diff --git a/lib/database/database.dart b/lib/database/database.dart
index 00fc344..11301da 100644
--- a/lib/database/database.dart
+++ b/lib/database/database.dart
@@ -18,7 +18,7 @@ class AppDatabase extends _$AppDatabase {
   static final Random _random = Random.secure();
 
   @override
-  int get schemaVersion => 6;
+  int get schemaVersion => 7;
 
   @override
   MigrationStrategy get migration => MigrationStrategy(
@@ -91,6 +91,9 @@ class AppDatabase extends _$AppDatabase {
           await customStatement('UPDATE rides SET cloud_ride_id = ? WHERE id = ?', [legacyId, id]);
         }
       }
+      if (from < 7) {
+        await m.addColumn(rides, rides.cloudOwnerUid);
+      }
     },
   );
 
@@ -161,6 +164,25 @@ class AppDatabase extends _$AppDatabase {
     ));
   }
 
+  Future<String?> getCloudOwnerUid(int rideId) async {
+    final rows = await customSelect(
+      'SELECT cloud_owner_uid FROM rides WHERE id = ?',
+      variables: [Variable<int>(rideId)],
+    ).get();
+    if (rows.isEmpty) return null;
+    return rows.first.data['cloud_owner_uid'] as String?;
+  }
+
+  /// Claims only an unclaimed ride. Existing ownership is immutable.
+  Future<bool> claimRideForCloudOwner(int rideId, String uid) async {
+    final normalizedUid = uid.trim();
+    if (normalizedUid.isEmpty) return false;
+    final changed = await (update(rides)
+          ..where((r) => r.id.equals(rideId) & r.cloudOwnerUid.isNull()))
+        .write(RidesCompanion(cloudOwnerUid: Value(normalizedUid)));
+    return changed == 1 || await getCloudOwnerUid(rideId) == normalizedUid;
+  }
+
   Future<void> endRide(int rideId, RidesCompanion data) async {
     await (update(rides)..where((t) => t.id.equals(rideId))).write(data.copyWith(endTime: Value(DateTime.now())));
   }
diff --git a/lib/database/database.g.dart b/lib/database/database.g.dart
index bf3b585..23e0aa7 100644
--- a/lib/database/database.g.dart
+++ b/lib/database/database.g.dart
@@ -32,6 +32,17 @@ class $RidesTable extends Rides with TableInfo<$RidesTable, Ride> {
     type: DriftSqlType.string,
     requiredDuringInsert: false,
   );
+  static const VerificationMeta _cloudOwnerUidMeta = const VerificationMeta(
+    'cloudOwnerUid',
+  );
+  @override
+  late final GeneratedColumn<String> cloudOwnerUid = GeneratedColumn<String>(
+    'cloud_owner_uid',
+    aliasedName,
+    true,
+    type: DriftSqlType.string,
+    requiredDuringInsert: false,
+  );
   static const VerificationMeta _startTimeMeta = const VerificationMeta(
     'startTime',
   );
@@ -292,6 +303,7 @@ class $RidesTable extends Rides with TableInfo<$RidesTable, Ride> {
   List<GeneratedColumn> get $columns => [
     id,
     cloudRideId,
+    cloudOwnerUid,
     startTime,
     endTime,
     distanceMiles,
@@ -339,6 +351,15 @@ class $RidesTable extends Rides with TableInfo<$RidesTable, Ride> {
         ),
       );
     }
+    if (data.containsKey('cloud_owner_uid')) {
+      context.handle(
+        _cloudOwnerUidMeta,
+        cloudOwnerUid.isAcceptableOrUnknown(
+          data['cloud_owner_uid']!,
+          _cloudOwnerUidMeta,
+        ),
+      );
+    }
     if (data.containsKey('start_time')) {
       context.handle(
         _startTimeMeta,
@@ -538,6 +559,10 @@ class $RidesTable extends Rides with TableInfo<$RidesTable, Ride> {
         DriftSqlType.string,
         data['${effectivePrefix}cloud_ride_id'],
       ),
+      cloudOwnerUid: attachedDatabase.typeMapping.read(
+        DriftSqlType.string,
+        data['${effectivePrefix}cloud_owner_uid'],
+      ),
       startTime: attachedDatabase.typeMapping.read(
         DriftSqlType.dateTime,
         data['${effectivePrefix}start_time'],
@@ -640,6 +665,9 @@ class Ride extends DataClass implements Insertable<Ride> {
 
