diff --git a/ios/Runner/WidgetSnapshotPlugin.swift b/ios/Runner/WidgetSnapshotPlugin.swift
index 104327ab6..0bf45b86d 100644
--- a/ios/Runner/WidgetSnapshotPlugin.swift
+++ b/ios/Runner/WidgetSnapshotPlugin.swift
@@ -6,6 +6,7 @@ import WidgetKit
 enum WidgetSnapshotKind: String {
   case weatherForecast
   case currentWeather
+  case locationCatalog
 
   var filename: String {
     switch self {
@@ -13,15 +14,19 @@ enum WidgetSnapshotKind: String {
       return "weather-forecast.json"
     case .currentWeather:
       return "current-weather.json"
+    case .locationCatalog:
+      return "location-catalog.json"
     }
   }
 
-  var widgetKind: String {
+  var widgetKind: String? {
     switch self {
     case .weatherForecast:
       return "DPIPWidgets"
     case .currentWeather:
       return "DPIPWidgets"
+    case .locationCatalog:
+      return nil
     }
   }
 }
@@ -144,8 +149,10 @@ public final class WidgetSnapshotPlugin: NSObject, FlutterPlugin {
 
       do {
         try WidgetSnapshotFile.replace(data, kind: kind, in: container)
-        WidgetCenter.shared.reloadTimelines(ofKind: kind.widgetKind)
-        DispatchQueue.main.async { result(nil) }
+          if let widgetKind = kind.widgetKind {
+            WidgetCenter.shared.reloadTimelines(ofKind: widgetKind)
+          };
+          DispatchQueue.main.async { result(nil) }
       } catch {
         DispatchQueue.main.async { result(self.flutterError(.writeFailed)) }
       }
@@ -182,7 +189,9 @@ public final class WidgetSnapshotPlugin: NSObject, FlutterPlugin {
 
       do {
         try WidgetSnapshotFile.clear(kind, in: container)
-        WidgetCenter.shared.reloadTimelines(ofKind: kind.widgetKind)
+          if let widgetKind = kind.widgetKind {
+            WidgetCenter.shared.reloadTimelines(ofKind: widgetKind)
+          }
         DispatchQueue.main.async { result(nil) }
       } catch {
         DispatchQueue.main.async { result(self.flutterError(.writeFailed)) }
diff --git a/ios/RunnerTests/RunnerTests.swift b/ios/RunnerTests/RunnerTests.swift
index 6226e98dc..f1385a739 100644
--- a/ios/RunnerTests/RunnerTests.swift
+++ b/ios/RunnerTests/RunnerTests.swift
@@ -7,9 +7,16 @@ final class RunnerTests: XCTestCase {
     let kind = try WidgetSnapshotFile.kind("weatherForecast")
     XCTAssertEqual(kind.filename, "weather-forecast.json")
     XCTAssertEqual(kind.rawValue, "weatherForecast")
+
     let currentWeather = try WidgetSnapshotFile.kind("currentWeather")
     XCTAssertEqual(currentWeather.filename, "current-weather.json")
     XCTAssertEqual(currentWeather.rawValue, "currentWeather")
+
+    let locationCatalog = try WidgetSnapshotFile.kind("locationCatalog")
+    XCTAssertEqual(locationCatalog.filename, "location-catalog.json")
+    XCTAssertEqual(locationCatalog.rawValue, "locationCatalog")
+    XCTAssertNil(locationCatalog.widgetKind)
+
     XCTAssertThrowsError(try WidgetSnapshotFile.kind("../other.json")) { error in
       XCTAssertEqual(error as? WidgetSnapshotError, .invalidKind)
     }
diff --git a/lib/app/app.dart b/lib/app/app.dart
index 7fa33624d..de654337b 100644
--- a/lib/app/app.dart
+++ b/lib/app/app.dart
@@ -12,6 +12,7 @@ import 'package:dpip/core/notifications/notification_service.dart';
 import 'package:dpip/core/notifications/notification_taps.dart';
 import 'package:dpip/core/permissions/permission_health.dart';
 import 'package:dpip/core/platform/background_location.dart';
