fix(acp): use small unique request IDs for Kotlin agents

packages/effect-acp/src/agent.test.ts

@@ -35,6 +35,8 @@ const SessionCancelNotification = jsonRpcNotification(
 const ExtPingNotification = jsonRpcNotification("x/ping", Schema.Struct({ count: Schema.Number }));
 const ExtRequest = jsonRpcRequest("x/test", Schema.Struct({ hello: Schema.String }));
 const ExtResponse = jsonRpcResponse(Schema.Struct({ ok: Schema.Boolean }));
+/** Peers on the Kotlin ACP SDK (Junie) decode numeric request ids as a signed 32-bit Int. */
+const isInt32RequestId = Schema.is(Schema.Number.check(Schema.isInt32()));
 /** A response whose cause is a handler's defect, as RpcServer encodes it. */
 const DieResponse = Schema.Struct({
   id: Schema.Number,
@@ -226,7 +228,7 @@ it.effect("effect-acp agent handles core agent requests and outbound client requ
   }),
 );
 
-it.effect("effect-acp agent uses distinct ids for RPC calls and extension requests", () =>
+it.effect("effect-acp agent keeps RPC and extension ids distinct and within signed 32-bit", () =>
   Effect.gen(function* () {
     const { stdio, input, output } = yield* makeInMemoryStdio();
     const scope = yield* Scope.make();
@@ -275,6 +277,7 @@ it.effect("effect-acp agent uses distinct ids for RPC calls and extension reques
         : yield* decodedExt(firstOutbound);
 
       assert.notEqual(permissionRequest.id, extRequest.id);
+      assert.isTrue(isInt32RequestId(permissionRequest.id) && isInt32RequestId(extRequest.id));
 
       yield* Queue.offer(
         input,

packages/effect-acp/src/agent.ts

@@ -436,9 +436,8 @@ export const make = Effect.fn("effect-acp/AcpAgent.make")(function* (
     Effect.forkScoped,
   );
 
-  let nextRpcRequestId = 2 ** 32;
   const rpc = yield* RpcClient.make(AcpRpcs.ClientRpcs, {
-    generateRequestId: () => RpcMessage.RequestId(nextRpcRequestId++),
+    generateRequestId: () => RpcMessage.RequestId(transport.nextRequestId()),
   }).pipe(Effect.provideService(RpcClient.Protocol, transport.clientProtocol));
 
   return AcpAgent.of({

packages/effect-acp/src/client.test.ts

@@ -42,6 +42,8 @@ const PromptRequestV1 = jsonRpcRequest("session/prompt", AcpSchemaV1.PromptReque
 const PromptResponseV1 = jsonRpcResponse(AcpSchemaV1.PromptResponse);
 const ExtRequest = jsonRpcRequest("x/test", Schema.Struct({ hello: Schema.String }));
 const ExtResponse = jsonRpcResponse(Schema.Struct({ ok: Schema.Boolean }));
+/** Peers on the Kotlin ACP SDK (Junie) decode numeric request ids as a signed 32-bit Int. */
+const isInt32RequestId = Schema.is(Schema.Number.check(Schema.isInt32()));
 const PromptRequest = jsonRpcRequest("session/prompt", AcpSchema.PromptRequest);
 const PromptResponse = jsonRpcResponse(AcpSchema.PromptResponse);
 const SessionUpdateNotification = jsonRpcNotification("session/update", Schema.Unknown);
@@ -755,7 +757,7 @@ it.layer(NodeServices.layer)("effect-acp client", (it) => {
     }),
   );
 
-  it.effect("uses distinct ids for RPC calls and extension requests", () =>
+  it.effect("keeps RPC and extension ids distinct and within signed 32-bit", () =>
     Effect.gen(function* () {
       const { stdio, input, output } = yield* makeInMemoryStdio();
       const scope = yield* Scope.make();
@@ -796,6 +798,7 @@ it.layer(NodeServices.layer)("effect-acp client", (it) => {
         : yield* decodedExt(firstOutbound);
 
       assert.notEqual(initializeRequest.id, extRequest.id);
+      assert.isTrue(isInt32RequestId(initializeRequest.id) && isInt32RequestId(extRequest.id));
 
       yield* Queue.offer(
         input,

packages/effect-acp/src/client.ts

@@ -1113,9 +1113,8 @@ export const make = Effect.fn("effect-acp/AcpClient.make")(function* (
     Effect.forkScoped,
   );
 
-  let nextRpcRequestId = 2 ** 32;
   const rpc = yield* RpcClient.make(AcpRpcs.CompatAgentRpcs, {
-    generateRequestId: () => RpcMessage.RequestId(nextRpcRequestId++),
+    generateRequestId: () => RpcMessage.RequestId(transport.nextRequestId()),
   }).pipe(Effect.provideService(RpcClient.Protocol, transport.clientProtocol));
 
   return AcpClient.of({

packages/effect-acp/src/protocol.ts

@@ -121,6 +121,15 @@ export interface AcpPatchedProtocol {
   readonly incoming: Stream.Stream<AcpIncomingNotification>;
   readonly request: (method: string, payload: unknown) => Effect.Effect<unknown, AcpError.AcpError>;
   readonly notify: (method: string, payload: unknown) => Effect.Effect<void, AcpError.AcpError>;
+  /**
+   * Allocates the next outbound request id. Pass it to `RpcClient.make` as
+   * `generateRequestId` so typed calls and `request` share one counter and ids
+   * stay unique per connection. Ids count up from 1, so they start small enough
+   * for peers built on the Kotlin ACP SDK (Junie), which decode them as signed
+   * 32-bit integers. The counter is not bounded; only a connection that sends
+   * over 2^31 - 1 requests would leave that range.
+   */
+  readonly nextRequestId: () => number;
 }
 
 interface AcpPendingRequest {
@@ -222,7 +231,8 @@ export const makeAcpPatchedProtocol = Effect.fn("makeAcpPatchedProtocol")(functi
     intentionalEnd: false,
     outstandingAcknowledgements: new Set(),
   });
-  const nextRequestId = yield* Ref.make(1);
+  let lastRequestId = 0;
+  const nextRequestId = () => ++lastRequestId;
   const terminationHandled = yield* Ref.make(false);
   const terminationFailure = yield* Deferred.make<never, AcpError.AcpError>();
   const extPending = yield* Ref.make(new Map<string, AcpPendingRequest>());
@@ -946,10 +956,7 @@ export const makeAcpPatchedProtocol = Effect.fn("makeAcpPatchedProtocol")(functi
 
   const sendRequest = Effect.fn("sendRequest")(function* (method: string, payload: unknown) {
     yield* ensureActive;
-    const requestId = yield* Ref.modify(
-      nextRequestId,
-      (current) => [current, current + 1] as const,
-    );
+    const requestId = nextRequestId();
     const deferred = yield* Deferred.make<unknown, AcpError.AcpError>();
     yield* Ref.update(extPending, (pending) =>
       new Map(pending).set(acpRequestIdentity(requestId), { deferred, method }),
@@ -974,6 +981,7 @@ export const makeAcpPatchedProtocol = Effect.fn("makeAcpPatchedProtocol")(functi
     },
     request: sendRequest,
     notify: sendNotification,
+    nextRequestId,
   } satisfies AcpPatchedProtocol;
 });