Mesh gossip (#381)

* wip mesh graph

* gossip fix

* gossip works

* source-based routing wip

* log

app/src/main/java/com/bitchat/android/mesh/BluetoothConnectionManager.kt

@@ -247,6 +247,16 @@ class BluetoothConnectionManager(
             serverManager.getCharacteristic()
         )
     }
+
+    fun sendToPeer(peerID: String, routed: RoutedPacket): Boolean {
+        if (!isActive) return false
+        return packetBroadcaster.sendToPeer(
+            peerID,
+            routed,
+            serverManager.getGattServer(),
+            serverManager.getCharacteristic()
+        )
+    }
     
 
     // Expose role controls for debug UI

app/src/main/java/com/bitchat/android/mesh/BluetoothMeshService.kt

@@ -408,6 +408,10 @@ class BluetoothMeshService(private val context: Context) {
             override fun relayPacket(routed: RoutedPacket) {
                 connectionManager.broadcastPacket(routed)
             }
+
+            override fun sendToPeer(peerID: String, routed: RoutedPacket): Boolean {
+                return connectionManager.sendToPeer(peerID, routed)
+            }
         }
         
         // BluetoothConnectionManager delegates
@@ -688,11 +692,25 @@ class BluetoothMeshService(private val context: Context) {
             
             // Create iOS-compatible IdentityAnnouncement with TLV encoding
             val announcement = IdentityAnnouncement(nickname, staticKey, signingKey)
-            val tlvPayload = announcement.encode()
+            var tlvPayload = announcement.encode()
             if (tlvPayload == null) {
                 Log.e(TAG, "Failed to encode announcement as TLV")
                 return@launch
             }
+
+            // Append gossip TLV containing up to 10 direct neighbors (compact IDs)
+            try {
+                val directPeers = getDirectPeerIDsForGossip()
+                if (directPeers.isNotEmpty()) {
+                    val gossip = com.bitchat.android.services.meshgraph.GossipTLV.encodeNeighbors(directPeers)
+                    tlvPayload = tlvPayload + gossip
+                }
+                // Always update our own node in the mesh graph with the neighbor list we used
+                try {
+                    com.bitchat.android.services.meshgraph.MeshGraphService.getInstance()
+                        .updateFromAnnouncement(myPeerID, nickname, directPeers, System.currentTimeMillis().toULong())
+                } catch (_: Exception) { }
+            } catch (_: Exception) { }
             
             val announcePacket = BitchatPacket(
                 type = MessageType.ANNOUNCE.value,
@@ -735,11 +753,25 @@ class BluetoothMeshService(private val context: Context) {
         
         // Create iOS-compatible IdentityAnnouncement with TLV encoding
         val announcement = IdentityAnnouncement(nickname, staticKey, signingKey)
-        val tlvPayload = announcement.encode()
+        var tlvPayload = announcement.encode()
         if (tlvPayload == null) {
             Log.e(TAG, "Failed to encode peer announcement as TLV")
             return
         }
+
+        // Append gossip TLV containing up to 10 direct neighbors (compact IDs)
+        try {
+            val directPeers = getDirectPeerIDsForGossip()
+            if (directPeers.isNotEmpty()) {
+                val gossip = com.bitchat.android.services.meshgraph.GossipTLV.encodeNeighbors(directPeers)
+                tlvPayload = tlvPayload + gossip
+            }
+            // Always update our own node in the mesh graph with the neighbor list we used
+            try {
+                com.bitchat.android.services.meshgraph.MeshGraphService.getInstance()
+                    .updateFromAnnouncement(myPeerID, nickname, directPeers, System.currentTimeMillis().toULong())
+            } catch (_: Exception) { }
+        } catch (_: Exception) { }
         
         val packet = BitchatPacket(
             type = MessageType.ANNOUNCE.value,
@@ -758,6 +790,20 @@ class BluetoothMeshService(private val context: Context) {
         Log.d(TAG, "Sent iOS-compatible signed TLV peer announce to $peerID (${tlvPayload.size} bytes)")
     }
 
