event-based cancellation

wire hash cancellation

await cleanup

remove forced kill

add regression tests

abort sync requests

fix cleanup ordering in teardown

exit isolate

test background sync

test sigabrt crash

cleanup

mobile/integration_test/background_sync_teardown_test.dart

@@ -0,0 +1,154 @@
+import 'dart:async';
+
+import 'package:drift/drift.dart' show Value;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:immich_mobile/domain/models/store.model.dart';
+import 'package:immich_mobile/domain/utils/background_sync.dart';
+import 'package:immich_mobile/entities/store.entity.dart';
+import 'package:immich_mobile/infrastructure/entities/user.entity.drift.dart';
+import 'package:immich_mobile/infrastructure/repositories/db.repository.dart';
+import 'package:immich_mobile/main.dart' as app;
+import 'package:immich_mobile/services/api.service.dart';
+import 'package:immich_mobile/utils/bootstrap.dart';
+import 'package:immich_mobile/wm_executor.dart';
+import 'package:integration_test/integration_test.dart';
+import 'package:openapi/api.dart';
+
+import 'test_utils/fake_immich_server.dart';
+
+void main() {
+  final binding = IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+  // These tests do real I/O without pumping a widget tree, so disable the fake async clock
+  binding.framePolicy = LiveTestWidgetsFlutterBindingFramePolicy.fullyLive;
+
+  late Drift drift;
+  late FakeImmichServer server;
+
+  setUpAll(() async {
+    await app.initApp();
+    (drift, _) = await Bootstrap.initDomain();
+  });
+
+  setUp(() async {
+    await workerManagerPatch.init(dynamicSpawning: true);
+    server = await FakeImmichServer.start();
+    await ApiService().resolveAndSetEndpoint(server.endpoint);
+    await drift.delete(drift.userEntity).go();
+    await Store.delete(StoreKey.syncMigrationStatus);
+  });
+
+  tearDown(() async {
+    await workerManagerPatch.dispose();
+    await server.close();
+    await Store.delete(StoreKey.serverEndpoint);
+    await Store.delete(StoreKey.syncMigrationStatus);
+  });
+
+  void sendUser(SyncStream stream, String id, String name) {
+    stream.send(
+      type: SyncEntityType.userV1.value,
+      data: SyncUserV1(
+        id: id,
+        name: name,
+        email: '$id@test.com',
+        hasProfileImage: false,
+        deletedAt: null,
+        profileChangedAt: DateTime.utc(2025),
+      ).toJson(),
+      ack: id,
+    );
+  }
+
+  Future<bool> dbReadable() async {
+    try {
+      await drift.customSelect('SELECT 1').get().timeout(const Duration(seconds: 5));
+      return true;
+    } catch (_) {
+      return false;
+    }
+  }
+
+  Future<int> userCount() async => (await drift.select(drift.userEntity).get()).length;
+
+  // Starts a remote sync and resolves once its /sync/stream request is open.
+  Future<(Future<bool>, SyncStream)> startSync() async {
+    final sync = BackgroundSyncManager().syncRemote();
+    final stream = await server.streamOpened.timeout(
+      const Duration(seconds: 30),
+      onTimeout: () => fail('sync isolate never opened /sync/stream'),
+    );
+    return (sync, stream);
+  }
+
+  testWidgets('a full sync ingests streamed events into the shared DB', (tester) async {
+    expect(await userCount(), 0);
+
+    final (sync, stream) = await startSync();
+
+    sendUser(stream, 'u1', 'Alice');
+    sendUser(stream, 'u2', 'Bob');
+    await stream.close();
+
+    final result = await sync.timeout(
+      const Duration(seconds: 30),
+      onTimeout: () => fail('sync did not complete after the stream ended'),
+    );
+    expect(result, isTrue);
+    expect(await userCount(), 2);
+    expect(server.ackRequests, greaterThan(0));
+  });
+
+  testWidgets('disposing the pool during an in-flight sync drains promptly', (tester) async {
+    final (sync, _) = await startSync();
+
+    final sw = Stopwatch()..start();
+    await workerManagerPatch.dispose().timeout(
+      const Duration(seconds: 15),
+      onTimeout: () => fail('dispose() hung — worker did not drain and exit'),
+    );
+    expect(sw.elapsed, lessThan(const Duration(seconds: 10)), reason: 'abort-driven, not socket-timeout bound');
+
+    expect(await sync.timeout(const Duration(seconds: 5), onTimeout: () => false), isFalse);
+  });
+
+  testWidgets('tearing down a worker blocked mid-write leaves the DB usable', (tester) async {
+    final (sync, stream) = await startSync();
+
+    // Hold an exclusive write transaction so the worker's write is blocked. The lock is taken only
+    // after the stream opens to avoid blocking the worker's own startup DB reads.
+    final releaseTxn = Completer<void>();
+    final txnHeld = Completer<void>();
+    final txn = drift.transaction(() async {
+      await drift.into(drift.userEntity).insert(
+            UserEntityCompanion.insert(
+              id: 'holder',
+              name: 'holder',
+              email: 'holder@test.com',
+              hasProfileImage: const Value(false),
+              profileChangedAt: Value(DateTime.utc(2025)),
+            ),
+          );
+      txnHeld.complete();
+      await releaseTxn.future;
+    });
+    await txnHeld.future;
+
+    sendUser(stream, 'u1', 'Alice');
+    await stream.close();
+
+    // dispose() can only finish once the worker unwinds, which is blocked on the
+    // lock — so start it, release the lock, then await completion.
+    final disposed = workerManagerPatch.dispose();
+    releaseTxn.complete();
+    await txn;
+    await disposed.timeout(
+      const Duration(seconds: 15),
+      onTimeout: () => fail('dispose() hung after releasing the write lock'),
+    );
+    await sync.timeout(const Duration(seconds: 5), onTimeout: () => false);
+
+    expect(await dbReadable(), isTrue);
+    final users = await drift.select(drift.userEntity).get();
+    expect(users.map((u) => u.id), contains('holder'));
+  });
+}

