diff --git a/deps/kizunapi b/deps/kizunapi
index c4dbe5c3..f04ca7c5 160000
--- a/deps/kizunapi
+++ b/deps/kizunapi
@@ -1 +1 @@
-Subproject commit c4dbe5c3f1eb0fd850be85e9c5a188238874bbe3
+Subproject commit f04ca7c5b7389b057c88fbc7f9debbe22f5a88ec
diff --git a/src/array.cc b/src/array.cc
index 5a1bc1fe..c523a42f 100644
--- a/src/array.cc
+++ b/src/array.cc
@@ -1,10 +1,19 @@
-#include "mlx/mlx.h"
-#include "src/bindings.h"
-
-namespace mx = mlx::core;
+#include "src/stream.h"
+#include "src/util.h"
 
 namespace ki {
 
+// Allow passing Dtype to js directly, no memory management involved as they are
+// static globals.
+template<>
+struct TypeBridge<mx::Dtype> {
+  static inline mx::Dtype* Wrap(mx::Dtype* ptr) {
+    return ptr;
+  }
+  static inline void Finalize(mx::Dtype* ptr) {
+  }
+};
+
 template<>
 struct Type<mx::Dtype> {
   static constexpr const char* name = "Dtype";
@@ -14,12 +23,12 @@ struct Type<mx::Dtype> {
     DefineProperties(env, prototype,
                      Property("size", Getter(&mx::Dtype::size)));
   }
-  // Since Dtype is represented as a class, we have to store it as a pointer in
-  // js, so converting it to js usually would involve a heap allocation. To
-  // avoid that let's just find the global const.
   static inline napi_status ToNode(napi_env env,
                                    const mx::Dtype& value,
                                    napi_value* result) {
+    // Since Dtype is represented as a class, we have to store it as a pointer
+    // in js, so converting it to js usually would involve a heap allocation. To
+    // avoid that let's just find the global const.
     if (value == mx::bool_)
       return ConvertToNode(env, &mx::bool_, result);
     if (value == mx::uint8)
@@ -48,30 +57,23 @@ struct Type<mx::Dtype> {
       return ConvertToNode(env, &mx::complex64, result);
     return napi_generic_failure;
   }
-  // Dtype is stored as pointer in js, convert it to value in C++ by copy.
   static inline std::optional<mx::Dtype> FromNode(napi_env env,
                                                   napi_value value) {
-    std::optional<mx::Dtype*> ptr = ki::FromNode<mx::Dtype*>(env, value);
-    if (!ptr)
-      return std::nullopt;
-    return *ptr.value();
+    return NodeObjToCppValue<mx::Dtype>(env, value);
   }
 };
 
-// Allow passing Dtype to js directly, no memory management involved as they are
-// static globals.
 template<>
-struct TypeBridge<mx::Dtype> {
-  static inline mx::Dtype* Wrap(mx::Dtype* ptr) {
-    return ptr;
-  }
-  static inline void Finalize(mx::Dtype* ptr) {
+struct TypeBridge<mx::array> {
+  static inline void Finalize(mx::array* ptr) {
+    delete ptr;
   }
 };
 
