fix: cancel persist timer on dispose to prevent post-dispose writes

- Clamp ML predictions between physics floor (raw airtime) and ceiling
  (worst-case formula) so model can never produce unsafe timeouts
- Replace hourOfDay feature with secondsSinceLastRx for network activity
- Remove unused _ContactStats.stdDev and dead model persistence code
- Debounce observation writes (2s) instead of writing on every delivery
- Skip recording observations when pathLength is null to avoid corrupting
  training data
- Add comment explaining global (not per-contact) RX time tracking
- Remove notifyListeners from retrain to avoid unnecessary widget rebuilds
- Run dart format

lib/connector/meshcore_connector.dart

@@ -19,6 +19,7 @@ import '../services/message_retry_service.dart';
 import '../services/path_history_service.dart';
 import '../services/app_settings_service.dart';
 import '../services/background_service.dart';
+import '../services/timeout_prediction_service.dart';
 import '../services/notification_service.dart';
 import 'meshcore_connector_usb.dart';
 import 'meshcore_connector_tcp.dart';
@@ -166,6 +167,10 @@ class MeshCoreConnector extends ChangeNotifier {
   bool _isLoadingContacts = false;
   bool _isLoadingChannels = false;
   bool _hasLoadedChannels = false;
+  TimeoutPredictionService? _timeoutPredictionService;
+  // Intentionally global (not per-contact): tracks overall network activity.
+  // Frequent RX from any source indicates a busy network with more collisions.
+  DateTime _lastRxTime = DateTime.now();
   bool _batteryRequested = false;
   bool _awaitingSelfInfo = false;
   bool _hasReceivedDeviceInfo = false;
@@ -668,6 +673,7 @@ class MeshCoreConnector extends ChangeNotifier {
     BleDebugLogService? bleDebugLogService,
     AppDebugLogService? appDebugLogService,
     BackgroundService? backgroundService,
+    TimeoutPredictionService? timeoutPredictionService,
   }) {
     _retryService = retryService;
     _pathHistoryService = pathHistoryService;
@@ -675,6 +681,7 @@ class MeshCoreConnector extends ChangeNotifier {
     _bleDebugLogService = bleDebugLogService;
     _appDebugLogService = appDebugLogService;
     _backgroundService = backgroundService;
+    _timeoutPredictionService = timeoutPredictionService;
     _usbManager.setDebugLogService(_appDebugLogService);
     _tcpConnector.setDebugLogService(_appDebugLogService);
 
@@ -689,13 +696,28 @@ class MeshCoreConnector extends ChangeNotifier {
       updateMessageCallback: _updateMessage,
       clearContactPathCallback: clearContactPath,
       setContactPathCallback: setContactPath,
-      calculateTimeoutCallback: (pathLength, messageBytes) =>
+      calculateTimeoutCallback:
-          calculateTimeout(pathLength: pathLength, messageBytes: messageBytes),
+          (pathLength, messageBytes, {String? contactKey}) => calculateTimeout(
+            pathLength: pathLength,
+            messageBytes: messageBytes,
+            contactKey: contactKey,
+          ),
       getSelfPublicKeyCallback: () => _selfPublicKey,
       prepareContactOutboundTextCallback: prepareContactOutboundText,
       appSettingsService: appSettingsService,
       debugLogService: _appDebugLogService,
       recordPathResultCallback: _recordPathResult,
+      onDeliveryObservedCallback:
+          (contactKey, pathLength, messageBytes, tripTimeMs) {
+            final secSinceRx = DateTime.now().difference(_lastRxTime).inSeconds;
+            _timeoutPredictionService?.recordObservation(
+              contactKey: contactKey,
+              pathLength: pathLength,
+              messageBytes: messageBytes,
+              tripTimeMs: tripTimeMs,
+              secondsSinceLastRx: secSinceRx,
+            );
+          },
     );
   }
 
@@ -2498,6 +2520,7 @@ class MeshCoreConnector extends ChangeNotifier {
 
   void _handleFrame(List<int> data) {
     if (data.isEmpty) return;
+    _lastRxTime = DateTime.now();
 
     final frame = Uint8List.fromList(data);
     _receivedFramesController.add(frame);
@@ -2874,38 +2897,68 @@ class MeshCoreConnector extends ChangeNotifier {
     }
   }
 
