diff --git a/src/Lean/Data/Lsp/Extra.lean b/src/Lean/Data/Lsp/Extra.lean
index b2914aff60..0a1478477c 100644
--- a/src/Lean/Data/Lsp/Extra.lean
+++ b/src/Lean/Data/Lsp/Extra.lean
@@ -5,6 +5,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Marc Huisinga, Wojciech Nawrocki
 -/
 import Lean.Data.Lsp.Basic
+import Lean.Server.Rpc.Basic
 
 /-! This file contains Lean-specific extensions to LSP. See the structures below for which
 additional requests and notifications are supported. -/
@@ -87,16 +88,6 @@ structure PlainTermGoal where
   range : Range
   deriving FromJson, ToJson
 
-/-- An object which RPC clients can refer to without marshalling. -/
-structure RpcRef where
-  /- NOTE(WN): It is important for this to be a single-field structure
-  in order to deserialize as an `Object` on the JS side. -/
-  p : USize
-  deriving BEq, Hashable, FromJson, ToJson
-
-instance : ToString RpcRef where
-  toString r := toString r.p
-
 /-- `$/lean/rpc/connect` client->server request.
 
 Starts an RPC session at the given file's worker, replying with the new session ID.
diff --git a/src/Lean/Server/FileWorker.lean b/src/Lean/Server/FileWorker.lean
index 29170d366c..538500a871 100644
--- a/src/Lean/Server/FileWorker.lean
+++ b/src/Lean/Server/FileWorker.lean
@@ -332,20 +332,20 @@ section NotificationHandling
     updatePendingRequests (fun pendingRequests => pendingRequests.erase p.id)
 
 def handleRpcRelease (p : Lsp.RpcReleaseParams) : WorkerM Unit := do
-  let st ← get
   -- NOTE(WN): when the worker restarts e.g. due to changed imports, we may receive `rpc/release`
   -- for the previous RPC session. This is fine, just ignore.
-  if let some seshRef := st.rpcSessions.find? p.sessionId then
+  if let some seshRef := (← get).rpcSessions.find? p.sessionId then
     let monoMsNow ← IO.monoMsNow
-    seshRef.modify fun sesh => Id.run do
-      let mut sesh := sesh
+    let discardRefs : StateM RpcObjectStore Unit := do
       for ref in p.refs do
-        sesh := sesh.release ref |>.snd
-      sesh.keptAlive monoMsNow
+        discard do rpcReleaseRef ref
+    seshRef.modify fun st =>
+      let st := st.keptAlive monoMsNow
+      let ((), objects) := discardRefs st.objects
+      { st with objects }
 
 def handleRpcKeepAlive (p : Lsp.RpcKeepAliveParams) : WorkerM Unit := do
-  let st ← get
-  match st.rpcSessions.find? p.sessionId with
+  match (← get).rpcSessions.find? p.sessionId with
   | none => return
   | some seshRef =>
     seshRef.modify (·.keptAlive (← IO.monoMsNow))
diff --git a/src/Lean/Server/FileWorker/Utils.lean b/src/Lean/Server/FileWorker/Utils.lean
index e065bd1392..9e637a0482 100644
--- a/src/Lean/Server/FileWorker/Utils.lean
+++ b/src/Lean/Server/FileWorker/Utils.lean
@@ -59,16 +59,7 @@ namespace EditableDocument
 end EditableDocument
 
 structure RpcSession where
-  /-- Objects that are being kept alive for the RPC client, together with their type names,
-  mapped to by their RPC reference.
-
-  Note that we may currently have multiple references to the same object. It is only disposed
-  of once all of those are gone. This simplifies the client a bit as it can drop every reference
-  received separately. -/
-  aliveRefs : Std.PersistentHashMap Lsp.RpcRef (Name × NonScalar)
-  /-- Value to use for the next `RpcRef`. It is monotonically increasing to avoid any possible
-  bugs resulting from its reuse. -/
-  nextRef   : USize
+  objects         : RpcObjectStore
   /-- The `IO.monoMsNow` time when the session expires. See `$/lean/rpc/keepAlive`. -/
   expireTime      : Nat
 
@@ -82,22 +73,11 @@ def new : IO (UInt64 × RpcSession) := do
   and worker restarts. Otherwise, the client may attempt to use outdated references. -/
   let newId ← ByteArray.toUInt64LE! <$> IO.getRandomBytes 8
   let newSesh := {
-    aliveRefs := Std.PersistentHashMap.empty
-    nextRef := 0
+    objects := {}
     expireTime := (← IO.monoMsNow) + keepAliveTimeMs
   }
   return (newId, newSesh)
 
