
 
-    Ok(cx.undefined())
-}
+    use bridge_macros::TryFromJs;
 
-/// Drop a reference to a Client, once all references are dropped, the Client will be closed.
-pub fn client_close(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let client = cx.argument::<BoxedClient>(0)?;
-    if client.replace(None).is_none() {
-        make_named_error_from_string(&mut cx, ILLEGAL_STATE_ERROR, "Client already closed")
-            .and_then(|err| cx.throw(err))?;
+    use crate::{
+        helpers::{BridgeError, BridgeResult, JsCallback, JsonString, TryFromJs},
+        logs::LogEntry,
     };
-    Ok(cx.undefined())
-}
 
-/// Update a Client's HTTP request headers
-pub fn client_update_headers(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let client = cx.argument::<BoxedClient>(0)?;
-    let headers = cx
-        .argument::<JsObject>(1)?
-        .as_hash_map_of_string_to_string(&mut cx)?;
-    let callback = cx.argument::<JsFunction>(2)?;
-
-    match client.borrow().as_ref() {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed Client")?;
-        }
-        Some(client) => {
-            let request = RuntimeRequest::UpdateClientHeaders {
-                client: client.core_client.clone(),
-                headers,
-                callback: callback.root(&mut cx),
-            };
-            if let Err(err) = client.runtime.sender.send(request) {
-                callback_with_unexpected_error(&mut cx, callback, err)?;
+    use super::BridgeLogExporter;
+
+    pub(super) const FORWARD_LOG_BUFFER_SIZE: usize = 2048;
+    pub(super) const FORWARD_LOG_MAX_FREQ_MS: u64 = 10;
+
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) struct RuntimeOptions {
+        log_exporter: LogExporter,
+        telemetry: TelemetryOptions,
+        metrics_exporter: Option<MetricsExporter>,
+    }
+
+    impl
+        TryInto<(
+            CoreTelemetryOptions,
+            Option<super::BridgeMetricsExporter>,
+            super::BridgeLogExporter,
+        )> for RuntimeOptions
+    {
+        type Error = BridgeError;
+
+        fn try_into(
+            self,
+        ) -> BridgeResult<(
+            CoreTelemetryOptions,
+            Option<super::BridgeMetricsExporter>,
+            super::BridgeLogExporter,
+        )> {
+            let (telemetry_logger, log_exporter) = match self.log_exporter {
+                LogExporter::Console { filter } => (
+                    CoreTelemetryLogger::Console { filter },
+                    BridgeLogExporter::Console,
+                ),
+                LogExporter::Forward { filter, receiver } => {
+                    let (consumer, stream) = CoreLogStreamConsumer::new(FORWARD_LOG_BUFFER_SIZE);
+                    (
+                        CoreTelemetryLogger::Push {
+                            filter,
+                            consumer: Arc::new(consumer),
+                        },
+                        BridgeLogExporter::Push { stream, receiver },
+                    )
+                }
             };
+
+            let mut telemetry_options = TelemetryOptionsBuilder::default();
+            let telemetry_options = telemetry_options
+                .logging(telemetry_logger)
+                .metric_prefix(self.telemetry.metric_prefix)
+                .attach_service_name(self.telemetry.attach_service_name)
+                .build()
+                .context("Failed to build telemetry options")?;
+
+            let metrics_exporter = self
+                .metrics_exporter
+                .map(std::convert::TryInto::try_into)
+                .transpose()?;
+
+            Ok((telemetry_options, metrics_exporter, log_exporter))
         }
     }
 
-    Ok(cx.undefined())
-}
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) struct TelemetryOptions {
+        metric_prefix: String,
+        attach_service_name: bool,
+    }
+
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) enum LogExporter {
+        Console {
+            filter: String,
+        },
+        Forward {
+            filter: String,
+            receiver: JsCallback<(Vec<JsonString<LogEntry>>,), ()>,
+        },
+    }
 
-/// Update a Client's API key
-pub fn client_update_api_key(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let client = cx.argument::<BoxedClient>(0)?;
-    let key = cx.argument::<JsString>(1)?.value(&mut cx);
-    let callback = cx.argument::<JsFunction>(2)?;
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) enum MetricsExporter {
+        Prometheus(PrometheusConfig),
+        Otel(OtelConfig),
+    }
 
-    match client.borrow().as_ref() {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed Client")?;
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) struct PrometheusConfig {
+        bind_address: SocketAddr,
+        counters_total_suffix: bool,
+        unit_suffix: bool,
+        use_seconds_for_durations: bool,
+        histogram_bucket_overrides: HashMap<String, Vec<f64>>,
+        global_tags: HashMap<String, String>,
+    }
+
+    impl TryInto<super::BridgeMetricsExporter> for MetricsExporter {
+        type Error = BridgeError;
+        fn try_into(self) -> BridgeResult<super::BridgeMetricsExporter> {
+            match self {
+                Self::Prometheus(prom) => {
+                    Ok(super::BridgeMetricsExporter::Prometheus(prom.try_into()?))
+                }
+                Self::Otel(otel) => Ok(super::BridgeMetricsExporter::Otel(otel.try_into()?)),
+            }
         }
-        Some(client) => {
-            let request = RuntimeRequest::UpdateClientApiKey {
-                client: client.core_client.clone(),
-                key,
-                callback: callback.root(&mut cx),
-            };
-            if let Err(err) = client.runtime.sender.send(request) {
-                callback_with_unexpected_error(&mut cx, callback, err)?;
-            };
+    }
+
+    impl TryInto<CorePrometheusExporterOptions> for PrometheusConfig {
+        type Error = BridgeError;
+
+        fn try_into(self) -> BridgeResult<CorePrometheusExporterOptions> {
+            let mut options = PrometheusExporterOptionsBuilder::default();
+            let options = options
+                .socket_addr(self.bind_address)
+                .counters_total_suffix(self.counters_total_suffix)
+                .unit_suffix(self.unit_suffix)
+                .use_seconds_for_durations(self.use_seconds_for_durations)
+                .histogram_bucket_overrides(HistogramBucketOverrides {
+                    overrides: self.histogram_bucket_overrides,
+                })
+                .global_tags(self.global_tags)
+                .build()
+                .context("Failed to build prometheus exporter options")?;
+
+            Ok(options)
         }
     }
 
-    Ok(cx.undefined())
-}
+    #[derive(Debug, Clone, TryFromJs)]
+    pub(super) struct OtelConfig {
+        url: Url,
+        protocol: StringEncoded<OtlpProtocol>,
+        headers: HashMap<String, String>,
+        metrics_export_interval: Duration,
+        use_seconds_for_durations: bool,
+        temporality: StringEncoded<MetricTemporality>,
+        histogram_bucket_overrides: HashMap<String, Vec<f64>>,
+        global_tags: HashMap<String, String>,
+    }
 
-pub(crate) struct HistoryForReplayTunnel {
-    pub(crate) runtime: Arc<RuntimeHandle>,
-    sender: Cell<Option<Sender<HistoryForReplay>>>,
-}
-impl HistoryForReplayTunnel {
-    fn new(runtime: Arc<RuntimeHandle>) -> (Self, ReceiverStream<HistoryForReplay>) {
-        let (sender, rx) = channel(1);
-        (
-            HistoryForReplayTunnel {
-                runtime,
-                sender: Cell::new(Some(sender)),
-            },
-            ReceiverStream::new(rx),
-        )
+    impl TryInto<CoreOtelCollectorOptions> for OtelConfig {
+        type Error = BridgeError;
+
+        fn try_into(self) -> BridgeResult<CoreOtelCollectorOptions> {
+            let mut options = OtelCollectorOptionsBuilder::default();
+            let options = options
+                .url(self.url)
+                .protocol(*self.protocol)
+                .headers(self.headers)
+                .metric_periodicity(self.metrics_export_interval)
+                .use_seconds_for_durations(self.use_seconds_for_durations)
+                .metric_temporality(*self.temporality)
+                .histogram_bucket_overrides(HistogramBucketOverrides {
+                    overrides: self.histogram_bucket_overrides,
+                })
+                .global_tags(self.global_tags)
+                .build()
+                .context("Failed to build otel exporter options")?;
+
+            Ok(options)
+        }
+    }
+
+    /// A private newtype so that we can implement `TryFromJs` on simple externally defined enums
+    #[derive(Debug, Clone)]
+    struct StringEncoded<T>(T);
+
+    impl TryFromJs for StringEncoded<OtlpProtocol> {
+        fn try_from_js<'cx, 'b>(
+            cx: &mut impl Context<'cx>,
+            js_value: Handle<'b, JsValue>,
+        ) -> BridgeResult<Self> {
+            let value = js_value.downcast::<JsString, _>(cx)?;
+            let value = value.value(cx);
+
+            match value.as_str() {
+                "http" => Ok(Self(OtlpProtocol::Http)),
+                "grpc" => Ok(Self(OtlpProtocol::Grpc)),
+                _ => Err(BridgeError::TypeError {
+                    field: None,
+                    message: "Expected either 'http' or 'grpc'".to_string(),
+                }),
+            }
+        }
     }
-    pub fn get_chan(&self) -> Result<Sender<HistoryForReplay>, &'static str> {
-        let chan = self.sender.take();
-        self.sender.set(chan.clone());
-        if let Some(chan) = chan {
-            Ok(chan)
-        } else {
-            Err("History replay channel is already closed")
+
+    impl TryFromJs for StringEncoded<MetricTemporality> {
+        fn try_from_js<'cx, 'b>(
+            cx: &mut impl Context<'cx>,
+            js_value: Handle<'b, JsValue>,
+        ) -> BridgeResult<Self> {
+            let value = js_value.downcast::<JsString, _>(cx)?;
+            let value = value.value(cx);
+
+            match value.as_str() {
+                "cumulative" => Ok(Self(MetricTemporality::Cumulative)),
+                "delta" => Ok(Self(MetricTemporality::Delta)),
+                _ => Err(BridgeError::TypeError {
+                    field: None,
+                    message: "Expected either 'cumulative' or 'delta'".to_string(),
+                }),
+            }
         }
     }
-    pub fn shutdown(&self) {
-        self.sender.take();
+
+    impl<T> std::ops::Deref for StringEncoded<T> {
+        type Target = T;
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
     }
 }
-impl Finalize for HistoryForReplayTunnel {}
diff --git a/packages/core-bridge/src/testing.rs b/packages/core-bridge/src/testing.rs
deleted file mode 100644
index 6374df1b1..000000000
--- a/packages/core-bridge/src/testing.rs
+++ /dev/null
@@ -1,70 +0,0 @@
-use crate::conversions::*;
-use crate::errors::*;
-use crate::helpers::*;
-use crate::runtime::{BoxedEphemeralServer, BoxedRuntime, RuntimeRequest};
-use neon::prelude::*;
-
-// Below are functions exported to JS
-
-/// Start an ephemeral Temporal server
-pub fn start_ephemeral_server(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let runtime = cx.argument::<BoxedRuntime>(0)?;
-    let config = cx.argument::<JsObject>(1)?;
-    let sdk_version = cx.argument::<JsString>(2)?.value(&mut cx);
-    let callback = cx.argument::<JsFunction>(3)?;
-
-    let config = config.as_ephemeral_server_config(&mut cx, sdk_version)?;
-    let request = RuntimeRequest::StartEphemeralServer {
-        runtime: (**runtime).clone(),
-        config,
-        callback: callback.root(&mut cx),
-    };
-    if let Err(err) = runtime.sender.send(request) {
-        callback_with_unexpected_error(&mut cx, callback, err)?;
-    };
-
-    Ok(cx.undefined())
-}
-
-/// Get the ephemeral server "target" (address:port string)
-pub fn get_ephemeral_server_target(mut cx: FunctionContext) -> JsResult<JsString> {
-    let server = cx.argument::<BoxedEphemeralServer>(0)?;
-    let target = server
-        .borrow()
-        .as_ref()
-        .map(|s| cx.string(s.core_server.blocking_lock().target.as_str()));
-    if target.is_none() {
-        make_named_error_from_string(
-            &mut cx,
-            ILLEGAL_STATE_ERROR,
-            "Tried to use closed test server",
-        )
-        .and_then(|err| cx.throw(err))?;
-    };
-    Ok(target.unwrap())
-}
-
-/// Shutdown an ephemeral server - consumes the server
-pub fn shutdown_ephemeral_server(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let server = cx.argument::<BoxedEphemeralServer>(0)?;
-    let callback = cx.argument::<JsFunction>(1)?;
-    // Drop the ref
-    match server.replace(None) {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed test server")?;
-        }
-        Some(server) => {
-            if let Err(err) = server
-                .runtime
-                .sender
-                .send(RuntimeRequest::ShutdownEphemeralServer {
-                    server: server.core_server.clone(),
-                    callback: callback.root(&mut cx),
-                })
-            {
-                callback_with_unexpected_error(&mut cx, callback, err)?;
-            };
-        }
-    }
-    Ok(cx.undefined())
-}
diff --git a/packages/core-bridge/src/worker.rs b/packages/core-bridge/src/worker.rs
index 14b1de273..5d0298a30 100644
--- a/packages/core-bridge/src/worker.rs
+++ b/packages/core-bridge/src/worker.rs
@@ -1,15 +1,18 @@
-use crate::{conversions::ObjectHandleConversionsExt, errors::*, helpers::*, runtime::*};
-use futures::stream::StreamExt;
-use neon::{prelude::*, types::buffer::TypedArray};
+use std::sync::Arc;
+
+use anyhow::Context as AnyhowContext;
+use neon::prelude::*;
 use prost::Message;
-use std::{cell::RefCell, sync::Arc};
-use temporal_sdk_core::replay::HistoryForReplay;
+use tokio::sync::mpsc::{Sender, channel};
+use tokio_stream::wrappers::ReceiverStream;
+
 use temporal_sdk_core::{
-    Worker as CoreWorker,
+    CoreRuntime,
     api::{
         Worker as CoreWorkerTrait,
         errors::{CompleteActivityError, CompleteWfError, PollError},
     },
+    init_replay_worker, init_worker,
     protos::{
         coresdk::{
             ActivityHeartbeat, ActivityTaskCompletion,
@@ -17,438 +20,839 @@ use temporal_sdk_core::{
         },
         temporal::api::history::v1::History,
     },
+    replay::{HistoryForReplay, ReplayWorkerInput},
 };
-use tokio::sync::mpsc::{UnboundedSender, unbounded_channel};
-use tokio_stream::wrappers::UnboundedReceiverStream;
 
-/// Worker struct, hold a reference for the channel sender responsible for sending requests from
-/// JS to a bridge thread which forwards them to core
-pub struct WorkerHandle {
-    pub(crate) sender: UnboundedSender<WorkerRequest>,
+use bridge_macros::js_function;
+
+use crate::{
+    client::Client,
+    enter_sync,
+    helpers::*,
+    runtime::{Runtime, RuntimeExt},
+};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+// Arc because most of CoreWorker's API require sending reference to the Worker into async closures.
+type CoreWorker = Arc<temporal_sdk_core::Worker>;
+
+pub struct Worker {
+    core_runtime: Arc<CoreRuntime>,
+    core_worker: CoreWorker,
 }
 
-/// Box it so we can use Worker from JS
-pub type BoxedWorker = JsBox<RefCell<Option<WorkerHandle>>>;
-impl Finalize for WorkerHandle {}
-
-#[derive(Debug)]
-pub enum WorkerRequest {
-    /// A request to shutdown a worker, the worker instance will remain active to
-    /// allow draining of pending tasks
-    InitiateShutdown {
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to poll for workflow activations
-    PollWorkflowActivation {
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to complete a single workflow activation
-    CompleteWorkflowActivation {
-        completion: WorkflowActivationCompletion,
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to poll for activity tasks
-    PollActivityTask {
-        /// Used to report completion or error back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to complete a single activity task
-    CompleteActivityTask {
-        completion: ActivityTaskCompletion,
-        /// Used to send the result back into JS
-        callback: Root<JsFunction>,
-    },
-    /// A request to send a heartbeat from a running activity
-    RecordActivityHeartbeat { heartbeat: ActivityHeartbeat },
+impl Finalize for Worker {}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub fn init(cx: &mut neon::prelude::ModuleContext) -> neon::prelude::NeonResult<()> {
+    cx.export_function("newWorker", worker_new)?;
+    cx.export_function("workerValidate", worker_validate)?;
+    cx.export_function(
+        "workerPollWorkflowActivation",
+        worker_poll_workflow_activation,
+    )?;
+    cx.export_function(
+        "workerCompleteWorkflowActivation",
+        worker_complete_workflow_activation,
+    )?;
+    cx.export_function("workerPollActivityTask", worker_poll_activity_task)?;
+    cx.export_function("workerCompleteActivityTask", worker_complete_activity_task)?;
+    cx.export_function(
+        "workerRecordActivityHeartbeat",
+        worker_record_activity_heartbeat,
+    )?;
+    cx.export_function("workerInitiateShutdown", worker_initiate_shutdown)?;
+    cx.export_function("workerFinalizeShutdown", worker_finalize_shutdown)?;
+
+    // Replay worker functions
+    cx.export_function("newReplayWorker", replay_worker_new)?;
+    cx.export_function("pushHistory", push_history)?;
+    cx.export_function("closeHistoryStream", close_history_stream)?;
+
+    Ok(())
 }
 
-/// Polls on [WorkerRequest]s via given channel.
-/// Bridges requests from JS to core and sends responses back to JS using a neon::Channel.
-/// Returns when the given channel is dropped.
-pub async fn start_worker_loop(
-    worker: CoreWorker,
-    channel: Arc<Channel>,
-    callback: Root<JsFunction>,
-    is_replay: Option<HistoryForReplayTunnel>,
-) {
-    if is_replay.is_none() {
-        if let Err(e) = worker.validate().await {
-            send_error(channel, callback, move |cx| {
-                make_named_error_from_error(cx, TRANSPORT_ERROR, e)
-            });
-            return;
+/// Create a new worker.
+#[js_function]
+pub fn worker_new(
+    client: OpaqueInboundHandle<Client>,
+    worker_options: config::BridgeWorkerOptions,
+) -> BridgeResult<OpaqueOutboundHandle<Worker>> {
+    let config = worker_options
+        .into_core_config()
+        .context("Failed to convert WorkerOptions to CoreWorkerConfig")?;
+
+    let client_ref = client.borrow_inner()?;
+    let client = client_ref.core_client.clone();
+    let runtime = client_ref.core_runtime.clone();
+
+    enter_sync!(runtime);
+    let worker = init_worker(&runtime, config, client).context("Failed to initialize worker")?;
+
+    Ok(OpaqueOutboundHandle::new(Worker {
+        core_runtime: runtime,
+        core_worker: Arc::new(worker),
+    }))
+}
+
+/// Validate a worker.
+#[js_function]
+pub fn worker_validate(worker: OpaqueInboundHandle<Worker>) -> BridgeResult<BridgeFuture<()>> {
+    let (runtime, worker) = worker.map_inner(|worker| {
+        (
+            Arc::clone(&worker.core_runtime),
+            Arc::clone(&worker.core_worker),
+        )
+    })?;
+
+    runtime.future_to_promise(async move {
+        worker
+            .validate()
+            .await
+            .map_err(|err| BridgeError::TransportError(err.to_string()))
+    })
+}
+
+/// Initiate a single workflow activation poll request.
+/// There should be only one concurrent poll request for this type.
+#[js_function]
+pub fn worker_poll_workflow_activation(
+    worker: OpaqueInboundHandle<Worker>,
+) -> BridgeResult<BridgeFuture<Vec<u8>>> {
+    let (runtime, worker) = worker.map_inner(|worker| {
+        (
+            Arc::clone(&worker.core_runtime),
+            Arc::clone(&worker.core_worker),
+        )
+    })?;
+
+    runtime.future_to_promise(async move {
+        let result = worker.poll_workflow_activation().await;
+
+        match result {
+            Ok(task) => Ok(task.encode_to_vec()),
+            Err(err) => match err {
+                PollError::ShutDown => Err(BridgeError::WorkerShutdown)?,
+                PollError::TonicError(status) => {
+                    Err(BridgeError::TransportError(status.message().to_string()))?
+                }
+            },
         }
-    }
-    let (tx, rx) = unbounded_channel();
-    // Return the worker after validation has happened
-    if let Some(tunnel) = is_replay {
-        send_result(channel.clone(), callback, |cx| {
-            let worker = cx.boxed(RefCell::new(Some(WorkerHandle { sender: tx })));
-            let tunnel = cx.boxed(tunnel);
-            let retme = cx.empty_object();
-            retme.set(cx, "worker", worker)?;
-            retme.set(cx, "pusher", tunnel)?;
-            Ok(retme)
-        })
-    } else {
-        send_result(channel.clone(), callback, |cx| {
-            Ok(cx.boxed(RefCell::new(Some(WorkerHandle { sender: tx }))))
-        });
-    }
-    UnboundedReceiverStream::new(rx)
-        .for_each_concurrent(None, |request| {
-            let worker = &worker;
-            let channel = channel.clone();
-            async move {
-                match request {
-                    WorkerRequest::InitiateShutdown { callback } => {
-                        worker.initiate_shutdown();
-                        send_result(channel, callback, |cx| Ok(cx.undefined()));
-                    }
-                    WorkerRequest::PollWorkflowActivation { callback } => {
-                        handle_poll_workflow_activation_request(worker, channel, callback).await
-                    }
-                    WorkerRequest::PollActivityTask { callback } => {
-                        handle_poll_activity_task_request(worker, channel, callback).await
-                    }
-                    WorkerRequest::CompleteWorkflowActivation {
-                        completion,
-                        callback,
-                    } => {
-                        void_future_to_js(
-                            channel,
-                            callback,
-                            async move { worker.complete_workflow_activation(completion).await },
-                            |cx, err| -> JsResult<JsObject> {
-                                match err {
-                                    CompleteWfError::MalformedWorkflowCompletion {
-                                        reason, ..
-                                    } => Ok(JsError::type_error(cx, reason)?.upcast()),
-                                }
-                            },
-                        )
-                        .await;
-                    }
-                    WorkerRequest::CompleteActivityTask {
-                        completion,
-                        callback,
-                    } => {
-                        void_future_to_js(
-                            channel,
-                            callback,
-                            async move { worker.complete_activity_task(completion).await },
-                            |cx, err| -> JsResult<JsObject> {
-                                match err {
-                                    CompleteActivityError::MalformedActivityCompletion {
-                                        reason,
-                                        ..
-                                    } => Ok(JsError::type_error(cx, reason)?.upcast()),
-                                }
-                            },
-                        )
-                        .await;
-                    }
-                    WorkerRequest::RecordActivityHeartbeat { heartbeat } => {
-                        worker.record_activity_heartbeat(heartbeat)
+    })
+}
+
+/// Submit a workflow activation completion to core.
+#[js_function]
+pub fn worker_complete_workflow_activation(
+    worker: OpaqueInboundHandle<Worker>,
+    completion: Vec<u8>,
+) -> BridgeResult<BridgeFuture<()>> {
+    let workflow_completion = WorkflowActivationCompletion::decode_length_delimited(
+        completion.as_slice(),
+    )
+    .map_err(|err| BridgeError::TypeError {
+        field: None,
+        message: format!("Cannot decode Completion from buffer: {err:?}"),
+    })?;
+
+    let (runtime, worker) = worker.map_inner(|worker| {
+        (
+            Arc::clone(&worker.core_runtime),
+            Arc::clone(&worker.core_worker),
+        )
+    })?;
+
+    runtime.future_to_promise(async move {
+        worker
+            .complete_workflow_activation(workflow_completion)
+            .await
+            .map_err(|err| match err {
+                CompleteWfError::MalformedWorkflowCompletion { reason, run_id } => {
+                    BridgeError::TypeError {
+                        field: None,
+                        message: format!(
+                            "Malformed Workflow Completion: {reason:?} for RunID={run_id}"
+                        ),
                     }
                 }
-            }
-        })
-        .await;
-    worker.finalize_shutdown().await;
+            })
+    })
 }
 
-/// Called within the poll loop thread, calls core and triggers JS callback with result
-async fn handle_poll_workflow_activation_request(
-    worker: &CoreWorker,
-    channel: Arc<Channel>,
-    callback: Root<JsFunction>,
-) {
-    match worker.poll_workflow_activation().await {
-        Ok(task) => {
-            send_result(channel, callback, move |cx| {
-                let len = task.encoded_len();
-                let mut result = JsArrayBuffer::new(cx, len)?;
-                let mut slice = result.as_mut_slice(cx);
-                if task.encode(&mut slice).is_err() {
-                    panic!("Failed to encode task")
-                };
-                Ok(result)
-            });
-        }
-        Err(err) => {
-            send_error(channel, callback, move |cx| match err {
-                PollError::ShutDown => make_named_error_from_error(cx, SHUTDOWN_ERROR, err),
-                PollError::TonicError(_) => make_named_error_from_error(cx, TRANSPORT_ERROR, err),
-            });
+/// Initiate a single activity task poll request.
+/// There should be only one concurrent poll request for this type.
+#[js_function]
+pub fn worker_poll_activity_task(
+    worker: OpaqueInboundHandle<Worker>,
+) -> BridgeResult<BridgeFuture<Vec<u8>>> {
+    let (runtime, worker) = worker.map_inner(|worker| {
+        (
+            Arc::clone(&worker.core_runtime),
+            Arc::clone(&worker.core_worker),
+        )
+    })?;
+
+    runtime.future_to_promise(async move {
+        let result = worker.poll_activity_task().await;
+
+        match result {
+            Ok(task) => Ok(task.encode_to_vec()),
+            Err(err) => match err {
+                PollError::ShutDown => Err(BridgeError::WorkerShutdown)?,
+                PollError::TonicError(status) => {
+                    Err(BridgeError::TransportError(status.message().to_string()))?
+                }
+            },
         }
-    }
+    })
 }
 
-/// Called within the poll loop thread, calls core and triggers JS callback with result
-pub async fn handle_poll_activity_task_request(
-    worker: &CoreWorker,
-    channel: Arc<Channel>,
-    callback: Root<JsFunction>,
-) {
-    match worker.poll_activity_task().await {
-        Ok(task) => {
-            send_result(channel, callback, move |cx| {
-                let len = task.encoded_len();
-                let mut result = JsArrayBuffer::new(cx, len)?;
-                let mut slice = result.as_mut_slice(cx);
-                if task.encode(&mut slice).is_err() {
-                    panic!("Failed to encode task")
-                };
-                Ok(result)
-            });
-        }
-        Err(err) => {
-            send_error(channel, callback, move |cx| match err {
-                PollError::ShutDown => make_named_error_from_error(cx, SHUTDOWN_ERROR, err),
-                PollError::TonicError(_) => make_named_error_from_error(cx, TRANSPORT_ERROR, err),
-            });
-        }
-    }
+/// Submit an activity task completion to core.
+#[js_function]
+pub fn worker_complete_activity_task(
+    worker: OpaqueInboundHandle<Worker>,
+    completion: Vec<u8>,
+) -> BridgeResult<BridgeFuture<()>> {
+    let activity_completion =
+        ActivityTaskCompletion::decode_length_delimited(completion.as_slice()).map_err(|err| {
+            BridgeError::TypeError {
+                field: None,
+                message: format!("Cannot decode Completion from buffer: {err:?}"),
+            }
+        })?;
+
+    let (runtime, worker) = worker.map_inner(|worker| {
+        (
+            Arc::clone(&worker.core_runtime),
+            Arc::clone(&worker.core_worker),
+        )
+    })?;
+
+    runtime.future_to_promise(async move {
+        worker
+            .complete_activity_task(activity_completion)
+            .await
+            .map_err(|err| match err {
+                CompleteActivityError::MalformedActivityCompletion {
+                    reason,
+                    completion: _,
+                } => BridgeError::TypeError {
+                    field: None,
+                    message: format!("Malformed Activity Completion: {reason:?}"),
+                },
+            })
+    })
 }
 
-// Below are functions exported to JS
+/// Submit an activity heartbeat to core.
+#[js_function]
+pub fn worker_record_activity_heartbeat(
+    worker: OpaqueInboundHandle<Worker>,
+    heartbeat: Vec<u8>,
+) -> BridgeResult<()> {
+    let activity_heartbeat = ActivityHeartbeat::decode_length_delimited(heartbeat.as_slice())
+        .map_err(|err| BridgeError::TypeError {
+            field: None,
+            message: format!("Cannot decode Heartbeat from buffer: {err:?}"),
+        })?;
 
-/// Create a new worker asynchronously.
-/// Worker uses the provided connection and returned to JS using supplied `callback`.
-pub fn worker_new(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let client = cx.argument::<BoxedClient>(0)?;
-    let worker_options = cx.argument::<JsObject>(1)?;
-    let callback = cx.argument::<JsFunction>(2)?;
+    let worker_ref = worker.borrow_inner()?;
+    worker_ref
+        .core_worker
+        .record_activity_heartbeat(activity_heartbeat);
 
-    match client.borrow().as_ref() {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed Client")?;
-        }
-        Some(client) => {
-            let config = worker_options.as_worker_config(&mut cx)?;
-            let request = RuntimeRequest::InitWorker {
-                client: client.core_client.clone(),
-                config,
-                callback: callback.root(&mut cx),
-            };
-            if let Err(err) = client.runtime.sender.send(request) {
-                callback_with_unexpected_error(&mut cx, callback, err)?;
-            };
-        }
+    Ok(())
+}
+
+/// Request shutdown of the worker.
+/// Once complete Core will stop polling on new tasks and activations on worker's task queue.
+/// Caller should drain any pending tasks and activations and call worker_finalize_shutdown before breaking from
+/// the loop to ensure graceful shutdown.
+#[js_function]
+pub fn worker_initiate_shutdown(worker: OpaqueInboundHandle<Worker>) -> BridgeResult<()> {
+    let worker_ref = worker.borrow_inner()?;
+    worker_ref.core_worker.initiate_shutdown();
+    Ok(())
+}
+
+#[js_function]
+pub fn worker_finalize_shutdown(
+    worker: OpaqueInboundHandle<Worker>,
+) -> BridgeResult<BridgeFuture<()>> {
+    let (runtime, worker) = {
+        let worker_ref = worker.take_inner()?;
+        (worker_ref.core_runtime, worker_ref.core_worker)
     };
 
-    Ok(cx.undefined())
+    let worker = Arc::try_unwrap(worker).map_err(|arc| BridgeError::IllegalStateStillInUse {
+        what: "Worker",
+        details: Some(format!(
+            "Expected 1 reference, but got {}",
+            Arc::strong_count(&arc)
+        )),
+    })?;
+
+    runtime.future_to_promise(async move {
+        worker.finalize_shutdown().await;
+        Ok(())
+    })
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+pub struct HistoryForReplayTunnelHandle {
+    core_runtime: Arc<CoreRuntime>,
+    sender: Sender<HistoryForReplay>,
+}
+
+impl HistoryForReplayTunnelHandle {
+    fn new(runtime: &Arc<CoreRuntime>) -> (Self, ReceiverStream<HistoryForReplay>) {
+        let (sender, rx) = channel(1);
+        (
+            Self {
+                core_runtime: Arc::clone(runtime),
+                sender,
+            },
+            ReceiverStream::new(rx),
+        )
+    }
+
+    pub(crate) fn get_chan(&self) -> Sender<HistoryForReplay> {
+        self.sender.clone()
+    }
 }
 
+impl Finalize for HistoryForReplayTunnelHandle {}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
 /// Create a new replay worker asynchronously.
-/// Worker is returned to JS using supplied callback.
-pub fn replay_worker_new(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let runtime = cx.argument::<BoxedRuntime>(0)?;
-    let worker_options = cx.argument::<JsObject>(1)?;
-    let callback = cx.argument::<JsFunction>(2)?;
-
-    let config = worker_options.as_worker_config(&mut cx)?;
-    let request = RuntimeRequest::InitReplayWorker {
-        runtime: (*runtime).clone(),
-        config,
-        callback: callback.root(&mut cx),
-    };
-    if let Err(err) = runtime.sender.send(request) {
-        callback_with_unexpected_error(&mut cx, callback, err)?;
+#[js_function]
+pub fn replay_worker_new(
+    runtime: OpaqueInboundHandle<Runtime>,
+    config: config::BridgeWorkerOptions,
+) -> BridgeResult<(
+    OpaqueOutboundHandle<Worker>,
+    OpaqueOutboundHandle<HistoryForReplayTunnelHandle>,
+)> {
+    let config = config
+        .into_core_config()
+        .context("Failed to convert WorkerOptions to CoreWorkerConfig")?;
+
+    let runtime = runtime.borrow_inner()?.core_runtime.clone();
+    enter_sync!(runtime);
+
+    let (tunnel, stream) = HistoryForReplayTunnelHandle::new(&runtime);
+
+    let worker = init_replay_worker(ReplayWorkerInput::new(config, Box::pin(stream)))
+        .context("Failed to initialize replay worker")?;
+
+    let worker_handle = Worker {
+        core_runtime: runtime,
+        core_worker: Arc::new(worker),
     };
 
-    Ok(cx.undefined())
+    Ok((
+        OpaqueOutboundHandle::new(worker_handle),
+        OpaqueOutboundHandle::new(tunnel),
+    ))
 }
 
-pub fn push_history(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let pusher = cx.argument::<JsBox<HistoryForReplayTunnel>>(0)?;
-    let workflow_id = cx.argument::<JsString>(1)?;
-    let history_binary = cx.argument::<JsArrayBuffer>(2)?;
-    let callback = cx.argument::<JsFunction>(3)?;
-    let data = history_binary.as_slice(&cx);
-    match History::decode_length_delimited(data) {
-        Ok(hist) => {
-            let workflow_id = workflow_id.value(&mut cx);
-            if let Err(e) = pusher.get_chan().map(|chan| {
-                pusher
-                    .runtime
-                    .sender
-                    .send(RuntimeRequest::PushReplayHistory {
-                        tx: chan,
-                        pushme: HistoryForReplay::new(hist, workflow_id),
-                        callback: callback.root(&mut cx),
-                    })
-            }) {
-                callback_with_unexpected_error(&mut cx, callback, e)?;
+#[js_function]
+pub fn push_history(
+    pusher: OpaqueInboundHandle<HistoryForReplayTunnelHandle>,
+    workflow_id: String,
+    history_binary: Vec<u8>,
+) -> BridgeResult<BridgeFuture<()>> {
+    let history: History =
+        History::decode_length_delimited(history_binary.as_slice()).map_err(|err| {
+            BridgeError::TypeError {
+                field: None,
+                message: format!("Cannot decode History from buffer: {err:?}"),
             }
-            Ok(cx.undefined())
-        }
-        Err(e) => cx.throw_error(format!("Error decoding history: {:?}", e)),
-    }
+        })?;
+    let history = HistoryForReplay::new(history, workflow_id);
+
+    let pusher_ref = pusher.borrow_inner()?;
+    let chan = pusher_ref.get_chan();
+
+    pusher_ref.core_runtime.future_to_promise(async move {
+        chan.send(history)
+            .await
+            .context("Error pushing history to replay worker")?;
+        Ok(())
+    })
 }
 