+import 'package:dpip/core/platform/widget_location_catalog_coordinator.dart';
 import 'package:dpip/core/realtime/realtime_lifecycle.dart';
 import 'package:dpip/core/realtime/realtime_service.dart';
 import 'package:dpip/core/settings/locale_config.dart';
@@ -51,6 +52,7 @@ class DpipApp extends StatelessWidget {
         notificationService: deps.notificationService,
         locationService: deps.locationService,
         regionStore: deps.regionStore,
+        widgetLocationCatalogCoordinator: deps.widgetLocationCatalogCoordinator,
         deviceLocationReporter: deps.deviceLocationReporter,
         backgroundLocation: deps.backgroundLocation,
         locationMonitor: deps.locationMonitor,
@@ -141,6 +143,7 @@ class _AppServicesHost extends StatefulWidget {
     required this.notificationService,
     required this.locationService,
     required this.regionStore,
+    required this.widgetLocationCatalogCoordinator,
     required this.deviceLocationReporter,
     required this.backgroundLocation,
     required this.locationMonitor,
@@ -153,6 +156,7 @@ class _AppServicesHost extends StatefulWidget {
   final NotificationService notificationService;
   final LocationService locationService;
   final RegionStore regionStore;
+  final WidgetLocationCatalogCoordinator widgetLocationCatalogCoordinator;
   final DeviceLocationReporter deviceLocationReporter;
   final BackgroundLocationService backgroundLocation;
   final LocationMonitor locationMonitor;
@@ -174,6 +178,8 @@ class _AppServicesHostState extends State<_AppServicesHost>
     super.initState();
     _observer = RealtimeLifecycleObserver(widget.realtimeService);
     WidgetsBinding.instance.addObserver(this);
+
+    widget.widgetLocationCatalogCoordinator.start();
     // The map tab keeps whichever overlay the session left it on, so an EEW
     // tap has to name 強震監視器 as well as the route. Same hand-off the home
     // monitor banner and the nav bar use, so the map has one way in.
@@ -276,6 +282,7 @@ class _AppServicesHostState extends State<_AppServicesHost>
     NotificationTaps.onTap = null;
     widget.onboarding.removeListener(_onOnboardingChanged);
     WidgetsBinding.instance.removeObserver(this);
+    widget.widgetLocationCatalogCoordinator.dispose();
     _observer.dispose();
     widget.locationMonitor.dispose();
     widget.permissionHealth.dispose();
diff --git a/lib/bootstrap.dart b/lib/bootstrap.dart
index c523aa7d2..7e96e48d3 100644
--- a/lib/bootstrap.dart
+++ b/lib/bootstrap.dart
@@ -15,6 +15,8 @@ import 'package:dpip/core/logging/log_store.dart';
 import 'package:dpip/core/network/api_client.dart';
 import 'package:dpip/core/platform/background_location.dart';
 import 'package:dpip/core/platform/install_source.dart';
+import 'package:dpip/core/platform/widget_location_catalog_coordinator.dart';
+import 'package:dpip/core/platform/widget_snapshot_writer.dart';
 import 'package:dpip/core/network/dio_client.dart';
 import 'package:dpip/core/network/endpoint_health.dart';
 import 'package:dpip/core/network/etag_cache_store.dart';
@@ -287,6 +289,12 @@ Future<void> bootstrap() async {
   final townDirectory = await townDirectoryFuture;
   final townMs = Log.sinceStartMs - townStart;
   final regionStore = RegionStore(settings);
+  final widgetSnapshotWriter = IosWidgetSnapshotWriter();
+  final widgetLocationCatalogCoordinator = WidgetLocationCatalogCoordinator(
+    regionStore,
+    townDirectory,
+    widgetSnapshotWriter,
+  );