-def store (st : RpcSession) (typeName : Name) (obj : NonScalar) : Lsp.RpcRef × RpcSession :=
-  let ref := ⟨st.nextRef⟩
-  let st' := { st with aliveRefs := st.aliveRefs.insert ref (typeName, obj)
-                       nextRef := st.nextRef + 1 }
-  (ref, st')
-
-def release (st : RpcSession) (ref : Lsp.RpcRef) : Bool × RpcSession :=
-  let released := st.aliveRefs.contains ref
-  (released, { st with aliveRefs := st.aliveRefs.erase ref })
-
 def keptAlive (monoMsNow : Nat) (s : RpcSession) : RpcSession :=
   { s with expireTime := monoMsNow + keepAliveTimeMs }
 
@@ -106,9 +86,4 @@ def hasExpired (s : RpcSession) : IO Bool :=
 
 end RpcSession
 
-instance [Monad m] [MonadStateOf RpcSession m] : MonadRpcSession m where
-  rpcStoreRef typeName obj := modifyGet fun st => st.store typeName obj
-  rpcGetRef r := return (←get).aliveRefs.find? r
-  rpcReleaseRef r := modifyGet fun st => st.release r
-
 end Lean.Server.FileWorker
diff --git a/src/Lean/Server/FileWorker/WidgetRequests.lean b/src/Lean/Server/FileWorker/WidgetRequests.lean
index e34696e885..df9de092dc 100644
--- a/src/Lean/Server/FileWorker/WidgetRequests.lean
+++ b/src/Lean/Server/FileWorker/WidgetRequests.lean
@@ -20,7 +20,7 @@ open Server
 structure MsgToInteractive where
   msg : WithRpcRef MessageData
   indent : Nat
-  deriving Inhabited, RpcEncoding
+  deriving Inhabited, RpcEncodable
 
 builtin_initialize
   registerBuiltinRpcProcedure
@@ -38,7 +38,7 @@ structure InfoPopup where
   exprExplicit : Option CodeWithInfos
   /-- Docstring. In markdown. -/
   doc : Option String
-  deriving Inhabited, RpcEncoding
+  deriving Inhabited, RpcEncodable
 
 /-- Given elaborator info for a particular subexpression. Produce the `InfoPopup`.
 
@@ -118,7 +118,7 @@ builtin_initialize
 structure GetGoToLocationParams where
   kind : GoToKind
   info : WithRpcRef InfoWithCtx
-  deriving RpcEncoding
+  deriving RpcEncodable
 
 builtin_initialize
   registerBuiltinRpcProcedure
diff --git a/src/Lean/Server/Rpc/Basic.lean b/src/Lean/Server/Rpc/Basic.lean
index 45beb67e50..e8e1bd95ad 100644
--- a/src/Lean/Server/Rpc/Basic.lean
+++ b/src/Lean/Server/Rpc/Basic.lean
@@ -4,7 +4,8 @@ Released under Apache 2.0 license as described in the file LICENSE.
 
 Authors: Wojciech Nawrocki
 -/
-import Lean.Data.Lsp.Extra
+import Lean.Data.Json
+import Std.Dynamic
 
 /-! Allows LSP clients to make Remote Procedure Calls to the server.
 
@@ -15,98 +16,113 @@ For example, the client can format an `Expr` without transporting the whole `Env
 All RPC requests are relative to an open file and an RPC session for that file. The client must
 first connect to the session using `$/lean/rpc/connect`. -/
 
+namespace Lean.Lsp
+
+/-- An object which RPC clients can refer to without marshalling. -/
+structure RpcRef where
+  /- NOTE(WN): It is important for this to be a single-field structure
+  in order to deserialize as an `Object` on the JS side. -/
+  p : USize
+  deriving BEq, Hashable, FromJson, ToJson
+
+instance : ToString RpcRef where
+  toString r := toString r.p
+
+end Lean.Lsp
+
 namespace Lean.Server
+open Std
 
-/-- Monads with an RPC session in their state. -/
-class MonadRpcSession (m : Type → Type) where
-  rpcStoreRef (typeName : Name) (obj : NonScalar) : m Lsp.RpcRef
-  rpcGetRef (r : Lsp.RpcRef) : m (Option (Name × NonScalar))
-  rpcReleaseRef (r : Lsp.RpcRef) : m Bool
-export MonadRpcSession (rpcStoreRef rpcGetRef rpcReleaseRef)
+structure RpcObjectStore : Type where
+  /-- Objects that are being kept alive for the RPC client, together with their type names,
+  mapped to by their RPC reference.
 