mobile/integration_test/test_utils/fake_immich_server.dart

@@ -0,0 +1,115 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+/// A dummy localhost server that implements only the endpoints that remote-sync touches.
+class FakeImmichServer {
+  FakeImmichServer._(this._server, this.version);
+
+  final HttpServer _server;
+  final (int, int, int) version;
+
+  final Completer<SyncStream> _streamOpened = Completer<SyncStream>();
+
+  int ackRequests = 0;
+
+  String get endpoint => 'http://${_server.address.host}:${_server.port}/api';
+
+  /// Resolves when the sync isolate opens `POST /sync/stream`.
+  Future<SyncStream> get streamOpened => _streamOpened.future;
+
+  static Future<FakeImmichServer> start({(int, int, int) version = (3, 0, 0)}) async {
+    final server = await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
+    final fake = FakeImmichServer._(server, version);
+    fake._listen();
+    return fake;
+  }
+
+  void _listen() {
+    // A connection torn down mid-write during teardown is expected
+    _server.listen((request) => unawaited(_route(request).catchError((_) {})));
+  }
+
+  Future<void> _route(HttpRequest request) async {
+    final method = request.method;
+    final path = request.uri.path;
+
+    if (method == 'GET' && path == '/api/server/ping') {
+      return _respondJson(request, {'res': 'pong'});
+    }
+    if (method == 'GET' && path == '/api/server/version') {
+      final (major, minor, patch) = version;
+      return _respondJson(request, {'major': major, 'minor': minor, 'patch': patch});
+    }
+    if (path == '/api/sync/ack') {
+      if (method != 'DELETE') {
+        ackRequests++;
+      }
+      return _respondEmpty(request);
+    }
+    if (method == 'POST' && path == '/api/sync/stream') {
+      return _openSyncStream(request);
+    }
+    return _respondEmpty(request, status: HttpStatus.notFound);
+  }
+
+  Future<void> _openSyncStream(HttpRequest request) async {
+    await request.drain<void>();
+    request.response
+      ..statusCode = HttpStatus.ok
+      ..headers.contentType = ContentType('application', 'jsonlines+json')
+      ..contentLength = -1 // chunked: stays open to stream incrementally
+      ..bufferOutput = false;
+    // Flush headers so the client's send() resolves and enters its read loop.
+    await request.response.flush();
+    if (!_streamOpened.isCompleted) {
+      _streamOpened.complete(SyncStream._(request.response));
+    }
+  }
+
+  Future<void> _respondJson(HttpRequest request, Object body) async {
+    await request.drain<void>();
+    request.response
+      ..statusCode = HttpStatus.ok
+      ..headers.contentType = ContentType.json
+      ..write(jsonEncode(body));
+    await request.response.close();
+  }
+
+  Future<void> _respondEmpty(HttpRequest request, {int status = HttpStatus.ok}) async {
+    await request.drain<void>();
+    request.response.statusCode = status;
+    await request.response.close();
+  }
+
+  Future<void> close() async {
+    if (_streamOpened.isCompleted) {
+      await (await _streamOpened.future).close();
+    }
+    await _server.close(force: true);
+  }
+}
+
+/// Handle to the open `/sync/stream` response: push jsonlines events, then end.
+class SyncStream {
+  SyncStream._(this._response);
+
+  final HttpResponse _response;
+  bool _closed = false;
+
+  /// [data] should be a Sync*V1 DTO's `toJson()` so the parser's `fromJson` round-trips it.
+  void send({required String type, required Object data, required String ack}) {
+    if (_closed) {
+      return;
+    }
+    _response.write('${jsonEncode({'type': type, 'data': data, 'ack': ack})}\n');
+  }
+
+  Future<void> close() async {
+    if (_closed) {
+      return;
+    }
+    _closed = true;
+    await _response.close();
+  }
+}

mobile/ios/Runner/Background/BackgroundWorker.swift

@@ -121,8 +121,8 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
   
   /**
    * Cancels the currently running background task, either due to timeout or external request.
-   * Sends a cancel signal to the Flutter side and sets up a fallback timer to ensure
-   * the completion handler is eventually called even if Flutter doesn't respond.
+   * Only tears down the engine after Dart confirms it's drained. If Dart overruns iOS's grace window,
+   * the expiration handler still calls setTaskCompleted and iOS suspends us.
    */
   func close() {
     if isComplete {
@@ -132,12 +132,6 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
     flutterApi?.cancel { result in
       self.complete(success: false)
     }
-
-    // Fallback safety mechanism: ensure completion is called within 2 seconds
-    // This prevents the background task from hanging indefinitely if Flutter doesn't respond
-    Timer.scheduledTimer(withTimeInterval: 2, repeats: false) { _ in
-      self.complete(success: false)
-    }
   }
 
   

mobile/lib/domain/services/background_worker.service.dart

@@ -188,20 +188,14 @@ class BackgroundWorkerBgService extends BackgroundWorkerFlutterApi {
       if (!_cancellationToken.isCompleted) {
         _cancellationToken.complete();
       }
-      final cleanupFutures = [
-        nativeSyncApi?.cancelHashing(),
-        workerManagerPatch.dispose().catchError((_) async {
-          // Discard any errors on the dispose call
-          return;
-        }),
-        LogService.I.dispose(),
-        Store.dispose(),
 
-        backgroundSyncManager?.cancel(),
-        _drift.optimize(allTables: true),
-      ];
-
-      await Future.wait(cleanupFutures.nonNulls);
+      // Workers share one sqlite connection, so DB teardown must wait until every worker has stopped using it.
+      await Future.wait([
+        if (backgroundSyncManager != null) backgroundSyncManager.cancel(),
+        if (nativeSyncApi != null) nativeSyncApi.cancelHashing(),
+      ]);
+      await workerManagerPatch.dispose().catchError((_) async {});
+      await Future.wait([LogService.I.dispose(), Store.dispose(), _drift.optimize(allTables: true)]);
       await _drift.close();
       await _driftLogger.close();
 

mobile/lib/domain/services/hash.service.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/services.dart';
 import 'package:immich_mobile/constants/constants.dart';
 import 'package:immich_mobile/domain/models/album/local_album.model.dart';
@@ -17,7 +19,7 @@ class HashService {
   final DriftLocalAssetRepository _localAssetRepository;
   final DriftTrashedLocalAssetRepository _trashedLocalAssetRepository;
   final NativeSyncApi _nativeSyncApi;
-  final bool Function()? _cancelChecker;
+  final Completer<void>? _cancellation;
   final _log = Logger('HashService');
 
   HashService({
@@ -25,11 +27,15 @@ class HashService {
     required this._localAssetRepository,
     required this._trashedLocalAssetRepository,
     required this._nativeSyncApi,
-    this._cancelChecker,
+    this._cancellation,
     int? batchSize,
-  }) : _batchSize = batchSize ?? kBatchHashFileLimit;
+  }) : _batchSize = batchSize ?? kBatchHashFileLimit {
+    // Stop the in-flight native hash call promptly on cancellation; the loops
+    // below also observe [isCancelled] to bail between batches.
+    _cancellation?.future.then((_) => _nativeSyncApi.cancelHashing());
+  }
 
