diff --git a/server/scripts/tx-writes-baseline.json b/server/scripts/tx-writes-baseline.json
index dcb76f5f1..91f80552f 100644
--- a/server/scripts/tx-writes-baseline.json
+++ b/server/scripts/tx-writes-baseline.json
@@ -28,7 +28,6 @@
   "src/nest/integrations/airtrail-link.service.ts#AirtrailLinkService.pushReservationToAirtrail": 2,
   "src/nest/integrations/airtrail-sync.service.ts#AirtrailSyncService.runAirtrailSync": 2,
   "src/nest/integrations/airtrail-sync.service.ts#AirtrailSyncService.syncOwner": 8,
-  "src/nest/integrations/airtrail.service.ts#AirtrailService.saveSettings": 2,
   "src/nest/integrations/dawarich-sync.service.ts#DawarichSyncService.runSync": 2,
   "src/nest/integrations/dawarich-sync.service.ts#DawarichSyncService.syncTripWindow": 3,
   "src/nest/integrations/dawarich-sync.service.ts#DawarichSyncService.syncUserOnce": 3,
diff --git a/server/src/nest/integrations/airtrail.service.ts b/server/src/nest/integrations/airtrail.service.ts
index adb97c8b5..a8328be79 100644
--- a/server/src/nest/integrations/airtrail.service.ts
+++ b/server/src/nest/integrations/airtrail.service.ts
@@ -2,6 +2,7 @@ import { UserAirtrailRepository } from '../../db/repositories/UserAirtrail.repos
 import { checkSsrf } from '../../utils/ssrfGuard';
 import { AuditService } from '../audit/audit.service';
 import { maybe_encrypt_api_key, decrypt_api_key } from '../common/crypto/apiKeyCrypto';
+import { UnitOfWork } from '../database/unit-of-work';
 import { AirtrailAuthError, AirtrailRequestError, type AirtrailCreds } from './airtrail.client';
 import { AirtrailClient } from './airtrail.client';
 import { normalizeFlight } from './airtrail.mapper';
@@ -34,10 +35,9 @@ interface UserConnRow {
  * `UserAirtrailRepository`'s (same `users` table) `getAirtrailConnRow`/`getAirtrailWriteEnabled`/
  * `setAirtrailSettingsWithKey`/`setAirtrailSettings`/`clearAirtrailApiKey`
  * methods (R7 — the repository sees only opaque, already-encrypted TEXT;
- * `maybe_encrypt_api_key`/`decrypt_api_key` stay here). `saveSettings` keeps
- * its pre-existing asymmetry with `DawarichService#saveSettings`
- * (Task 3): Dawarich wraps its writes in `uow.transactional`, this one does
- * not — preserved exactly, not "fixed" to match.
+ * `maybe_encrypt_api_key`/`decrypt_api_key` stay here). `saveSettings` writes
+ * in one `uow.transactional`, as `DawarichService#saveSettings` does: the new
+ * address and the key it may no longer carry change together or not at all.
  */
 @Injectable()
 export class AirtrailService {
@@ -45,6 +45,7 @@ export class AirtrailService {
     private readonly airtrailRepo: UserAirtrailRepository,
     private readonly audit: AuditService,
     private readonly client: AirtrailClient,
+    private readonly uow: UnitOfWork,
   ) {}
 
   private async readRow(userId: number): Promise<UserConnRow | undefined> {
@@ -122,34 +123,32 @@ export class AirtrailService {
     // A key belongs to the instance it was issued on, as in testConnection. A
     // new host with the key field left masked or blank would otherwise send the
     // old instance's key to the new one on the next sync, so the key goes with
-    // the host. A path edit on the same origin keeps it. The key is cleared
-    // before the new address is written, so no moment stores the new address
-    // beside the old key.
-    if (newKey === undefined) {
-      const previousUrl = (await this.readRow(userId))?.airtrail_url ?? null;
-      if (movedHost(previousUrl, trimmedUrl)) await this.airtrailRepo.clearAirtrailApiKey(userId);
-    }
+    // the host. A path edit on the same origin keeps it. An address cleared with
+    // no key left drops the key too: it would be a credential for no server.
+    const previousUrl = newKey === undefined ? ((await this.readRow(userId))?.airtrail_url ?? null) : null;
+    const dropKey = newKey === undefined && (!trimmedUrl || movedHost(previousUrl, trimmedUrl));
 