   /// Stable MotorCloud identity preserved across local IDs, reinstalls, and sync retries.
   final String? cloudRideId;
+
+  /// Firebase UID that owns this ride in MotorCloud. Null means device-only.
+  final String? cloudOwnerUid;
   final DateTime startTime;
   final DateTime? endTime;
   final double distanceMiles;
@@ -665,6 +693,7 @@ class Ride extends DataClass implements Insertable<Ride> {
   const Ride({
     required this.id,
     this.cloudRideId,
+    this.cloudOwnerUid,
     required this.startTime,
     this.endTime,
     required this.distanceMiles,
@@ -695,6 +724,9 @@ class Ride extends DataClass implements Insertable<Ride> {
     if (!nullToAbsent || cloudRideId != null) {
       map['cloud_ride_id'] = Variable<String>(cloudRideId);
     }
+    if (!nullToAbsent || cloudOwnerUid != null) {
+      map['cloud_owner_uid'] = Variable<String>(cloudOwnerUid);
+    }
     map['start_time'] = Variable<DateTime>(startTime);
     if (!nullToAbsent || endTime != null) {
       map['end_time'] = Variable<DateTime>(endTime);
@@ -742,6 +774,9 @@ class Ride extends DataClass implements Insertable<Ride> {
       cloudRideId: cloudRideId == null && nullToAbsent
           ? const Value.absent()
           : Value(cloudRideId),
+      cloudOwnerUid: cloudOwnerUid == null && nullToAbsent
+          ? const Value.absent()
+          : Value(cloudOwnerUid),
       startTime: Value(startTime),
       endTime: endTime == null && nullToAbsent
           ? const Value.absent()
@@ -791,6 +826,7 @@ class Ride extends DataClass implements Insertable<Ride> {
     return Ride(
       id: serializer.fromJson<int>(json['id']),
       cloudRideId: serializer.fromJson<String?>(json['cloudRideId']),
+      cloudOwnerUid: serializer.fromJson<String?>(json['cloudOwnerUid']),
       startTime: serializer.fromJson<DateTime>(json['startTime']),
       endTime: serializer.fromJson<DateTime?>(json['endTime']),
       distanceMiles: serializer.fromJson<double>(json['distanceMiles']),
@@ -823,6 +859,7 @@ class Ride extends DataClass implements Insertable<Ride> {
     return <String, dynamic>{
       'id': serializer.toJson<int>(id),
       'cloudRideId': serializer.toJson<String?>(cloudRideId),
+      'cloudOwnerUid': serializer.toJson<String?>(cloudOwnerUid),
       'startTime': serializer.toJson<DateTime>(startTime),
       'endTime': serializer.toJson<DateTime?>(endTime),
       'distanceMiles': serializer.toJson<double>(distanceMiles),
@@ -851,6 +888,7 @@ class Ride extends DataClass implements Insertable<Ride> {
   Ride copyWith({
     int? id,
     Value<String?> cloudRideId = const Value.absent(),
+    Value<String?> cloudOwnerUid = const Value.absent(),
     DateTime? startTime,
     Value<DateTime?> endTime = const Value.absent(),
     double? distanceMiles,
@@ -876,6 +914,9 @@ class Ride extends DataClass implements Insertable<Ride> {
   }) => Ride(
     id: id ?? this.id,
     cloudRideId: cloudRideId.present ? cloudRideId.value : this.cloudRideId,
+    cloudOwnerUid: cloudOwnerUid.present
+        ? cloudOwnerUid.value
+        : this.cloudOwnerUid,
     startTime: startTime ?? this.startTime,
     endTime: endTime.present ? endTime.value : this.endTime,
     distanceMiles: distanceMiles ?? this.distanceMiles,
@@ -913,6 +954,9 @@ class Ride extends DataClass implements Insertable<Ride> {
       cloudRideId: data.cloudRideId.present
           ? data.cloudRideId.value
           : this.cloudRideId,
+      cloudOwnerUid: data.cloudOwnerUid.present
+          ? data.cloudOwnerUid.value
+          : this.cloudOwnerUid,
       startTime: data.startTime.present ? data.startTime.value : this.startTime,
       endTime: data.endTime.present ? data.endTime.value : this.endTime,
       distanceMiles: data.distanceMiles.present
@@ -977,6 +1021,7 @@ class Ride extends DataClass implements Insertable<Ride> {
     return (StringBuffer('Ride(')
           ..write('id: $id, ')
           ..write('cloudRideId: $cloudRideId, ')
+          ..write('cloudOwnerUid: $cloudOwnerUid, ')
           ..write('startTime: $startTime, ')
           ..write('endTime: $endTime, ')
           ..write('distanceMiles: $distanceMiles, ')
@@ -1007,6 +1052,7 @@ class Ride extends DataClass implements Insertable<Ride> {
   int get hashCode => Object.hashAll([
     id,
     cloudRideId,
+    cloudOwnerUid,
     startTime,
     endTime,
     distanceMiles,
@@ -1036,6 +1082,7 @@ class Ride extends DataClass implements Insertable<Ride> {