-  bool get isCancelled => _cancelChecker?.call() ?? false;
+  bool get isCancelled => _cancellation?.isCompleted ?? false;
 
   Future<void> hashAssets() async {
     _log.info("Starting hashing of assets");

mobile/lib/domain/services/local_sync.service.dart

@@ -25,6 +25,7 @@ class LocalSyncService {
   final DriftTrashedLocalAssetRepository _trashedLocalAssetRepository;
   final AssetMediaRepository _assetMediaRepository;
   final IPermissionRepository _permissionRepository;
+  final Completer<void>? _cancellation;
   final Logger _log = Logger("DeviceSyncService");
 
   LocalSyncService({
@@ -34,8 +35,11 @@ class LocalSyncService {
     required this._trashedLocalAssetRepository,
     required this._assetMediaRepository,
     required this._permissionRepository,
+    this._cancellation,
   });
 
+  bool get _isCancelled => _cancellation?.isCompleted ?? false;
+
   Future<void> sync({bool full = false}) async {
     final Stopwatch stopwatch = Stopwatch()..start();
     try {
@@ -81,6 +85,10 @@ class LocalSyncService {
       // detect album deletions from the native side
       if (CurrentPlatform.isAndroid) {
         for (final album in dbAlbums) {
+          if (_isCancelled) {
+            _log.warning("Local sync cancelled. Stopped processing albums.");
+            return;
+          }
           final deviceIds = await _nativeSyncApi.getAssetIdsForAlbum(album.id);
           await _localAlbumRepository.syncDeletes(album.id, deviceIds);
         }
@@ -91,6 +99,10 @@ class LocalSyncService {
         // does not include changes for cloud albums.
         final cloudAlbums = deviceAlbums.where((a) => a.isCloud).toLocalAlbums();
         for (final album in cloudAlbums) {
+          if (_isCancelled) {
+            _log.warning("Local sync cancelled. Stopped processing cloud albums.");
+            return;
+          }
           final dbAlbum = dbAlbums.firstWhereOrNull((a) => a.id == album.id);
           if (dbAlbum == null) {
             _log.warning("Cloud album ${album.name} not found in local database. Skipping sync.");
@@ -135,6 +147,9 @@ class LocalSyncService {
   }
 
   Future<void> addAlbum(LocalAlbum album) async {
+    if (_isCancelled) {
+      return;
+    }
     try {
       _log.fine("Adding device album ${album.name}");
 
@@ -162,6 +177,9 @@ class LocalSyncService {
 
   // The deviceAlbum is ignored since we are going to refresh it anyways
   FutureOr<bool> updateAlbum(LocalAlbum dbAlbum, LocalAlbum deviceAlbum) async {
+    if (_isCancelled) {
+      return false;
+    }
     try {
       _log.fine("Syncing device album ${dbAlbum.name}");
 

mobile/lib/domain/services/log.service.dart

@@ -112,10 +112,16 @@ class LogService {
     return _flushBuffer();
   }
 
-  Future<void> dispose() {
+  Future<void> dispose() async {
     _flushTimer?.cancel();
-    _logSubscription.cancel();
-    return _flushBuffer();
+    _flushTimer = null;
+    await _logSubscription.cancel();
+    await _flushBuffer();
+    // Allow a subsequent init() (e.g. when a worker isolate is reused) to
+    // create a fresh instance instead of returning this disposed one.
+    if (identical(_instance, this)) {
+      _instance = null;
+    }
   }
 
   Future<void> _flushBuffer() async {

mobile/lib/domain/services/store.service.dart

@@ -54,7 +54,13 @@ class StoreService {
   /// Disposes the store and cancels the subscription. To reuse the store call init() again
   Future<void> dispose() async {
     await _storeUpdateSubscription?.cancel();
+    _storeUpdateSubscription = null;
     _cache.clear();
+    // Allow a subsequent init() (e.g. when a worker isolate is reused) to
+    // create a fresh instance instead of returning this disposed one.
+    if (identical(_instance, this)) {
+      _instance = null;
+    }
   }
 
   /// Returns the cached value for [key], or `null`

mobile/lib/domain/services/sync_linked_album.service.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:immich_mobile/domain/models/album/local_album.model.dart';
 import 'package:immich_mobile/domain/models/store.model.dart';
@@ -5,6 +7,7 @@ import 'package:immich_mobile/domain/services/store.service.dart';
 import 'package:immich_mobile/infrastructure/repositories/local_album.repository.dart';
 import 'package:immich_mobile/infrastructure/repositories/remote_album.repository.dart';
 import 'package:immich_mobile/providers/infrastructure/album.provider.dart';
+import 'package:immich_mobile/providers/infrastructure/cancel.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/store.provider.dart';
 import 'package:immich_mobile/repositories/drift_album_api_repository.dart';
 import 'package:immich_mobile/utils/debug_print.dart';
@@ -16,6 +19,7 @@ final syncLinkedAlbumServiceProvider = Provider(
     ref.watch(remoteAlbumRepository),
     ref.watch(driftAlbumApiRepositoryProvider),
     ref.watch(storeServiceProvider),
+    cancellation: ref.watch(cancellationProvider),
   ),
 );
 
@@ -24,13 +28,15 @@ class SyncLinkedAlbumService {
   final DriftRemoteAlbumRepository _remoteAlbumRepository;
   final DriftAlbumApiRepository _albumApiRepository;
   final StoreService _storeService;
+  final Completer<void>? _cancellation;
 
   SyncLinkedAlbumService(
     this._localAlbumRepository,
     this._remoteAlbumRepository,
     this._albumApiRepository,
-    this._storeService,
-  );
+    this._storeService, {
+    this._cancellation,
+  });
 
   final _log = Logger("SyncLinkedAlbumService");
 
@@ -55,7 +61,11 @@ class SyncLinkedAlbumService {
         final assetIds = await _remoteAlbumRepository.getLinkedAssetIds(userId, localAlbum.id, linkedRemoteAlbumId);
         _log.fine("Syncing ${assetIds.length} assets to remote album: ${remoteAlbum.name}");
         if (assetIds.isNotEmpty) {
-          final album = await _albumApiRepository.addAssets(remoteAlbum.id, assetIds);
+          final album = await _albumApiRepository.addAssets(
+            remoteAlbum.id,
+            assetIds,
+            abortTrigger: _cancellation?.future,
+          );
           await _remoteAlbumRepository.addAssets(remoteAlbum.id, album.added);
         }
       }),

mobile/lib/domain/services/sync_stream.service.dart

@@ -38,7 +38,7 @@ class SyncStreamService {
   final IPermissionRepository _permissionRepository;
   final SyncMigrationRepository _syncMigrationRepository;
   final ApiService _api;
-  final bool Function()? _cancelChecker;
+  final Completer<void>? _cancellation;
 
