diff --git a/server/src/nest/common/body-contract-allow-list.ts b/server/src/nest/common/body-contract-allow-list.ts
index b78611ed..6692a68d 100644
--- a/server/src/nest/common/body-contract-allow-list.ts
+++ b/server/src/nest/common/body-contract-allow-list.ts
@@ -54,11 +54,6 @@ export const BODY_CONTRACT_ALLOW_LIST: string[] = [
   'JourneyController.uploadEntryPhotos',
   'JourneyController.uploadGalleryVideo',
   'LlmLocalController.pull',
-  'NotificationsController.respond',
-  'NotificationsController.setPreferences',
-  'NotificationsController.testNtfy',
-  'NotificationsController.testSmtp',
-  'NotificationsController.testWebhook',
   'OauthApiController.authorize',
   'OauthApiController.createClient',
   'PluginRoutesController.route',
diff --git a/server/src/nest/notifications/notifications.controller.ts b/server/src/nest/notifications/notifications.controller.ts
index eeae8f70..63a48790 100644
--- a/server/src/nest/notifications/notifications.controller.ts
+++ b/server/src/nest/notifications/notifications.controller.ts
@@ -14,6 +14,13 @@ import {
 import type { ChannelTestResult, UnreadCountResult } from '@trek/shared';
 import type { User } from '../../types';
 import { NotificationsService } from './notifications.service';
+import {
+  PreferencesUpdateDto,
+  TestSmtpDto,
+  TestWebhookDto,
+  TestNtfyDto,
+  NotificationRespondDto,
+} from './notifications.dto';
 import { JwtAuthGuard } from '../auth/jwt-auth.guard';
 import { CurrentUser } from '../auth/current-user.decorator';
 
@@ -31,6 +38,10 @@ const MASKED = '••••••••';
  * codes. POSTs that answer with res.json stay 200 (Nest would default to 201).
  * The static /in-app/read-all and /in-app/all routes are declared before the
  * /in-app/:id routes so they win over the param, matching the legacy order.
+ * Bodies validate via notifications.dto.ts (@trek/shared schemas through the
+ * global ZodValidationPipe) — malformed bodies now get the pipe's standard
+ * { error: 'field: message; …' } envelope instead of the old inline checks
+ * (the sanctioned ratchet behavior); valid bodies behave byte-identically.
  */
 @Controller('api/notifications')
 @UseGuards(JwtAuthGuard)
@@ -43,24 +54,24 @@ export class NotificationsController {
   }
 
   @Put('preferences')
-  setPreferences(@CurrentUser() user: User, @Body() body: Record<string, Record<string, boolean>>) {
+  setPreferences(@CurrentUser() user: User, @Body() body: PreferencesUpdateDto) {
     this.notifications.setPreferences(user.id, body);
     return this.notifications.getPreferences(user.id, user.role);
   }
 
   @Post('test-smtp')
   @HttpCode(200)
-  async testSmtp(@CurrentUser() user: User, @Body('email') email?: string): Promise<ChannelTestResult> {
+  async testSmtp(@CurrentUser() user: User, @Body() body: TestSmtpDto): Promise<ChannelTestResult> {
     if (user.role !== 'admin') {
       throw new HttpException({ error: 'Admin only' }, 403);
     }
-    return this.notifications.testSmtp(email || user.email);
+    return this.notifications.testSmtp(body.email || user.email);
   }
 
   @Post('test-webhook')
   @HttpCode(200)
-  async testWebhook(@CurrentUser() user: User, @Body('url') urlInput?: unknown): Promise<ChannelTestResult> {
-    let url = urlInput;
+  async testWebhook(@CurrentUser() user: User, @Body() body: TestWebhookDto): Promise<ChannelTestResult> {
+    let url: string | null | undefined = body.url;
     if (!url || url === MASKED) {
       url = this.notifications.userWebhookUrl(user.id);
       if (!url && user.role === 'admin') url = this.notifications.adminWebhookUrl();
@@ -68,9 +79,6 @@ export class NotificationsController {
         throw new HttpException({ error: 'No webhook URL configured' }, 400);
       }
     }
-    if (typeof url !== 'string') {
-      throw new HttpException({ error: 'url must be a string' }, 400);
-    }
     try {
       new URL(url);
     } catch {
@@ -81,12 +89,8 @@ export class NotificationsController {
 