       (other is Ride &&
           other.id == this.id &&
           other.cloudRideId == this.cloudRideId &&
+          other.cloudOwnerUid == this.cloudOwnerUid &&
           other.startTime == this.startTime &&
           other.endTime == this.endTime &&
           other.distanceMiles == this.distanceMiles &&
@@ -1063,6 +1110,7 @@ class Ride extends DataClass implements Insertable<Ride> {
 class RidesCompanion extends UpdateCompanion<Ride> {
   final Value<int> id;
   final Value<String?> cloudRideId;
+  final Value<String?> cloudOwnerUid;
   final Value<DateTime> startTime;
   final Value<DateTime?> endTime;
   final Value<double> distanceMiles;
@@ -1088,6 +1136,7 @@ class RidesCompanion extends UpdateCompanion<Ride> {
   const RidesCompanion({
     this.id = const Value.absent(),
     this.cloudRideId = const Value.absent(),
+    this.cloudOwnerUid = const Value.absent(),
     this.startTime = const Value.absent(),
     this.endTime = const Value.absent(),
     this.distanceMiles = const Value.absent(),
@@ -1114,6 +1163,7 @@ class RidesCompanion extends UpdateCompanion<Ride> {
   RidesCompanion.insert({
     this.id = const Value.absent(),
     this.cloudRideId = const Value.absent(),
+    this.cloudOwnerUid = const Value.absent(),
     required DateTime startTime,
     this.endTime = const Value.absent(),
     this.distanceMiles = const Value.absent(),
@@ -1140,6 +1190,7 @@ class RidesCompanion extends UpdateCompanion<Ride> {
   static Insertable<Ride> custom({
     Expression<int>? id,
     Expression<String>? cloudRideId,
+    Expression<String>? cloudOwnerUid,
     Expression<DateTime>? startTime,
     Expression<DateTime>? endTime,
     Expression<double>? distanceMiles,
@@ -1166,6 +1217,7 @@ class RidesCompanion extends UpdateCompanion<Ride> {
     return RawValuesInsertable({
       if (id != null) 'id': id,
       if (cloudRideId != null) 'cloud_ride_id': cloudRideId,
+      if (cloudOwnerUid != null) 'cloud_owner_uid': cloudOwnerUid,
       if (startTime != null) 'start_time': startTime,
       if (endTime != null) 'end_time': endTime,
       if (distanceMiles != null) 'distance_miles': distanceMiles,
@@ -1194,6 +1246,7 @@ class RidesCompanion extends UpdateCompanion<Ride> {
   RidesCompanion copyWith({
     Value<int>? id,
     Value<String?>? cloudRideId,
+    Value<String?>? cloudOwnerUid,
     Value<DateTime>? startTime,
     Value<DateTime?>? endTime,
     Value<double>? distanceMiles,
@@ -1220,6 +1273,7 @@ class RidesCompanion extends UpdateCompanion<Ride> {
     return RidesCompanion(
       id: id ?? this.id,
       cloudRideId: cloudRideId ?? this.cloudRideId,
+      cloudOwnerUid: cloudOwnerUid ?? this.cloudOwnerUid,
       startTime: startTime ?? this.startTime,
       endTime: endTime ?? this.endTime,
       distanceMiles: distanceMiles ?? this.distanceMiles,
@@ -1254,6 +1308,9 @@ class RidesCompanion extends UpdateCompanion<Ride> {
     if (cloudRideId.present) {
       map['cloud_ride_id'] = Variable<String>(cloudRideId.value);
     }
+    if (cloudOwnerUid.present) {
+      map['cloud_owner_uid'] = Variable<String>(cloudOwnerUid.value);
+    }
     if (startTime.present) {
       map['start_time'] = Variable<DateTime>(startTime.value);
     }
@@ -1328,6 +1385,7 @@ class RidesCompanion extends UpdateCompanion<Ride> {
     return (StringBuffer('RidesCompanion(')
           ..write('id: $id, ')
           ..write('cloudRideId: $cloudRideId, ')
+          ..write('cloudOwnerUid: $cloudOwnerUid, ')
           ..write('startTime: $startTime, ')
           ..write('endTime: $endTime, ')
           ..write('distanceMiles: $distanceMiles, ')
@@ -10030,6 +10088,7 @@ typedef $$RidesTableCreateCompanionBuilder =
     RidesCompanion Function({
       Value<int> id,
       Value<String?> cloudRideId,
+      Value<String?> cloudOwnerUid,
       required DateTime startTime,
       Value<DateTime?> endTime,
       Value<double> distanceMiles,
@@ -10057,6 +10116,7 @@ typedef $$RidesTableUpdateCompanionBuilder =
     RidesCompanion Function({
       Value<int> id,
       Value<String?> cloudRideId,
+      Value<String?> cloudOwnerUid,
       Value<DateTime> startTime,
       Value<DateTime?> endTime,
       Value<double> distanceMiles,
@@ -10224,6 +10284,11 @@ class $$RidesTableFilterComposer extends Composer<_$AppDatabase, $RidesTable> {
     builder: (column) => ColumnFilters(column),
   );
 
