Add voice image packet retry

lib/providers/app_provider.dart

@@ -47,6 +47,15 @@ class AppProvider with ChangeNotifier {
   bool _isVoiceLimiterEnabled = true;
   bool get isVoiceLimiterEnabled => _isVoiceLimiterEnabled;
 
+  static const Duration _packetRetryDelay = Duration(milliseconds: 1200);
+  static const int _maxPacketRetryAttempts = 4;
+  final Map<String, String> _voiceSessionSenderKey6 = {};
+  final Map<String, String> _imageSessionSenderKey6 = {};
+  final Map<String, Timer> _voiceMissingRetryTimers = {};
+  final Map<String, Timer> _imageMissingRetryTimers = {};
+  final Map<String, int> _voiceMissingRetryAttempts = {};
+  final Map<String, int> _imageMissingRetryAttempts = {};
+
   AppProvider({
     required this.connectionProvider,
     required this.contactsProvider,
@@ -472,6 +481,9 @@ class AppProvider with ChangeNotifier {
           voiceProvider.serveSessionTo(
             sessionId: voiceFetchRequest.sessionId,
             requester: requester,
+            requestedIndices: voiceFetchRequest.want == 'missing'
+                ? voiceFetchRequest.missingIndices.toSet()
+                : null,
           ),
         );
         return;
@@ -519,6 +531,9 @@ class AppProvider with ChangeNotifier {
       // Voice envelope message (new public/direct on-demand format).
       final voiceEnvelope = VoiceEnvelope.tryParseText(enrichedMessage.text);
       if (voiceEnvelope != null) {
+        _voiceSessionSenderKey6[voiceEnvelope.sessionId] = voiceEnvelope
+            .senderKey6
+            .toLowerCase();
         enrichedMessage = enrichedMessage.copyWith(
           isVoice: true,
           voiceId: voiceEnvelope.sessionId,
@@ -544,7 +559,9 @@ class AppProvider with ChangeNotifier {
       }
 
       // Image fetch request (IR1): requester asks us to stream image fragments.
-      final imageFetchRequest = ImageFetchRequest.tryParse(enrichedMessage.text);
+      final imageFetchRequest = ImageFetchRequest.tryParse(
+        enrichedMessage.text,
+      );
       if (imageFetchRequest != null) {
         final senderPrefix = enrichedMessage.senderPublicKeyPrefix;
         if (senderPrefix != null) {
@@ -562,6 +579,9 @@ class AppProvider with ChangeNotifier {
                 imageProvider.serveSessionTo(
                   sessionId: imageFetchRequest.sessionId,
                   requester: requester,
+                  requestedIndices: imageFetchRequest.want == 'missing'
+                      ? imageFetchRequest.missingIndices.toSet()
+                      : null,
                 ),
               );
             }
@@ -573,6 +593,9 @@ class AppProvider with ChangeNotifier {
       // Image envelope (IE1): announce image availability.
       final imageEnvelope = ImageEnvelope.tryParse(enrichedMessage.text);
       if (imageEnvelope != null) {
+        _imageSessionSenderKey6[imageEnvelope.sessionId] = imageEnvelope
+            .senderKey6
+            .toLowerCase();
         imageProvider.registerEnvelope(imageEnvelope);
         messagesProvider.addMessage(
           enrichedMessage,
@@ -660,11 +683,12 @@ class AppProvider with ChangeNotifier {
         if (frag == null) return;
         debugPrint('📷 [AppProvider] Binary image fragment received: $frag');
         final session = imageProvider.session(frag.sessionId);
-        imageProvider.addFragment(
+        final justComplete = imageProvider.addFragment(
           frag,
           width: session?.width ?? 0,
           height: session?.height ?? 0,
         );
+        _scheduleImageMissingRetry(frag.sessionId, justComplete: justComplete);
         return;
       }
 
@@ -673,6 +697,7 @@ class AppProvider with ChangeNotifier {
       if (pkt == null) return;
       debugPrint('🎙️ [AppProvider] Binary voice packet received: $pkt');
       final justComplete = voiceProvider.addPacket(pkt);
+      _scheduleVoiceMissingRetry(pkt.sessionId, justComplete: justComplete);
       // Insert or update the placeholder message in the chat list
       _handleIncomingVoicePacket(pkt, justComplete: justComplete);
     };
@@ -990,6 +1015,158 @@ class AppProvider with ChangeNotifier {
     }
   }
 