-    if (newKey !== undefined) {
-      await this.airtrailRepo.setAirtrailSettingsWithKey(
-        userId,
-        trimmedUrl || null,
-        newKey,
-        allowInsecureTls ? 1 : 0,
-        writeEnabled ? 1 : 0,
-      );
-    } else {
+    // The address and the key it may no longer carry change together, so no
+    // moment stores the new address beside the old key.
+    await this.uow.transactional(async () => {
+      if (newKey !== undefined) {
+        await this.airtrailRepo.setAirtrailSettingsWithKey(
+          userId,
+          trimmedUrl || null,
+          newKey,
+          allowInsecureTls ? 1 : 0,
+          writeEnabled ? 1 : 0,
+        );
+        return;
+      }
       await this.airtrailRepo.setAirtrailSettings(
         userId,
         trimmedUrl || null,
         allowInsecureTls ? 1 : 0,
         writeEnabled ? 1 : 0,
       );
-      // Clearing the URL with no key left makes the connection meaningless — drop the key too.
-      if (!trimmedUrl) {
-        await this.airtrailRepo.clearAirtrailApiKey(userId);
-      }
-    }
+      if (dropKey) await this.airtrailRepo.clearAirtrailApiKey(userId);
+    });
 
     return { success: true, warning };
   }
diff --git a/server/tests/unit/nest/airtrail.service.test.ts b/server/tests/unit/nest/airtrail.service.test.ts
index f6aee5a47..b56a43d99 100644
--- a/server/tests/unit/nest/airtrail.service.test.ts
+++ b/server/tests/unit/nest/airtrail.service.test.ts
@@ -17,6 +17,7 @@ import { Users } from '../../../src/db/entities/Users.entity';
 import { UserAirtrailRepository } from '../../../src/db/repositories/UserAirtrail.repository';
 import type { UsersRepository } from '../../../src/db/repositories/Users.repository';
 import { AuditService } from '../../../src/nest/audit/audit.service';
+import { UnitOfWork } from '../../../src/nest/database/unit-of-work';
 import type { AirtrailClient } from '../../../src/nest/integrations/airtrail.client';
 import { AirtrailService } from '../../../src/nest/integrations/airtrail.service';
 import { createSnapshotTestDb } from '../../helpers/db-mock';
@@ -42,9 +43,14 @@ const listFlights = vi.fn();
 beforeAll(async () => {
   t = await createTestOrm(testDb);
   usersRepo = t.repo(Users);
-  svc = new AirtrailService(new UserAirtrailRepository(t.orm.em), new AuditService(t.repo(AuditLog), usersRepo), {
-    listFlights,
-  } as unknown as AirtrailClient);
+  svc = new AirtrailService(
+    new UserAirtrailRepository(t.orm.em),
+    new AuditService(t.repo(AuditLog), usersRepo),
+    {
+      listFlights,
+    } as unknown as AirtrailClient,
+    new UnitOfWork(t.orm.em),
+  );
 });
 beforeEach(() => {
   resetTestDb(testDb);
diff --git a/server/tests/unit/nest/integrations/airtrailTestConnection.test.ts b/server/tests/unit/nest/integrations/airtrailTestConnection.test.ts
index f250ba71f..a6af90477 100644
--- a/server/tests/unit/nest/integrations/airtrailTestConnection.test.ts
+++ b/server/tests/unit/nest/integrations/airtrailTestConnection.test.ts
@@ -3,6 +3,7 @@ import { AuditLog } from '../../../../src/db/entities/AuditLog.entity';
 import { Users } from '../../../../src/db/entities/Users.entity';
 import { UserAirtrailRepository } from '../../../../src/db/repositories/UserAirtrail.repository';
 import { AuditService } from '../../../../src/nest/audit/audit.service';
+import { UnitOfWork } from '../../../../src/nest/database/unit-of-work';
 import type { AirtrailClient } from '../../../../src/nest/integrations/airtrail.client';
 import { AirtrailService } from '../../../../src/nest/integrations/airtrail.service';
 import { createUser } from '../../../helpers/factories';
@@ -24,9 +25,14 @@ let t: TestOrm;
 
 beforeAll(async () => {
   t = await createTestOrm(db);
-  svc = new AirtrailService(new UserAirtrailRepository(t.orm.em), new AuditService(t.repo(AuditLog), t.repo(Users)), {
-    listFlights,
-  } as unknown as AirtrailClient);
+  svc = new AirtrailService(
+    new UserAirtrailRepository(t.orm.em),
+    new AuditService(t.repo(AuditLog), t.repo(Users)),
+    {
+      listFlights,
+    } as unknown as AirtrailClient,
+    new UnitOfWork(t.orm.em),
+  );
 });
 