   @Post('test-ntfy')
   @HttpCode(200)
-  async testNtfy(
-    @CurrentUser() user: User,
-    @Body('topic') topic?: string,
-    @Body('server') server?: string,
-    @Body('token') token?: string,
-  ): Promise<ChannelTestResult> {
+  async testNtfy(@CurrentUser() user: User, @Body() body: TestNtfyDto): Promise<ChannelTestResult> {
+    const { topic, server, token } = body;
     const userCfg = this.notifications.userNtfyConfig(user.id);
     const adminCfg = this.notifications.adminNtfyConfig();
 
@@ -176,13 +180,10 @@ export class NotificationsController {
   async respond(
     @CurrentUser() user: User,
     @Param('id') idParam: string,
-    @Body('response') response?: unknown,
+    @Body() body: NotificationRespondDto,
   ): Promise<{ success: boolean; notification: unknown }> {
     const id = this.parseId(idParam);
-    if (response !== 'positive' && response !== 'negative') {
-      throw new HttpException({ error: 'response must be "positive" or "negative"' }, 400);
-    }
-    const result = await this.notifications.respond(id, user.id, response);
+    const result = await this.notifications.respond(id, user.id, body.response);
     if (!result.success) {
       throw new HttpException({ error: result.error }, 400);
     }
diff --git a/server/src/nest/notifications/notifications.dto.ts b/server/src/nest/notifications/notifications.dto.ts
new file mode 100644
index 00000000..cdce0d64
--- /dev/null
+++ b/server/src/nest/notifications/notifications.dto.ts
@@ -0,0 +1,21 @@
+import { createZodDto } from 'nestjs-zod';
+import {
+  preferencesUpdateRequestSchema,
+  testSmtpRequestSchema,
+  testWebhookRequestSchema,
+  testNtfyRequestSchema,
+  notificationRespondRequestSchema,
+} from '@trek/shared';
+
+/**
+ * Server-side createZodDto wrappers over the @trek/shared notification
+ * contracts. The global ZodValidationPipe (APP_PIPE in app.module.ts)
+ * validates any @Body() parameter typed with one of these classes by
+ * metatype — the Zod schemas in shared/ remain the single source of truth
+ * for the wire contract.
+ */
+export class PreferencesUpdateDto extends createZodDto(preferencesUpdateRequestSchema) {}
+export class TestSmtpDto extends createZodDto(testSmtpRequestSchema) {}
+export class TestWebhookDto extends createZodDto(testWebhookRequestSchema) {}
+export class TestNtfyDto extends createZodDto(testNtfyRequestSchema) {}
+export class NotificationRespondDto extends createZodDto(notificationRespondRequestSchema) {}
diff --git a/server/tests/integration/notifications.test.ts b/server/tests/integration/notifications.test.ts
index 1dc5ade5..0a469852 100644
--- a/server/tests/integration/notifications.test.ts
+++ b/server/tests/integration/notifications.test.ts
@@ -95,10 +95,13 @@ describe('Notification preferences', () => {
   it('NOTIF-001 — PUT /api/notifications/preferences updates settings', async () => {
     const { user } = createUser(testDb);
 
+    // The DTO ratchet enforces the matrix shape the client actually sends
+    // ({ event: { channel: enabled } }); the pre-matrix flat notify_* body
+    // this case used to send is rejected by the pipe now.
     const res = await request(app)
       .put('/api/notifications/preferences')
       .set('Cookie', authCookie(user.id))
-      .send({ notify_trip_invite: true, notify_booking_change: false });
+      .send({ trip_invite: { email: true }, booking_change: { email: false } });
     expect(res.status).toBe(200);
     expect(res.body).toHaveProperty('preferences');
   });
@@ -310,9 +313,13 @@ describe('Notification test endpoints', () => {
   it('NOTIF-005 — POST /api/notifications/test-smtp requires admin', async () => {
     const { user } = createUser(testDb);
 
+    // Send the empty JSON body the client sends ({ email: undefined } →
+    // {}): a completely body-less POST has no content-type, so the DTO pipe
+    // rejects it before the admin gate since the ratchet.
     const res = await request(app)
       .post('/api/notifications/test-smtp')
-      .set('Cookie', authCookie(user.id));
+      .set('Cookie', authCookie(user.id))
+      .send({});
     // Non-admin gets 403
     expect(res.status).toBe(403);
   });
diff --git a/server/tests/unit/nest/notifications.controller.test.ts b/server/tests/unit/nest/notifications.controller.test.ts
index d96bbed6..f037db0d 100644
--- a/server/tests/unit/nest/notifications.controller.test.ts
+++ b/server/tests/unit/nest/notifications.controller.test.ts
@@ -1,6 +1,7 @@
 import { describe, it, expect, vi } from 'vitest';
 import { HttpException } from '@nestjs/common';
 import { NotificationsController } from '../../../src/nest/notifications/notifications.controller';
+import { NotificationRespondDto } from '../../../src/nest/notifications/notifications.dto';
 import type { NotificationsService } from '../../../src/nest/notifications/notifications.service';
 import type { User } from '../../../src/types';
 