+  Contact? _resolveContactByPrefixHex(String prefixHex) {
+    if (prefixHex.length != 12) return null;
+    return contactsProvider.findContactByPrefixHex(prefixHex.toLowerCase());
+  }
+
+  void _scheduleVoiceMissingRetry(
+    String sessionId, {
+    required bool justComplete,
+  }) {
+    if (justComplete || voiceProvider.isComplete(sessionId)) {
+      _voiceMissingRetryTimers.remove(sessionId)?.cancel();
+      _voiceMissingRetryAttempts.remove(sessionId);
+      return;
+    }
+
+    _voiceMissingRetryAttempts[sessionId] = 0;
+    _voiceMissingRetryTimers[sessionId]?.cancel();
+    _voiceMissingRetryTimers[sessionId] = Timer(_packetRetryDelay, () {
+      unawaited(_requestMissingVoicePackets(sessionId));
+    });
+  }
+
+  Future<void> _requestMissingVoicePackets(String sessionId) async {
+    if (voiceProvider.isComplete(sessionId)) {
+      _voiceMissingRetryTimers.remove(sessionId)?.cancel();
+      _voiceMissingRetryAttempts.remove(sessionId);
+      return;
+    }
+
+    final attempt = _voiceMissingRetryAttempts[sessionId] ?? 0;
+    if (attempt >= _maxPacketRetryAttempts) {
+      debugPrint(
+        '⚠️ [AppProvider] Voice re-request limit reached for $sessionId',
+      );
+      _voiceMissingRetryTimers.remove(sessionId)?.cancel();
+      return;
+    }
+
+    final senderKey6 = _voiceSessionSenderKey6[sessionId];
+    if (senderKey6 == null) return;
+    final sender = _resolveContactByPrefixHex(senderKey6);
+    final deviceKey = connectionProvider.deviceInfo.publicKey;
+    if (sender == null || deviceKey == null || deviceKey.length < 6) return;
+
+    final missing = voiceProvider.missingPacketIndices(sessionId);
+    if (missing.isEmpty) {
+      _voiceMissingRetryTimers.remove(sessionId)?.cancel();
+      _voiceMissingRetryAttempts.remove(sessionId);
+      return;
+    }
+
+    final requesterKey6 = deviceKey
+        .sublist(0, 6)
+        .map((b) => b.toRadixString(16).padLeft(2, '0'))
+        .join('');
+
+    final request = VoiceFetchRequest(
+      sessionId: sessionId,
+      want: 'missing',
+      missingIndices: missing,
+      requesterKey6: requesterKey6,
+      timestampSec: DateTime.now().millisecondsSinceEpoch ~/ 1000,
+      version: 1,
+    );
+
+    final sent = await connectionProvider.sendTextMessage(
+      contactPublicKey: sender.publicKey,
+      text: request.encodeText(),
+      contact: sender,
+    );
+    if (!sent) return;
+
+    _voiceMissingRetryAttempts[sessionId] = attempt + 1;
+    _voiceMissingRetryTimers[sessionId]?.cancel();
+    _voiceMissingRetryTimers[sessionId] = Timer(_packetRetryDelay, () {
+      unawaited(_requestMissingVoicePackets(sessionId));
+    });
+  }
+
+  void _scheduleImageMissingRetry(
+    String sessionId, {
+    required bool justComplete,
+  }) {
+    if (justComplete || imageProvider.isComplete(sessionId)) {
+      _imageMissingRetryTimers.remove(sessionId)?.cancel();
+      _imageMissingRetryAttempts.remove(sessionId);
+      return;
+    }
