Summarize repo changes

lib/providers/connection_provider.dart

@@ -264,7 +264,6 @@ class ConnectionProvider with ChangeNotifier {
 
       try {
         await _activeService.addOrUpdateContact(pendingOp.contact!);
-        await Future.delayed(const Duration(milliseconds: 300));
 
         if (pendingOp.messageId != null) {
           _messageDeliveryTracker.trackPendingDirectMessage(
@@ -1272,12 +1271,11 @@ class ConnectionProvider with ChangeNotifier {
         '⚠️ [ConnectionProvider] Rate limit hit: $pendingCount pending ACKs (max 7)',
       );
       debugPrint(
-        '⚠️ Firmware only tracks 8 ACKs - waiting for delivery confirmations...',
+        '⚠️ Firmware only tracks 8 ACKs - waiting for delivery confirmation...',
       );
 
-      // Wait briefly for some ACKs to arrive, then proceed anyway
-      // (User action shouldn't be blocked forever)
-      await Future.delayed(const Duration(milliseconds: 500));
+      // Wait for a slot to free up (delivery/timeout), max 500ms
+      await _messageDeliveryTracker.waitForSlot();
 
       if (_messageDeliveryTracker.shouldRateLimit) {
         debugPrint(
@@ -1353,30 +1351,14 @@ class ConnectionProvider with ChangeNotifier {
         attempt: retryAttempt,
       );
 
-      if (messageId != null) {
-        Future.delayed(const Duration(milliseconds: 350), () {
-          if (_messageDeliveryTracker.hasAckForMessage(messageId)) {
-            return;
-          }
-
-          debugPrint(
-            'ℹ️ [ConnectionProvider] Missing RESP_CODE_SENT for $messageId; promoting to sent via fallback',
-          );
-          onMessageSent?.call(messageId, 0, 0);
-        });
-      }
-
-      // Clear pending operation after successful send (no error)
-      // If ERR_CODE_NOT_FOUND occurs, the operation will be recovered automatically
+      // Clear pending operation — any ERR_CODE_NOT_FOUND has already been
+      // handled synchronously by onContactNotFound before sendTextMessage returns.
       if (effectiveContact != null) {
         final operationId = contactPublicKey
             .sublist(0, 6)
             .map((b) => b.toRadixString(16).padLeft(2, '0'))
             .join(':');
-        // Use a small delay to allow error response to arrive before clearing
-        Future.delayed(const Duration(milliseconds: 500), () {
-          _pendingSendOperations.remove(operationId);
-        });
+        _pendingSendOperations.remove(operationId);
       }
 
       return true;

lib/providers/helpers/message_delivery_tracker.dart

@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:typed_data';
 
 /// Message delivery tracking helper
@@ -30,6 +31,9 @@ class MessageDeliveryTracker {
   /// Map of ACK tag to timestamp for timeout cleanup
   final Map<int, DateTime> _ackTagTimestamps = {};
 
+  /// Completer signalled when a pending ACK slot is freed (delivery or removal).
+  Completer<void>? _slotFreedCompleter;
+
   /// Track a pending message ID before sending
   ///
   /// This is called BEFORE sending the message. When RESP_CODE_SENT
@@ -112,6 +116,7 @@ class MessageDeliveryTracker {
       _messageIdToAckTag.remove(messageId);
     }
     _ackTagTimestamps.remove(ackCode);
+    _notifySlotFreed();
   }
 
   /// Remove ACK tag mapping by message ID
@@ -122,6 +127,7 @@ class MessageDeliveryTracker {
     if (ackTag != null) {
       _ackTagToMessageId.remove(ackTag);
       _ackTagTimestamps.remove(ackTag);
+      _notifySlotFreed();
     }
     _pendingMessageIds.remove(messageId);
     final emptyKeys = <String>[];
@@ -166,6 +172,7 @@ class MessageDeliveryTracker {
     _ackTagToMessageId.clear();
     _messageIdToAckTag.clear();
     _ackTagTimestamps.clear();
+    _notifySlotFreed();
   }
 
   /// Get count of pending ACK tags
@@ -179,6 +186,27 @@ class MessageDeliveryTracker {
   /// Returns true if >= 7 pending ACKs (stay under firmware limit of 8)
   bool get shouldRateLimit => pendingCount >= 7;
 
+  /// Wait until a pending ACK slot is freed, or [timeout] elapses.
+  ///
+  /// Returns immediately if not at the rate limit.
+  Future<void> waitForSlot({
+    Duration timeout = const Duration(milliseconds: 500),
+  }) async {
+    if (!shouldRateLimit) return;
+    _slotFreedCompleter ??= Completer<void>();
+    await _slotFreedCompleter!.future.timeout(
+      timeout,
+      onTimeout: () {},
+    );
+  }
+
+  void _notifySlotFreed() {
+    if (_slotFreedCompleter != null && !_slotFreedCompleter!.isCompleted) {
+      _slotFreedCompleter!.complete();
+    }
+    _slotFreedCompleter = null;
+  }
+
   /// Get oldest pending ACK timestamp (for debugging)
   DateTime? get oldestPendingTimestamp {
     if (_ackTagTimestamps.isEmpty) return null;