fix(#115): decode multi-byte path hashes at the device width

Packet Path mis-identified repeaters: a 2-byte path hash like 6A3D was
sliced into two 1-byte hops (6A + 3D), so the first byte collided with an
unrelated repeater (Freemasons 6A..) and the second matched nothing
("Unknown Repeater").

- meshcore_protocol: realHopCount() converts the firmware path BYTE length
  to true hops via the device hash width.
- channel_message_path_screen: slice/count/match at the device
  pathHashByteWidth (not the unreliable per-message high-bits); bucket and
  match on the full w-byte hash (mirrors _pathMatchesContact), not hash[0].
- channel_chat_screen: same width fix on the per-message via-line + hop badge.
- settings: show the build number alongside the version name.
- bump 1.1.2-beta.4+36.
- test: realHopCount regression coverage.

Gemini review (llm-consult): fix-then-ship; 2 findings clarification-only
(_formatHash is canonical hex used identically both sides; pathHashByteWidth
is static per-connection).

Part of epic #112.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/connector/meshcore_protocol.dart

@@ -445,12 +445,26 @@ int readInt32LE(Uint8List data, int offset) {
   return val;
 }
 
-// Path-length byte: firmware packs hop count + hash width into one byte.
-// Low 6 bits = hop count (0-63); high 2 bits = hash-size mode 0..2 -> 1..3 bytes/hop.
+// Path-length byte from the firmware. Low 6 bits = the path length field
+// (a BYTE count of the hop-hash array, 0-63); high 2 bits carry an optional
+// hash-size mode hint (0..2 -> 1..3 bytes/hop) that is not reliably populated,
+// so the device's configured hash width (MeshCoreConnector.pathHashByteWidth)
+// is authoritative for slicing the path. realHopCount() converts the byte
+// length to a true hop count at that width. (#112)
 // TX counterpart: buildSetPathHashModeFrame (CMD_SET_PATH_HASH_MODE).
 int pathHopCount(int pathLenRaw) => pathLenRaw & 0x3F;
 int pathHashSizeBytes(int pathLenRaw) => ((pathLenRaw >> 6) & 0x03) + 1;
 
+/// Real hop count from the firmware path byte-length and the device hash width.
+/// `pathHopCount` returns the path BYTE length, so at a 2-byte hash width a
+/// single 2-byte hop reports 2 — divide by the width to get the true hop count.
+/// Null (unknown) and negative (flood) sentinels pass through unchanged. (#112)
+int? realHopCount(int? rawByteLen, int hashWidth) {
+  if (rawByteLen == null || rawByteLen < 0) return rawByteLen;
+  final w = hashWidth < 1 ? 1 : hashWidth;
+  return rawByteLen ~/ w;
+}
+
 // Helper to convert uint32 to hex string
 String ackHashToHex(int ackHash) {
   return ackHash.toRadixString(16).padLeft(8, '0');

lib/screens/channel_chat_screen.dart

@@ -494,6 +494,7 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
   Widget _buildMessageBubble(ChannelMessage message, double textScale) {
     final settingsService = context.watch<AppSettingsService>();
     final enableTracing = settingsService.settings.enableMessageTracing;
+    final hashWidth = context.read<MeshCoreConnector>().pathHashByteWidth;
     final isOutgoing = message.isOutgoing;
     final gifId = GifHelper.parseGif(message.text);
     final poi = parseMarkerText(message.text);
@@ -634,10 +635,7 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
                               : EdgeInsets.zero,
                           child: Text(
                             context.l10n.channels_via(
-                              _formatPathPrefixes(
-                                displayPath,
-                                message.pathHashSize,
-                              ),
+                              _formatPathPrefixes(displayPath, hashWidth),
                             ),
                             style: TextStyle(
                               fontSize: 11,
@@ -1337,7 +1335,8 @@ class _ChannelChatScreenState extends State<ChannelChatScreen> {
   }
 
