diff --git a/primer-service/src/Primer/OpenAPI.hs b/primer-service/src/Primer/OpenAPI.hs
index 1e0b13119..0ce92959b 100644
--- a/primer-service/src/Primer/OpenAPI.hs
+++ b/primer-service/src/Primer/OpenAPI.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE StandaloneDeriving #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 
 module Primer.OpenAPI (
@@ -6,8 +7,12 @@ module Primer.OpenAPI (
 ) where
 
 import Data.OpenApi (ToSchema)
+import Data.Text (Text)
+import Primer.API (Def, Prog, Tree)
 import Primer.App (InitialApp)
+import Primer.Core (ID (..))
 import Primer.Database (Session, SessionName)
+import Primer.Name (Name)
 
 -- $orphanInstances
 --
@@ -19,3 +24,14 @@ import Primer.Database (Session, SessionName)
 instance ToSchema SessionName
 instance ToSchema Session
 instance ToSchema InitialApp
+
+-- We need to GND the ID instance to match its To/FromJSON instances
+deriving newtype instance ToSchema ID
+
+-- We can't GND derive for Name as it is an opaque type
+-- But the JSON instance is done by GND, so we must match here...
+-- This instance works because the parameter has a phantom role!
+deriving via Text instance (ToSchema Name)
+instance ToSchema Tree
+instance ToSchema Def
+instance ToSchema Prog
diff --git a/primer-service/src/Primer/Server.hs b/primer-service/src/Primer/Server.hs
index 019159f56..86ab21546 100644
--- a/primer-service/src/Primer/Server.hs
+++ b/primer-service/src/Primer/Server.hs
@@ -47,6 +47,7 @@ import Primer.API (
   renameSession,
   variablesInScope,
  )
+import qualified Primer.API as API
 import Primer.Action (
   Action (Move),
   ActionError (TypeError),
@@ -162,7 +163,11 @@ type PrimerOpenAPI =
   :<|> QueryFlag "inMemory" :> "sessions" :>
     PaginationParams :>
     Summary "List sessions" :>
-    OpId "getSessionList" Get '[JSON] (Paginated Session))
+    OpId "getSessionList" Get '[JSON] (Paginated Session)
+
+    -- The rest of the API is scoped to a particular session
+  :<|> QueryParam' '[Required, Strict] "session" SessionId :> SOpenAPI
+  )
 
 type PrimerLegacyAPI =
   "api" :> (
@@ -193,15 +198,19 @@ type PrimerLegacyAPI =
   :<|> Raw
 
 -- | The session-specific bits of the api
-type SAPI = (
-
+type SOpenAPI = (
     -- GET /api/program
     --   Get the current program state
-    "program" :> Get '[JSON] (Result ProgError Prog)
+    "program" :> Get '[JSON] API.Prog
+  )
+
 
+-- | The session-specific bits of the api
+-- (legacy version)
+type SAPI = (
     -- GET /api/session-name
     --   Get the current session name.
-  :<|> "session-name" :> Get '[JSON] Text
+       "session-name" :> Get '[JSON] Text
 
     -- PUT /api/session-name
     --   Attempt to set the current session name. Returns the new
@@ -370,13 +379,13 @@ primerServer = openAPIServer :<|> legacyServer
   where
     openAPIServer =
       newSession
-        :<|> \b p -> pagedDefaultClamp 100 p $ listSessions b
+        :<|> (\b p -> pagedDefaultClamp 100 p $ listSessions b)
+        :<|> getProgram
     legacyServer =
       ( copySession
           :<|> getVersion
           :<|> ( \sid ->
-                  getProgram sid
-                    :<|> getSessionName sid
+                  getSessionName sid
                     :<|> renameSession sid
                     :<|> edit sid
                     :<|> (variablesInScope sid :<|> generateNames sid)
diff --git a/primer/primer.cabal b/primer/primer.cabal
index bb6111696..9474db303 100644
--- a/primer/primer.cabal
+++ b/primer/primer.cabal
@@ -96,6 +96,7 @@ test-suite primer-test
     Tests.Action.Capture
     Tests.Action.Prog
     Tests.AlphaEquality
+    Tests.API
     Tests.Database
     Tests.Eval
     Tests.EvalFull
diff --git a/primer/src/Primer/API.hs b/primer/src/Primer/API.hs
index c92618ed9..50d723100 100644
--- a/primer/src/Primer/API.hs
+++ b/primer/src/Primer/API.hs
@@ -19,6 +19,9 @@ module Primer.API (
   copySession,
   listSessions,
   getVersion,
+  Tree,
+  Prog,
+  Def,
   getProgram,
   getSessionName,
   renameSession,
@@ -28,6 +31,9 @@ module Primer.API (
   evalStep,
   evalFull,
   flushSessions,
+  -- viewTree*: only exported for testing
+  viewTreeType,
+  viewTreeExpr,
 ) where
 