   final locationService = LocationService(
     townDirectory,
     boundaries: townBoundaries,
@@ -379,6 +387,7 @@ Future<void> bootstrap() async {
     townDirectory: townDirectory,
     townBoundaries: townBoundaries,
     regionStore: regionStore,
+    widgetLocationCatalogCoordinator: widgetLocationCatalogCoordinator,
     locationService: locationService,
     deviceLocationReporter: deviceLocationReporter,
     backgroundLocation: backgroundLocation,
diff --git a/lib/core/di/shared_deps.dart b/lib/core/di/shared_deps.dart
index ac38b8a52..05a1b682b 100644
--- a/lib/core/di/shared_deps.dart
+++ b/lib/core/di/shared_deps.dart
@@ -20,6 +20,7 @@ import 'package:dpip/core/network/region_selection.dart';
 import 'package:dpip/core/notifications/notification_service.dart';
 import 'package:dpip/core/permissions/permission_health.dart';
 import 'package:dpip/core/platform/background_location.dart';
+import 'package:dpip/core/platform/widget_location_catalog_coordinator.dart';
 import 'package:dpip/core/realtime/realtime_service.dart';
 import 'package:dpip/core/realtime/server_clock.dart';
 import 'package:dpip/core/settings/default_map_layer_controller.dart';
@@ -58,6 +59,7 @@ class SharedDeps {
     required this.townDirectory,
     required this.townBoundaries,
     required this.regionStore,
+    required this.widgetLocationCatalogCoordinator,
     required this.locationService,
     required this.deviceLocationReporter,
     required this.backgroundLocation,
@@ -117,6 +119,9 @@ class SharedDeps {
   /// App-wide Home region selection (also provided).
   final RegionStore regionStore;
 
+  /// Synchronizes DPIP's saved locations into the Widget App Group catalog.
+  final WidgetLocationCatalogCoordinator widgetLocationCatalogCoordinator;
+
   /// GPS → current township resolver (geolocator).
   final LocationService locationService;
 
diff --git a/lib/core/platform/widget_location_catalog.dart b/lib/core/platform/widget_location_catalog.dart
new file mode 100644
index 000000000..bf173b1f3
--- /dev/null
+++ b/lib/core/platform/widget_location_catalog.dart
@@ -0,0 +1,69 @@
+import 'package:dpip/core/geo/town_directory.dart';
+
+final class WidgetLocationCatalogLocation {
+  const WidgetLocationCatalogLocation({
+    required this.regionCode,
+    required this.displayName,
+    required this.administrativeAreaName,
+    required this.latitude,
+    required this.longitude,
+  });
+
+  final String regionCode;
+  final String displayName;
+  final String administrativeAreaName;
+  final double latitude;
+  final double longitude;
+
+  Map<String, Object> toJson() {
+    return {
+      'regionCode': regionCode,
+      'displayName': displayName,
+      'administrativeAreaName': administrativeAreaName,
+      'latitude': latitude,
+      'longitude': longitude,
+    };
+  }
+}
+
+final class WidgetLocationCatalog {
+  const WidgetLocationCatalog({
+    this.schemaVersion = 1,
+    required this.locations,
+  });
+
+  final int schemaVersion;
+  final List<WidgetLocationCatalogLocation> locations;
+
+  Map<String, Object> toJson() {
+    return {
+      'schemaVersion': schemaVersion,
+      'locations': [for (final location in locations) location.toJson()],
+    };
+  }
+}
+
+WidgetLocationCatalog createWidgetLocationCatalog({
+  required List<String> savedCodes,
+  required TownDirectory townDirectory,
+}) {
+  final locations = <WidgetLocationCatalogLocation>[];
+
+  for (final code in savedCodes) {