   Widget _buildHopBadge(BuildContext context, ChannelMessage message) {
-    final hops = message.hopCount ?? 0;
+    final hashWidth = context.read<MeshCoreConnector>().pathHashByteWidth;
+    final hops = realHopCount(message.hopCount, hashWidth) ?? 0;
     final color = Theme.of(context).brightness == Brightness.dark
         ? Colors.grey[400]
         : Colors.grey[600];

lib/screens/channel_message_path_screen.dart

@@ -40,16 +40,12 @@ class ChannelMessagePathScreen extends StatelessWidget {
         final primaryPath = !channelMessage && !message.isOutgoing
             ? Uint8List.fromList(primaryPathTmp.reversed.toList())
             : primaryPathTmp;
-        final hops = _buildPathHops(
-          primaryPath,
-          connector,
-          l10n,
-          message.pathHashSize,
-        );
+        final hashWidth = connector.pathHashByteWidth;
+        final hops = _buildPathHops(primaryPath, connector, l10n, hashWidth);
         final hasHopDetails = primaryPath.isNotEmpty;
         final observedLabel = _formatObservedHops(
-          primaryPath.length ~/ message.pathHashSize,
-          message.hopCount,
+          primaryPath.length ~/ hashWidth,
+          realHopCount(message.hopCount, hashWidth),
           l10n,
         );
         final extraPaths = _otherPaths(primaryPath, message.pathVariants);
@@ -125,6 +121,7 @@ class ChannelMessagePathScreen extends StatelessWidget {
 
   Widget _buildSummaryCard(BuildContext context, {String? observedLabel}) {
     final l10n = context.l10n;
+    final hashWidth = context.read<MeshCoreConnector>().pathHashByteWidth;
     return Card(
       child: Padding(
         padding: const EdgeInsets.all(12),
@@ -148,7 +145,7 @@ class ChannelMessagePathScreen extends StatelessWidget {
               ),
             _buildDetailRow(
               l10n.channelPath_pathLabelTitle,
-              _formatPathLabel(message.hopCount, l10n),
+              _formatPathLabel(realHopCount(message.hopCount, hashWidth), l10n),
             ),
             if (observedLabel != null)
               _buildDetailRow(l10n.channelPath_observedLabel, observedLabel),
@@ -160,6 +157,7 @@ class ChannelMessagePathScreen extends StatelessWidget {
 
   Widget _buildPathVariants(BuildContext context, List<Uint8List> variants) {
     final l10n = context.l10n;
+    final hashWidth = context.read<MeshCoreConnector>().pathHashByteWidth;
     return Column(
       crossAxisAlignment: CrossAxisAlignment.start,
       children: [
@@ -171,15 +169,10 @@ class ChannelMessagePathScreen extends StatelessWidget {
               title: Text(
                 l10n.channelPath_observedPathTitle(
                   i + 1,
-                  _formatHopCount(
-                    variants[i].length ~/ message.pathHashSize,
-                    l10n,
-                  ),
+                  _formatHopCount(variants[i].length ~/ hashWidth, l10n),
                 ),
               ),
-              subtitle: Text(
-                _formatPathPrefixes(variants[i], message.pathHashSize),
-              ),
+              subtitle: Text(_formatPathPrefixes(variants[i], hashWidth)),
               trailing: const Icon(Icons.map_outlined, size: 20),
               onTap: () => _openPathMap(
                 context,
@@ -474,11 +467,12 @@ class _ChannelMessagePathMapScreenState
             : selectedPathTmp;
 
         final selectedIndex = _indexForPath(selectedPath, observedPaths);
+        final hashWidth = connector.pathHashByteWidth;
         final hops = _buildPathHops(
           selectedPath,
           connector,
           context.l10n,
-          widget.message.pathHashSize,
+          hashWidth,
         );
 
         final points = <LatLng>[];
@@ -520,7 +514,7 @@ class _ChannelMessagePathMapScreenState
             ? LatLngBounds.fromPoints(points)
             : null;
         final mapKey = ValueKey(
-          '${_formatPathPrefixes(selectedPath, widget.message.pathHashSize)},${context.l10n.pathTrace_you}',
+          '${_formatPathPrefixes(selectedPath, hashWidth)},${context.l10n.pathTrace_you}',
         );
         _pathDistance = _getPathDistance(points);
 
