Bridge dedup: content-derived stable mesh message ID (#1419)

* Bridge dedup keys on a content-derived stable mesh message ID

Public mesh messages carry no message ID on the BLE wire, so every
non-origin device minted a fresh UUID and the bridge's m-tag dedup only
matched on the origin device: duplicate bridged rows, misattributed
"across the bridge" counts, redundant downlink rebroadcasts, and an
m-tag spoof vector (an attacker could claim a victim's message ID).

Every device now derives the same stable ID from the signed wire fields
(sender ID + ms timestamp + trimmed content, SHA256/32 hex) via the new
MeshMessageIdentity — zero BLE wire change. The bridge event's m tag
carries the origin coordinates ["m", senderIDHex, timestampMs] and
receivers recompute the key from those plus the event's own content
instead of trusting a claimed ID; old-format/absent tags fall back to
the event ID as before.

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

* Fix mixed-version message loss: m tag leads with the derived stable ID

The previous layout (["m", senderIDHex, timestampMs]) broke v1.7.0
receivers: their parser takes m[1] unconditionally as the timeline
dedup key whenever the tag has >= 2 elements, so every bridged message
from a new-version sender keyed on the CONSTANT sender hex and
inject-dedup dropped all but the first. The tag is now
["m", <derived stable ID>, senderIDHex, timestampMs]: old parsers get a
per-message-unique m[1] (exactly today's semantics), while the new
parser recomputes the ID from elements 2-3 plus the event's own content
and never trusts element 1, keeping the recompute-don't-trust property.

Also:
- Soften the overstated security claim in MeshMessageIdentity and the
  BridgeService classify comment: forging a chosen ID onto different
  content is infeasible, but all three hash inputs are cleartext on the
  radio, so identical-content front-running by a radio-local attacker
  remains possible (no worse than the unbridged mesh).
- Fix the stale archivedEchoKeys rationale: re-synced copies of others'
  messages now carry the derived stable ID (insert-by-ID catches them);
  the content key remains for echo--prefixed archive rows + self echoes.
- Tests: old-parser semantics on the new tag (m[1] per-message-unique
  and equal to the derived ID) and a forged-m[1] event that cannot
  pre-poison a genuine message's dedup slot.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

bitchat/Nostr/NostrProtocol.swift

@@ -264,22 +264,33 @@ struct NostrProtocol {
 
     /// Create a mesh-bridge public message (kind 20000) for a geohash-cell
     /// rendezvous. The distinct `r` tag keeps bridge traffic out of geohash
-    /// channel subscriptions (which filter on `#g`); `m` carries the original
+    /// channel subscriptions (which filter on `#g`); `m` is
-    /// mesh message ID so receivers dedup the bridged copy against the radio
+    /// `[stable ID, mesh sender ID, wire timestamp in ms]`. Element 1 is the
-    /// copy by timeline ID.
+    /// content-stable mesh message ID (`MeshMessageIdentity`) for v1.7.0
+    /// parsers, which key their dedup on `m[1]` unconditionally and need it
+    /// per-message-unique; current parsers ignore it and recompute the ID
+    /// from the origin coordinates (elements 2-3) plus the event's own
+    /// content to dedup the bridged copy against the radio copy by
+    /// timeline ID.
     static func createBridgeMeshEvent(
         content: String,
         cell: String,
         senderIdentity: NostrIdentity,
         nickname: String? = nil,
-        meshMessageID: String? = nil
+        meshSenderID: String? = nil,
+        meshTimestampMs: UInt64? = nil
     ) throws -> NostrEvent {
         var tags = [["r", cell]]
         if let nickname = nickname?.trimmedOrNilIfEmpty {
             tags.append(["n", nickname])
         }
-        if let meshMessageID = meshMessageID?.trimmedOrNilIfEmpty {
+        if let meshSenderID = meshSenderID?.trimmedOrNilIfEmpty, let meshTimestampMs {
-            tags.append(["m", meshMessageID])
+            let stableID = MeshMessageIdentity.stableID(
+                senderIDHex: meshSenderID,
+                timestampMs: meshTimestampMs,
+                content: content
+            )
+            tags.append(["m", stableID, meshSenderID, String(meshTimestampMs)])
         }
         let event = NostrEvent(
             pubkey: senderIdentity.publicKeyHex,

bitchat/Protocols/MeshMessageIdentity.swift

@@ -0,0 +1,35 @@
+//
+// MeshMessageIdentity.swift
+// bitchat
+//
+// This is free and unencumbered software released into the public domain.
+// For more information, see <https://unlicense.org>
+//
+
+import BitFoundation
+import Foundation
+
+/// Content-derived identity for public mesh messages.
+///
+/// The BLE wire carries no message ID for public broadcasts, so every device
+/// recomputes the same stable ID from the signed wire fields (sender ID,
+/// millisecond timestamp, content). That gives the mesh bridge a
+/// cross-device-consistent dedup/attribution key with zero wire change — and
+/// because receivers derive the key themselves instead of trusting a claimed
+/// ID, forging a bridge tag that binds a chosen ID to *different* content is
+/// infeasible. The inputs are cleartext on the radio, though: an attacker in
+/// radio range can re-sign the identical sender/timestamp/content under
+/// their own Nostr key and win first-wins injection on remote islands —
+/// duplicate-content spoofing the unbridged mesh already permits, so no
+/// worse than before.
+enum MeshMessageIdentity {
+    /// Matches the wire truncation in `BLEService.sendMessage`.
+    static func millisecondTimestamp(_ date: Date) -> UInt64 {
+        UInt64(date.timeIntervalSince1970 * 1000)
+    }
+
+    static func stableID(senderIDHex: String, timestampMs: UInt64, content: String) -> String {
+        let input = senderIDHex.lowercased() + "|" + String(timestampMs) + "|" + content.trimmed
+        return String(Data(input.utf8).sha256Hex().prefix(32))
+    }
+}