-instance {m n : Type → Type} [MonadLift m n] [MonadRpcSession m] : MonadRpcSession n where
-  rpcStoreRef typeName obj := liftM (rpcStoreRef typeName obj : m _)
-  rpcGetRef r              := liftM (rpcGetRef r : m _)
-  rpcReleaseRef r          := liftM (rpcReleaseRef r : m _)
+  Note that we may currently have multiple references to the same object. It is only disposed
+  of once all of those are gone. This simplifies the client a bit as it can drop every reference
+  received separately. -/
+  aliveRefs : Std.PersistentHashMap Lsp.RpcRef Dynamic := {}
+  /-- Value to use for the next `RpcRef`. It is monotonically increasing to avoid any possible
+  bugs resulting from its reuse. -/
+  nextRef   : USize := 0
 
-set_option linter.unusedVariables false in
-def RpcEncodable (α : Type) : Type := default
-def RpcEncodable.rpcEncode := 0
-def RpcEncodable.rpcDecode := 0
+def rpcStoreRef (any : Dynamic) : StateM RpcObjectStore Lsp.RpcRef := do
+  let st ← get
+  set { st with
+    aliveRefs := st.aliveRefs.insert ⟨st.nextRef⟩ any
+    nextRef := st.nextRef + 1
+  }
+  return ⟨st.nextRef⟩
 
-/-- `RpcEncoding α β` means that `α` may participate in RPC calls with its on-the-wire LSP encoding
-being `β`. This is useful when `α` contains fields which must be marshalled in a special way. In
-particular, we encode `WithRpcRef` fields as opaque references rather than send their content.
+def rpcGetRef (r : Lsp.RpcRef) : ReaderT RpcObjectStore Id (Option Dynamic) :=
+  return (← read).aliveRefs.find? r
 
-Structures with `From/ToJson` use JSON as their `RpcEncoding`. Structures containing
-non-JSON-serializable fields can be auto-encoded in two ways:
-- `deriving RpcEncoding` acts like `From/ToJson` but marshalls any `WithRpcRef` fields
+def rpcReleaseRef (r : Lsp.RpcRef) : StateM RpcObjectStore Bool := do
+  let st ← get
+  if st.aliveRefs.contains r then
+    set { st with aliveRefs := st.aliveRefs.erase r }
+    return true
+  else
+    return false
+
+/--
+`RpcEncodable α` means that `α` can be serialized in the RPC system of the Lean server.
+This is required when `α` contains fields which should be serialized as an RPC reference
+instead of being sent in full.
+The type wrapper `WithRpcRef` is used for these fields which should be sent as
+a reference.
+
+- Any type with `FromJson` and `ToJson` instance is automatically `RpcEncodable`.
+- If a type has an `Std.Dynamic` instance, then `WithRpcRef` can be used for its references.
+- `deriving RpcEncodable` acts like `FromJson`/`ToJson` but marshalls any `WithRpcRef` fields
   as `Lsp.RpcRef`s.
-- `deriving RpcEncoding with { withRef := true }` generates an encoding for
-  `WithRpcRef TheType`. -/
--- TODO(WN): for Lean.js, have third parameter defining the client-side structure;
--- or, compile `WithRpcRef` to "opaque reference" on the client
-class RpcEncoding (α : Type) (β : outParam Type) where
-  rpcEncode {m : Type → Type} [Monad m] [MonadRpcSession m] : α → ExceptT String m β
-  rpcDecode {m : Type → Type} [Monad m] [MonadRpcSession m] : β → ExceptT String m α
-export RpcEncoding (rpcEncode rpcDecode)
+-/
+-- TODO(WN): for Lean.js, compile `WithRpcRef` to "opaque reference" on the client
+class RpcEncodable (α : Type) where
+  rpcEncode : α → StateM RpcObjectStore Json
+  rpcDecode : Json → ExceptT String (ReaderT RpcObjectStore Id) α
+export RpcEncodable (rpcEncode rpcDecode)
 
-instance : Nonempty (RpcEncoding α β) :=
-  ⟨{ rpcEncode := fun _ => throw "unreachable", rpcDecode := fun _ => throw "unreachable" }⟩
+instance : Nonempty (RpcEncodable α) :=
+  ⟨{ rpcEncode := default, rpcDecode := default }⟩
 