 import Foreword
@@ -41,6 +47,10 @@ import Control.Concurrent.STM (
   writeTBQueue,
  )
 import Control.Monad.Catch (MonadThrow, throwM)
+import Data.Aeson (ToJSON)
+import Data.Data (showConstr, toConstr)
+import qualified Data.Generics.Uniplate.Data as U
+import qualified Data.Map as Map
 import qualified ListT (toList)
 import Primer.App (
   App,
@@ -51,7 +61,6 @@ import Primer.App (
   EvalResp (..),
   InitialApp,
   MutationRequest,
-  Prog,
   ProgError,
   QueryAppM,
   Question (..),
@@ -62,13 +71,25 @@ import Primer.App (
   handleMutationRequest,
   handleQuestion,
   initialApp,
+  progDefs,
+  progTypes,
   runEditAppM,
   runQueryAppM,
  )
+import qualified Primer.App as App
 import Primer.Core (
+  Expr,
+  Expr' (APP, Ann, GlobalVar, LetType, Letrec),
   ID,
   Kind,
-  Type',
+  Type,
+  Type' (TForall),
+  defExpr,
+  defID,
+  defName,
+  defType,
+  getID,
+  typeDefName,
  )
 import Primer.Database (
   OffsetLimit,
@@ -97,7 +118,7 @@ import qualified Primer.Database as Database (
     Success
   ),
  )
-import Primer.Name (Name)
+import Primer.Name (Name, unName)
 import qualified StmContainers.Map as StmMap
 
 data Env = Env
@@ -256,10 +277,97 @@ liftEditAppM h sid = withSession' sid (EditApp $ runEditAppM h)
 liftQueryAppM :: (MonadIO m, MonadThrow m) => QueryAppM a -> SessionId -> PrimerM m (Result ProgError a)
 liftQueryAppM h sid = withSession' sid (QueryApp $ runQueryAppM h)
 