-pub fn close_history_stream(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let pusher = cx.argument::<JsBox<HistoryForReplayTunnel>>(0)?;
-    pusher.shutdown();
-    Ok(cx.undefined())
+#[js_function]
+pub fn close_history_stream(
+    pusher: OpaqueInboundHandle<HistoryForReplayTunnelHandle>,
+) -> BridgeResult<()> {
+    // Just drop the pusher's channel; there's actually no "close" method on the channel.
+    let _pusher_ref = pusher.take_inner()?;
+    Ok(())
 }
 
-/// Initiate a single workflow activation poll request.
-/// There should be only one concurrent poll request for this type.
-pub fn worker_poll_workflow_activation(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let worker = cx.argument::<BoxedWorker>(0)?;
-    let callback = cx.argument::<JsFunction>(1)?;
-    match worker.borrow().as_ref() {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed Worker")?;
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+mod config {
+    use std::{sync::Arc, time::Duration};
+
+    use temporal_sdk_core::{
+        ResourceBasedSlotsOptions, ResourceBasedSlotsOptionsBuilder, ResourceSlotOptions,
+        SlotSupplierOptions as CoreSlotSupplierOptions, TunerHolder, TunerHolderOptionsBuilder,
+        api::worker::{
+            ActivitySlotKind, LocalActivitySlotKind, PollerBehavior, SlotKind, WorkerConfig,
+            WorkerConfigBuilder, WorkerConfigBuilderError, WorkflowSlotKind,
+        },
+    };
+
+    use bridge_macros::TryFromJs;
+
+    use super::custom_slot_supplier::CustomSlotSupplierOptions;
+
+    #[derive(TryFromJs)]
+    pub struct BridgeWorkerOptions {
+        identity: String,
+        build_id: String,
+        use_versioning: bool,
+        task_queue: String,
+        namespace: String,
+        tuner: WorkerTuner,
+        non_sticky_to_sticky_poll_ratio: f32,
+        max_concurrent_workflow_task_polls: usize,
+        max_concurrent_activity_task_polls: usize,
+        enable_non_local_activities: bool,
+        sticky_queue_schedule_to_start_timeout: Duration,
+        max_cached_workflows: usize,
+        max_heartbeat_throttle_interval: Duration,
+        default_heartbeat_throttle_interval: Duration,
+        max_activities_per_second: Option<f64>,
+        max_task_queue_activities_per_second: Option<f64>,
+        shutdown_grace_time: Option<Duration>,
+    }
+
+    impl BridgeWorkerOptions {
+        pub(crate) fn into_core_config(self) -> Result<WorkerConfig, WorkerConfigBuilderError> {
+            // Set all other options
+            let mut builder = WorkerConfigBuilder::default();
+            builder
+                .client_identity_override(Some(self.identity))
+                .worker_build_id(self.build_id)
+                .use_worker_versioning(self.use_versioning)
+                .task_queue(self.task_queue)
+                .namespace(self.namespace)
+                .tuner(self.tuner.into_core_config()?)
+                .nonsticky_to_sticky_poll_ratio(self.non_sticky_to_sticky_poll_ratio)
+                .workflow_task_poller_behavior(PollerBehavior::SimpleMaximum(
+                    self.max_concurrent_workflow_task_polls,
+                ))
+                .activity_task_poller_behavior(PollerBehavior::SimpleMaximum(
+                    self.max_concurrent_activity_task_polls,
+                ))
+                .no_remote_activities(!self.enable_non_local_activities)
+                .sticky_queue_schedule_to_start_timeout(self.sticky_queue_schedule_to_start_timeout)
+                .max_cached_workflows(self.max_cached_workflows)
+                .max_heartbeat_throttle_interval(self.max_heartbeat_throttle_interval)
+                .default_heartbeat_throttle_interval(self.default_heartbeat_throttle_interval)
+                .max_task_queue_activities_per_second(self.max_task_queue_activities_per_second)
+                .max_worker_activities_per_second(self.max_activities_per_second)
+                .graceful_shutdown_period(self.shutdown_grace_time)
+                .build()
         }
-        Some(worker) => {
-            let request = WorkerRequest::PollWorkflowActivation {
-                callback: callback.root(&mut cx),
-            };
-            if let Err(err) = worker.sender.send(request) {
-                callback_with_unexpected_error(&mut cx, callback, err)?;
+    }
+
+    #[derive(TryFromJs)]
+    #[allow(clippy::struct_field_names)]
+    pub(super) struct WorkerTuner {
+        workflow_task_slot_supplier: SlotSupplier<WorkflowSlotKind>,
+        activity_task_slot_supplier: SlotSupplier<ActivitySlotKind>,
+        local_activity_task_slot_supplier: SlotSupplier<LocalActivitySlotKind>,
+    }
+
+    impl WorkerTuner {
+        fn into_core_config(self) -> Result<Arc<TunerHolder>, String> {
+            let mut tuner_holder = TunerHolderOptionsBuilder::default();
+            let mut rbo = None;
+
+            tuner_holder.workflow_slot_options(
+                self.workflow_task_slot_supplier
+                    .into_slot_supplier(&mut rbo),
+            );
+            tuner_holder.activity_slot_options(
+                self.activity_task_slot_supplier
+                    .into_slot_supplier(&mut rbo),
+            );
+            tuner_holder.local_activity_slot_options(
+                self.local_activity_task_slot_supplier
+                    .into_slot_supplier(&mut rbo),
+            );
+            if let Some(rbo) = rbo {
+                tuner_holder.resource_based_options(rbo);
             }
+
+            tuner_holder
+                .build_tuner_holder()
+                .map(Arc::new)
+                .map_err(|e| format!("Invalid tuner options: {e:?}"))
         }
     }
-    Ok(cx.undefined())
-}
 
-/// Initiate a single activity task poll request.
-/// There should be only one concurrent poll request for this type.
-pub fn worker_poll_activity_task(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let worker = cx.argument::<BoxedWorker>(0)?;
-    let callback = cx.argument::<JsFunction>(1)?;
-    match worker.borrow().as_ref() {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed Worker")?;
-        }
-        Some(worker) => {
-            let request = WorkerRequest::PollActivityTask {
-                callback: callback.root(&mut cx),
-            };
-            if let Err(err) = worker.sender.send(request) {
-                callback_with_unexpected_error(&mut cx, callback, err)?;
+    #[derive(TryFromJs)]
+    pub(super) enum SlotSupplier<SK: SlotKind + Send + Sync + 'static> {
+        FixedSize(FixedSizeSlotSupplierOptions),
+        ResourceBased(ResourceBasedSlotSupplierOptions),
+        Custom(CustomSlotSupplierOptions<SK>),
+    }
+
+    #[derive(TryFromJs)]
+    pub(super) struct FixedSizeSlotSupplierOptions {
+        num_slots: usize,
+    }
+
+    #[derive(TryFromJs)]
+    pub(super) struct ResourceBasedSlotSupplierOptions {
+        minimum_slots: usize,
+        maximum_slots: usize,
+        ramp_throttle: Duration,
+        tuner_options: ResourceBasedTunerOptions,
+    }
+
+    #[derive(TryFromJs)]
+    pub(super) struct ResourceBasedTunerOptions {
+        target_memory_usage: f64,
+        target_cpu_usage: f64,
+    }
+
+    impl<SK: SlotKind + Send + Sync + 'static> SlotSupplier<SK> {
+        fn into_slot_supplier(
+            self,
+            rbo: &mut Option<ResourceBasedSlotsOptions>,
+        ) -> CoreSlotSupplierOptions<SK> {
+            match self {
+                Self::FixedSize(opts) => CoreSlotSupplierOptions::FixedSize {
+                    slots: opts.num_slots,
+                },
+                Self::ResourceBased(opts) => {
+                    *rbo = Some(
+                        ResourceBasedSlotsOptionsBuilder::default()
+                            .target_cpu_usage(opts.tuner_options.target_cpu_usage)
+                            .target_mem_usage(opts.tuner_options.target_memory_usage)
+                            .build()
+                            .expect("Building ResourceBasedSlotsOptions can't fail"),
+                    );
+                    CoreSlotSupplierOptions::ResourceBased(ResourceSlotOptions::new(
+                        opts.minimum_slots,
+                        opts.maximum_slots,
+                        opts.ramp_throttle,
+                    ))
+                }
+                Self::Custom(opts) => CoreSlotSupplierOptions::Custom(Arc::new(
+                    super::custom_slot_supplier::SlotSupplierBridge::new(opts),
+                )),
             }
         }
     }
-    Ok(cx.undefined())
 }
 
-/// Submit a workflow activation completion to core.
-pub fn worker_complete_workflow_activation(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let worker = cx.argument::<BoxedWorker>(0)?;
-    let completion = cx.argument::<JsArrayBuffer>(1)?;
-    let callback = cx.argument::<JsFunction>(2)?;
-    match worker.borrow().as_ref() {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed Worker")?;
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+mod custom_slot_supplier {
+    use std::{marker::PhantomData, sync::Arc};
+
+    use neon::{context::Context, handle::Handle, prelude::*};
+
+    use temporal_sdk_core::{
+        SlotSupplierOptions as CoreSlotSupplierOptions,
+        api::worker::{
+            SlotInfo as CoreSlotInfo, SlotInfoTrait as _, SlotKind,
+            SlotKindType as CoreSlotKindType, SlotMarkUsedContext as CoreSlotMarkUsedContext,
+            SlotReleaseContext as CoreSlotReleaseContext,
+            SlotReservationContext as CoreSlotReservationContext, SlotSupplier as CoreSlotSupplier,
+            SlotSupplierPermit as CoreSlotSupplierPermit,
+        },
+    };
+
+    use bridge_macros::{TryFromJs, TryIntoJs};
+
+    use crate::helpers::*;
+
+    // Custom Slot Supplier ////////////////////////////////////////////////////////////////////////////
+
+    pub(super) struct SlotSupplierBridge<SK: SlotKind + Send + Sync + 'static> {
+        options: CustomSlotSupplierOptions<SK>,
+    }
+
+    impl<SK: SlotKind + Send + Sync + 'static> SlotSupplierBridge<SK> {
+        pub(crate) const fn new(options: CustomSlotSupplierOptions<SK>) -> Self {
+            Self { options }
         }
-        Some(worker) => {
-            match WorkflowActivationCompletion::decode_length_delimited(completion.as_slice(&cx)) {
-                Ok(completion) => {
-                    let request = WorkerRequest::CompleteWorkflowActivation {
-                        completion,
-                        callback: callback.root(&mut cx),
-                    };
-                    if let Err(err) = worker.sender.send(request) {
-                        callback_with_unexpected_error(&mut cx, callback, err)?;
-                    };
+    }
+
+    #[async_trait::async_trait]
+    impl<SK: SlotKind + Send + Sync + 'static> CoreSlotSupplier for SlotSupplierBridge<SK> {
+        type SlotKind = SK;
+
+        async fn reserve_slot(
+            &self,
+            ctx: &dyn CoreSlotReservationContext,
+        ) -> CoreSlotSupplierPermit {
+            loop {
+                let reserve_ctx = SlotReserveContext {
+                    slot_type: SK::kind().into(),
+                    task_queue: ctx.task_queue().to_string(),
+                    worker_identity: ctx.worker_identity().to_string(),
+                    worker_build_id: ctx.worker_build_id().to_string(),
+                    is_sticky: ctx.is_sticky(),
+                };
+
+                let (_abort_controller, abort_signal) =
+                    AbortController::new("Request Cancelled".to_string());
+
+                let permit_result = self
+                    .options
+                    .reserve_slot
+                    .call((reserve_ctx, abort_signal))
+                    .await;
+
+                match permit_result {
+                    Ok(permit) => {
+                        return CoreSlotSupplierPermit::with_user_data(BridgePermitData {
+                            permit: Arc::new(permit),
+                        });
+                    }
+                    Err(err) => {
+                        log::warn!("Error reserving slot: {err:?}");
+                        tokio::time::sleep(std::time::Duration::from_millis(1000)).await;
+                        continue;
+                    }
                 }
-                Err(_) => callback_with_error(&mut cx, callback, |cx| {
-                    JsError::type_error(cx, "Cannot decode Completion from buffer")
-                })?,
             }
         }
-    };
-    Ok(cx.undefined())
-}
 
-/// Submit an activity task completion to core.
-pub fn worker_complete_activity_task(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let worker = cx.argument::<BoxedWorker>(0)?;
-    let result = cx.argument::<JsArrayBuffer>(1)?;
-    let callback = cx.argument::<JsFunction>(2)?;
-    match worker.borrow().as_ref() {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed Worker")?;
-        }
-        Some(worker) => {
-            match ActivityTaskCompletion::decode_length_delimited(result.as_slice(&cx)) {
-                Ok(completion) => {
-                    let request = WorkerRequest::CompleteActivityTask {
-                        completion,
-                        callback: callback.root(&mut cx),
-                    };
-                    if let Err(err) = worker.sender.send(request) {
-                        callback_with_unexpected_error(&mut cx, callback, err)?;
-                    };
+        fn try_reserve_slot(
+            &self,
+            ctx: &dyn CoreSlotReservationContext,
+        ) -> Option<CoreSlotSupplierPermit> {
+            let tokio_runtime = tokio::runtime::Handle::current();
+            let _entered = tokio_runtime.enter();
+
+            let reserve_ctx = SlotReserveContext {
+                slot_type: SK::kind().into(),
+                task_queue: ctx.task_queue().to_string(),
+                worker_identity: ctx.worker_identity().to_string(),
+                worker_build_id: ctx.worker_build_id().to_string(),
+                is_sticky: ctx.is_sticky(),
+            };
+
+            // Try to reserve slot synchronously
+            let result = self.options.try_reserve_slot.call_and_block((reserve_ctx,));
+
+            match result {
+                Ok(res) => res.map(|permit| {
+                    CoreSlotSupplierPermit::with_user_data(BridgePermitData {
+                        permit: Arc::new(permit),
+                    })
+                }),
+                Err(err) => {
+                    log::warn!("Error reserving {} slot: {:?}", SK::kind(), err);
+                    None
                 }
-                Err(_) => callback_with_error(&mut cx, callback, |cx| {
-                    JsError::type_error(cx, "Cannot decode Completion from buffer")
-                })?,
             }
         }
-    };
-    Ok(cx.undefined())
-}
 
-/// Submit an activity heartbeat to core.
-pub fn worker_record_activity_heartbeat(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let worker = cx.argument::<BoxedWorker>(0)?;
-    let heartbeat = cx.argument::<JsArrayBuffer>(1)?;
-    match worker.borrow().as_ref() {
-        None => {
-            make_named_error_from_string(&mut cx, UNEXPECTED_ERROR, "Tried to use closed Worker")
-                .and_then(|err| cx.throw(err))?
+        fn mark_slot_used(&self, ctx: &dyn CoreSlotMarkUsedContext<SlotKind = Self::SlotKind>) {
+            let tokio_runtime = tokio::runtime::Handle::current();
+            let _entered = tokio_runtime.enter();
+
+            let permit_data = ctx
+                .permit()
+                .user_data::<BridgePermitData>()
+                .expect("Expected BridgePermitData in mark_slot_used");
+
+            let slot_info = SlotInfo::from(&ctx.info().downcast());
+
+            // Fire and forget call to mark_slot_used
+            let _ = self
+                .options
+                .mark_slot_used
+                .call_on_js_thread((SlotMarkUsedContext::<SK> {
+                    slot_info,
+                    permit: permit_data.permit.clone(),
+                    _marker: PhantomData,
+                },));
         }
-        Some(worker) => match ActivityHeartbeat::decode_length_delimited(heartbeat.as_slice(&cx)) {
-            Ok(heartbeat) => {
-                let request = WorkerRequest::RecordActivityHeartbeat { heartbeat };
-                if let Err(err) = worker.sender.send(request) {
-                    make_named_error_from_error(&mut cx, UNEXPECTED_ERROR, err)
-                        .and_then(|err| cx.throw(err))?;
-                }
-            }
-            Err(_) => cx.throw_type_error("Cannot decode ActivityHeartbeat from buffer")?,
+
+        fn release_slot(&self, ctx: &dyn CoreSlotReleaseContext<SlotKind = Self::SlotKind>) {
+            let tokio_runtime = tokio::runtime::Handle::current();
+            let _entered = tokio_runtime.enter();
+
+            let permit_data = ctx
+                .permit()
+                .user_data::<BridgePermitData>()
+                .expect("Expected BridgePermitData in release_slot");
+
+            let slot_info = ctx.info().map(|info| SlotInfo::from(&info.downcast()));
+
+            // Fire and forget call to release_slot
+            let _ = self
+                .options
+                .release_slot
+                .call_on_js_thread((SlotReleaseContext::<SK> {
+                    slot_info,
+                    permit: permit_data.permit.clone(),
+                    _marker: PhantomData,
+                },));
+        }
+    }
+
+    #[derive(TryFromJs)]
+    pub(super) struct CustomSlotSupplierOptions<SK: SlotKind + Send + Sync + 'static> {
+        reserve_slot: JsAsyncCallback<(SlotReserveContext, AbortSignal), SlotPermitOpaqueData>,
+        try_reserve_slot: JsCallback<(SlotReserveContext,), Option<SlotPermitOpaqueData>>,
+        mark_slot_used: JsCallback<(SlotMarkUsedContext<SK>,), ()>,
+        release_slot: JsCallback<(SlotReleaseContext<SK>,), ()>,
+    }
+
+    impl<SK: SlotKind + Send + Sync + 'static> TryInto<CoreSlotSupplierOptions<SK>>
+        for CustomSlotSupplierOptions<SK>
+    {
+        type Error = BridgeError;
+
+        fn try_into(self) -> Result<CoreSlotSupplierOptions<SK>, Self::Error> {
+            Ok(CoreSlotSupplierOptions::Custom(Arc::new(
+                SlotSupplierBridge { options: self },
+            )))
+        }
+    }
+
+    #[derive(TryIntoJs)]
+    enum SlotInfo {
+        Workflow {
+            workflow_type: String,
+            is_sticky: bool,
         },
-    };
-    Ok(cx.undefined())
-}
+        Activity {
+            activity_type: String,
+        },
+        LocalActivity {
+            activity_type: String,
+        },
+        Nexus {
+            service: String,
+            operation: String,
+        },
+    }
 
-/// Request shutdown of the worker.
-/// Once complete Core will stop polling on new tasks and activations on worker's task queue.
-/// Caller should drain any pending tasks and activations and call worker_finalize_shutdown before breaking from
-/// the loop to ensure graceful shutdown.
-pub fn worker_initiate_shutdown(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let worker = cx.argument::<BoxedWorker>(0)?;
-    let callback = cx.argument::<JsFunction>(1)?;
-    match worker.borrow().as_ref() {
-        None => {
-            callback_with_unexpected_error(&mut cx, callback, "Tried to use closed Worker")?;
+    impl<'a> From<&'a CoreSlotInfo<'a>> for SlotInfo {
+        fn from(info: &'a CoreSlotInfo<'a>) -> Self {
+            match info {
+                CoreSlotInfo::Workflow(info) => Self::Workflow {
+                    workflow_type: info.workflow_type.to_string(),
+                    is_sticky: info.is_sticky,
+                },
+                CoreSlotInfo::Activity(info) => Self::Activity {
+                    activity_type: info.activity_type.to_string(),
+                },
+                CoreSlotInfo::LocalActivity(info) => Self::LocalActivity {
+                    activity_type: info.activity_type.to_string(),
+                },
+                CoreSlotInfo::Nexus(info) => Self::Nexus {
+                    service: info.service.to_string(),
+                    operation: info.operation.to_string(),
+                },
+            }
         }
-        Some(worker) => {
-            if let Err(err) = worker.sender.send(WorkerRequest::InitiateShutdown {
-                callback: callback.root(&mut cx),
-            }) {
-                make_named_error_from_error(&mut cx, UNEXPECTED_ERROR, err)
-                    .and_then(|err| cx.throw(err))?;
+    }
+
+    #[derive(TryIntoJs)]
+    struct SlotReserveContext {
+        slot_type: SlotKindType,
+        task_queue: String,
+        worker_identity: String,
+        worker_build_id: String,
+        is_sticky: bool,
+    }
+
+    #[derive(TryIntoJs)]
+    struct SlotMarkUsedContext<SK: SlotKind> {
+        slot_info: SlotInfo,
+        permit: Arc<SlotPermitOpaqueData>,
+        _marker: PhantomData<SK>,
+    }
+
+    #[derive(TryIntoJs)]
+    struct SlotReleaseContext<SK: SlotKind> {
+        slot_info: Option<SlotInfo>,
+        permit: Arc<SlotPermitOpaqueData>,
+        _marker: PhantomData<SK>,
+    }
+
+    enum SlotKindType {
+        Workflow,
+        Activity,
+        LocalActivity,
+        Nexus,
+    }
+
+    // FIXME: Anyway we could get this auto-generated from CoreSlotKindType?
+    impl TryIntoJs for SlotKindType {
+        type Output = JsString;
+        fn try_into_js<'cx>(self, cx: &mut impl Context<'cx>) -> JsResult<'cx, JsString> {
+            let s = match self {
+                Self::Workflow => "workflow",
+                Self::Activity => "activity",
+                Self::LocalActivity => "local-activity",
+                Self::Nexus => "nexus",
             };
+            Ok(cx.string(s))
         }
     }
-    Ok(cx.undefined())
-}
 
-pub fn worker_finalize_shutdown(mut cx: FunctionContext) -> JsResult<JsUndefined> {
-    let worker = cx.argument::<BoxedWorker>(0)?;
-    if worker.replace(None).is_none() {
-        make_named_error_from_string(&mut cx, ILLEGAL_STATE_ERROR, "Worker already closed")
-            .and_then(|err| cx.throw(err))?;
+    impl From<CoreSlotKindType> for SlotKindType {
+        fn from(val: CoreSlotKindType) -> Self {
+            match val {
+                CoreSlotKindType::Workflow => Self::Workflow,
+                CoreSlotKindType::Activity => Self::Activity,
+                CoreSlotKindType::LocalActivity => Self::LocalActivity,
+                CoreSlotKindType::Nexus => Self::Nexus,
+            }
+        }
     }
 
-    Ok(cx.undefined())
+    /// `BridgePermitData` holds the data associated with a slot permit.
+    struct BridgePermitData {
+        permit: Arc<SlotPermitOpaqueData>,
+    }
+
+    /// An opaque handle to a root'd JS object.
+    ///
+    /// Note that even though the public API allows `permit` to be any JS value, including
+    /// `undefined` or `null`, we may in fact only root JS _objects_ (including arrays and
+    /// functions, but not primitives). For that reason, we wrap the user's JS value in a
+    /// `JSObject`, and root that object instead.
+    struct SlotPermitOpaqueData(Root<JsObject>);
+
+    static PERMIT_DATA_FIELD: &str = "permit_data";
+
+    impl TryFromJs for SlotPermitOpaqueData {
+        fn try_from_js<'cx, 'b>(
+            cx: &mut impl Context<'cx>,
+            js_value: Handle<'b, JsValue>,
+        ) -> BridgeResult<Self> {
+            let obj = cx.empty_object();
+            obj.set(cx, PERMIT_DATA_FIELD, js_value)?;
+            Ok(Self(obj.root(cx)))
+        }
+    }
+
+    impl TryIntoJs for Arc<SlotPermitOpaqueData> {
+        type Output = JsValue;
+        fn try_into_js<'a>(self, cx: &mut impl Context<'a>) -> JsResult<'a, JsValue> {
+            let obj = self.as_ref().0.to_inner(cx);
+            obj.get_value(cx, PERMIT_DATA_FIELD)
+        }
+    }
 }
diff --git a/packages/core-bridge/ts/index.ts b/packages/core-bridge/ts/index.ts
index e4ab77eaf..2c44599fd 100644
--- a/packages/core-bridge/ts/index.ts
+++ b/packages/core-bridge/ts/index.ts
@@ -1,628 +1,18 @@
-import { LogLevel, Duration, SearchAttributeType } from '@temporalio/common';
-import type { TLSConfig, ProxyConfig, HttpConnectProxyConfig } from '@temporalio/common/lib/internal-non-workflow';
-import { WorkerTuner } from './worker-tuner';
-import { SearchAttributeKey } from '@temporalio/common/src/search-attributes';
+import * as native from './native';
+import * as errors from './errors';
 
 export {
-  WorkerTuner,
-  SlotSupplier,
-  ResourceBasedSlotOptions,
-  ResourceBasedTunerOptions,
-  FixedSizeSlotSupplier,
-  CustomSlotSupplier,
-  SlotInfo,
-  WorkflowSlotInfo,
-  ActivitySlotInfo,
-  LocalActivitySlotInfo,
-  SlotMarkUsedContext,
-  SlotPermit,
-  SlotReserveContext,
-  SlotReleaseContext,
-} from './worker-tuner';
-
-export type { TLSConfig, ProxyConfig, HttpConnectProxyConfig };
-
-/** @deprecated Import from @temporalio/common instead */
-export { LogLevel };
-
-export interface RetryOptions {
-  /** Initial wait time before the first retry. */
-  initialInterval: number;
   /**
-   * Randomization jitter that is used as a multiplier for the current retry interval
-   * and is added or subtracted from the interval length.
+   * @internal This module is not intended to be used directly. Any API provided
+   *           by this package is internal and subject to change without notice.
+   * @hidden
    */
-  randomizationFactor: number;
-  /** Rate at which retry time should be increased, until it reaches max_interval. */
-  multiplier: number;
-  /** Maximum amount of time to wait between retries. */
-  maxInterval: number;
-  /** Maximum total amount of time requests should be retried for, if None is set then no limit will be used. */
-  maxElapsedTime?: number;
-  /** Maximum number of retry attempts. */
-  maxRetries: number;
-}
+  native,
 