+
+    _imageMissingRetryAttempts[sessionId] = 0;
+    _imageMissingRetryTimers[sessionId]?.cancel();
+    _imageMissingRetryTimers[sessionId] = Timer(_packetRetryDelay, () {
+      unawaited(_requestMissingImageFragments(sessionId));
+    });
+  }
+
+  Future<void> _requestMissingImageFragments(String sessionId) async {
+    if (imageProvider.isComplete(sessionId)) {
+      _imageMissingRetryTimers.remove(sessionId)?.cancel();
+      _imageMissingRetryAttempts.remove(sessionId);
+      return;
+    }
+
+    final attempt = _imageMissingRetryAttempts[sessionId] ?? 0;
+    if (attempt >= _maxPacketRetryAttempts) {
+      debugPrint(
+        '⚠️ [AppProvider] Image re-request limit reached for $sessionId',
+      );
+      _imageMissingRetryTimers.remove(sessionId)?.cancel();
+      return;
+    }
+
+    final senderKey6 = _imageSessionSenderKey6[sessionId];
+    if (senderKey6 == null) return;
+    final sender = _resolveContactByPrefixHex(senderKey6);
+    final deviceKey = connectionProvider.deviceInfo.publicKey;
+    if (sender == null || deviceKey == null || deviceKey.length < 6) return;
+
+    final missing = imageProvider.missingFragmentIndices(sessionId);
+    if (missing.isEmpty) {
+      _imageMissingRetryTimers.remove(sessionId)?.cancel();
+      _imageMissingRetryAttempts.remove(sessionId);
+      return;
+    }
+
+    final requesterKey6 = deviceKey
+        .sublist(0, 6)
+        .map((b) => b.toRadixString(16).padLeft(2, '0'))
+        .join('');
+
+    final request = ImageFetchRequest(
+      sessionId: sessionId,
+      want: 'missing',
+      missingIndices: missing,
+      requesterKey6: requesterKey6,
+      timestampSec: DateTime.now().millisecondsSinceEpoch ~/ 1000,
+    );
+
+    final sent = await connectionProvider.sendTextMessage(
+      contactPublicKey: sender.publicKey,
+      text: request.encode(),
+      contact: sender,
+    );
+    if (!sent) return;
+
+    _imageMissingRetryAttempts[sessionId] = attempt + 1;
+    _imageMissingRetryTimers[sessionId]?.cancel();
+    _imageMissingRetryTimers[sessionId] = Timer(_packetRetryDelay, () {
+      unawaited(_requestMissingImageFragments(sessionId));
+    });
+  }
+
   /// Insert or update a voice placeholder message for binary raw-data packets.
   ///
   /// Binary voice packets arrive without a chat message, so we synthesise one
@@ -1120,6 +1297,18 @@ class AppProvider with ChangeNotifier {
     messagesProvider.clearAll();
     unawaited(voiceProvider.clearStoredVoiceData());
     unawaited(imageProvider.clearAll());
+    for (final timer in _voiceMissingRetryTimers.values) {
+      timer.cancel();
+    }
+    for (final timer in _imageMissingRetryTimers.values) {
+      timer.cancel();
+    }
+    _voiceMissingRetryTimers.clear();
+    _imageMissingRetryTimers.clear();
+    _voiceMissingRetryAttempts.clear();
+    _imageMissingRetryAttempts.clear();
+    _voiceSessionSenderKey6.clear();
+    _imageSessionSenderKey6.clear();
     notifyListeners();
   }
 