-getProgram :: (MonadIO m, MonadThrow m) => SessionId -> PrimerM m (Result ProgError Prog)
-getProgram = liftQueryAppM handleGetProgramRequest
+getProgram :: (MonadIO m, MonadThrow m) => SessionId -> PrimerM m Prog
+getProgram sid = withSession' sid $ QueryApp $ viewProg . handleGetProgramRequest
+
+-- | A frontend will be mostly concerned with rendering, and does not need the
+-- full complexity of our AST for that task. 'Tree' is a simplified view with
+-- just enough information to render nicely.
+-- (NB: currently this is just a first draft, and is expected to evolve.)
+data Tree = Tree
+  { nodeId :: ID
+  , label :: Text
+  , childTrees :: [Tree]
+  }
+  deriving (Show, Eq, Generic)
+
+instance ToJSON Tree
+
+-- | This type is the API's view of a 'App.Prog'
+-- (this is expected to evolve as we flesh out the API)
+data Prog = Prog
+  { types :: [Name]
+  , -- We don't use Map ID Def, as the JSON encoding would be as an object,
+    -- where keys are IDs converted to strings and we have no nice way of
+    -- saying "all the keys of this object should parse as numbers". Similarly,
+    -- it is rather redundant as each Def carries a defID field (which is
+    -- encoded as a number), and it is difficult to enforce that "the keys of
+    -- this object match the defID field of the corresponding value".
+    defs :: [Def]
+  }
+  deriving (Generic)
+
+instance ToJSON Prog
+
+-- | This type is the api's view of a 'Primer.Core.Def'
+-- (this is expected to evolve as we flesh out the API)
+data Def = Def
+  { id :: ID
+  , name :: Name
+  , type_ :: Tree
+  , term :: Tree
+  }
+  deriving (Generic)
+
+instance ToJSON Def
+
+viewProg :: App.Prog -> Prog
+viewProg p =
+  Prog
+    { types = typeDefName <$> progTypes p
+    , defs =
+        ( \d ->
+            Def
+              { id = defID d
+              , name = defName d
+              , type_ = viewTreeType $ defType d
+              , term = viewTreeExpr $ defExpr d
+              }
+        )
+          <$> Map.elems (progDefs p)
+    }
+
+-- | A simple method to extract 'Tree's from 'Expr's. This is injective.
+-- Currently it is designed to be simple and just enough to enable
+-- experimenting with rendering on the frontend.
+--
+-- It is expected to evolve in the future.
+viewTreeExpr :: Expr -> Tree
+viewTreeExpr = U.para $ \e exprChildren ->
+  let c = toS $ showConstr $ toConstr e
+      n = case e of
+        GlobalVar _ i -> c <> " " <> show i
+        _ -> unwords $ c : map unName (U.childrenBi e)
+      -- add info about type children
+      allChildren = case e of
+        Ann _ _ ty -> exprChildren ++ [viewTreeType ty]
+        APP _ _ ty -> exprChildren ++ [viewTreeType ty]
+        LetType _ _ ty _ -> viewTreeType ty : exprChildren
+        Letrec _ _ _ ty _ -> let (h, t) = splitAt 1 exprChildren in h ++ viewTreeType ty : t
+        -- otherwise, no type children
+        _ -> exprChildren
+   in Tree (getID e) n allChildren
+
+-- | Similar to 'viewTreeExpr', but for 'Type's
+viewTreeType :: Type -> Tree
+viewTreeType = U.para $ \e allChildren ->
+  let c = toS $ showConstr $ toConstr e
+      n = case e of
+        TForall _ m k _ -> c <> " " <> unName m <> ":" <> show k
+        _ -> unwords $ c : map unName (U.childrenBi e)
+   in Tree (getID e) n allChildren
 
-edit :: (MonadIO m, MonadThrow m) => SessionId -> MutationRequest -> PrimerM m (Result ProgError Prog)
+edit :: (MonadIO m, MonadThrow m) => SessionId -> MutationRequest -> PrimerM m (Result ProgError App.Prog)
 edit sid req = liftEditAppM (handleMutationRequest req) sid
 
 variablesInScope :: (MonadIO m, MonadThrow m) => SessionId -> (ID, ID) -> PrimerM m (Result ProgError (([(Name, Kind)], [(Name, Type' ())]), [(ID, Name, Type' ())]))
diff --git a/primer/src/Primer/App.hs b/primer/src/Primer/App.hs
index 8055f8729..15afd124a 100644
--- a/primer/src/Primer/App.hs
+++ b/primer/src/Primer/App.hs
@@ -292,7 +292,7 @@ focusNode prog defid nodeid =
             Just x -> pure x
 
 -- | Handle a request to retrieve the current program
-handleGetProgramRequest :: MonadQueryApp m => m Prog
+handleGetProgramRequest :: MonadReader App m => m Prog
 handleGetProgramRequest = asks appProg
 
 -- | Handle a request to mutate the app state
diff --git a/primer/src/Primer/Core.hs b/primer/src/Primer/Core.hs
index 644a208ab..5fc695056 100644
--- a/primer/src/Primer/Core.hs
+++ b/primer/src/Primer/Core.hs
@@ -64,11 +64,8 @@ newtype ID = ID {unID :: Int}
   -- The Ord and Enum instances are useful for tests but we may remove them in
   -- future, so don't use them in app code.
   deriving newtype (Show, Num, Ord, Enum)
-  deriving (FromJSON, ToJSON) via VJSON ID
-
-instance ToJSONKey ID
-
-instance FromJSONKey ID
+  deriving newtype (FromJSON, ToJSON)
+  deriving newtype (ToJSONKey, FromJSONKey)
 
 data Meta a = Meta ID a (Maybe Value)
   deriving (Generic, Eq, Show, Data, Functor)
diff --git a/primer/src/Primer/Name.hs b/primer/src/Primer/Name.hs
index 1c2ec2804..654a73af5 100644
--- a/primer/src/Primer/Name.hs
+++ b/primer/src/Primer/Name.hs
@@ -23,7 +23,7 @@ import Primer.JSON
 newtype Name = Name {unName :: Text}
   deriving (Eq, Ord, Generic, Data)
   deriving newtype (Show, IsString)
-  deriving (FromJSON, ToJSON) via VJSON Name
+  deriving newtype (FromJSON, ToJSON)
 