-export interface ClientOptions {
   /**
-   * The URL of the Temporal server to connect to
+   * @internal This module is not intended to be used directly. Any API provided
+   *           by this package is internal and subject to change without notice.
+   * @hidden
    */
-  url: string;
-
-  /** Version string for the whole node SDK. Should never be set by user */
-  sdkVersion: string;
-
-  /**
-   * TLS configuration options.
-   *
-   * Pass undefined to use a non-encrypted connection or an empty object to
-   * connect with TLS without any customization.
-   */
-  tls?: TLSConfig;
-
-  /**
-   * Proxying configuration.
-   */
-  proxy?: ProxyConfig;
-
-  /**
-   * Optional retry options for server requests.
-   */
-  retry?: RetryOptions;
-
-  /**
-   * Optional mapping of gRPC metadata (HTTP headers) to send with each request to the server.
-   *
-   * Set statically at connection time, can be replaced later using {@link clientUpdateHeaders}.
-   */
-  metadata?: Record<string, string>;
-
-  /**
-   * API key for Temporal. This becomes the "Authorization" HTTP header with "Bearer " prepended.
-   * This is only set if RPC metadata doesn't already have an "authorization" key.
-   *
-   * Set statically at connection time, can be replaced later using {@link clientUpdateApiKey}.
-   */
-  apiKey?: string;
-
-  /**
-   * If set to true, error code labels will not be included on request failure
-   * metrics emitted by this Client.
-   *
-   * @default false
-   */
-  disableErrorCodeMetricTags?: boolean;
-}
-
-/**
- * Log directly to console
- */
-export interface ConsoleLogger {
-  console: {}; // eslint-disable-line @typescript-eslint/no-empty-object-type
-}
-
-/**
- * Forward logs to {@link Runtime} logger
- */
-export interface ForwardLogger {
-  forward: {
-    /**
-     * What level, if any, logs should be forwarded from core at
-     *
-     * @deprecated Use {@link TelemetryOptions.logging.filter} instead
-     */
-    level?: LogLevel;
-  };
-}
-
-/**
- * Logger types supported by Core
- */
-export type Logger = ConsoleLogger | ForwardLogger;
-
-/**
- * OpenTelemetry Collector options for exporting metrics or traces
- */
-export interface OtelCollectorExporter {
-  otel: {
-    /**
-     * URL of a gRPC OpenTelemetry collector.
-     *
-     * Syntax generally looks like `http://server:4317` or `grpc://server:4317` for OTLP/gRPC exporters,
-     * or `http://server:4318/v1/metrics` for OTLP/HTTP exporters. Make sure to set the `http` option
-     * to `true` for OTLP/HTTP endpoints.
-     *
-     * @format Starts with "grpc://" or "http://" for an unsecured connection (typical),
-     *         or "grpcs://" or "https://" for a TLS connection.
-     * @note The `OTEL_EXPORTER_OTLP_ENDPOINT` environment variable, if set, will override this property.
-     */
-    url: string;
-
-    /**
-     * If set to true, the exporter will use OTLP/HTTP instead of OTLP/gRPC.
-     *
-     * @default false meaning that the exporter will use OTLP/gRPC.
-     */
-    http?: boolean;
-
-    /**
-     * Optional set of HTTP request headers to send to Collector (e.g. for authentication)
-     */
-    headers?: Record<string, string>;
-
-    /**
-     * Specify how frequently in metrics should be exported.
-     *
-     * @format number of milliseconds or {@link https://www.npmjs.com/package/ms | ms-formatted string}
-     * @default 1 second
-     */
-    metricsExportInterval?: Duration;
-
-    /**
-     * If set to true, the exporter will use seconds for durations instead of milliseconds.
-     *
-     * @default false
-     */
-    useSecondsForDurations?: boolean;
-
-    /**
-     * Determines if the metrics exporter should use cumulative or delta temporality.
-
-     * See the [OpenTelemetry specification](https://github.com/open-telemetry/opentelemetry-specification/blob/ce50e4634efcba8da445cc23523243cb893905cb/specification/metrics/datamodel.md#temporality)
-     * for more information.
-     *
-     * @default 'cumulative'
-     */
-    temporality?: 'cumulative' | 'delta';
-
-    /**
-     * Overrides boundary values for histogram metrics.
-     *
-     * The key is the metric name and the value is the list of bucket boundaries.
-     *
-     * For example:
-     *
-     * ```
-     * {
-     *   "request_latency": [1, 5, 10, 25, 50, 100, 250, 500, 1000],
-     * }
-     * ```
-     *
-     * The metric name will apply regardless of name prefixing.
-     *
-     * See [this doc](https://docs.rs/opentelemetry_sdk/latest/opentelemetry_sdk/metrics/enum.Aggregation.html#variant.ExplicitBucketHistogram.field.boundaries)
-     * for the exact meaning of boundaries.
-     */
-    histogramBucketOverrides?: Record<string, number[]>;
-  };
-}
-
-interface CompiledOtelMetricsExporter {
-  otel: {
-    url: string;
-    http: boolean;
-    headers: Record<string, string> | undefined;
-    metricsExportInterval: number;
-    useSecondsForDurations: boolean;
-    temporality: 'cumulative' | 'delta';
-    histogramBucketOverrides: Record<string, number[]> | undefined;
-  };
-}
-
-/**
- * Prometheus metrics exporter options
- */
-export interface PrometheusMetricsExporter {
-  prometheus: {
-    /**
-     * Address to bind the Prometheus HTTP metrics exporter server
-     * (for example, `0.0.0.0:1234`).
-     *
-     * Metrics will be available for scraping under the standard `/metrics` route.
-     */
-    bindAddress: string;
-    /**
-     * If set to true, all counter names will include a "_total" suffix.
-     *
-     * @default false
-     */
-    countersTotalSuffix?: boolean;
-    /**
-     * If set to true, all histograms will include the unit in their name as a suffix.
-     * EX: "_milliseconds"
-     *
-     * @default false
-     */
-    unitSuffix?: boolean;
-    /**
-     * If set to true, the exporter will use seconds for durations instead of milliseconds.
-     *
-     * @default false
-     */
-    useSecondsForDurations?: boolean;
-
-    /**
-     * Overrides boundary values for histogram metrics.
-     *
-     * The key is the metric name and the value is the list of bucket boundaries.
-     *
-     * For example:
-     *
-     * ```
-     * {
-     *   "request_latency": [1, 5, 10, 25, 50, 100, 250, 500, 1000],
-     * }
-     * ```
-     *
-     * The metric name will apply regardless of name prefixing.
-     *
-     * See [this doc](https://docs.rs/opentelemetry_sdk/latest/opentelemetry_sdk/metrics/enum.Aggregation.html#variant.ExplicitBucketHistogram.field.boundaries)
-     * for the exact meaning of boundaries.
-     */
-    histogramBucketOverrides?: Record<string, number[]>;
-  };
-}
-
-interface CompiledPrometheusMetricsExporter {
-  prometheus: {
-    bindAddress: string;
-    countersTotalSuffix: boolean;
-    unitSuffix: boolean;
-    useSecondsForDurations: boolean;
-    histogramBucketOverrides: Record<string, number[]> | undefined;
-  };
-}
-
-/**
- * Metrics exporters supported by Core
- */
-export type MetricsExporter = {
-  /**
-   * Determines if the metrics exporter should use cumulative or delta temporality.
-   * Only applies to OpenTelemetry exporter.
-   *
-   * @deprecated Use 'otel.temporality' instead
-   */
-  temporality?: 'cumulative' | 'delta';
-
-  /**
-   * A prefix to add to all metrics.
-   *
-   * @default 'temporal_'
-   */
-  metricPrefix?: string;
-
-  /**
-   * Tags to add to all metrics emitted by the worker.
-   */
-  globalTags?: Record<string, string>;
-
-  /**
-   * Whether to put the service_name on every metric.
-   *
-   * @default true
-   */
-  attachServiceName?: boolean;
-} & (PrometheusMetricsExporter | OtelCollectorExporter);
-
-export interface TelemetryOptions {
-  /**
-   * A string in the env filter format specified here:
-   * https://docs.rs/tracing-subscriber/0.2.20/tracing_subscriber/struct.EnvFilter.html
-   *
-   * Which determines what tracing data is collected in the Core SDK.
-   *
-   * @deprecated Use `logging.filter` instead
-   */
-  tracingFilter?: string;
-
-  /**
-   * If set true, do not prefix metrics with `temporal_`.
-   *
-   * @deprecated Use `metrics.metricPrefix` instead
-   */
-  noTemporalPrefixForMetrics?: boolean;
-
-  /**
-   * Control where to send Rust Core logs
-   */
-  logging?: {
-    /**
-     * A string in (env filter format)[https://docs.rs/tracing-subscriber/0.2.20/tracing_subscriber/struct.EnvFilter.html]
-     * which determines the verboseness of logging output.
-     *
-     * You can use {@link Runtime.makeTelemetryFilterString()} to easily build a correctly formatted filter
-     * string based on desired log level for Core SDK and other native packages.
-     *
-     * **BACKWARD COMPATIBILITY**
-     *
-     * If `logging.filter` is missing, the following legacy values (if present) will be used instead (in the given order):
-     * - {@link ForwardLogger.forward.level} => `makeTelemetryFilterString({ core: level, other: level })`
-     * - {@link TelemetryOptions.tracingFilter}
-     * - Default value of `makeTelemetryFilterString({ core: 'WARN', other: 'ERROR'})`
-     *
-     * @default `makeTelemetryFilterString({ core: 'WARN', other: 'ERROR'})` (with some exceptions, as described in backward compatibility note above)
-     */
-    filter?: string;
-  } & Partial<Logger>;
-
-  /**
-   * Control exporting {@link NativeConnection} and {@link Worker} metrics.
-   *
-   * Turned off by default
-   */
-  metrics?: MetricsExporter;
-
-  /**
-   * @deprecated Core SDK tracing is no longer supported. This option is ignored.
-   */
-  tracing?: unknown;
-}
-
-export type CompiledTelemetryOptions = {
-  logging: {
-    filter: string;
-  } & (
-    | { console: {} /* eslint-disable-line @typescript-eslint/no-empty-object-type */ }
-    | { forward: {} /* eslint-disable-line @typescript-eslint/no-empty-object-type */ }
-  );
-  metrics?: {
-    metricPrefix: string;
-    globalTags: Record<string, string> | undefined;
-    attachServiceName: boolean;
-  } & (CompiledPrometheusMetricsExporter | CompiledOtelMetricsExporter);
+  errors,
 };
-
-export interface WorkerOptions {
-  identity: string;
-  buildId: string;
-  useVersioning: boolean;
-  taskQueue: string;
-  tuner: WorkerTuner;
-  nonStickyToStickyPollRatio: number;
-  maxConcurrentWorkflowTaskPolls: number;
-  maxConcurrentActivityTaskPolls: number;
-  enableNonLocalActivities: boolean;
-  stickyQueueScheduleToStartTimeoutMs: number;
-  maxCachedWorkflows: number;
-  maxHeartbeatThrottleIntervalMs: number;
-  defaultHeartbeatThrottleIntervalMs: number;
-  maxTaskQueueActivitiesPerSecond?: number;
-  maxActivitiesPerSecond?: number;
-  shutdownGraceTimeMs: number;
-}
-
-export type LogEntryMetadata = {
-  [key: string]: string | number | boolean | LogEntryMetadata;
-};
-
-export interface LogEntry {
-  /** Log message */
-  message: string;
-  /**
-   * Time since epoch [seconds, nanos].
-   *
-   * Should be switched to bigint once it is supported in neon.
-   */
-  timestamp: [number, number];
-
-  /** Log level */
-  level: LogLevel;
-
-  /** Name of the Core subsystem that emitted that log entry */
-  target: string;
-
-  /*** Metadata fields */
-  fields: LogEntryMetadata;
-}
-
-/**
- * Which version of the executable to run.
- */
-export type EphemeralServerExecutable =
-  | {
-      type: 'cached-download';
-      /**
-       * Download destination directory or the system's temp directory if none set.
-       */
-      downloadDir?: string;
-      /**
-       * Optional version, can be set to a specific server release or "default" or "latest".
-       *
-       * At the time of writing the the server is released as part of the Java SDK - (https://github.com/temporalio/sdk-java/releases).
-       *
-       * @default "default" - get the best version for the current SDK version.
-       */
-      version?: string;
-      /** How long to cache the download for. Undefined means forever. */
-      ttlMs?: number;
-    }
-  | {
-      type: 'existing-path';
-      /** Path to executable */
-      path: string;
-    };
-
-/**
- * Configuration for the time-skipping test server.
- */
-export interface TimeSkippingServerConfig {
-  type: 'time-skipping';
-  executable?: EphemeralServerExecutable;
-  /**
-   * Optional port to listen on, defaults to find a random free port.
-   */
-  port?: number;
-  /**
-   * Extra args to pass to the executable command.
-   *
-   * Note that the Test Server implementation may be changed to another one in the future. Therefore, there is
-   * no guarantee that server options, and particularly those provided through the `extraArgs` array, will continue to
-   * be supported in the future.
-   */
-  extraArgs?: string[];
-}
-
-/**
- * Configuration for the Temporal CLI Dev Server.
- */
-export interface DevServerConfig {
-  type: 'dev-server';
-  executable?: EphemeralServerExecutable;
-  /**
-   * Sqlite DB filename if persisting or non-persistent if none (default).
-   */
-  dbFilename?: string;
-  /**
-   * Namespace to use - created at startup.
-   *
-   * @default "default"
-   */
-  namespace?: string;
-  /**
-   * IP to bind to.
-   *
-   * @default localhost
-   */
-  ip?: string;
-  /**
-   * Port to listen on; defaults to find a random free port.
-   */
-  port?: number;
-  /**
-   * Whether to enable the UI.
-   *
-   * @default true if `uiPort` is set; defaults to `false` otherwise.
-   */
-  ui?: boolean;
-  /**
-   * Port to listen on for the UI; if `ui` is true, defaults to `port + 1000`.
-   */
-  uiPort?: number;
-  /**
-   * Log format and level
-   * @default { format: "pretty", level" "warn" }
-   */
-  log?: { format: string; level: string };
-  /**
-   * Extra args to pass to the executable command.
-   *
-   * Note that the Dev Server implementation may be changed to another one in the future. Therefore, there is no
-   * guarantee that Dev Server options, and particularly those provided through the `extraArgs` array, will continue to
-   * be supported in the future.
-   */
-  extraArgs?: string[];
-  /**
-   * Search attributes to be registered with the dev server.
-   */
-  searchAttributes?: SearchAttributeKey<SearchAttributeType>[];
-}
-
-/**
- * Configuration for spawning an ephemeral Temporal server.
- *
- * Both the time-skipping Test Server and Temporal CLI dev server are supported.
- */
-export type EphemeralServerConfig = TimeSkippingServerConfig | DevServerConfig;
-
-export interface Worker {
-  type: 'Worker';
-}
-
-export interface Runtime {
-  type: 'Runtime';
-}
-
-export interface Client {
-  type: 'Client';
-}
-
-export interface EphemeralServer {
-  type: 'EphemeralServer';
-}
-
-export interface HistoryPusher {
-  type: 'HistoryPusher';
-}
-
-export interface ReplayWorker {
-  type: 'ReplayWorker';
-  worker: Worker;
-  pusher: HistoryPusher;
-}
-
-export declare type Callback<T> = (err: Error, result: T) => void;
-export declare type PollCallback = (err: Error, result: ArrayBuffer) => void;
-export declare type WorkerCallback = (err: Error, result: Worker) => void;
-export declare type ReplayWorkerCallback = (err: Error, worker: ReplayWorker) => void;
-export declare type ClientCallback = (err: Error, result: Client) => void;
-export declare type VoidCallback = (err: Error, result: void) => void;
-export declare type LogsCallback = (err: Error, result: LogEntry[]) => void;
-
-export declare function newRuntime(telemOptions: CompiledTelemetryOptions): Runtime;
-
-export declare function newClient(runtime: Runtime, clientOptions: ClientOptions, callback: ClientCallback): void;
-
-export declare function newWorker(client: Client, workerOptions: WorkerOptions, callback: WorkerCallback): void;
-
-export declare function newReplayWorker(
-  runtime: Runtime,
-  workerOptions: WorkerOptions,
-  callback: ReplayWorkerCallback
-): void;
-
-export declare function pushHistory(
-  pusher: HistoryPusher,
-  workflowId: string,
-  history: ArrayBuffer,
-  callback: VoidCallback
-): void;
-
-export declare function closeHistoryStream(pusher: HistoryPusher): void;
-
-export declare function workerInitiateShutdown(worker: Worker, callback: VoidCallback): void;
-
-export declare function workerFinalizeShutdown(worker: Worker): void;
-
-export declare function clientUpdateHeaders(
-  client: Client,
-  headers: Record<string, string>,
-  callback: VoidCallback
-): void;
-
-export declare function clientUpdateApiKey(client: Client, apiKey: string, callback: VoidCallback): void;
-
-export declare function clientClose(client: Client): void;
-
-export declare function runtimeShutdown(runtime: Runtime, callback: VoidCallback): void;
-
-export declare function pollLogs(runtime: Runtime, callback: LogsCallback): void;
-
-export declare function workerPollWorkflowActivation(worker: Worker, callback: PollCallback): void;
-
-export declare function workerCompleteWorkflowActivation(
-  worker: Worker,
-  result: ArrayBuffer,
-  callback: VoidCallback
-): void;
-
-export declare function workerPollActivityTask(worker: Worker, callback: PollCallback): void;
-
-export declare function workerCompleteActivityTask(worker: Worker, result: ArrayBuffer, callback: VoidCallback): void;
-
-export declare function workerRecordActivityHeartbeat(worker: Worker, heartbeat: ArrayBuffer): void;
-
-export declare function getTimeOfDay(): [number, number];
-
-export declare function startEphemeralServer(
-  runtime: Runtime,
-  config: EphemeralServerConfig,
-  sdkVersion: string,
-  callback: Callback<EphemeralServer>
-): void;
-
-export declare function shutdownEphemeralServer(server: EphemeralServer, callback: Callback<EphemeralServer>): void;
-
-export declare function getEphemeralServerTarget(server: EphemeralServer): string;
-
-export { ShutdownError, TransportError, UnexpectedError } from './errors';
diff --git a/packages/core-bridge/ts/native.ts b/packages/core-bridge/ts/native.ts
new file mode 100644
index 000000000..08bd35109
--- /dev/null
+++ b/packages/core-bridge/ts/native.ts
@@ -0,0 +1,335 @@
+/**
+ * Indicates a property that is allowed to be unspecified when calling in or out of
+ * native code (the equivalent of the `Option<T>` type in Rust).
+ *
+ * Always use either this type or the `T | null` idiom to indicate a property that may
+ * legitimately be left unspecified when calling into or out of native code. Never use
+ * `T | undefined` or `prop?: T` on TS/Rust interfaces.
+ *
+ * ### Rationale
+ *
+ * Differentiating between "a property that is set to an unspecified optional value"
+ * and "a non-existant property" allows eager detection of some of the most common
+ * bug patterns resulting from incoherencies between the JS and Rust type definitions
+ * (e.g. optional properties whose names differ between the two languages, or that
+ * are missing in the JS interface, etc.).
+ *
+ * Unfortunately, it is not possible at present in Neon to differentiate between
+ * a property that is set to `undefined` and a property that is missing;
+ * i.e. `obj.get_value(cx, "prop")` will return `undefined` in both cases.
+ *
+ * We therefore follow the following principles for our TypeScript/Rust interfaces:
+ *
+ * - Always use `null` to indicate an intentionally unspecified optional value
+ *   in TypeScript interfaces. This will be converted to `None` on the Rust side.
+ * - Explicitly set _every_ properties on objects sent to the native code,
+ *   including optional properties (e.g. `{ prop: input.prop ?? null }`).
+ * - Never use the "optional property" syntax in TypeScript (i.e. `prop?: T`).
+ *
+ * Thanks to those conventions, a property that reads as `undefined` is known to to always
+ * indicate an _unintentionally missing_ property, which will results in a runtime error.
+ */
+type Option<T> = T | null;
+
+/**
+ * Marker for values that are transferred as JSON strings.
+ */
+export type JsonString<_T> = string;
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Runtime
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export declare function newRuntime(telemOptions: RuntimeOptions): Runtime;
+export declare function runtimeShutdown(runtime: Runtime): void;
+
+export interface Runtime {
+  type: 'runtime';
+}
+
+export type RuntimeOptions = {
+  logExporter: LogExporterOptions;
+  telemetry: {
+    metricPrefix: string;
+    attachServiceName: boolean;
+  };
+  metricsExporter: MetricExporterOptions;
+};
+
+export type LogExporterOptions =
+  | {
+      type: 'console';
+      filter: string;
+    }
+  | {
+      type: 'forward';
+      filter: string;
+      receiver: (entries: JsonString<LogEntry>[]) => void;
+    };
+
+export type MetricExporterOptions =
+  | {
+      type: 'prometheus';
+      bindAddress: string;
+      countersTotalSuffix: boolean;
+      unitSuffix: boolean;
+      useSecondsForDurations: boolean;
+      histogramBucketOverrides: Record<string, number[]>;
+      globalTags: Record<string, string>;
+    }
+  | {
+      type: 'otel';
+      url: string;
+      protocol: 'http' | 'grpc';
+      headers: Record<string, string>;
+      metricsExportInterval: number;
+      useSecondsForDurations: boolean;
+      temporality: 'cumulative' | 'delta';
+      histogramBucketOverrides: Record<string, number[]>;
+      globalTags: Record<string, string>;
+    }
+  | null;
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Client
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export declare function newClient(runtime: Runtime, clientOptions: ClientOptions): Promise<Client>;
+export declare function clientUpdateHeaders(client: Client, headers: Record<string, string>): void;
+export declare function clientUpdateApiKey(client: Client, apiKey: string): void;
+export declare function clientClose(client: Client): void;
+
+export interface Client {
+  type: 'client';
+}
+
+export interface ClientOptions {
+  url: string;
+  sdkVersion: string;
+  tls: Option<TLSConfig>;
+  proxy: Option<ProxyConfig>;
+  metadata: Option<Record<string, string>>;
+  apiKey: Option<string>;
+  disableErrorCodeMetricTags: boolean;
+}
+
+export interface TLSConfig {
+  serverNameOverride: Option<string>;
+  serverRootCaCertificate: Option<Buffer>;
+  clientCertPair: Option<{
+    crt: Buffer;
+    key: Buffer;
+  }>;
+}
+
+export interface ProxyConfig {
+  type: 'http-connect';
+  targetHost: string;
+  basicAuth: Option<{
+    username: string;
+    password: string;
+  }>;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Worker
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export declare function newWorker(client: Client, workerOptions: WorkerOptions): Worker;
+export declare function workerValidate(worker: Worker): Promise<void>;
+
+export declare function workerInitiateShutdown(worker: Worker): void;
+export declare function workerFinalizeShutdown(worker: Worker): Promise<void>;
+
+export declare function workerPollWorkflowActivation(worker: Worker): Promise<Buffer>;
+export declare function workerCompleteWorkflowActivation(worker: Worker, result: Buffer): Promise<void>;
+
+export declare function workerPollActivityTask(worker: Worker): Promise<Buffer>;
+export declare function workerCompleteActivityTask(worker: Worker, result: Buffer): Promise<void>;
+export declare function workerRecordActivityHeartbeat(worker: Worker, heartbeat: Buffer): void;
+
+export interface Worker {
+  type: 'worker';
+}
+
+export interface WorkerOptions {
+  identity: string;
+  buildId: string;
+  useVersioning: boolean;
+  taskQueue: string;
+  namespace: string;
+  tuner: WorkerTunerOptions;
+  nonStickyToStickyPollRatio: number;
+  maxConcurrentWorkflowTaskPolls: number;
+  maxConcurrentActivityTaskPolls: number;
+  enableNonLocalActivities: boolean;
+  stickyQueueScheduleToStartTimeout: number;
+  maxCachedWorkflows: number;
+  maxHeartbeatThrottleInterval: number;
+  defaultHeartbeatThrottleInterval: number;
+  maxTaskQueueActivitiesPerSecond: Option<number>;
+  maxActivitiesPerSecond: Option<number>;
+  shutdownGraceTime: number;
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Worker Tuner
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export interface WorkerTunerOptions {
+  workflowTaskSlotSupplier: SlotSupplierOptions;
+  activityTaskSlotSupplier: SlotSupplierOptions;
+  localActivityTaskSlotSupplier: SlotSupplierOptions;
+}
+
+export type SlotSupplierOptions =
+  | FixedSizeSlotSupplierOptions
+  | ResourceBasedSlotSupplierOptions
+  | CustomSlotSupplierOptions<any>; // FIXME: any?
+
+interface FixedSizeSlotSupplierOptions {
+  type: 'fixed-size';
+  numSlots: number;
+}
+
+interface ResourceBasedSlotSupplierOptions {
+  type: 'resource-based';
+  minimumSlots: number;
+  maximumSlots: number;
+  rampThrottle: number;
+  tunerOptions: ResourceBasedTunerOptions;
+}
+
+interface ResourceBasedTunerOptions {
+  targetMemoryUsage: number;
+  targetCpuUsage: number;
+}
+
+export interface CustomSlotSupplierOptions<SI extends SlotInfo> {
+  type: 'custom';
+  reserveSlot(ctx: SlotReserveContext, abortSignal: AbortSignal): Promise<SlotPermit>;
+  tryReserveSlot(ctx: SlotReserveContext): Option<SlotPermit>;
+  markSlotUsed(ctx: SlotMarkUsedContext<SI>): void;
+  releaseSlot(ctx: SlotReleaseContext<SI>): void;
+}
+
+export type SlotInfo =
+  | {
+      type: 'workflow';
+      workflowType: string;
+      isSticky: boolean;
+    }
+  | {
+      type: 'activity';
+      activityType: string;
+    }
+  | {
+      type: 'local-activity';
+      activityType: string;
+    }
+  | {
+      type: 'nexus';
+      service: string;
+      operation: string;
+    };
+
+export interface SlotReserveContext {
+  slotType: SlotInfo['type'];
+  taskQueue: string;
+  workerIdentity: string;
+  workerBuildId: string;
+  isSticky: boolean;
+}
+
+export interface SlotMarkUsedContext<SI extends SlotInfo> {
+  slotInfo: SI;
+  permit: SlotPermit;
+}
+
+export interface SlotReleaseContext<SI extends SlotInfo> {
+  slotInfo: Option<SI>;
+  permit: SlotPermit;
+}
+
+// eslint-disable-next-line @typescript-eslint/no-empty-object-type
+export interface SlotPermit {}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// ReplayWorker
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export declare function newReplayWorker(runtime: Runtime, workerOptions: WorkerOptions): [Worker, HistoryPusher];
+export declare function pushHistory(pusher: HistoryPusher, workflowId: string, history: Buffer): Promise<void>;
+export declare function closeHistoryStream(pusher: HistoryPusher): void;
+
+export interface HistoryPusher {
+  type: 'history-pusher';
+}
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Log Forwarding
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+// export declare function pollLogs(runtime: Runtime): LogEntry[];
+export declare function getTimeOfDay(): bigint;
+
+export interface LogEntry {
+  message: string;
+  timestamp: string; // u128 as a string - JSON doesn't support u128 numbers
+  level: LogLevel;
+  target: string;
+  fields: LogEntryMetadata;
+}
+
+type LogLevel = 'TRACE' | 'DEBUG' | 'INFO' | 'WARN' | 'ERROR';
+
+type LogEntryMetadata = {
+  [key: string]: string | number | boolean | LogEntryMetadata;
+};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+// Ephemeral Server
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export interface EphemeralServer {
+  type: 'ephemeral-server';
+}
+
+export declare function startEphemeralServer(runtime: Runtime, config: EphemeralServerConfig): Promise<EphemeralServer>;
+export declare function getEphemeralServerTarget(server: EphemeralServer): string;
+export declare function shutdownEphemeralServer(server: EphemeralServer): Promise<void>;
+
+export type EphemeralServerConfig = TimeSkippingServerConfig | DevServerConfig;
+
+export interface TimeSkippingServerConfig {
+  type: 'time-skipping';
+  executable: EphemeralServerExecutableConfig;
+  port: Option<number>;
+  extraArgs: string[];
+}
+
+export interface DevServerConfig {
+  type: 'dev-server';
+  executable: EphemeralServerExecutableConfig;
+  ip: string;
+  port: Option<number>;
+  ui: boolean;
+  uiPort: Option<number>;
+  namespace: string;
+  dbFilename: Option<string>;
+  log: { format: string; level: string };
+  extraArgs: string[];
+}
+
+export type EphemeralServerExecutableConfig =
+  | {
+      type: 'cached-download';
+      downloadDir: Option<string>;
+      version: string;
+      ttl: number;
+      sdkVersion: string;
+    }
+  | {
+      type: 'existing-path';
+      path: string;
+    };
diff --git a/packages/core-bridge/ts/worker-tuner.ts b/packages/core-bridge/ts/worker-tuner.ts
deleted file mode 100644
index e3327c5ef..000000000
--- a/packages/core-bridge/ts/worker-tuner.ts
+++ /dev/null
@@ -1,211 +0,0 @@
-/**
- * A worker tuner allows the customization of the performance characteristics of workers by
- * controlling how "slots" are handed out for different task types. In order to poll for and then
- * run tasks, a slot must first be reserved by the {@link SlotSupplier} returned by the tuner.
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-export interface WorkerTuner {
-  workflowTaskSlotSupplier: SlotSupplier;
-  activityTaskSlotSupplier: SlotSupplier;
-  localActivityTaskSlotSupplier: SlotSupplier;
-}
-
-export type SlotInfo = WorkflowSlotInfo | ActivitySlotInfo | LocalActivitySlotInfo;
-
-export interface WorkflowSlotInfo {
-  type: 'workflow';
-  workflowId: string;
-  runId: string;
-}
-
-export interface ActivitySlotInfo {
-  type: 'activity';
-  activityId: string;
-}
-
-export interface LocalActivitySlotInfo {
-  type: 'local-activity';
-  activityId: string;
-}
-
-/**
- * Controls how slots are handed out for a specific task type.
- *
- * For now, only {@link ResourceBasedSlotOptions} and {@link FixedSizeSlotSupplier} are supported,
- * but we may add support for custom tuners in the future.
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-export type SlotSupplier = ResourceBasedSlotsForType | FixedSizeSlotSupplier | CustomSlotSupplier<any>;
-
-/**
- * Options for a specific slot type within a {@link ResourceBasedSlotsForType}
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-export interface ResourceBasedSlotOptions {
-  // Amount of slots that will be issued regardless of any other checks
-  minimumSlots: number;
-  // Maximum amount of slots permitted
-  maximumSlots: number;
-  // Minimum time we will wait (after passing the minimum slots number) between handing out new
-  // slots in milliseconds.
-  rampThrottleMs: number;
-}
-
-/**
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-type ResourceBasedSlotsForType = ResourceBasedSlotOptions & {
-  type: 'resource-based';
-  tunerOptions: ResourceBasedTunerOptions;
-};
-
-/**
- * Options for a {@link ResourceBasedTuner} to control target resource usage
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-export interface ResourceBasedTunerOptions {
-  // A value between 0 and 1 that represents the target (system) memory usage. It's not recommended
-  // to set this higher than 0.8, since how much memory a workflow may use is not predictable, and
-  // you don't want to encounter OOM errors.
-  targetMemoryUsage: number;
-  // A value between 0 and 1 that represents the target (system) CPU usage. This can be set to 1.0
-  // if desired, but it's recommended to leave some headroom for other processes.
-  targetCpuUsage: number;
-}
-
-/**
- * A fixed-size slot supplier that will never issue more than a fixed number of slots.
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-export interface FixedSizeSlotSupplier {
-  type: 'fixed-size';
-  // The maximum number of slots that can be issued
-  numSlots: number;
-}
-
-/**
- * The interface can be implemented to provide custom slot supplier behavior.
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-export interface CustomSlotSupplier<SI extends SlotInfo> {
-  type: 'custom';
-
-  /**
-   * This function is called before polling for new tasks. Your implementation should block until a
-   * slot is available then return a permit to use that slot.
-   *
-   * The only acceptable exception to throw is AbortError, any other exceptions thrown will be
-   * logged and ignored.
-   *
-   * The value inside the returned promise should be an object, however other types will still count
-   * as having issued a permit. Including undefined or null. Returning undefined or null does *not*
-   * mean you have not issued a permit. Implementations are expected to block until a meaningful
-   * permit can be issued.
-   *
-   * @param ctx The context for slot reservation.
-   * @param abortSignal The SDK may decide to abort the reservation request if it's no longer
-   *   needed. Implementations may clean up and then must reject the promise with AbortError.
-   * @returns A permit to use the slot which may be populated with your own data.
-   */
-  reserveSlot(ctx: SlotReserveContext, abortSignal: AbortSignal): Promise<SlotPermit>;
-
-  /**
-   * This function is called when trying to reserve slots for "eager" workflow and activity tasks.
-   * Eager tasks are those which are returned as a result of completing a workflow task, rather than
-   * from polling. Your implementation must not block, and if a slot is available, return a permit
-   * to use that slot.
-   *
-   * @param ctx The context for slot reservation.
-   * @returns Maybe a permit to use the slot which may be populated with your own data.
-   */
-  tryReserveSlot(ctx: SlotReserveContext): SlotPermit | null;
-
-  /**
-   * This function is called once a slot is actually being used to process some task, which may be
-   * some time after the slot was reserved originally. For example, if there is no work for a
-   * worker, a number of slots equal to the number of active pollers may already be reserved, but
-   * none of them are being used yet. This call should be non-blocking.
-   *
-   * @param ctx The context for marking a slot as used.
-   */
-  markSlotUsed(slot: SlotMarkUsedContext<SI>): void;
-
-  /**
-   * This function is called once a permit is no longer needed. This could be because the task has
-   * finished, whether successfully or not, or because the slot was no longer needed (ex: the number
-   * of active pollers decreased). This call should be non-blocking.
-   *
-   * @param ctx The context for releasing a slot.
-   */
-  releaseSlot(slot: SlotReleaseContext<SI>): void;
-}
-
-/**
- * A permit to use a slot.
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-// eslint-disable-next-line @typescript-eslint/no-empty-object-type
-export interface SlotPermit {}
-
-export interface SlotReserveContext {
-  /**
-   * The type of slot trying to be reserved
-   */
-  slotType: SlotInfo['type'];
-  /**
-   * The name of the task queue for which this reservation request is associated
-   */
-  taskQueue: string;
-  /**
-   * The identity of the worker that is requesting the reservation
-   */
-  workerIdentity: string;
-  /**
-   * The build id of the worker that is requesting the reservation
-   */
-  workerBuildId: string;
-  /**
-   * True iff this is a reservation for a sticky poll for a workflow task
-   */
-  isSticky: boolean;
-}
-
-/**
- * Context for marking a slot as used.
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-export interface SlotMarkUsedContext<SI extends SlotInfo> {
-  /**
-   * Info about the task that will be using the slot
-   */
-  slotInfo: SI;
-  /**
-   * The permit that was issued when the slot was reserved
-   */
-  permit: SlotPermit;
-}
-
-/**
- * Context for releasing a slot.
- *
- * @experimental Worker Tuner is an experimental feature and may be subject to change.
- */
-export interface SlotReleaseContext<SI extends SlotInfo> {
-  /**
-   * Info about the task that used this slot, if any. A slot may be released without being used in
-   * the event a poll times out.
-   */
-  slotInfo?: SI;
-  /**
-   * The permit that was issued when the slot was reserved
-   */
-  permit: SlotPermit;
-}
diff --git a/packages/test/src/helpers-integration.ts b/packages/test/src/helpers-integration.ts
index e932a1f66..7abcbacd7 100644
--- a/packages/test/src/helpers-integration.ts
+++ b/packages/test/src/helpers-integration.ts
@@ -54,7 +54,7 @@ function setupRuntime(recordedLogs?: { [workflowId: string]: LogEntry[] }) {
         recordedLogs![workflowId] ??= [];
         recordedLogs![workflowId].push(entry);
       })
-    : new DefaultLogger((process.env.TEST_LOG_LEVEL || 'DEBUG').toUpperCase() as LogLevel);
+    : new DefaultLogger((process.env.TEST_LOG_LEVEL || 'WARN').toUpperCase() as LogLevel);
   Runtime.install({
     logger,
     telemetryOptions: {
diff --git a/packages/test/src/load/worker.ts b/packages/test/src/load/worker.ts
index 8bc50874a..379e18455 100644
--- a/packages/test/src/load/worker.ts
+++ b/packages/test/src/load/worker.ts
@@ -5,13 +5,14 @@ import { OTLPTraceExporter } from '@opentelemetry/exporter-trace-otlp-grpc';
 import * as opentelemetry from '@opentelemetry/sdk-node';
 import { SemanticResourceAttributes } from '@opentelemetry/semantic-conventions';
 import arg from 'arg';
-import { LogLevel, TelemetryOptions } from '@temporalio/core-bridge';
 import { Connection } from '@temporalio/client';
 import {
   DefaultLogger,
   LogEntry,
+  LogLevel,
   NativeConnection,
   Runtime,
+  TelemetryOptions,
   Worker,
   makeTelemetryFilterString,
 } from '@temporalio/worker';
diff --git a/packages/test/src/mock-native-worker.ts b/packages/test/src/mock-native-worker.ts
index a0946071d..385233e97 100644
--- a/packages/test/src/mock-native-worker.ts
+++ b/packages/test/src/mock-native-worker.ts
@@ -34,14 +34,14 @@ export type Task =
   | { activity: coresdk.activity_task.IActivityTask };
 
 export class MockNativeWorker implements NativeWorkerLike {
-  public readonly type = 'Worker';
+  public readonly type = 'worker';
   flushCoreLogs(): void {
     // noop
   }
-  activityTasks: Array<Promise<ArrayBuffer>> = [];
-  workflowActivations: Array<Promise<ArrayBuffer>> = [];
-  activityCompletionCallback?: (arr: ArrayBuffer) => void;
-  workflowCompletionCallback?: (arr: ArrayBuffer) => void;
+  activityTasks: Array<Promise<Buffer>> = [];
+  workflowActivations: Array<Promise<Buffer>> = [];
+  activityCompletionCallback?: (arr: Buffer) => void;
+  workflowCompletionCallback?: (arr: Buffer) => void;
   activityHeartbeatCallback?: (taskToken: Uint8Array, details: any) => void;
   reject?: (err: Error) => void;
   namespace = 'mock';
@@ -52,14 +52,14 @@ export class MockNativeWorker implements NativeWorkerLike {
   }
 
   public static async createReplay(): Promise<NativeReplayHandle> {
-    return { worker: new this(), historyPusher: { type: 'HistoryPusher' } };
+    return { worker: new this(), historyPusher: { type: 'history-pusher' } };
   }
 
   public async finalizeShutdown(): Promise<void> {
     // Nothing to do here
   }
 
-  public async initiateShutdown(): Promise<void> {
+  public initiateShutdown(): void {
     const shutdownErrorPromise = Promise.reject(new ShutdownError('Core is shut down'));
     shutdownErrorPromise.catch(() => {
       /* avoid unhandled rejection */
@@ -68,7 +68,7 @@ export class MockNativeWorker implements NativeWorkerLike {
     this.workflowActivations.unshift(shutdownErrorPromise);
   }
 
-  public async pollWorkflowActivation(): Promise<ArrayBuffer> {
+  public async pollWorkflowActivation(): Promise<Buffer> {
     for (;;) {
       const task = this.workflowActivations.pop();
       if (task !== undefined) {
@@ -78,7 +78,7 @@ export class MockNativeWorker implements NativeWorkerLike {
     }
   }
 
-  public async pollActivityTask(): Promise<ArrayBuffer> {
+  public async pollActivityTask(): Promise<Buffer> {
     for (;;) {
       const task = this.activityTasks.pop();
       if (task !== undefined) {
@@ -88,12 +88,12 @@ export class MockNativeWorker implements NativeWorkerLike {
     }
   }
 
-  public async completeWorkflowActivation(result: ArrayBuffer): Promise<void> {
+  public async completeWorkflowActivation(result: Buffer): Promise<void> {
     this.workflowCompletionCallback!(result);
     this.workflowCompletionCallback = undefined;
   }
 
-  public async completeActivityTask(result: ArrayBuffer): Promise<void> {
+  public async completeActivityTask(result: Buffer): Promise<void> {
     this.activityCompletionCallback!(result);
     this.activityCompletionCallback = undefined;
   }
@@ -116,7 +116,7 @@ export class MockNativeWorker implements NativeWorkerLike {
   ): Promise<coresdk.workflow_completion.WorkflowActivationCompletion> {
     const arr = coresdk.workflow_activation.WorkflowActivation.encode(activation).finish();
     const buffer = byteArrayToBuffer(arr);
-    const result = await new Promise<ArrayBuffer>((resolve) => {
+    const result = await new Promise<Buffer>((resolve) => {
       this.workflowCompletionCallback = resolve;
       this.workflowActivations.unshift(Promise.resolve(buffer));
     });
@@ -127,14 +127,14 @@ export class MockNativeWorker implements NativeWorkerLike {
     addActivityStartDefaults(task);
     const arr = coresdk.activity_task.ActivityTask.encode(task).finish();
     const buffer = byteArrayToBuffer(arr);
-    const result = await new Promise<ArrayBuffer>((resolve) => {
+    const result = await new Promise<Buffer>((resolve) => {
       this.activityCompletionCallback = resolve;
       this.activityTasks.unshift(Promise.resolve(buffer));
     });
     return coresdk.ActivityTaskCompletion.decodeDelimited(new Uint8Array(result));
   }
 