+  ColumnFilters<String> get cloudOwnerUid => $composableBuilder(
+    column: $table.cloudOwnerUid,
+    builder: (column) => ColumnFilters(column),
+  );
+
   ColumnFilters<DateTime> get startTime => $composableBuilder(
     column: $table.startTime,
     builder: (column) => ColumnFilters(column),
@@ -10504,6 +10569,11 @@ class $$RidesTableOrderingComposer
     builder: (column) => ColumnOrderings(column),
   );
 
+  ColumnOrderings<String> get cloudOwnerUid => $composableBuilder(
+    column: $table.cloudOwnerUid,
+    builder: (column) => ColumnOrderings(column),
+  );
+
   ColumnOrderings<DateTime> get startTime => $composableBuilder(
     column: $table.startTime,
     builder: (column) => ColumnOrderings(column),
@@ -10632,6 +10702,11 @@ class $$RidesTableAnnotationComposer
     builder: (column) => column,
   );
 
+  GeneratedColumn<String> get cloudOwnerUid => $composableBuilder(
+    column: $table.cloudOwnerUid,
+    builder: (column) => column,
+  );
+
   GeneratedColumn<DateTime> get startTime =>
       $composableBuilder(column: $table.startTime, builder: (column) => column);
 
@@ -10922,6 +10997,7 @@ class $$RidesTableTableManager
               ({
                 Value<int> id = const Value.absent(),
                 Value<String?> cloudRideId = const Value.absent(),
+                Value<String?> cloudOwnerUid = const Value.absent(),
                 Value<DateTime> startTime = const Value.absent(),
                 Value<DateTime?> endTime = const Value.absent(),
                 Value<double> distanceMiles = const Value.absent(),
@@ -10947,6 +11023,7 @@ class $$RidesTableTableManager
               }) => RidesCompanion(
                 id: id,
                 cloudRideId: cloudRideId,
+                cloudOwnerUid: cloudOwnerUid,
                 startTime: startTime,
                 endTime: endTime,
                 distanceMiles: distanceMiles,
@@ -10974,6 +11051,7 @@ class $$RidesTableTableManager
               ({
                 Value<int> id = const Value.absent(),
                 Value<String?> cloudRideId = const Value.absent(),
+                Value<String?> cloudOwnerUid = const Value.absent(),
                 required DateTime startTime,
                 Value<DateTime?> endTime = const Value.absent(),
                 Value<double> distanceMiles = const Value.absent(),
@@ -10999,6 +11077,7 @@ class $$RidesTableTableManager
               }) => RidesCompanion.insert(
                 id: id,
                 cloudRideId: cloudRideId,
+                cloudOwnerUid: cloudOwnerUid,
                 startTime: startTime,
                 endTime: endTime,
                 distanceMiles: distanceMiles,
diff --git a/lib/database/tables.dart b/lib/database/tables.dart
index 4410576..c5e5f77 100644
--- a/lib/database/tables.dart
+++ b/lib/database/tables.dart
@@ -4,6 +4,8 @@ class Rides extends Table {
   IntColumn get id => integer().autoIncrement()();
   /// Stable MotorCloud identity preserved across local IDs, reinstalls, and sync retries.
   TextColumn get cloudRideId => text().nullable()();
+  /// Firebase UID that owns this ride in MotorCloud. Null means device-only.
+  TextColumn get cloudOwnerUid => text().nullable()();
   DateTimeColumn get startTime => dateTime()();
   DateTimeColumn get endTime => dateTime().nullable()();
   RealColumn get distanceMiles => real().withDefault(const Constant(0.0))();
diff --git a/lib/features/settings/account_screen.dart b/lib/features/settings/account_screen.dart
index 22e31f9..6c49727 100644
--- a/lib/features/settings/account_screen.dart
+++ b/lib/features/settings/account_screen.dart
@@ -25,6 +25,7 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
 