 -- | Construct a name from a Text. This is called unsafe because there are no
 -- guarantees about whether the name refers to anything that is in scope.
diff --git a/primer/test/Tests/API.hs b/primer/test/Tests/API.hs
new file mode 100644
index 000000000..a98d76183
--- /dev/null
+++ b/primer/test/Tests/API.hs
@@ -0,0 +1,95 @@
+module Tests.API where
+
+import Foreword
+
+import Gen.Core.Raw (evalExprGen, genExpr, genType)
+import Hedgehog
+import Primer.API (viewTreeExpr, viewTreeType)
+import Primer.Core.DSL
+import Test.Tasty.HUnit
+
+import Primer.Core
+
+hprop_viewTreeExpr_injective :: Property
+hprop_viewTreeExpr_injective = property $ do
+  e1 <- forAll $ evalExprGen 0 genExpr
+  e2 <- forAll $ evalExprGen 0 genExpr
+  when (e1 == e2) discard
+  viewTreeExpr e1 /== viewTreeExpr e2
+
+hprop_viewTreeType_injective :: Property
+hprop_viewTreeType_injective = property $ do
+  t1 <- forAll $ evalExprGen 0 genType
+  t2 <- forAll $ evalExprGen 0 genType
+  when (t1 == t2) discard
+  viewTreeType t1 /== viewTreeType t2
+
+-- regression tests to check we encode names into the tree
+
+unit_viewTreeExpr_injective_con :: Assertion
+unit_viewTreeExpr_injective_con =
+  distinctTreeExpr (con "C") (con "D")
+
+unit_viewTreeExpr_injective_lam :: Assertion
+unit_viewTreeExpr_injective_lam =
+  distinctTreeExpr (lam "x" emptyHole) (lam "y" emptyHole)
+
+unit_viewTreeExpr_injective_LAM :: Assertion
+unit_viewTreeExpr_injective_LAM =
+  distinctTreeExpr (lAM "x" emptyHole) (lAM "y" emptyHole)
+
+unit_viewTreeExpr_injective_var :: Assertion
+unit_viewTreeExpr_injective_var =
+  distinctTreeExpr (var "x") (var "y")
+
+unit_viewTreeExpr_injective_globalvar :: Assertion
+unit_viewTreeExpr_injective_globalvar =
+  distinctTreeExpr (global 0) (global 1)
+
+unit_viewTreeExpr_injective_let :: Assertion
+unit_viewTreeExpr_injective_let =
+  distinctTreeExpr (let_ "x" emptyHole emptyHole) (let_ "y" emptyHole emptyHole)
+
+unit_viewTreeExpr_injective_lettype :: Assertion
+unit_viewTreeExpr_injective_lettype =
+  distinctTreeExpr (letType "x" tEmptyHole emptyHole) (letType "y" tEmptyHole emptyHole)
+
+unit_viewTreeExpr_injective_letrec :: Assertion
+unit_viewTreeExpr_injective_letrec =
+  distinctTreeExpr (letrec "x" emptyHole tEmptyHole emptyHole) (letrec "y" emptyHole tEmptyHole emptyHole)
+
+unit_viewTreeExpr_injective_case_conName :: Assertion
+unit_viewTreeExpr_injective_case_conName =
+  distinctTreeExpr (case_ emptyHole [branch "C" [("x", Nothing)] emptyHole]) (case_ emptyHole [branch "D" [("x", Nothing)] emptyHole])
+
+unit_viewTreeExpr_injective_case_paramName :: Assertion
+unit_viewTreeExpr_injective_case_paramName =
+  distinctTreeExpr (case_ emptyHole [branch "C" [("x", Nothing)] emptyHole]) (case_ emptyHole [branch "C" [("y", Nothing)] emptyHole])
+
+unit_viewTreeType_injective_con :: Assertion
+unit_viewTreeType_injective_con =
+  distinctTreeType (tcon "T") (tcon "S")
+
+unit_viewTreeType_injective_var :: Assertion
+unit_viewTreeType_injective_var =
+  distinctTreeType (tvar "a") (tvar "b")
+
+unit_viewTreeType_injective_forall_param :: Assertion
+unit_viewTreeType_injective_forall_param =
+  distinctTreeType (tforall "a" KType tEmptyHole) (tforall "b" KType tEmptyHole)
+
+unit_viewTreeType_injective_forall_kind :: Assertion
+unit_viewTreeType_injective_forall_kind =
+  distinctTreeType (tforall "a" KType tEmptyHole) (tforall "a" KHole tEmptyHole)
+
+distinctTreeExpr :: S Expr -> S Expr -> Assertion
+distinctTreeExpr e1 e2 =
+  let t1 = viewTreeExpr $ fst $ create e1
+      t2 = viewTreeExpr $ fst $ create e2
+   in assertBool ("non-injective viewTreeExpr: " ++ show t1) (t1 /= t2)
+
+distinctTreeType :: S Type -> S Type -> Assertion
+distinctTreeType e1 e2 =
+  let t1 = viewTreeType $ fst $ create e1
+      t2 = viewTreeType $ fst $ create e2
+   in assertBool ("non-injective viewTreeType: " ++ show t1) (t1 /= t2)
diff --git a/primer/test/outputs/serialization/action.json b/primer/test/outputs/serialization/action.json
index 0b8adf0e5..834c280fd 100644
--- a/primer/test/outputs/serialization/action.json
+++ b/primer/test/outputs/serialization/action.json
@@ -1,6 +1,4 @@
 {
-    "contents": {
-        "unID": 0
-    },
+    "contents": 0,
     "tag": "SetCursor"
 }
\ No newline at end of file
diff --git a/primer/test/outputs/serialization/actionerror.json b/primer/test/outputs/serialization/actionerror.json
index 610d019f0..26e8a96a3 100644
--- a/primer/test/outputs/serialization/actionerror.json
+++ b/primer/test/outputs/serialization/actionerror.json
@@ -1,6 +1,4 @@
 {
-    "contents": {
-        "unID": 0
-    },
+    "contents": 0,
     "tag": "IDNotFound"
 }
\ No newline at end of file
diff --git a/primer/test/outputs/serialization/def.json b/primer/test/outputs/serialization/def.json
