test(heartbeat): verify failure alerts re-fire after cooldown window

docs/plans/state.json

@@ -3497,7 +3497,7 @@
     }
   },
   "overall_progress": {
-    "total_test_count": 1866,
+    "total_test_count": 1867,
     "all_tests_passing": true,
     "p0_completion": "3/3 (100%)",
     "p1_completion": "4/4 (100%)",

src/automation/heartbeat.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, vi, afterEach } from 'vitest';
+import { describe, it, expect, vi, afterEach, beforeEach } from 'vitest';
 import { HeartbeatMonitor, parseInterval } from './heartbeat.js';
 import type { HeartbeatDeps } from './heartbeat.js';
 import type { HeartbeatConfig } from '../config/schema.js';
@@ -84,9 +84,15 @@ describe('parseInterval', () => {
 
 describe('HeartbeatMonitor', () => {
   let monitor: HeartbeatMonitor;
+  let nowSpy: ReturnType<typeof vi.spyOn> | undefined;
+
+  beforeEach(() => {
+    nowSpy = undefined;
+  });
 
   afterEach(() => {
     monitor?.stop();
+    nowSpy?.mockRestore();
   });
 
   it('start() does nothing when enabled: false', () => {
@@ -256,6 +262,51 @@ describe('HeartbeatMonitor', () => {
     expect(mockSend).toHaveBeenCalledTimes(2);
   });
 
+  it('sends failure notification again after notify cooldown elapses', async () => {
+    const mockSend = vi.fn().mockResolvedValue(undefined);
+    const mockGet = vi.fn().mockReturnValue({ send: mockSend });
+
+    const deps = makeDeps({
+      config: makeConfig({
+        checks: ['model'],
+        failure_threshold: 1,
+        notify_cooldown: '1h',
+        notify: { channel: 'telegram', peer: '123' },
+      }),
+      modelRouter: undefined,
+      channelLookup: { get: mockGet },
+    });
+    monitor = new HeartbeatMonitor(deps);
+
+    let mockNow = 0;
+    nowSpy = vi.spyOn(Date, 'now').mockImplementation(() => mockNow);
+
+    await monitor.runChecks();
+    expect(mockSend).toHaveBeenCalledTimes(1);
+
+    mockNow = 1000;
+    Object.assign(deps, { modelRouter: { getTier: () => 'default' } });
+    await monitor.runChecks();
+    expect(mockSend).toHaveBeenCalledTimes(1);
+
+    mockNow = 2000;
+    Object.assign(deps, { modelRouter: undefined });
+    await monitor.runChecks();
+    expect(mockSend).toHaveBeenCalledTimes(1);
+
+    mockNow = 3600001;
+    Object.assign(deps, { modelRouter: { getTier: () => 'default' } });
+    await monitor.runChecks();
+
+    mockNow = 3600002;
+    Object.assign(deps, { modelRouter: undefined });
+    await monitor.runChecks();
+    expect(mockSend).toHaveBeenCalledTimes(2);
+    expect(mockSend).toHaveBeenLastCalledWith('123', expect.objectContaining({
+      text: expect.stringContaining('FAILING'),
+    }));
+  });
+
   it('recovery notification sent when checks pass after failures', async () => {
     const mockSend = vi.fn().mockResolvedValue(undefined);
     const mockGet = vi.fn().mockReturnValue({ send: mockSend });