feat(client): advertise reasoning merge capability

packages/server/src/client/daemon-client.test.ts

@@ -60,10 +60,12 @@ function createMockTransport() {
   return {
     transport,
     sent,
-    triggerOpen: () => {
+    triggerOpen: (options?: { preserveSent?: boolean }) => {
       onOpen();
-      // Ignore HELLO handshake payloads in assertions.
-      sent.length = 0;
+      if (!options?.preserveSent) {
+        // Ignore HELLO handshake payloads in assertions.
+        sent.length = 0;
+      }
       onMessage(
         JSON.stringify({
           type: "session",
@@ -214,6 +216,35 @@ test("passes password as HTTP bearer header and WebSocket subprotocol", async ()
   });
 });
 
+test("advertises reasoning_merge_enum in hello", async () => {
+  const logger = createMockLogger();
+  const mock = createMockTransport();
+
+  const client = new DaemonClient({
+    url: "ws://test",
+    clientId: "clsk_unit_test",
+    logger,
+    reconnect: { enabled: false },
+    transportFactory: () => mock.transport,
+  });
+  clients.push(client);
+
+  const connectPromise = client.connect();
+  mock.triggerOpen({ preserveSent: true });
+  await connectPromise;
+
+  expect(mock.sent).toHaveLength(1);
+  expect(JSON.parse(mock.sent[0] as string)).toEqual({
+    type: "hello",
+    clientId: "clsk_unit_test",
+    clientType: "cli",
+    protocolVersion: 1,
+    capabilities: {
+      reasoning_merge_enum: true,
+    },
+  });
+});
+
 test("does not reconnect after close when ensureConnected is called", async () => {
   const logger = createMockLogger();
   const mock = createMockTransport();

packages/server/src/client/daemon-client.ts

@@ -1,4 +1,5 @@
 import type { z } from "zod";
+import { CLIENT_CAPS } from "../shared/client-capabilities.js";
 import {
   AgentCreateFailedStatusPayloadSchema,
   AgentCreatedStatusPayloadSchema,
@@ -3877,6 +3878,9 @@ export class DaemonClient {
           clientId: this.config.clientId,
           clientType: this.config.clientType ?? "cli",
           protocolVersion: 1,
+          capabilities: {
+            [CLIENT_CAPS.reasoningMergeEnum]: true,
+          },
           ...(this.config.appVersion ? { appVersion: this.config.appVersion } : {}),
         }),
       );

packages/server/src/server/websocket-server.relay-reconnect.test.ts

@@ -15,6 +15,7 @@ import {
   encodeTerminalStreamFrame,
   TerminalStreamOpcode,
 } from "../shared/terminal-stream-protocol.js";
+import { CLIENT_CAPS } from "../shared/client-capabilities.js";
 
 type SocketListener = (...args: unknown[]) => void;
 
@@ -47,6 +48,7 @@ const sessionMock = vi.hoisted(() => {
     cleanup = vi.fn(async () => {});
     handleMessage = vi.fn(async () => {});
     handleBinaryFrame = vi.fn((_frame: unknown) => {});
+    supports = vi.fn((capability: string) => this.args.clientCapabilities?.[capability] === true);
     getClientActivity = vi.fn(() => null);
     resetPeakInflight = vi.fn(() => {});
     getRuntimeMetrics = vi.fn(() => ({
@@ -293,12 +295,16 @@ function createDownloadInProgressSpeechReadinessSnapshot(): SpeechReadinessSnaps
   };
 }
 
-function createHelloMessage(clientId: string) {
+function createHelloMessage(
+  clientId: string,
+  options?: { capabilities?: Record<string, boolean> },
+) {
   return {
     type: "hello" as const,
     clientId,
     clientType: "cli" as const,
     protocolVersion: 1,
+    ...(options?.capabilities ? { capabilities: options.capabilities } : {}),
   };
 }
 
@@ -400,6 +406,34 @@ describe("relay external socket reconnect behavior", () => {
     await server.close();
   });
 
+  test("passes hello capabilities through to the created session", async () => {
+    const server = createServer();
+    const socket = new MockSocket();
+
+    await (server as unknown as WebSocketServerInternals).attachSocket(
+      socket,
+      createDirectRequest(),
+    );
+    socket.emit(
+      "message",
+      JSON.stringify(
+        createHelloMessage("client-capabilities", {
+          capabilities: { [CLIENT_CAPS.reasoningMergeEnum]: true },
+        }),
+      ),
+    );
+    await Promise.resolve();
+
+    expect(sessionMock.instances).toHaveLength(1);
+    const session = sessionMock.instances[0]!;
+    expect(session.args.clientCapabilities).toEqual({
+      [CLIENT_CAPS.reasoningMergeEnum]: true,
+    });
+    expect(session.supports(CLIENT_CAPS.reasoningMergeEnum)).toBe(true);
+
+    await server.close();
+  });
+
   test("closes pending connection when hello timeout elapses", async () => {
     const server = createServer();