-  /// Calculate timeout for a message based on radio settings and path length
+  /// Estimate single-packet airtime in ms from radio settings, or a fallback.
-  /// Returns timeout in milliseconds, considering number of hops
+  int _estimateAirtimeMs(int messageBytes) {
-  int calculateTimeout({required int pathLength, int messageBytes = 100}) {
-    // If we have radio settings, use them for accurate calculation
     if (_currentFreqHz != null &&
         _currentBwHz != null &&
         _currentSf != null &&
         _currentCr != null) {
       final cr = _currentCr! <= 4 ? _currentCr! : _currentCr! - 4;
-      return calculateMessageTimeout(
+      return calculateLoRaAirtime(
-        freqHz: _currentFreqHz!,
+        payloadBytes: messageBytes,
-        bwHz: _currentBwHz!,
+        spreadingFactor: _currentSf!,
-        sf: _currentSf!,
+        bandwidthHz: _currentBwHz!,
-        cr: cr,
+        codingRate: cr,
-        pathLength: pathLength,
+        lowDataRateOptimize: _currentSf! >= 11,
-        messageBytes: messageBytes,
       );
     }
+    return 50; // fallback: ~SF7/BW125 for 100 bytes
+  }
 
-    // Fallback: Conservative estimates based on typical settings
+  /// Physics-based worst-case timeout (ceiling).
-    // Assume SF7, BW125, which gives ~50ms airtime for 100 bytes
+  int _physicsMaxTimeout(int pathLength, int airtime) {
-    const estimatedAirtime = 50;
-
     if (pathLength < 0) {
-      // Flood mode: Base delay + 16× airtime
+      return 500 + (16 * airtime);
-      return 500 + (16 * estimatedAirtime);
     } else {
-      // Direct path: Base delay + ((airtime×6 + 250ms)×(hops+1))
+      return 500 + ((airtime * 6 + 250) * (pathLength + 1));
-      return 500 + ((estimatedAirtime * 6 + 250) * (pathLength + 1));
     }
   }
 
+  /// Physics-based minimum timeout (floor): raw traversal time.
+  int _physicsMinTimeout(int pathLength, int airtime) {
+    if (pathLength < 0) {
+      return airtime;
+    } else {
+      return airtime * (pathLength + 1);
+    }
+  }
+
+  /// Calculate timeout for a message based on radio settings and path length.
+  /// Returns timeout in milliseconds, considering number of hops.
+  int calculateTimeout({
+    required int pathLength,
+    int messageBytes = 100,
+    String? contactKey,
+  }) {
+    final airtime = _estimateAirtimeMs(messageBytes);
+    final physicsMin = _physicsMinTimeout(pathLength, airtime);
+    final physicsMax = _physicsMaxTimeout(pathLength, airtime);
+
+    // Try ML-based prediction, clamped between physics bounds
+    final secSinceRx = DateTime.now().difference(_lastRxTime).inSeconds;
+    final mlTimeout = _timeoutPredictionService?.predictTimeout(
+      contactKey: contactKey,
+      pathLength: pathLength,
+      messageBytes: messageBytes,
+      secondsSinceLastRx: secSinceRx,
+    );
+    if (mlTimeout != null) {
+      return mlTimeout.clamp(physicsMin, physicsMax);
+    }
+
+    return physicsMax;
+  }
+
   void _handleContact(Uint8List frame, {bool isContact = true}) {
     final contact = Contact.fromFrame(frame);
     if (contact != null) {

lib/main.dart

@@ -19,6 +19,7 @@ import 'services/app_debug_log_service.dart';
 import 'services/background_service.dart';
 import 'services/map_tile_cache_service.dart';
 import 'services/chat_text_scale_service.dart';
+import 'services/timeout_prediction_service.dart';
 import 'storage/prefs_manager.dart';
 import 'utils/app_logger.dart';
 
@@ -39,6 +40,7 @@ void main() async {
   final backgroundService = BackgroundService();
   final mapTileCacheService = MapTileCacheService();
   final chatTextScaleService = ChatTextScaleService();
+  final timeoutPredictionService = TimeoutPredictionService(storage);
 
   // Load settings
   await appSettingsService.loadSettings();
@@ -56,6 +58,7 @@ void main() async {
   _registerThirdPartyLicenses();
 
   await chatTextScaleService.initialize();
+  await timeoutPredictionService.initialize();
 
   // Wire up connector with services
   connector.initialize(
@@ -65,6 +68,7 @@ void main() async {
     bleDebugLogService: bleDebugLogService,
     appDebugLogService: appDebugLogService,
     backgroundService: backgroundService,
+    timeoutPredictionService: timeoutPredictionService,
   );
 
   await connector.loadContactCache();
@@ -86,6 +90,7 @@ void main() async {
       appDebugLogService: appDebugLogService,
       mapTileCacheService: mapTileCacheService,
       chatTextScaleService: chatTextScaleService,
+      timeoutPredictionService: timeoutPredictionService,
     ),
   );
 }
@@ -121,6 +126,7 @@ class MeshCoreApp extends StatelessWidget {
   final AppDebugLogService appDebugLogService;
   final MapTileCacheService mapTileCacheService;
   final ChatTextScaleService chatTextScaleService;
+  final TimeoutPredictionService timeoutPredictionService;
 
   const MeshCoreApp({
     super.key,
@@ -133,6 +139,7 @@ class MeshCoreApp extends StatelessWidget {
     required this.appDebugLogService,
     required this.mapTileCacheService,
     required this.chatTextScaleService,
+    required this.timeoutPredictionService,
   });
 