   SyncStreamService({
     required this._syncApiRepository,
@@ -49,10 +49,10 @@ class SyncStreamService {
     required this._permissionRepository,
     required this._syncMigrationRepository,
     required this._api,
-    this._cancelChecker,
+    this._cancellation,
   });
 
-  bool get isCancelled => _cancelChecker?.call() ?? false;
+  bool get isCancelled => _cancellation?.isCompleted ?? false;
 
   Future<bool> sync() async {
     _logger.info("Remote sync request for user");
@@ -80,10 +80,15 @@ class SyncStreamService {
       _handleEvents,
       serverVersion: serverSemVer,
       onReset: () => shouldReset = true,
+      abortSignal: _cancellation?.future,
     );
     if (shouldReset) {
       _logger.info("Resetting sync state as requested by server");
-      await _syncApiRepository.streamChanges(_handleEvents, serverVersion: serverSemVer);
+      await _syncApiRepository.streamChanges(
+        _handleEvents,
+        serverVersion: serverSemVer,
+        abortSignal: _cancellation?.future,
+      );
     }
 
     previousLength = migrations.length;
@@ -318,7 +323,7 @@ class SyncStreamService {
   }
 
   Future<void> handleWsAssetUploadReadyV1Batch(List<dynamic> batchData) async {
-    if (batchData.isEmpty) {
+    if (batchData.isEmpty || isCancelled) {
       return;
     }
 
@@ -361,7 +366,7 @@ class SyncStreamService {
   }
 
   Future<void> handleWsAssetUploadReadyV2Batch(List<dynamic> batchData) async {
-    if (batchData.isEmpty) {
+    if (batchData.isEmpty || isCancelled) {
       return;
     }
 
@@ -404,6 +409,9 @@ class SyncStreamService {
   }
 
   Future<void> handleWsAssetEditReadyV1(dynamic data) async {
+    if (isCancelled) {
+      return;
+    }
     _logger.info('Processing AssetEditReadyV1 event');
 
     try {
@@ -444,6 +452,9 @@ class SyncStreamService {
   }
 
   Future<void> handleWsAssetEditReadyV2(dynamic data) async {
+    if (isCancelled) {
+      return;
+    }
     _logger.info('Processing AssetEditReadyV2 event');
 
     try {

mobile/lib/domain/utils/background_sync.dart

@@ -50,53 +50,27 @@ class BackgroundSyncManager {
   });
 
   Future<void> cancel() async {
-    final futures = <Future>[];
-
-    if (_syncTask != null) {
-      futures.add(_syncTask!.future);
+    final tasks = [
+      _syncTask,
+      _syncWebsocketTask,
+      _cloudIdSyncTask,
+      _linkedAlbumSyncTask,
+      _deviceAlbumSyncTask,
+      _hashTask,
+    ];
+    final futures = [
+      for (final task in tasks)
+        if (task != null) task.future,
+    ];
+    for (final task in tasks) {
+      task?.cancel();
     }
-    _syncTask?.cancel();
     _syncTask = null;
-
-    if (_syncWebsocketTask != null) {
-      futures.add(_syncWebsocketTask!.future);
-    }
-    _syncWebsocketTask?.cancel();
     _syncWebsocketTask = null;
-
-    if (_cloudIdSyncTask != null) {
-      futures.add(_cloudIdSyncTask!.future);
-    }
-    _cloudIdSyncTask?.cancel();
     _cloudIdSyncTask = null;
-
-    if (_linkedAlbumSyncTask != null) {
-      futures.add(_linkedAlbumSyncTask!.future);
-    }
-    _linkedAlbumSyncTask?.cancel();
     _linkedAlbumSyncTask = null;
-
-    try {
-      await Future.wait(futures);
-    } on CanceledError {
-      // Ignore cancellation errors
-    }
-  }
-
-  Future<void> cancelLocal() async {
-    final futures = <Future>[];
-
-    if (_hashTask != null) {
-      futures.add(_hashTask!.future);
-    }
-    _hashTask?.cancel();
-    _hashTask = null;
-
-    if (_deviceAlbumSyncTask != null) {
-      futures.add(_deviceAlbumSyncTask!.future);
-    }
-    _deviceAlbumSyncTask?.cancel();
     _deviceAlbumSyncTask = null;
+    _hashTask = null;
 
     try {
       await Future.wait(futures);

mobile/lib/domain/utils/migrate_cloud_ids.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:drift/drift.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:immich_mobile/constants/constants.dart';
@@ -9,6 +11,7 @@ import 'package:immich_mobile/infrastructure/repositories/db.repository.dart';
 import 'package:immich_mobile/infrastructure/repositories/local_album.repository.dart';
 import 'package:immich_mobile/platform/native_sync_api.g.dart';
 import 'package:immich_mobile/providers/api.provider.dart';
+import 'package:immich_mobile/providers/infrastructure/cancel.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/db.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/sync.provider.dart';
 import 'package:immich_mobile/providers/server_info.provider.dart';
@@ -51,9 +54,10 @@ Future<void> syncCloudIds(ProviderContainer ref) async {
   }
 
   final assetApi = ref.read(apiServiceProvider).assetsApi;
+  final cancellation = ref.read(cancellationProvider);
 
   // Process cloud IDs in paginated batches
-  await _processCloudIdMappingsInBatches(db, currentUser.id, assetApi, canBulkUpdateMetadata, logger);
+  await _processCloudIdMappingsInBatches(db, currentUser.id, assetApi, canBulkUpdateMetadata, logger, cancellation);
 }
 
 Future<void> _processCloudIdMappingsInBatches(
@@ -62,12 +66,17 @@ Future<void> _processCloudIdMappingsInBatches(
   AssetsApi assetsApi,
   bool canBulkUpdate,
   Logger logger,
+  Completer<void> cancellation,
 ) async {
   const pageSize = 20000;
   String? lastLocalId;
   final seenRemoteAssetIds = <String>{};
 
   while (true) {
+    if (cancellation.isCompleted) {
+      logger.warning('Cloud ID migration cancelled. Stopping batch processing.');
+      break;
+    }
     final mappings = await _fetchCloudIdMappings(drift, userId, pageSize, lastLocalId);
     if (mappings.isEmpty) {
       break;
@@ -98,9 +107,9 @@ Future<void> _processCloudIdMappingsInBatches(
 
     if (items.isNotEmpty) {
       if (canBulkUpdate) {
-        await _bulkUpdateCloudIds(assetsApi, items);
+        await _bulkUpdateCloudIds(assetsApi, items, cancellation.future);
       } else {
-        await _sequentialUpdateCloudIds(assetsApi, items);
+        await _sequentialUpdateCloudIds(assetsApi, items, cancellation);
       }
     }
 
