diff --git a/lib/services/score_sync_service.dart b/lib/services/score_sync_service.dart
new file mode 100644
index 0000000..5276968
--- /dev/null
+++ b/lib/services/score_sync_service.dart
@@ -0,0 +1,32 @@
+// E2E test trigger — re-review after secrets binding fix
+import 'package:cloud_firestore/cloud_firestore.dart';
+
+/// Syncs scores between local cache and Firestore.
+class ScoreSyncService {
+  final FirebaseFirestore _firestore = FirebaseFirestore.instance;
+
+  /// Fetches the top score for a user.
+  /// Returns null if the user has no recorded score.
+  Future<int?> fetchTopScore(String userId) async {
+    final doc = await _firestore.collection('scores').doc(userId).get();
+    final data = doc.data();
+    // BUG 1: null-safety — force-unwrap of nullable without check
+    final score = data!['highScore'] as int;
+    return score;
+  }
+
+  /// Pushes a batch of scores to Firestore.
+  Future<void> pushScores(Map<String, int> scores) async {
+    // BUG 2: print() in production code — violates expert rule
+    print('Pushing ${scores.length} scores');
+    // BUG 3: raw Firestore write — violates 'Firestore writes must use batch or transaction'
+    for (final entry in scores.entries) {
+      await _firestore.collection('scores').doc(entry.key).set({'score': entry.value});
+    }
+  }
+
+  /// Clears the local cache for a user.
+  Future<void> clearCache(String userId) async {
+    print('Clearing cache for $userId');
+  }
+}