-instance [FromJson α] [ToJson α] : RpcEncoding α α where
-  rpcEncode := pure
-  rpcDecode := pure
+instance [FromJson α] [ToJson α] : RpcEncodable α where
+  rpcEncode a := return toJson a
+  rpcDecode j := ofExcept (fromJson? j)
 
-instance [RpcEncoding α β] : RpcEncoding (Option α) (Option β) where
-  rpcEncode v := match v with
-    | none => pure none
-    | some v => some <$> rpcEncode v
-  rpcDecode v := match v with
-    | none => pure none
-    | some v => some <$> rpcDecode v
+instance [RpcEncodable α] : RpcEncodable (Option α) where
+  rpcEncode v := toJson <$> v.mapM rpcEncode
+  rpcDecode j := do Option.mapM rpcDecode (← fromJson? j)
 
--- TODO(WN): instance [RpcEncoding α β] [Traversable t] : RpcEncoding (t α) (t β)
-instance [RpcEncoding α β] : RpcEncoding (Array α) (Array β) where
-  rpcEncode a := a.mapM rpcEncode
-  rpcDecode b := b.mapM rpcDecode
+-- TODO(WN): instance [RpcEncodable α β] [Traversable t] : RpcEncodable (t α) (t β)
 
-instance [RpcEncoding α α'] [RpcEncoding β β'] : RpcEncoding (α × β) (α' × β') where
-  rpcEncode := fun (a, b) => do
-    let a' ← rpcEncode a
-    let b' ← rpcEncode b
-    return (a', b')
-  rpcDecode := fun (a', b') => do
-    let a ← rpcDecode a'
-    let b ← rpcDecode b'
-    return (a, b)
+instance [RpcEncodable α] : RpcEncodable (Array α) where
+  rpcEncode a := toJson <$> a.mapM rpcEncode
+  rpcDecode b := do Array.mapM rpcDecode (← fromJson? b)
 
-structure RpcEncoding.DerivingParams where
-  withRef : Bool := false
+instance [RpcEncodable α] [RpcEncodable β] : RpcEncodable (α × β) where
+  rpcEncode := fun (a, b) => return toJson (← rpcEncode a, ← rpcEncode b)
+  rpcDecode j := do
+    let (a, b) ← fromJson? j
+    return (← rpcDecode a, ← rpcDecode b)
 
 /-- Marks fields to encode as opaque references in LSP packets. -/
 structure WithRpcRef (α : Type u) where
   val : α
   deriving Inhabited
 
-namespace WithRpcRef
+instance [TypeName α] : RpcEncodable (WithRpcRef α) :=
+  { rpcEncode, rpcDecode }
+where
+  -- separate definitions to prevent inlining
+  rpcEncode r := toJson <$> rpcStoreRef (.mk r.val)
+  rpcDecode j := do
+    let r ← fromJson? j
+    match (← rpcGetRef r) with
+      | none => throw s!"RPC reference '{r}' is not valid"
+      | some any =>
+        if let some obj := any.get? α then
+          return ⟨obj⟩
+        else
+          throw s!"RPC call type mismatch in reference '{r}'\nexpected '{TypeName.typeName α}', got '{any.typeName}'"
 
-variable {m : Type → Type} [Monad m] [MonadRpcSession m]
-
-/-- This is unsafe because we must ensure that:
-- the stored `NonScalar` is never used to access the value as a type other than `α`
-- the type `α` is not a scalar -/
-protected unsafe def encodeUnsafe [Monad m] (typeName : Name) (r : WithRpcRef α) : m Lsp.RpcRef := do
-  let obj := @unsafeCast α NonScalar r.val
-  rpcStoreRef typeName obj
-
-protected unsafe def decodeUnsafeAs (α) (typeName : Name) (r : Lsp.RpcRef) : ExceptT String m (WithRpcRef α) := do
-  match (← rpcGetRef r) with
-    | none => throw s!"RPC reference '{r}' is not valid"
-    | some (nm, obj) =>
-      if nm != typeName then
-        throw s!"RPC call type mismatch in reference '{r}'\nexpected '{typeName}', got '{nm}'"
-      return WithRpcRef.mk <| @unsafeCast NonScalar α obj
-
-end WithRpcRef
 end Lean.Server
diff --git a/src/Lean/Server/Rpc/RequestHandling.lean b/src/Lean/Server/Rpc/RequestHandling.lean
index 5ad94572cf..1f11482aaf 100644
--- a/src/Lean/Server/Rpc/RequestHandling.lean
+++ b/src/Lean/Server/Rpc/RequestHandling.lean
@@ -20,7 +20,6 @@ that users don't need to import core Lean modules to make builtin handlers work,
 they *can* easily create custom handlers and use them in the same file. -/
 builtin_initialize builtinRpcProcedures : IO.Ref (Std.PHashMap Name RpcProcedure) ←
   IO.mkRef {}
-
 builtin_initialize userRpcProcedures : MapDeclarationExtension Name ←
   mkMapDeclarationExtension `userRpcProcedures
 
