diff --git a/integration-tests/cli/qwen-serve-live-journal-recovery.test.ts b/integration-tests/cli/qwen-serve-live-journal-recovery.test.ts
index f15b03464e4..9ae67e60d37 100644
--- a/integration-tests/cli/qwen-serve-live-journal-recovery.test.ts
+++ b/integration-tests/cli/qwen-serve-live-journal-recovery.test.ts
@@ -81,6 +81,15 @@ describe('qwen serve live journal recovery', () => {
       expect(replayText).toContain('chunk-19');
 
       await prompt;
+
+      // Gate the fixture's session-close ack: the only other consumer of
+      // this path is the opt-in loadtest, so without this call a drifted
+      // close method name or missing close handler would surface only in
+      // the post-merge E2E workflow (ack-shape drift is absorbed by the
+      // daemon's cancel fallback and is not observable from the client).
+      await expect(
+        activeDaemon.client.closeSession(created.sessionId),
+      ).resolves.toBeUndefined();
     } finally {
       await activeDaemon?.dispose();
       activeDaemon = undefined;
diff --git a/integration-tests/fixtures/mock-acp-child/agent.mjs b/integration-tests/fixtures/mock-acp-child/agent.mjs
index 5e1ad0ee216..f99e8de7fc1 100644
--- a/integration-tests/fixtures/mock-acp-child/agent.mjs
+++ b/integration-tests/fixtures/mock-acp-child/agent.mjs
@@ -55,6 +55,12 @@ delete process.env[PRIVATE_EXTERNAL_TOOL_GUARD_PROVIDER_ENV];
 const externalToolGuardRequired =
   externalToolGuardMarker === EXTERNAL_TOOL_GUARD_REQUIRED_VALUE;
 
+// SERVE_CONTROL_EXT_METHODS.sessionClose from @qwen-code/acp-bridge/status,
+// hardcoded because that module runtime-imports @qwen-code/qwen-code-core
+// and would pull core's whole barrel into this lightweight fixture. Drift
+// fails loudly: the daemon's session close errors when this stops matching.
+const SESSION_CLOSE_EXT_METHOD = 'qwen/control/session/close';
+
 new AgentSideConnection(
   (connection) => ({
     async initialize() {
@@ -119,6 +125,17 @@ new AgentSideConnection(
     },
 
     async cancel() {},
+
+    async extMethod(method, params) {
+      if (method === SESSION_CLOSE_EXT_METHOD) {
+        // The daemon's DELETE /session/:id forwards this ext method down the
+        // ACP channel; ack with the production success shape so teardown
+        // completes. The mock keeps no per-session state to drain.
+        const { sessionId } = params;
+        return { sessionId, closed: true };
+      }
+      throw RequestError.methodNotFound(method);
+    },
   }),
   ndJsonStream(Writable.toWeb(process.stdout), Readable.toWeb(process.stdin)),
 );