+    final town = townDirectory.byCode(code);
+
+    if (town == null) continue;
+
+    locations.add(
+      WidgetLocationCatalogLocation(
+        regionCode: town.code,
+        displayName: town.townName,
+        administrativeAreaName: town.cityName,
+        latitude: town.lat,
+        longitude: town.lng,
+      ),
+    );
+  }
+
+  return WidgetLocationCatalog(locations: locations);
+}
diff --git a/lib/core/platform/widget_location_catalog_coordinator.dart b/lib/core/platform/widget_location_catalog_coordinator.dart
new file mode 100644
index 000000000..e303551a7
--- /dev/null
+++ b/lib/core/platform/widget_location_catalog_coordinator.dart
@@ -0,0 +1,79 @@
+import 'dart:convert';
+
+import 'package:dpip/core/geo/town_directory.dart';
+import 'package:dpip/core/platform/widget_location_catalog.dart';
+import 'package:dpip/core/platform/widget_snapshot_writer.dart';
+import 'package:dpip/core/settings/region_store.dart';
+
+final class WidgetLocationCatalogCoordinator {
+  WidgetLocationCatalogCoordinator(
+    this._regions,
+    this._directory,
+    this._writer,
+  );
+
+  final RegionStore _regions;
+  final TownDirectory _directory;
+  final WidgetSnapshotWriter _writer;
+
+  List<String>? _lastSavedCodes;
+  Future<void> _pendingWrite = Future<void>.value();
+  bool _started = false;
+
+  void start() {
+    if (_started) return;
+
+    _started = true;
+    _regions.addListener(_handleRegionChanged);
+
+    _schedulePublish(force: true);
+  }
+
+  void dispose() {
+    if (!_started) return;
+
+    _regions.removeListener(_handleRegionChanged);
+    _started = false;
+  }
+
+  Future<void> waitForPendingWrites() => _pendingWrite;
+
+  void _handleRegionChanged() {
+    _schedulePublish();
+  }
+
+  void _schedulePublish({bool force = false}) {
+    final savedCodes = _regions.savedCodes;
+
+    if (!force && _sameCodes(_lastSavedCodes, savedCodes)) {
+      return;
+    }
+
+    _lastSavedCodes = List<String>.unmodifiable(savedCodes);
+
+    final catalog = createWidgetLocationCatalog(
+      savedCodes: savedCodes,
+      townDirectory: _directory,
+    );
+
+    final json = jsonEncode(catalog.toJson());
+
+    _pendingWrite = _pendingWrite.then((_) async {
+      await _writer.write(kind: WidgetSnapshotKind.locationCatalog, json: json);
+    });
+  }
+
+  bool _sameCodes(List<String>? previous, List<String> current) {
+    if (previous == null || previous.length != current.length) {
+      return false;
+    }
+
+    for (var index = 0; index < current.length; index++) {
+      if (previous[index] != current[index]) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+}
diff --git a/lib/core/platform/widget_snapshot_writer.dart b/lib/core/platform/widget_snapshot_writer.dart
index 7be128ca3..62d01b809 100644
--- a/lib/core/platform/widget_snapshot_writer.dart
+++ b/lib/core/platform/widget_snapshot_writer.dart
@@ -5,8 +5,8 @@ import 'package:dpip/core/error/result.dart';
 import 'package:dpip/core/logging/log.dart';
 import 'package:flutter/services.dart';
 
-/// Native allowlist key. This reserves a file only; no forecast producer exists.
-enum WidgetSnapshotKind { weatherForecast, currentWeather }
+/// Native allowlist key for versioned Widget shared data.
+enum WidgetSnapshotKind { weatherForecast, currentWeather, locationCatalog }
 
 /// Writes an already encoded, versioned JSON snapshot for a future widget.
 /// The caller owns its schema; this boundary owns delivery and persistence.