@@ -111,20 +120,35 @@ Future<void> _processCloudIdMappingsInBatches(
   }
 }
 
-Future<void> _sequentialUpdateCloudIds(AssetsApi assetsApi, List<AssetMetadataBulkUpsertItemDto> items) async {
+Future<void> _sequentialUpdateCloudIds(
+  AssetsApi assetsApi,
+  List<AssetMetadataBulkUpsertItemDto> items,
+  Completer<void> cancellation,
+) async {
   for (final item in items) {
+    if (cancellation.isCompleted) {
+      break;
+    }
     final upsertItem = AssetMetadataUpsertItemDto(key: item.key, value: item.value);
     try {
-      await assetsApi.updateAssetMetadata(item.assetId, AssetMetadataUpsertDto(items: [upsertItem]));
+      await assetsApi.updateAssetMetadata(
+        item.assetId,
+        AssetMetadataUpsertDto(items: [upsertItem]),
+        abortTrigger: cancellation.future,
+      );
     } catch (error, stack) {
       Logger('migrateCloudIds').warning('Failed to update metadata for asset ${item.assetId}', error, stack);
     }
   }
 }
 
-Future<void> _bulkUpdateCloudIds(AssetsApi assetsApi, List<AssetMetadataBulkUpsertItemDto> items) async {
+Future<void> _bulkUpdateCloudIds(
+  AssetsApi assetsApi,
+  List<AssetMetadataBulkUpsertItemDto> items,
+  Future<void> abortTrigger,
+) async {
   try {
-    await assetsApi.updateBulkAssetMetadata(AssetMetadataBulkUpsertDto(items: items));
+    await assetsApi.updateBulkAssetMetadata(AssetMetadataBulkUpsertDto(items: items), abortTrigger: abortTrigger);
   } catch (error, stack) {
     Logger('migrateCloudIds').warning('Failed to bulk update metadata', error, stack);
   }

mobile/lib/infrastructure/repositories/sync_api.repository.dart

@@ -29,6 +29,7 @@ class SyncApiRepository {
     Function()? onReset,
     int batchSize = kSyncEventBatchSize,
     http.Client? httpClient,
+    Future<void>? abortSignal,
   }) async {
     final stopwatch = Stopwatch()..start();
     final client = httpClient ?? NetworkRepository.client;
@@ -36,7 +37,7 @@ class SyncApiRepository {
 
     final headers = {'Content-Type': 'application/json', 'Accept': 'application/jsonlines+json'};
 
-    final request = http.Request('POST', Uri.parse(endpoint));
+    final request = http.AbortableRequest('POST', Uri.parse(endpoint), abortTrigger: abortSignal);
     request.headers.addAll(headers);
     request.body = jsonEncode(
       SyncStreamDto(

mobile/lib/providers/infrastructure/cancel.provider.dart

@@ -1,8 +1,9 @@
+import 'dart:async';
+
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 
-/// Provider holding a boolean function that returns true when cancellation is requested.
-/// A computation running in the isolate uses the function to implement cooperative cancellation.
-final cancellationProvider = Provider<bool Function()>(
+/// Holds the isolate's cancellation signal.
+final cancellationProvider = Provider<Completer<void>>(
   // This will be overridden in the isolate's container.
   // Throwing ensures it's not used without an override.
   (ref) => throw UnimplementedError(

mobile/lib/providers/infrastructure/sync.provider.dart

@@ -26,7 +26,7 @@ final syncStreamServiceProvider = Provider(
     permissionRepository: ref.watch(permissionRepositoryProvider),
     syncMigrationRepository: ref.watch(syncMigrationRepositoryProvider),
     api: ref.watch(apiServiceProvider),
-    cancelChecker: ref.watch(cancellationProvider),
+    cancellation: ref.watch(cancellationProvider),
   ),
 );
 
@@ -42,6 +42,7 @@ final localSyncServiceProvider = Provider(
     assetMediaRepository: ref.watch(assetMediaRepositoryProvider),
     permissionRepository: ref.watch(permissionRepositoryProvider),
     nativeSyncApi: ref.watch(nativeSyncApiProvider),
+    cancellation: ref.watch(cancellationProvider),
   ),
 );
 
@@ -51,5 +52,6 @@ final hashServiceProvider = Provider(
     localAssetRepository: ref.watch(localAssetRepository),
     nativeSyncApi: ref.watch(nativeSyncApiProvider),
     trashedLocalAssetRepository: ref.watch(trashedLocalAssetRepository),
+    cancellation: ref.watch(cancellationProvider),
   ),
 );

mobile/lib/repositories/drift_album_api_repository.dart

@@ -41,8 +41,14 @@ class DriftAlbumApiRepository extends ApiRepository {
     return (removed: removed, failed: failed);
   }
 
-  Future<({List<String> added, List<String> failed})> addAssets(String albumId, Iterable<String> assetIds) async {
-    final response = await checkNull(_api.addAssetsToAlbum(albumId, BulkIdsDto(ids: assetIds.toList())));
+  Future<({List<String> added, List<String> failed})> addAssets(
+    String albumId,
+    Iterable<String> assetIds, {
+    Future<void>? abortTrigger,
+  }) async {
+    final response = await checkNull(
+      _api.addAssetsToAlbum(albumId, BulkIdsDto(ids: assetIds.toList()), abortTrigger: abortTrigger),
+    );
     final List<String> added = [], failed = [];
     for (final dto in response) {
       if (dto.success) {

mobile/lib/utils/isolate.dart

@@ -8,10 +8,9 @@ import 'package:immich_mobile/entities/store.entity.dart';
 import 'package:immich_mobile/providers/infrastructure/cancel.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/db.provider.dart';
 import 'package:immich_mobile/utils/bootstrap.dart';
-import 'package:immich_mobile/utils/debug_print.dart';
 import 'package:immich_mobile/wm_executor.dart';
 import 'package:logging/logging.dart';
-import 'package:worker_manager/worker_manager.dart';
+import 'package:worker_manager/worker_manager.dart' show Cancelable;
 
 class InvalidIsolateUsageException implements Exception {
   const InvalidIsolateUsageException();
@@ -30,50 +29,27 @@ Cancelable<T?> runInIsolateGentle<T>({
     throw const InvalidIsolateUsageException();
   }
 