   _AuthFormMode _formMode = _AuthFormMode.signIn;
   bool _obscurePassword = true;
+  bool _showAnonymousUpgrade = false;
   String? _statusMessage;
 
   @override
@@ -75,7 +76,7 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
                 isEvolution,
                 isWide,
               );
-            } else if (authState.isAnonymous) {
+            } else if (authState.isAnonymous && !_showAnonymousUpgrade) {
               content = _buildAnonymousView(
                 context,
                 authState.user!,
@@ -719,8 +720,7 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
                     'SIGN IN WITH FULL ACCOUNT',
                     style: TextStyle(fontWeight: FontWeight.bold),
                   ),
-                  onPressed: () =>
-                      ref.read(authNotifierProvider.notifier).signOut(),
+                  onPressed: () => setState(() => _showAnonymousUpgrade = true),
                 ),
               ),
             ],
@@ -803,7 +803,7 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
           const SizedBox(height: 12),
           if (!isAuthenticated) ...[
             const Text(
-              'Sign in to back up your rides and access multi-device synchronization. All rides are safely stored on this device in your local Drift SQLite database.',
+              'Sign in to MotorCloud to back up eligible rides and restore them on another device. Local rides remain available on this device.',
               style: TextStyle(
                 fontSize: 11,
                 color: Colors.white70,
@@ -891,7 +891,7 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
             ],
             _buildInfoRow(
               'Cloud Provider',
-              'Firebase (Auth/Firestore) + Cloudflare R2',
+              'MotorCloud backup',
             ),
             if (syncState.lastSuccessfulSync != null)
               _buildInfoRow(
@@ -1084,10 +1084,40 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
   Future<void> _handleBackupAllHistoricalRides() async {
     final db = ref.read(databaseProvider);
     final syncManager = ref.read(syncManagerProvider);
+    final user = ref.read(currentUserProvider);
+    if (user == null || user.isAnonymous) return;
     final rides = await db.select(db.rides).get();
+    final owned = rides.where((ride) => ride.cloudOwnerUid == user.uid).toList();
+    final unclaimed = rides.where((ride) => ride.cloudOwnerUid == null).toList();
+    final otherOwned = rides.length - owned.length - unclaimed.length;
+    var claimUnclaimed = false;
+    if (unclaimed.isNotEmpty && mounted) {
+      claimUnclaimed = await showDialog<bool>(
+            context: context,
+            builder: (context) => AlertDialog(
+              title: const Text('Back Up Device Rides?'),
+              content: Text(
+                'This will associate ${unclaimed.length} device-local ride(s) with your signed-in MotorCloud account. Rides already associated with another account will not be included.',
+              ),
+              actions: [
+                TextButton(onPressed: () => Navigator.pop(context, false), child: const Text('CANCEL')),
+                FilledButton(onPressed: () => Navigator.pop(context, true), child: const Text('BACK UP')),
+              ],
+            ),
+          ) ??
+          false;
+    }
 
-    int enqueued = 0;
-    for (final ride in rides) {
+    var enqueued = 0;
+    if (claimUnclaimed) {
+      for (final ride in unclaimed) {
+        if (await db.claimRideForCloudOwner(ride.id, user.uid)) {
+          await syncManager.enqueueRide(ride.id, autoProcess: false);
+          enqueued++;
+        }
+      }
+    }
+    for (final ride in owned) {
       await syncManager.enqueueRide(ride.id, autoProcess: false);
       enqueued++;
     }
@@ -1096,7 +1126,7 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
       ScaffoldMessenger.of(context).showSnackBar(
         SnackBar(
           content: Text(
-            'Enqueued $enqueued local ride(s) for MotorCloud synchronization.',
+            'Queued $enqueued ride(s). Skipped $otherOwned ride(s) associated with another account.',
           ),
           duration: const Duration(seconds: 3),
         ),
@@ -1227,7 +1257,7 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
                 ),
                 SizedBox(height: 2),
                 Text(
-                  'Your local Schema 5 Drift SQLite database remains the authoritative source of truth for telemetry and rides.',
+                  'Your local ride history remains available on this device. MotorCloud backup is optional and never required for recording or offline use.',
                   style: TextStyle(fontSize: 11, color: Colors.white60),
                 ),
               ],
@@ -1304,10 +1334,14 @@ class _AccountScreenState extends ConsumerState<AccountScreen> {
         displayName: displayName.isNotEmpty ? displayName : null,
       );
     } else if (_formMode == _AuthFormMode.forgotPassword) {
-      await notifier.sendPasswordResetEmail(email);
-      if (mounted) {
+      try {
+        await notifier.sendPasswordResetEmail(email);
+      } catch (_) {
+        return;
+      }
+      if (mounted && !ref.read(authNotifierProvider).hasError) {
         setState(() {
-          _statusMessage = 'Password reset instructions sent to $email';
+        _statusMessage = 'Password reset instructions sent. Check your email.';
         });
       }
     }
diff --git a/lib/services/auth/auth_service.dart b/lib/services/auth/auth_service.dart
index e118b7a..2ec3504 100644
--- a/lib/services/auth/auth_service.dart
+++ b/lib/services/auth/auth_service.dart
@@ -363,6 +363,7 @@ class FirebaseAuthService implements AuthService {
         user: _currentState.user,
         isFirebaseConfigured: true,
       ));
+      rethrow;
     }
   }
 