+    /**
+     * Collect up to 10 direct neighbors for gossip TLV.
+     */
+    private fun getDirectPeerIDsForGossip(): List<String> {
+        return try {
+            // Prefer verified peers that are currently marked as direct
+            val verified = peerManager.getVerifiedPeers()
+            val direct = verified.filter { it.value.isDirectConnection }.keys.toList()
+            direct.take(10)
+        } catch (_: Exception) {
+            emptyList()
+        }
+    }
+
     /**
      * Send leave announcement
      */
@@ -939,21 +985,37 @@ class BluetoothMeshService(private val context: Context) {
      */
     private fun signPacketBeforeBroadcast(packet: BitchatPacket): BitchatPacket {
         return try {
+            // Optionally compute and attach a source route for addressed packets
+            val withRoute = try {
+                val rec = packet.recipientID
+                if (rec != null && !rec.contentEquals(SpecialRecipients.BROADCAST)) {
+                    val dest = rec.joinToString("") { b -> "%02x".format(b) }
+                    val path = com.bitchat.android.services.meshgraph.RoutePlanner.shortestPath(myPeerID, dest)
+                    if (path != null && path.size >= 3) {
+                        // Exclude first (sender) and last (recipient); only intermediates
+                        val intermediates = path.subList(1, path.size - 1)
+                        val hopsBytes = intermediates.map { hexStringToByteArray(it) }
+                        Log.d(TAG, "✅ Signed packet type ${packet.type} (route ${hopsBytes.size} hops: $intermediates)")
+                        packet.copy(route = hopsBytes)
+                    } else packet.copy(route = null)
+                } else packet
+            } catch (_: Exception) { packet }
+
             // Get the canonical packet data for signing (without signature)
-            val packetDataForSigning = packet.toBinaryDataForSigning()
+            val packetDataForSigning = withRoute.toBinaryDataForSigning()
             if (packetDataForSigning == null) {
                 Log.w(TAG, "Failed to encode packet type ${packet.type} for signing, sending unsigned")
-                return packet
+                return withRoute
             }
             
             // Sign the packet data using our signing key
             val signature = encryptionService.signData(packetDataForSigning)
             if (signature != null) {
                 Log.d(TAG, "✅ Signed packet type ${packet.type} (signature ${signature.size} bytes)")
-                packet.copy(signature = signature)
+                withRoute.copy(signature = signature)
             } else {
                 Log.w(TAG, "Failed to sign packet type ${packet.type}, sending unsigned")
-                packet
+                withRoute
             }
         } catch (e: Exception) {
             Log.w(TAG, "Error signing packet type ${packet.type}: ${e.message}, sending unsigned")

app/src/main/java/com/bitchat/android/mesh/BluetoothPacketBroadcaster.kt

@@ -159,6 +159,46 @@ class BluetoothPacketBroadcaster(
             }
         }
     }
+
+    /**
+     * Targeted send to a specific peer (by peerID) if directly connected.
+     * Returns true if sent to at least one matching connection.
+     */
+    fun sendToPeer(
+        targetPeerID: String,
+        routed: RoutedPacket,
+        gattServer: BluetoothGattServer?,
+        characteristic: BluetoothGattCharacteristic?
+    ): Boolean {
+        val packet = routed.packet
+        val data = packet.toBinaryData() ?: return false
+        val typeName = MessageType.fromValue(packet.type)?.name ?: packet.type.toString()
+        val senderPeerID = routed.peerID ?: packet.senderID.toHexString()
+        val incomingAddr = routed.relayAddress
+        val incomingPeer = incomingAddr?.let { connectionTracker.addressPeerMap[it] }
+        val senderNick = senderPeerID.let { pid -> nicknameResolver?.invoke(pid) }
+
+        // Try server-side connections first
+        val targetDevice = connectionTracker.getSubscribedDevices()
+            .firstOrNull { connectionTracker.addressPeerMap[it.address] == targetPeerID }
+        if (targetDevice != null) {
+            if (notifyDevice(targetDevice, data, gattServer, characteristic)) {
+                logPacketRelay(typeName, senderPeerID, senderNick, incomingPeer, incomingAddr, targetPeerID, targetDevice.address, packet.ttl)
+                return true
+            }
+        }
+
+        // Try client-side connections next
+        val targetConn = connectionTracker.getConnectedDevices().values
+            .firstOrNull { connectionTracker.addressPeerMap[it.device.address] == targetPeerID }
+        if (targetConn != null) {
+            if (writeToDeviceConn(targetConn, data)) {
+                logPacketRelay(typeName, senderPeerID, senderNick, incomingPeer, incomingAddr, targetPeerID, targetConn.device.address, packet.ttl)
+                return true
+            }
+        }
+        return false
+    }
     
     /**
      * Internal broadcast implementation - runs in serialized actor context

app/src/main/java/com/bitchat/android/mesh/MessageHandler.kt

@@ -240,6 +240,13 @@ class MessageHandler(private val myPeerID: String) {
             previousPeerID = null
         )
         
+        // Update mesh graph from gossip neighbors (only if TLV present)
+        try {
+            val neighborsOrNull = com.bitchat.android.services.meshgraph.GossipTLV.decodeNeighborsFromAnnouncementPayload(packet.payload)
+            com.bitchat.android.services.meshgraph.MeshGraphService.getInstance()
+                .updateFromAnnouncement(peerID, nickname, neighborsOrNull, packet.timestamp)
+        } catch (_: Exception) { }
+
         Log.d(TAG, "✅ Processed verified TLV announce: stored identity for $peerID")
         return isFirstAnnounce
     }

app/src/main/java/com/bitchat/android/mesh/PacketProcessor.kt

@@ -112,6 +112,9 @@ class PacketProcessor(private val myPeerID: String) {
             override fun broadcastPacket(routed: RoutedPacket) {
                 delegate?.relayPacket(routed)
             }
+            override fun sendToPeer(peerID: String, routed: RoutedPacket): Boolean {
+                return delegate?.sendToPeer(peerID, routed) ?: false
+            }
         }
     }
     