index 26497389a..19c3eb0e4 100644
--- a/primer/test/outputs/serialization/def.json
+++ b/primer/test/outputs/serialization/def.json
@@ -1,9 +1,7 @@
 {
     "defExpr": {
         "contents": [
-            {
-                "unID": 0
-            },
+            0,
             {
                 "contents": {
                     "contents": [],
@@ -15,17 +13,11 @@
         ],
         "tag": "EmptyHole"
     },
-    "defID": {
-        "unID": 1
-    },
-    "defName": {
-        "unName": "main"
-    },
+    "defID": 1,
+    "defName": "main",
     "defType": {
         "contents": [
-            {
-                "unID": 0
-            },
+            0,
             {
                 "tag": "KType"
             },
diff --git a/primer/test/outputs/serialization/edit_response_1.json b/primer/test/outputs/serialization/edit_response_1.json
index 8d5bee8ca..fc4a18aa6 100644
--- a/primer/test/outputs/serialization/edit_response_1.json
+++ b/primer/test/outputs/serialization/edit_response_1.json
@@ -1,8 +1,6 @@
 {
     "contents": {
-        "contents": {
-            "unID": 0
-        },
+        "contents": 0,
         "tag": "IDNotFound"
     },
     "tag": "Error"
diff --git a/primer/test/outputs/serialization/edit_response_2.json b/primer/test/outputs/serialization/edit_response_2.json
index 7b6fbdea0..88076147a 100644
--- a/primer/test/outputs/serialization/edit_response_2.json
+++ b/primer/test/outputs/serialization/edit_response_2.json
@@ -1,48 +1,35 @@
 {
     "contents": {
-        "progDefs": [
-            [
-                {
-                    "unID": 1
-                },
-                {
-                    "defExpr": {
-                        "contents": [
-                            {
-                                "unID": 0
-                            },
-                            {
-                                "contents": {
-                                    "contents": [],
-                                    "tag": "TEmptyHole"
-                                },
-                                "tag": "TCSynthed"
-                            },
-                            null
-                        ],
-                        "tag": "EmptyHole"
-                    },
-                    "defID": {
-                        "unID": 1
-                    },
-                    "defName": {
-                        "unName": "main"
-                    },
-                    "defType": {
-                        "contents": [
-                            {
-                                "unID": 0
-                            },
-                            {
-                                "tag": "KType"
+        "progDefs": {
+            "1": {
+                "defExpr": {
+                    "contents": [
+                        0,
+                        {
+                            "contents": {
+                                "contents": [],
+                                "tag": "TEmptyHole"
                             },
-                            null
-                        ],
-                        "tag": "TEmptyHole"
-                    }
+                            "tag": "TCSynthed"
+                        },
+                        null
+                    ],
+                    "tag": "EmptyHole"
+                },
+                "defID": 1,
+                "defName": "main",
+                "defType": {
+                    "contents": [
+                        0,
+                        {
+                            "tag": "KType"
+                        },
+                        null
+                    ],
+                    "tag": "TEmptyHole"
                 }
-            ]
-        ],
+            }
+        },
         "progLog": {
             "unlog": [
                 [
@@ -64,9 +51,7 @@
             "selectedDef": {
                 "defExpr": {
                     "contents": [
-                        {
-                            "unID": 0
-                        },
+                        0,
                         {
                             "contents": {
                                 "contents": [],
@@ -78,17 +63,11 @@
                     ],
                     "tag": "EmptyHole"
                 },
-                "defID": {
-                    "unID": 1
-                },
-                "defName": {
-                    "unName": "main"
-                },
+                "defID": 1,
+                "defName": "main",
                 "defType": {
                     "contents": [
-                        {
-                            "unID": 0
-                        },
+                        0,