@@ -43,7 +44,7 @@ describe('NotificationsController (parity with the legacy /api/notifications rou
   describe('test-smtp', () => {
     it('403 { error: Admin only } for a non-admin (distinct from AdminGuard wording)', async () => {
       const testSmtp = vi.fn();
-      expect(await thrown(() => makeController({ testSmtp }).testSmtp(user))).toEqual({
+      expect(await thrown(() => makeController({ testSmtp }).testSmtp(user, {}))).toEqual({
         status: 403, body: { error: 'Admin only' },
       });
       expect(testSmtp).not.toHaveBeenCalled();
@@ -51,7 +52,7 @@ describe('NotificationsController (parity with the legacy /api/notifications rou
 
     it('falls back to the admin\'s own email when none given', async () => {
       const testSmtp = vi.fn().mockResolvedValue({ success: true });
-      await makeController({ testSmtp }).testSmtp(admin);
+      await makeController({ testSmtp }).testSmtp(admin, {});
       expect(testSmtp).toHaveBeenCalledWith('admin@example.test');
     });
   });
@@ -59,27 +60,27 @@ describe('NotificationsController (parity with the legacy /api/notifications rou
   describe('test-webhook', () => {
     it('uses the provided url', async () => {
       const testWebhook = vi.fn().mockResolvedValue({ success: true });
-      await makeController({ testWebhook }).testWebhook(user, 'https://hooks.example/x');
+      await makeController({ testWebhook }).testWebhook(user, { url: 'https://hooks.example/x' });
       expect(testWebhook).toHaveBeenCalledWith('https://hooks.example/x');
     });
 
     it('falls back to the saved user url when the masked placeholder is sent', async () => {
       const testWebhook = vi.fn().mockResolvedValue({ success: true });
       const userWebhookUrl = vi.fn().mockReturnValue('https://saved.example/u');
-      await makeController({ testWebhook, userWebhookUrl }).testWebhook(user, MASKED);
+      await makeController({ testWebhook, userWebhookUrl }).testWebhook(user, { url: MASKED });
       expect(userWebhookUrl).toHaveBeenCalledWith(4);
       expect(testWebhook).toHaveBeenCalledWith('https://saved.example/u');
     });
 
     it('400 when no url is configured', async () => {
       const userWebhookUrl = vi.fn().mockReturnValue(null);
-      expect(await thrown(() => makeController({ userWebhookUrl }).testWebhook(user, undefined))).toEqual({
+      expect(await thrown(() => makeController({ userWebhookUrl }).testWebhook(user, {}))).toEqual({
         status: 400, body: { error: 'No webhook URL configured' },
       });
     });
 
     it('400 on an invalid url', async () => {
-      expect(await thrown(() => makeController({}).testWebhook(user, 'not a url'))).toEqual({
+      expect(await thrown(() => makeController({}).testWebhook(user, { url: 'not a url' }))).toEqual({
         status: 400, body: { error: 'Invalid URL' },
       });
     });
@@ -89,7 +90,7 @@ describe('NotificationsController (parity with the legacy /api/notifications rou
     it('400 when no topic can be resolved', async () => {
       const userNtfyConfig = vi.fn().mockReturnValue(null);
       const adminNtfyConfig = vi.fn().mockReturnValue({ server: null, token: null });
-      expect(await thrown(() => makeController({ userNtfyConfig, adminNtfyConfig }).testNtfy(user))).toEqual({
+      expect(await thrown(() => makeController({ userNtfyConfig, adminNtfyConfig }).testNtfy(user, {}))).toEqual({
         status: 400, body: { error: 'No ntfy topic configured' },
       });
     });
@@ -98,7 +99,7 @@ describe('NotificationsController (parity with the legacy /api/notifications rou
       const testNtfy = vi.fn().mockResolvedValue({ success: true });
       const userNtfyConfig = vi.fn().mockReturnValue({ topic: 'saved-topic', server: 'https://ntfy.me', token: 'saved-token' });
       const adminNtfyConfig = vi.fn().mockReturnValue({ server: null, token: null });
-      await makeController({ testNtfy, userNtfyConfig, adminNtfyConfig }).testNtfy(user, undefined, undefined, MASKED);
+      await makeController({ testNtfy, userNtfyConfig, adminNtfyConfig }).testNtfy(user, { token: MASKED });
       expect(testNtfy).toHaveBeenCalledWith({ topic: 'saved-topic', server: 'https://ntfy.me', token: 'saved-token' });
     });
   });
@@ -159,22 +160,24 @@ describe('NotificationsController (parity with the legacy /api/notifications rou
   });
 