@@ -310,4 +313,5 @@ interface PacketProcessorDelegate {
     fun sendAnnouncementToPeer(peerID: String)
     fun sendCachedMessages(peerID: String)
     fun relayPacket(routed: RoutedPacket)
+    fun sendToPeer(peerID: String, routed: RoutedPacket): Boolean
 }

app/src/main/java/com/bitchat/android/mesh/PacketRelayManager.kt

@@ -65,9 +65,35 @@ class PacketRelayManager(private val myPeerID: String) {
         val relayPacket = packet.copy(ttl = (packet.ttl - 1u).toUByte())
         Log.d(TAG, "Decremented TTL from ${'$'}{packet.ttl} to ${'$'}{relayPacket.ttl}")
         
+        // Source-based routing: if route is set and includes us, try targeted next-hop forwarding
+        val route = relayPacket.route
+        if (!route.isNullOrEmpty()) {
+            val myIdBytes = hexStringToPeerBytes(myPeerID)
+            val index = route.indexOfFirst { it.contentEquals(myIdBytes) }
+            if (index >= 0) {
+                val nextHopIdHex: String? = run {
+                    val nextIndex = index + 1
+                    if (nextIndex < route.size) {
+                        route[nextIndex].toHexString()
+                    } else {
+                        // We are the last intermediate; try final recipient as next hop
+                        relayPacket.recipientID?.toHexString()
+                    }
+                }
+                if (nextHopIdHex != null) {
+                    val success = try { delegate?.sendToPeer(nextHopIdHex, RoutedPacket(relayPacket, peerID, routed.relayAddress)) } catch (_: Exception) { false } ?: false
+                    if (success) {
+                        Log.i(TAG, "📦 Source-route relay: ${myPeerID.take(8)} -> ${nextHopIdHex.take(8)} (type ${'$'}{packet.type}, TTL ${'$'}{relayPacket.ttl})")
+                        return
+                    } else {
+                        Log.w(TAG, "Source-route next hop ${nextHopIdHex.take(8)} not directly connected; falling back to broadcast")
+                    }
+                }
+            }
+        }
+
         // Apply relay logic based on packet type and debug switch
         val shouldRelay = isRelayEnabled() && shouldRelayPacket(relayPacket, peerID)
-        
         if (shouldRelay) {
             relayPacket(RoutedPacket(relayPacket, peerID, routed.relayAddress))
         } else {
@@ -206,4 +232,17 @@ interface PacketRelayManagerDelegate {
     
     // Packet operations
     fun broadcastPacket(routed: RoutedPacket)
+    fun sendToPeer(peerID: String, routed: RoutedPacket): Boolean
+}
+
+private fun hexStringToPeerBytes(hex: String): ByteArray {
+    val result = ByteArray(8)
+    var idx = 0
+    var out = 0
+    while (idx + 1 < hex.length && out < 8) {
+        val b = hex.substring(idx, idx + 2).toIntOrNull(16)?.toByte() ?: 0
+        result[out++] = b
+        idx += 2
+    }
+    return result
 }

app/src/main/java/com/bitchat/android/protocol/BinaryProtocol.kt

@@ -57,7 +57,8 @@ data class BitchatPacket(
     val timestamp: ULong,
     val payload: ByteArray,
     var signature: ByteArray? = null,  // Changed from val to var for packet signing
-    var ttl: UByte
+    var ttl: UByte,
+    var route: List<ByteArray>? = null // Optional source route: ordered list of peerIDs (8 bytes each), not including sender and final recipient
 ) : Parcelable {
 
     constructor(
@@ -95,7 +96,8 @@ data class BitchatPacket(
             timestamp = timestamp,
             payload = payload,
             signature = null, // Remove signature for signing
-            ttl = 0u // Use fixed TTL=0 for signing to ensure relay compatibility
+            ttl = 0u, // Use fixed TTL=0 for signing to ensure relay compatibility
+            route = route
         )
         return BinaryProtocol.encode(unsignedPacket)
     }
@@ -147,6 +149,11 @@ data class BitchatPacket(
             if (!signature.contentEquals(other.signature)) return false
         } else if (other.signature != null) return false
         if (ttl != other.ttl) return false
+        if (route != null || other.route != null) {
+            val a = route?.map { it.toList() } ?: emptyList()
+            val b = other.route?.map { it.toList() } ?: emptyList()
+            if (a != b) return false
+        }
 