   @override
@@ -148,6 +155,7 @@ class MeshCoreApp extends StatelessWidget {
         ChangeNotifierProvider.value(value: chatTextScaleService),
         Provider.value(value: storage),
         Provider.value(value: mapTileCacheService),
+        ChangeNotifierProvider.value(value: timeoutPredictionService),
       ],
       child: Consumer<AppSettingsService>(
         builder: (context, settingsService, child) {

lib/models/delivery_observation.dart

@@ -0,0 +1,43 @@
+class DeliveryObservation {
+  final String contactKey;
+  final int pathLength;
+  final int messageBytes;
+  final int secondsSinceLastRx;
+  final bool isFlood;
+  final int deliveryMs;
+  final DateTime timestamp;
+
+  DeliveryObservation({
+    required this.contactKey,
+    required this.pathLength,
+    required this.messageBytes,
+    required this.secondsSinceLastRx,
+    required this.isFlood,
+    required this.deliveryMs,
+    required this.timestamp,
+  });
+
+  Map<String, dynamic> toJson() {
+    return {
+      'contact_key': contactKey,
+      'path_length': pathLength,
+      'message_bytes': messageBytes,
+      'seconds_since_last_rx': secondsSinceLastRx,
+      'is_flood': isFlood,
+      'delivery_ms': deliveryMs,
+      'timestamp': timestamp.toIso8601String(),
+    };
+  }
+
+  factory DeliveryObservation.fromJson(Map<String, dynamic> json) {
+    return DeliveryObservation(
+      contactKey: json['contact_key'] as String,
+      pathLength: json['path_length'] as int,
+      messageBytes: json['message_bytes'] as int,
+      secondsSinceLastRx: json['seconds_since_last_rx'] as int? ?? 0,
+      isFlood: json['is_flood'] as bool,
+      deliveryMs: json['delivery_ms'] as int,
+      timestamp: DateTime.parse(json['timestamp'] as String),
+    );
+  }
+}

lib/services/message_retry_service.dart

@@ -58,12 +58,13 @@ class MessageRetryService extends ChangeNotifier {
   Function(Message)? _updateMessageCallback;
   Function(Contact)? _clearContactPathCallback;
   Function(Contact, Uint8List, int)? _setContactPathCallback;
-  Function(int, int)? _calculateTimeoutCallback;
+  Function(int, int, {String? contactKey})? _calculateTimeoutCallback;
   Uint8List? Function()? _getSelfPublicKeyCallback;
   String Function(Contact, String)? _prepareContactOutboundTextCallback;
   AppSettingsService? _appSettingsService;
   AppDebugLogService? _debugLogService;
   Function(String, PathSelection, bool, int?)? _recordPathResultCallback;
+  Function(String, int, int, int)? _onDeliveryObservedCallback;
 
   MessageRetryService();
 
@@ -73,12 +74,20 @@ class MessageRetryService extends ChangeNotifier {
     required Function(Message) updateMessageCallback,
     Function(Contact)? clearContactPathCallback,
     Function(Contact, Uint8List, int)? setContactPathCallback,
-    Function(int pathLength, int messageBytes)? calculateTimeoutCallback,
+    Function(int pathLength, int messageBytes, {String? contactKey})?
+    calculateTimeoutCallback,
     Uint8List? Function()? getSelfPublicKeyCallback,
     String Function(Contact, String)? prepareContactOutboundTextCallback,
     AppSettingsService? appSettingsService,
     AppDebugLogService? debugLogService,
     Function(String, PathSelection, bool, int?)? recordPathResultCallback,
+    Function(
+      String contactKey,
+      int pathLength,
+      int messageBytes,
+      int tripTimeMs,
+    )?
+    onDeliveryObservedCallback,
   }) {
     _sendMessageCallback = sendMessageCallback;
     _addMessageCallback = addMessageCallback;
@@ -91,6 +100,7 @@ class MessageRetryService extends ChangeNotifier {
     _appSettingsService = appSettingsService;
     _debugLogService = debugLogService;
     _recordPathResultCallback = recordPathResultCallback;
+    _onDeliveryObservedCallback = onDeliveryObservedCallback;
   }
 
   /// Compute expected ACK hash using same algorithm as firmware:
@@ -423,25 +433,33 @@ class MessageRetryService extends ChangeNotifier {
       );
     }
 
