diff --git a/backend/src/lib/webhook-subscriber.test.ts b/backend/src/lib/webhook-subscriber.test.ts
new file mode 100644
index 0000000..aa5454a
--- /dev/null
+++ b/backend/src/lib/webhook-subscriber.test.ts
@@ -0,0 +1,79 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+
+const { dispatchToTargetsMock } = vi.hoisted(() => ({
+  dispatchToTargetsMock: vi.fn(async () => []),
+}));
+
+vi.mock('@bytelyst/webhook-dispatch', () => ({
+  dispatchToTargets: dispatchToTargetsMock,
+}));
+
+import { _resetEventBus, getEventBus } from './event-bus.js';
+import {
+  _resetWebhookSubscriberForTests,
+  initWebhookSubscriber,
+  isWebhookSubscriberRunning,
+  registerWebhookTarget,
+  stopWebhookSubscriber,
+} from './webhook-subscriber.js';
+
+describe('webhook subscriber lifecycle', () => {
+  beforeEach(() => {
+    _resetWebhookSubscriberForTests();
+    _resetEventBus();
+    dispatchToTargetsMock.mockClear();
+  });
+
+  it('does not subscribe until initialized', async () => {
+    registerWebhookTarget({
+      id: 'target-1',
+      url: 'https://example.com/webhook',
+      secret: 'secret',
+      events: ['note.created'],
+      enabled: true,
+    });
+
+    await getEventBus().emit('note.created', {
+      noteId: 'note-1',
+      workspaceId: 'ws-1',
+      userId: 'user-1',
+      title: 'Created',
+    });
+
+    expect(isWebhookSubscriberRunning()).toBe(false);
+    expect(dispatchToTargetsMock).not.toHaveBeenCalled();
+  });
+
+  it('initializes idempotently and unsubscribes on stop', async () => {
+    registerWebhookTarget({
+      id: 'target-1',
+      url: 'https://example.com/webhook',
+      secret: 'secret',
+      events: ['note.created'],
+      enabled: true,
+    });
+
+    initWebhookSubscriber();
+    initWebhookSubscriber();
+    expect(isWebhookSubscriberRunning()).toBe(true);
+
+    await getEventBus().emit('note.created', {
+      noteId: 'note-1',
+      workspaceId: 'ws-1',
+      userId: 'user-1',
+      title: 'Created',
+    });
+    expect(dispatchToTargetsMock).toHaveBeenCalledTimes(1);
+
+    stopWebhookSubscriber();
+    expect(isWebhookSubscriberRunning()).toBe(false);
+
+    await getEventBus().emit('note.created', {
+      noteId: 'note-2',
+      workspaceId: 'ws-1',
+      userId: 'user-1',
+      title: 'Created again',
+    });
+    expect(dispatchToTargetsMock).toHaveBeenCalledTimes(1);
+  });
+});
diff --git a/backend/src/lib/webhook-subscriber.ts b/backend/src/lib/webhook-subscriber.ts
index 4978f92..37e138d 100644
--- a/backend/src/lib/webhook-subscriber.ts
+++ b/backend/src/lib/webhook-subscriber.ts
@@ -73,6 +73,8 @@ async function dispatchEvent<K extends keyof NoteLettEventMap>(
 const unsubscribers: (() => void)[] = [];
 
 export function initWebhookSubscriber(): void {
+  if (unsubscribers.length > 0) return;
+
   const bus = getEventBus();
 
   unsubscribers.push(
@@ -84,7 +86,18 @@ export function initWebhookSubscriber(): void {
   );
 }
 
+export function isWebhookSubscriberRunning(): boolean {
+  return unsubscribers.length > 0;
+}
+
 export function stopWebhookSubscriber(): void {
   for (const unsub of unsubscribers) unsub();
   unsubscribers.length = 0;
 }
+
+/** @internal — for testing only. */
+export function _resetWebhookSubscriberForTests(): void {
+  stopWebhookSubscriber();
+  targets.length = 0;
+  deliveryLog = [];
+}
diff --git a/backend/src/modules/note-prompts/scheduler.test.ts b/backend/src/modules/note-prompts/scheduler.test.ts
index 20d8e35..d0b3dda 100644
--- a/backend/src/modules/note-prompts/scheduler.test.ts
+++ b/backend/src/modules/note-prompts/scheduler.test.ts
@@ -59,7 +59,12 @@ vi.mock('@bytelyst/llm', () => ({
 }));
 
 import { buildTestApp, resetMemoryDatastore } from '../../test-helpers.js';
-import { promptSchedulerRoutes } from './scheduler.js';
+import {
+  isSchedulerLoopRunning,
+  promptSchedulerRoutes,
+  startSchedulerLoop,
+  stopSchedulerLoop,
+} from './scheduler.js';
 import { notePromptRoutes } from './routes.js';
 import { noteRoutes } from '../notes/routes.js';
 import { upsertBuiltinTemplate } from './repository.js';
@@ -76,6 +81,7 @@ beforeAll(async () => {
 });
 
 afterAll(async () => {
+  stopSchedulerLoop();
   await app.close();
 });
 