diff --git a/test/core/platform/widget_location_catalog_coordinator_test.dart b/test/core/platform/widget_location_catalog_coordinator_test.dart
new file mode 100644
index 000000000..6bebc75cb
--- /dev/null
+++ b/test/core/platform/widget_location_catalog_coordinator_test.dart
@@ -0,0 +1,416 @@
+import 'dart:async';
+import 'dart:convert';
+
+import 'package:dpip/core/error/result.dart';
+import 'package:dpip/core/geo/town_directory.dart';
+import 'package:dpip/core/platform/widget_location_catalog_coordinator.dart';
+import 'package:dpip/core/platform/widget_snapshot_writer.dart';
+import 'package:dpip/core/settings/region_store.dart';
+import 'package:dpip/core/settings/settings_store.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  final townDirectory = TownDirectory.fromJson({
+    '407': {
+      'city': '臺中',
+      'town': '西屯',
+      'lat': 24.1658213,
+      'lng': 120.6336717,
+      'cityLevel': '市',
+      'townLevel': '區',
+    },
+    '700': {
+      'city': '臺南',
+      'town': '中西',
+      'lat': 22.994821,
+      'lng': 120.196452,
+      'cityLevel': '市',
+      'townLevel': '區',
+    },
+  });
+
+  test('publishes the saved-location catalog when started', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407'],
+      }),
+    );
+
+    final writer = _RecordingWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    addTearDown(coordinator.dispose);
+
+    coordinator.start();
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(1));
+    expect(writer.writes.single.kind, WidgetSnapshotKind.locationCatalog);
+
+    final json = jsonDecode(writer.writes.single.json) as Map<String, dynamic>;
+
+    expect(json['schemaVersion'], 1);
+
+    final locations = json['locations'] as List<dynamic>;
+
+    expect(locations, hasLength(1));
+    expect((locations.single as Map<String, dynamic>)['regionCode'], '407');
+  });
+
+  test('does not republish when only the selected Home area changes', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407'],
+      }),
+    );
+
+    final writer = _RecordingWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    addTearDown(coordinator.dispose);
+
+    coordinator.start();
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(1));
+
+    regions.select(0);
+
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(1));
+  });
+
+  test('does not republish when only the current GPS code changes', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407'],
+      }),
+    );
+
+    final writer = _RecordingWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    addTearDown(coordinator.dispose);
+
+    coordinator.start();
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(1));
+
+    regions.setCurrentCode('700');
+
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(1));
+  });
+
+  test('republishes when the saved locations change', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407'],
+      }),
+    );
+
+    final writer = _RecordingWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    addTearDown(coordinator.dispose);
+
+    coordinator.start();
+    await coordinator.waitForPendingWrites();
+
+    regions.addSaved('700');
+
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(2));
+
+    final json = jsonDecode(writer.writes.last.json) as Map<String, dynamic>;
+    final locations = json['locations'] as List<dynamic>;
+
+    expect(
+      locations
+          .cast<Map<String, dynamic>>()
+          .map((location) => location['regionCode'])
+          .toList(),
+      ['407', '700'],
+    );
+  });
+
+  test('republishes when a saved location is removed', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407', '700'],
+      }),
+    );
+
+    final writer = _RecordingWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    addTearDown(coordinator.dispose);
+
+    coordinator.start();
+    await coordinator.waitForPendingWrites();
+
+    regions.removeSaved('407');
+
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(2));
+
+    final json = jsonDecode(writer.writes.last.json) as Map<String, dynamic>;
+    final locations = json['locations'] as List<dynamic>;
+
+    expect(
+      locations
+          .cast<Map<String, dynamic>>()
+          .map((location) => location['regionCode'])
+          .toList(),
+      ['700'],
+    );
+  });
+
+  test('republishes when a saved location is replaced', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407'],