-  public recordActivityHeartbeat(buffer: ArrayBuffer): void {
+  public recordActivityHeartbeat(buffer: Buffer): void {
     const { taskToken, details } = coresdk.ActivityHeartbeat.decodeDelimited(new Uint8Array(buffer));
     const arg = fromPayloadsAtIndex(defaultPayloadConverter, 0, details);
     this.activityHeartbeatCallback!(taskToken, arg);
@@ -159,12 +159,13 @@ export class Worker extends RealWorker {
   }
 
   public constructor(workflowCreator: WorkflowCreator, opts: CompiledWorkerOptions) {
-    const logger = withMetadata(Runtime.instance().logger, {
+    const runtime = Runtime.instance();
+    const logger = withMetadata(runtime.logger, {
       sdkComponent: SdkComponent.worker,
       taskQueue: opts.taskQueue,
     });
     const nativeWorker = new MockNativeWorker();
-    super(nativeWorker, workflowCreator, opts, logger);
+    super(runtime, nativeWorker, workflowCreator, opts, logger);
   }
 
   public runWorkflows(...args: Parameters<Worker['workflow$']>): Promise<void> {
diff --git a/packages/test/src/test-bridge.ts b/packages/test/src/test-bridge.ts
new file mode 100644
index 000000000..5b2fffd2c
--- /dev/null
+++ b/packages/test/src/test-bridge.ts
@@ -0,0 +1,244 @@
+import { setTimeout } from 'node:timers/promises';
+import ms from 'ms';
+import test from 'ava';
+import { native, errors } from '@temporalio/core-bridge';
+
+// TESTING NOTES
+//
+// - Tests in this file requires an external Temporal server to be running, because using the ephemeral
+//   server support provided by Core SDK would affect the behavior that we're testing here.
+// - Tests in this file can't be run in parallel, since the bridge is mostly a singleton.
+// - Some of these tests explicitly use the native bridge, without going through the lang side Runtime/Worker.
+
+test('Can instantiate and shutdown the native runtime', async (t) => {
+  const runtime = native.newRuntime(GenericConfigs.runtime.basic);
+  t.is(typeof runtime, 'object');
+  native.runtimeShutdown(runtime);
+
+  // Pass this point, any operation on the runtime should throw
+
+  t.throws(() => native.newClient(runtime, GenericConfigs.client.basic), {
+    instanceOf: errors.IllegalStateError,
+    message: 'Runtime already closed',
+  });
+
+  // Trying to shutdown the runtime a second time should throw
+  t.throws(() => native.runtimeShutdown(runtime), {
+    instanceOf: errors.IllegalStateError,
+    message: 'Runtime already closed',
+  });
+});
+
+test('Can run multiple runtime concurrently', async (t) => {
+  const runtime1 = native.newRuntime(GenericConfigs.runtime.basic);
+  const runtime2 = native.newRuntime(GenericConfigs.runtime.basic);
+  const runtime3 = native.newRuntime(GenericConfigs.runtime.basic);
+
+  // Order is intentionally random - distinct runtimes are expected to be independent
+  const _client2 = await native.newClient(runtime3, GenericConfigs.client.basic);
+  const _client1 = await native.newClient(runtime1, GenericConfigs.client.basic);
+  const _client3 = await native.newClient(runtime2, GenericConfigs.client.basic);
+
+  native.runtimeShutdown(runtime1);
+  native.runtimeShutdown(runtime3);
+
+  await t.throwsAsync(async () => await native.newClient(runtime1, GenericConfigs.client.basic), {
+    instanceOf: errors.IllegalStateError,
+    message: 'Runtime already closed',
+  });
+
+  const _client5 = await native.newClient(runtime2, GenericConfigs.client.basic);
+
+  native.runtimeShutdown(runtime2);
+
+  t.pass();
+});
+
+test('Missing/invalid properties in config throws appropriately', async (t) => {
+  // required string = undefined ==> missing property
+  t.throws(
+    () =>
+      native.newRuntime({
+        ...GenericConfigs.runtime.basic,
+        logExporter: {
+          type: 'forward',
+          // @ts-expect-error 2322
+          filter: undefined,
+        },
+      }),
+    {
+      instanceOf: TypeError,
+      message: "fn runtime_new.args[0].logExporter.forward.filter: Missing property 'filter'",
+    }
+  );
+
+  // required string = null ==> failed to downcast
+  t.throws(
+    () =>
+      native.newRuntime({
+        ...GenericConfigs.runtime.basic,
+        logExporter: {
+          type: 'forward',
+          // @ts-expect-error 2322
+          filter: null,
+        },
+      }),
+    {
+      instanceOf: TypeError,
+      // FIXME: should say "failed to downcast _null_ to string"
+      message: 'fn runtime_new.args[0].logExporter.forward.filter: failed to downcast any to string',
+    }
+  );
+
+  // required string = number ==> failed to downcast
+  t.throws(
+    () =>
+      native.newRuntime({
+        ...GenericConfigs.runtime.basic,
+        logExporter: {
+          type: 'forward',
+          // @ts-expect-error 2322
+          filter: 1234,
+        },
+      }),
+    {
+      instanceOf: TypeError,
+      // FIXME: should say "failed to downcast _number_ to string"
+      message: 'fn runtime_new.args[0].logExporter.forward.filter: failed to downcast any to string',
+    }
+  );
+
+  // optional object = undefined ==> missing property
+  t.throws(
+    () =>
+      native.newRuntime({
+        ...GenericConfigs.runtime.basic,
+        // @ts-expect-error 2322
+        metricsExporter: undefined,
+      }),
+    {
+      instanceOf: TypeError,
+      message: "fn runtime_new.args[0].metricsExporter: Missing property 'metricsExporter'",
+    }
+  );
+});
+
+test(`get_time_of_day() returns a bigint`, async (t) => {
+  const time_1 = await native.getTimeOfDay();
+  const time_2 = await native.getTimeOfDay();
+  await setTimeout(100);
+  const time_3 = await native.getTimeOfDay();
+
+  t.is(typeof time_1, 'bigint');
+  t.true(time_1 < time_2);
+  t.true(time_2 + 100_000_000n < time_3); // At least 100ms passed
+});
+
+test("Creating Runtime without shutting it down doesn't hang process", (t) => {
+  const _runtime = native.newRuntime(GenericConfigs.runtime.basic);
+  t.pass();
+});
+
+test("Dropping Client without closing doesn't hang process", (t) => {
+  const runtime = native.newRuntime(GenericConfigs.runtime.basic);
+  const _client = native.newClient(runtime, GenericConfigs.client.basic);
+  t.pass();
+});
+
+test("Dropping Worker without shutting it down doesn't hang process", async (t) => {
+  const runtime = native.newRuntime(GenericConfigs.runtime.basic);
+  const client = await native.newClient(runtime, GenericConfigs.client.basic);
+  const worker = native.newWorker(client, GenericConfigs.worker.basic);
+  await native.workerValidate(worker);
+  t.pass();
+});
+
+// FIXME: Not hanging, but server is left running. Should try to kill process on Finalize?
+test.skip("Dropping EphemeralServer without shutting it down doesn't hang process", async (t) => {
+  const runtime = native.newRuntime(GenericConfigs.runtime.basic);
+  const _ephemeralServer = await native.startEphemeralServer(runtime, GenericConfigs.ephemeralServer.basic);
+  t.pass();
+});
+
+// Sample configs ///////////////////////////////////////////////////////////////////////////////////
+
+const GenericConfigs = {
+  runtime: {
+    basic: {
+      logExporter: {
+        type: 'console',
+        filter: 'ERROR',
+      },
+      telemetry: {
+        metricPrefix: 'test',
+        attachServiceName: false,
+      },
+      metricsExporter: null,
+    } satisfies native.RuntimeOptions,
+  },
+  client: {
+    basic: {
+      url: 'http://127.0.0.1:7233',
+      sdkVersion: '1.0.0',
+      tls: null,
+      proxy: null,
+      metadata: null,
+      apiKey: null,
+      disableErrorCodeMetricTags: false,
+    } satisfies native.ClientOptions,
+  },
+  worker: {
+    basic: {
+      taskQueue: 'default',
+      identity: 'test-worker',
+      buildId: 'test-build-id',
+      useVersioning: false,
+      namespace: 'default',
+      tuner: {
+        workflowTaskSlotSupplier: {
+          type: 'fixed-size',
+          numSlots: 1,
+        },
+        activityTaskSlotSupplier: {
+          type: 'fixed-size',
+          numSlots: 1,
+        },
+        localActivityTaskSlotSupplier: {
+          type: 'fixed-size',
+          numSlots: 1,
+        },
+      },
+      nonStickyToStickyPollRatio: 0.5,
+      maxConcurrentWorkflowTaskPolls: 1,
+      maxConcurrentActivityTaskPolls: 1,
+      enableNonLocalActivities: false,
+      stickyQueueScheduleToStartTimeout: 1000,
+      maxCachedWorkflows: 1000,
+      maxHeartbeatThrottleInterval: 1000,
+      defaultHeartbeatThrottleInterval: 1000,
+      maxTaskQueueActivitiesPerSecond: null,
+      maxActivitiesPerSecond: null,
+      shutdownGraceTime: 1000,
+    } satisfies native.WorkerOptions,
+  },
+  ephemeralServer: {
+    basic: {
+      type: 'dev-server',
+      executable: {
+        type: 'cached-download',
+        downloadDir: null,
+        version: 'default',
+        ttl: ms('1y'),
+        sdkVersion: '1.0.0',
+      },
+      ip: '127.0.0.1',
+      port: null,
+      ui: false,
+      uiPort: null,
+      namespace: 'default',
+      dbFilename: null,
+      log: { format: 'json', level: 'info' },
+      extraArgs: [],
+    } satisfies native.EphemeralServerConfig,
+  },
+} as const;
diff --git a/packages/test/src/test-ephemeral-server.ts b/packages/test/src/test-ephemeral-server.ts
index 2deddd019..4930b2639 100644
--- a/packages/test/src/test-ephemeral-server.ts
+++ b/packages/test/src/test-ephemeral-server.ts
@@ -82,7 +82,10 @@ test('TestEnvironment sets up dev server with db filename', async (t) => {
 });
 
 test('TestEnvironment sets up dev server with custom port and ui', async (t) => {
-  const port = await getRandomPort();
+  // FIXME: We'd really need to assert that the UI port is not being used by another process.
+  let port = await getRandomPort();
+  if (port > 65535 - 1000) port = 65535 - 1000;
+
   const testEnv = await TestWorkflowEnvironment.createLocal({
     server: {
       ip: '127.0.0.1',
@@ -125,3 +128,18 @@ test('TestEnvironment sets up dev server with custom ui port', async (t) => {
     await testEnv.teardown();
   }
 });
+
+test("TestEnvironment doesn't hang on fail to download", async (t) => {
+  try {
+    await TestWorkflowEnvironment.createLocal({
+      server: {
+        executable: {
+          type: 'cached-download',
+          version: '999.999.999',
+        },
+      },
+    });
+  } catch (_e) {
+    t.pass();
+  }
+});
diff --git a/packages/test/src/test-native-connection.ts b/packages/test/src/test-native-connection.ts
index d68aa3980..dfbdb830c 100644
--- a/packages/test/src/test-native-connection.ts
+++ b/packages/test/src/test-native-connection.ts
@@ -48,7 +48,7 @@ test('NativeConnection.connect() throws meaningful error when passed invalid add
 test('NativeConnection.connect() throws meaningful error when passed invalid clientCertPair', async (t) => {
   await t.throwsAsync(NativeConnection.connect({ tls: { clientCertPair: {} as any } }), {
     instanceOf: TypeError,
-    message: 'Invalid or missing serverOptions.tls.clientCertPair.crt',
+    message: /tls\.clientCertPair\.crt: Missing property/,
   });
 });
 
diff --git a/packages/test/src/test-otel.ts b/packages/test/src/test-otel.ts
index b87925de0..369e8b547 100644
--- a/packages/test/src/test-otel.ts
+++ b/packages/test/src/test-otel.ts
@@ -58,7 +58,16 @@ async function withFakeGrpcServer(
       });
       fn(addr.port)
         .catch((e) => reject(e))
-        .finally(() => srv.close((_) => resolve()));
+        .finally(() => {
+          resolve();
+
+          // The OTel exporter will try to flush metrics on drop, which may result in tons of ERROR
+          // messages on the console if the server has had time to complete shutdown before then.
+          // Delaying closing the server by 1 second is enough to avoid that situation.
+          setTimeout(() => {
+            srv.close();
+          }, 1000).unref();
+        });
     });
   });
 }
@@ -81,7 +90,16 @@ async function withHttpServer(
       });
       fn(addr.port)
         .catch((e) => reject(e))
-        .finally(() => srv.close((_) => resolve()));
+        .finally(() => {
+          resolve();
+
+          // The OTel exporter will try to flush metrics on drop, which may result in ERROR messages
+          // on the console if the server has had time to complete shutdown before then.
+          // Not really a problem, but delaying closing the server by 1 second helps avoid the error.
+          setTimeout(() => {
+            srv.close();
+          }, 1000).unref();
+        });
     });
   });
 }
@@ -89,7 +107,7 @@ async function withHttpServer(
 test.serial('Runtime.install() throws meaningful error when passed invalid metrics.otel.url', async (t) => {
   t.throws(() => Runtime.install({ telemetryOptions: { metrics: { otel: { url: ':invalid' } } } }), {
     instanceOf: TypeError,
-    message: /Invalid telemetryOptions.metrics.otel.url/,
+    message: /metricsExporter.otel.url/,
   });
 });
 
@@ -106,106 +124,102 @@ test.serial('Runtime.install() accepts metrics.otel.url without headers', async
 test.serial('Exporting OTEL metrics from Core works', async (t) => {
   let resolveCapturedRequest = (_req: http2.Http2ServerRequest) => undefined as void;
   const capturedRequest = new Promise<http2.Http2ServerRequest>((r) => (resolveCapturedRequest = r));
-  try {
-    await withFakeGrpcServer(async (port: number) => {
-      Runtime.install({
-        telemetryOptions: {
-          metrics: {
-            otel: {
-              url: `http://127.0.0.1:${port}`,
-              headers: {
-                'x-test-header': 'test-value',
-              },
-              metricsExportInterval: 10,
+
+  await withFakeGrpcServer(async (port: number) => {
+    Runtime.install({
+      telemetryOptions: {
+        metrics: {
+          otel: {
+            url: `http://127.0.0.1:${port}`,
+            headers: {
+              'x-test-header': 'test-value',
             },
+            metricsExportInterval: 10,
           },
         },
-      });
+      },
+    });
 
-      const localEnv = await TestWorkflowEnvironment.createLocal();
-      try {
-        const worker = await Worker.create({
-          connection: localEnv.nativeConnection,
-          workflowsPath: require.resolve('./workflows'),
+    const localEnv = await TestWorkflowEnvironment.createLocal();
+    try {
+      const worker = await Worker.create({
+        connection: localEnv.nativeConnection,
+        workflowsPath: require.resolve('./workflows'),
+        taskQueue: 'test-otel',
+      });
+      const client = new WorkflowClient({
+        connection: localEnv.connection,
+      });
+      await worker.runUntil(async () => {
+        await client.execute(workflows.successString, {
           taskQueue: 'test-otel',
+          workflowId: uuid4(),
         });
-        const client = new WorkflowClient({
-          connection: localEnv.connection,
-        });
-        await worker.runUntil(async () => {
-          await client.execute(workflows.successString, {
-            taskQueue: 'test-otel',
-            workflowId: uuid4(),
-          });
-          const req = await Promise.race([
-            capturedRequest,
-            await new Promise<undefined>((resolve) => setTimeout(() => resolve(undefined), 2000)),
-          ]);
-          t.truthy(req);
-          t.is(req?.url, '/opentelemetry.proto.collector.metrics.v1.MetricsService/Export');
-          t.is(req?.headers['x-test-header'], 'test-value');
-        });
-      } finally {
-        await localEnv.teardown();
-      }
-    }, resolveCapturedRequest);
-  } finally {
-    // Cleanup the runtime so that it doesn't interfere with other tests
-    await Runtime._instance?.shutdown();
-  }
+        const req = await Promise.race([
+          capturedRequest,
+          await new Promise<undefined>((resolve) => setTimeout(() => resolve(undefined), 2000)),
+        ]);
+        t.truthy(req);
+        t.is(req?.url, '/opentelemetry.proto.collector.metrics.v1.MetricsService/Export');
+        t.is(req?.headers['x-test-header'], 'test-value');
+      });
+    } finally {
+      await localEnv.teardown();
+      // Cleanup the runtime so that it doesn't interfere with other tests
+      await Runtime._instance?.shutdown();
+    }
+  }, resolveCapturedRequest);
 });
 
 test.serial('Exporting OTEL metrics using OTLP/HTTP from Core works', async (t) => {
   let resolveCapturedRequest = (_req: http.IncomingMessage) => undefined as void;
   const capturedRequest = new Promise<http.IncomingMessage>((r) => (resolveCapturedRequest = r));
-  try {
-    await withHttpServer(async (port: number) => {
-      Runtime.install({
-        telemetryOptions: {
-          metrics: {
-            otel: {
-              url: `http://127.0.0.1:${port}/v1/metrics`,
-              http: true,
-              headers: {
-                'x-test-header': 'test-value',
-              },
-              metricsExportInterval: 10,
+  // try {
+  await withHttpServer(async (port: number) => {
+    Runtime.install({
+      telemetryOptions: {
+        metrics: {
+          otel: {
+            url: `http://127.0.0.1:${port}/v1/metrics`,
+            http: true,
+            headers: {
+              'x-test-header': 'test-value',
             },
+            metricsExportInterval: 10,
           },
         },
-      });
+      },
+    });
 
-      const localEnv = await TestWorkflowEnvironment.createLocal();
-      try {
-        const worker = await Worker.create({
-          connection: localEnv.nativeConnection,
-          workflowsPath: require.resolve('./workflows'),
+    const localEnv = await TestWorkflowEnvironment.createLocal();
+    try {
+      const worker = await Worker.create({
+        connection: localEnv.nativeConnection,
+        workflowsPath: require.resolve('./workflows'),
+        taskQueue: 'test-otel',
+      });
+      const client = new WorkflowClient({
+        connection: localEnv.connection,
+      });
+      await worker.runUntil(async () => {
+        await client.execute(workflows.successString, {
           taskQueue: 'test-otel',
+          workflowId: uuid4(),
         });
-        const client = new WorkflowClient({
-          connection: localEnv.connection,
-        });
-        await worker.runUntil(async () => {
-          await client.execute(workflows.successString, {
-            taskQueue: 'test-otel',
-            workflowId: uuid4(),
-          });
-          const req = await Promise.race([
-            capturedRequest,
-            await new Promise<undefined>((resolve) => setTimeout(() => resolve(undefined), 2000)),
-          ]);
-          t.truthy(req);
-          t.is(req?.url, '/v1/metrics');
-          t.is(req?.headers['x-test-header'], 'test-value');
-        });
-      } finally {
-        await localEnv.teardown();
-      }
-    }, resolveCapturedRequest);
-  } finally {
-    // Cleanup the runtime so that it doesn't interfere with other tests
-    await Runtime._instance?.shutdown();
-  }
+        const req = await Promise.race([
+          capturedRequest,
+          await new Promise<undefined>((resolve) => setTimeout(() => resolve(undefined), 2000)),
+        ]);
+        t.truthy(req);
+        t.is(req?.url, '/v1/metrics');
+        t.is(req?.headers['x-test-header'], 'test-value');
+      });
+    } finally {
+      await localEnv.teardown();
+      // Cleanup the runtime so that it doesn't interfere with other tests
+      await Runtime._instance?.shutdown();
+    }
+  }, resolveCapturedRequest);
 });
 
 if (RUN_INTEGRATION_TESTS) {
@@ -365,8 +379,10 @@ if (RUN_INTEGRATION_TESTS) {
     }
   });
 
-  // Un-skip this test and run it by hand to inspect outputted traces
-  test.serial('Otel spans connected', async (t) => {
+  // FIXME: This tests take ~9 seconds to complete on my local machine, even
+  //        more in CI, and yet, it doesn't really do any assertion by itself.
+  //        To be revisited at a later time.
+  test.skip('Otel spans connected', async (t) => {
     const logger = new DefaultLogger('DEBUG');
     Runtime.install({
       logger,
diff --git a/packages/test/src/test-prometheus.ts b/packages/test/src/test-prometheus.ts
index 8cbd3af6a..38edc6fe3 100644
--- a/packages/test/src/test-prometheus.ts
+++ b/packages/test/src/test-prometheus.ts
@@ -9,7 +9,7 @@ import * as workflows from './workflows';
 test.serial('Runtime.install() throws meaningful error when passed invalid metrics.prometheus.bindAddress', (t) => {
   t.throws(() => Runtime.install({ telemetryOptions: { metrics: { prometheus: { bindAddress: ':invalid' } } } }), {
     instanceOf: TypeError,
-    message: 'Invalid telemetryOptions.metrics.prometheus.bindAddress',
+    message: /metricsExporter.prometheus.bindAddress/,
   });
 });
 
diff --git a/packages/test/src/test-runtime.ts b/packages/test/src/test-runtime.ts
index 4ac9bdd8b..8c030795c 100644
--- a/packages/test/src/test-runtime.ts
+++ b/packages/test/src/test-runtime.ts
@@ -82,10 +82,6 @@ if (RUN_INTEGRATION_TESTS) {
       telemetryOptions: { logging: { forward: {}, filter: makeTelemetryFilterString({ core: 'DEBUG' }) } },
     });
     try {
-      {
-        const runtime = Runtime.instance();
-        t.is(runtime.options.logger, logger);
-      }
       await new Client().workflow.start('not-existant', { taskQueue: 'q1', workflowId: uuid4() });
       const worker = await Worker.create({
         ...defaultOptions,
@@ -97,7 +93,7 @@ if (RUN_INTEGRATION_TESTS) {
             if (!logEntries.some((x) => x.message === 'Failing workflow task'))
               throw new Error('Waiting for failing workflow task');
           },
-          { maxTimeout: 5000, retries: 50 }
+          { maxTimeout: 200, minTimeout: 20, retries: 40 }
         )
       );
 
@@ -117,11 +113,4 @@ if (RUN_INTEGRATION_TESTS) {
       await Runtime.instance().shutdown();
     }
   });
-
-  test.serial('Runtime.install() throws meaningful error when passed invalid telemetryOptions.logging.filter', (t) => {
-    t.throws(() => Runtime.install({ telemetryOptions: { logging: { filter: 2 as any } } }), {
-      instanceOf: TypeError,
-      message: 'Invalid filter',
-    });
-  });
 }
diff --git a/packages/test/src/test-sinks.ts b/packages/test/src/test-sinks.ts
index f3991fccb..b7b18f263 100644
--- a/packages/test/src/test-sinks.ts
+++ b/packages/test/src/test-sinks.ts
@@ -441,8 +441,6 @@ if (RUN_INTEGRATION_TESTS) {
       ...defaultOptions,
       taskQueue,
       sinks,
-      maxCachedWorkflows: 2,
-      maxConcurrentWorkflowTaskExecutions: 2,
 
       // Cut down on execution time
       stickyQueueScheduleToStartTimeout: 1,
diff --git a/packages/test/src/test-worker-lifecycle.ts b/packages/test/src/test-worker-lifecycle.ts
index 2c9a28d73..2cb408ecd 100644
--- a/packages/test/src/test-worker-lifecycle.ts
+++ b/packages/test/src/test-worker-lifecycle.ts
@@ -7,8 +7,7 @@
 import { setTimeout } from 'timers/promises';
 import { randomUUID } from 'crypto';
 import test from 'ava';
-import { Runtime, PromiseCompletionTimeoutError } from '@temporalio/worker';
-import { TransportError, UnexpectedError } from '@temporalio/core-bridge';
+import { Runtime, PromiseCompletionTimeoutError, TransportError, UnexpectedError } from '@temporalio/worker';
 import { Client } from '@temporalio/client';
 import { RUN_INTEGRATION_TESTS, Worker } from './helpers';
 import { defaultOptions, isolateFreeWorker } from './mock-native-worker';
@@ -21,15 +20,17 @@ if (RUN_INTEGRATION_TESTS) {
       taskQueue: t.title.replace(/ /g, '_'),
     });
     t.is(worker.getState(), 'INITIALIZED');
+    t.not(Runtime._instance, undefined);
     const p = worker.run();
     t.is(worker.getState(), 'RUNNING');
     process.emit('SIGINT', 'SIGINT');
     // Shutdown callback is enqueued as a microtask
     await new Promise((resolve) => process.nextTick(resolve));
-    t.is(worker.getState(), 'STOPPING');
+    t.is(worker.getState(), 'DRAINING');
     await p;
     t.is(worker.getState(), 'STOPPED');
     await t.throwsAsync(worker.run(), { message: 'Poller was already started' });
+    t.is(Runtime._instance, undefined);
   });
 
   test.serial("Worker.runUntil doesn't hang if provided promise survives to Worker's shutdown", async (t) => {
@@ -37,6 +38,7 @@ if (RUN_INTEGRATION_TESTS) {
       ...defaultOptions,
       taskQueue: t.title.replace(/ /g, '_'),
     });
+    t.not(Runtime._instance, undefined);
     const p = worker.runUntil(
       new Promise(() => {
         /* a promise that will never unblock */
@@ -44,9 +46,10 @@ if (RUN_INTEGRATION_TESTS) {
     );
     t.is(worker.getState(), 'RUNNING');
     worker.shutdown();
-    t.is(worker.getState(), 'STOPPING');
+    t.is(worker.getState(), 'DRAINING');
     await t.throwsAsync(p, { instanceOf: PromiseCompletionTimeoutError });
     t.is(worker.getState(), 'STOPPED');
+    t.is(Runtime._instance, undefined);
   });
 
   test.serial('Worker shuts down gracefully if interrupted before running', async (t) => {
@@ -148,7 +151,7 @@ test.serial('Mocked run shuts down gracefully if interrupted before running', as
     const worker = isolateFreeWorker({
       taskQueue: t.title.replace(/ /g, '_'),
     });
-    // worker.native.initiateShutdown = () => new Promise(() => undefined);
+    // worker.native.initiateShutdown = () => undefined;
     t.is(worker.getState(), 'INITIALIZED');
     process.emit('SIGINT', 'SIGINT');
     const p = worker.run();
@@ -169,7 +172,7 @@ test.serial('Mocked run throws if not shut down gracefully', async (t) => {
   const p = worker.run();
   t.is(worker.getState(), 'RUNNING');
   // Make sure shutdown never resolves
-  worker.native.initiateShutdown = () => new Promise(() => undefined);
+  worker.native.initiateShutdown = () => undefined;
   worker.shutdown();
   await t.throwsAsync(p, {
     message: 'Timed out while waiting for worker to shutdown gracefully',
@@ -183,7 +186,7 @@ test.serial('Mocked throws combined error in runUntil', async (t) => {
     shutdownForceTime: '5ms',
     taskQueue: t.title.replace(/ /g, '_'),
   });
-  worker.native.initiateShutdown = () => new Promise(() => undefined);
+  worker.native.initiateShutdown = () => undefined;
   const err = await t.throwsAsync(
     worker.runUntil(async () => {
       throw new Error('inner');
diff --git a/packages/test/src/test-worker-tuner.ts b/packages/test/src/test-worker-tuner.ts
index 1fe8ec61c..0a5709e09 100644
--- a/packages/test/src/test-worker-tuner.ts
+++ b/packages/test/src/test-worker-tuner.ts
@@ -1,7 +1,7 @@
 import { ExecutionContext } from 'ava';
-import { ResourceBasedTunerOptions } from '@temporalio/core-bridge';
 import {
   CustomSlotSupplier,
+  ResourceBasedTunerOptions,
   SlotInfo,
   SlotMarkUsedContext,
   SlotPermit,
diff --git a/packages/testing/src/client.ts b/packages/testing/src/client.ts
new file mode 100644
index 000000000..be771abdf
--- /dev/null
+++ b/packages/testing/src/client.ts
@@ -0,0 +1,85 @@
+import 'abort-controller/polyfill'; // eslint-disable-line import/no-unassigned-import
+import {
+  Client,
+  ClientOptions,
+  WorkflowClient,
+  WorkflowClientOptions,
+  WorkflowResultOptions,
+} from '@temporalio/client';
+import { Connection, TestService } from './connection';
+
+// Config ///////////////////////////////////////////////////////////////////////////////////////////
+
+export interface TimeSkippingWorkflowClientOptions extends WorkflowClientOptions {
+  connection: Connection;
+  enableTimeSkipping: boolean;
+}
+
+export interface TestEnvClientOptions extends ClientOptions {
+  connection: Connection;
+  enableTimeSkipping: boolean;
+}
+
+/**
+ * Subset of the "normal" client options that are used to create a client for the test environment.
+ */
+export type ClientOptionsForTestEnv = Omit<ClientOptions, 'namespace' | 'connection'>;
+
+// Implementation //////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * A client with the exact same API as the "normal" client with 1 exception,
+ * When this client waits on a Workflow's result, it will enable time skipping
+ * in the test server.
+ */
+export class TimeSkippingWorkflowClient extends WorkflowClient {
+  protected readonly testService: TestService;
+  protected readonly enableTimeSkipping: boolean;
+
+  constructor(options: TimeSkippingWorkflowClientOptions) {
+    super(options);
+    this.enableTimeSkipping = options.enableTimeSkipping;
+    this.testService = options.connection.testService;
+  }
+
+  /**
+   * Gets the result of a Workflow execution.
+   *
+   * @see {@link WorkflowClient.result}
+   */
+  override async result<T>(
+    workflowId: string,
+    runId?: string | undefined,
+    opts?: WorkflowResultOptions | undefined
+  ): Promise<T> {
+    if (this.enableTimeSkipping) {
+      await this.testService.unlockTimeSkipping({});
+      try {
+        return await super.result(workflowId, runId, opts);
+      } finally {
+        await this.testService.lockTimeSkipping({});
+      }
+    } else {
+      return await super.result(workflowId, runId, opts);
+    }
+  }
+}
+
+/**
+ * A client with the exact same API as the "normal" client with one exception:
+ * when `TestEnvClient.workflow` (an instance of {@link TimeSkippingWorkflowClient}) waits on a Workflow's result, it will enable time skipping
+ * in the Test Server.
+ */
+export class TestEnvClient extends Client {
+  constructor(options: TestEnvClientOptions) {
+    super(options);
+
+    // Recreate the client (this isn't optimal but it's better than adding public methods just for testing).
+    // NOTE: we cast to "any" to work around `workflow` being a readonly attribute.
+    (this as any).workflow = new TimeSkippingWorkflowClient({
+      ...this.workflow.options,
+      connection: options.connection,
+      enableTimeSkipping: options.enableTimeSkipping,
+    });
+  }
+}
diff --git a/packages/testing/src/ephemeral-server.ts b/packages/testing/src/ephemeral-server.ts
new file mode 100644
index 000000000..0f7c7bee4
--- /dev/null
+++ b/packages/testing/src/ephemeral-server.ts
@@ -0,0 +1,188 @@
+import 'abort-controller/polyfill'; // eslint-disable-line import/no-unassigned-import
+import { Duration, SearchAttributeType } from '@temporalio/common';
+import { msToNumber } from '@temporalio/common/lib/time';
+import { native } from '@temporalio/core-bridge';
+import { SearchAttributeKey } from '@temporalio/common/lib/search-attributes';
+import pkg from './pkg';
+
+// Config //////////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Configuration for the Temporal CLI Dev Server.
+ */
+export interface DevServerConfig {
+  type: 'dev-server';
+
+  executable?: EphemeralServerExecutable;
+
+  /**
+   * Sqlite DB filename if persisting or non-persistent if none (default).
+   */
+  dbFilename?: string;
+
+  /**
+   * Namespace to use - created at startup.
+   *
+   * @default "default"
+   */
+  namespace?: string;
+
+  /**
+   * IP to bind to.
+   *
+   * @default localhost
+   */
+  ip?: string;
+
+  /**
+   * Port to listen on; defaults to find a random free port.
+   */
+  port?: number;
+
+  /**
+   * Whether to enable the UI.
+   *
+   * @default true if `uiPort` is set; defaults to `false` otherwise.
+   */
+  ui?: boolean;
+
+  /**
+   * Port to listen on for the UI; if `ui` is true, defaults to `port + 1000`.
+   */
+  uiPort?: number;
+
+  /**
+   * Log format and level
+   * @default { format: "pretty", level" "warn" }
+   */
+  log?: { format: string; level: string };
+
+  /**
+   * Extra args to pass to the executable command.
+   *
+   * Note that the Dev Server implementation may be changed to another one in the future. Therefore, there is no
+   * guarantee that Dev Server options, and particularly those provided through the `extraArgs` array, will continue to
+   * be supported in the future.
+   */
+  extraArgs?: string[];
+
+  /**
+   * Search attributes to be registered with the dev server.
+   */
+  searchAttributes?: SearchAttributeKey<SearchAttributeType>[];
+}
+
+/**
+ * Configuration for the time-skipping test server.
+ */
+export interface TimeSkippingServerConfig {
+  type: 'time-skipping';
+
+  executable?: EphemeralServerExecutable;
+
+  /**
+   * Optional port to listen on, defaults to find a random free port.
+   */
+  port?: number;
+
+  /**
+   * Extra args to pass to the executable command.
+   *
+   * Note that the Test Server implementation may be changed to another one in the future. Therefore, there is
+   * no guarantee that server options, and particularly those provided through the `extraArgs` array, will continue to
+   * be supported in the future.
+   */
+  extraArgs?: string[];
+}
+
+/**
+ * Which version of the executable to run.
+ */
+export type EphemeralServerExecutable =
+  | {
+      type: 'cached-download';
+      /**
+       * Download destination directory or the system's temp directory if none set.
+       */
+      downloadDir?: string;
+      /**
+       * Optional version, can be set to a specific server release or "default" or "latest".
+       *
+       * At the time of writing the the server is released as part of the
+       * Java SDK - (https://github.com/temporalio/sdk-java/releases).
+       *
+       * @default "default" - get the best version for the current SDK version.
+       */
+      version?: string;
+
+      /** How long to cache the download for. Default to 1 day. */
+      ttl?: Duration;
+    }
+  | {
+      type: 'existing-path';
+      /** Path to executable */
+      path: string;
+    };
+
+// Compile Config //////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * @internal
+ */
+export function toNativeEphemeralServerConfig(
+  server: DevServerConfig | TimeSkippingServerConfig
+): native.EphemeralServerConfig {
+  switch (server.type) {
+    case 'dev-server':
+      return {
+        type: 'dev-server',
+        executable: toNativeEphemeralServerExecutableConfig(server.executable),
+        ip: server.ip ?? '127.0.0.1',
+        port: server.port ?? null,
+        ui: server.ui ?? false,
+        uiPort: server.uiPort ?? null,
+        namespace: server.namespace ?? 'default',
+        dbFilename: server.dbFilename ?? null,
+        log: server.log ?? { format: 'pretty', level: 'warn' },
+        extraArgs: server.extraArgs ?? [],
+      };
+
+    case 'time-skipping':
+      return {
+        type: 'time-skipping',
+        executable: toNativeEphemeralServerExecutableConfig(server.executable),
+        port: server.port ?? null,
+        extraArgs: server.extraArgs ?? [],
+      };
+
+    default:
+      throw new TypeError(`Unsupported server type: ${String((server as any).type)}`);
+  }
+}
+
+/**
+ * @internal
+ */
+function toNativeEphemeralServerExecutableConfig(
+  executable: EphemeralServerExecutable = { type: 'cached-download' }
+): native.EphemeralServerExecutableConfig {
+  switch (executable.type) {
+    case 'cached-download':
+      return {
+        type: 'cached-download',
+        downloadDir: executable.downloadDir ?? null,
+        version: executable.version ?? 'default',
+        ttl: msToNumber(executable.ttl ?? '1d'),
+        sdkVersion: pkg.version,
+      };
+
+    case 'existing-path':
+      return {
+        type: 'existing-path',
+        path: executable.path,
+      };
+
+    default:
+      throw new TypeError(`Unsupported server executable type: ${String((executable as any).type)}`);
+  }
+}
diff --git a/packages/testing/src/index.ts b/packages/testing/src/index.ts
index ff56e6165..d00594ce4 100644
--- a/packages/testing/src/index.ts
+++ b/packages/testing/src/index.ts
@@ -8,110 +8,34 @@
  * @module
  */
 