-  return workerManagerPatch.executeGentle((cancelledChecker) async {
-    T? result;
-    await runZonedGuarded(
-      () async {
-        BackgroundIsolateBinaryMessenger.ensureInitialized(token);
-        DartPluginRegistrant.ensureInitialized();
+  return workerManagerPatch.executeGentle((onCancel) async {
+    BackgroundIsolateBinaryMessenger.ensureInitialized(token);
+    DartPluginRegistrant.ensureInitialized();
 
-        final (drift, logDb) = await Bootstrap.initDomain(shouldBufferLogs: false, listenStoreUpdates: false);
-        final ref = ProviderContainer(
-          overrides: [
-            cancellationProvider.overrideWithValue(cancelledChecker),
-            driftProvider.overrideWith(driftOverride(drift)),
-          ],
-        );
-
-        Logger log = Logger("IsolateLogger");
-
-        try {
-          result = await computation(ref);
-        } on CanceledError {
-          log.warning("Computation cancelled ${debugLabel == null ? '' : ' for $debugLabel'}");
-        } catch (error, stack) {
-          log.severe("Error in runInIsolateGentle ${debugLabel == null ? '' : ' for $debugLabel'}", error, stack);
-        } finally {
-          try {
-            ref.dispose();
-
-            await Store.dispose();
-            await LogService.I.dispose();
-            await logDb.close();
-            await drift.close();
-          } catch (error, stack) {
-            dPrint(() => "Error closing resources in isolate: $error, $stack");
-          } finally {
-            ref.dispose();
-            // Delay to ensure all resources are released
-            await Future.delayed(const Duration(seconds: 2));
-          }
-        }
-      },
-      (error, stack) {
-        dPrint(() => "Error in isolate $debugLabel zone: $error, $stack");
-      },
+    final log = Logger("IsolateLogger");
+    final (drift, logDb) = await Bootstrap.initDomain(shouldBufferLogs: false, listenStoreUpdates: false);
+    final ref = ProviderContainer(
+      overrides: [cancellationProvider.overrideWithValue(onCancel), driftProvider.overrideWith(driftOverride(drift))],
     );
-    return result;
+
+    try {
+      return await computation(ref);
+    } catch (error, stack) {
+      log.severe("Error in runInIsolateGentle${debugLabel == null ? '' : ' for $debugLabel'}", error, stack);
+      return null;
+    } finally {
+      ref.dispose();
+      await Store.dispose();
+      await LogService.I.dispose();
+      await logDb.close();
+      await drift.close();
+    }
   });
 }

mobile/lib/utils/isolate_worker.dart

@@ -0,0 +1,163 @@
+// Forked from worker_manager's `WorkerImpl` (src/worker/worker_io.dart): a
+// `CancelRequest` completes the computation's [Completer] (so it can await
+// cancellation and unwind) instead of flipping a polled flag, and [shutdown]
+// lets the isolate drain and exit on its own rather than force-killing it. Only
+// the gentle-with-cancellation path immich uses is kept.
+//
+// ignore_for_file: implementation_imports
+
+import 'dart:async';
+import 'dart:isolate';
+
+import 'package:worker_manager/src/scheduling/task.dart';
+import 'package:worker_manager/src/worker/cancel_request.dart';
+import 'package:worker_manager/src/worker/result.dart';
+
+/// A worker computation that receives a [Completer] which completes on
+/// cancellation: await its future to react promptly, or read `isCompleted`.
+typedef GentleExecution<R> = FutureOr<R> Function(Completer<void> onCancel);
+
+class _Shutdown {
+  const _Shutdown();
+}
+
+class IsolateWorker {
+  IsolateWorker();
+
+  Isolate? _isolate;
+  RawReceivePort? _receivePort;
+  SendPort? _sendPort;
+  Completer<void>? _sendPortReceived;
+  Completer? _result;
+
+  String? taskId;
+
+  bool get initialized => _sendPortReceived?.isCompleted ?? false;
+
+  bool get initializing {
+    final sendPortReceived = _sendPortReceived;
+    return sendPortReceived != null && !sendPortReceived.isCompleted;
+  }
+
+  Future<void> initialize() async {
+    final sendPortReceived = _sendPortReceived = Completer<void>();
+    final receivePort = _receivePort = RawReceivePort();
+    receivePort.handler = (Object message) {
+      if (message is SendPort) {
+        _sendPort = message;
+        sendPortReceived.complete();
+      } else if (message is ResultSuccess) {
+        _result?.complete(message.value);
+        _afterTask();
+      } else if (message is ResultError) {
+        _result?.completeError(message.error, message.stackTrace);
+        _afterTask();
+      }
+    };
+    _isolate = await Isolate.spawn(_isolateEntry, receivePort.sendPort, errorsAreFatal: false);
+    await sendPortReceived.future;
+  }
+
+  Future<R> work<R>(Task<R> task) async {
+    taskId = task.id;
+    final result = _result = Completer();
+    _sendPort!.send(task.execution);
+    return await (result.future as Future<R>);
+  }
+
+  /// Cancels the current task without retiring the worker.
+  void cancelGentle() => _sendPort?.send(CancelRequest());
+
+  /// Cancels any in-flight task and awaits the isolate exiting on its own — no
+  /// force-kill, so `finally` blocks and native cleanup always run.
+  ///
+  /// Detaches the slot up front so a concurrent [initialize] can revive it
+  /// without colliding (revival installs fresh ports while this drains the ones
+  /// it captured locally). A revived worker is always idle, so the still-live
+  /// receive-port handler can't misroute a result.
+  Future<void> shutdown() async {
+    final sendPortReceived = _sendPortReceived;
+    if (sendPortReceived != null && !sendPortReceived.isCompleted) {
+      await sendPortReceived.future;
+    }
+
+    final isolate = _isolate;
+    final receivePort = _receivePort;
+    final sendPort = _sendPort;
+    if (isolate == null || receivePort == null || sendPort == null) {
+      return;
+    }
+    _isolate = null;
+    _sendPort = null;
+    _sendPortReceived = null;
+    // Not _result: an in-flight task still delivers it before exiting; nulling
+    // here would drop that and hang work()'s caller.
+
+    final exited = Completer<void>();
+    final exitPort = RawReceivePort();
+    exitPort.handler = (_) {
+      if (!exited.isCompleted) {
+        exited.complete();
+      }
+      exitPort.close();
+    };
+    isolate.addOnExitListener(exitPort.sendPort);
+    sendPort.send(const _Shutdown());
+    await exited.future;
+    receivePort.close();
+  }
+
+  void _afterTask() {
+    taskId = null;
+    _result = null;
+  }
+
+  static void _isolateEntry(SendPort sendPort) {
+    final receivePort = RawReceivePort();
+    sendPort.send(receivePort.sendPort);
+    // One task at a time, so a single completer suffices; null between tasks.
+    Completer<void>? onCancel;
+    void cancel() {
+      if (onCancel?.isCompleted == false) {
+        onCancel!.complete();
+      }
+    }
+
+    var shuttingDown = false;
+    var running = false;
+    receivePort.handler = (message) async {
+      if (message is _Shutdown) {
+        shuttingDown = true;
+        cancel();
+        if (!running) {
+          Isolate.exit();
+        }
+        return;
+      }
+      if (message is CancelRequest) {
+        cancel();
+        return;
+      }
+      final execution = message as GentleExecution;
+      onCancel = Completer<void>();
+      running = true;
+      Result result;
+      try {
+        result = ResultSuccess(await execution(onCancel!));
+      } catch (error, stackTrace) {
+        result = ResultError(error, stackTrace);
+      } finally {
+        onCancel = null;
+        running = false;
+      }
+      if (shuttingDown) {
+        // An isolate that has used platform channels can't exit on its own (Flutter's BackgroundIsolateBinaryMessenger
+        // opens an undisposable port), so closing our ports isn't enough. Isolate.exit delivers the result as its final
+        // message and terminates. It's abrupt (skips pending finally/microtasks) but safe here: the computation and its
+        // `finally` are already done and there's no await before this, so nothing pending is skipped.
+        Isolate.exit(sendPort, result);
+      }
+      sendPort.send(result);
+    };
+  }
+}