-    // Use device-provided timeout, or calculate from radio settings if timeout is 0 or invalid
+    // Calculate timeout: prefer ML prediction, then device-provided, then physics fallback
+    int pathLengthValue;
+    if (selection != null) {
+      pathLengthValue = selection.useFlood ? -1 : selection.hopCount;
+      if (pathLengthValue < 0) pathLengthValue = contact.pathLength;
+    } else if (message.pathLength != null) {
+      pathLengthValue = message.pathLength!;
+    } else {
+      pathLengthValue = contact.pathLength;
+    }
+
     int actualTimeout = timeoutMs;
-    if (timeoutMs <= 0 && _calculateTimeoutCallback != null) {
+    if (_calculateTimeoutCallback != null) {
-      int pathLengthValue;
+      final calculated = _calculateTimeoutCallback!(
-      if (selection != null) {
-        pathLengthValue = selection.useFlood ? -1 : selection.hopCount;
-        if (pathLengthValue < 0) pathLengthValue = contact.pathLength;
-      } else if (message.pathLength != null) {
-        pathLengthValue = message.pathLength!;
-      } else {
-        pathLengthValue = contact.pathLength;
-      }
-      actualTimeout = _calculateTimeoutCallback!(
         pathLengthValue,
         message.text.length,
+        contactKey: contact.publicKeyHex,
       );
-      debugPrint(
+      // calculateTimeout tries ML first, falls back to physics.
-        'Using calculated timeout: ${actualTimeout}ms for path length $pathLengthValue',
+      // Use calculated value if device didn't provide one, or if ML
-      );
+      // produced a tighter prediction than the device's estimate.
+      if (timeoutMs <= 0 || calculated < timeoutMs) {
+        actualTimeout = calculated;
+        debugPrint(
+          'Using calculated timeout: ${actualTimeout}ms for path length $pathLengthValue',
+        );
+      }
     }
 
     final updatedMessage = message.copyWith(
@@ -738,6 +756,16 @@ class MessageRetryService extends ChangeNotifier {
           true,
           tripTimeMs,
         );
+        if (_onDeliveryObservedCallback != null &&
+            tripTimeMs > 0 &&
+            message.pathLength != null) {
+          _onDeliveryObservedCallback!(
+            contact.publicKeyHex,
+            message.pathLength!,
+            message.text.length,
+            tripTimeMs,
+          );
+        }
         _onMessageResolved(matchedMessageId, contact.publicKeyHex);
       }
 

lib/services/storage_service.dart

@@ -1,4 +1,5 @@
 import 'dart:convert';
+import '../models/delivery_observation.dart';
 import '../models/path_history.dart';
 import '../storage/prefs_manager.dart';
 
@@ -6,6 +7,7 @@ class StorageService {
   static const String _pathHistoryPrefix = 'path_history_';
   static const String _pendingMessagesKey = 'pending_messages';
   static const String _repeaterPasswordsKey = 'repeater_passwords';
+  static const String _deliveryObservationsKey = 'delivery_observations';
 
   Future<void> savePathHistory(
     String contactPubKeyHex,
@@ -122,4 +124,33 @@ class StorageService {
     final prefs = PrefsManager.instance;
     await prefs.remove(_repeaterPasswordsKey);
   }
+
+  Future<void> saveDeliveryObservations(
+    List<DeliveryObservation> observations,
+  ) async {
+    final prefs = PrefsManager.instance;
+    final jsonStr = jsonEncode(observations.map((o) => o.toJson()).toList());
+    await prefs.setString(_deliveryObservationsKey, jsonStr);
+  }
+
+  Future<List<DeliveryObservation>> loadDeliveryObservations() async {
+    final prefs = PrefsManager.instance;
+    final jsonStr = prefs.getString(_deliveryObservationsKey);
+
+    if (jsonStr == null) return [];
+
+    try {
+      final list = jsonDecode(jsonStr) as List;
+      return list
+          .map((e) => DeliveryObservation.fromJson(e as Map<String, dynamic>))
+          .toList();
+    } catch (e) {
+      return [];
+    }
+  }
+
+  Future<void> clearDeliveryObservations() async {
+    final prefs = PrefsManager.instance;
+    await prefs.remove(_deliveryObservationsKey);
+  }
 }