-import 'abort-controller/polyfill'; // eslint-disable-line import/no-unassigned-import
 import path from 'node:path';
-import events from 'node:events';
-import * as activity from '@temporalio/activity';
-import {
-  AsyncCompletionClient,
-  Client,
-  ClientOptions,
-  WorkflowClient,
-  WorkflowClientOptions,
-  WorkflowResultOptions,
-} from '@temporalio/client';
-import {
-  ActivityFunction,
-  Duration,
-  SdkComponent,
-  Logger,
-  defaultFailureConverter,
-  defaultPayloadConverter,
-  TypedSearchAttributes,
-} from '@temporalio/common';
-import { msToNumber, msToTs, tsToMs } from '@temporalio/common/lib/time';
-import { ActivityInterceptorsFactory, DefaultLogger, NativeConnection, Runtime } from '@temporalio/worker';
-import { withMetadata } from '@temporalio/worker/lib/logger';
-import { Activity } from '@temporalio/worker/lib/activity';
-import {
-  EphemeralServer,
-  EphemeralServerConfig,
-  getEphemeralServerTarget,
-  DevServerConfig,
-  TimeSkippingServerConfig,
-} from '@temporalio/core-bridge';
-import { filterNullAndUndefined } from '@temporalio/common/lib/internal-non-workflow';
-import { Connection, TestService } from './connection';
 
-export { TimeSkippingServerConfig, DevServerConfig, EphemeralServerExecutable } from '@temporalio/core-bridge';
-export { EphemeralServerConfig };
-
-export interface TimeSkippingWorkflowClientOptions extends WorkflowClientOptions {
-  connection: Connection;
-  enableTimeSkipping: boolean;
-}
-
-export interface TestEnvClientOptions extends ClientOptions {
-  connection: Connection;
-  enableTimeSkipping: boolean;
-}
-
-/**
- * A client with the exact same API as the "normal" client with 1 exception,
- * When this client waits on a Workflow's result, it will enable time skipping
- * in the test server.
- */
-export class TimeSkippingWorkflowClient extends WorkflowClient {
-  protected readonly testService: TestService;
-  protected readonly enableTimeSkipping: boolean;
-
-  constructor(options: TimeSkippingWorkflowClientOptions) {
-    super(options);
-    this.enableTimeSkipping = options.enableTimeSkipping;
-    this.testService = options.connection.testService;
-  }
-
-  /**
-   * Gets the result of a Workflow execution.
-   *
-   * @see {@link WorkflowClient.result}
-   */
-  override async result<T>(
-    workflowId: string,
-    runId?: string | undefined,
-    opts?: WorkflowResultOptions | undefined
-  ): Promise<T> {
-    if (this.enableTimeSkipping) {
-      await this.testService.unlockTimeSkipping({});
-      try {
-        return await super.result(workflowId, runId, opts);
-      } finally {
-        await this.testService.lockTimeSkipping({});
-      }
-    } else {
-      return await super.result(workflowId, runId, opts);
-    }
-  }
-}
-
-/**
- * A client with the exact same API as the "normal" client with one exception:
- * when `TestEnvClient.workflow` (an instance of {@link TimeSkippingWorkflowClient}) waits on a Workflow's result, it will enable time skipping
- * in the Test Server.
- */
-class TestEnvClient extends Client {
-  constructor(options: TestEnvClientOptions) {
-    super(options);
-
-    // Recreate the client (this isn't optimal but it's better than adding public methods just for testing).
-    // NOTE: we cast to "any" to work around `workflow` being a readonly attribute.
-    (this as any).workflow = new TimeSkippingWorkflowClient({
-      ...this.workflow.options,
-      connection: options.connection,
-      enableTimeSkipping: options.enableTimeSkipping,
-    });
-  }
-}
+export {
+  TestWorkflowEnvironment,
+  type LocalTestWorkflowEnvironmentOptions,
+  type TimeSkippingTestWorkflowEnvironmentOptions,
+} from './testing-workflow-environment';
+
+export {
+  type DevServerConfig,
+  type TimeSkippingServerConfig,
+  type EphemeralServerExecutable,
+} from './ephemeral-server';
+
+export {
+  // FIXME: Revise the pertinence of these types
+  type ClientOptionsForTestEnv,
+  type TestEnvClientOptions,
+  type TimeSkippingWorkflowClientOptions,
+  TestEnvClient,
+  TimeSkippingWorkflowClient,
+} from './client';
+
+export {
+  type MockActivityEnvironmentOptions,
+  MockActivityEnvironment,
+  defaultActivityInfo,
+} from './mocking-activity-environment';
 
 /**
  * Convenience workflow interceptors
@@ -120,354 +44,3 @@ class TestEnvClient extends Client {
  * retryable `ApplicationFailure`s.
  */
 export const workflowInterceptorModules = [path.join(__dirname, 'assert-to-failure-interceptor')];
-
-/**
- * Subset of the "normal" client options that are used to create a client for the test environment.
- */
-export type ClientOptionsForTestEnv = Omit<ClientOptions, 'namespace' | 'connection'>;
-
-/**
- * Options for {@link TestWorkflowEnvironment.create}
- */
-export type TestWorkflowEnvironmentOptions = {
-  server: EphemeralServerConfig;
-  client?: ClientOptionsForTestEnv;
-};
-
-/**
- * Options for {@link TestWorkflowEnvironment.createTimeSkipping}
- */
-export type TimeSkippingTestWorkflowEnvironmentOptions = {
-  server?: Omit<TimeSkippingServerConfig, 'type'>;
-  client?: ClientOptionsForTestEnv;
-};
-
-/**
- * Options for {@link TestWorkflowEnvironment.createLocal}
- */
-export type LocalTestWorkflowEnvironmentOptions = {
-  server?: Omit<DevServerConfig, 'type'>;
-  client?: ClientOptionsForTestEnv;
-};
-
-export type TestWorkflowEnvironmentOptionsWithDefaults = Required<TestWorkflowEnvironmentOptions>;
-
-function addDefaults(opts: TestWorkflowEnvironmentOptions): TestWorkflowEnvironmentOptionsWithDefaults {
-  return {
-    client: {},
-    ...opts,
-  };
-}
-
-/**
- * An execution environment for running Workflow integration tests.
- *
- * Runs an external server.
- * By default, the Java test server is used which supports time skipping.
- */
-export class TestWorkflowEnvironment {
-  /**
-   * Namespace used in this environment (taken from {@link TestWorkflowEnvironmentOptions})
-   */
-  public readonly namespace?: string;
-  /**
-   * Get an established {@link Connection} to the ephemeral server
-   */
-  public readonly connection: Connection;
-
-  /**
-   * A {@link TestEnvClient} for interacting with the ephemeral server
-   */
-  public readonly client: Client;
-
-  /**
-   * An {@link AsyncCompletionClient} for interacting with the test server
-   *
-   * @deprecated - use `client.activity` instead
-   */
-  public readonly asyncCompletionClient: AsyncCompletionClient;
-
-  /**
-   * A {@link TimeSkippingWorkflowClient} for interacting with the test server
-   *
-   * @deprecated - use `client.workflow` instead
-   */
-  public readonly workflowClient: WorkflowClient;
-
-  /**
-   * A {@link NativeConnection} for interacting with the test server.
-   *
-   * Use this connection when creating Workers for testing.
-   */
-  public readonly nativeConnection: NativeConnection;
-
-  protected constructor(
-    public readonly options: TestWorkflowEnvironmentOptionsWithDefaults,
-    public readonly supportsTimeSkipping: boolean,
-    protected readonly server: EphemeralServer,
-    connection: Connection,
-    nativeConnection: NativeConnection,
-    namespace: string | undefined
-  ) {
-    this.connection = connection;
-    this.nativeConnection = nativeConnection;
-    this.namespace = namespace;
-    this.client = new TestEnvClient({
-      connection,
-      namespace: this.namespace,
-      enableTimeSkipping: supportsTimeSkipping,
-      ...options.client,
-    });
-    // eslint-disable-next-line deprecation/deprecation
-    this.asyncCompletionClient = this.client.activity;
-    // eslint-disable-next-line deprecation/deprecation
-    this.workflowClient = this.client.workflow;
-  }
-
-  /**
-   * Start a time skipping workflow environment.
-   *
-   * This environment automatically skips to the next events in time when a workflow handle's `result` is awaited on
-   * (which includes {@link WorkflowClient.execute}). Before the result is awaited on, time can be manually skipped
-   * forward using {@link sleep}. The currently known time can be obtained via {@link currentTimeMs}.
-   *
-   * This environment will be powered by the Temporal Time Skipping Test Server (part of the [Java SDK](https://github.com/temporalio/sdk-java)).
-   * Note that the Time Skipping Test Server does not support full capabilities of the regular Temporal Server, and may
-   * occasionally present different behaviors. For general Workflow testing, it is generally preferable to use {@link createLocal}
-   * instead.
-   *
-   * Users can reuse this environment for testing multiple independent workflows, but not concurrently. Time skipping,
-   * which is automatically done when awaiting a workflow result and manually done on sleep, is global to the
-   * environment, not to the workflow under test. We highly recommend running tests serially when using a single
-   * environment or creating a separate environment per test.
-   *
-   * By default, the latest release of the Test Serveer will be downloaded and cached to a temporary directory
-   * (e.g. `$TMPDIR/temporal-test-server-sdk-typescript-*` or `%TEMP%/temporal-test-server-sdk-typescript-*.exe`). Note
-   * that existing cached binairies will be reused without validation that they are still up-to-date, until the SDK
-   * itself is updated. Alternatively, a specific version number of the Test Server may be provided, or the path to an
-   * existing Test Server binary may be supplied; see {@link LocalTestWorkflowEnvironmentOptions.server.executable}.
-   *
-   * Note that the Test Server implementation may be changed to another one in the future. Therefore, there is no
-   * guarantee that Test Server options, and particularly those provided through the `extraArgs` array, will continue to
-   * be supported in the future.
-   *
-   * IMPORTANT: At this time, the Time Skipping Test Server is not supported on ARM platforms. Execution on Apple
-   * silicon Macs will work if Rosetta 2 is installed.
-   */
-  static async createTimeSkipping(opts?: TimeSkippingTestWorkflowEnvironmentOptions): Promise<TestWorkflowEnvironment> {
-    return await this.create({
-      server: { type: 'time-skipping', ...opts?.server },
-      client: opts?.client,
-      supportsTimeSkipping: true,
-    });
-  }
-
-  /**
-   * Start a full Temporal server locally.
-   *
-   * This environment is good for testing full server capabilities, but does not support time skipping like
-   * {@link createTimeSkipping} does. {@link supportsTimeSkipping} will always return `false` for this environment.
-   * {@link sleep} will sleep the actual amount of time and {@link currentTimeMs} will return the current time.
-   *
-   * This local environment will be powered by [Temporal CLI](https://github.com/temporalio/cli), which is a
-   * self-contained executable for Temporal. By default, Temporal's database will not be persisted to disk, and no UI
-   * will be launched.
-   *
-   * By default, the latest release of the CLI will be downloaded and cached to a temporary directory
-   * (e.g. `$TMPDIR/temporal-sdk-typescript-*` or `%TEMP%/temporal-sdk-typescript-*.exe`). Note that existing cached
-   * binairies will be reused without validation that they are still up-to-date, until the SDK itself is updated.
-   * Alternatively, a specific version number of the CLI may be provided, or the path to an existing CLI binary may be
-   * supplied; see {@link LocalTestWorkflowEnvironmentOptions.server.executable}.
-   *
-   * Note that the Dev Server implementation may be changed to another one in the future. Therefore, there is no
-   * guarantee that Dev Server options, and particularly those provided through the `extraArgs` array, will continue to
-   * be supported in the future.
-   */
-  static async createLocal(opts?: LocalTestWorkflowEnvironmentOptions): Promise<TestWorkflowEnvironment> {
-    return await this.create({
-      server: { type: 'dev-server', ...opts?.server },
-      client: opts?.client,
-      namespace: opts?.server?.namespace,
-      supportsTimeSkipping: false,
-    });
-  }
-
-  /**
-   * Create a new test environment
-   */
-  private static async create(
-    opts: TestWorkflowEnvironmentOptions & {
-      supportsTimeSkipping: boolean;
-      namespace?: string;
-    }
-  ): Promise<TestWorkflowEnvironment> {
-    const { supportsTimeSkipping, namespace, ...rest } = opts;
-    const optsWithDefaults = addDefaults(filterNullAndUndefined(rest));
-
-    // Add search attributes to CLI server arguments
-    if ('searchAttributes' in optsWithDefaults.server && optsWithDefaults.server.searchAttributes) {
-      let newArgs: string[] = [];
-      for (const { name, type } of optsWithDefaults.server.searchAttributes) {
-        newArgs.push('--search-attribute');
-        newArgs.push(`${name}=${TypedSearchAttributes.toMetadataType(type)}`);
-      }
-      newArgs = newArgs.concat(optsWithDefaults.server.extraArgs ?? []);
-      optsWithDefaults.server.extraArgs = newArgs;
-    }
-
-    const server = await Runtime.instance().createEphemeralServer(optsWithDefaults.server);
-    const address = getEphemeralServerTarget(server);
-
-    const nativeConnection = await NativeConnection.connect({ address });
-    const connection = await Connection.connect({ address });
-
-    return new this(optsWithDefaults, supportsTimeSkipping, server, connection, nativeConnection, namespace);
-  }
-
-  /**
-   * Kill the test server process and close the connection to it
-   */
-  async teardown(): Promise<void> {
-    await this.connection.close();
-    await this.nativeConnection.close();
-    await Runtime.instance().shutdownEphemeralServer(this.server);
-  }
-
-  /**
-   * Wait for `durationMs` in "server time".
-   *
-   * This awaits using regular setTimeout in regular environments, or manually skips time in time-skipping environments.
-   *
-   * Useful for simulating events far into the future like completion of long running activities.
-   *
-   * **Time skippping**:
-   *
-   * The time skippping server toggles between skipped time and normal time depending on what it needs to execute.
-   *
-   * This method is _likely_ to resolve in less than `durationMs` of "real time".
-   *
-   * @param durationMs number of milliseconds or {@link https://www.npmjs.com/package/ms | ms-formatted string}
-   *
-   * @example
-   *
-   * `workflow.ts`
-   *
-   * ```ts
-   * const activities = proxyActivities({ startToCloseTimeout: 2_000_000 });
-   *
-   * export async function raceActivityAndTimer(): Promise<string> {
-   *   return await Promise.race([
-   *     wf.sleep(500_000).then(() => 'timer'),
-   *     activities.longRunning().then(() => 'activity'),
-   *   ]);
-   * }
-   * ```
-   *
-   * `test.ts`
-   *
-   * ```ts
-   * const worker = await Worker.create({
-   *   connection: testEnv.nativeConnection,
-   *   activities: {
-   *     async longRunning() {
-   *       await testEnv.sleep(1_000_000); // <-- sleep called here
-   *     },
-   *   },
-   *   // ...
-   * });
-   * ```
-   */
-  sleep = async (durationMs: Duration): Promise<void> => {
-    if (this.supportsTimeSkipping) {
-      await (this.connection as Connection).testService.unlockTimeSkippingWithSleep({ duration: msToTs(durationMs) });
-    } else {
-      await new Promise((resolve) => setTimeout(resolve, msToNumber(durationMs)));
-    }
-  };
-
-  /**
-   * Get the current time known to this environment.
-   *
-   * For non-time-skipping environments this is simply the system time. For time-skipping environments this is whatever
-   * time has been skipped to.
-   */
-  async currentTimeMs(): Promise<number> {
-    if (this.supportsTimeSkipping) {
-      const { time } = await (this.connection as Connection).testService.getCurrentTime({});
-      return tsToMs(time);
-    } else {
-      return Date.now();
-    }
-  }
-}
-
-export interface MockActivityEnvironmentOptions {
-  interceptors?: ActivityInterceptorsFactory[];
-  logger?: Logger;
-}
-
-/**
- * Used as the default activity info for Activities executed in the {@link MockActivityEnvironment}
- */
-export const defaultActivityInfo: activity.Info = {
-  attempt: 1,
-  taskQueue: 'test',
-  isLocal: false,
-  taskToken: Buffer.from('test'),
-  activityId: 'test',
-  activityType: 'unknown',
-  workflowType: 'test',
-  base64TaskToken: Buffer.from('test').toString('base64'),
-  heartbeatTimeoutMs: undefined,
-  heartbeatDetails: undefined,
-  activityNamespace: 'default',
-  workflowNamespace: 'default',
-  workflowExecution: { workflowId: 'test', runId: 'dead-beef' },
-  scheduledTimestampMs: 1,
-  startToCloseTimeoutMs: 1000,
-  scheduleToCloseTimeoutMs: 1000,
-  currentAttemptScheduledTimestampMs: 1,
-  priority: undefined,
-};
-
-/**
- * An execution environment for testing Activities.
- *
- * Mocks Activity {@link Context | activity.Context} and exposes hooks for cancellation and heartbeats.
- *
- * Note that the `Context` object used by this environment will be reused for all activities that are run in this
- * environment. Consequently, once `cancel()` is called, any further activity that gets executed in this environment
- * will immediately be in a cancelled state.
- */
-export class MockActivityEnvironment extends events.EventEmitter {
-  public cancel: (reason?: any) => void = () => undefined;
-  public readonly context: activity.Context;
-  private readonly activity: Activity;
-
-  constructor(info?: Partial<activity.Info>, opts?: MockActivityEnvironmentOptions) {
-    super();
-    const heartbeatCallback = (details?: unknown) => this.emit('heartbeat', details);
-    const loadedDataConverter = {
-      payloadConverter: defaultPayloadConverter,
-      payloadCodecs: [],
-      failureConverter: defaultFailureConverter,
-    };
-    this.activity = new Activity(
-      { ...defaultActivityInfo, ...info },
-      undefined,
-      loadedDataConverter,
-      heartbeatCallback,
-      withMetadata(opts?.logger ?? new DefaultLogger(), { sdkComponent: SdkComponent.worker }),
-      opts?.interceptors ?? []
-    );
-    this.context = this.activity.context;
-    this.cancel = this.activity.cancel;
-  }
-
-  /**
-   * Run a function in Activity Context
-   */
-  public async run<P extends any[], R, F extends ActivityFunction<P, R>>(fn: F, ...args: P): Promise<R> {
-    return this.activity.runNoEncoding(fn as ActivityFunction<any, any>, { args, headers: {} }) as Promise<R>;
-  }
-}
diff --git a/packages/testing/src/mocking-activity-environment.ts b/packages/testing/src/mocking-activity-environment.ts
new file mode 100644
index 000000000..3240cddba
--- /dev/null
+++ b/packages/testing/src/mocking-activity-environment.ts
@@ -0,0 +1,90 @@
+import 'abort-controller/polyfill'; // eslint-disable-line import/no-unassigned-import
+import events from 'node:events';
+import * as activity from '@temporalio/activity';
+import {
+  ActivityFunction,
+  Logger,
+  SdkComponent,
+  defaultFailureConverter,
+  defaultPayloadConverter,
+} from '@temporalio/common';
+import { ActivityInterceptorsFactory, DefaultLogger } from '@temporalio/worker';
+import { withMetadata } from '@temporalio/worker/lib/logger';
+import { Activity } from '@temporalio/worker/lib/activity';
+
+// Config //////////////////////////////////////////////////////////////////////////////////////////
+
+export interface MockActivityEnvironmentOptions {
+  interceptors?: ActivityInterceptorsFactory[];
+  logger?: Logger;
+}
+
+// Implementation //////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * An execution environment for testing Activities.
+ *
+ * Mocks Activity {@link Context | activity.Context} and exposes hooks for cancellation and heartbeats.
+ *
+ * Note that the `Context` object used by this environment will be reused for all activities that are run in this
+ * environment. Consequently, once `cancel()` is called, any further activity that gets executed in this environment
+ * will immediately be in a cancelled state.
+ */
+export class MockActivityEnvironment extends events.EventEmitter {
+  public cancel: (reason?: any) => void = () => undefined;
+  public readonly context: activity.Context;
+  private readonly activity: Activity;
+
+  constructor(info?: Partial<activity.Info>, opts?: MockActivityEnvironmentOptions) {
+    super();
+    const heartbeatCallback = (details?: unknown) => this.emit('heartbeat', details);
+    const loadedDataConverter = {
+      payloadConverter: defaultPayloadConverter,
+      payloadCodecs: [],
+      failureConverter: defaultFailureConverter,
+    };
+    this.activity = new Activity(
+      { ...defaultActivityInfo, ...info },
+      undefined,
+      loadedDataConverter,
+      heartbeatCallback,
+      withMetadata(opts?.logger ?? new DefaultLogger(), { sdkComponent: SdkComponent.worker }),
+      opts?.interceptors ?? []
+    );
+    this.context = this.activity.context;
+    this.cancel = this.activity.cancel;
+  }
+
+  /**
+   * Run a function in Activity Context
+   */
+  public async run<P extends any[], R, F extends ActivityFunction<P, R>>(fn: F, ...args: P): Promise<R> {
+    return this.activity.runNoEncoding(fn as ActivityFunction<any, any>, { args, headers: {} }) as Promise<R>;
+  }
+}
+
+/**
+ * Used as the default activity info for Activities executed in the {@link MockActivityEnvironment}
+ *
+ * @hidden
+ */
+export const defaultActivityInfo: activity.Info = {
+  attempt: 1,
+  taskQueue: 'test',
+  isLocal: false,
+  taskToken: Buffer.from('test'),
+  activityId: 'test',
+  activityType: 'unknown',
+  workflowType: 'test',
+  base64TaskToken: Buffer.from('test').toString('base64'),
+  heartbeatTimeoutMs: undefined,
+  heartbeatDetails: undefined,
+  activityNamespace: 'default',
+  workflowNamespace: 'default',
+  workflowExecution: { workflowId: 'test', runId: 'dead-beef' },
+  scheduledTimestampMs: 1,
+  startToCloseTimeoutMs: 1000,
+  scheduleToCloseTimeoutMs: 1000,
+  currentAttemptScheduledTimestampMs: 1,
+  priority: undefined,
+};
diff --git a/packages/testing/src/pkg.ts b/packages/testing/src/pkg.ts
new file mode 100644
index 000000000..60ba3e205
--- /dev/null
+++ b/packages/testing/src/pkg.ts
@@ -0,0 +1,7 @@
+// ../package.json is outside of the TS project rootDir which causes TS to complain about this import.
+// We do not want to change the rootDir because it messes up the output structure.
+// eslint-disable-next-line @typescript-eslint/ban-ts-comment
+// @ts-ignore
+import pkg from '../package.json';
+
+export default pkg as { name: string; version: string };
diff --git a/packages/testing/src/testing-workflow-environment.ts b/packages/testing/src/testing-workflow-environment.ts
new file mode 100644
index 000000000..68e11a5e7
--- /dev/null
+++ b/packages/testing/src/testing-workflow-environment.ts
@@ -0,0 +1,306 @@
+import 'abort-controller/polyfill'; // eslint-disable-line import/no-unassigned-import
+import { AsyncCompletionClient, Client, WorkflowClient } from '@temporalio/client';
+import { Duration, TypedSearchAttributes } from '@temporalio/common';
+import { msToNumber, msToTs, tsToMs } from '@temporalio/common/lib/time';
+import { NativeConnection, Runtime } from '@temporalio/worker';
+import { native } from '@temporalio/core-bridge';
+import { filterNullAndUndefined } from '@temporalio/common/lib/internal-non-workflow';
+import { Connection } from './connection';
+import { toNativeEphemeralServerConfig, DevServerConfig, TimeSkippingServerConfig } from './ephemeral-server';
+import { ClientOptionsForTestEnv, TestEnvClient } from './client';
+
+// Config //////////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Options for {@link TestWorkflowEnvironment.createLocal}
+ */
+export type LocalTestWorkflowEnvironmentOptions = {
+  server?: Omit<DevServerConfig, 'type'>;
+  client?: ClientOptionsForTestEnv;
+};
+
+/**
+ * Options for {@link TestWorkflowEnvironment.createTimeSkipping}
+ */
+export type TimeSkippingTestWorkflowEnvironmentOptions = {
+  server?: Omit<TimeSkippingServerConfig, 'type'>;
+  client?: ClientOptionsForTestEnv;
+};
+
+// Implementation //////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * An execution environment for running Workflow integration tests.
+ *
+ * Runs an external server.
+ * By default, the Java test server is used which supports time skipping.
+ */
+export class TestWorkflowEnvironment {
+  /**
+   * Namespace used in this environment (taken from {@link TestWorkflowEnvironmentOptions})
+   */
+  public readonly namespace?: string;
+  /**
+   * Get an established {@link Connection} to the ephemeral server
+   */
+  public readonly connection: Connection;
+
+  /**
+   * A {@link TestEnvClient} for interacting with the ephemeral server
+   */
+  public readonly client: Client;
+
+  /**
+   * An {@link AsyncCompletionClient} for interacting with the test server
+   *
+   * @deprecated - use `client.activity` instead
+   */
+  public readonly asyncCompletionClient: AsyncCompletionClient;
+
+  /**
+   * A {@link TimeSkippingWorkflowClient} for interacting with the test server
+   *
+   * @deprecated - use `client.workflow` instead
+   */
+  public readonly workflowClient: WorkflowClient;
+
+  /**
+   * A {@link NativeConnection} for interacting with the test server.
+   *
+   * Use this connection when creating Workers for testing.
+   */
+  public readonly nativeConnection: NativeConnection;
+
+  protected constructor(
+    private readonly runtime: Runtime,
+    public readonly options: TestWorkflowEnvironmentOptionsWithDefaults,
+    public readonly supportsTimeSkipping: boolean,
+    protected readonly server: native.EphemeralServer,
+    connection: Connection,
+    nativeConnection: NativeConnection,
+    namespace: string | undefined
+  ) {
+    this.connection = connection;
+    this.nativeConnection = nativeConnection;
+    this.namespace = namespace;
+    this.client = new TestEnvClient({
+      connection,
+      namespace: this.namespace,
+      enableTimeSkipping: supportsTimeSkipping,
+      ...options.client,
+    });
+    // eslint-disable-next-line deprecation/deprecation
+    this.asyncCompletionClient = this.client.activity;
+    // eslint-disable-next-line deprecation/deprecation
+    this.workflowClient = this.client.workflow;
+  }
+
+  /**
+   * Start a time skipping workflow environment.
+   *
+   * This environment automatically skips to the next events in time when a workflow handle's `result` is awaited on
+   * (which includes {@link WorkflowClient.execute}). Before the result is awaited on, time can be manually skipped
+   * forward using {@link sleep}. The currently known time can be obtained via {@link currentTimeMs}.
+   *
+   * This environment will be powered by the Temporal Time Skipping Test Server (part of the [Java SDK](https://github.com/temporalio/sdk-java)).
+   * Note that the Time Skipping Test Server does not support full capabilities of the regular Temporal Server, and may
+   * occasionally present different behaviors. For general Workflow testing, it is generally preferable to use {@link createLocal}
+   * instead.
+   *
+   * Users can reuse this environment for testing multiple independent workflows, but not concurrently. Time skipping,
+   * which is automatically done when awaiting a workflow result and manually done on sleep, is global to the
+   * environment, not to the workflow under test. We highly recommend running tests serially when using a single
+   * environment or creating a separate environment per test.
+   *
+   * By default, the latest release of the Test Serveer will be downloaded and cached to a temporary directory
+   * (e.g. `$TMPDIR/temporal-test-server-sdk-typescript-*` or `%TEMP%/temporal-test-server-sdk-typescript-*.exe`). Note
+   * that existing cached binairies will be reused without validation that they are still up-to-date, until the SDK
+   * itself is updated. Alternatively, a specific version number of the Test Server may be provided, or the path to an
+   * existing Test Server binary may be supplied; see {@link LocalTestWorkflowEnvironmentOptions.server.executable}.
+   *
+   * Note that the Test Server implementation may be changed to another one in the future. Therefore, there is no
+   * guarantee that Test Server options, and particularly those provided through the `extraArgs` array, will continue to
+   * be supported in the future.
+   *
+   * IMPORTANT: At this time, the Time Skipping Test Server is not supported on ARM platforms. Execution on Apple
+   * silicon Macs will work if Rosetta 2 is installed.
+   */
+  static async createTimeSkipping(opts?: TimeSkippingTestWorkflowEnvironmentOptions): Promise<TestWorkflowEnvironment> {
+    return await this.create({
+      server: { type: 'time-skipping', ...opts?.server },
+      client: opts?.client,
+      supportsTimeSkipping: true,
+    });
+  }
+
+  /**
+   * Start a full Temporal server locally.
+   *
+   * This environment is good for testing full server capabilities, but does not support time skipping like
+   * {@link createTimeSkipping} does. {@link supportsTimeSkipping} will always return `false` for this environment.
+   * {@link sleep} will sleep the actual amount of time and {@link currentTimeMs} will return the current time.
+   *
+   * This local environment will be powered by [Temporal CLI](https://github.com/temporalio/cli), which is a
+   * self-contained executable for Temporal. By default, Temporal's database will not be persisted to disk, and no UI
+   * will be launched.
+   *
+   * By default, the latest release of the CLI will be downloaded and cached to a temporary directory
+   * (e.g. `$TMPDIR/temporal-sdk-typescript-*` or `%TEMP%/temporal-sdk-typescript-*.exe`). Note that existing cached
+   * binairies will be reused without validation that they are still up-to-date, until the SDK itself is updated.
+   * Alternatively, a specific version number of the CLI may be provided, or the path to an existing CLI binary may be
+   * supplied; see {@link LocalTestWorkflowEnvironmentOptions.server.executable}.
+   *
+   * Note that the Dev Server implementation may be changed to another one in the future. Therefore, there is no
+   * guarantee that Dev Server options, and particularly those provided through the `extraArgs` array, will continue to
+   * be supported in the future.
+   */
+  static async createLocal(opts?: LocalTestWorkflowEnvironmentOptions): Promise<TestWorkflowEnvironment> {
+    return await this.create({
+      server: { type: 'dev-server', ...opts?.server },
+      client: opts?.client,
+      namespace: opts?.server?.namespace,
+      supportsTimeSkipping: false,
+    });
+  }
+
+  /**
+   * Create a new test environment
+   */
+  private static async create(
+    opts: TestWorkflowEnvironmentOptions & {
+      supportsTimeSkipping: boolean;
+      namespace?: string;
+    }
+  ): Promise<TestWorkflowEnvironment> {
+    const { supportsTimeSkipping, namespace, ...rest } = opts;
+    const optsWithDefaults = addDefaults(filterNullAndUndefined(rest));
+
+    // Add search attributes to CLI server arguments
+    if ('searchAttributes' in optsWithDefaults.server && optsWithDefaults.server.searchAttributes) {
+      let newArgs: string[] = [];
+      for (const { name, type } of optsWithDefaults.server.searchAttributes) {
+        newArgs.push('--search-attribute');
+        newArgs.push(`${name}=${TypedSearchAttributes.toMetadataType(type)}`);
+      }
+      newArgs = newArgs.concat(optsWithDefaults.server.extraArgs ?? []);
+      optsWithDefaults.server.extraArgs = newArgs;
+    }
+
+    const runtime = Runtime.instance();
+    const server = await runtime.createEphemeralServer(toNativeEphemeralServerConfig(optsWithDefaults.server));
+    const address = native.getEphemeralServerTarget(server);
+
+    const nativeConnection = await NativeConnection.connect({ address });
+    const connection = await Connection.connect({ address });
+
+    return new this(runtime, optsWithDefaults, supportsTimeSkipping, server, connection, nativeConnection, namespace);
+  }
+
+  /**
+   * Kill the test server process and close the connection to it
+   */
+  async teardown(): Promise<void> {
+    await this.connection.close().catch((e) => {
+      console.error(e);
+      /* ignore */
+    });
+    await this.nativeConnection.close().catch((e) => {
+      console.error(e);
+      /* ignore */
+    });
+    await this.runtime.shutdownEphemeralServer(this.server).catch((e) => {
+      console.error(e);
+      /* ignore */
+    });
+    console.log('teardown done');
+  }
+
+  /**
+   * Wait for `durationMs` in "server time".
+   *
+   * This awaits using regular setTimeout in regular environments, or manually skips time in time-skipping environments.
+   *
+   * Useful for simulating events far into the future like completion of long running activities.
+   *
+   * **Time skippping**:
+   *
+   * The time skippping server toggles between skipped time and normal time depending on what it needs to execute.
+   *
+   * This method is _likely_ to resolve in less than `durationMs` of "real time".
+   *
+   * @param durationMs number of milliseconds or {@link https://www.npmjs.com/package/ms | ms-formatted string}
+   *
+   * @example
+   *
+   * `workflow.ts`
+   *
+   * ```ts
+   * const activities = proxyActivities({ startToCloseTimeout: 2_000_000 });
+   *
+   * export async function raceActivityAndTimer(): Promise<string> {
+   *   return await Promise.race([
+   *     wf.sleep(500_000).then(() => 'timer'),
+   *     activities.longRunning().then(() => 'activity'),
+   *   ]);
+   * }
+   * ```
+   *
+   * `test.ts`
+   *
+   * ```ts
+   * const worker = await Worker.create({
+   *   connection: testEnv.nativeConnection,
+   *   activities: {
+   *     async longRunning() {
+   *       await testEnv.sleep(1_000_000); // <-- sleep called here
+   *     },
+   *   },
+   *   // ...
+   * });
+   * ```
+   */
+  sleep = async (durationMs: Duration): Promise<void> => {
+    if (this.supportsTimeSkipping) {
+      await (this.connection as Connection).testService.unlockTimeSkippingWithSleep({ duration: msToTs(durationMs) });
+    } else {
+      await new Promise((resolve) => setTimeout(resolve, msToNumber(durationMs)));
+    }
+  };
+
+  /**
+   * Get the current time known to this environment.
+   *
+   * For non-time-skipping environments this is simply the system time. For time-skipping environments this is whatever
+   * time has been skipped to.
+   */
+  async currentTimeMs(): Promise<number> {
+    if (this.supportsTimeSkipping) {
+      const { time } = await (this.connection as Connection).testService.getCurrentTime({});
+      return tsToMs(time);
+    } else {
+      return Date.now();
+    }
+  }
+}
+
+// Compile Config //////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Options for {@link TestWorkflowEnvironment.create}
+ */
+type TestWorkflowEnvironmentOptions = {
+  server: DevServerConfig | TimeSkippingServerConfig;
+  client?: ClientOptionsForTestEnv;
+};
+
+type TestWorkflowEnvironmentOptionsWithDefaults = Required<TestWorkflowEnvironmentOptions>;
+
+function addDefaults(opts: TestWorkflowEnvironmentOptions): TestWorkflowEnvironmentOptionsWithDefaults {
+  return {
+    client: {},
+    ...opts,
+    server: {
+      ...opts.server,
+    },
+  };
+}
diff --git a/packages/worker/src/connection-options.ts b/packages/worker/src/connection-options.ts
index 961b87146..48e252a29 100644
--- a/packages/worker/src/connection-options.ts
+++ b/packages/worker/src/connection-options.ts
@@ -1,14 +1,14 @@
-import * as native from '@temporalio/core-bridge';
+import { native } from '@temporalio/core-bridge';
 import {
-  normalizeGrpcEndpointAddress,
   joinProtoHostPort,
+  normalizeGrpcEndpointAddress,
+  normalizeTlsConfig,
   parseHttpConnectProxyAddress,
+  ProxyConfig,
+  TLSConfig,
 } from '@temporalio/common/lib/internal-non-workflow';
 import pkg from './pkg';
 