@@ -410,3 +416,24 @@ describe('scheduler diagnostics', () => {
     expect(Array.isArray(body.nextRuns)).toBe(true);
   });
 });
+
+describe('scheduler lifecycle', () => {
+  beforeEach(() => {
+    stopSchedulerLoop();
+  });
+
+  it('does not start the scheduler loop when only routes are registered for tests', () => {
+    expect(isSchedulerLoopRunning()).toBe(false);
+  });
+
+  it('starts idempotently and stops cleanly', () => {
+    startSchedulerLoop(60_000);
+    expect(isSchedulerLoopRunning()).toBe(true);
+
+    startSchedulerLoop(60_000);
+    expect(isSchedulerLoopRunning()).toBe(true);
+
+    stopSchedulerLoop();
+    expect(isSchedulerLoopRunning()).toBe(false);
+  });
+});
diff --git a/backend/src/modules/note-prompts/scheduler.ts b/backend/src/modules/note-prompts/scheduler.ts
index 70e39b9..38378f3 100644
--- a/backend/src/modules/note-prompts/scheduler.ts
+++ b/backend/src/modules/note-prompts/scheduler.ts
@@ -243,6 +243,10 @@ export function startSchedulerLoop(intervalMs = 60_000, logger?: SchedulerLogger
   }, intervalMs);
 }
 
+export function isSchedulerLoopRunning(): boolean {
+  return schedulerInterval !== null;
+}
+
 export function stopSchedulerLoop(): void {
   if (schedulerInterval) {
     clearInterval(schedulerInterval);
diff --git a/backend/src/server.test.ts b/backend/src/server.test.ts
index 0dfa822..e1cdde4 100644
--- a/backend/src/server.test.ts
+++ b/backend/src/server.test.ts
@@ -8,6 +8,8 @@ const initDatastoreMock = vi.fn(() => undefined);
 const diagnosticsRoutesMock = vi.fn(async () => undefined);
 const startSchedulerLoopMock = vi.fn();
 const stopSchedulerLoopMock = vi.fn();
+const initWebhookSubscriberMock = vi.fn();
+const stopWebhookSubscriberMock = vi.fn();
 
 const appMock = {
   register: vi.fn(async () => undefined),
@@ -74,6 +76,10 @@ vi.mock('./lib/request-context.js', () => ({
 vi.mock('./lib/feature-flags.js', () => ({ getAllFlags: vi.fn(() => ({})) }));
 vi.mock('./lib/telemetry.js', () => ({ getBufferedEvents: vi.fn(() => []), flushEvents: vi.fn(() => []) }));
 vi.mock('./lib/diagnostics-routes.js', () => ({ diagnosticsRoutes: diagnosticsRoutesMock }));
+vi.mock('./lib/webhook-subscriber.js', () => ({
+  initWebhookSubscriber: initWebhookSubscriberMock,
+  stopWebhookSubscriber: stopWebhookSubscriberMock,
+}));
 vi.mock('./modules/note-shares/repository.js', () => ({ findShareByToken: vi.fn(async () => null) }));
 vi.mock('./modules/notes/repository.js', () => ({ getNote: vi.fn(async () => null) }));
 
@@ -99,6 +105,13 @@ describe('server bootstrap', () => {
     expect(appMock.register).toHaveBeenCalledTimes(14);
     expect(diagnosticsRoutesMock).toHaveBeenCalledWith(appMock);
     expect(startSchedulerLoopMock).toHaveBeenCalledWith(60_000, appMock.log);
+    expect(initWebhookSubscriberMock).toHaveBeenCalledOnce();
+    expect(appMock.addHook).toHaveBeenCalledWith('onClose', expect.any(Function));
+    const onCloseHook = appMock.addHook.mock.calls.find(([event]) => event === 'onClose')?.[1];
+    expect(onCloseHook).toEqual(expect.any(Function));
+    await onCloseHook();
+    expect(stopSchedulerLoopMock).toHaveBeenCalledOnce();
+    expect(stopWebhookSubscriberMock).toHaveBeenCalledOnce();
     expect(startServiceMock).toHaveBeenCalledWith(appMock, { port: 4016, host: '0.0.0.0' });
   });
 });