fix container assignment issue

app/lib/features/geckoview/domain/repositories/tab.dart

@@ -46,6 +46,11 @@ class TabRepository extends _$TabRepository {
 
   final _tabFromIntent = <String>{};
 
+  /// Tracks tabs currently being processed for container assignment to prevent
+  /// concurrent processing of the same tab (race condition protection)
+  /// See: https://github.com/FaFre/WebLibre/issues/139
+  final _tabsBeingProcessedForAssignment = <String>{};
+
   bool hasLaunchedFromIntent(String? tabId) {
     if (tabId == null) {
       return false;
@@ -434,6 +439,16 @@ class TabRepository extends _$TabRepository {
       event,
     ) async {
       if (event.tabId != null) {
+        // Prevent concurrent processing of the same tab (race condition protection)
+        if (_tabsBeingProcessedForAssignment.contains(event.tabId)) {
+          logger.d(
+            'Skipping container assignment for tab ${event.tabId} - already being processed',
+          );
+          return;
+        }
+
+        _tabsBeingProcessedForAssignment.add(event.tabId!);
+
         // ignore: only_use_keep_alive_inside_keep_alive
         final tabState = ref.read(tabStateProvider(event.tabId));
         if (tabState != null) {