         return true
     }
@@ -160,6 +167,7 @@ data class BitchatPacket(
         result = 31 * result + payload.contentHashCode()
         result = 31 * result + (signature?.contentHashCode() ?: 0)
         result = 31 * result + ttl.hashCode()
+        result = 31 * result + (route?.fold(1) { acc, bytes -> 31 * acc + bytes.contentHashCode() } ?: 0)
         return result
     }
 }
@@ -177,6 +185,7 @@ object BinaryProtocol {
         const val HAS_RECIPIENT: UByte = 0x01u
         const val HAS_SIGNATURE: UByte = 0x02u
         const val IS_COMPRESSED: UByte = 0x04u
+        const val HAS_ROUTE: UByte = 0x08u
     }
     
     fun encode(packet: BitchatPacket): ByteArray? {
@@ -215,6 +224,9 @@ object BinaryProtocol {
             if (isCompressed) {
                 flags = flags or Flags.IS_COMPRESSED
             }
+            if (!packet.route.isNullOrEmpty()) {
+                flags = flags or Flags.HAS_ROUTE
+            }
             buffer.put(flags.toByte())
             
             // Payload length (2 bytes, big-endian) - includes original size if compressed
@@ -236,6 +248,14 @@ object BinaryProtocol {
                     buffer.put(ByteArray(RECIPIENT_ID_SIZE - recipientBytes.size))
                 }
             }
+
+            // Route (optional): 1 byte count + N*8 bytes
+            packet.route?.let { routeList ->
+                val cleaned = routeList.map { bytes -> bytes.take(SENDER_ID_SIZE).toByteArray().let { if (it.size < SENDER_ID_SIZE) it + ByteArray(SENDER_ID_SIZE - it.size) else it } }
+                val count = cleaned.size.coerceAtMost(255)
+                buffer.put(count.toByte())
+                cleaned.take(count).forEach { hop -> buffer.put(hop) }
+            }
             
             // Payload (with original size prepended if compressed)
             if (isCompressed) {
@@ -302,6 +322,7 @@ object BinaryProtocol {
             val hasRecipient = (flags and Flags.HAS_RECIPIENT) != 0u.toUByte()
             val hasSignature = (flags and Flags.HAS_SIGNATURE) != 0u.toUByte()
             val isCompressed = (flags and Flags.IS_COMPRESSED) != 0u.toUByte()
+            val hasRoute = (flags and Flags.HAS_ROUTE) != 0u.toUByte()
             
             // Payload length
             val payloadLength = buffer.getShort().toUShort()
@@ -309,6 +330,15 @@ object BinaryProtocol {
             // Calculate expected total size
             var expectedSize = HEADER_SIZE + SENDER_ID_SIZE + payloadLength.toInt()
             if (hasRecipient) expectedSize += RECIPIENT_ID_SIZE
+            var routeCount = 0
+            if (hasRoute) {
+                // Peek count (1 byte) without consuming buffer for now
+                val mark = buffer.position()
+                if (raw.size >= mark + 1) {
+                    routeCount = raw[mark].toUByte().toInt()
+                }
+                expectedSize += 1 + (routeCount * SENDER_ID_SIZE)
+            }
             if (hasSignature) expectedSize += SIGNATURE_SIZE
             
             if (raw.size < expectedSize) return null
@@ -324,6 +354,18 @@ object BinaryProtocol {
                 recipientBytes
             } else null
             
+            // Route (optional)
+            val route: List<ByteArray>? = if (hasRoute) {
+                val count = buffer.get().toUByte().toInt()
+                val hops = mutableListOf<ByteArray>()
+                repeat(count) {
+                    val hop = ByteArray(SENDER_ID_SIZE)
+                    buffer.get(hop)
+                    hops.add(hop)
+                }
+                hops
+            } else null
+
             // Payload
             val payload = if (isCompressed) {
                 // First 2 bytes are original size
@@ -357,7 +399,8 @@ object BinaryProtocol {
                 timestamp = timestamp,
                 payload = payload,
                 signature = signature,
-                ttl = ttl
+                ttl = ttl,
+                route = route
             )
             