 template<>
 struct Type<mx::array> {
   static constexpr const char* name = "array";
+
   static mx::array* Constructor(napi_env env,
                                 napi_value value,
                                 std::optional<mx::Dtype> dtype) {
@@ -89,9 +91,7 @@ struct Type<mx::array> {
         return nullptr;
     }
   }
-  static inline void Destructor(mx::array* ptr) {
-    delete ptr;
-  }
+
   static void Define(napi_env env,
                      napi_value constructor,
                      napi_value prototype) {
@@ -108,47 +108,51 @@ struct Type<mx::array> {
                      Property("dtype", Getter(&mx::array::dtype)));
     // Define array's methods.
     Set(env, prototype,
-        "item", MemberFunction(&Item));
+        "item", MemberFunction(&Item),
+        "astype", MemberFunction(&mx::astype));
   }
+
   static napi_value Item(mx::array* a, napi_env env) {
     a->eval();
     switch (a->dtype()) {
       case mx::bool_:
-        return ToNode(env, a->item<bool>());
+        return ki::ToNode(env, a->item<bool>());
       case mx::uint8:
-        return ToNode(env, a->item<uint8_t>());
+        return ki::ToNode(env, a->item<uint8_t>());
       case mx::uint16:
-        return ToNode(env, a->item<uint16_t>());
+        return ki::ToNode(env, a->item<uint16_t>());
       case mx::uint32:
-        return ToNode(env, a->item<uint32_t>());
+        return ki::ToNode(env, a->item<uint32_t>());
       case mx::uint64:
-        return ToNode(env, a->item<uint64_t>());
+        return ki::ToNode(env, a->item<uint64_t>());
       case mx::int8:
-        return ToNode(env, a->item<int8_t>());
+        return ki::ToNode(env, a->item<int8_t>());
       case mx::int16:
-        return ToNode(env, a->item<int16_t>());
+        return ki::ToNode(env, a->item<int16_t>());
       case mx::int32:
-        return ToNode(env, a->item<int32_t>());
+        return ki::ToNode(env, a->item<int32_t>());
       case mx::int64:
-        return ToNode(env, a->item<int64_t>());
+        return ki::ToNode(env, a->item<int64_t>());
       case mx::float16:
-        return ToNode(env, static_cast<float>(a->item<mx::float16_t>()));
+        return ki::ToNode(env, static_cast<float>(a->item<mx::float16_t>()));
       case mx::float32:
-        return ToNode(env, a->item<float>());
+        return ki::ToNode(env, a->item<float>());
       case mx::bfloat16:
-        return ToNode(env, static_cast<float>(a->item<mx::bfloat16_t>()));
+        return ki::ToNode(env, static_cast<float>(a->item<mx::bfloat16_t>()));
       case mx::complex64:
         // FIXME(zcbenz): Represent complex number in JS.
         return Undefined(env);
     }
   }
-  // array is stored as pointer in js, convert it to value in C++ by copy.
+
+  static inline napi_status ToNode(napi_env env,
+                                   mx::array a,
+                                   napi_value* result) {
+    return ManagePointerInJSWrapper(env, new mx::array(std::move(a)), result);
+  }
   static inline std::optional<mx::array> FromNode(napi_env env,
                                                   napi_value value) {
-    std::optional<mx::array*> ptr = ki::FromNode<mx::array*>(env, value);
-    if (!ptr)
-      return std::nullopt;
-    return *ptr.value();
+    return NodeObjToCppValue<mx::array>(env, value);
   }
 };
 
diff --git a/src/bindings.cc b/src/bindings.cc
index 6353c36f..7b1bb41a 100644
--- a/src/bindings.cc
+++ b/src/bindings.cc
@@ -3,6 +3,8 @@
 namespace {
 
 napi_value Init(napi_env env, napi_value exports) {
+  InitDevice(env, exports);
+  InitStream(env, exports);
   InitArray(env, exports);
   return exports;
 }
diff --git a/src/bindings.h b/src/bindings.h
index 15abbcda..bba9c6e6 100644
--- a/src/bindings.h
+++ b/src/bindings.h
@@ -1,8 +1,13 @@
 #ifndef SRC_BINDINGS_H_
 #define SRC_BINDINGS_H_
 
+#include <mlx/mlx.h>
 #include <kizunapi.h>
 
+namespace mx = mlx::core;
+
+void InitDevice(napi_env env, napi_value exports);
+void InitStream(napi_env env, napi_value exports);
 void InitArray(napi_env env, napi_value exports);
 