lib/services/timeout_prediction_service.dart

@@ -0,0 +1,229 @@
+import 'dart:async';
+import 'package:flutter/foundation.dart';
+import 'package:ml_algo/ml_algo.dart';
+import 'package:ml_dataframe/ml_dataframe.dart';
+import '../models/delivery_observation.dart';
+import 'storage_service.dart';
+
+class _ContactStats {
+  int count = 0;
+  double _sum = 0;
+
+  void add(double ms) {
+    count++;
+    _sum += ms;
+  }
+
+  double get mean => _sum / count;
+}
+
+class TimeoutPredictionService extends ChangeNotifier {
+  final StorageService? _storage;
+
+  static const int minObservations = 10;
+  static const int maxObservations = 100;
+  static const int _retrainInterval = 5;
+  // 1.5x multiplier on raw prediction to account for variance in delivery
+  // times — tight enough to improve on worst-case physics, loose enough
+  // to avoid premature timeouts from model noise.
+  static const double _safetyMargin = 1.5;
+  static const int _minContactObservations = 10;
+
+  List<DeliveryObservation> _observations = [];
+  LinearRegressor? _model;
+  List<String> _activeFeatures = [];
+  int _observationsSinceLastTrain = 0;
+  final Map<String, _ContactStats> _contactStats = {};
+  Timer? _persistTimer;
+
+  TimeoutPredictionService(StorageService storage) : _storage = storage;
+  TimeoutPredictionService.noStorage() : _storage = null;
+
+  int get observationCount => _observations.length;
+  bool get hasModel => _model != null;
+
+  Future<void> initialize() async {
+    _observations = await _storage?.loadDeliveryObservations() ?? [];
+    _rebuildContactStats();
+
+    if (_observations.length >= minObservations) {
+      _trainModel();
+    }
+
+    debugPrint(
+      'TimeoutPrediction: initialized with ${_observations.length} observations, '
+      'model=${_model != null ? "ready" : "waiting for data"}',
+    );
+  }
+
+  void recordObservation({
+    required String contactKey,
+    required int pathLength,
+    required int messageBytes,
+    required int tripTimeMs,
+    int secondsSinceLastRx = 0,
+  }) {
+    final observation = DeliveryObservation(
+      contactKey: contactKey,
+      pathLength: pathLength,
+      messageBytes: messageBytes,
+      secondsSinceLastRx: secondsSinceLastRx,
+      isFlood: pathLength < 0,
+      deliveryMs: tripTimeMs,
+      timestamp: DateTime.now(),
+    );
+
+    _observations.add(observation);
+    if (_observations.length > maxObservations) {
+      _observations.removeAt(0);
+    }
+
+    _contactStats.putIfAbsent(contactKey, () => _ContactStats());
+    _contactStats[contactKey]!.add(tripTimeMs.toDouble());
+
+    _observationsSinceLastTrain++;
+    if (_observationsSinceLastTrain >= _retrainInterval &&
+        _observations.length >= minObservations) {
+      _trainModel();
+    }
+
+    _persistTimer?.cancel();
+    _persistTimer = Timer(const Duration(seconds: 2), () {
+      _storage?.saveDeliveryObservations(_observations);
+    });
+    debugPrint(
+      'TimeoutPrediction: recorded ${tripTimeMs}ms for $pathLength hops '
+      '(${_observations.length} total)',
+    );
+  }
+
+  int? predictTimeout({
+    String? contactKey,
+    required int pathLength,
+    required int messageBytes,
+    int secondsSinceLastRx = 0,
+  }) {
+    if (_model == null) return null;
+
+    try {
+      if (_activeFeatures.isEmpty) return null;
+
+      final allFeatures = {
+        'pathLength': pathLength.toDouble(),
+        'messageBytes': messageBytes.toDouble(),
+        'secSinceRx': secondsSinceLastRx.toDouble(),
+        'isFlood': pathLength < 0 ? 1.0 : 0.0,
+      };
+      final row = _activeFeatures.map((f) => allFeatures[f]!).toList();