diff --git a/lib/services/sync/cloud_reconciliation_service.dart b/lib/services/sync/cloud_reconciliation_service.dart
index 97571db..6310bba 100644
--- a/lib/services/sync/cloud_reconciliation_service.dart
+++ b/lib/services/sync/cloud_reconciliation_service.dart
@@ -158,12 +158,16 @@ class CloudReconciliationService {
         final existingCloudId = legacyRows.first.data['cloud_ride_id'];
         if (existingCloudId == null || existingCloudId.toString().isEmpty) {
           await _db.customStatement(
-            'UPDATE rides SET cloud_ride_id = ? WHERE id = ?',
-            [cloudRideId, localRideId],
+            'UPDATE rides SET cloud_ride_id = ?, cloud_owner_uid = COALESCE(cloud_owner_uid, ?) WHERE id = ?',
+            [cloudRideId, ownerId, localRideId],
           );
           return const CloudReconciliationResult(unchanged: 1);
         }
         if (existingCloudId == cloudRideId) {
+          await _db.customStatement(
+            'UPDATE rides SET cloud_owner_uid = COALESCE(cloud_owner_uid, ?) WHERE id = ?',
+            [ownerId, localRideId],
+          );
           return const CloudReconciliationResult(unchanged: 1);
         }
         return const CloudReconciliationResult(conflicts: 1);
@@ -178,6 +182,7 @@ class CloudReconciliationService {
     final endTime = _readDateTime(data['endTime'] ?? data['endedAt']);
     await _insertRestoredMetadata(
       cloudRideId: cloudRideId,
+      ownerId: ownerId,
       startTime: startTime,
       endTime: endTime,
       data: data,
@@ -188,6 +193,7 @@ class CloudReconciliationService {
 
   Future<void> _insertRestoredMetadata({
     required String cloudRideId,
+    required String ownerId,
     required DateTime startTime,
     required DateTime? endTime,
     required Map<String, dynamic> data,
@@ -196,6 +202,7 @@ class CloudReconciliationService {
       '''
       INSERT INTO rides (
         cloud_ride_id,
+        cloud_owner_uid,
         start_time,
         end_time,
         distance_miles,
@@ -216,10 +223,11 @@ class CloudReconciliationService {
         motorcycle_make,
         motorcycle_model,
         motorcycle_variant
-      ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+      ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
     ''',
       [
         cloudRideId,
+        ownerId,
         startTime.toUtc().millisecondsSinceEpoch,
         endTime?.toUtc().millisecondsSinceEpoch,
         _asDouble(data['distanceMiles']),
diff --git a/lib/services/sync/firebase_sync_provider.dart b/lib/services/sync/firebase_sync_provider.dart
index 6db304f..73a3684 100644
--- a/lib/services/sync/firebase_sync_provider.dart
+++ b/lib/services/sync/firebase_sync_provider.dart
@@ -43,10 +43,19 @@ class FirebaseSyncProvider implements SyncProvider {
 
   @override
   Future<SyncResult> uploadRide(SyncItem item) async {
-    if (!await isAvailable()) return SyncResult.temporaryFailure('Firebase services are unavailable or unconfigured. Ride remains safely stored locally.');
     final user = _authService.currentUser;
     if (user == null || user.isAnonymous) return SyncResult.authRequired(message: 'Sign in to MotorCloud is required for cloud backup.');
 