@@ -633,6 +627,7 @@ class _ChannelMessagePathMapScreenState
     ValueChanged<int> onSelected,
   ) {
     final l10n = context.l10n;
+    final hashWidth = context.read<MeshCoreConnector>().pathHashByteWidth;
     final selectedPath = paths[selectedIndex];
     final label = selectedPath.isPrimary
         ? l10n.channelPath_primaryPath(selectedIndex + 1)
@@ -663,7 +658,7 @@ class _ChannelMessagePathMapScreenState
                           value: i,
                           child: Text(
                             '${paths[i].isPrimary ? l10n.channelPath_primaryPath(i + 1) : l10n.channelPath_pathLabel(i + 1)}'
-                            ' • ${_formatHopCount(paths[i].pathBytes.length ~/ widget.message.pathHashSize, l10n)}',
+                            ' • ${_formatHopCount(paths[i].pathBytes.length ~/ hashWidth, l10n)}',
                           ),
                         ),
                     ],
@@ -677,10 +672,7 @@ class _ChannelMessagePathMapScreenState
                 Text(
                   l10n.channelPath_selectedPathLabel(
                     label,
-                    _formatPathPrefixes(
-                      selectedPath.pathBytes,
-                      widget.message.pathHashSize,
-                    ),
+                    _formatPathPrefixes(selectedPath.pathBytes, hashWidth),
                   ),
                   style: TextStyle(color: Colors.grey[700], fontSize: 12),
                 ),
@@ -936,14 +928,14 @@ List<_PathHop> _buildPathHops(
 ) {
   if (pathBytes.isEmpty) return const [];
   final w = hashWidth < 1 ? 1 : hashWidth;
-  final candidatesByPrefix = <int, List<Contact>>{};
+  final candidatesByPrefix = <String, List<Contact>>{};
   final allContacts = connector.allContacts;
   for (final contact in allContacts) {
-    if (contact.publicKey.isEmpty) continue;
+    if (contact.publicKey.length < w) continue;
     if (contact.type != advTypeRepeater && contact.type != advTypeRoom) {
       continue;
     }
-    final prefix = contact.publicKey.first;
+    final prefix = _formatHash(contact.publicKey.sublist(0, w));
     candidatesByPrefix.putIfAbsent(prefix, () => <Contact>[]).add(contact);
   }
   for (final candidates in candidatesByPrefix.values) {
@@ -960,7 +952,7 @@ List<_PathHop> _buildPathHops(
   final hops = <_PathHop>[];
   for (var i = 0; i + w <= pathBytes.length; i += w) {
     final hash = pathBytes.sublist(i, i + w);
-    final prefixKey = hash[0];
+    final prefixKey = _formatHash(hash);
     final searchPoint = i == 0 ? startPoint : previousPosition;
     final candidates = candidatesByPrefix[prefixKey];
     Contact? contact;

lib/screens/settings_screen.dart

@@ -57,7 +57,7 @@ class _SettingsScreenState extends State<SettingsScreen> {
     final packageInfo = await PackageInfo.fromPlatform();
     if (!mounted) return;
     setState(() {
-      _appVersion = packageInfo.version;
+      _appVersion = '${packageInfo.version}+${packageInfo.buildNumber}';
     });
   }
 

pubspec.yaml

@@ -16,7 +16,7 @@ publish_to: 'none' # Remove this line if you wish to publish to pub.dev
 # https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
 # In Windows, build-name is used as the major, minor, and patch parts
 # of the product and file versions while build-number is used as the build suffix.
-version: 1.1.2-beta.3+33
+version: 1.1.2-beta.4+36
 
 environment:
   sdk: ^3.9.2

test/connector/path_hash_test.dart

@@ -0,0 +1,32 @@
+// Path-hash width / hop-count decode (#112). The firmware path-length byte is a
+// BYTE count of the hop-hash array, not a hop count, so at a 2-byte hash width a
+// single 2-byte hop reports 2. realHopCount divides by the device width to get
+// true hops; the Packet Path screen slices and matches at the device width so a
+// 2-byte hash like 6A3D resolves to one repeater instead of two 1-byte hops.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:meshcore_open/connector/meshcore_protocol.dart';
+
+void main() {
+  group('realHopCount', () {
+    test('divides path byte-length by hash width', () {
+      // The bug: one 2-byte hop (6A3D) reported byteLen 2 -> shown as "2 hops".
+      expect(realHopCount(2, 2), 1);
+      expect(realHopCount(4, 2), 2);
+      expect(realHopCount(6, 3), 2);
+    });
+
+    test('is a no-op at 1-byte width (no regression for legacy nets)', () {
+      expect(realHopCount(3, 1), 3);
+    });
+
+    test('treats width < 1 as 1', () {
+      expect(realHopCount(3, 0), 3);
+    });
+
+    test('passes null (unknown) and negative (flood) sentinels through', () {
+      expect(realHopCount(null, 2), isNull);
+      expect(realHopCount(-1, 2), -1);
+    });
+  });
+}