@@ -56,8 +55,7 @@ builtin_initialize
   registerLspRequestHandler "$/lean/rpc/call" Lsp.RpcCallParams Json handleRpcCall
 
 def wrapRpcProcedure (method : Name) paramType respType
-    {paramLspType} [RpcEncoding paramType paramLspType] [FromJson paramLspType]
-    {respLspType} [RpcEncoding respType respLspType] [ToJson respLspType]
+    [RpcEncodable paramType] [RpcEncodable respType]
     (handler : paramType → RequestM (RequestTask respType)) : RpcProcedure :=
   ⟨fun seshId j => do
     let rc ← read
@@ -66,9 +64,7 @@ def wrapRpcProcedure (method : Name) paramType respType
       | throwThe RequestError { code := JsonRpc.ErrorCode.rpcNeedsReconnect
                                 message := s!"Outdated RPC session" }
     let t ← RequestM.asTask do
-      let paramsLsp ← liftExcept <| parseRequestParams paramLspType j
-      let act := rpcDecode (α := paramType) (β := paramLspType) (m := StateM FileWorker.RpcSession) paramsLsp
-      match act.run' (← seshRef.get) with
+      match rpcDecode j (← seshRef.get).objects with
       | Except.ok v => return v
       | Except.error e => throwThe RequestError {
           code := JsonRpc.ErrorCode.invalidParams
@@ -81,23 +77,12 @@ def wrapRpcProcedure (method : Name) paramType respType
 
     RequestM.mapTask t fun
       | Except.error e => throw e
-      | Except.ok ret => do
-        let act : StateM FileWorker.RpcSession (Except String respLspType) := do
-          let s ← get
-          match ← rpcEncode (α := respType) (β := respLspType) (m := StateM FileWorker.RpcSession) ret with
-            | .ok x => return .ok x
-            | .error e => set s; return .error e
-        match ← seshRef.modifyGet act.run with
-          | .ok x => return toJson x
-          | .error e =>
-            throwThe RequestError {
-              code := JsonRpc.ErrorCode.invalidParams
-              message := s!"Cannot encode result of RPC call '{method}'\n{e}"
-            }⟩
+      | Except.ok ret =>
+        seshRef.modifyGet fun st =>
+          rpcEncode ret st.objects |>.map id ({st with objects := ·})⟩
 
 def registerBuiltinRpcProcedure (method : Name) paramType respType
-    {paramLspType} [RpcEncoding paramType paramLspType] [FromJson paramLspType]
-    {respLspType} [RpcEncoding respType respLspType] [ToJson respLspType]
+    [RpcEncodable paramType] [RpcEncodable respType]
     (handler : paramType → RequestM (RequestTask respType)) : IO Unit := do
   let errMsg := s!"Failed to register builtin RPC call handler for '{method}'"
   unless (← IO.initializing) do
@@ -137,7 +122,7 @@ builtin_initialize registerBuiltinAttribute {
   descr := "Marks a function as a Lean server RPC method.
     Shorthand for `registerRpcProcedure`.
     The function must have type `α → RequestM (RequestTask β)` with
-    RpcEncodings for both α and β."
+    `[RpcEncodable α]` and `[RpcEncodable β]`."
   applicationTime := AttributeApplicationTime.afterCompilation
   add := fun decl _ _ =>
     registerRpcProcedure decl
diff --git a/src/Lean/Widget/Basic.lean b/src/Lean/Widget/Basic.lean
index 3ca433e116..52c2e442df 100644
--- a/src/Lean/Widget/Basic.lean
+++ b/src/Lean/Widget/Basic.lean
@@ -18,9 +18,9 @@ functionality is purpose-specific to showing the contents of infoview popups.
 structure InfoWithCtx where
   ctx  : Elab.ContextInfo
   info : Elab.Info
-  deriving Inhabited, RpcEncoding with { withRef := true }
+  deriving Inhabited, Std.TypeName
 