+    final ride = await (_db.select(_db.rides)..where((r) => r.id.equals(item.localRideId))).getSingleOrNull();
+    if (ride != null && ride.cloudOwnerUid != user.uid) {
+      return SyncResult.permanentFailure(
+        ride.cloudOwnerUid == null
+            ? 'This device-only ride needs explicit approval before MotorCloud backup.'
+            : 'This ride belongs to another MotorCloud account and was not uploaded.',
+      );
+    }
+    if (!await isAvailable()) return SyncResult.temporaryFailure('Firebase services are unavailable or unconfigured. Ride remains safely stored locally.');
+
     // Refresh the Firebase ID token before a manual upload. This prevents a
     // recently completed sign-in from being rejected because the cached token
     // has not yet propagated through the app's auth abstraction.
diff --git a/lib/services/sync/sync_manager.dart b/lib/services/sync/sync_manager.dart
index b64fc29..786cf61 100644
--- a/lib/services/sync/sync_manager.dart
+++ b/lib/services/sync/sync_manager.dart
@@ -3,6 +3,8 @@ import 'package:flutter/widgets.dart';
 import 'sync_models.dart';
 import 'sync_outbox.dart';
 import 'sync_provider.dart';
+import '../../database/database.dart';
+import '../auth/auth_service.dart';
 
 /// Central provider-agnostic synchronization coordinator.
 ///
@@ -15,8 +17,10 @@ class SyncManager extends ChangeNotifier with WidgetsBindingObserver {
   String _activeProviderId = 'fake';
   bool _isProcessing = false;
   DateTime? Function() _nowProvider;
+  final AppDatabase? _db;
+  final AuthService? _authService;
 
-  SyncManager(this._outbox, {List<SyncProvider>? initialProviders, String? defaultProviderId, DateTime? Function()? nowProvider}) : _nowProvider = nowProvider ?? (() => DateTime.now()) {
+  SyncManager(this._outbox, {List<SyncProvider>? initialProviders, String? defaultProviderId, DateTime? Function()? nowProvider, this._db, this._authService}) : _nowProvider = nowProvider ?? (() => DateTime.now()) {
     if (initialProviders != null) {
       for (final p in initialProviders) { registerProvider(p); }
     }
@@ -61,6 +65,12 @@ class SyncManager extends ChangeNotifier with WidgetsBindingObserver {
 
   Future<SyncItem> enqueueRide(int localRideId, {String? targetProviderId, bool autoProcess = true}) async {
     final providerId = targetProviderId ?? _activeProviderId;
+    if (providerId == 'firebase') {
+      final user = _authService?.currentUser;
+      if (user != null && !user.isAnonymous && _db != null) {
+        await _db.claimRideForCloudOwner(localRideId, user.uid);
+      }
+    }
     final item = await _outbox.enqueue(localRideId, providerId, now: _now());
     notifyListeners();
     if (autoProcess) unawaited(processQueue());
diff --git a/lib/services/sync/sync_providers.dart b/lib/services/sync/sync_providers.dart
index 28195de..4f6aefd 100644
--- a/lib/services/sync/sync_providers.dart
+++ b/lib/services/sync/sync_providers.dart
@@ -79,6 +79,8 @@ final syncManagerProvider = ChangeNotifierProvider<SyncManager>((ref) {
       ref.watch(githubSyncProvider),
     ],
     defaultProviderId: 'firebase',
+    db: ref.watch(databaseProvider),
+    authService: ref.watch(authServiceProvider),
   );
   final accountSync = ref.watch(firebaseAccountSyncServiceProvider);
 
diff --git a/test/cloud_ride_identity_migration_test.dart b/test/cloud_ride_identity_migration_test.dart
index 59cab19..0dc2c0a 100644
--- a/test/cloud_ride_identity_migration_test.dart
+++ b/test/cloud_ride_identity_migration_test.dart
@@ -90,6 +90,7 @@ void main() {
 
     final migrated = await db.getCloudRideId(42);
     expect(migrated, 'ride_42_20260831_210705');
+    expect(await db.getCloudOwnerUid(42), isNull);
 