+
+      final features = DataFrame(
+        [row],
+        headerExists: false,
+        header: _activeFeatures,
+      );
+
+      final prediction = _model!.predict(features);
+      final rawValue = prediction.rows.first.first;
+      var predictedMs = (rawValue is double)
+          ? rawValue
+          : (rawValue as num).toDouble();
+
+      debugPrint(
+        'TimeoutPrediction: raw prediction=$predictedMs for '
+        'pathLength=$pathLength, messageBytes=$messageBytes, '
+        'features=$_activeFeatures',
+      );
+
+      // Sanity check: if prediction is negative or zero, fall back
+      if (predictedMs <= 0) return null;
+
+      // Blend with per-contact mean if enough data
+      if (contactKey != null) {
+        final stats = _contactStats[contactKey];
+        if (stats != null && stats.count >= _minContactObservations) {
+          predictedMs = 0.5 * predictedMs + 0.5 * stats.mean;
+        }
+      }
+
+      // Connector clamps this between physics min/max bounds
+      final timeout = (predictedMs * _safetyMargin).ceil();
+      debugPrint(
+        'TimeoutPrediction: ML timeout ${timeout}ms '
+        '(raw: ${predictedMs.round()}ms, contact: $contactKey)',
+      );
+      return timeout;
+    } catch (e) {
+      debugPrint('TimeoutPrediction: prediction failed: $e');
+      return null;
+    }
+  }
+
+  void _trainModel() {
+    try {
+      // Build feature columns, then exclude any with zero variance
+      // (ml_algo's OLS produces all-zero coefficients for singular matrices)
+      final allNames = ['pathLength', 'messageBytes', 'secSinceRx', 'isFlood'];
+      final allExtractors = <double Function(DeliveryObservation)>[
+        (o) => o.pathLength.toDouble(),
+        (o) => o.messageBytes.toDouble(),
+        (o) => o.secondsSinceLastRx.toDouble(),
+        (o) => o.isFlood ? 1.0 : 0.0,
+      ];
+
+      _activeFeatures = [];
+      for (var i = 0; i < allNames.length; i++) {
+        final values = _observations.map(allExtractors[i]).toSet();
+        if (values.length > 1) _activeFeatures.add(allNames[i]);
+      }
+
+      if (_activeFeatures.isEmpty) {
+        debugPrint(
+          'TimeoutPrediction: no features with variance, skipping training',
+        );
+        return;
+      }
+
+      final header = [..._activeFeatures, 'deliveryMs'];
+      final rows = _observations.map((o) {
+        final row = <double>[];
+        for (var i = 0; i < allNames.length; i++) {
+          if (_activeFeatures.contains(allNames[i])) {
+            row.add(allExtractors[i](o));
+          }
+        }
+        row.add(o.deliveryMs.toDouble());
+        return row;
+      });
+
+      final data = DataFrame([header, ...rows], headerExists: true);
+
+      _model = LinearRegressor(data, 'deliveryMs');
+      _observationsSinceLastTrain = 0;
+
+      // Log training summary with sample predictions
+      final avgMs =
+          _observations.map((o) => o.deliveryMs).reduce((a, b) => a + b) /
+          _observations.length;
+      debugPrint(
+        'TimeoutPrediction: trained on ${_observations.length} observations '
+        '(avg: ${avgMs.round()}ms, features: $_activeFeatures)',
+      );
+    } catch (e) {
+      debugPrint('TimeoutPrediction: training failed: $e');
+    }
+  }
+
+  @override
+  void dispose() {
+    _persistTimer?.cancel();
+    super.dispose();
+  }
+
+  void _rebuildContactStats() {
+    _contactStats.clear();
+    for (final obs in _observations) {
+      _contactStats.putIfAbsent(obs.contactKey, () => _ContactStats());
+      _contactStats[obs.contactKey]!.add(obs.deliveryMs.toDouble());
+    }
+  }
+}