   describe('respond', () => {
-    it('400 on an invalid response value', async () => {
-      expect(await thrown(() => makeController({}).respond(user, '5', 'maybe'))).toEqual({
-        status: 400, body: { error: 'response must be "positive" or "negative"' },
-      });
+    it('rejects an invalid response value at the contract (ZodValidationPipe owns the 400 now)', () => {
+      // The inline enum check died with the DTO ratchet: over HTTP the global
+      // pipe rejects the body before the handler runs, with the standard
+      // { error: 'field: message; …' } envelope.
+      expect(NotificationRespondDto.schema.safeParse({ response: 'maybe' }).success).toBe(false);
+      expect(NotificationRespondDto.schema.safeParse({ response: 'positive' }).success).toBe(true);
     });
 
     it('400 with the service error when the response fails', async () => {
       const respond = vi.fn().mockResolvedValue({ success: false, error: 'Already responded' });
-      expect(await thrown(() => makeController({ respond }).respond(user, '5', 'positive'))).toEqual({
+      expect(await thrown(() => makeController({ respond }).respond(user, '5', { response: 'positive' }))).toEqual({
         status: 400, body: { error: 'Already responded' },
       });
     });
 
     it('returns success + the updated notification', async () => {
       const respond = vi.fn().mockResolvedValue({ success: true, notification: { id: 5, response: 'positive' } });
-      expect(await makeController({ respond }).respond(user, '5', 'positive')).toEqual({
+      expect(await makeController({ respond }).respond(user, '5', { response: 'positive' })).toEqual({
         success: true, notification: { id: 5, response: 'positive' },
       });
       expect(respond).toHaveBeenCalledWith(5, 4, 'positive');
diff --git a/shared/src/notification/notification.schema.spec.ts b/shared/src/notification/notification.schema.spec.ts
index 7d4d7d68..5aa3b8b2 100644
--- a/shared/src/notification/notification.schema.spec.ts
+++ b/shared/src/notification/notification.schema.spec.ts
@@ -3,6 +3,7 @@ import {
   notificationRespondRequestSchema,
   channelTestResultSchema,
   inAppListResultSchema,
+  testNtfyRequestSchema,
 } from './notification.schema';
 
 import { describe, it, expect } from 'vitest';
@@ -29,6 +30,14 @@ describe('notificationRespondRequestSchema', () => {
   });
 });
 
+describe('testNtfyRequestSchema', () => {
+  it('accepts null server/token — the client sends null to mean "use the saved value"', () => {
+    expect(testNtfyRequestSchema.safeParse({ topic: 't', server: null, token: null }).success).toBe(true);
+    expect(testNtfyRequestSchema.safeParse({}).success).toBe(true);
+    expect(testNtfyRequestSchema.safeParse({ topic: 1 }).success).toBe(false);
+  });
+});
+
 describe('channelTestResultSchema', () => {
   it('accepts a success result and an error result', () => {
     expect(channelTestResultSchema.safeParse({ success: true }).success).toBe(true);
diff --git a/shared/src/notification/notification.schema.ts b/shared/src/notification/notification.schema.ts
index b0b295fc..91a7dc4c 100644
--- a/shared/src/notification/notification.schema.ts
+++ b/shared/src/notification/notification.schema.ts
@@ -21,10 +21,13 @@ export const testSmtpRequestSchema = z.object({ email: z.string().optional() });
 export const testWebhookRequestSchema = z.object({
   url: z.string().optional(),
 });
+// server/token are nullable: the client deliberately sends null to mean
+// "fall back to the saved value" (a stored token is only masked in the
+// placeholder — sending null keeps the saved one).
 export const testNtfyRequestSchema = z.object({
   topic: z.string().optional(),
-  server: z.string().optional(),
-  token: z.string().optional(),
+  server: z.string().nullable().optional(),
+  token: z.string().nullable().optional(),
 });
 
 /** Result of a channel test ping. */