         } catch (e: Exception) {

app/src/main/java/com/bitchat/android/services/meshgraph/GossipTLV.kt

@@ -0,0 +1,77 @@
+package com.bitchat.android.services.meshgraph
+
+import android.util.Log
+
+/**
+ * Gossip TLV helpers for embedding direct neighbor peer IDs in ANNOUNCE payloads.
+ * Uses compact TLV: [type=0x04][len=1 byte][value=N*8 bytes of peerIDs]
+ */
+object GossipTLV {
+    // TLV type for a compact list of direct neighbor peerIDs (each 8 bytes)
+    const val DIRECT_NEIGHBORS_TYPE: UByte = 0x04u
+
+    /**
+     * Encode up to 10 unique peerIDs (hex string up to 16 chars) as TLV value.
+     */
+    fun encodeNeighbors(peerIDs: List<String>): ByteArray {
+        val unique = peerIDs.distinct().take(10)
+        val valueBytes = unique.flatMap { id -> hexStringPeerIdTo8Bytes(id).toList() }.toByteArray()
+        if (valueBytes.size > 255) {
+            // Safety check, though 10*8 = 80 bytes, so well under 255
+            Log.w("GossipTLV", "Neighbors value exceeds 255, truncating")
+        }
+        return byteArrayOf(DIRECT_NEIGHBORS_TYPE.toByte(), valueBytes.size.toByte()) + valueBytes
+    }
+
+    /**
+     * Scan a TLV-encoded announce payload and extract neighbor peerIDs.
+     * Returns null if the TLV is not present at all; returns an empty list if present with length 0.
+     */
+    fun decodeNeighborsFromAnnouncementPayload(payload: ByteArray): List<String>? {
+        val result = mutableListOf<String>()
+        var offset = 0
+        while (offset + 2 <= payload.size) {
+            val type = payload[offset].toUByte()
+            val len = payload[offset + 1].toUByte().toInt()
+            offset += 2
+            if (offset + len > payload.size) break
+            val value = payload.sliceArray(offset until offset + len)
+            offset += len
+
+            if (type == DIRECT_NEIGHBORS_TYPE) {
+                // Value is N*8 bytes of peer IDs
+                var pos = 0
+                while (pos + 8 <= value.size) {
+                    val idBytes = value.sliceArray(pos until pos + 8)
+                    result.add(bytesToPeerIdHex(idBytes))
+                    pos += 8
+                }
+                return result // present (possibly empty)
+            }
+        }
+        // Not present
+        return null
+    }
+
+    private fun hexStringPeerIdTo8Bytes(hexString: String): ByteArray {
+        val clean = hexString.lowercase().take(16)
+        val result = ByteArray(8) { 0 }
+        var idx = 0
+        var out = 0
+        while (idx + 1 < clean.length && out < 8) {
+            val byteStr = clean.substring(idx, idx + 2)
+            val b = byteStr.toIntOrNull(16)?.toByte() ?: 0
+            result[out++] = b
+            idx += 2
+        }
+        return result
+    }
+
+    private fun bytesToPeerIdHex(bytes: ByteArray): String {
+        val sb = StringBuilder()
+        for (b in bytes.take(8)) {
+            sb.append(String.format("%02x", b))
+        }
+        return sb.toString()
+    }
+}

app/src/main/java/com/bitchat/android/services/meshgraph/MeshGraphService.kt

@@ -0,0 +1,102 @@
+package com.bitchat.android.services.meshgraph
+
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import java.util.concurrent.ConcurrentHashMap
+
+/**
+ * Maintains an internal undirected graph of the mesh based on gossip.
+ * Nodes are peers (peerID), edges are direct connections.
+ */
+class MeshGraphService private constructor() {
+    data class GraphNode(val peerID: String, val nickname: String?)
+    data class GraphEdge(val a: String, val b: String)
+    data class GraphSnapshot(val nodes: List<GraphNode>, val edges: List<GraphEdge>)
+
+    // Map peerID -> nickname (may be null if unknown)
+    private val nicknames = ConcurrentHashMap<String, String?>()
+    // Adjacency (undirected): peerID -> set of neighbor peerIDs
+    private val adjacency = ConcurrentHashMap<String, MutableSet<String>>()
+    // Latest announcement timestamp per peer (ULong from packet)
+    private val lastUpdate = ConcurrentHashMap<String, ULong>()
+
+    private val _graphState = MutableStateFlow(GraphSnapshot(emptyList(), emptyList()))
+    val graphState: StateFlow<GraphSnapshot> = _graphState.asStateFlow()
+
+    /**
+     * Update graph from a verified announcement.
+     * Replaces previous neighbors for origin if this is newer (by timestamp).
+     */
+    fun updateFromAnnouncement(originPeerID: String, originNickname: String?, neighborsOrNull: List<String>?, timestamp: ULong) {
+        synchronized(this) {
+            // Always update nickname if provided
+            if (originNickname != null) nicknames[originPeerID] = originNickname
+
+            // If no neighbors TLV present, do not modify edges or timestamps
+            if (neighborsOrNull == null) {
+                publishSnapshot()
+                return
+            }
+
+            // Newer-only replacement per origin (based on TLV-bearing announcements only)
+            val prevTs = lastUpdate[originPeerID]
+            if (prevTs != null && prevTs >= timestamp) {
+                // Older or equal TLV-bearing update: ignore
+                return
+            }
+            lastUpdate[originPeerID] = timestamp
+
+            // Remove old symmetric edges contributed by this origin
+            val prevNeighbors = adjacency[originPeerID]?.toSet().orEmpty()
+            prevNeighbors.forEach { n ->
+                adjacency[n]?.remove(originPeerID)
+            }
+
+            // Replace origin's adjacency with new set (may be empty)
+            val newSet = neighborsOrNull.distinct().take(10).filter { it != originPeerID }.toMutableSet()
+            adjacency[originPeerID] = newSet
+            // Ensure undirected edges
+            newSet.forEach { n ->
+                adjacency.putIfAbsent(n, mutableSetOf())
+                adjacency[n]?.add(originPeerID)
+            }
+
+            publishSnapshot()
+        }
+    }
+
+    fun updateNickname(peerID: String, nickname: String?) {
+        if (nickname == null) return
+        nicknames[peerID] = nickname
+        publishSnapshot()
+    }
+
+    private fun publishSnapshot() {
+        val nodes = mutableSetOf<String>()
+        adjacency.forEach { (a, neighbors) ->
+            nodes.add(a)
+            nodes.addAll(neighbors)
+        }
+        // Merge in nicknames-only nodes
+        nodes.addAll(nicknames.keys)
+
+        val nodeList = nodes.map { GraphNode(it, nicknames[it]) }.sortedBy { it.peerID }
+        val edgeSet = mutableSetOf<Pair<String, String>>()
+        adjacency.forEach { (a, ns) ->
+            ns.forEach { b ->
+                val (x, y) = if (a <= b) a to b else b to a
+                edgeSet.add(x to y)
+            }
+        }
+        val edges = edgeSet.map { GraphEdge(it.first, it.second) }.sortedWith(compareBy({ it.a }, { it.b }))
+        _graphState.value = GraphSnapshot(nodeList, edges)
+    }
+
+    companion object {
+        @Volatile private var INSTANCE: MeshGraphService? = null
+        fun getInstance(): MeshGraphService = INSTANCE ?: synchronized(this) {
+            INSTANCE ?: MeshGraphService().also { INSTANCE = it }
+        }
+    }
+}