-deriving instance RpcEncoding with { withRef := true } for MessageData
+deriving instance Std.TypeName for MessageData
 
 instance : ToJson FVarId := ⟨fun f => toJson f.name⟩
 instance : ToJson MVarId := ⟨fun f => toJson f.name⟩
diff --git a/src/Lean/Widget/InteractiveCode.lean b/src/Lean/Widget/InteractiveCode.lean
index 7f25dd8b8c..6258bc7c3f 100644
--- a/src/Lean/Widget/InteractiveCode.lean
+++ b/src/Lean/Widget/InteractiveCode.lean
@@ -24,7 +24,7 @@ structure SubexprInfo where
   subexprPos : Lean.SubExpr.Pos
   -- TODO(WN): add fields for semantic highlighting
   -- kind : Lsp.SymbolKind
-  deriving Inhabited, RpcEncoding
+  deriving Inhabited, RpcEncodable
 
 /-- Pretty-printed syntax (usually but not necessarily an `Expr`) with embedded `Info`s. -/
 abbrev CodeWithInfos := TaggedText SubexprInfo
diff --git a/src/Lean/Widget/InteractiveDiagnostic.lean b/src/Lean/Widget/InteractiveDiagnostic.lean
index a22c58d11b..59727ebf29 100644
--- a/src/Lean/Widget/InteractiveDiagnostic.lean
+++ b/src/Lean/Widget/InteractiveDiagnostic.lean
@@ -15,14 +15,14 @@ inductive MsgEmbed where
   | expr : CodeWithInfos → MsgEmbed
   | goal : InteractiveGoal → MsgEmbed
   | lazyTrace : Nat → Name → WithRpcRef MessageData → MsgEmbed
-  deriving Inhabited, RpcEncoding
+  deriving Inhabited, RpcEncodable
 
 /-- We embed objects in LSP diagnostics by storing them in the tag of an empty subtree (`text ""`).
 In other words, we terminate the `MsgEmbed`-tagged tree at embedded objects and instead store
 the pretty-printed embed (which can itself be a `TaggedText`) in the tag. -/
 abbrev InteractiveDiagnostic := Lsp.DiagnosticWith (TaggedText MsgEmbed)
 
-deriving instance RpcEncoding for Lsp.DiagnosticWith
+deriving instance RpcEncodable for Lsp.DiagnosticWith
 
 namespace InteractiveDiagnostic
 open MsgEmbed
diff --git a/src/Lean/Widget/InteractiveGoal.lean b/src/Lean/Widget/InteractiveGoal.lean
index 12b580723e..bc00558b43 100644
--- a/src/Lean/Widget/InteractiveGoal.lean
+++ b/src/Lean/Widget/InteractiveGoal.lean
@@ -6,6 +6,7 @@ Authors: Wojciech Nawrocki
 -/
 import Lean.Meta.PPGoal
 import Lean.Widget.InteractiveCode
+import Lean.Data.Lsp.Extra
 
 /-! RPC procedures for retrieving tactic and term goals with embedded `CodeWithInfos`. -/
 
@@ -21,7 +22,7 @@ structure InteractiveHypothesisBundle where
   val? : Option CodeWithInfos := none
   isInstance : Bool
   isType : Bool
-  deriving Inhabited, RpcEncoding
+  deriving Inhabited, RpcEncodable
 
 structure InteractiveGoal where
   hyps      : Array InteractiveHypothesisBundle
@@ -32,7 +33,7 @@ structure InteractiveGoal where
   name of the MVar that it is a goal for.)
   This is none when we are showing a term goal. -/
   mvarId? : Option MVarId := none
-  deriving Inhabited, RpcEncoding
+  deriving Inhabited, RpcEncodable
 
 namespace InteractiveGoal
 
@@ -69,7 +70,7 @@ structure InteractiveTermGoal where
   hyps      : Array InteractiveHypothesisBundle
   type      : CodeWithInfos
   range     : Lsp.Range
-  deriving Inhabited, RpcEncoding
+  deriving Inhabited, RpcEncodable
 
 namespace InteractiveTermGoal
 
@@ -80,7 +81,7 @@ end InteractiveTermGoal
 
 structure InteractiveGoals where
   goals : Array InteractiveGoal
-  deriving RpcEncoding
+  deriving RpcEncodable
 
 open Meta in
 def addInteractiveHypothesisBundle (hyps : Array InteractiveHypothesisBundle) (ids : Array (Name × FVarId)) (type : Expr) (value? : Option Expr := none) : MetaM (Array InteractiveHypothesisBundle) := do
diff --git a/src/Lean/Widget/TaggedText.lean b/src/Lean/Widget/TaggedText.lean
index ddb3cda569..b97e15348b 100644
--- a/src/Lean/Widget/TaggedText.lean
+++ b/src/Lean/Widget/TaggedText.lean
@@ -63,9 +63,9 @@ partial def rewriteM : TaggedText α → m (TaggedText β)
   | append as => return append (← as.mapM rewriteM)
   | tag t a => f t a
 