@@ -1148,6 +1337,12 @@ class AppProvider with ChangeNotifier {
     locationTrackingService.onTrackingStateChanged = null;
     // Dispose the location tracking service to stop GPS stream and clean up resources
     locationTrackingService.dispose();
+    for (final timer in _voiceMissingRetryTimers.values) {
+      timer.cancel();
+    }
+    for (final timer in _imageMissingRetryTimers.values) {
+      timer.cancel();
+    }
     super.dispose();
   }
 }

lib/providers/image_provider.dart

@@ -1,6 +1,5 @@
 import 'dart:async';
 import 'dart:convert';
-import 'dart:typed_data';
 import 'package:flutter/foundation.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import '../models/contact.dart';
@@ -63,6 +62,16 @@ class ImageProvider with ChangeNotifier {
       _sessions[sessionId]?.isComplete ?? false;
   bool hasOutgoing(String sessionId) => _outgoing.containsKey(sessionId);
 
+  List<int> missingFragmentIndices(String sessionId) {
+    final session = _sessions[sessionId];
+    if (session == null) return const [];
+    final missing = <int>[];
+    for (var i = 0; i < session.total; i++) {
+      if (session.fragments[i] == null) missing.add(i);
+    }
+    return missing;
+  }
+
   // ── Incoming fragment reception ──────────────────────────────────────────
 
   /// Add a received [fragment].  Creates the session on first fragment using
@@ -166,6 +175,7 @@ class ImageProvider with ChangeNotifier {
   Future<bool> serveSessionTo({
     required String sessionId,
     required Contact requester,
+    Set<int>? requestedIndices,
   }) async {
     final cached = _outgoing[sessionId];
     if (cached == null) {
@@ -177,13 +187,15 @@ class ImageProvider with ChangeNotifier {
       return false;
     }
     if (requester.outPathLen < 0) {
-      debugPrint(
+      debugPrint('⚠️ [ImageProvider] ${requester.advName} has no direct path');
-        '⚠️ [ImageProvider] ${requester.advName} has no direct path',
-      );
       return false;
     }
 
     for (final fragment in cached.fragments) {
+      if (requestedIndices != null &&
+          !requestedIndices.contains(fragment.index)) {
+        continue;
+      }
       try {
         await sendRawPacketCallback!(
           contactPath: requester.outPath,
@@ -217,9 +229,7 @@ class ImageProvider with ChangeNotifier {
 
   void _evictExpiredOutgoing() {
     final now = DateTime.now();
-    _outgoing.removeWhere(
+    _outgoing.removeWhere((_, s) => now.difference(s.cachedAt) > _outgoingTtl);
-      (_, s) => now.difference(s.cachedAt) > _outgoingTtl,
-    );
   }
 
   Future<void> _persist() async {
@@ -237,9 +247,7 @@ class ImageProvider with ChangeNotifier {
                 'height': s.height,
                 'fragments': s.fragments
                     .map(
-                      (f) => f == null
+                      (f) => f == null ? null : base64.encode(f.encodeBinary()),
-                          ? null
-                          : base64.encode(f.encodeBinary()),
                     )
                     .toList(),
               },

lib/providers/voice_provider.dart

@@ -93,6 +93,16 @@ class VoiceProvider with ChangeNotifier {
   bool hasOutgoingSession(String sessionId) =>
       _outgoingSessions.containsKey(sessionId);
 
+  List<int> missingPacketIndices(String sessionId) {
+    final session = _sessions[sessionId];
+    if (session == null) return const [];
+    final missing = <int>[];
+    for (var i = 0; i < session.total; i++) {
+      if (session.packets[i] == null) missing.add(i);
+    }
+    return missing;
+  }
+
   // ── Packet reception ─────────────────────────────────────────────────────
 
   /// Add an incoming [packet] to its session.  Creates the session on first packet.
@@ -132,6 +142,7 @@ class VoiceProvider with ChangeNotifier {
   Future<bool> serveSessionTo({
     required String sessionId,
     required Contact requester,
+    Set<int>? requestedIndices,
   }) async {
     final cached = _outgoingSessions[sessionId];
     if (cached == null) {
@@ -152,6 +163,10 @@ class VoiceProvider with ChangeNotifier {
     }
 
     for (final packet in cached.packets) {
+      if (requestedIndices != null &&
+          !requestedIndices.contains(packet.index)) {
+        continue;
+      }
       try {
         await sendRawPacketCallback!(
           contactPath: requester.outPath,
@@ -229,9 +244,7 @@ class VoiceProvider with ChangeNotifier {
                 'sessionId': session.sessionId,
                 'modeId': session.mode.id,
                 'total': session.total,
-                'packets': session.packets
+                'packets': session.packets.map((p) => p?.encodeText()).toList(),
-                    .map((p) => p?.encodeText())
-                    .toList(),
               },
             )
             .toList(),
@@ -264,7 +277,10 @@ class VoiceProvider with ChangeNotifier {
         final sessionId = map['sessionId'] as String?;
         final modeId = map['modeId'] as int?;
         final total = map['total'] as int?;
-        if (sessionId == null || modeId == null || total == null || total <= 0) {
+        if (sessionId == null ||
+            modeId == null ||
+            total == null ||
+            total <= 0) {
           continue;
         }
         final mode = VoicePacketMode.fromId(modeId);
@@ -325,8 +341,5 @@ class _OutgoingVoiceSession {
   final String sessionId;
   final List<VoicePacket> packets;
 