-type TLSConfig = native.TLSConfig;
-type ProxyConfig = native.ProxyConfig;
-
 export { TLSConfig, ProxyConfig };
 
 /**
@@ -61,40 +61,50 @@ export interface NativeConnectionOptions {
   disableErrorCodeMetricTags?: boolean;
 }
 
-export type RequiredNativeConnectionOptions = Omit<
-  Required<NativeConnectionOptions>,
-  'tls' | 'proxy' | 'metadata' | 'apiKey'
-> & {
-  tls?: NativeConnectionOptions['tls'];
-  proxy?: NativeConnectionOptions['proxy'];
-  metadata?: NativeConnectionOptions['metadata'];
-  apiKey?: NativeConnectionOptions['apiKey'];
-  sdkVersion: string;
-};
+// Compile to Native ///////////////////////////////////////////////////////////////////////////////
 
-export function getDefaultConnectionOptions(): RequiredNativeConnectionOptions {
-  return {
-    address: 'localhost:7233',
-    sdkVersion: pkg.version,
-    disableErrorCodeMetricTags: false,
-  };
-}
+export function toNativeClientOptions(options: NativeConnectionOptions): native.ClientOptions {
+  const address = normalizeGrpcEndpointAddress(options.address ?? 'localhost:7233', DEFAULT_TEMPORAL_GRPC_PORT);
+
+  const tlsInput = normalizeTlsConfig(options.tls);
+  const tls: native.TLSConfig | null = tlsInput
+    ? {
+        serverRootCaCertificate: tlsInput.serverRootCACertificate ?? null,
+        clientCertPair: tlsInput.clientCertPair ?? null,
+        serverNameOverride: tlsInput.serverNameOverride ?? null,
+      }
+    : null;
 
-export function compileConnectionOptions(options: RequiredNativeConnectionOptions): RequiredNativeConnectionOptions {
-  const { address, ...rest } = options;
-  const proxyOpts: Partial<RequiredNativeConnectionOptions> = {};
+  let proxy: native.ProxyConfig | null = null;
   if (options.proxy?.targetHost) {
-    const { targetHost: target, basicAuth } = options.proxy;
+    const { targetHost: target } = options.proxy;
     const { hostname: host, port } = parseHttpConnectProxyAddress(target);
-    proxyOpts.proxy = {
+    const basicAuth = options.proxy.basicAuth
+      ? {
+          username: options.proxy.basicAuth.username,
+          password: options.proxy.basicAuth.password,
+        }
+      : null;
+    proxy = {
       type: 'http-connect',
       targetHost: joinProtoHostPort({ hostname: host, port }),
       basicAuth,
     };
   }
+
+  if (options?.apiKey && options.metadata?.['Authorization']) {
+    throw new TypeError(
+      'Both `apiKey` option and `Authorization` header were provided. Only one makes sense to use at a time.'
+    );
+  }
+
   return {
-    ...rest,
-    address: normalizeGrpcEndpointAddress(address, DEFAULT_TEMPORAL_GRPC_PORT),
-    ...proxyOpts,
+    url: tls ? `https://${address}` : `http://${address}`,
+    sdkVersion: pkg.version,
+    tls,
+    proxy,
+    metadata: options.metadata ?? null,
+    apiKey: options.apiKey ?? null,
+    disableErrorCodeMetricTags: options.disableErrorCodeMetricTags ?? false,
   };
 }
diff --git a/packages/worker/src/connection.ts b/packages/worker/src/connection.ts
index 65a151309..49a148fdc 100644
--- a/packages/worker/src/connection.ts
+++ b/packages/worker/src/connection.ts
@@ -1,12 +1,9 @@
-import util from 'node:util';
 import { IllegalStateError } from '@temporalio/common';
-import { Client, Worker, clientUpdateHeaders, TransportError, clientUpdateApiKey } from '@temporalio/core-bridge';
+import { native } from '@temporalio/core-bridge';
+import { TransportError } from './errors';
 import { NativeConnectionOptions } from './connection-options';
 import { Runtime } from './runtime';
 
-const updateHeaders = util.promisify(clientUpdateHeaders);
-const updateApiKey = util.promisify(clientUpdateApiKey);
-
 /**
  * A Native Connection object that delegates calls to the Rust Core binary extension.
  *
@@ -18,20 +15,24 @@ export class NativeConnection {
   /**
    * referenceHolders is used internally by the framework, it can be accessed with `extractReferenceHolders` (below)
    */
-  private readonly referenceHolders = new Set<Worker>();
+  private readonly referenceHolders = new Set<native.Worker>();
 
   /**
    * nativeClient is intentionally left private, framework code can access it with `extractNativeClient` (below)
    */
-  protected constructor(private nativeClient: Client) {}
+  protected constructor(
+    private readonly runtime: Runtime,
+    private readonly nativeClient: native.Client
+  ) {}
 
   /**
    * @deprecated use `connect` instead
    */
   static async create(options?: NativeConnectionOptions): Promise<NativeConnection> {
     try {
-      const client = await Runtime.instance().createNativeClient(options);
-      return new this(client);
+      const runtime = Runtime.instance();
+      const client = await runtime.createNativeClient(options);
+      return new this(runtime, client);
     } catch (err) {
       if (err instanceof TransportError) {
         throw new TransportError(err.message);
@@ -45,8 +46,9 @@ export class NativeConnection {
    */
   static async connect(options?: NativeConnectionOptions): Promise<NativeConnection> {
     try {
-      const client = await Runtime.instance().createNativeClient(options);
-      return new this(client);
+      const runtime = Runtime.instance();
+      const client = await runtime.createNativeClient(options);
+      return new this(runtime, client);
     } catch (err) {
       if (err instanceof TransportError) {
         throw new TransportError(err.message);
@@ -65,7 +67,7 @@ export class NativeConnection {
     if (this.referenceHolders.size > 0) {
       throw new IllegalStateError('Cannot close connection while Workers hold a reference to it');
     }
-    await Runtime.instance().closeNativeClient(this.nativeClient);
+    await this.runtime.closeNativeClient(this.nativeClient);
   }
 
   /**
@@ -74,7 +76,7 @@ export class NativeConnection {
    * Use {@link NativeConnectionOptions.metadata} to set the initial metadata for client creation.
    */
   async setMetadata(metadata: Record<string, string>): Promise<void> {
-    await updateHeaders(this.nativeClient, metadata);
+    native.clientUpdateHeaders(this.nativeClient, metadata);
   }
 
   /**
@@ -84,7 +86,7 @@ export class NativeConnection {
    * Use {@link NativeConnectionOptions.apiKey} to set the initial metadata for client creation.
    */
   async setApiKey(apiKey: string): Promise<void> {
-    await updateApiKey(this.nativeClient, apiKey);
+    native.clientUpdateApiKey(this.nativeClient, apiKey);
   }
 }
 
@@ -93,7 +95,7 @@ export class NativeConnection {
  *
  * Only meant to be used by the framework.
  */
-export function extractNativeClient(conn: NativeConnection): Client {
+export function extractNativeClient(conn: NativeConnection): native.Client {
   return (conn as any).nativeClient;
 }
 
@@ -102,7 +104,7 @@ export function extractNativeClient(conn: NativeConnection): Client {
  *
  * Only meant to be used by the framework.
  */
-export function extractReferenceHolders(conn: NativeConnection): Set<Worker> {
+export function extractReferenceHolders(conn: NativeConnection): Set<native.Worker> {
   return (conn as any).referenceHolders;
 }
 
diff --git a/packages/worker/src/errors.ts b/packages/worker/src/errors.ts
index 3bf4962d7..f0c1f40dd 100644
--- a/packages/worker/src/errors.ts
+++ b/packages/worker/src/errors.ts
@@ -1,6 +1,9 @@
 import { IllegalStateError } from '@temporalio/common';
 import { SymbolBasedInstanceOfError } from '@temporalio/common/lib/type-helpers';
-import { ShutdownError, TransportError, UnexpectedError } from '@temporalio/core-bridge';
+import { errors as bridgeErrors } from '@temporalio/core-bridge';
+
+const { ShutdownError, TransportError, UnexpectedError } = bridgeErrors;
+export { ShutdownError, TransportError, UnexpectedError };
 
 /**
  * Thrown from JS if Worker does not shutdown in configured period
diff --git a/packages/worker/src/index.ts b/packages/worker/src/index.ts
index 9f9b65bd2..7567c2587 100644
--- a/packages/worker/src/index.ts
+++ b/packages/worker/src/index.ts
@@ -8,47 +8,31 @@
  * @module
  */
 
-export {
-  ConsoleLogger,
-  ForwardLogger,
-  Logger as TelemLogger,
-  MetricsExporter,
-  OtelCollectorExporter,
-  PrometheusMetricsExporter,
-  TelemetryOptions,
-  CustomSlotSupplier,
-  SlotInfo,
-  WorkflowSlotInfo,
-  LocalActivitySlotInfo,
-  ActivitySlotInfo,
-  SlotMarkUsedContext,
-  SlotPermit,
-  SlotReleaseContext,
-  SlotReserveContext,
-} from '@temporalio/core-bridge';
 export { NativeConnection } from './connection';
-export { NativeConnectionOptions, RequiredNativeConnectionOptions, TLSConfig } from './connection-options';
+export { NativeConnectionOptions, TLSConfig } from './connection-options';
 export { startDebugReplayer } from './debug-replayer';
 export { IllegalStateError } from '@temporalio/common';
-export {
-  ShutdownError,
-  TransportError,
-  UnexpectedError,
-  SlotSupplier,
-  ResourceBasedSlotOptions,
-  ResourceBasedTunerOptions,
-  FixedSizeSlotSupplier,
-} from '@temporalio/core-bridge';
 export {
   CombinedWorkerRunError,
   CombinedWorkerRunErrorCause,
   GracefulShutdownPeriodExpiredError,
-  UnhandledRejectionError,
   PromiseCompletionTimeoutError,
+  UnhandledRejectionError,
 } from './errors';
 export * from './interceptors';
 export { DefaultLogger, LogEntry, LogLevel, LogMetadata, LogTimestamp, Logger } from './logger';
-export { History, Runtime, RuntimeOptions, makeTelemetryFilterString } from './runtime';
+export { History, Runtime } from './runtime';
+export {
+  RuntimeOptions,
+  makeTelemetryFilterString,
+  ConsoleLogger,
+  ForwardLogger,
+  LogExporterConfig,
+  MetricsExporterConfig,
+  OtelCollectorExporter,
+  PrometheusMetricsExporter,
+  TelemetryOptions,
+} from './runtime-options';
 export * from './sinks';
 export { DataConverter, defaultPayloadConverter, State, Worker, WorkerStatus } from './worker';
 export {
@@ -61,7 +45,25 @@ export {
 } from './worker-options';
 export { ReplayError, ReplayHistoriesIterable, ReplayResult } from './replay';
 export { BundleOptions, bundleWorkflowCode, WorkflowBundleWithSourceMap } from './workflow/bundler';
-export { WorkerTuner } from './worker-tuner';
+export {
+  WorkerTuner,
+  TunerHolder,
+  SlotSupplier,
+  ResourceBasedTuner,
+  ResourceBasedTunerOptions,
+  ResourceBasedSlotOptions,
+  ResourceBasedSlotsForType,
+  FixedSizeSlotSupplier,
+  CustomSlotSupplier,
+  SlotInfo,
+  WorkflowSlotInfo,
+  ActivitySlotInfo,
+  LocalActivitySlotInfo,
+  SlotPermit,
+  SlotReserveContext,
+  SlotMarkUsedContext,
+  SlotReleaseContext,
+} from './worker-tuner';
 
 /* eslint-disable deprecation/deprecation */
 // Anything below this line is deprecated
@@ -130,18 +132,26 @@ export {
   workflowLogAttributes,
 } from '@temporalio/workflow/lib/logs';
 
-export {
-  /**
-   * @deprecated This function is meant for internal usage. Don't use it.
-   */
-  timeOfDayToBigint,
-} from './logger';
-
 export {
   /**
    * @deprecated Import error classes directly
    */
   errors,
+  /**
+   * @deprecated - meant for internal use only
+   * @hidden
+   */
+  ShutdownError,
+  /**
+   * @deprecated - meant for internal use only
+   * @hidden
+   */
+  TransportError,
+  /**
+   * @deprecated - meant for internal use only
+   * @hidden
+   */
+  UnexpectedError,
 } from './errors';
 
 /**
diff --git a/packages/worker/src/logger.ts b/packages/worker/src/logger.ts
index c06a6c36f..3f625538a 100644
--- a/packages/worker/src/logger.ts
+++ b/packages/worker/src/logger.ts
@@ -1,16 +1,30 @@
 import { formatWithOptions } from 'node:util';
 import * as supportsColor from 'supports-color';
-import { getTimeOfDay } from '@temporalio/core-bridge';
+import { native } from '@temporalio/core-bridge';
 import { LogLevel, LogMetadata, Logger } from '@temporalio/common';
 
 /** @deprecated Import from @temporalio/common instead */
 export { LogLevel, LogMetadata, Logger };
 
 export interface LogEntry {
-  level: LogLevel;
+  /**
+   * Log message
+   */
   message: string;
+
+  /**
+   * Log level
+   */
+  level: LogLevel;
+
+  /**
+   * Time since epoch, in nanoseconds.
+   */
   timestampNanos: bigint;
-  /** Custom attributes */
+
+  /**
+   * Custom attributes
+   */
   meta?: LogMetadata;
 }
 
@@ -46,14 +60,6 @@ function defaultLogFunction(entry: LogEntry): void {
   }
 }
 
-/**
- * Takes a `[seconds, nanos]` tuple as returned from getTimeOfDay and turns it into bigint.
- */
-export function timeOfDayToBigint(timeOfDay: [number, number]): bigint {
-  const [seconds, nanos] = timeOfDay;
-  return BigInt(seconds) * 1_000_000_000n + BigInt(nanos);
-}
-
 /**
  * Default worker logger - uses a default log function to log messages to `console.error`.
  * See constructor arguments for customization.
@@ -77,7 +83,7 @@ export class DefaultLogger implements Logger {
         level,
         message,
         meta: Object.keys(rest).length === 0 ? undefined : rest,
-        timestampNanos: timestampNanos ?? timeOfDayToBigint(getTimeOfDay()),
+        timestampNanos: timestampNanos ?? native.getTimeOfDay(),
       });
     }
   }
@@ -175,3 +181,11 @@ class LoggerWithMetadata implements Logger {
     return [...chain, meta];
   }
 }
+
+export interface FlushableLogger extends Logger {
+  flush(): void;
+}
+
+export function isFlushableLogger(logger: Logger): logger is FlushableLogger {
+  return 'flush' in logger && typeof logger.flush === 'function';
+}
diff --git a/packages/worker/src/native-log-forward.ts b/packages/worker/src/native-log-forward.ts
new file mode 100644
index 000000000..2c87218a4
--- /dev/null
+++ b/packages/worker/src/native-log-forward.ts
@@ -0,0 +1,71 @@
+import { Heap } from 'heap-js';
+import { SdkComponent } from '@temporalio/common';
+import { native } from '@temporalio/core-bridge';
+import { DefaultLogger, LogEntry, Logger, LogTimestamp } from './logger';
+
+/**
+ * A logger that buffers logs from both Node.js and Rust Core and emits logs in the right order.
+ *
+ * @internal
+ */
+export class NativeLogCollector {
+  public readonly logger: Logger;
+  protected buffer = new Heap<LogEntry>((a, b) => Number(a.timestampNanos - b.timestampNanos));
+
+  constructor(protected readonly next: Logger) {
+    this.logger = new DefaultLogger('TRACE', (entry) => this.buffer.add(entry));
+    this.receive = this.receive.bind(this);
+  }
+
+  /**
+   * Receive logs pushed from the native layer.
+   *
+   * Called from the native layer; this function is not allowed to throw.
+   */
+  public receive(entries: native.JsonString<native.LogEntry>[]): void {
+    try {
+      for (const entry of entries) {
+        const log = this.convertFromNativeLogEntry(entry);
+        if (log) {
+          this.buffer.add(log);
+        }
+      }
+      this.flush();
+    } catch (e) {
+      console.error('Error in NativeLogCollector.receive()', e);
+    }
+  }
+
+  private convertFromNativeLogEntry(entry: native.JsonString<native.LogEntry>): LogEntry | undefined {
+    try {
+      const log = JSON.parse(entry) as native.LogEntry;
+      const timestampNanos = BigInt(log.timestamp);
+      return {
+        level: log.level,
+        message: log.message,
+        meta: {
+          [LogTimestamp]: timestampNanos,
+          sdkComponent: SdkComponent.core,
+          ...log.fields,
+        },
+        timestampNanos,
+      };
+    } catch (e) {
+      console.error('Error in NativeLogCollector.convertFromNativeLogEntry()', e, entry);
+      return undefined;
+    }
+  }
+
+  /**
+   * Flush all buffered logs into the logger supplied to the constructor
+   */
+  flush(): void {
+    for (const entry of this.buffer) {
+      this.next.log(entry.level, entry.message, {
+        [LogTimestamp]: entry.timestampNanos,
+        ...entry.meta,
+      });
+    }
+    this.buffer.clear();
+  }
+}
diff --git a/packages/worker/src/runtime-options.ts b/packages/worker/src/runtime-options.ts
new file mode 100644
index 000000000..ae6c620d9
--- /dev/null
+++ b/packages/worker/src/runtime-options.ts
@@ -0,0 +1,476 @@
+import { native } from '@temporalio/core-bridge';
+import { Logger, LogLevel } from '@temporalio/common';
+import { Duration, msToNumber } from '@temporalio/common/lib/time';
+import { DefaultLogger } from './logger';
+import { NativeLogCollector } from './native-log-forward';
+
+/**
+ * Options used to create a Temporal Runtime. These are mostly about logging and telemetry.
+ */
+export interface RuntimeOptions {
+  /**
+   * A logger that will receive log messages emitted by the SDK, as well as through the
+   * [Workflow](https://typescript.temporal.io/api/namespaces/workflow#log) and
+   * [Activity](https://typescript.temporal.io/api/namespaces/activity#log) context loggers.
+   *
+   * By default, the Runtime's logger outputs everything to stderr, filtering out
+   * messages below the `INFO` level. To customize this behavior, instantiate a
+   * {@link DefaultLogger} with a different log level and a custom output function. Refer to
+   * [this sample](https://github.com/temporalio/samples-typescript/tree/main/hello-world/src/sample.ts)
+   * for an example.
+   *
+   * Note that by default, log messages emitted from the native side of the SDK are printed directly
+   * to the console, _independently of `RuntimeOptions.logger`_ – that is, this option only applies
+   * to log messages emitted from the TS side of the SDK. See {@link TelemetryOptions.logging} on
+   * how to turn on forwarding of native logs to the TS logger.
+   */
+  logger?: Logger;
+
+  /**
+   * Options for Core-side telemetry, including logs and metrics.
+   */
+  telemetryOptions?: TelemetryOptions;
+
+  /**
+   * Automatically shut down workers on any of these signals.
+   * @default
+   * ```ts
+   * ['SIGINT', 'SIGTERM', 'SIGQUIT', 'SIGUSR2']
+   * ```
+   */
+  shutdownSignals?: NodeJS.Signals[];
+}
+
+// Telemetry Options ///////////////////////////////////////////////////////////////////////////////
+
+export interface TelemetryOptions {
+  /**
+   * A string in the env filter format specified here:
+   * https://docs.rs/tracing-subscriber/0.2.20/tracing_subscriber/struct.EnvFilter.html
+   *
+   * Which determines what tracing data is collected in the Core SDK.
+   *
+   * @deprecated Use `logging.filter` instead
+   */
+  tracingFilter?: string;
+
+  /**
+   * If set to `true`, do not prefix metrics with `temporal_`.
+   *
+   * @deprecated Use `metrics.metricPrefix` instead
+   */
+  noTemporalPrefixForMetrics?: boolean;
+
+  /**
+   * Control where to send log messages emitted by native code.
+   *
+   * ### Log Forwarding
+   *
+   * By default, logs emitted by the native side of the SDK are printed directly to the console,
+   * _independently of `RuntimeOptions.logger`_. To enable forwarding of those logs messages to the
+   * TS side logger, add the `forward` property to the `logging` object.
+   *
+   * For example:
+   *
+   * ```ts
+   * Runtime.install({
+   *   logger: new DefaultLogger('INFO'),
+   *   telemetryOptions: {
+   *     logging: {
+   *       filter: { core: 'INFO', other: 'WARN' },
+   *       forward: {},
+   *     },
+   *   },
+   * });
+   * ```
+   *
+   * Note that forwarded log messages are internally throttled/buffered for a few milliseconds to
+   * reduce overhead incurred by Rust-to-JS calls. In rare cases, this may result in log messages
+   * appearing out of order by a few milliseconds. Users are discouraged from using log forwarding
+   * with verboseness sets to `DEBUG` or `TRACE`.
+   */
+  logging?: LogExporterConfig;
+
+  /**
+   * Control exporting {@link NativeConnection} and {@link Worker} metrics.
+   *
+   * Turned off by default
+   */
+  metrics?: MetricsExporterConfig;
+
+  /**
+   * @deprecated Core SDK tracing is no longer supported. This option is ignored.
+   */
+  tracing?: unknown;
+}
+
+// Log Exporter ////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Configuration for logs emitted by the native side of the SDK.
+ *
+ * @see {@link TelemetryOptions.logging}
+ */
+export type LogExporterConfig = {
+  /**
+   * Determines the verboseness of log output emitted by the native side of the SDK.
+   *
+   * This can be specified either as an (env filter format)[https://docs.rs/tracing-subscriber/0.2.20/tracing_subscriber/struct.EnvFilter.html]
+   * string, or as a {@link CoreLogFilterOptions} object.
+   *
+   *
+   * Note that if log forwarding is enabled, then the configured {@link Runtime.logger} may apply
+   * further filtering on top of this.
+   *
+   *
+   * **BACKWARD COMPATIBILITY**
+   *
+   * If `logging.filter` is missing, the following legacy values (if present) will be used instead (in the given order):
+   * - {@link ForwardLogger.forward.level} => `makeTelemetryFilterString({ core: level, other: level })`
+   * - {@link TelemetryOptions.tracingFilter}
+   * - Default value of `makeTelemetryFilterString({ core: 'WARN', other: 'ERROR'})`
+   *
+   * @default `{ core: 'WARN', other: 'ERROR'}` (with some exceptions, as described in backward compatibility note above).
+   */
+  filter?: string | CoreLogFilterOptions;
+} & Partial<ConsoleLogger | ForwardLogger>;
+
+/**
+ * Log directly to console
+ */
+export interface ConsoleLogger {
+  console: {}; // eslint-disable-line @typescript-eslint/no-empty-object-type
+}
+
+/**
+ * Forward logs to {@link Runtime} logger
+ */
+export interface ForwardLogger {
+  forward: {
+    /**
+     * What level, if any, logs should be forwarded from core at
+     *
+     * @deprecated Use {@link TelemetryOptions.logging.filter} instead
+     */
+    level?: LogLevel;
+  };
+}
+
+/**
+ * Options for configuring the verboseness of log output emitted by the native side of the SDK.
+ */
+export interface CoreLogFilterOptions {
+  /**
+   * Determines which level of verbosity to keep for _SDK Core_'s related events.
+   * Any event with a verbosity level less than that value will be discarded.
+   * Possible values are, in order: 'TRACE' | 'DEBUG' | 'INFO' | 'WARN' | 'ERROR'.
+   */
+  core: LogLevel;
+
+  /**
+   * Determines which level of verbosity to keep for events related to third
+   * party native packages imported by SDK Core. Any event with a verbosity level
+   * less than that value will be discarded. Possible values are, in order:
+   * 'TRACE' | 'DEBUG' | 'INFO' | 'WARN' | 'ERROR'.
+   *
+   * @defaults `'ERROR'`.
+   */
+  other?: LogLevel;
+}
+
+// Metrics Exporter ////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Configuration for exporting metrics emitted by Core.
+ */
+export type MetricsExporterConfig = {
+  /**
+   * Determines if the metrics exporter should use cumulative or delta temporality.
+   * Only applies to OpenTelemetry exporter.
+   *
+   * @deprecated Use 'otel.temporality' instead
+   */
+  temporality?: 'cumulative' | 'delta';
+
+  /**
+   * A prefix to add to all metrics.
+   *
+   * @default 'temporal_'
+   */
+  metricPrefix?: string;
+
+  /**
+   * Tags to add to all metrics emitted by the worker.
+   */
+  globalTags?: Record<string, string>;
+
+  /**
+   * Whether to put the service_name on every metric.
+   *
+   * @default true
+   */
+  attachServiceName?: boolean;
+} & (PrometheusMetricsExporter | OtelCollectorExporter);
+
+/**
+ * OpenTelemetry Collector options for exporting metrics or traces
+ */
+export interface OtelCollectorExporter {
+  otel: {
+    /**
+     * URL of a gRPC OpenTelemetry collector.
+     *
+     * Syntax generally looks like `http://server:4317` or `grpc://server:4317` for OTLP/gRPC exporters,
+     * or `http://server:4318/v1/metrics` for OTLP/HTTP exporters. Make sure to set the `http` option
+     * to `true` for OTLP/HTTP endpoints.
+     *
+     * @format Starts with "grpc://" or "http://" for an unsecured connection (typical),
+     *         or "grpcs://" or "https://" for a TLS connection.
+     * @note The `OTEL_EXPORTER_OTLP_ENDPOINT` environment variable, if set, will override this property.
+     */
+    url: string;
+
+    /**
+     * If set to true, the exporter will use OTLP/HTTP instead of OTLP/gRPC.
+     *
+     * @default false meaning that the exporter will use OTLP/gRPC.
+     */
+    http?: boolean;
+
+    /**
+     * Optional set of HTTP request headers to send to Collector (e.g. for authentication)
+     */
+    headers?: Record<string, string>;
+
+    /**
+     * Specify how frequently in metrics should be exported.
+     *
+     * @format number of milliseconds or {@link https://www.npmjs.com/package/ms | ms-formatted string}
+     * @default 1 second
+     */
+    metricsExportInterval?: Duration;
+
+    /**
+     * If set to true, the exporter will use seconds for durations instead of milliseconds.
+     *
+     * @default false
+     */
+    useSecondsForDurations?: boolean;
+
+    /**
+     * Determines if the metrics exporter should use cumulative or delta temporality.
+
+     * See the [OpenTelemetry specification](https://github.com/open-telemetry/opentelemetry-specification/blob/ce50e4634efcba8da445cc23523243cb893905cb/specification/metrics/datamodel.md#temporality)
+     * for more information.
+     *
+     * @default 'cumulative'
+     */
+    temporality?: 'cumulative' | 'delta';
+
+    /**
+     * Overrides boundary values for histogram metrics.
+     *
+     * The key is the metric name and the value is the list of bucket boundaries.
+     *
+     * For example:
+     *
+     * ```
+     * {
+     *   "request_latency": [1, 5, 10, 25, 50, 100, 250, 500, 1000],
+     * }
+     * ```
+     *
+     * The metric name will apply regardless of name prefixing.
+     *
+     * See [this doc](https://docs.rs/opentelemetry_sdk/latest/opentelemetry_sdk/metrics/enum.Aggregation.html#variant.ExplicitBucketHistogram.field.boundaries)
+     * for the exact meaning of boundaries.
+     */
+    histogramBucketOverrides?: Record<string, number[]>;
+  };
+}
+
+/**
+ * Prometheus metrics exporter options
+ */
+export interface PrometheusMetricsExporter {
+  prometheus: {
+    /**
+     * Address to bind the Prometheus HTTP metrics exporter server
+     * (for example, `0.0.0.0:1234`).
+     *
+     * Metrics will be available for scraping under the standard `/metrics` route.
+     */
+    bindAddress: string;
+    /**
+     * If set to true, all counter names will include a "_total" suffix.
+     *
+     * @default false
+     */
+    countersTotalSuffix?: boolean;
+    /**
+     * If set to true, all histograms will include the unit in their name as a suffix.
+     * EX: "_milliseconds"
+     *
+     * @default false
+     */
+    unitSuffix?: boolean;
+    /**
+     * If set to true, the exporter will use seconds for durations instead of milliseconds.
+     *
+     * @default false
+     */
+    useSecondsForDurations?: boolean;
+
+    /**
+     * Overrides boundary values for histogram metrics.
+     *
+     * The key is the metric name and the value is the list of bucket boundaries.
+     *
+     * For example:
+     *
+     * ```
+     * {
+     *   "request_latency": [1, 5, 10, 25, 50, 100, 250, 500, 1000],
+     * }
+     * ```
+     *
+     * The metric name will apply regardless of name prefixing.
+     *
+     * See [this doc](https://docs.rs/opentelemetry_sdk/latest/opentelemetry_sdk/metrics/enum.Aggregation.html#variant.ExplicitBucketHistogram.field.boundaries)
+     * for the exact meaning of boundaries.
+     */
+    histogramBucketOverrides?: Record<string, number[]>;
+  };
+}
+
+// Compile Options ////////////////////////////////////////////////////////////////////////////////
+
+export interface CompiledRuntimeOptions {
+  shutdownSignals: NodeJS.Signals[];
+  telemetryOptions: native.RuntimeOptions;
+  logger: Logger;
+}
+
+export function compileOptions(options: RuntimeOptions): CompiledRuntimeOptions {
+  // eslint-disable-next-line deprecation/deprecation
+  const { metrics, noTemporalPrefixForMetrics } = options.telemetryOptions ?? {};
+
+  const [logger, logExporter] = compileLoggerOptions(options);
+
+  return {
+    logger,
+    shutdownSignals: options.shutdownSignals ?? ['SIGINT', 'SIGTERM', 'SIGQUIT', 'SIGUSR2'],
+    telemetryOptions: {
+      logExporter,
+      telemetry: {
+        metricPrefix: metrics?.metricPrefix ?? (noTemporalPrefixForMetrics ? '' : 'temporal_'),
+        attachServiceName: metrics?.attachServiceName ?? true,
+      },
+      metricsExporter:
+        metrics && isOtelCollectorExporter(metrics)
+          ? ({
+              type: 'otel',
+              url: metrics.otel.url,
+              protocol: metrics.otel.http ? 'http' : 'grpc',
+              headers: metrics.otel.headers ?? {},
+              metricsExportInterval: msToNumber(metrics.otel.metricsExportInterval ?? '1s'),
+              // eslint-disable-next-line deprecation/deprecation
+              temporality: metrics.otel.temporality ?? metrics.temporality ?? 'cumulative',
+              useSecondsForDurations: metrics.otel.useSecondsForDurations ?? false,
+              histogramBucketOverrides: metrics.otel.histogramBucketOverrides ?? {},
+              globalTags: metrics.globalTags ?? {},
+            } satisfies native.MetricExporterOptions)
+          : metrics && isPrometheusMetricsExporter(metrics)
+            ? ({
+                type: 'prometheus',
+                bindAddress: metrics.prometheus.bindAddress,
+                unitSuffix: metrics.prometheus.unitSuffix ?? false,
+                countersTotalSuffix: metrics.prometheus.countersTotalSuffix ?? false,
+                useSecondsForDurations: metrics.prometheus.useSecondsForDurations ?? false,
+                histogramBucketOverrides: metrics.prometheus.histogramBucketOverrides ?? {},
+                globalTags: metrics.globalTags ?? {},
+              } satisfies native.MetricExporterOptions)
+            : null,
+    },
+  };
+}
+
+function compileLoggerOptions(options: RuntimeOptions): [Logger, native.LogExporterOptions] {
+  // eslint-disable-next-line deprecation/deprecation
+  const { logging, tracingFilter } = options.telemetryOptions ?? {};
+
+  const logger = options.logger ?? new DefaultLogger('INFO');
+
+  // Unfortunately, "filter" has changed place and semantics a few times in the past, and we want to
+  // do our best not to break existing users, so this gets a bit more complex than it should be.
+  const defaultFilter = tracingFilter ?? makeTelemetryFilterString({ core: 'WARN', other: 'ERROR' });
+  let loggingFilter: string | undefined = undefined;
+  if (logging?.filter) {
+    if (typeof logging.filter === 'string') {
+      loggingFilter = logging.filter;
+    } else if (typeof logging.filter === 'object') {
+      loggingFilter = makeTelemetryFilterString(logging.filter);
+    } else {
+      throw new TypeError('Invalid logging filter');
+    }
+  }
+  // eslint-disable-next-line deprecation/deprecation
+  const forwardLevel = (logging as ForwardLogger | undefined)?.forward?.level;
+  const forwardLevelFilter =
+    forwardLevel &&
+    makeTelemetryFilterString({
+      core: forwardLevel,
+      other: forwardLevel,
+    });
+
+  if (logging && isForwardingLogger(logging)) {
+    const collector = new NativeLogCollector(logger);
+    return [
+      collector.logger,
+      {
+        type: 'forward',
+        filter: loggingFilter ?? forwardLevelFilter ?? defaultFilter,
+        receiver: collector.receive,
+      },
+    ];
+  } else {
+    return [
+      logger,
+      {
+        type: 'console',
+        filter: loggingFilter ?? defaultFilter,
+      },
+    ];
+  }
+}
+
+// Utilities //////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * @deprecated Use {@link CoreLogFilterOptions} instead.
+ */
+export type MakeTelemetryFilterStringOptions = CoreLogFilterOptions;
+
+/**
+ * A helper to build a filter string for use in `RuntimeOptions.telemetryOptions.tracingFilter`.
+ *
+ * Note that one may instead simply pass a {@link CoreLogFilterOptions} object directly to
+ * `RuntimeOptions.telemetryOptions.logging.filter`. This function may however still be useful
+ * in some particular use cases and will therefore be kept around.
+ */
+export function makeTelemetryFilterString(options: CoreLogFilterOptions): string {
+  const { core, other } = options;
+  return `${other ?? 'ERROR'},temporal_sdk_core=${core},temporal_client=${core},temporal_sdk=${core}`;
+}
+
+function isOtelCollectorExporter(metrics: MetricsExporterConfig): metrics is OtelCollectorExporter {
+  return 'otel' in metrics && typeof metrics.otel === 'object';
+}
+
+function isPrometheusMetricsExporter(metrics: MetricsExporterConfig): metrics is PrometheusMetricsExporter {
+  return 'prometheus' in metrics && typeof metrics.prometheus === 'object';
+}
+
+function isForwardingLogger(options: LogExporterConfig): boolean {
+  return 'forward' in options && typeof options.forward === 'object';
+}
diff --git a/packages/worker/src/runtime.ts b/packages/worker/src/runtime.ts
index 7d44d534d..0e8911ce1 100644
--- a/packages/worker/src/runtime.ts
+++ b/packages/worker/src/runtime.ts
@@ -1,125 +1,18 @@
-import { promisify } from 'node:util';
 import * as v8 from 'node:v8';
 import * as fs from 'node:fs';
 import * as os from 'node:os';
-import { Heap } from 'heap-js';
-import * as native from '@temporalio/core-bridge';
-import {
-  pollLogs,
-  runtimeShutdown,
-  newClient,
-  newRuntime,
-  TelemetryOptions,
-  CompiledTelemetryOptions,
-  ForwardLogger,
-  MetricsExporter,
-  OtelCollectorExporter,
-} from '@temporalio/core-bridge';
-import { filterNullAndUndefined, normalizeTlsConfig } from '@temporalio/common/lib/internal-non-workflow';
-import { IllegalStateError, LogMetadata, SdkComponent } from '@temporalio/common';
+import { native } from '@temporalio/core-bridge';
+import { filterNullAndUndefined } from '@temporalio/common/lib/internal-non-workflow';
+import { IllegalStateError, Logger, SdkComponent } from '@temporalio/common';
 import { temporal } from '@temporalio/proto';
 import { History } from '@temporalio/common/lib/proto-utils';
-import { msToNumber } from '@temporalio/common/lib/time';
-import { DefaultLogger, LogEntry, Logger, LogTimestamp, timeOfDayToBigint } from './logger';
-import { compileConnectionOptions, getDefaultConnectionOptions, NativeConnectionOptions } from './connection-options';
+import { isFlushableLogger } from './logger';
+import { toNativeClientOptions, NativeConnectionOptions } from './connection-options';
 import { byteArrayToBuffer, toMB } from './utils';
-import pkg from './pkg';
+import { CompiledRuntimeOptions, compileOptions, RuntimeOptions } from './runtime-options';
 
 export { History };
 