-instance [RpcEncoding α β] : RpcEncoding (TaggedText α) (TaggedText β) where
-  rpcEncode a := a.mapM rpcEncode
-  rpcDecode a := a.mapM rpcDecode
+instance [RpcEncodable α] : RpcEncodable (TaggedText α) where
+  rpcEncode a := toJson <$> a.mapM rpcEncode
+  rpcDecode a := do TaggedText.mapM rpcDecode (← fromJson? a)
 
 private structure TaggedState where
   out      : TaggedText (Nat × Nat)              := TaggedText.text ""
diff --git a/tests/lean/derivingRpcEncoding.lean b/tests/lean/derivingRpcEncoding.lean
index 4608ebbf6f..7008783919 100644
--- a/tests/lean/derivingRpcEncoding.lean
+++ b/tests/lean/derivingRpcEncoding.lean
@@ -2,30 +2,21 @@ import Lean.Server.Rpc.Basic
 
 open Lean Server
 
-abbrev M := StateM (Array (Name × NonScalar))
+abbrev M := StateM RpcObjectStore
 
-instance : MonadRpcSession M where
-  rpcStoreRef typeName obj :=
-    (return ⟨(← get).size.toUSize⟩) <* modify (·.push (typeName, obj))
-  rpcGetRef r := return (← get)[r.p]?
-  rpcReleaseRef _ := return false
+def M.run (x : ExceptT String M α) : Except String α :=
+  x.run' {}
 
-def M.run (x : ExceptT String M α) : Except String α := x.run' #[]
-
-def test (α : Type) [RpcEncoding α β] [FromJson β] [ToJson β] (a : α) := M.run do
-  let json := toJson (← rpcEncode a)
-  let packet ← ofExcept (fromJson? (α := β) json)
-  let _ ← rpcDecode (α := α) packet
+def test (α : Type) [RpcEncodable α] (a : α) := M.run do
+  let json ← rpcEncode a
+  let _a : α ← ofExcept (rpcDecode json (← get))
   return json
 
-@[reducible]
-def rpcPacketFor (α : Type) {β : outParam Type} [RpcEncoding α β] := β
-
 structure FooRef where
   a : Array Nat
-  deriving Inhabited, RpcEncoding with { withRef := true }
+  deriving Inhabited, Std.TypeName
 
-#check instRpcEncodingWithRpcRefFooRefRpcRef
+#check instTypeNameFooRef
 #eval test (WithRpcRef FooRef) default
 
 structure FooJson where
@@ -35,75 +26,75 @@ structure FooJson where
 structure Bar where
   fooRef : WithRpcRef FooRef
   fooJson : FooJson
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingBar
+#check instRpcEncodableBar
 #eval test Bar default
 
 structure BarTrans where
   bar : Bar
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingBarTrans
+#check instRpcEncodableBarTrans
 #eval test BarTrans default
 
 structure Baz where
   arr : Array String -- non-constant field
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingBaz
+#check instRpcEncodableBaz
 #eval test Baz default
 
 structure FooGeneric (α : Type) where
   a : α
   b? : Option α
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingFooGeneric
+#check @instRpcEncodableFooGeneric
 #eval test (FooGeneric Nat) default
 #eval test (FooGeneric Nat) { a := 3, b? := some 42 }
 
 inductive BazInductive
   | baz (arr : Array Bar)
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingBazInductive
+#check @instRpcEncodableBazInductive
 #eval test BazInductive ⟨#[default, default]⟩
 
 inductive FooInductive (α : Type) where
   | a : α → WithRpcRef FooRef → FooInductive α
   | b : (n : Nat) → (a : α) → (m : Nat) → FooInductive α
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingFooInductive
+#check @instRpcEncodableFooInductive
 #eval test (FooInductive BazInductive) (.a default default)
 #eval test (FooInductive BazInductive) (.b 42 default default)
 
 inductive FooNested (α : Type) where
   | a : α → Array (FooNested α) → FooNested α
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
 #eval test (FooNested BazInductive) (.a default #[default])
 
 inductive FooParam (n : Nat) where
   | a : Nat → FooParam n
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingFooParam
+#check @instRpcEncodableFooParam
 #eval test (FooParam 10) (.a 42)
 
 inductive Unused (α : Type) | a
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingUnused
-structure NoRpcEncoding
-#eval test (Unused NoRpcEncoding) default
+#check @instRpcEncodableUnused
+structure NoRpcEncodable
+#eval test (Unused NoRpcEncodable) default
 
 structure UnusedStruct (α : Type)
-  deriving RpcEncoding, Inhabited
+  deriving RpcEncodable, Inhabited
 