-  const _OutgoingVoiceSession({
+  const _OutgoingVoiceSession({required this.sessionId, required this.packets});
-    required this.sessionId,
-    required this.packets,
-  });
 }

lib/screens/messages_tab.dart

@@ -446,13 +446,15 @@ class _MessagesTabState extends State<MessagesTab> {
 
     setState(() => _isSendingImage = true);
     try {
-      // Compress to grayscale AVIF using user-selected size and compression.
+      // Compress AVIF using user-selected size, compression and color mode.
       final maxSize = await ImagePreferences.getMaxSize();
       final compression = await ImagePreferences.getCompression();
+      final grayscale = await ImagePreferences.getGrayscale();
       final result = await ImageCodecService.compress(
         rawBytes,
         maxDimension: maxSize,
         compression: compression,
+        grayscale: grayscale,
       );
       if (result == null) {
         ToastLogger.error(context, 'Image compression failed');
@@ -467,10 +469,21 @@ class _MessagesTabState extends State<MessagesTab> {
       ).join();
 
       // Fragment.
+      var imageDataBytesPerFragment = ImagePacket.maxDataBytes;
+      if (_destinationType ==
+              MessageDestinationPreferences.destinationTypeContact &&
+          _selectedRecipient != null &&
+          _selectedRecipient!.outPathLen >= 0) {
+        imageDataBytesPerFragment = safeImageDataBytesForPath(
+          _selectedRecipient!.outPathLen,
+        );
+      }
+
       final fragments = fragmentImage(
         sessionId: sessionId,
         format: ImageFormat.avif,
         bytes: compressed,
+        maxDataBytes: imageDataBytesPerFragment,
       );
 
       if (fragments.isEmpty) {
@@ -548,7 +561,8 @@ class _MessagesTabState extends State<MessagesTab> {
 
       debugPrint(
         '📷 [Image] Sent IE1 for session $sessionId: '
-        '${fragments.length} fragments, ${compressed.length}B',
+        '${fragments.length} fragments, ${compressed.length}B, '
+        'chunk=${imageDataBytesPerFragment}B',
       );
     } catch (e, st) {
       debugPrint('❌ [Image] _pickAndSendImage: $e\n$st');

lib/screens/settings_screen.dart

@@ -50,6 +50,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
   int _voiceBitrate = VoiceBitratePreferences.defaultBitrate;
   int _imageMaxSize = ImagePreferences.defaultMaxSize;
   int _imageCompression = ImagePreferences.defaultQuality;
+  bool _imageGrayscale = ImagePreferences.defaultGrayscale;
   final LocationTrackingService _locationService = LocationTrackingService();
 
   @override
@@ -119,10 +120,12 @@ class _SettingsScreenState extends State<SettingsScreen> {
   Future<void> _loadImagePreferences() async {
     final size = await ImagePreferences.getMaxSize();
     final compression = await ImagePreferences.getCompression();
+    final grayscale = await ImagePreferences.getGrayscale();
     if (!mounted) return;
     setState(() {
       _imageMaxSize = size;
       _imageCompression = compression;
+      _imageGrayscale = grayscale;
     });
   }
 
@@ -695,6 +698,18 @@ class _SettingsScreenState extends State<SettingsScreen> {
               onChangeEnd: (v) => _saveImageCompression(v.round()),
             ),
           ),
+          SwitchListTile(
+            secondary: const Icon(Icons.invert_colors),
+            title: const Text('Grayscale'),
+            subtitle: const Text(
+              'Converts image to grayscale for smaller file size',
+            ),
+            value: _imageGrayscale,
+            onChanged: (value) async {
+              await ImagePreferences.setGrayscale(value);
+              setState(() => _imageGrayscale = value);
+            },
+          ),
           const Divider(),
 