pubspec.yaml

@@ -69,6 +69,8 @@ dependencies:
   material_symbols_icons: ^4.2906.0
   web: ^1.1.1
   flutter_svg: ^2.0.10+1
+  ml_algo: ^16.0.0
+  ml_dataframe: ^1.0.0
 
 dev_dependencies:
   flutter_test:

test/services/ml_algo_sanity_test.dart

@@ -0,0 +1,156 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:ml_algo/ml_algo.dart';
+import 'package:ml_dataframe/ml_dataframe.dart';
+
+void main() {
+  test('LinearRegressor basic sanity check', () {
+    // Simple: y = 2x + 100
+    final data = DataFrame(
+      [
+        [1.0, 102.0],
+        [2.0, 104.0],
+        [3.0, 106.0],
+        [4.0, 108.0],
+        [5.0, 110.0],
+        [10.0, 120.0],
+        [20.0, 140.0],
+        [50.0, 200.0],
+        [0.0, 100.0],
+        [100.0, 300.0],
+      ],
+      headerExists: false,
+      header: ['x', 'y'],
+    );
+
+    debugPrint('Training data columns: ${data.header}');
+    debugPrint('Training data rows: ${data.rows.length}');
+
+    final model = LinearRegressor(data, 'y');
+
+    final testDf = DataFrame(
+      [
+        [25.0],
+      ],
+      headerExists: false,
+      header: ['x'],
+    );
+
+    final prediction = model.predict(testDf);
+    final value = prediction.rows.first.first;
+    debugPrint('Predict x=25 → y=$value (expected ~150)');
+    expect((value as num).toDouble(), closeTo(150, 5));
+  });
+
+  test('LinearRegressor multi-feature with constant column produces zeros', () {
+    // isFlood=0 for all rows → zero-variance column → singular matrix
+    final data = DataFrame(
+      [
+        [0.0, 50.0, 14.0, 0.0, 1900.0],
+        [0.0, 80.0, 14.0, 0.0, 2200.0],
+        [2.0, 50.0, 14.0, 0.0, 5000.0],
+        [4.0, 50.0, 14.0, 0.0, 9500.0],
+      ],
+      headerExists: false,
+      header: [
+        'pathLength',
+        'messageBytes',
+        'hourOfDay',
+        'isFlood',
+        'deliveryMs',
+      ],
+    );
+
+    final model = LinearRegressor(data, 'deliveryMs');
+    final testDf = DataFrame(
+      [
+        [2.0, 50.0, 14.0, 0.0],
+      ],
+      headerExists: false,
+      header: ['pathLength', 'messageBytes', 'hourOfDay', 'isFlood'],
+    );
+    final pred = model.predict(testDf).rows.first.first;
+    debugPrint(
+      'With constant isFlood column: hops=2 → ${(pred as num).round()}ms (likely 0)',
+    );
+  });
+
+  test('LinearRegressor 2-feature works correctly', () {
+    // Just pathLength + messageBytes → deliveryMs
+    final data = DataFrame(
+      [
+        [0.0, 50.0, 1900.0],
+        [0.0, 80.0, 2200.0],
+        [2.0, 50.0, 5000.0],
+        [2.0, 80.0, 5500.0],
+        [4.0, 50.0, 9500.0],
+        [4.0, 80.0, 10000.0],
+        [0.0, 30.0, 1800.0],
+        [2.0, 30.0, 4800.0],
+        [4.0, 30.0, 9000.0],
+        [0.0, 60.0, 2000.0],
+      ],
+      headerExists: false,
+      header: ['pathLength', 'messageBytes', 'deliveryMs'],
+    );
+
+    final model = LinearRegressor(data, 'deliveryMs');
+
+    for (final hops in [0.0, 2.0, 4.0]) {
+      final testDf = DataFrame(
+        [
+          [hops, 50.0],
+        ],
+        headerExists: false,
+        header: ['pathLength', 'messageBytes'],
+      );
+      final pred = model.predict(testDf).rows.first.first;
+      debugPrint('2-feature: hops=$hops → ${(pred as num).round()}ms');
+    }
+  });
+
+  test('LinearRegressor multi-feature with variance in all columns', () {
+    // Mix flood and direct so isFlood has variance
+    final data = DataFrame(
+      [
+        [0.0, 50.0, 14.0, 0.0, 1900.0],
+        [0.0, 80.0, 10.0, 0.0, 2200.0],
+        [2.0, 50.0, 16.0, 0.0, 5000.0],
+        [2.0, 80.0, 20.0, 0.0, 5500.0],
+        [4.0, 50.0, 8.0, 0.0, 9500.0],
+        [4.0, 80.0, 12.0, 0.0, 10000.0],
+        [-1.0, 40.0, 14.0, 1.0, 5000.0],
+        [-1.0, 60.0, 18.0, 1.0, 6500.0],
+        [-1.0, 30.0, 10.0, 1.0, 4000.0],
+        [-1.0, 80.0, 22.0, 1.0, 7000.0],
+      ],
+      headerExists: false,
+      header: [
+        'pathLength',
+        'messageBytes',
+        'hourOfDay',
+        'isFlood',
+        'deliveryMs',
+      ],
+    );
+
+    final model = LinearRegressor(data, 'deliveryMs');
+
+    for (final tc in [
+      [0.0, 50.0, 14.0, 0.0],
+      [2.0, 50.0, 14.0, 0.0],
+      [4.0, 50.0, 14.0, 0.0],
+      [-1.0, 50.0, 14.0, 1.0],
+    ]) {
+      final testDf = DataFrame(
+        [tc],
+        headerExists: false,
+        header: ['pathLength', 'messageBytes', 'hourOfDay', 'isFlood'],
+      );
+      final pred = model.predict(testDf).rows.first.first;
+      debugPrint(
+        '4-feature: hops=${tc[0]} flood=${tc[3]} → ${(pred as num).round()}ms',
+      );
+    }
+  });
+}