-#check instRpcEncodingUnusedStruct
-#eval test (UnusedStruct NoRpcEncoding) default
+#check @instRpcEncodableUnusedStruct
+#eval test (UnusedStruct NoRpcEncodable) default
 
-deriving instance Repr, RpcEncoding for Empty
-#eval M.run do rpcDecode (α := Empty) (← fromJson? .null)
+deriving instance Repr, RpcEncodable for Empty
+#eval rpcDecode (α := Empty) .null {}
diff --git a/tests/lean/derivingRpcEncoding.lean.expected.out b/tests/lean/derivingRpcEncoding.lean.expected.out
index 281522e27f..c2e356e0ce 100644
--- a/tests/lean/derivingRpcEncoding.lean.expected.out
+++ b/tests/lean/derivingRpcEncoding.lean.expected.out
@@ -1,29 +1,27 @@
-instRpcEncodingWithRpcRefFooRefRpcRef : RpcEncoding (WithRpcRef FooRef) Lsp.RpcRef
+instTypeNameFooRef : Std.TypeName FooRef
 ok: {"p": "0"}
-instRpcEncodingBar : RpcEncoding Bar RpcEncodingPacket✝
+instRpcEncodableBar : RpcEncodable Bar
 ok: {"fooRef": {"p": "0"}, "fooJson": {"s": ""}}
-instRpcEncodingBarTrans : RpcEncoding BarTrans RpcEncodingPacket✝
+instRpcEncodableBarTrans : RpcEncodable BarTrans
 ok: {"bar": {"fooRef": {"p": "0"}, "fooJson": {"s": ""}}}
-instRpcEncodingBaz : RpcEncoding Baz RpcEncodingPacket✝
+instRpcEncodableBaz : RpcEncodable Baz
 ok: {"arr": []}
-instRpcEncodingFooGeneric : (α αPacket : Type) →
-  [inst : RpcEncoding α αPacket] → RpcEncoding (FooGeneric α) (RpcEncodingPacket✝ αPacket)
+@instRpcEncodableFooGeneric : {α : Type} → [inst : RpcEncodable α] → RpcEncodable (FooGeneric α)
 ok: {"a": 0}
 ok: {"b": 42, "a": 3}
-instRpcEncodingBazInductive : RpcEncoding BazInductive RpcEncodingPacket✝
+instRpcEncodableBazInductive : RpcEncodable BazInductive
 ok: {"baz":
  {"arr":
   [{"fooRef": {"p": "0"}, "fooJson": {"s": ""}},
    {"fooRef": {"p": "1"}, "fooJson": {"s": ""}}]}}
-instRpcEncodingFooInductive : (α αPacket : Type) →
-  [inst : RpcEncoding α αPacket] → RpcEncoding (FooInductive α) (RpcEncodingPacket✝ αPacket)
+@instRpcEncodableFooInductive : {α : Type} → [inst : RpcEncodable α] → RpcEncodable (FooInductive α)
 ok: {"a": [{"baz": {"arr": []}}, {"p": "0"}]}
 ok: {"b": {"n": 42, "m": 0, "a": {"baz": {"arr": []}}}}
 ok: {"a": [{"baz": {"arr": []}}, [{"a": [{"baz": {"arr": []}}, []]}]]}
-instRpcEncodingFooParam : (n : Nat) → RpcEncoding (FooParam n) RpcEncodingPacket✝
+@instRpcEncodableFooParam : {n : Nat} → RpcEncodable (FooParam n)
 ok: {"a": 42}
-instRpcEncodingUnused : (α : Type) → RpcEncoding (Unused α) RpcEncodingPacket✝
+@instRpcEncodableUnused : {α : Type} → RpcEncodable (Unused α)
 ok: "a"
-instRpcEncodingUnusedStruct : (α : Type) → RpcEncoding (UnusedStruct α) RpcEncodingPacket✝
+@instRpcEncodableUnusedStruct : {α : Type} → RpcEncodable (UnusedStruct α)
 ok: {}
 Except.error "no inductive constructor matched"