           // Templates Section

lib/services/image_codec_service.dart

@@ -21,6 +21,7 @@ class ImageCodecService {
     Uint8List rawBytes, {
     int maxDimension = 256,
     int compression = 90,
+    bool grayscale = true,
   }) async {
     try {
       // 1a. Probe original dimensions (no resize).
@@ -64,8 +65,9 @@ class ImageCodecService {
       image.dispose();
       if (byteData == null) return null;
 
-      // 3. Convert to grayscale in-place (luminance, keep alpha = 255).
+      // 3. Optionally convert to grayscale in-place (luminance).
       final rgba = byteData.buffer.asUint8List();
+      if (grayscale) {
         for (var i = 0; i < rgba.length; i += 4) {
           final lum =
               (0.299 * rgba[i] + 0.587 * rgba[i + 1] + 0.114 * rgba[i + 2])
@@ -74,7 +76,8 @@ class ImageCodecService {
           rgba[i] = lum;
           rgba[i + 1] = lum;
           rgba[i + 2] = lum;
-        rgba[i + 3] = 255; // fully opaque
+          rgba[i + 3] = 255;
+        }
       }
 
       // 4. Re-encode grayscale RGBA → PNG so encodeAvif can decode it.

lib/services/image_preferences.dart

@@ -5,9 +5,11 @@ class ImagePreferences {
   static const String _maxSizeKey = 'image_max_size';
   // Keep the legacy key name so existing users retain their saved value.
   static const String _qualityKey = 'image_quality';
+  static const String _grayscaleKey = 'image_grayscale';
 
   static const int defaultMaxSize = 256;
   static const int defaultQuality = 90;
+  static const bool defaultGrayscale = true;
 
   static const List<int> supportedSizes = [64, 128, 256];
 
@@ -32,4 +34,14 @@ class ImagePreferences {
     final prefs = await SharedPreferences.getInstance();
     await prefs.setInt(_qualityKey, compression.clamp(10, 90));
   }
+
+  static Future<bool> getGrayscale() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getBool(_grayscaleKey) ?? defaultGrayscale;
+  }
+
+  static Future<void> setGrayscale(bool value) async {
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(_grayscaleKey, value);
+  }
 }

lib/utils/image_message_parser.dart

@@ -1,5 +1,9 @@
 import 'dart:typed_data';
 
+const int _maxCompanionFrameBytes = 172; // MeshCore MAX_FRAME_SIZE
+const int _cmdSendRawDataOverheadBytes = 2; // cmd + pathLen
+const int _maxMeshPacketPayloadBytes = 184; // MeshCore MAX_PACKET_PAYLOAD
+
 /// Compressed image format used in the image packet protocol.
 enum ImageFormat {
   avif(0, 'AVIF'),
@@ -20,7 +24,7 @@ enum ImageFormat {
 /// Binary format (direct contacts, via pushRawData / cmdSendRawData):
 ///   [0x49 'I'][sessionId:4B][fmt:1B][idx:1B][total:1B][imageData...]
 ///
-/// Max total packet size is 160 bytes → 152 bytes of image data per fragment.
+/// Legacy default is 152 data bytes per fragment.
 class ImagePacket {
   final String sessionId; // 8 hex chars (4 bytes)
   final ImageFormat format;
@@ -38,7 +42,8 @@ class ImagePacket {
 
   static const int _magic = 0x49; // 'I'
   static const int _headerLen = 8; // magic(1)+session(4)+fmt(1)+idx(1)+total(1)
-  static const int maxDataBytes = 152; // 160 - 8 header bytes
+  static const int maxDataBytes =
+      152; // Conservative default for compatibility.
 
   static bool isImageBinary(Uint8List payload) =>
       payload.isNotEmpty && payload[0] == _magic;
@@ -90,6 +95,30 @@ class ImagePacket {
       'ImagePacket($sessionId ${format.label} [$index/${total - 1}] ${data.length}B)';
 }
 