test/services/timeout_prediction_service_test.dart

@@ -0,0 +1,164 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_open/models/delivery_observation.dart';
+import 'package:meshcore_open/services/timeout_prediction_service.dart';
+
+void main() {
+  late TimeoutPredictionService service;
+
+  setUp(() {
+    service = TimeoutPredictionService.noStorage();
+  });
+
+  test('trains on sample data and predicts sensible timeouts', () {
+    // Simulate realistic delivery data:
+    // Direct 0-hop messages: ~1500-2500ms
+    // 2-hop messages: ~4000-6000ms
+    // 4-hop messages: ~8000-12000ms
+    // Flood messages: ~3000-8000ms
+    final sampleData = [
+      // 0-hop direct
+      _obs(pathLength: 0, messageBytes: 20, deliveryMs: 1800),
+      _obs(pathLength: 0, messageBytes: 50, deliveryMs: 2100),
+      _obs(pathLength: 0, messageBytes: 80, deliveryMs: 2400),
+      _obs(pathLength: 0, messageBytes: 30, deliveryMs: 1925),
+      // 2-hop direct
+      _obs(pathLength: 2, messageBytes: 40, deliveryMs: 4500),
+      _obs(pathLength: 2, messageBytes: 60, deliveryMs: 5200),
+      _obs(pathLength: 2, messageBytes: 25, deliveryMs: 4100),
+      // 4-hop direct
+      _obs(pathLength: 4, messageBytes: 50, deliveryMs: 9800),
+      _obs(pathLength: 4, messageBytes: 30, deliveryMs: 8500),
+      _obs(pathLength: 4, messageBytes: 70, deliveryMs: 10570),
+      // Flood
+      _obs(pathLength: -1, messageBytes: 40, deliveryMs: 5000),
+      _obs(pathLength: -1, messageBytes: 60, deliveryMs: 6500),
+    ];
+
+    // Feed all observations
+    for (final obs in sampleData) {
+      service.recordObservation(
+        contactKey: obs.contactKey,
+        pathLength: obs.pathLength,
+        messageBytes: obs.messageBytes,
+        tripTimeMs: obs.deliveryMs,
+      );
+    }
+
+    expect(service.hasModel, isTrue);
+    expect(service.observationCount, equals(12));
+
+    // Predict for different scenarios
+    final direct0 = service.predictTimeout(pathLength: 0, messageBytes: 50);
+    final direct2 = service.predictTimeout(pathLength: 2, messageBytes: 50);
+    final direct4 = service.predictTimeout(pathLength: 4, messageBytes: 50);
+    final flood = service.predictTimeout(pathLength: -1, messageBytes: 50);
+
+    // All should return non-null (model is trained)
+    expect(direct0, isNotNull);
+    expect(direct2, isNotNull);
+    expect(direct4, isNotNull);
+    expect(flood, isNotNull);
+
+    // More hops should predict longer timeouts
+    expect(direct4!, greaterThan(direct2!));
+    expect(direct2, greaterThan(direct0!));
+
+    // All should be positive
+    expect(direct0, greaterThan(0));
+    expect(direct4, greaterThan(0));
+
+    // Print predictions for visibility
+    debugPrint('Predictions (with 1.5x safety margin):');
+    debugPrint('  0-hop direct: ${direct0}ms');
+    debugPrint('  2-hop direct: ${direct2}ms');
+    debugPrint('  4-hop direct: ${direct4}ms');
+    debugPrint('  flood:        ${flood}ms');
+  });
+
+  test('returns null before minimum observations', () {
+    for (var i = 0; i < TimeoutPredictionService.minObservations - 1; i++) {
+      service.recordObservation(
+        contactKey: 'abc',
+        pathLength: 0,
+        messageBytes: 50,
+        tripTimeMs: 2000,
+      );
+    }
+
+    expect(service.hasModel, isFalse);
+    expect(service.predictTimeout(pathLength: 0, messageBytes: 50), isNull);
+  });
+
+  test('caps observations at maxObservations', () {
+    for (var i = 0; i < TimeoutPredictionService.maxObservations + 20; i++) {
+      service.recordObservation(
+        contactKey: 'abc',
+        pathLength: 0,
+        messageBytes: 50,
+        tripTimeMs: 2000 + i,
+      );
+    }
+
+    expect(
+      service.observationCount,
+      equals(TimeoutPredictionService.maxObservations),
+    );
+  });
+
+  test('blends per-contact stats after enough observations', () {
+    // Train with mixed contacts and varied features:
+    // contactA is fast (0-hop), contactB is slow (2-hop)
+    for (var i = 0; i < 12; i++) {
+      service.recordObservation(
+        contactKey: 'contactA',
+        pathLength: 0,
+        messageBytes: 30 + i,
+        tripTimeMs: 1500,
+      );
+      service.recordObservation(
+        contactKey: 'contactB',
+        pathLength: 2,
+        messageBytes: 30 + i,
+        tripTimeMs: 8000,
+      );
+    }
+
+    final predA = service.predictTimeout(
+      contactKey: 'contactA',
+      pathLength: 0,
+      messageBytes: 50,
+    );
+    final predB = service.predictTimeout(
+      contactKey: 'contactB',
+      pathLength: 0,
+      messageBytes: 50,
+    );
+
+    expect(predA, isNotNull);
+    expect(predB, isNotNull);
+    // Contact B (slow) should have a higher predicted timeout than A (fast)
+    expect(predB!, greaterThan(predA!));
+
+    debugPrint('Per-contact blending:');
+    debugPrint('  contactA (fast): ${predA}ms');
+    debugPrint('  contactB (slow): ${predB}ms');
+  });
+}
+
+DeliveryObservation _obs({
+  required int pathLength,
+  required int messageBytes,
+  required int deliveryMs,
+  String contactKey = 'test_contact',
+}) {
+  return DeliveryObservation(
+    contactKey: contactKey,
+    pathLength: pathLength,
+    messageBytes: messageBytes,
+    secondsSinceLastRx: 5,
+    isFlood: pathLength < 0,
+    deliveryMs: deliveryMs,
+    timestamp: DateTime.now(),
+  );
+}