mobile/lib/wm_executor.dart

@@ -6,8 +6,8 @@ import 'dart:math';
 
 import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
+import 'package:immich_mobile/utils/isolate_worker.dart';
 import 'package:worker_manager/src/number_of_processors/processors_io.dart';
-import 'package:worker_manager/src/worker/worker.dart';
 import 'package:worker_manager/worker_manager.dart';
 
 final workerManagerPatch = _Executor();
@@ -16,6 +16,13 @@ final workerManagerPatch = _Executor();
 const _minId = -9007199254740992;
 const _maxId = 9007199254740992;
 
+class _GentleTask<R> extends Task<R> implements Gentle {
+  @override
+  final GentleExecution<R> execution;
+
+  _GentleTask({required super.id, required super.completer, required super.workPriority, required this.execution});
+}
+
 class Mixinable<T> {
   late final itSelf = this as T;
 }
@@ -51,13 +58,13 @@ mixin _ExecutorLogger on Mixinable<_Executor> {
 
 class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
   final _queue = PriorityQueue<Task>();
-  final _pool = <Worker>[];
+  final _pool = <IsolateWorker>[];
   var _nextTaskId = _minId;
   var _dynamicSpawning = false;
   var _isolatesCount = numberOfProcessors;
 
   @visibleForTesting
-  UnmodifiableListView<Worker> get pool => UnmodifiableListView(_pool);
+  UnmodifiableListView<IsolateWorker> get pool => UnmodifiableListView(_pool);
 
   @override
   Future<void> init({int? isolatesCount, bool? dynamicSpawning}) async {
@@ -80,117 +87,37 @@ class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
   @override
   Future<void> dispose() async {
     _queue.clear();
-    for (final worker in _pool) {
-      if (worker.initialized || worker.initializing) {
-        worker.kill();
-      }
-    }
+    final shutdown = _pool.map((worker) => worker.shutdown()).toList(growable: false);
     _pool.clear();
+    await Future.wait(shutdown);
     super.dispose();
   }
 
-  Cancelable<R> execute<R>(Execute<R> execution, {WorkPriority priority = WorkPriority.immediately}) {
-    return _createCancelable<R>(execution: execution, priority: priority);
-  }
-
-  Cancelable<R> executeNow<R>(ExecuteGentle<R> execution) {
-    final task = TaskGentle<R>(
-      id: "",
-      workPriority: WorkPriority.immediately,
-      execution: execution,
-      completer: Completer<R>(),
-    );
-
-    Future<void> run() async {
-      try {
-        final result = await execution(() => task.canceled);
-        task.complete(result, null, null);
-      } catch (error, st) {
-        task.complete(null, error, st);
-      }
-    }
-
-    run();
-    return Cancelable(completer: task.completer, onCancel: () => _cancel(task));
-  }
-
-  Cancelable<R> executeWithPort<R, T>(
-    ExecuteWithPort<R> execution, {
-    WorkPriority priority = WorkPriority.immediately,
-    required void Function(T value) onMessage,
-  }) {
-    return _createCancelable<R>(
-      execution: execution,
-      priority: priority,
-      onMessage: (message) => onMessage(message as T),
-    );
-  }
-
-  Cancelable<R> executeGentle<R>(ExecuteGentle<R> execution, {WorkPriority priority = WorkPriority.immediately}) {
-    return _createCancelable<R>(execution: execution, priority: priority);
-  }
-
-  Cancelable<R> executeGentleWithPort<R, T>(
-    ExecuteGentleWithPort<R> execution, {
-    WorkPriority priority = WorkPriority.immediately,
-    required void Function(T value) onMessage,
-  }) {
-    return _createCancelable<R>(
-      execution: execution,
-      priority: priority,
-      onMessage: (message) => onMessage(message as T),
-    );
-  }
-
-  void _createWorkers() {
-    for (var i = 0; i < _isolatesCount; i++) {
-      _pool.add(Worker());
-    }
-  }
-
-  Future<void> _initializeWorkers() async {
-    await Future.wait(_pool.map((e) => e.initialize()));
-  }
-
-  Cancelable<R> _createCancelable<R>({
-    required Function execution,
-    WorkPriority priority = WorkPriority.immediately,
-    void Function(Object value)? onMessage,
-  }) {
+  /// Runs [execution] on a worker isolate; its [Completer] completes when the
+  /// returned [Cancelable] is cancelled.
+  Cancelable<R> executeGentle<R>(GentleExecution<R> execution, {WorkPriority priority = WorkPriority.immediately}) {
     if (_nextTaskId + 1 == _maxId) {
       _nextTaskId = _minId;
     }
     final id = _nextTaskId.toString();
     _nextTaskId++;
-    late final Task<R> task;
-    final completer = Completer<R>();
-    if (execution is ExecuteWithPort<R>) {
-      task = TaskWithPort<R>(
-        id: id,
-        workPriority: priority,
-        execution: execution,
-        completer: completer,
-        onMessage: onMessage!,
-      );
-    } else if (execution is ExecuteGentle<R>) {
-      task = TaskGentle<R>(id: id, workPriority: priority, execution: execution, completer: completer);
-    } else if (execution is ExecuteGentleWithPort<R>) {
-      task = TaskGentleWithPort<R>(
-        id: id,
-        workPriority: priority,
-        execution: execution,
-        completer: completer,
-        onMessage: onMessage!,
-      );
-    } else if (execution is Execute<R>) {
-      task = TaskRegular<R>(id: id, workPriority: priority, execution: execution, completer: completer);
-    }
+    final task = _GentleTask<R>(id: id, workPriority: priority, execution: execution, completer: Completer<R>());
     _queue.add(task);
     _schedule();
     logTaskAdded(task.id);
     return Cancelable(completer: task.completer, onCancel: () => _cancel(task));
   }
 