+/// Compute the maximum safe image data bytes for a direct route path.
+///
+/// This accounts for:
+/// - companion command-frame limit (MAX_FRAME_SIZE=172),
+/// - cmdSendRawData overhead (`cmd` + `pathLen`),
+/// - image packet binary header (8 bytes),
+/// - mesh packet payload limit (MAX_PACKET_PAYLOAD=184).
+///
+/// Path length follows Contact.outPathLen semantics: 0 = direct, 1+ = hops.
+int safeImageDataBytesForPath(int pathLen) {
+  final normalizedPathLen = pathLen.clamp(0, 64).toInt();
+  final maxRawPayloadFromCommandFrame =
+      _maxCompanionFrameBytes -
+      _cmdSendRawDataOverheadBytes -
+      normalizedPathLen;
+  final maxRawPayloadFromMesh =
+      _maxMeshPacketPayloadBytes - ImagePacket._headerLen;
+  final maxRawPayload = maxRawPayloadFromCommandFrame < maxRawPayloadFromMesh
+      ? maxRawPayloadFromCommandFrame
+      : maxRawPayloadFromMesh;
+  final maxData = maxRawPayload - ImagePacket._headerLen;
+  return maxData.clamp(1, 255).toInt();
+}
+
 /// Envelope announcing image availability (control plane).
 ///
 /// Text format:
@@ -165,7 +194,7 @@ class ImageEnvelope {
   }
 
   String encode() =>
-      '${prefix}${sessionId.toLowerCase()}:${format.id}:$total:$width:$height:$sizeBytes:${senderKey6.toLowerCase()}:$timestampSec:$version';
+      '$prefix${sessionId.toLowerCase()}:${format.id}:$total:$width:$height:$sizeBytes:${senderKey6.toLowerCase()}:$timestampSec:$version';
 }
 
 /// Direct request to fetch image fragments (control plane).
@@ -178,7 +207,8 @@ class ImageFetchRequest {
   static const String prefix = 'IR1:';
 
   final String sessionId;
-  final String want; // always 'all'
+  final String want; // 'all' or 'missing'
+  final List<int> missingIndices;
   final String requesterKey6; // 12 hex chars
   final int timestampSec;
   final int version;
@@ -186,6 +216,7 @@ class ImageFetchRequest {
   const ImageFetchRequest({
     required this.sessionId,
     this.want = 'all',
+    this.missingIndices = const [],
     required this.requesterKey6,
     required this.timestampSec,
     this.version = 1,
@@ -204,10 +235,24 @@ class ImageFetchRequest {
       final requesterKey6 = parts[2];
       final ts = int.tryParse(parts[3]);
       final ver = int.tryParse(parts[4]);
-      final normalizedWant = wantToken == 'a' ? 'all' : wantToken;
+      final normalizedWant = wantToken == 'a'
+          ? 'all'
+          : (wantToken.startsWith('m-') ? 'missing' : wantToken);
 
       if (!RegExp(r'^[0-9a-fA-F]{8}$').hasMatch(sid)) return null;
-      if (normalizedWant != 'all') return null;
+      final missingIndices = <int>[];
+      if (normalizedWant == 'missing') {
+        final encoded = wantToken.substring(2);
+        if (encoded.isEmpty) return null;
+        for (final raw in encoded.split(',')) {
+          final idx = int.tryParse(raw);
+          if (idx == null || idx < 0 || idx > 254) return null;
+          missingIndices.add(idx);
+        }
+        if (missingIndices.isEmpty) return null;
+      } else if (normalizedWant != 'all') {
+        return null;
+      }
       if (!RegExp(r'^[0-9a-fA-F]{12}$').hasMatch(requesterKey6)) return null;
       if (ts == null || ts <= 0) return null;
       if (ver == null || ver != 1) return null;
@@ -215,6 +260,7 @@ class ImageFetchRequest {
       return ImageFetchRequest(
         sessionId: sid.toLowerCase(),
         want: normalizedWant,
+        missingIndices: missingIndices,
         requesterKey6: requesterKey6.toLowerCase(),
         timestampSec: ts,
         version: ver,
@@ -225,8 +271,10 @@ class ImageFetchRequest {
   }
 
   String encode() {
-    final wantToken = want == 'all' ? 'a' : want;
+    final wantToken = want == 'missing' && missingIndices.isNotEmpty
-    return '${prefix}${sessionId.toLowerCase()}:$wantToken:${requesterKey6.toLowerCase()}:$timestampSec:$version';
+        ? 'm-${missingIndices.join(',')}'
+        : (want == 'all' ? 'a' : want);
+    return '$prefix${sessionId.toLowerCase()}:$wantToken:${requesterKey6.toLowerCase()}:$timestampSec:$version';
   }
 }
 