app/src/main/java/com/bitchat/android/services/meshgraph/RoutePlanner.kt

@@ -0,0 +1,66 @@
+package com.bitchat.android.services.meshgraph
+
+import android.util.Log
+import java.util.PriorityQueue
+
+/**
+ * Computes shortest paths on the current mesh graph snapshot using Dijkstra.
+ * Assumes unit edge weights.
+ */
+object RoutePlanner {
+    private const val TAG = "RoutePlanner"
+
+    /**
+     * Return full path [src, ..., dst] if reachable, else null.
+     */
+    fun shortestPath(src: String, dst: String): List<String>? {
+        if (src == dst) return listOf(src)
+        val snapshot = MeshGraphService.getInstance().graphState.value
+        val neighbors = mutableMapOf<String, MutableSet<String>>()
+        snapshot.edges.forEach { e ->
+            neighbors.getOrPut(e.a) { mutableSetOf() }.add(e.b)
+            neighbors.getOrPut(e.b) { mutableSetOf() }.add(e.a)
+        }
+        // Ensure nodes known even if isolated
+        snapshot.nodes.forEach { n -> neighbors.putIfAbsent(n.peerID, mutableSetOf()) }
+
+        if (!neighbors.containsKey(src) || !neighbors.containsKey(dst)) return null
+
+        val dist = mutableMapOf<String, Int>()
+        val prev = mutableMapOf<String, String?>()
+        val pq = PriorityQueue<Pair<String, Int>>(compareBy { it.second })
+
+        neighbors.keys.forEach { v ->
+            dist[v] = if (v == src) 0 else Int.MAX_VALUE
+            prev[v] = null
+        }
+        pq.add(src to 0)
+
+        while (pq.isNotEmpty()) {
+            val (u, d) = pq.poll()
+            if (d > (dist[u] ?: Int.MAX_VALUE)) continue
+            if (u == dst) break
+            neighbors[u]?.forEach { v ->
+                val alt = d + 1
+                if (alt < (dist[v] ?: Int.MAX_VALUE)) {
+                    dist[v] = alt
+                    prev[v] = u
+                    pq.add(v to alt)
+                }
+            }
+        }
+
+        if ((dist[dst] ?: Int.MAX_VALUE) == Int.MAX_VALUE) return null
+
+        val path = mutableListOf<String>()
+        var cur: String? = dst
+        while (cur != null) {
+            path.add(cur)
+            cur = prev[cur]
+        }
+        path.reverse()
+        Log.d(TAG, "Computed path $path")
+        return path
+    }
+}
+