                         {
                             "tag": "KType"
                         },
@@ -100,9 +79,7 @@
             "selectedNode": {
                 "meta": {
                     "Left": [
-                        {
-                            "unID": 0
-                        },
+                        0,
                         {
                             "contents": {
                                 "contents": [],
@@ -113,9 +90,7 @@
                         null
                     ]
                 },
-                "nodeId": {
-                    "unID": 0
-                },
+                "nodeId": 0,
                 "nodeType": {
                     "tag": "BodyNode"
                 }
@@ -135,18 +110,14 @@
                                     {
                                         "contents": [
                                             [],
-                                            {
-                                                "unName": "b"
-                                            }
+                                            "b"
                                         ],
                                         "tag": "TCon"
                                     },
                                     {
                                         "contents": [
                                             [],
-                                            {
-                                                "unName": "a"
-                                            }
+                                            "a"
                                         ],
                                         "tag": "TCon"
                                     }
@@ -156,35 +127,25 @@
                             {
                                 "contents": [
                                     [],
-                                    {
-                                        "unName": "Nat"
-                                    }
+                                    "Nat"
                                 ],
                                 "tag": "TCon"
                             }
                         ],
-                        "valConName": {
-                            "unName": "C"
-                        }
+                        "valConName": "C"
                     }
                 ],
-                "typeDefName": {
-                    "unName": "T"
-                },
+                "typeDefName": "T",
                 "typeDefNameHints": [],
                 "typeDefParameters": [
                     [
-                        {
-                            "unName": "a"
-                        },
+                        "a",
                         {
                             "tag": "KType"
                         }
                     ],
                     [
-                        {
-                            "unName": "b"
-                        },
+                        "b",
                         {
                             "contents": [
                                 {
diff --git a/primer/test/outputs/serialization/expr.json b/primer/test/outputs/serialization/expr.json
index 19374dacb..69fa63969 100644
--- a/primer/test/outputs/serialization/expr.json
+++ b/primer/test/outputs/serialization/expr.json
@@ -1,8 +1,6 @@
 {
     "contents": [
-        {
-            "unID": 0
-        },
+        0,
         {
             "contents": {
                 "contents": [],
diff --git a/primer/test/outputs/serialization/id.json b/primer/test/outputs/serialization/id.json
index 8e5d1b35f..c22708346 100644
--- a/primer/test/outputs/serialization/id.json
+++ b/primer/test/outputs/serialization/id.json
@@ -1,3 +1 @@
-{
-    "unID": 0
-}
\ No newline at end of file
+0
\ No newline at end of file
diff --git a/primer/test/outputs/serialization/name.json b/primer/test/outputs/serialization/name.json
index a6d6abbbd..3403a0c7f 100644
--- a/primer/test/outputs/serialization/name.json
+++ b/primer/test/outputs/serialization/name.json
@@ -1,3 +1 @@
-{
-    "unName": "x"
-}
\ No newline at end of file
+"x"
\ No newline at end of file
diff --git a/primer/test/outputs/serialization/prog.json b/primer/test/outputs/serialization/prog.json
index 8a0d08f57..3d8d32b9a 100644
--- a/primer/test/outputs/serialization/prog.json
+++ b/primer/test/outputs/serialization/prog.json
@@ -1,47 +1,34 @@
 {
-    "progDefs": [
-        [
-            {
-                "unID": 1
-            },
-            {
-                "defExpr": {
-                    "contents": [
-                        {
-                            "unID": 0
-                        },
-                        {