@@ -239,8 +287,9 @@ List<ImagePacket> fragmentImage({
   required String sessionId,
   required ImageFormat format,
   required Uint8List bytes,
+  int maxDataBytes = ImagePacket.maxDataBytes,
 }) {
-  const chunkSize = ImagePacket.maxDataBytes;
+  final chunkSize = maxDataBytes.clamp(1, 255).toInt();
   final chunks = <Uint8List>[];
   for (var offset = 0; offset < bytes.length; offset += chunkSize) {
     final end = (offset + chunkSize).clamp(0, bytes.length);

lib/utils/voice_message_parser.dart

@@ -259,6 +259,7 @@ class VoiceFetchRequest {
 
   final String sessionId;
   final String want;
+  final List<int> missingIndices;
   final String requesterKey6;
   final int timestampSec;
   final int version;
@@ -266,6 +267,7 @@ class VoiceFetchRequest {
   const VoiceFetchRequest({
     required this.sessionId,
     this.want = 'all',
+    this.missingIndices = const [],
     required this.requesterKey6,
     required this.timestampSec,
     this.version = 1,
@@ -288,12 +290,26 @@ class VoiceFetchRequest {
       final requesterKey6 = parts[2];
       final ts = int.tryParse(parts[3]);
       final ver = int.tryParse(parts[4]);
-      final normalizedWant = wantToken == 'a' ? 'all' : wantToken;
+      final normalizedWant = wantToken == 'a'
+          ? 'all'
+          : (wantToken.startsWith('m-') ? 'missing' : wantToken);
 
       if (!RegExp(r'^[0-9a-fA-F]{8}$').hasMatch(sid)) {
         return null;
       }
-      if (normalizedWant != 'all') return null;
+      final missingIndices = <int>[];
+      if (normalizedWant == 'missing') {
+        final encoded = wantToken.substring(2);
+        if (encoded.isEmpty) return null;
+        for (final raw in encoded.split(',')) {
+          final idx = int.tryParse(raw);
+          if (idx == null || idx < 0 || idx > 254) return null;
+          missingIndices.add(idx);
+        }
+        if (missingIndices.isEmpty) return null;
+      } else if (normalizedWant != 'all') {
+        return null;
+      }
       if (!RegExp(r'^[0-9a-fA-F]{12}$').hasMatch(requesterKey6)) {
         return null;
       }
@@ -303,6 +319,7 @@ class VoiceFetchRequest {
       return VoiceFetchRequest(
         sessionId: sid.toLowerCase(),
         want: normalizedWant,
+        missingIndices: missingIndices,
         requesterKey6: requesterKey6.toLowerCase(),
         timestampSec: ts,
         version: ver,
@@ -313,7 +330,9 @@ class VoiceFetchRequest {
   }
 
   String encodeText() {
-    final wantToken = want == 'all' ? 'a' : want;
+    final wantToken = want == 'missing' && missingIndices.isNotEmpty
+        ? 'm-${missingIndices.join(',')}'
+        : (want == 'all' ? 'a' : want);
     return '$_prefix${sessionId.toLowerCase()}:$wantToken:${requesterKey6.toLowerCase()}:$timestampSec:$version';
   }
 }

test/utils/voice_message_parser_test.dart

@@ -59,6 +59,22 @@ void main() {
         isNull,
       );
     });
+
+    test('encodes and parses missing-packet request', () {
+      final req = VoiceFetchRequest(
+        sessionId: '00112233',
+        want: 'missing',
+        missingIndices: const [0, 3, 7],
+        requesterKey6: 'ffeeddccbbaa',
+        timestampSec: 1700000001,
+      );
+      final text = req.encodeText();
+
+      final parsed = VoiceFetchRequest.tryParseText(text);
+      expect(parsed, isNotNull);
+      expect(parsed!.want, equals('missing'));
+      expect(parsed.missingIndices, equals([0, 3, 7]));
+    });
   });
 
   group('VoicePacket backward compatibility', () {