app/src/main/java/com/bitchat/android/ui/debug/DebugSettingsSheet.kt

@@ -24,7 +24,92 @@ import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
 import androidx.compose.ui.draw.rotate
 import com.bitchat.android.mesh.BluetoothMeshService
+import com.bitchat.android.services.meshgraph.MeshGraphService
 import kotlinx.coroutines.launch
+import androidx.compose.ui.graphics.toArgb
+import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
+import androidx.compose.ui.graphics.nativeCanvas
+
+@Composable
+fun MeshTopologySection() {
+    val colorScheme = MaterialTheme.colorScheme
+    val graphService = remember { MeshGraphService.getInstance() }
+    val snapshot by graphService.graphState.collectAsState()
+
+    Surface(shape = RoundedCornerShape(12.dp), color = colorScheme.surfaceVariant.copy(alpha = 0.2f)) {
+        Column(Modifier.padding(16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+            Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                Icon(Icons.Filled.SettingsEthernet, contentDescription = null, tint = Color(0xFF8E8E93))
+                Text("mesh topology", fontFamily = FontFamily.Monospace, fontSize = 14.sp, fontWeight = FontWeight.Medium)
+            }
+            val nodes = snapshot.nodes
+            val edges = snapshot.edges
+            val empty = nodes.isEmpty()
+            if (empty) {
+                Text("no gossip yet", fontFamily = FontFamily.Monospace, fontSize = 11.sp, color = colorScheme.onSurface.copy(alpha = 0.6f))
+            } else {
+                androidx.compose.foundation.Canvas(Modifier.fillMaxWidth().height(220.dp).background(colorScheme.surface.copy(alpha = 0.4f))) {
+                    val w = size.width
+                    val h = size.height
+                    val cx = w / 2f
+                    val cy = h / 2f
+                    val radius = (minOf(w, h) * 0.36f)
+                    val n = nodes.size
+                    if (n == 1) {
+                        // Single node centered
+                        drawCircle(color = Color(0xFF00C851), radius = 12f, center = androidx.compose.ui.geometry.Offset(cx, cy))
+                    } else {
+                        // Circular layout
+                        val positions = nodes.mapIndexed { i, node ->
+                            val angle = (2 * Math.PI * i.toDouble()) / n
+                            val x = cx + (radius * Math.cos(angle)).toFloat()
+                            val y = cy + (radius * Math.sin(angle)).toFloat()
+                            node.peerID to androidx.compose.ui.geometry.Offset(x, y)
+                        }.toMap()
+
+                        // Draw edges
+                        edges.forEach { e ->
+                            val p1 = positions[e.a]
+                            val p2 = positions[e.b]
+                            if (p1 != null && p2 != null) {
+                                drawLine(color = Color(0xFF4A90E2), start = p1, end = p2, strokeWidth = 2f)
+                            }
+                        }
+
+                        // Draw nodes
+                        nodes.forEach { node ->
+                            val pos = positions[node.peerID] ?: androidx.compose.ui.geometry.Offset(cx, cy)
+                            drawCircle(color = Color(0xFF00C851), radius = 10f, center = pos)
+                        }
+
+                        // Draw labels near nodes (nickname or short ID)
+                        val labelColor = colorScheme.onSurface.toArgb()
+                        val textSizePx = 10.sp.toPx()
+                        drawIntoCanvas { canvas ->
+                            val paint = android.graphics.Paint().apply {
+                                isAntiAlias = true
+                                color = labelColor
+                                textSize = textSizePx
+                            }
+                            nodes.forEach { node ->
+                                val pos = positions[node.peerID] ?: androidx.compose.ui.geometry.Offset(cx, cy)
+                                val label = (node.nickname?.takeIf { it.isNotBlank() } ?: node.peerID.take(8))
+                                canvas.nativeCanvas.drawText(label, pos.x + 12f, pos.y - 12f, paint)
+                            }
+                        }
+                    }
+                }
+                // Label list for clarity under the canvas
+                LazyColumn(modifier = Modifier.fillMaxWidth().heightIn(max = 140.dp)) {
+                    items(nodes) { node ->
+                        val label = "${node.peerID.take(8)} • ${node.nickname ?: "unknown"}"
+                        Text(label, fontFamily = FontFamily.Monospace, fontSize = 11.sp, color = colorScheme.onSurface.copy(alpha = 0.85f))
+                    }
+                }
+            }
+        }
+    }
+}
 
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable
@@ -124,6 +209,11 @@ fun DebugSettingsSheet(
                 }
             }
 