 afterAll(async () => {
diff --git a/server/tests/unit/nest/integrations/airtrailWriteback.test.ts b/server/tests/unit/nest/integrations/airtrailWriteback.test.ts
index 18c69d21f..9c8f3b24b 100644
--- a/server/tests/unit/nest/integrations/airtrailWriteback.test.ts
+++ b/server/tests/unit/nest/integrations/airtrailWriteback.test.ts
@@ -10,6 +10,7 @@ import { AuditLog } from '../../../../src/db/entities/AuditLog.entity';
 import { Users } from '../../../../src/db/entities/Users.entity';
 import { UserAirtrailRepository } from '../../../../src/db/repositories/UserAirtrail.repository';
 import { AuditService } from '../../../../src/nest/audit/audit.service';
+import { UnitOfWork } from '../../../../src/nest/database/unit-of-work';
 import { AirtrailClient } from '../../../../src/nest/integrations/airtrail.client';
 import { AirtrailService } from '../../../../src/nest/integrations/airtrail.service';
 import { createUser } from '../../../helpers/factories';
@@ -39,6 +40,7 @@ beforeAll(async () => {
     new UserAirtrailRepository(t.orm.em),
     new AuditService(t.repo(AuditLog), t.repo(Users)),
     new AirtrailClient(),
+    new UnitOfWork(t.orm.em),
   );
   getConnectionSettings = (...args) => svc.getConnectionSettings(...args);
   isAirtrailWriteEnabled = (...args) => svc.isAirtrailWriteEnabled(...args);
@@ -72,45 +74,32 @@ describe('airtrail writeback opt-in persistence (#1240)', () => {
   });
 });
 
-describe('airtrail saveSettings preserves its pre-existing NO-transaction asymmetry with Dawarich (Plan 3h Task 4, R7/Risks)', () => {
-  it('ATC-TX-001: AirtrailService is constructed with no UnitOfWork at all — saveSettings has nothing to wrap its writes in', () => {
-    // `DawarichService#saveSettings`'s equivalent DOES take a `UnitOfWork` and
-    // wraps its writes in `uow.transactional`; AirtrailService's own
-    // constructor (`UserAirtrailRepository`, `AuditService`, `AirtrailClient`) never
-    // gained one during the Plan 3h Task 4 conversion — a structural
-    // guarantee that a future edit re-introducing a transactional wrap here
-    // would have to ALSO add a new constructor param to do it, not just
-    // touch `saveSettings`'s body.
+describe('airtrail saveSettings writes in one transaction, as Dawarich does', () => {
+  it('ATC-TX-001: AirtrailService is constructed with a UnitOfWork to wrap its writes in', () => {
     const paramTypes = Reflect.getMetadata('design:paramtypes', AirtrailService) as unknown[] | undefined;
-    expect(paramTypes).toBeDefined();
-    expect(paramTypes!.map((p) => (p as { name?: string })?.name)).toEqual([
+    expect(paramTypes?.map((p) => (p as { name?: string })?.name)).toEqual([
       'UserAirtrailRepository',
       'AuditService',
       'AirtrailClient',
+      'UnitOfWork',
     ]);
   });
 
-  it('ATC-TX-002: the URL-cleared branch performs its two writes as genuinely separate repository calls, not one atomic statement', async () => {
+  it('ATC-TX-002: clearing the URL drops the key inside the same transaction as the address write', async () => {
     const { user } = createUser(db);
     await saveSettings(user.id, 'https://at.example.com', 'secret-key', false, false, null);
 
-    const airtrailRepo = (svc as unknown as { airtrailRepo: UserAirtrailRepository }).airtrailRepo;
-    const setSpy = vi.spyOn(airtrailRepo, 'setAirtrailSettings');
-    const clearSpy = vi.spyOn(airtrailRepo, 'clearAirtrailApiKey');
+    const inner = svc as unknown as { airtrailRepo: UserAirtrailRepository; uow: UnitOfWork };
+    const txSpy = vi.spyOn(inner.uow, 'transactional');
+    const setSpy = vi.spyOn(inner.airtrailRepo, 'setAirtrailSettings');
+    const clearSpy = vi.spyOn(inner.airtrailRepo, 'clearAirtrailApiKey');
     try {
-      // Clearing the URL with no key left drops the key too (ATC4 then ATC5) —
-      // TWO independent nativeUpdate calls, not a single transactional unit.
       await saveSettings(user.id, '', undefined, false, false, null);
+      expect(txSpy).toHaveBeenCalledTimes(1);
       expect(setSpy).toHaveBeenCalledTimes(1);
       expect(clearSpy).toHaveBeenCalledTimes(1);
-      // clearAirtrailApiKey only runs AFTER setAirtrailSettings's own write
-      // resolved (sequential awaits in the service body, never Promise.all
-      // or a single wrapped call) — the same "report, don't fix" asymmetry
-      // the plan's Risks section flags.
-      const setOrder = setSpy.mock.invocationCallOrder[0];
-      const clearOrder = clearSpy.mock.invocationCallOrder[0];
-      expect(clearOrder).toBeGreaterThan(setOrder);
     } finally {
+      txSpy.mockRestore();
       setSpy.mockRestore();
       clearSpy.mockRestore();
     }