 #endif  // SRC_BINDINGS_H_
diff --git a/src/device.cc b/src/device.cc
new file mode 100644
index 00000000..3f94a632
--- /dev/null
+++ b/src/device.cc
@@ -0,0 +1,74 @@
+#include "src/device.h"
+#include "src/util.h"
+
+namespace ki {
+
+template<>
+struct TypeBridge<mx::Device> {
+  static inline void Finalize(mx::Device* ptr) {
+    delete ptr;
+  }
+};
+
+// static
+napi_status Type<mx::Device::DeviceType>::ToNode(
+    napi_env env, mx::Device::DeviceType type, napi_value* result) {
+  return ConvertToNode(env, static_cast<int>(type), result);
+}
+
+// static
+std::optional<mx::Device::DeviceType> Type<mx::Device::DeviceType>::FromNode(
+    napi_env env, napi_value value) {
+  std::optional<int> type = ki::FromNode<int>(env, value);
+  if (!type)
+    return std::nullopt;
+  if (*type == static_cast<int>(mx::Device::DeviceType::cpu))
+    return mx::Device::DeviceType::cpu;
+  if (*type == static_cast<int>(mx::Device::DeviceType::gpu))
+    return mx::Device::DeviceType::gpu;
+  return std::nullopt;
+}
+
+// static
+mx::Device* Type<mx::Device>::Constructor(mx::Device::DeviceType type,
+                                          int index) {
+  return new mx::Device(type, index);
+}
+
+// static
+void Type<mx::Device>::Define(napi_env env,
+                              napi_value constructor,
+                              napi_value prototype) {
+  DefineProperties(env, prototype,
+                   Property("type", Getter(&mx::Device::type)));
+}
+
+// static
+napi_status Type<mx::Device>::ToNode(napi_env env,
+                                     mx::Device device,
+                                     napi_value* result) {
+  return ManagePointerInJSWrapper(
+      env, new mx::Device(std::move(device)), result);
+}
+
+// static
+std::optional<mx::Device> Type<mx::Device>::FromNode(napi_env env,
+                                                     napi_value value) {
+  // Try creating a Device when value is a DeviceType.
+  auto type = ki::FromNode<mx::Device::DeviceType>(env, value);
+  if (type)
+    return mx::Device(*type);
+  // Otherwise try converting from Device.
+  return NodeObjToCppValue<mx::Device>(env, value);
+}
+
+}  // namespace ki
+
+void InitDevice(napi_env env, napi_value exports) {
+  ki::Set(env, exports,
+          "cpu", mx::Device::DeviceType::cpu,
+          "gpu", mx::Device::DeviceType::gpu,
+          "Device", ki::Class<mx::Device>(),
+          "defaultDevice", mx::default_device,
+          "setDefaultDevice", mx::set_default_device);
+}
diff --git a/src/device.h b/src/device.h
new file mode 100644
index 00000000..19081bb0
--- /dev/null
+++ b/src/device.h
@@ -0,0 +1,36 @@
+#ifndef SRC_DEVICE_H_
+#define SRC_DEVICE_H_
+
+#include "src/bindings.h"
+
+namespace ki {
+
+template<>
+struct Type<mx::Device::DeviceType> {
+  static constexpr const char* name = "DeviceType";
+  static napi_status ToNode(napi_env env,
+                            mx::Device::DeviceType type,
+                            napi_value* result);
+  static std::optional<mx::Device::DeviceType> FromNode(napi_env env,
+                                                        napi_value value);
+};
+
+template<>
+struct Type<mx::Device> {
+  static constexpr const char* name = "Device";
+
+  static mx::Device* Constructor(mx::Device::DeviceType type, int index);
+  static void Define(napi_env env,
+                     napi_value constructor,
+                     napi_value prototype);
+
+  static napi_status ToNode(napi_env env,
+                            mx::Device device,
+                            napi_value* result);
+  static std::optional<mx::Device> FromNode(napi_env env,