+            // Mesh topology visualization (moved below verbose logging)
+            item {
+                MeshTopologySection()
+            }
+
             // GATT controls
             item {
                 Surface(shape = RoundedCornerShape(12.dp), color = colorScheme.surfaceVariant.copy(alpha = 0.2f)) {
@@ -250,39 +340,82 @@ fun DebugSettingsSheet(
                                     }
                                 }
                             }
-                            // Left gutter layout: unit + ticks neatly aligned
-                            Row(Modifier.fillMaxSize()) {
-                                Box(Modifier.width(leftGutter).fillMaxHeight()) {
-                                    // Unit label on the far left, centered vertically
-                                    Text(
-                                        "p/s",
-                                        fontFamily = FontFamily.Monospace,
-                                        fontSize = 10.sp,
-                                        color = colorScheme.onSurface.copy(alpha = 0.7f),
-                                        modifier = Modifier.align(Alignment.CenterStart).padding(start = 2.dp).rotate(-90f)
-                                    )
-                                    // Tick labels right-aligned in gutter, top and bottom aligned
-                                    Text(
-                                        "${maxVal.toInt()}",
-                                        fontFamily = FontFamily.Monospace,
-                                        fontSize = 10.sp,
-                                        color = colorScheme.onSurface.copy(alpha = 0.7f),
-                                        modifier = Modifier.align(Alignment.TopEnd).padding(end = 4.dp, top = 0.dp)
-                                    )
-                                    Text(
-                                        "0",
-                                        fontFamily = FontFamily.Monospace,
-                                        fontSize = 10.sp,
-                                        color = colorScheme.onSurface.copy(alpha = 0.7f),
-                                        modifier = Modifier.align(Alignment.BottomEnd).padding(end = 4.dp, bottom = 0.dp)
-                                    )
-                                }
-                                Spacer(Modifier.weight(1f))
+                            // Y-axis ticks (min/max) in the left margin
+                            Text("0", fontFamily = FontFamily.Monospace, fontSize = 10.sp, color = colorScheme.onSurface.copy(alpha = 0.7f), modifier = Modifier.align(Alignment.BottomStart).padding(start = 4.dp, bottom = 2.dp))
+                            Text("${maxVal.toInt()}", fontFamily = FontFamily.Monospace, fontSize = 10.sp, color = colorScheme.onSurface.copy(alpha = 0.7f), modifier = Modifier.align(Alignment.TopStart).padding(start = 4.dp, top = 2.dp))
+                            // Y-axis unit label (vertical)
+                            Text("p/s", fontFamily = FontFamily.Monospace, fontSize = 9.sp, color = colorScheme.onSurface.copy(alpha = 0.7f), modifier = Modifier.align(Alignment.CenterStart).padding(start = 2.dp).rotate(-90f))
+            }
+        }
+    }
+}
+
+@Composable
+fun MeshTopologySection() {
+    val colorScheme = MaterialTheme.colorScheme
+    val graphService = remember { MeshGraphService.getInstance() }
+    val snapshot by graphService.graphState.collectAsState()
+
+    Surface(shape = RoundedCornerShape(12.dp), color = colorScheme.surfaceVariant.copy(alpha = 0.2f)) {
+        Column(Modifier.padding(16.dp), verticalArrangement = Arrangement.spacedBy(8.dp)) {
+            Row(verticalAlignment = Alignment.CenterVertically, horizontalArrangement = Arrangement.spacedBy(8.dp)) {
+                Icon(Icons.Filled.SettingsEthernet, contentDescription = null, tint = Color(0xFF8E8E93))
+                Text("mesh topology", fontFamily = FontFamily.Monospace, fontSize = 14.sp, fontWeight = FontWeight.Medium)
+            }
+            val nodes = snapshot.nodes
+            val edges = snapshot.edges
+            val empty = nodes.isEmpty()
+            if (empty) {
+                Text("no gossip yet", fontFamily = FontFamily.Monospace, fontSize = 11.sp, color = colorScheme.onSurface.copy(alpha = 0.6f))
+            } else {
+                androidx.compose.foundation.Canvas(Modifier.fillMaxWidth().height(220.dp).background(colorScheme.surface.copy(alpha = 0.4f))) {
+                    val w = size.width
+                    val h = size.height
+                    val cx = w / 2f
+                    val cy = h / 2f
+                    val radius = (minOf(w, h) * 0.36f)
+                    val n = nodes.size
+                    if (n == 1) {
+                        // Single node centered
+                        drawCircle(color = Color(0xFF00C851), radius = 12f, center = androidx.compose.ui.geometry.Offset(cx, cy))
+                    } else {
+                        // Circular layout
+                        val positions = nodes.mapIndexed { i, node ->
+                            val angle = (2 * Math.PI * i.toDouble()) / n
+                            val x = cx + (radius * Math.cos(angle)).toFloat()
+                            val y = cy + (radius * Math.sin(angle)).toFloat()
+                            node.peerID to androidx.compose.ui.geometry.Offset(x, y)
+                        }.toMap()
+
+                        // Draw edges
+                        edges.forEach { e ->
+                            val p1 = positions[e.a]
+                            val p2 = positions[e.b]
+                            if (p1 != null && p2 != null) {
+                                drawLine(color = Color(0xFF4A90E2), start = p1, end = p2, strokeWidth = 2f)
                             }
                         }
+
+                        // Draw nodes
+                        nodes.forEach { node ->
+                            val pos = positions[node.peerID] ?: androidx.compose.ui.geometry.Offset(cx, cy)
+                            drawCircle(color = Color(0xFF00C851), radius = 10f, center = pos)
+                        }
+                    }
+                }
+                // Label list for clarity under the canvas
+                LazyColumn(modifier = Modifier.fillMaxWidth().heightIn(max = 140.dp)) {
+                    items(nodes) { node ->
+                        val label = "${node.peerID.take(8)} • ${node.nickname ?: "unknown"}"
+                        Text(label, fontFamily = FontFamily.Monospace, fontSize = 11.sp, color = colorScheme.onSurface.copy(alpha = 0.85f))
                     }
                 }
             }
+        }
+    }
+}
+
+
 
             // Connected devices
             item {