+  void _createWorkers() {
+    for (var i = 0; i < _isolatesCount; i++) {
+      _pool.add(IsolateWorker());
+    }
+  }
+
+  Future<void> _initializeWorkers() async {
+    await Future.wait(_pool.map((e) => e.initialize()));
+  }
+
   Future<void> _ensureWorkersInitialized() async {
     if (_pool.isEmpty) {
       _createWorkers();
@@ -240,7 +167,9 @@ class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
         )
         .whenComplete(() {
           if (_dynamicSpawning && _queue.isEmpty) {
-            availableWorker.kill();
+            // Retire the idle worker; shutdown() nulls its fields so the husk
+            // stays pooled and is revived by initialize() if work arrives.
+            unawaited(availableWorker.shutdown());
           }
           _schedule();
         });
@@ -250,15 +179,8 @@ class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
   void _cancel(Task task) {
     task.cancel();
     _queue.remove(task);
-    final targetWorker = _pool.firstWhereOrNull((worker) => worker.taskId == task.id);
-    if (task is Gentle) {
-      targetWorker?.cancelGentle();
-    } else {
-      targetWorker?.kill();
-      if (!_dynamicSpawning) {
-        targetWorker?.initialize();
-      }
-    }
+    // All tasks are gentle: signal cancellation; the worker unwinds on its own.
+    _pool.firstWhereOrNull((worker) => worker.taskId == task.id)?.cancelGentle();
     super._cancel(task);
   }
 }

mobile/test/domain/services/sync_stream_service_test.dart

@@ -36,13 +36,6 @@ class _AbortCallbackWrapper {
 
 class _MockAbortCallbackWrapper extends Mock implements _AbortCallbackWrapper {}
 
-class _CancellationWrapper {
-  const _CancellationWrapper();
-
-  bool call() => false;
-}
-
-class _MockCancellationWrapper extends Mock implements _CancellationWrapper {}
 
 void main() {
   late SyncStreamService sut;
@@ -94,9 +87,13 @@ void main() {
 
     when(() => mockAbortCallbackWrapper()).thenReturn(false);
 
-    when(() => mockSyncApiRepo.streamChanges(any(), serverVersion: any(named: 'serverVersion'))).thenAnswer((
-      invocation,
-    ) async {
+    when(
+      () => mockSyncApiRepo.streamChanges(
+        any(),
+        serverVersion: any(named: 'serverVersion'),
+        abortSignal: any(named: 'abortSignal'),
+      ),
+    ).thenAnswer((invocation) async {
       handleEventsCallback = invocation.positionalArguments.first;
     });
 
@@ -105,6 +102,7 @@ void main() {
         any(),
         onReset: any(named: 'onReset'),
         serverVersion: any(named: 'serverVersion'),
+        abortSignal: any(named: 'abortSignal'),
       ),
     ).thenAnswer((invocation) async {
       handleEventsCallback = invocation.positionalArguments.first;
@@ -233,8 +231,7 @@ void main() {
     });
 
     test("aborts and stops processing if cancelled during iteration", () async {
-      final cancellationChecker = _MockCancellationWrapper();
-      when(() => cancellationChecker()).thenReturn(false);
+      final cancellation = Completer<void>();
 
       sut = SyncStreamService(
         syncApiRepository: mockSyncApiRepo,
@@ -243,7 +240,7 @@ void main() {
         trashedLocalAssetRepository: mockTrashedLocalAssetRepo,
         assetMediaRepository: mockAssetMediaRepo,
         permissionRepository: mockPermissionRepo,
-        cancelChecker: cancellationChecker.call,
+        cancellation: cancellation,
         api: mockApi,
         syncMigrationRepository: mockSyncMigrationRepo,
       );
@@ -252,7 +249,7 @@ void main() {
       final events = [SyncStreamStub.userDeleteV1, SyncStreamStub.userV1Admin, SyncStreamStub.partnerDeleteV1];
 
       when(() => mockSyncStreamRepo.deleteUsersV1(any())).thenAnswer((_) async {
-        when(() => cancellationChecker()).thenReturn(true);
+        cancellation.complete();
       });
 
       await handleEventsCallback(events, mockAbortCallbackWrapper.call, mockResetCallbackWrapper.call);
@@ -267,8 +264,7 @@ void main() {
     });
 
     test("aborts and stops processing if cancelled before processing batch", () async {
-      final cancellationChecker = _MockCancellationWrapper();
-      when(() => cancellationChecker()).thenReturn(false);
+      final cancellation = Completer<void>();
 
       final processingCompleter = Completer<void>();
       bool handler1Started = false;
@@ -284,7 +280,7 @@ void main() {
         trashedLocalAssetRepository: mockTrashedLocalAssetRepo,
         assetMediaRepository: mockAssetMediaRepo,
         permissionRepository: mockPermissionRepo,
-        cancelChecker: cancellationChecker.call,
+        cancellation: cancellation,
         api: mockApi,
         syncMigrationRepository: mockSyncMigrationRepo,
       );
@@ -303,7 +299,7 @@ void main() {
       expect(handler1Started, isTrue);
 
       // Signal cancellation while handler 1 is waiting
-      when(() => cancellationChecker()).thenReturn(true);
+      cancellation.complete();
       await pumpEventQueue();
 
       processingCompleter.complete();

mobile/test/unit/utils/isolate_worker_test.dart

@@ -0,0 +1,23 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:immich_mobile/wm_executor.dart';
+
+void main() {
+  tearDown(workerManagerPatch.dispose);
+
+  test('dispose() drains a cancelled task and delivers its result', () async {
+    await workerManagerPatch.init(isolatesCount: 1, dynamicSpawning: false);
+
+    final task = workerManagerPatch.executeGentle((onCancel) async {
+      await onCancel.future;
+      return 'drained';
+    });
+
+    await workerManagerPatch.dispose();
+
+    expect(
+      await task.timeout(const Duration(seconds: 5)),
+      'drained',
+      reason: 'the worker must finish and return its result, not be killed mid-task',
+    );
+  });
+}