-                            "contents": {
-                                "contents": [],
-                                "tag": "TEmptyHole"
-                            },
-                            "tag": "TCSynthed"
-                        },
-                        null
-                    ],
-                    "tag": "EmptyHole"
-                },
-                "defID": {
-                    "unID": 1
-                },
-                "defName": {
-                    "unName": "main"
-                },
-                "defType": {
-                    "contents": [
-                        {
-                            "unID": 0
-                        },
-                        {
-                            "tag": "KType"
+    "progDefs": {
+        "1": {
+            "defExpr": {
+                "contents": [
+                    0,
+                    {
+                        "contents": {
+                            "contents": [],
+                            "tag": "TEmptyHole"
                         },
-                        null
-                    ],
-                    "tag": "TEmptyHole"
-                }
+                        "tag": "TCSynthed"
+                    },
+                    null
+                ],
+                "tag": "EmptyHole"
+            },
+            "defID": 1,
+            "defName": "main",
+            "defType": {
+                "contents": [
+                    0,
+                    {
+                        "tag": "KType"
+                    },
+                    null
+                ],
+                "tag": "TEmptyHole"
             }
-        ]
-    ],
+        }
+    },
     "progLog": {
         "unlog": [
             [
@@ -63,9 +50,7 @@
         "selectedDef": {
             "defExpr": {
                 "contents": [
-                    {
-                        "unID": 0
-                    },
+                    0,
                     {
                         "contents": {
                             "contents": [],
@@ -77,17 +62,11 @@
                 ],
                 "tag": "EmptyHole"
             },
-            "defID": {
-                "unID": 1
-            },
-            "defName": {
-                "unName": "main"
-            },
+            "defID": 1,
+            "defName": "main",
             "defType": {
                 "contents": [
-                    {
-                        "unID": 0
-                    },
+                    0,
                     {
                         "tag": "KType"
                     },
@@ -99,9 +78,7 @@
         "selectedNode": {
             "meta": {
                 "Left": [
-                    {
-                        "unID": 0
-                    },
+                    0,
                     {
                         "contents": {
                             "contents": [],
@@ -112,9 +89,7 @@
                     null
                 ]
             },
-            "nodeId": {
-                "unID": 0
-            },
+            "nodeId": 0,
             "nodeType": {
                 "tag": "BodyNode"
             }
@@ -134,18 +109,14 @@
                                 {
                                     "contents": [
                                         [],
-                                        {
-                                            "unName": "b"
-                                        }
+                                        "b"
                                     ],
                                     "tag": "TCon"
                                 },
                                 {
                                     "contents": [
                                         [],
-                                        {
-                                            "unName": "a"
-                                        }
+                                        "a"
                                     ],
                                     "tag": "TCon"
                                 }
@@ -155,35 +126,25 @@
                         {
                             "contents": [
                                 [],
-                                {
-                                    "unName": "Nat"
-                                }
+                                "Nat"
                             ],
                             "tag": "TCon"
                         }
                     ],
-                    "valConName": {
-                        "unName": "C"
-                    }
+                    "valConName": "C"
                 }
             ],
-            "typeDefName": {
-                "unName": "T"
