Guard against phantom "I'll be notified" dead-end finals at delivery

An agent could end a turn with "I'll wait for the build to complete — I'll be
notified" without registering any watcher, so nothing ever resumed and the user
was left staring at a dead-end (observed in the tts_site room). The prompt rule
alone did not stop the model. At final-delivery time, when the final reads like
such a phantom-notification dead-end AND no CI watcher is active for the chat,
append an explicit notice telling the user no notification is coming and to send
a follow-up — turning a silent hang into an actionable prompt. Pure detector +
guard with unit tests; wired into the owner/reviewer final-delivery path.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/phantom-notification-guard.test.ts

@@ -0,0 +1,76 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+  applyPhantomNotificationGuard,
+  isPhantomNotificationDeadEnd,
+  PHANTOM_NOTIFICATION_NOTICE,
+} from './phantom-notification-guard.js';
+
+describe('isPhantomNotificationDeadEnd', () => {
+  it('detects the reported "I\'ll wait for the build … I\'ll be notified" final', () => {
+    expect(
+      isPhantomNotificationDeadEnd(
+        "I'll wait for the build to complete — I'll be notified.",
+      ),
+    ).toBe(true);
+  });
+
+  it('detects close variants of the notification promise', () => {
+    expect(isPhantomNotificationDeadEnd('I will be notified when it finishes.')).toBe(
+      true,
+    );
+    expect(
+      isPhantomNotificationDeadEnd('Waiting for the deploy to finish now.'),
+    ).toBe(true);
+    expect(
+      isPhantomNotificationDeadEnd("I'll be notified once CI is green."),
+    ).toBe(true);
+  });
+
+  it('does not flag ordinary status finals', () => {
+    expect(
+      isPhantomNotificationDeadEnd(
+        'TASK_DONE\n빌드를 끝냈고 테스트 1597개가 모두 통과했습니다.',
+      ),
+    ).toBe(false);
+    expect(
+      isPhantomNotificationDeadEnd('The build completed and I pushed the fix.'),
+    ).toBe(false);
+    expect(isPhantomNotificationDeadEnd('')).toBe(false);
+  });
+});
+
+describe('applyPhantomNotificationGuard', () => {
+  const deadEnd = "I'll wait for the build to complete — I'll be notified.";
+
+  it('appends the follow-up notice for a dead-end final with no active watcher', () => {
+    const result = applyPhantomNotificationGuard(deadEnd, {
+      hasActiveWatcher: false,
+    });
+    expect(result.startsWith(deadEnd)).toBe(true);
+    expect(result).toContain(PHANTOM_NOTIFICATION_NOTICE.trim());
+  });
+
+  it('leaves the final untouched when a watcher is actually active', () => {
+    expect(
+      applyPhantomNotificationGuard(deadEnd, { hasActiveWatcher: true }),
+    ).toBe(deadEnd);
+  });
+
+  it('leaves ordinary finals untouched', () => {
+    const ok = 'TASK_DONE\n작업을 마쳤습니다.';
+    expect(applyPhantomNotificationGuard(ok, { hasActiveWatcher: false })).toBe(
+      ok,
+    );
+  });
+
+  it('is idempotent — never appends the notice twice', () => {
+    const once = applyPhantomNotificationGuard(deadEnd, {
+      hasActiveWatcher: false,
+    });
+    const twice = applyPhantomNotificationGuard(once, {
+      hasActiveWatcher: false,
+    });
+    expect(twice).toBe(once);
+  });
+});