     final rows = await db.customSelect('PRAGMA table_info(rides)').get();
     expect(rows.any((row) => row.data['name'] == 'cloud_ride_id'), isTrue);
diff --git a/test/ownership_isolation_test.dart b/test/ownership_isolation_test.dart
new file mode 100644
index 0000000..73e151a
--- /dev/null
+++ b/test/ownership_isolation_test.dart
@@ -0,0 +1,100 @@
+import 'package:drift/native.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+import 'package:motorcycle_dash/database/database.dart';
+import 'package:motorcycle_dash/services/auth/auth_service.dart';
+import 'package:motorcycle_dash/services/auth/auth_state.dart';
+import 'package:motorcycle_dash/services/auth/auth_user.dart';
+import 'package:motorcycle_dash/services/sync/sync_manager.dart';
+import 'package:motorcycle_dash/services/sync/sync_outbox.dart';
+import 'package:motorcycle_dash/services/sync/sync_provider.dart';
+import 'package:motorcycle_dash/services/sync/sync_models.dart';
+import 'package:motorcycle_dash/services/sync/firebase_sync_provider.dart';
+
+class _Auth implements AuthService {
+  AuthUser? user;
+  @override bool get isConfigured => true;
+  @override AuthUser? get currentUser => user;
+  @override AuthState get currentState => user == null ? const AuthState.unauthenticated() : AuthState.authenticated(user!);
+  @override Stream<AuthState> get authStateChanges => Stream.value(currentState);
+  @override Future<void> createUserWithEmailAndPassword(String e, String p, {String? displayName}) async {}
+  @override Future<void> sendPasswordResetEmail(String email) async {}
+  @override Future<void> signInAnonymously() async {}
+  @override Future<void> signInWithEmailAndPassword(String e, String p) async {}
+  @override Future<void> signInWithGoogle() async {}
+  @override Future<String?> getIdToken([bool forceRefresh = false]) async => user == null ? null : 'token';
+  @override Future<void> signOut() async { user = null; }
+  @override void dispose() {}
+}
+
+void main() {
+  TestWidgetsFlutterBinding.ensureInitialized();
+
+  test('new rides are unclaimed and claim is immutable', () async {
+    final db = AppDatabase.forTesting(NativeDatabase.memory());
+    addTearDown(db.close);
+    final rideId = await db.startRide();
+    expect(await db.getCloudOwnerUid(rideId), isNull);
+    expect(await db.claimRideForCloudOwner(rideId, 'user_a'), isTrue);
+    expect(await db.getCloudOwnerUid(rideId), 'user_a');
+    expect(await db.claimRideForCloudOwner(rideId, 'user_b'), isFalse);
+    expect(await db.getCloudOwnerUid(rideId), 'user_a');
+    expect(await db.getCloudRideId(rideId), startsWith('ride_'));
+  });
+
+  test('authenticated enqueue claims only for the current permanent account', () async {
+    SharedPreferences.setMockInitialValues({});
+    final prefs = await SharedPreferences.getInstance();
+    final db = AppDatabase.forTesting(NativeDatabase.memory());
+    addTearDown(db.close);
+    final auth = _Auth()..user = const AuthUser(uid: 'user_a', email: 'a@test.com');
+    final rideId = await db.startRide();
+    final manager = SyncManager(
+      SyncOutbox(prefs),
+      db: db,
+      authService: auth,
+      initialProviders: [FakeSyncProvider(providerId: 'firebase')],
+      defaultProviderId: 'firebase',
+    );
+    addTearDown(manager.dispose);
+
+    await manager.enqueueRide(rideId, autoProcess: false);
+    expect(await db.getCloudOwnerUid(rideId), 'user_a');
+
+    auth.user = const AuthUser(uid: 'user_b', email: 'b@test.com');
+    await manager.enqueueRide(rideId, autoProcess: false);
+    expect(await db.getCloudOwnerUid(rideId), 'user_a');
+  });
+
+  test('signed-out enqueue leaves ride unclaimed', () async {
+    SharedPreferences.setMockInitialValues({});
+    final prefs = await SharedPreferences.getInstance();
+    final db = AppDatabase.forTesting(NativeDatabase.memory());
+    addTearDown(db.close);
+    final rideId = await db.startRide();
+    final manager = SyncManager(
+      SyncOutbox(prefs),
+      db: db,
+      authService: _Auth(),
+      initialProviders: [FakeSyncProvider(providerId: 'firebase')],
+      defaultProviderId: 'firebase',
+    );
+    addTearDown(manager.dispose);
+    await manager.enqueueRide(rideId, autoProcess: false);
+    expect(await db.getCloudOwnerUid(rideId), isNull);
+  });
+
+  test('Firebase provider rejects another account before any cloud call', () async {
+    final db = AppDatabase.forTesting(NativeDatabase.memory());
+    addTearDown(db.close);
+    final rideId = await db.startRide();
+    await db.claimRideForCloudOwner(rideId, 'user_a');
+    final auth = _Auth()..user = const AuthUser(uid: 'user_b', email: 'b@test.com');
+    final result = await FirebaseSyncProvider(db: db, authService: auth).uploadRide(
+      SyncItem(localRideId: rideId, providerId: 'firebase', createdAt: DateTime.now()),
+    );
+    expect(result.success, isFalse);
+    expect(result.isRetryable, isFalse);
+    expect(await db.getCloudOwnerUid(rideId), 'user_a');
+  });
+}