diff --git a/lib/services/sync/sync_outbox.dart b/lib/services/sync/sync_outbox.dart
index 9a708ef..007e817 100644
--- a/lib/services/sync/sync_outbox.dart
+++ b/lib/services/sync/sync_outbox.dart
@@ -4,21 +4,38 @@ import 'package:shared_preferences/shared_preferences.dart';
 import 'sync_models.dart';
 
 class SyncOutbox {
-  static const String _outboxStorageKey = 'motorsignal_sync_outbox_manifest_v1';
+  static const String _outboxStorageKeyPrefix = 'motorsignal_sync_outbox_manifest_v2';
   static const int maxOutboxCapacity = 500;
   final SharedPreferences _prefs;
+  final String _storageNamespace;
   final Map<String, SyncItem> _items = {};
   Future<void> _saveChain = Future<void>.value();
   bool _isLoaded = false;
 
-  SyncOutbox(this._prefs) { load(); }
+  /// The namespace must be tied to the current Firebase UID (or a local
+  /// signed-out namespace). This prevents one account's sync state from being
+  /// mistaken for another account's state on the same device.
+  SyncOutbox(this._prefs, {String? storageNamespace})
+      : _storageNamespace = _normalizeNamespace(storageNamespace) {
+    load();
+  }
+
+  static String _normalizeNamespace(String? value) {
+    final normalized = (value == null || value.trim().isEmpty) ? 'local' : value.trim();
+    return normalized.replaceAll(RegExp(r'[^a-zA-Z0-9_.-]'), '_');
+  }
+
+  String get storageKey => '${_outboxStorageKeyPrefix}_$_storageNamespace';
   bool get isLoaded => _isLoaded;
   int get count => _items.length;
 
   void load() {
     _items.clear();
-    final rawJson = _prefs.getString(_outboxStorageKey);
-    if (rawJson == null || rawJson.trim().isEmpty) { _isLoaded = true; return; }
+    final rawJson = _prefs.getString(storageKey);
+    if (rawJson == null || rawJson.trim().isEmpty) {
+      _isLoaded = true;
+      return;
+    }
     try {
       final decoded = jsonDecode(rawJson);
       if (decoded is! List) throw const FormatException('Outbox manifest is not a list');
@@ -26,27 +43,33 @@ class SyncOutbox {
         try {
           final map = entry is Map<String, dynamic> ? entry : Map<String, dynamic>.from(entry as Map);
           final item = SyncItem.fromJson(map);
-          // An app/process death cannot leave an upload genuinely in progress.
-          // Requeue it so the provider can safely retry its deterministic operation.
           _items[item.key] = item.status == SyncStatus.uploading
               ? item.copyWith(status: SyncStatus.queued, clearNextRetry: true)
               : item;
-        } catch (itemError) { debugPrint('[SyncOutbox] Skipped malformed item: $itemError'); }
+        } catch (itemError) {
+          debugPrint('[SyncOutbox] Skipped malformed item: $itemError');
+        }
       }
-    } catch (e) { debugPrint('[SyncOutbox] Corrupt manifest recovered safely: $e'); _items.clear(); }
+    } catch (e) {
+      debugPrint('[SyncOutbox] Corrupt manifest recovered safely: $e');
+      _items.clear();
+    }
     _isLoaded = true;
   }
 
   Future<bool> _save() {
     final operation = _saveChain.then((_) async {
       if (_items.length > maxOutboxCapacity) {
-        final terminal = _items.values.where((i) => i.status.isTerminal).toList()..sort((a, b) => a.createdAt.compareTo(b.createdAt));
+        final terminal = _items.values.where((i) => i.status.isTerminal).toList()
+          ..sort((a, b) => a.createdAt.compareTo(b.createdAt));
         while (_items.length > maxOutboxCapacity && terminal.isNotEmpty) {
           _items.remove(terminal.removeAt(0).key);
         }
       }
-      if (_items.length > maxOutboxCapacity) throw StateError('Sync outbox capacity reached with no evictable terminal items.');
-      return _prefs.setString(_outboxStorageKey, jsonEncode(_items.values.map((e) => e.toJson()).toList()));
+      if (_items.length > maxOutboxCapacity) {
+        throw StateError('Sync outbox capacity reached with no evictable terminal items.');
+      }
+      return _prefs.setString(storageKey, jsonEncode(_items.values.map((e) => e.toJson()).toList()));
     });
     _saveChain = operation.then((_) {}, onError: (_) {});
     return operation;
@@ -58,22 +81,44 @@ class SyncOutbox {
   List<SyncItem> getEligibleItems(DateTime now) => _items.values.where((i) => i.isEligibleForAttempt(now)).toList(growable: false);
 
   Future<SyncItem> enqueue(int localRideId, String providerId, {DateTime? now}) async {
-    if (localRideId <= 0 || providerId.trim().isEmpty) throw ArgumentError('A positive localRideId and non-empty providerId are required.');
+    if (localRideId <= 0 || providerId.trim().isEmpty) {
+      throw ArgumentError('A positive localRideId and non-empty providerId are required.');
+    }
     final normalizedProvider = providerId.trim();
     final key = '$normalizedProvider:$localRideId';
     final existing = _items[key];
     if (existing != null) {
-      if (existing.status == SyncStatus.synced || existing.status == SyncStatus.queued || existing.status == SyncStatus.uploading) return existing;
+      if (existing.status == SyncStatus.synced || existing.status == SyncStatus.queued || existing.status == SyncStatus.uploading) {
+        return existing;
+      }
       final rearmed = existing.copyWith(status: SyncStatus.queued, clearLastError: true, clearNextRetry: true);
-      _items[key] = rearmed; await _save(); return rearmed;
+      _items[key] = rearmed;
+      await _save();
+      return rearmed;
+    }
+    if (_items.length >= maxOutboxCapacity && !_items.values.any((i) => i.status.isTerminal)) {
+      throw StateError('Sync outbox capacity reached; pending rides were not discarded.');
     }
-    if (_items.length >= maxOutboxCapacity && !_items.values.any((i) => i.status.isTerminal)) throw StateError('Sync outbox capacity reached; pending rides were not discarded.');
     final item = SyncItem(localRideId: localRideId, providerId: normalizedProvider, status: SyncStatus.queued, createdAt: now ?? DateTime.now());
-    _items[key] = item; await _save(); return item;
+    _items[key] = item;
+    await _save();
+    return item;
+  }
+
+  Future<void> update(SyncItem item) async {
+    _items[item.key] = item;
+    await _save();
+  }
+
+  Future<void> remove(int localRideId, String providerId) async {
+    if (_items.remove('${providerId.trim()}:$localRideId') != null) await _save();
+  }
+
+  Future<void> clear() async {
+    _items.clear();
+    _saveChain = Future<void>.value();
+    await _prefs.remove(storageKey);
   }
 
-  Future<void> update(SyncItem item) async { _items[item.key] = item; await _save(); }
-  Future<void> remove(int localRideId, String providerId) async { if (_items.remove('${providerId.trim()}:$localRideId') != null) await _save(); }
-  Future<void> clear() async { _items.clear(); _saveChain = Future<void>.value(); await _prefs.remove(_outboxStorageKey); }
   bool isRideSynced(int localRideId, String providerId) => getItem(localRideId, providerId)?.status == SyncStatus.synced;
 }