+      }),
+    );
+
+    final writer = _RecordingWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    addTearDown(coordinator.dispose);
+
+    coordinator.start();
+    await coordinator.waitForPendingWrites();
+
+    final replaced = regions.replaceSaved('407', '700');
+
+    expect(replaced, isTrue);
+
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(2));
+
+    final json = jsonDecode(writer.writes.last.json) as Map<String, dynamic>;
+    final locations = json['locations'] as List<dynamic>;
+
+    expect(
+      locations
+          .cast<Map<String, dynamic>>()
+          .map((location) => location['regionCode'])
+          .toList(),
+      ['700'],
+    );
+  });
+
+  test('republishes when saved locations are reordered', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407', '700'],
+      }),
+    );
+
+    final writer = _RecordingWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    addTearDown(coordinator.dispose);
+
+    coordinator.start();
+    await coordinator.waitForPendingWrites();
+
+    regions.reorderSaved(1, 0);
+
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(2));
+
+    final json = jsonDecode(writer.writes.last.json) as Map<String, dynamic>;
+    final locations = json['locations'] as List<dynamic>;
+
+    expect(
+      locations
+          .cast<Map<String, dynamic>>()
+          .map((location) => location['regionCode'])
+          .toList(),
+      ['700', '407'],
+    );
+  });
+
+  test('does not publish after disposal', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407'],
+      }),
+    );
+
+    final writer = _RecordingWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    coordinator.start();
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(1));
+
+    coordinator.dispose();
+
+    regions.addSaved('700');
+
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(1));
+  });
+
+  test('serializes writes so the newest catalog is written last', () async {
+    final regions = RegionStore(
+      SettingsStore.inMemory({
+        'home.savedRegionCodes': ['407'],
+      }),
+    );
+
+    final writer = _BlockingFirstWriteWidgetSnapshotWriter();
+
+    final coordinator = WidgetLocationCatalogCoordinator(
+      regions,
+      townDirectory,
+      writer,
+    );
+
+    addTearDown(coordinator.dispose);
+
+    coordinator.start();
+
+    // Wait until the initial catalog write has actually started.
+    await writer.firstWriteStarted.future;
+
+    expect(writer.writes, hasLength(1));
+
+    // Change the saved locations while the first write is still blocked.
+    regions.addSaved('700');
+
+    // Give any queued async work a chance to run.
+    await Future<void>.delayed(Duration.zero);
+
+    // The second write must NOT start before the first one finishes.
+    expect(writer.writes, hasLength(1));
+
+    writer.releaseFirstWrite.complete();
+
+    await coordinator.waitForPendingWrites();
+
+    expect(writer.writes, hasLength(2));
+
+    final firstJson =
+        jsonDecode(writer.writes.first.json) as Map<String, dynamic>;
+    final firstLocations = firstJson['locations'] as List<dynamic>;
+
+    expect(
+      firstLocations
+          .cast<Map<String, dynamic>>()
+          .map((location) => location['regionCode'])
+          .toList(),
+      ['407'],
+    );
+
+    final lastJson =
+        jsonDecode(writer.writes.last.json) as Map<String, dynamic>;
+    final lastLocations = lastJson['locations'] as List<dynamic>;
+
+    expect(
+      lastLocations
+          .cast<Map<String, dynamic>>()
+          .map((location) => location['regionCode'])
+          .toList(),
+      ['407', '700'],
+    );
+  });
+}
+
+final class _RecordingWidgetSnapshotWriter implements WidgetSnapshotWriter {
+  final List<({WidgetSnapshotKind kind, String json})> writes = [];
+
+  @override
+  Future<Result<void>> write({
+    required WidgetSnapshotKind kind,
+    required String json,
+  }) async {
+    writes.add((kind: kind, json: json));
+    return const Ok(null);
+  }
+
+  @override
+  Future<Result<void>> clear({required WidgetSnapshotKind kind}) async {
+    return const Ok(null);
+  }
+}
+
+final class _BlockingFirstWriteWidgetSnapshotWriter
+    implements WidgetSnapshotWriter {
+  final List<({WidgetSnapshotKind kind, String json})> writes = [];
+