-function isForwardingLogger(opts: TelemetryOptions['logging']): opts is ForwardLogger {
-  return Object.hasOwnProperty.call(opts, 'forward');
-}
-
-function isOtelCollectorExporter(opts: MetricsExporter): opts is OtelCollectorExporter {
-  return Object.hasOwnProperty.call(opts, 'otel');
-}
-
-/**
- * Options used to create a Core runtime
- */
-export interface RuntimeOptions {
-  /**
-   * Automatically shut down workers on any of these signals.
-   * @default
-   * ```ts
-   * ['SIGINT', 'SIGTERM', 'SIGQUIT', 'SIGUSR2']
-   * ```
-   */
-  shutdownSignals?: NodeJS.Signals[];
-
-  /** Telemetry options for traces/metrics/logging */
-  telemetryOptions?: TelemetryOptions;
-  /**
-   * Custom logger for logging events from the SDK, by default we log everything to stderr
-   * at the INFO level. See https://docs.temporal.io/typescript/logging/ for more info.
-   */
-  logger?: Logger;
-}
-
-export interface CompiledRuntimeOptions {
-  shutdownSignals: NodeJS.Signals[];
-  telemetryOptions: CompiledTelemetryOptions;
-  logger: Logger;
-}
-
-export interface MakeTelemetryFilterStringOptions {
-  /**
-   * Determines which level of verbosity to keep for _SDK Core_'s related events.
-   * Any event with a verbosity level less than that value will be discarded.
-   * Possible values are, in order: 'TRACE' | 'DEBUG' | 'INFO' | 'WARN' | 'ERROR'.
-   */
-  core: native.LogLevel;
-
-  /**
-   * Determines which level of verbosity to keep for events related to third
-   * party native packages imported by SDK Core. Any event with a verbosity level
-   * less than that value will be discarded. Possible values are, in order:
-   * 'TRACE' | 'DEBUG' | 'INFO' | 'WARN' | 'ERROR'.
-   *
-   * @defaults `'INFO'`
-   */
-  other?: native.LogLevel;
-}
-
-/**
- * A helper to build a filter string for use in `RuntimeOptions.telemetryOptions.tracingFilter`.
- *
- * Example:
- *  ```
- *  telemetryOptions: {
- *    logging: {
- *     filter: makeTelemetryFilterString({ core: 'TRACE', other: 'DEBUG' });
- *     // ...
- *    },
- *  }
- * ```
- */
-export function makeTelemetryFilterString(options: MakeTelemetryFilterStringOptions): string {
-  const { core, other } = { other: 'INFO', ...options };
-  return `${other},temporal_sdk_core=${core},temporal_client=${core},temporal_sdk=${core}`;
-}
-
-/** A logger that buffers logs from both Node.js and Rust Core and emits logs in the right order */
-class BufferedLogger extends DefaultLogger {
-  protected buffer = new Heap<LogEntry>((a, b) => Number(a.timestampNanos - b.timestampNanos));
-
-  constructor(protected readonly next: Logger) {
-    super('TRACE', (entry) => this.buffer.add(entry));
-  }
-
-  /** Flush all buffered logs into the logger supplied to the constructor */
-  flush(): void {
-    for (const entry of this.buffer) {
-      this.next.log(entry.level, entry.message, {
-        ...entry.meta,
-        [LogTimestamp]: entry.timestampNanos,
-      });
-    }
-    this.buffer.clear();
-  }
-}
-
 type TrackedNativeObject = native.Client | native.Worker | native.EphemeralServer;
 
 /**
@@ -128,14 +21,13 @@ type TrackedNativeObject = native.Client | native.Worker | native.EphemeralServe
  * Use {@link install} in order to customize the server connection options or other global process options.
  */
 export class Runtime {
+  public readonly logger: Logger;
+
   /** Track the number of pending creation calls into the tokio runtime to prevent shut down */
   protected pendingCreations = 0;
   /** Track the registered native objects to automatically shutdown when all have been deregistered */
   protected readonly backRefs = new Set<TrackedNativeObject>();
-  protected stopPollingForLogs = false;
-  protected stopPollingForLogsCallback?: () => void;
-  protected readonly logPollPromise: Promise<void>;
-  public readonly logger: Logger;
+
   protected readonly shutdownSignalCallbacks = new Set<() => void>();
   protected state: 'RUNNING' | 'SHUTTING_DOWN' = 'RUNNING';
 
@@ -152,13 +44,7 @@ export class Runtime {
     public readonly native: native.Runtime,
     public readonly options: CompiledRuntimeOptions
   ) {
-    if (this.isForwardingLogs()) {
-      const logger = (this.logger = new BufferedLogger(this.options.logger));
-      this.logPollPromise = this.initLogPolling(logger);
-    } else {
-      this.logger = this.options.logger;
-      this.logPollPromise = Promise.resolve();
-    }
+    this.logger = options.logger;
     this.checkHeapSizeLimit();
     this.setupShutdownHook();
   }
@@ -201,8 +87,8 @@ export class Runtime {
    * Factory function for creating a new Core instance, not exposed because Core is meant to be used as a singleton
    */
   protected static create(options: RuntimeOptions, instantiator: 'install' | 'instance'): Runtime {
-    const compiledOptions = this.compileOptions(options);
-    const runtime = newRuntime(compiledOptions.telemetryOptions);
+    const compiledOptions = compileOptions(options);
+    const runtime = native.newRuntime(compiledOptions.telemetryOptions);
 
     // Remember the provided options in case Core is reinstantiated after being shut down
     this.defaultOptions = options;
@@ -211,129 +97,12 @@ export class Runtime {
     return this._instance;
   }
 
-  // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
-  protected static compileOptions(options: RuntimeOptions): CompiledRuntimeOptions {
-    // eslint-disable-next-line deprecation/deprecation
-    const { logging, metrics, tracingFilter, noTemporalPrefixForMetrics } = options.telemetryOptions ?? {};
-
-    const defaultFilter =
-      tracingFilter ??
-      makeTelemetryFilterString({
-        core: 'WARN',
-        other: 'ERROR',
-      });
-    const loggingFilter = logging?.filter;
-
-    // eslint-disable-next-line deprecation/deprecation
-    const forwardLevel = (logging as ForwardLogger | undefined)?.forward?.level;
-    const forwardLevelFilter =
-      forwardLevel &&
-      makeTelemetryFilterString({
-        core: forwardLevel,
-        other: forwardLevel,
-      });
-
-    return {
-      shutdownSignals: options.shutdownSignals ?? ['SIGINT', 'SIGTERM', 'SIGQUIT', 'SIGUSR2'],
-      telemetryOptions: {
-        logging:
-          !!logging && isForwardingLogger(logging)
-            ? {
-                filter: loggingFilter ?? forwardLevelFilter ?? defaultFilter,
-                forward: {},
-              }
-            : {
-                filter: loggingFilter ?? defaultFilter,
-                console: {},
-              },
-        metrics: metrics && {
-          metricPrefix: metrics.metricPrefix ?? (noTemporalPrefixForMetrics ? '' : 'temporal_'),
-          globalTags: metrics.globalTags,
-          attachServiceName: metrics.attachServiceName ?? true,
-          ...(isOtelCollectorExporter(metrics)
-            ? {
-                otel: {
-                  url: metrics.otel.url,
-                  http: metrics.otel.http ?? false,
-                  headers: metrics.otel.headers ?? {},
-                  metricsExportInterval: msToNumber(metrics.otel.metricsExportInterval ?? '1s'),
-                  // eslint-disable-next-line deprecation/deprecation
-                  temporality: metrics.otel.temporality ?? metrics.temporality ?? 'cumulative',
-                  useSecondsForDurations: metrics.otel.useSecondsForDurations ?? false,
-                  histogramBucketOverrides: metrics.otel.histogramBucketOverrides,
-                },
-              }
-            : {
-                prometheus: {
-                  bindAddress: metrics.prometheus.bindAddress,
-                  unitSuffix: metrics.prometheus.unitSuffix ?? false,
-                  countersTotalSuffix: metrics.prometheus.countersTotalSuffix ?? false,
-                  useSecondsForDurations: metrics.prometheus.useSecondsForDurations ?? false,
-                  histogramBucketOverrides: metrics.prometheus.histogramBucketOverrides,
-                },
-              }),
-        },
-      },
-      logger: options.logger ?? new DefaultLogger('INFO'),
-    };
-  }
-
-  protected async initLogPolling(logger: BufferedLogger): Promise<void> {
-    if (!this.isForwardingLogs()) {
-      return;
-    }
-
-    const poll = promisify(pollLogs);
-    const doPoll = async () => {
-      const logs = await poll(this.native);
-      for (const log of logs) {
-        const meta: LogMetadata = {
-          [LogTimestamp]: timeOfDayToBigint(log.timestamp),
-          sdkComponent: SdkComponent.core,
-          ...log.fields,
-        };
-        logger.log(log.level, log.message, meta);
-      }
-    };
-
-    try {
-      for (;;) {
-        await doPoll();
-        logger.flush();
-        if (this.stopPollingForLogs) {
-          break;
-        }
-        await new Promise<void>((resolve) => {
-          setTimeout(resolve, 3);
-          this.stopPollingForLogsCallback = resolve;
-        });
-      }
-    } catch (error) {
-      // Log using the original logger instead of buffering
-      this.options.logger.warn('Error gathering forwarded logs from core', {
-        error,
-        sdkComponent: SdkComponent.worker,
-      });
-    } finally {
-      logger.flush();
-    }
-  }
-
-  protected isForwardingLogs(): boolean {
-    const logger = this.options.telemetryOptions.logging;
-    return logger != null && isForwardingLogger(logger);
-  }
-
   /**
    * Flush any buffered logs.
-   *
-   * This is a noop in case the instance is configured with
-   * `logForwardingLevel=OFF`.
    */
   flushLogs(): void {
-    if (this.isForwardingLogs()) {
-      const logger = this.logger as BufferedLogger;
-      logger.flush();
+    if (isFlushableLogger(this.logger)) {
+      this.logger.flush();
     }
   }
 
@@ -344,21 +113,11 @@ export class Runtime {
    * @hidden
    */
   public async createNativeClient(options?: NativeConnectionOptions): Promise<native.Client> {
-    const compiledServerOptions = compileConnectionOptions({
-      ...getDefaultConnectionOptions(),
-      ...filterNullAndUndefined(options ?? {}),
-    });
-    if (options?.apiKey && compiledServerOptions.metadata?.['Authorization']) {
-      throw new TypeError(
-        'Both `apiKey` option and `Authorization` header were provided. Only one makes sense to use at a time.'
-      );
-    }
-    const clientOptions = {
-      ...compiledServerOptions,
-      tls: normalizeTlsConfig(compiledServerOptions.tls),
-      url: options?.tls ? `https://${compiledServerOptions.address}` : `http://${compiledServerOptions.address}`,
-    };
-    return await this.createNative(promisify(newClient), this.native, clientOptions);
+    return await this.createNative(
+      native.newClient,
+      this.native,
+      toNativeClientOptions(filterNullAndUndefined(options ?? {}))
+    );
   }
 
   /**
@@ -380,16 +139,20 @@ export class Runtime {
    * @hidden
    */
   public async registerWorker(client: native.Client, options: native.WorkerOptions): Promise<native.Worker> {
-    return await this.createNative(promisify(native.newWorker), client, options);
+    return await this.createNativeNoBackRef(async () => {
+      const worker = native.newWorker(client, options);
+      await native.workerValidate(worker);
+      this.backRefs.add(worker);
+      return worker;
+    });
   }
 
   /** @hidden */
-  public async createReplayWorker(options: native.WorkerOptions): Promise<native.ReplayWorker> {
+  public async createReplayWorker(options: native.WorkerOptions): Promise<[native.Worker, native.HistoryPusher]> {
     return await this.createNativeNoBackRef(async () => {
-      const fn = promisify(native.newReplayWorker);
-      const replayWorker = await fn(this.native, options);
-      this.backRefs.add(replayWorker.worker);
-      return replayWorker;
+      const [worker, pusher] = native.newReplayWorker(this.native, options);
+      this.backRefs.add(worker);
+      return [worker, pusher];
     });
   }
 
@@ -402,7 +165,7 @@ export class Runtime {
    */
   public async pushHistory(pusher: native.HistoryPusher, workflowId: string, history: History): Promise<void> {
     const encoded = byteArrayToBuffer(temporal.api.history.v1.History.encodeDelimited(history).finish());
-    return await promisify(native.pushHistory)(pusher, workflowId, encoded);
+    return await native.pushHistory(pusher, workflowId, encoded);
   }
 
   /**
@@ -423,9 +186,12 @@ export class Runtime {
    * @hidden
    */
   public async deregisterWorker(worker: native.Worker): Promise<void> {
-    native.workerFinalizeShutdown(worker);
-    this.backRefs.delete(worker);
-    await this.shutdownIfIdle();
+    try {
+      await native.workerFinalizeShutdown(worker);
+    } finally {
+      this.backRefs.delete(worker);
+      await this.shutdownIfIdle();
+    }
   }
 
   /**
@@ -435,7 +201,7 @@ export class Runtime {
    * @hidden
    */
   public async createEphemeralServer(options: native.EphemeralServerConfig): Promise<native.EphemeralServer> {
-    return await this.createNative(promisify(native.startEphemeralServer), this.native, options, pkg.version);
+    return await this.createNative(native.startEphemeralServer, this.native, options);
   }
 
   /**
@@ -445,7 +211,7 @@ export class Runtime {
    * @hidden
    */
   public async shutdownEphemeralServer(server: native.EphemeralServer): Promise<void> {
-    await promisify(native.shutdownEphemeralServer)(server);
+    await native.shutdownEphemeralServer(server);
     this.backRefs.delete(server);
     await this.shutdownIfIdle();
   }
@@ -498,13 +264,16 @@ export class Runtime {
    * @hidden
    */
   public async shutdown(): Promise<void> {
-    delete Runtime._instance;
-    this.teardownShutdownHook();
-    this.stopPollingForLogs = true;
-    this.stopPollingForLogsCallback?.();
-    // This will effectively drain all logs
-    await this.logPollPromise;
-    await promisify(runtimeShutdown)(this.native);
+    if (this.native === undefined) return;
+    try {
+      delete Runtime._instance;
+      this.teardownShutdownHook();
+      // native.runtimeShutdown(this.native);
+      (this as any).native = undefined;
+      this.flushLogs();
+    } finally {
+      delete (this as any).native;
+    }
   }
 
   /**
diff --git a/packages/worker/src/utils.ts b/packages/worker/src/utils.ts
index 62b8198e0..22f77fb44 100644
--- a/packages/worker/src/utils.ts
+++ b/packages/worker/src/utils.ts
@@ -7,8 +7,8 @@ export function toMB(bytes: number, fractionDigits = 2): string {
   return (bytes / 1024 / 1024).toFixed(fractionDigits);
 }
 
-export function byteArrayToBuffer(array: Uint8Array): ArrayBuffer {
-  return array.buffer.slice(array.byteOffset, array.byteLength + array.byteOffset);
+export function byteArrayToBuffer(array: Uint8Array): Buffer {
+  return Buffer.from(array, array.byteOffset, array.byteLength + array.byteOffset);
 }
 
 export function convertToParentWorkflowType(
diff --git a/packages/worker/src/worker-options.ts b/packages/worker/src/worker-options.ts
index 993de4592..ce9946c93 100644
--- a/packages/worker/src/worker-options.ts
+++ b/packages/worker/src/worker-options.ts
@@ -6,8 +6,7 @@ import { Duration, msOptionalToNumber, msToNumber } from '@temporalio/common/lib
 import { loadDataConverter } from '@temporalio/common/lib/internal-non-workflow';
 import { LoggerSinks } from '@temporalio/workflow';
 import { Context } from '@temporalio/activity';
-import { checkExtends } from '@temporalio/common/lib/type-helpers';
-import { WorkerOptions as NativeWorkerOptions, WorkerTuner as NativeWorkerTuner } from '@temporalio/core-bridge';
+import { native } from '@temporalio/core-bridge';
 import { ActivityInboundLogInterceptor } from './activity-log-interceptor';
 import { NativeConnection } from './connection';
 import { CompiledWorkerInterceptors, WorkerInterceptors } from './interceptors';
@@ -19,43 +18,6 @@ import { MiB } from './utils';
 import { WorkflowBundleWithSourceMap } from './workflow/bundler';
 import { asNativeTuner, WorkerTuner } from './worker-tuner';
 
-export type { WebpackConfiguration };
-
-export interface WorkflowBundlePath {
-  codePath: string;
-}
-
-/**
- * Note this no longer contains a source map.
- * The name was preserved to avoid breaking backwards compatibility.
- *
- * @deprecated
- */
-export interface WorkflowBundlePathWithSourceMap {
-  codePath: string;
-  sourceMapPath: string;
-}
-
-export interface WorkflowBundle {
-  code: string;
-}
-
-export type WorkflowBundleOption =
-  | WorkflowBundle
-  | WorkflowBundleWithSourceMap
-  | WorkflowBundlePath
-  | WorkflowBundlePathWithSourceMap; // eslint-disable-line deprecation/deprecation
-
-export function isCodeBundleOption(bundleOpt: WorkflowBundleOption): bundleOpt is WorkflowBundle {
-  const opt = bundleOpt as any; // Cast to access properties without TS complaining
-  return typeof opt.code === 'string';
-}
-
-export function isPathBundleOption(bundleOpt: WorkflowBundleOption): bundleOpt is WorkflowBundlePath {
-  const opt = bundleOpt as any; // Cast to access properties without TS complaining
-  return typeof opt.codePath === 'string';
-}
-
 /**
  * Options to configure the {@link Worker}
  *
@@ -537,68 +499,7 @@ export interface WorkerOptions {
   };
 }
 
-/**
- * WorkerOptions with all of the Worker required attributes
- */
-export type WorkerOptionsWithDefaults = WorkerOptions &
-  Required<
-    Pick<
-      WorkerOptions,
-      | 'namespace'
-      | 'identity'
-      | 'useVersioning'
-      | 'shutdownGraceTime'
-      | 'maxConcurrentWorkflowTaskPolls'
-      | 'maxConcurrentActivityTaskPolls'
-      | 'nonStickyToStickyPollRatio'
-      | 'enableNonLocalActivities'
-      | 'stickyQueueScheduleToStartTimeout'
-      | 'maxCachedWorkflows'
-      | 'workflowThreadPoolSize'
-      | 'maxHeartbeatThrottleInterval'
-      | 'defaultHeartbeatThrottleInterval'
-      | 'showStackTraceSources'
-      | 'debugMode'
-      | 'reuseV8Context'
-      | 'tuner'
-    >
-  > & {
-    interceptors: Required<WorkerInterceptors>;
-
-    /**
-     * Time to wait for result when calling a Workflow isolate function.
-     * @format number of milliseconds or {@link https://www.npmjs.com/package/ms | ms-formatted string}
-     *
-     * This value is not exposed at the moment.
-     *
-     * @default 5s
-     */
-    isolateExecutionTimeout: Duration;
-  };
-
-/**
- * {@link WorkerOptions} where the attributes the Worker requires are required and time units are converted from ms
- * formatted strings to numbers.
- */
-export interface CompiledWorkerOptions
-  extends Omit<WorkerOptionsWithDefaults, 'interceptors' | 'activities' | 'tuner'> {
-  interceptors: CompiledWorkerInterceptors;
-  shutdownGraceTimeMs: number;
-  shutdownForceTimeMs?: number;
-  isolateExecutionTimeoutMs: number;
-  stickyQueueScheduleToStartTimeoutMs: number;
-  maxHeartbeatThrottleIntervalMs: number;
-  defaultHeartbeatThrottleIntervalMs: number;
-  loadedDataConverter: LoadedDataConverter;
-  activities: Map<string, ActivityFunction>;
-  tuner: NativeWorkerTuner;
-}
-
-export type CompiledWorkerOptionsWithBuildId = CompiledWorkerOptions & {
-  buildId: string;
-};
-
-checkExtends<NativeWorkerOptions, CompiledWorkerOptionsWithBuildId>();
+// Replay Worker ///////////////////////////////////////////////////////////////////////////////////
 
 /**
  * {@link WorkerOptions} with inapplicable-to-replay fields removed.
@@ -636,6 +537,47 @@ export interface ReplayWorkerOptions
   replayName?: string;
 }
 
+// Workflow Bundle /////////////////////////////////////////////////////////////////////////////////
+
+export type { WebpackConfiguration };
+
+export interface WorkflowBundlePath {
+  codePath: string;
+}
+
+/**
+ * Note this no longer contains a source map.
+ * The name was preserved to avoid breaking backwards compatibility.
+ *
+ * @deprecated
+ */
+export interface WorkflowBundlePathWithSourceMap {
+  codePath: string;
+  sourceMapPath: string;
+}
+
+export interface WorkflowBundle {
+  code: string;
+}
+
+export type WorkflowBundleOption =
+  | WorkflowBundle
+  | WorkflowBundleWithSourceMap
+  | WorkflowBundlePath
+  | WorkflowBundlePathWithSourceMap; // eslint-disable-line deprecation/deprecation
+
+export function isCodeBundleOption(bundleOpt: WorkflowBundleOption): bundleOpt is WorkflowBundle {
+  const opt = bundleOpt as any; // Cast to access properties without TS complaining
+  return typeof opt.code === 'string';
+}
+
+export function isPathBundleOption(bundleOpt: WorkflowBundleOption): bundleOpt is WorkflowBundlePath {
+  const opt = bundleOpt as any; // Cast to access properties without TS complaining
+  return typeof opt.codePath === 'string';
+}
+
+// Sinks and Interceptors //////////////////////////////////////////////////////////////////////////
+
 /**
  * Build the sink used internally by the SDK to forwards log messages from the Workflow sandbox to an actual logger.
  *
@@ -697,6 +639,69 @@ function compileWorkerInterceptors({
   };
 }
 
+// Compile Options /////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * WorkerOptions with all of the Worker required attributes
+ */
+export type WorkerOptionsWithDefaults = WorkerOptions &
+  Required<
+    Pick<
+      WorkerOptions,
+      | 'namespace'
+      | 'identity'
+      | 'useVersioning'
+      | 'shutdownGraceTime'
+      | 'maxConcurrentWorkflowTaskPolls'
+      | 'maxConcurrentActivityTaskPolls'
+      | 'nonStickyToStickyPollRatio'
+      | 'enableNonLocalActivities'
+      | 'stickyQueueScheduleToStartTimeout'
+      | 'maxCachedWorkflows'
+      | 'workflowThreadPoolSize'
+      | 'maxHeartbeatThrottleInterval'
+      | 'defaultHeartbeatThrottleInterval'
+      | 'showStackTraceSources'
+      | 'debugMode'
+      | 'reuseV8Context'
+      | 'tuner'
+    >
+  > & {
+    interceptors: Required<WorkerInterceptors>;
+
+    /**
+     * Time to wait for result when calling a Workflow isolate function.
+     * @format number of milliseconds or {@link https://www.npmjs.com/package/ms | ms-formatted string}
+     *
+     * This value is not exposed at the moment.
+     *
+     * @default 5s
+     */
+    isolateExecutionTimeout: Duration;
+  };
+
+/**
+ * {@link WorkerOptions} where the attributes the Worker requires are required and time units are converted from ms
+ * formatted strings to numbers.
+ */
+export interface CompiledWorkerOptions
+  extends Omit<WorkerOptionsWithDefaults, 'interceptors' | 'activities' | 'tuner'> {
+  interceptors: CompiledWorkerInterceptors;
+  shutdownGraceTimeMs: number;
+  shutdownForceTimeMs?: number;
+  isolateExecutionTimeoutMs: number;
+  stickyQueueScheduleToStartTimeoutMs: number;
+  maxHeartbeatThrottleIntervalMs: number;
+  defaultHeartbeatThrottleIntervalMs: number;
+  loadedDataConverter: LoadedDataConverter;
+  activities: Map<string, ActivityFunction>;
+  tuner: native.WorkerTunerOptions;
+}
+
+export type CompiledWorkerOptionsWithBuildId = CompiledWorkerOptions & {
+  buildId: string;
+};
+
 function addDefaultWorkerOptions(options: WorkerOptions, logger: Logger): WorkerOptionsWithDefaults {
   const {
     buildId,
@@ -840,6 +845,30 @@ export function compileWorkerOptions(rawOpts: WorkerOptions, logger: Logger): Co
   };
 }
 
+export function toNativeWorkerOptions(opts: CompiledWorkerOptionsWithBuildId): native.WorkerOptions {
+  return {
+    identity: opts.identity,
+    buildId: opts.buildId,
+    useVersioning: opts.useVersioning,
+    taskQueue: opts.taskQueue,
+    namespace: opts.namespace,
+    tuner: opts.tuner,
+    nonStickyToStickyPollRatio: opts.nonStickyToStickyPollRatio,
+    maxConcurrentWorkflowTaskPolls: opts.maxConcurrentWorkflowTaskPolls,
+    maxConcurrentActivityTaskPolls: opts.maxConcurrentActivityTaskPolls,
+    enableNonLocalActivities: opts.enableNonLocalActivities,
+    stickyQueueScheduleToStartTimeout: msToNumber(opts.stickyQueueScheduleToStartTimeout),
+    maxCachedWorkflows: opts.maxCachedWorkflows,
+    maxHeartbeatThrottleInterval: msToNumber(opts.maxHeartbeatThrottleInterval),
+    defaultHeartbeatThrottleInterval: msToNumber(opts.defaultHeartbeatThrottleInterval),
+    maxTaskQueueActivitiesPerSecond: opts.maxTaskQueueActivitiesPerSecond ?? null,
+    maxActivitiesPerSecond: opts.maxActivitiesPerSecond ?? null,
+    shutdownGraceTime: msToNumber(opts.shutdownGraceTime),
+  };
+}
+
+// Utils ///////////////////////////////////////////////////////////////////////////////////////////
+
 function isSet(env: string | undefined): boolean {
   if (env === undefined) return false;
   env = env.toLocaleLowerCase();
diff --git a/packages/worker/src/worker-tuner.ts b/packages/worker/src/worker-tuner.ts
index a5876c75b..22d82d5d7 100644
--- a/packages/worker/src/worker-tuner.ts
+++ b/packages/worker/src/worker-tuner.ts
@@ -1,25 +1,11 @@
-import {
-  ActivitySlotInfo,
-  CustomSlotSupplier,
-  FixedSizeSlotSupplier,
-  LocalActivitySlotInfo,
-  ResourceBasedTunerOptions,
-  SlotInfo,
-  SlotMarkUsedContext,
-  SlotPermit,
-  SlotReleaseContext,
-  SlotReserveContext,
-  SlotSupplier as NativeSlotSupplier,
-  WorkerTuner as NativeWorkerTuner,
-  WorkflowSlotInfo,
-} from '@temporalio/core-bridge';
+import { native } from '@temporalio/core-bridge';
 import { Duration, msToNumber } from '@temporalio/common/lib/time';
 import { Logger } from '@temporalio/common';
 
-export { FixedSizeSlotSupplier, ResourceBasedTunerOptions };
-
 /**
- * Controls how slots for different task types will be handed out.
+ * A worker tuner allows the customization of the performance characteristics of workers by
+ * controlling how "slots" are handed out for different task types. In order to poll for and then
+ * run tasks, a slot must first be reserved by the {@link SlotSupplier} returned by the tuner.
  *
  * @experimental Worker Tuner is an experimental feature and may be subject to change.
  */
@@ -39,9 +25,6 @@ export interface TunerHolder {
 /**
  * Controls how slots are handed out for a specific task type.
  *
- * For now, only {@link ResourceBasedSlotOptions} and {@link FixedSizeSlotSupplier} are supported,
- * but we may add support for custom tuners in the future.
- *
  * @experimental Worker Tuner is an experimental feature and may be subject to change.
  */
 export type SlotSupplier<SI extends SlotInfo> =
@@ -49,15 +32,50 @@ export type SlotSupplier<SI extends SlotInfo> =
   | FixedSizeSlotSupplier
   | CustomSlotSupplier<SI>;
 
+// Resource Based //////////////////////////////////////////////////////////////////////////////////
+
 /**
- * Resource based slot supplier options for a specific kind of slot.
+ * This tuner attempts to maintain certain levels of resource usage when under load. You do not
+ * need more than one instance of this when using it for multiple slot types.
  *
  * @experimental Worker Tuner is an experimental feature and may be subject to change.
  */
-type ResourceBasedSlotsForType = ResourceBasedSlotOptions & {
-  type: 'resource-based';
+export interface ResourceBasedTuner {
+  /**
+   * Options for the tuner
+   */
   tunerOptions: ResourceBasedTunerOptions;
-};
+  /**
+   * Options for workflow task slots. Defaults to a minimum of 2 slots and a maximum of 1000 slots
+   * with no ramp throttle
+   */
+  workflowTaskSlotOptions?: ResourceBasedSlotOptions;
+  /**
+   * Options for activity task slots. Defaults to a minimum of 1 slots and a maximum of 2000 slots
+   * with 50ms ramp throttle
+   */
+  activityTaskSlotOptions?: ResourceBasedSlotOptions;
+  /**
+   * Options for local activity task slots. Defaults to a minimum of 1 slots and a maximum of 2000
+   * slots with 50ms ramp throttle
+   */
+  localActivityTaskSlotOptions?: ResourceBasedSlotOptions;
+}
+
+/**
+ * Options for a {@link ResourceBasedTuner} to control target resource usage
+ *
+ * @experimental Worker Tuner is an experimental feature and may be subject to change.
+ */
+export interface ResourceBasedTunerOptions {
+  // A value between 0 and 1 that represents the target (system) memory usage. It's not recommended
+  // to set this higher than 0.8, since how much memory a workflow may use is not predictable, and
+  // you don't want to encounter OOM errors.
+  targetMemoryUsage: number;
+  // A value between 0 and 1 that represents the target (system) CPU usage. This can be set to 1.0
+  // if desired, but it's recommended to leave some headroom for other processes.
+  targetCpuUsage: number;
+}
 
 /**
  * Options for a specific slot type within a {@link ResourceBasedSlotsForType}
@@ -83,34 +101,174 @@ export interface ResourceBasedSlotOptions {
 }
 