-            },
+            "typeDefName": "T",
             "typeDefNameHints": [],
             "typeDefParameters": [
                 [
-                    {
-                        "unName": "a"
-                    },
+                    "a",
                     {
                         "tag": "KType"
                     }
                 ],
                 [
-                    {
-                        "unName": "b"
-                    },
+                    "b",
                     {
                         "contents": [
                             {
diff --git a/primer/test/outputs/serialization/progaction.json b/primer/test/outputs/serialization/progaction.json
index 2e0e4dec5..6303f85fb 100644
--- a/primer/test/outputs/serialization/progaction.json
+++ b/primer/test/outputs/serialization/progaction.json
@@ -1,6 +1,4 @@
 {
-    "contents": {
-        "unID": 0
-    },
+    "contents": 0,
     "tag": "MoveToDef"
 }
\ No newline at end of file
diff --git a/primer/test/outputs/serialization/selection.json b/primer/test/outputs/serialization/selection.json
index 92480f322..798af6aef 100644
--- a/primer/test/outputs/serialization/selection.json
+++ b/primer/test/outputs/serialization/selection.json
@@ -2,9 +2,7 @@
     "selectedDef": {
         "defExpr": {
             "contents": [
-                {
-                    "unID": 0
-                },
+                0,
                 {
                     "contents": {
                         "contents": [],
@@ -16,17 +14,11 @@
             ],
             "tag": "EmptyHole"
         },
-        "defID": {
-            "unID": 1
-        },
-        "defName": {
-            "unName": "main"
-        },
+        "defID": 1,
+        "defName": "main",
         "defType": {
             "contents": [
-                {
-                    "unID": 0
-                },
+                0,
                 {
                     "tag": "KType"
                 },
@@ -38,9 +30,7 @@
     "selectedNode": {
         "meta": {
             "Left": [
-                {
-                    "unID": 0
-                },
+                0,
                 {
                     "contents": {
                         "contents": [],
@@ -51,9 +41,7 @@
                 null
             ]
         },
-        "nodeId": {
-            "unID": 0
-        },
+        "nodeId": 0,
         "nodeType": {
             "tag": "BodyNode"
         }
diff --git a/primer/test/outputs/serialization/type.json b/primer/test/outputs/serialization/type.json
index de8c0b92f..2596b3c9c 100644
--- a/primer/test/outputs/serialization/type.json
+++ b/primer/test/outputs/serialization/type.json
@@ -1,8 +1,6 @@
 {
     "contents": [
-        {
-            "unID": 0
-        },
+        0,
         {
             "tag": "KType"
         },
diff --git a/primer/test/outputs/serialization/typeDef.json b/primer/test/outputs/serialization/typeDef.json
index fbe1f3764..6b0fbd173 100644
--- a/primer/test/outputs/serialization/typeDef.json
+++ b/primer/test/outputs/serialization/typeDef.json
@@ -8,18 +8,14 @@
                         {
                             "contents": [
                                 [],
-                                {
-                                    "unName": "b"
-                                }
+                                "b"
                             ],
                             "tag": "TCon"
                         },
                         {
                             "contents": [
                                 [],
-                                {
-                                    "unName": "a"
-                                }
+                                "a"
                             ],
                             "tag": "TCon"
                         }
@@ -29,35 +25,25 @@
                 {
                     "contents": [
                         [],
-                        {
-                            "unName": "Nat"
-                        }
+                        "Nat"
                     ],
                     "tag": "TCon"
                 }
             ],
-            "valConName": {
-                "unName": "C"
-            }
+            "valConName": "C"
         }
     ],
-    "typeDefName": {
-        "unName": "T"
-    },
+    "typeDefName": "T",
     "typeDefNameHints": [],
     "typeDefParameters": [
         [
-            {
-                "unName": "a"
-            },
+            "a",
             {
                 "tag": "KType"
             }
         ],
         [
-            {
-                "unName": "b"
-            },
+            "b",
             {
                 "contents": [
                     {