+  final Completer<void> firstWriteStarted = Completer<void>();
+  final Completer<void> releaseFirstWrite = Completer<void>();
+
+  @override
+  Future<Result<void>> write({
+    required WidgetSnapshotKind kind,
+    required String json,
+  }) async {
+    writes.add((kind: kind, json: json));
+
+    if (writes.length == 1) {
+      firstWriteStarted.complete();
+
+      await releaseFirstWrite.future;
+    }
+
+    return const Ok(null);
+  }
+
+  @override
+  Future<Result<void>> clear({required WidgetSnapshotKind kind}) async {
+    return const Ok(null);
+  }
+}
diff --git a/test/core/platform/widget_location_catalog_test.dart b/test/core/platform/widget_location_catalog_test.dart
new file mode 100644
index 000000000..7ac925367
--- /dev/null
+++ b/test/core/platform/widget_location_catalog_test.dart
@@ -0,0 +1,87 @@
+import 'package:dpip/core/geo/town_directory.dart';
+import 'package:dpip/core/platform/widget_location_catalog.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  final townDirectory = TownDirectory.fromJson({
+    '407': {
+      'city': '臺中',
+      'town': '西屯',
+      'lat': 24.1658213,
+      'lng': 120.6336717,
+      'cityLevel': '市',
+      'townLevel': '區',
+    },
+    '700': {
+      'city': '臺南',
+      'town': '中西',
+      'lat': 22.994821,
+      'lng': 120.196452,
+      'cityLevel': '市',
+      'townLevel': '區',
+    },
+  });
+
+  group('createWidgetLocationCatalog', () {
+    test('projects saved region codes in order', () {
+      final catalog = createWidgetLocationCatalog(
+        savedCodes: ['407', '700'],
+        townDirectory: townDirectory,
+      );
+
+      expect(catalog.schemaVersion, 1);
+      expect(catalog.locations, hasLength(2));
+
+      expect(catalog.locations[0].regionCode, '407');
+      expect(catalog.locations[0].displayName, '西屯區');
+      expect(catalog.locations[0].administrativeAreaName, '臺中市');
+      expect(catalog.locations[0].latitude, 24.1658213);
+      expect(catalog.locations[0].longitude, 120.6336717);
+
+      expect(catalog.locations[1].regionCode, '700');
+      expect(catalog.locations[1].displayName, '中西區');
+      expect(catalog.locations[1].administrativeAreaName, '臺南市');
+    });
+
+    test('omits unresolved codes while preserving resolved order', () {
+      final catalog = createWidgetLocationCatalog(
+        savedCodes: ['407', '999', '700'],
+        townDirectory: townDirectory,
+      );
+
+      expect(
+        catalog.locations.map((location) => location.regionCode).toList(),
+        ['407', '700'],
+      );
+    });
+
+    test('serializes the exact widget location catalog contract', () {
+      final catalog = createWidgetLocationCatalog(
+        savedCodes: ['407'],
+        townDirectory: townDirectory,
+      );
+
+      expect(catalog.toJson(), {
+        'schemaVersion': 1,
+        'locations': [
+          {
+            'regionCode': '407',
+            'displayName': '西屯區',
+            'administrativeAreaName': '臺中市',
+            'latitude': 24.1658213,
+            'longitude': 120.6336717,
+          },
+        ],
+      });
+    });
+
+    test('serializes an empty saved-location catalog', () {
+      final catalog = createWidgetLocationCatalog(
+        savedCodes: const [],
+        townDirectory: townDirectory,
+      );
+
+      expect(catalog.toJson(), {'schemaVersion': 1, 'locations': <Object>[]});
+    });
+  });
+}
diff --git a/test/core/platform/widget_snapshot_writer_test.dart b/test/core/platform/widget_snapshot_writer_test.dart
index 687a45f35..c96c2f0a8 100644
--- a/test/core/platform/widget_snapshot_writer_test.dart
+++ b/test/core/platform/widget_snapshot_writer_test.dart
@@ -200,6 +200,30 @@ void main() {
         entry.value,
       );
     });
+
+    test(
+      'writes the location catalog kind without exposing a file path',
+      () async {
+        final writer = IosWidgetSnapshotWriter(
+          channel: channel,
+          isSupportedPlatform: true,
+        );
+
+        const json = '{"schemaVersion":1,"locations":[]}';
+
+        final result = await writer.write(
+          kind: WidgetSnapshotKind.locationCatalog,
+          json: json,
+        );
+
+        expect(result.isOk, isTrue);
+        expect(calls.single.method, 'write');
+        expect(calls.single.arguments, {
+          'kind': 'locationCatalog',
+          'json': json,
+        });
+      },
+    );
   }
 }