 /**
- * This tuner attempts to maintain certain levels of resource usage when under load. You do not
- * need more than one instance of this when using it for multiple slot types.
+ * Resource based slot supplier options for a specific kind of slot.
  *
  * @experimental Worker Tuner is an experimental feature and may be subject to change.
  */
-export interface ResourceBasedTuner {
+export type ResourceBasedSlotsForType = ResourceBasedSlotOptions & {
+  type: 'resource-based';
+  tunerOptions: ResourceBasedTunerOptions;
+};
+
+// Fixed Size //////////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * A fixed-size slot supplier that will never issue more than a fixed number of slots.
+ *
+ * @experimental Worker Tuner is an experimental feature and may be subject to change.
+ */
+export interface FixedSizeSlotSupplier {
+  type: 'fixed-size';
+  // The maximum number of slots that can be issued
+  numSlots: number;
+}
+
+/**
+ * The interface can be implemented to provide custom slot supplier behavior.
+ *
+ * @experimental Worker Tuner is an experimental feature and may be subject to change.
+ */
+export interface CustomSlotSupplier<SI extends SlotInfo> {
+  type: 'custom';
+
   /**
-   * Options for the tuner
+   * This function is called before polling for new tasks. Your implementation should return a permit
+   * when a slot is available.
+   *
+   * Note: This function is called asynchronously from the Rust side. It should return a Promise that
+   * resolves when a slot is available. You can use async/await or return a Promise directly.
+   *
+   * The only acceptable exception to throw is AbortError, any other exceptions thrown will be
+   * logged and ignored.
+   *
+   * The value inside the returned promise should be an object, however other types will still count
+   * as having issued a permit. Including undefined or null. Returning undefined or null does *not*
+   * mean you have not issued a permit. Implementations are expected to block until a meaningful
+   * permit can be issued.
+   *
+   * @param ctx The context for slot reservation.
+   * @param abortSignal The SDK may decide to abort the reservation request if it's no longer
+   *   needed. Implementations may clean up and then must reject the promise with AbortError.
+   * @returns A promise that resolves to a permit to use the slot which may be populated with your own data.
    */
-  tunerOptions: ResourceBasedTunerOptions;
+  reserveSlot(ctx: SlotReserveContext, abortSignal: AbortSignal): Promise<SlotPermit>;
+
   /**
-   * Options for workflow task slots. Defaults to a minimum of 2 slots and a maximum of 1000 slots
-   * with no ramp throttle
+   * This function is called when trying to reserve slots for "eager" workflow and activity tasks.
+   * Eager tasks are those which are returned as a result of completing a workflow task, rather than
+   * from polling. Your implementation must not block, and if a slot is available, return a permit
+   * to use that slot.
+   *
+   * @param ctx The context for slot reservation.
+   * @returns Maybe a permit to use the slot which may be populated with your own data.
    */
-  workflowTaskSlotOptions?: ResourceBasedSlotOptions;
+  tryReserveSlot(ctx: SlotReserveContext): SlotPermit | null;
+
   /**
-   * Options for activity task slots. Defaults to a minimum of 1 slots and a maximum of 2000 slots
-   * with 50ms ramp throttle
+   * This function is called once a slot is actually being used to process some task, which may be
+   * some time after the slot was reserved originally. For example, if there is no work for a
+   * worker, a number of slots equal to the number of active pollers may already be reserved, but
+   * none of them are being used yet. This call should be non-blocking.
+   *
+   * @param ctx The context for marking a slot as used.
    */
-  activityTaskSlotOptions?: ResourceBasedSlotOptions;
+  markSlotUsed(slot: SlotMarkUsedContext<SI>): void;
+
   /**
-   * Options for local activity task slots. Defaults to a minimum of 1 slots and a maximum of 2000
-   * slots with 50ms ramp throttle
+   * This function is called once a permit is no longer needed. This could be because the task has
+   * finished, whether successfully or not, or because the slot was no longer needed (ex: the number
+   * of active pollers decreased). This call should be non-blocking.
+   *
+   * @param ctx The context for releasing a slot.
    */
-  localActivityTaskSlotOptions?: ResourceBasedSlotOptions;
+  releaseSlot(slot: SlotReleaseContext<SI>): void;
+}
+
+export type SlotInfo = WorkflowSlotInfo | ActivitySlotInfo | LocalActivitySlotInfo;
+
+export interface WorkflowSlotInfo {
+  type: 'workflow';
+  workflowType: string;
+  isSticky: boolean;
+}
+
+export interface ActivitySlotInfo {
+  type: 'activity';
+  activityType: string;
+}
+
+export interface LocalActivitySlotInfo {
+  type: 'local-activity';
+  activityType: string;
+}
+
+/**
+ * A permit to use a slot.
+ *
+ * @experimental Worker Tuner is an experimental feature and may be subject to change.
+ */
+// eslint-disable-next-line @typescript-eslint/no-empty-object-type
+export interface SlotPermit {}
+
+export interface SlotReserveContext {
+  /**
+   * The type of slot trying to be reserved
+   */
+  slotType: SlotInfo['type'];
+  /**
+   * The name of the task queue for which this reservation request is associated
+   */
+  taskQueue: string;
+  /**
+   * The identity of the worker that is requesting the reservation
+   */
+  workerIdentity: string;
+  /**
+   * The build id of the worker that is requesting the reservation
+   */
+  workerBuildId: string;
+  /**
+   * True iff this is a reservation for a sticky poll for a workflow task
+   */
+  isSticky: boolean;
+}
+
+/**
+ * Context for marking a slot as used.
+ *
+ * @experimental Worker Tuner is an experimental feature and may be subject to change.
+ */
+export interface SlotMarkUsedContext<SI extends SlotInfo> {
+  /**
+   * Info about the task that will be using the slot
+   */
+  slotInfo: SI;
+  /**
+   * The permit that was issued when the slot was reserved
+   */
+  permit: SlotPermit;
+}
+
+/**
+ * Context for releasing a slot.
+ *
+ * @experimental Worker Tuner is an experimental feature and may be subject to change.
+ */
+export interface SlotReleaseContext<SI extends SlotInfo> {
+  /**
+   * Info about the task that used this slot, if any. A slot may be released without being used in
+   * the event a poll times out.
+   */
+  slotInfo?: SI;
+  /**
+   * The permit that was issued when the slot was reserved
+   */
+  permit: SlotPermit;
 }
 
-export function asNativeTuner(tuner: WorkerTuner, logger: Logger): NativeWorkerTuner {
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+export function asNativeTuner(tuner: WorkerTuner, logger: Logger): native.WorkerTunerOptions {
   if (isTunerHolder(tuner)) {
     let tunerOptions = undefined;
     const retme = {
@@ -125,7 +283,10 @@ export function asNativeTuner(tuner: WorkerTuner, logger: Logger): NativeWorkerT
     ]) {
       if (isResourceBased(supplier)) {
         if (tunerOptions !== undefined) {
-          if (tunerOptions !== supplier.tunerOptions) {
+          if (
+            tunerOptions.targetCpuUsage !== supplier.tunerOptions.targetCpuUsage ||
+            tunerOptions.targetMemoryUsage !== supplier.tunerOptions.targetMemoryUsage
+          ) {
             throw new TypeError('Cannot construct worker tuner with multiple different tuner options');
           }
         } else {
@@ -143,19 +304,19 @@ export function asNativeTuner(tuner: WorkerTuner, logger: Logger): NativeWorkerT
         type: 'resource-based',
         tunerOptions: tuner.tunerOptions,
         ...wftSO,
-        rampThrottleMs: msToNumber(wftSO.rampThrottle),
+        rampThrottle: msToNumber(wftSO.rampThrottle),
       },
       activityTaskSlotSupplier: {
         type: 'resource-based',
         tunerOptions: tuner.tunerOptions,
         ...atSO,
-        rampThrottleMs: msToNumber(atSO.rampThrottle),
+        rampThrottle: msToNumber(atSO.rampThrottle),
       },
       localActivityTaskSlotSupplier: {
         type: 'resource-based',
         tunerOptions: tuner.tunerOptions,
         ...latSO,
-        rampThrottleMs: msToNumber(latSO.rampThrottle),
+        rampThrottle: msToNumber(latSO.rampThrottle),
       },
     };
   } else {
@@ -167,78 +328,43 @@ const isResourceBasedTuner = (tuner: WorkerTuner): tuner is ResourceBasedTuner =
   Object.hasOwnProperty.call(tuner, 'tunerOptions');
 const isTunerHolder = (tuner: WorkerTuner): tuner is TunerHolder =>
   Object.hasOwnProperty.call(tuner, 'workflowTaskSlotSupplier');
-const isResourceBased = (sup: SlotSupplier<any> | NativeSlotSupplier): sup is ResourceBasedSlotsForType =>
+const isResourceBased = (sup: SlotSupplier<any> | native.SlotSupplierOptions): sup is ResourceBasedSlotsForType =>
   sup.type === 'resource-based';
-const isCustom = (sup: SlotSupplier<any> | NativeSlotSupplier): sup is CustomSlotSupplier<any> => sup.type === 'custom';
+const isCustom = (sup: SlotSupplier<any> | native.SlotSupplierOptions): sup is CustomSlotSupplier<any> =>
+  sup.type === 'custom';
 
 type ActOrWorkflow = 'activity' | 'workflow';
-const abortString = '__ABORTED_BY_CORE__';
-
-class ErrorLoggingSlotSupplier<SI extends SlotInfo> implements CustomSlotSupplier<SI> {
-  readonly type = 'custom';
 
-  constructor(
-    private readonly supplier: CustomSlotSupplier<SI>,
-    private readonly logger: Logger
-  ) {}
-
-  async reserveSlot(ctx: SlotReserveContext, registerAbort: any): Promise<SlotPermit> {
-    const abortController = new AbortController();
-    registerAbort(() => abortController.abort(abortString));
-    return await this.supplier.reserveSlot(ctx, abortController.signal).catch((err) => {
-      if (err !== abortString) {
-        this.logger.error('Error in custom slot supplier `reserveSlot`', err);
-      }
-      throw err;
-    });
-  }
-
-  tryReserveSlot(ctx: SlotReserveContext): SlotPermit | null {
-    try {
-      return this.supplier.tryReserveSlot(ctx);
-    } catch (err: any) {
-      this.logger.error('Error in custom slot supplier `tryReserveSlot`', err);
-    }
-    return null;
-  }
-
-  markSlotUsed(ctx: SlotMarkUsedContext<SI>): void {
-    try {
-      this.supplier.markSlotUsed(ctx);
-    } catch (err: any) {
-      this.logger.error('Error in custom slot supplier `markSlotUsed`', err);
-    }
-  }
-
-  releaseSlot(ctx: SlotReleaseContext<SI>): void {
-    try {
-      this.supplier.releaseSlot(ctx);
-    } catch (err: any) {
-      this.logger.error('Error in custom slot supplier `releaseSlot`', err);
-    }
-  }
-}
+////////////////////////////////////////////////////////////////////////////////////////////////////
 
 function nativeifySupplier<SI extends SlotInfo>(
   supplier: SlotSupplier<SI>,
   kind: ActOrWorkflow,
   logger: Logger
-): NativeSlotSupplier {
+): native.SlotSupplierOptions {
   if (isResourceBased(supplier)) {
     const tunerOptions = supplier.tunerOptions;
     const defaulted = addResourceBasedSlotDefaults(supplier, kind);
     return {
-      ...defaulted,
       type: 'resource-based',
-      tunerOptions,
-      rampThrottleMs: msToNumber(defaulted.rampThrottle),
+      minimumSlots: defaulted.minimumSlots,
+      maximumSlots: defaulted.maximumSlots,
+      rampThrottle: msToNumber(defaulted.rampThrottle),
+      tunerOptions: {
+        targetMemoryUsage: tunerOptions.targetMemoryUsage,
+        targetCpuUsage: tunerOptions.targetCpuUsage,
+      },
     };
   }
+
   if (isCustom(supplier)) {
-    return new ErrorLoggingSlotSupplier(supplier, logger);
+    return new NativeifiedCustomSlotSupplier(supplier, logger);
   }
 
-  return supplier;
+  return {
+    type: 'fixed-size',
+    numSlots: supplier.numSlots,
+  };
 }
 
 function addResourceBasedSlotDefaults(
@@ -259,3 +385,76 @@ function addResourceBasedSlotDefaults(
     };
   }
 }
+
+class NativeifiedCustomSlotSupplier<SI extends SlotInfo> implements CustomSlotSupplier<SI> {
+  readonly type = 'custom';
+
+  constructor(
+    private readonly supplier: CustomSlotSupplier<SI>,
+    private readonly logger: Logger
+  ) {
+    this.reserveSlot = this.reserveSlot.bind(this);
+    this.tryReserveSlot = this.tryReserveSlot.bind(this);
+    this.markSlotUsed = this.markSlotUsed.bind(this);
+    this.releaseSlot = this.releaseSlot.bind(this);
+  }
+
+  async reserveSlot(ctx: SlotReserveContext, abortSignal: AbortSignal): Promise<SlotPermit> {
+    try {
+      const result = await this.supplier.reserveSlot(
+        {
+          slotType: ctx.slotType,
+          taskQueue: ctx.taskQueue,
+          workerIdentity: ctx.workerIdentity,
+          workerBuildId: ctx.workerBuildId,
+          isSticky: ctx.isSticky,
+        },
+        abortSignal
+      );
+      return result;
+    } catch (error) {
+      if (abortSignal.aborted && error !== abortSignal.reason) {
+        this.logger.error('Error in custom slot supplier `reserveSlot`', { error });
+      }
+      throw error;
+    }
+  }
+
+  tryReserveSlot(ctx: SlotReserveContext): SlotPermit | null {
+    try {
+      const result = this.supplier.tryReserveSlot({
+        slotType: ctx.slotType,
+        taskQueue: ctx.taskQueue,
+        workerIdentity: ctx.workerIdentity,
+        workerBuildId: ctx.workerBuildId,
+        isSticky: ctx.isSticky,
+      });
+      return result ?? null;
+    } catch (error) {
+      this.logger.error(`Error in custom slot supplier tryReserveSlot`, { error });
+      return null;
+    }
+  }
+
+  markSlotUsed(ctx: SlotMarkUsedContext<SI>): void {
+    try {
+      this.supplier.markSlotUsed({
+        slotInfo: ctx.slotInfo,
+        permit: ctx.permit,
+      });
+    } catch (error) {
+      this.logger.error(`Error in custom slot supplier markSlotUsed`, { error });
+    }
+  }
+
+  releaseSlot(ctx: SlotReleaseContext<SI>): void {
+    try {
+      this.supplier.releaseSlot({
+        slotInfo: ctx.slotInfo ?? undefined,
+        permit: ctx.permit,
+      });
+    } catch (error) {
+      this.logger.error(`Error in custom slot supplier releaseSlot`, { error });
+    }
+  }
+}
diff --git a/packages/worker/src/worker.ts b/packages/worker/src/worker.ts
index a47a22a36..29ea95a42 100644
--- a/packages/worker/src/worker.ts
+++ b/packages/worker/src/worker.ts
@@ -2,7 +2,6 @@ import crypto from 'node:crypto';
 import fs from 'node:fs/promises';
 import * as path from 'node:path';
 import * as vm from 'node:vm';
-import { promisify } from 'node:util';
 import { EventEmitter, on } from 'node:events';
 import { setTimeout as setTimeoutCallback } from 'node:timers';
 import {
@@ -53,8 +52,7 @@ import {
 } from '@temporalio/common/lib/time';
 import { errorMessage } from '@temporalio/common/lib/type-helpers';
 import { workflowLogAttributes } from '@temporalio/workflow/lib/logs';
-import * as native from '@temporalio/core-bridge';
-import { ShutdownError, UnexpectedError } from '@temporalio/core-bridge';
+import { native } from '@temporalio/core-bridge';
 import { coresdk, temporal } from '@temporalio/proto';
 import { type SinkCall, type WorkflowInfo } from '@temporalio/workflow';
 import { Activity, CancelReason, activityLogAttributes } from './activity';
@@ -79,6 +77,7 @@ import {
   isCodeBundleOption,
   isPathBundleOption,
   ReplayWorkerOptions,
+  toNativeWorkerOptions,
   WorkerOptions,
   WorkflowBundle,
 } from './worker-options';
@@ -89,7 +88,13 @@ import { ReusableVMWorkflowCreator } from './workflow/reusable-vm';
 import { ThreadedVMWorkflowCreator } from './workflow/threaded-vm';
 import { VMWorkflowCreator } from './workflow/vm';
 import { WorkflowBundleWithSourceMapAndFilename } from './workflow/workflow-worker-thread/input';
-import { CombinedWorkerRunError, GracefulShutdownPeriodExpiredError, PromiseCompletionTimeoutError } from './errors';
+import {
+  CombinedWorkerRunError,
+  GracefulShutdownPeriodExpiredError,
+  PromiseCompletionTimeoutError,
+  ShutdownError,
+  UnexpectedError,
+} from './errors';
 
 export { DataConverter, defaultPayloadConverter };
 
@@ -105,19 +110,10 @@ export { DataConverter, defaultPayloadConverter };
  */
 export type State = 'INITIALIZED' | 'RUNNING' | 'STOPPED' | 'STOPPING' | 'DRAINING' | 'DRAINED' | 'FAILED';
 
-type ExtractToPromise<T> = T extends (err: any, result: infer R) => void ? Promise<R> : never;
-// For some reason the lint rule doesn't realize that _I should be ignored
-// eslint-disable-next-line @typescript-eslint/no-unused-vars
-type Last<T extends any[]> = T extends [...infer _I, infer L] ? L : never;
-type LastParameter<F extends (...args: any) => any> = Last<Parameters<F>>;
 type OmitFirst<T> = T extends [any, ...infer REST] ? REST : never;
-type OmitLast<T> = T extends [...infer REST, any] ? REST : never;
 type OmitFirstParam<T> = T extends (...args: any[]) => any
   ? (...args: OmitFirst<Parameters<T>>) => ReturnType<T>
   : never;
-type Promisify<T> = T extends (...args: any[]) => void
-  ? (...args: OmitLast<Parameters<T>>) => ExtractToPromise<LastParameter<T>>
-  : never;
 
 type NonNullableObject<T> = { [P in keyof T]-?: NonNullable<T[P]> };
 
@@ -129,7 +125,7 @@ export type ActivityTaskWithBase64Token = {
 
   // The unaltered protobuf-encoded ActivityTask; kept so that it can be printed
   // out for analysis if decoding fails at a later step.
-  protobufEncodedTask: ArrayBuffer;
+  protobufEncodedTask: Buffer;
 };
 
 interface EvictionWithRunID {
@@ -138,14 +134,14 @@ interface EvictionWithRunID {
 }
 
 export interface NativeWorkerLike {
-  type: 'Worker';
-  initiateShutdown: Promisify<OmitFirstParam<typeof native.workerInitiateShutdown>>;
+  type: 'worker';
+  initiateShutdown: OmitFirstParam<typeof native.workerInitiateShutdown>;
   finalizeShutdown(): Promise<void>;
   flushCoreLogs(): void;
-  pollWorkflowActivation: Promisify<OmitFirstParam<typeof native.workerPollWorkflowActivation>>;
-  pollActivityTask: Promisify<OmitFirstParam<typeof native.workerPollActivityTask>>;
-  completeWorkflowActivation: Promisify<OmitFirstParam<typeof native.workerCompleteWorkflowActivation>>;
-  completeActivityTask: Promisify<OmitFirstParam<typeof native.workerCompleteActivityTask>>;
+  pollWorkflowActivation: OmitFirstParam<typeof native.workerPollWorkflowActivation>;
+  pollActivityTask: OmitFirstParam<typeof native.workerPollActivityTask>;
+  completeWorkflowActivation: OmitFirstParam<typeof native.workerCompleteWorkflowActivation>;
+  completeActivityTask: OmitFirstParam<typeof native.workerCompleteActivityTask>;
   recordActivityHeartbeat: OmitFirstParam<typeof native.workerRecordActivityHeartbeat>;
 }
 
@@ -173,29 +169,29 @@ function addBuildIdIfMissing(options: CompiledWorkerOptions, bundleCode?: string
 }
 
 export class NativeWorker implements NativeWorkerLike {
-  public readonly type = 'Worker';
-  public readonly pollWorkflowActivation: Promisify<OmitFirstParam<typeof native.workerPollWorkflowActivation>>;
-  public readonly pollActivityTask: Promisify<OmitFirstParam<typeof native.workerPollActivityTask>>;
-  public readonly completeWorkflowActivation: Promisify<OmitFirstParam<typeof native.workerCompleteWorkflowActivation>>;
-  public readonly completeActivityTask: Promisify<OmitFirstParam<typeof native.workerCompleteActivityTask>>;
+  public readonly type = 'worker';
+  public readonly pollWorkflowActivation: OmitFirstParam<typeof native.workerPollWorkflowActivation>;
+  public readonly pollActivityTask: OmitFirstParam<typeof native.workerPollActivityTask>;
+  public readonly completeWorkflowActivation: OmitFirstParam<typeof native.workerCompleteWorkflowActivation>;
+  public readonly completeActivityTask: OmitFirstParam<typeof native.workerCompleteActivityTask>;
   public readonly recordActivityHeartbeat: OmitFirstParam<typeof native.workerRecordActivityHeartbeat>;
-  public readonly initiateShutdown: Promisify<OmitFirstParam<typeof native.workerInitiateShutdown>>;
+  public readonly initiateShutdown: OmitFirstParam<typeof native.workerInitiateShutdown>;
 
   public static async create(
     connection: NativeConnection,
     options: CompiledWorkerOptionsWithBuildId
   ): Promise<NativeWorkerLike> {
     const runtime = Runtime.instance();
-    const nativeWorker = await runtime.registerWorker(extractNativeClient(connection), options);
+    const nativeWorker = await runtime.registerWorker(extractNativeClient(connection), toNativeWorkerOptions(options));
     return new NativeWorker(runtime, nativeWorker);
   }
 
   public static async createReplay(options: CompiledWorkerOptionsWithBuildId): Promise<NativeReplayHandle> {
     const runtime = Runtime.instance();
-    const replayer = await runtime.createReplayWorker(options);
+    const [worker, historyPusher] = await runtime.createReplayWorker(toNativeWorkerOptions(options));
     return {
-      worker: new NativeWorker(runtime, replayer.worker),
-      historyPusher: replayer.pusher,
+      worker: new NativeWorker(runtime, worker),
+      historyPusher,
     };
   }
 
@@ -203,12 +199,12 @@ export class NativeWorker implements NativeWorkerLike {
     protected readonly runtime: Runtime,
     protected readonly nativeWorker: native.Worker
   ) {
-    this.pollWorkflowActivation = promisify(native.workerPollWorkflowActivation).bind(undefined, nativeWorker);
-    this.pollActivityTask = promisify(native.workerPollActivityTask).bind(undefined, nativeWorker);
-    this.completeWorkflowActivation = promisify(native.workerCompleteWorkflowActivation).bind(undefined, nativeWorker);
-    this.completeActivityTask = promisify(native.workerCompleteActivityTask).bind(undefined, nativeWorker);
+    this.pollWorkflowActivation = native.workerPollWorkflowActivation.bind(undefined, nativeWorker);
+    this.pollActivityTask = native.workerPollActivityTask.bind(undefined, nativeWorker);
+    this.completeWorkflowActivation = native.workerCompleteWorkflowActivation.bind(undefined, nativeWorker);
+    this.completeActivityTask = native.workerCompleteActivityTask.bind(undefined, nativeWorker);
     this.recordActivityHeartbeat = native.workerRecordActivityHeartbeat.bind(undefined, nativeWorker);
-    this.initiateShutdown = promisify(native.workerInitiateShutdown).bind(undefined, nativeWorker);
+    this.initiateShutdown = native.workerInitiateShutdown.bind(undefined, nativeWorker);
   }
 
   flushCoreLogs(): void {
@@ -464,13 +460,14 @@ export class Worker {
    * This method initiates a connection to the server and will throw (asynchronously) on connection failure.
    */
   public static async create(options: WorkerOptions): Promise<Worker> {
-    const logger = withMetadata(Runtime.instance().logger, {
+    const runtime = Runtime.instance();
+    const logger = withMetadata(runtime.logger, {
       sdkComponent: SdkComponent.worker,
       taskQueue: options.taskQueue ?? 'default',
     });
     const nativeWorkerCtor: NativeWorkerConstructor = this.nativeWorkerCtor;
     const compiledOptions = compileWorkerOptions(options, logger);
-    logger.info('Creating worker', {
+    logger.debug('Creating worker', {
       options: {
         ...compiledOptions,
         ...(compiledOptions.workflowBundle && isCodeBundleOption(compiledOptions.workflowBundle)
@@ -503,7 +500,7 @@ export class Worker {
       throw err;
     }
     extractReferenceHolders(connection).add(nativeWorker);
-    return new this(nativeWorker, workflowCreator, compiledOptionsWithBuildId, logger, connection);
+    return new this(runtime, nativeWorker, workflowCreator, compiledOptionsWithBuildId, logger, connection);
   }
 
   protected static async createWorkflowCreator(
@@ -651,7 +648,8 @@ export class Worker {
       ...options,
     };
     this.replayWorkerCount++;
-    const logger = withMetadata(Runtime.instance().logger, {
+    const runtime = Runtime.instance();
+    const logger = withMetadata(runtime.logger, {
       sdkComponent: 'worker',
       taskQueue: fixedUpOptions.taskQueue,
     });
@@ -663,7 +661,7 @@ export class Worker {
     const workflowCreator = await this.createWorkflowCreator(bundle, compiledOptions, logger);
     const replayHandle = await nativeWorkerCtor.createReplay(addBuildIdIfMissing(compiledOptions, bundle.code));
     return [
-      new this(replayHandle.worker, workflowCreator, compiledOptions, logger, undefined, true),
+      new this(runtime, replayHandle.worker, workflowCreator, compiledOptions, logger, undefined, true),
       replayHandle.historyPusher,
     ];
   }
@@ -721,6 +719,7 @@ export class Worker {
    * Create a new Worker from nativeWorker.
    */
   protected constructor(
+    protected readonly runtime: Runtime,
     protected readonly nativeWorker: NativeWorkerLike,
     /**
      * Optional WorkflowCreator - if not provided, Worker will not poll on Workflows
@@ -794,38 +793,34 @@ export class Worker {
 
   /**
    * Start shutting down the Worker. The Worker stops polling for new tasks and sends
-   * {@link https://typescript.temporal.io/api/namespaces/activity#cancellation | cancellation} (via a
-   * {@link CancelledFailure} with `message` set to `'WORKER_SHUTDOWN'`) to running Activities. Note: if the Activity
-   * accepts cancellation (i.e. re-throws or allows the `CancelledFailure` to be thrown out of the Activity function),
-   * the Activity Task will be marked as failed, not cancelled. It's helpful for the Activity Task to be marked failed
-   * during shutdown because the Server will retry the Activity sooner (than if the Server had to wait for the Activity
-   * Task to time out).
+   * {@link https://typescript.temporal.io/api/namespaces/activity#cancellation | cancellation}
+   * (via a {@link CancelledFailure} with `message` set to `'WORKER_SHUTDOWN'`) to running Activities.
+   * Note: if the Activity accepts cancellation (i.e. re-throws or allows the `CancelledFailure`
+   * to be thrown out of the Activity function), the Activity Task will be marked as failed, not
+   * cancelled. It's helpful for the Activity Task to be marked failed during shutdown because the
+   * Server will retry the Activity sooner (than if the Server had to wait for the Activity Task
+   * to time out).
    *
-   * When called, immediately transitions {@link state} to `'STOPPING'` and asks Core to shut down. Once Core has
-   * confirmed that it's shutting down, the Worker enters `'DRAINING'` state unless the Worker has already been
-   * `'DRAINED'`. Once all currently running Activities and Workflow Tasks have completed, the Worker transitions to
-   * `'STOPPED'`.
+   * When called, immediately transitions {@link state} to `'STOPPING'` and asks Core to shut down.
+   * Once Core has confirmed that it's shutting down, the Worker enters `'DRAINING'` state. It will
+   * stay in that state until both task pollers receive a `ShutdownError`, at which point we'll
+   * transition to `DRAINED` state. Once all currently running Activities and Workflow Tasks have
+   * completed, the Worker transitions to `'STOPPED'`.
    */
   shutdown(): void {
     if (this.state !== 'RUNNING') {
       throw new IllegalStateError(`Not running. Current state: ${this.state}`);
     }
     this.state = 'STOPPING';
-    this.nativeWorker
-      .initiateShutdown()
-      .then(() => {
-        // Core may have already returned a ShutdownError to our pollers in which
-        // case the state would transition to DRAINED
-        if (this.state === 'STOPPING') {
-          this.state = 'DRAINING';
-        }
-      })
-      .catch((error) => {
-        // This is totally unexpected. If we reach this point, something horribly wrong in the Worker
-        // state, and attempt to shutdown gracefully will very likely hang. Just terminate immediately.
-        this.logger.error('Failed to initiate shutdown', { error });
-        this.instantTerminateErrorSubject.error(error);
-      });
+    try {
+      this.nativeWorker.initiateShutdown();
+      this.state = 'DRAINING';
+    } catch (error) {
+      // This is totally unexpected, and indicates there's something horribly wrong with the Worker
+      // state. Attempt to shutdown gracefully will very likely hang, so just terminate immediately.
+      this.logger.error('Failed to initiate shutdown', { error });
+      this.instantTerminateErrorSubject.error(error);
+    }
   }
 
   /**
@@ -1522,7 +1517,7 @@ export class Worker {
   protected workflowPoll$(): Observable<WorkflowActivation> {
     return this.pollLoop$(async () => {
       this.hasOutstandingWorkflowPoll = true;
-      let buffer: ArrayBuffer;
+      let buffer: Buffer;
       try {
         buffer = await this.nativeWorker.pollWorkflowActivation();
       } finally {
@@ -1561,7 +1556,7 @@ export class Worker {
       mergeMap(this.handleWorkflowActivations.bind(this)),
       mergeMap(async (completion) => {
         try {
-          await this.nativeWorker.completeWorkflowActivation(completion.buffer.slice(completion.byteOffset));
+          await this.nativeWorker.completeWorkflowActivation(Buffer.from(completion, completion.byteOffset));
         } catch (error) {
           this.logger.error('Core reported failure in completeWorkflowActivation(). Initiating Worker shutdown.', {
             error,
@@ -1583,7 +1578,7 @@ export class Worker {
   protected activityPoll$(): Observable<ActivityTaskWithBase64Token> {
     return this.pollLoop$(async () => {
       this.hasOutstandingActivityPoll = true;
-      let buffer: ArrayBuffer;
+      let buffer: Buffer;
       try {
         buffer = await this.nativeWorker.pollActivityTask();
       } finally {
@@ -1623,7 +1618,7 @@ export class Worker {
     return this.activityPoll$().pipe(
       this.activityOperator(),
       mergeMap(async (completion) => {
-        await this.nativeWorker.completeActivityTask(completion.buffer.slice(completion.byteOffset));
+        await this.nativeWorker.completeActivityTask(Buffer.from(completion, completion.byteOffset));
       }),
       tap({ complete: () => this.logger.debug('Activity Worker terminated') })
     );
@@ -1734,7 +1729,7 @@ export class Worker {
     const shutdownCallback = () => {
       if (this.state === 'RUNNING') this.shutdown();
     };
-    Runtime.instance().registerShutdownSignalCallback(shutdownCallback);
+    this.runtime.registerShutdownSignalCallback(shutdownCallback);
 
     let fatalError: Error | undefined;
     const unexpectedErrorSubscription = this.unexpectedErrorSubject.subscribe({
@@ -1784,7 +1779,7 @@ export class Worker {
           { defaultValue: undefined }
         );
       } finally {
-        Runtime.instance().deregisterShutdownSignalCallback(shutdownCallback);
+        this.runtime.deregisterShutdownSignalCallback(shutdownCallback);
 
         await this.nativeWorker.finalizeShutdown();
       }
diff --git a/packages/worker/src/workflow/reusable-vm.ts b/packages/worker/src/workflow/reusable-vm.ts
index 55dd2a07c..5824e0ade 100644
--- a/packages/worker/src/workflow/reusable-vm.ts
+++ b/packages/worker/src/workflow/reusable-vm.ts
@@ -1,8 +1,7 @@
 import vm from 'node:vm';
 import * as internals from '@temporalio/workflow/lib/worker-interface';
 import { IllegalStateError } from '@temporalio/common';
-import { getTimeOfDay } from '@temporalio/core-bridge';
-import { timeOfDayToBigint } from '../logger';
+import { native } from '@temporalio/core-bridge';
 import { Workflow, WorkflowCreateOptions, WorkflowCreator } from './interface';
 import { WorkflowBundleWithSourceMapAndFilename } from './workflow-worker-thread/input';
 import { BaseVMWorkflow, globalHandlers, injectGlobals, setUnhandledRejectionHandler } from './vm-shared';
@@ -181,7 +180,7 @@ export class ReusableVMWorkflowCreator implements WorkflowCreator {
     workflowModule.initRuntime({
       ...options,
       sourceMap: this.workflowBundle.sourceMap,
-      getTimeOfDay: () => timeOfDayToBigint(getTimeOfDay()),
+      getTimeOfDay: native.getTimeOfDay,
       registeredActivityNames: this.registeredActivityNames,
     });
     const activator = context['__TEMPORAL_ACTIVATOR__'];
diff --git a/packages/worker/src/workflow/threaded-vm.ts b/packages/worker/src/workflow/threaded-vm.ts
index 509cb54e4..ac6e73c7c 100644
--- a/packages/worker/src/workflow/threaded-vm.ts
+++ b/packages/worker/src/workflow/threaded-vm.ts
@@ -12,8 +12,8 @@
 import { Worker as NodeWorker } from 'node:worker_threads';
 import { coresdk } from '@temporalio/proto';
 import { IllegalStateError, type SinkCall } from '@temporalio/workflow';
-import { UnexpectedError } from '@temporalio/core-bridge';
 import { Logger } from '@temporalio/common';
+import { UnexpectedError } from '../errors';
 import {
   WorkflowBundleWithSourceMapAndFilename,
   WorkerThreadInput,
diff --git a/packages/worker/src/workflow/vm.ts b/packages/worker/src/workflow/vm.ts
index 8d8f8bdb2..0478a8d0c 100644
--- a/packages/worker/src/workflow/vm.ts
+++ b/packages/worker/src/workflow/vm.ts
@@ -1,7 +1,6 @@
 import vm from 'node:vm';
 import { IllegalStateError } from '@temporalio/common';
-import { getTimeOfDay } from '@temporalio/core-bridge';
-import { timeOfDayToBigint } from '../logger';
+import { native } from '@temporalio/core-bridge';
 import { Workflow, WorkflowCreateOptions, WorkflowCreator } from './interface';
 import { WorkflowBundleWithSourceMapAndFilename } from './workflow-worker-thread/input';
 import {
@@ -59,7 +58,7 @@ export class VMWorkflowCreator implements WorkflowCreator {
     workflowModule.initRuntime({
       ...options,
       sourceMap: this.workflowBundle.sourceMap,
-      getTimeOfDay: () => timeOfDayToBigint(getTimeOfDay()),
+      getTimeOfDay: native.getTimeOfDay,
       registeredActivityNames: this.registeredActivityNames,
     });
     const activator = context.__TEMPORAL_ACTIVATOR__ as any;
diff --git a/packages/workflow/src/internals.ts b/packages/workflow/src/internals.ts
index acc49985b..4bd9e3c63 100644
--- a/packages/workflow/src/internals.ts
+++ b/packages/workflow/src/internals.ts
@@ -410,7 +410,9 @@ export class Activator implements ActivationHandler {
   sinkCalls = Array<SinkCall>();
 
   /**
-   * A nanosecond resolution time function, externally injected
+   * A nanosecond resolution time function, externally injected. This is used to
+   * precisely sort logs entries emitted from the Workflow Context vs those emitted
+   * from other sources (e.g. main thread, Core, etc).
    */
   public readonly getTimeOfDay: () => bigint;