+                                            napi_value value);
+};
+
+}  // namespace ki
+
+#endif  // SRC_DEVICE_H_
diff --git a/src/stream.cc b/src/stream.cc
new file mode 100644
index 00000000..e98ecfc7
--- /dev/null
+++ b/src/stream.cc
@@ -0,0 +1,61 @@
+#include "src/stream.h"
+#include "src/util.h"
+
+namespace ki {
+
+template<>
+struct TypeBridge<mx::Stream> {
+  static inline void Finalize(mx::Stream* ptr) {
+    delete ptr;
+  }
+};
+
+// static
+mx::Stream* Type<mx::Stream>::Constructor(int index, const mx::Device& device) {
+  return new mx::Stream(index, device);
+}
+
+// static
+void Type<mx::Stream>::Define(napi_env env,
+                              napi_value constructor,
+                              napi_value prototype) {
+  DefineProperties(env, prototype,
+                   Property("device", Getter(&mx::Stream::device)));
+}
+
+// static
+napi_status Type<mx::Stream>::ToNode(napi_env env,
+                                     mx::Stream stream,
+                                     napi_value* result) {
+  return ManagePointerInJSWrapper(
+      env, new mx::Stream(std::move(stream)), result);
+}
+
+// static
+std::optional<mx::Stream> Type<mx::Stream>::FromNode(napi_env env,
+                                                     napi_value value) {
+  return NodeObjToCppValue<mx::Stream>(env, value);
+}
+
+// static
+std::optional<mx::StreamOrDevice> Type<mx::StreamOrDevice>::FromNode(
+    napi_env env,
+    napi_value value) {
+  std::optional<mx::Stream> stream = Type<mx::Stream>::FromNode(env, value);
+  if (stream)
+    return *stream;
+  std::optional<mx::Device> device = Type<mx::Device>::FromNode(env, value);
+  if (device)
+    return *device;
+  return std::nullopt;
+}
+
+}  // namespace ki
+
+void InitStream(napi_env env, napi_value exports) {
+  ki::Set(env, exports,
+          "Stream", ki::Class<mx::Stream>(),
+          "defaultStream", mx::default_stream,
+          "setDefaultStream", mx::set_default_stream,
+          "newStream", mx::new_stream);
+}
diff --git a/src/stream.h b/src/stream.h
new file mode 100644
index 00000000..353bf09f
--- /dev/null
+++ b/src/stream.h
@@ -0,0 +1,33 @@
+#ifndef SRC_STREAM_H_
+#define SRC_STREAM_H_
+
+#include "src/device.h"
+
+namespace ki {
+
+template<>
+struct Type<mx::Stream> {
+  static constexpr const char* name = "Stream";
+
+  static mx::Stream* Constructor(int index, const mx::Device& device);
+  static void Define(napi_env env,
+                     napi_value constructor,
+                     napi_value prototype);
+
+  static napi_status ToNode(napi_env env,
+                            mx::Stream stream,
+                            napi_value* result);
+  static std::optional<mx::Stream> FromNode(napi_env env,
+                                            napi_value value);
+};
+
+template<>
+struct Type<mx::StreamOrDevice> {
+  static constexpr const char* name = "StreamOrDevice";
+  static std::optional<mx::StreamOrDevice> FromNode(napi_env env,
+                                                    napi_value value);
+};
+
+}  // namespace ki
+
+#endif  // SRC_STREAM_H_
diff --git a/src/util.h b/src/util.h
new file mode 100644
index 00000000..fc90a9c6
--- /dev/null
+++ b/src/util.h
@@ -0,0 +1,16 @@
+#ifndef SRC_UTIL_H_
+#define SRC_UTIL_H_
+
+#include <kizunapi.h>
+
+// In js land the objects are always stored as pointers, when a value is needed
+// from C++ land, we do a copy.
+template<typename T>
+inline std::optional<T> NodeObjToCppValue(napi_env env, napi_value value) {
+  std::optional<T*> ptr = ki::FromNode<T*>(env, value);
+  if (!ptr)
+    return std::nullopt;
+  return *ptr.value();
+}
+
+#endif  // SRC_UTIL_H_