bitchat/Services/BLE/BLEPublicMessageHandler.swift

@@ -122,10 +122,18 @@ final class BLEPublicMessageHandler {
         SecureLogger.debug("💬 [\(senderNickname)] TTL:\(packet.ttl) (\(pathTag)) chars=\(content.count) bytes=\(packet.payload.count)", category: .session)
 
         let ts = Date(timeIntervalSince1970: Double(packet.timestamp) / 1000)
-        var resolvedSelfMessageID: String? = nil
+        let messageID: String?
         if peerID == env.localPeerID() {
-            resolvedSelfMessageID = env.takeSelfBroadcastMessageID(packet)
+            messageID = env.takeSelfBroadcastMessageID(packet)
+        } else {
+            // The wire carries no message ID; derive the stable one every
+            // device agrees on so bridged copies dedup against the radio copy.
+            messageID = MeshMessageIdentity.stableID(
+                senderIDHex: peerID.id,
+                timestampMs: packet.timestamp,
+                content: content
+            )
         }
-        env.deliverPublicMessage(peerID, senderNickname, content, ts, resolvedSelfMessageID)
+        env.deliverPublicMessage(peerID, senderNickname, content, ts, messageID)
     }
 }

bitchat/Services/Gateway/BridgeService.swift

@@ -47,9 +47,11 @@ import Foundation
 ///    already holds the radio copy (`isMessageSeenLocally` on the event's
 ///    mesh message ID) — remote islands' traffic is the only thing worth
 ///    airtime.
-/// Receivers additionally dedup by timeline message ID: a bridged copy
+/// Receivers additionally dedup by timeline message ID: the wire carries no
-/// carries the original mesh message ID in its `m` tag, so the store's
+/// public message ID, so every device derives the same content-stable one
-/// insert-by-ID absorbs radio/bridge duplicates in either arrival order.
+/// (`MeshMessageIdentity`) from the origin coordinates in the event's `m`
+/// tag — recomputed locally, never trusted — and the store's insert-by-ID
+/// absorbs radio/bridge duplicates in either arrival order.
 ///
 /// All dependencies are closure-injected (repo convention) so the policy
 /// layer is unit-testable without relays, radios, or CoreLocation.
@@ -292,22 +294,32 @@ final class BridgeService: ObservableObject {
     /// Composes and ships the bridged copy of an outgoing public mesh
     /// message. Call after the radio send; no-op when the bridge is off,
     /// no cell is known, or the message was flagged nearby-only upstream.
-    func bridgeOutgoing(content: String, messageID: String) {
+    /// `senderPeerID`/`timestamp` are the origin coordinates of the radio
+    /// send — they (with the content) derive the cross-device-stable mesh
+    /// message ID that receivers dedup on.
+    func bridgeOutgoing(content: String, senderPeerID: PeerID, timestamp: Date) {
         guard isEnabled, !nearbyOnly, let cell = activeCell ?? currentCell() else { return }
         guard content.utf8.count <= Limits.maxContentBytes else { return }
+        let timestampMs = MeshMessageIdentity.millisecondTimestamp(timestamp)
+        let stableID = MeshMessageIdentity.stableID(
+            senderIDHex: senderPeerID.id,
+            timestampMs: timestampMs,
+            content: content
+        )
         guard let identity = try? deriveIdentity?(cell),
               let event = try? NostrProtocol.createBridgeMeshEvent(
                 content: content,
                 cell: cell,
                 senderIdentity: identity,
                 nickname: myNickname?(),
-                meshMessageID: messageID
+                meshSenderID: senderPeerID.id,
+                meshTimestampMs: timestampMs
               ) else {
             SecureLogger.error("🌉 Bridge: failed to compose rendezvous event", category: .session)
             return
         }
         publishedEventIDs.insert(event.id)
-        injectedMessageIDs.insert(messageID) // our own timeline already has it
+        injectedMessageIDs.insert(stableID) // our own timeline already has it
         if relaysConnected?() ?? false {
             publishToRelays?(event, cell)
         } else if let carrier = NostrCarrierPacket(direction: .toBridge, geohash: cell, event: event),
@@ -648,8 +660,25 @@ final class BridgeService: ObservableObject {
             let content = event.content
             guard !content.trimmed.isEmpty, content.utf8.count <= Limits.maxContentBytes else { return nil }
             let nickname = event.tags.first(where: { $0.count >= 2 && $0[0] == "n" })?[1]
-            let meshID = event.tags.first(where: { $0.count >= 2 && $0[0] == "m" })?[1]
+            // Recompute — never trust — the mesh message ID: the `m` tag is
-            let messageID = (meshID?.trimmedOrNilIfEmpty) ?? event.id
+            // `[stable ID, sender ID, wire timestamp ms]`. Element 1 exists
+            // for v1.7.0 parsers; we ignore it and derive the ID from the
+            // origin coordinates (elements 2-3) plus the event's own content,
+            // so a forged tag cannot bind a chosen ID to different content
+            // (see `MeshMessageIdentity` for the exact property and its
+            // limits).
+            let m = event.tags.first(where: { $0.count >= 2 && $0[0] == "m" })
+            let messageID: String
+            if let m, m.count >= 4, m[2].count == 16, m[2].allSatisfy(\.isHexDigit),
+               let timestampMs = UInt64(m[3]) {
+                messageID = MeshMessageIdentity.stableID(
+                    senderIDHex: m[2],
+                    timestampMs: timestampMs,
+                    content: content
+                )
+            } else {
+                messageID = event.id // old-format or absent tag
+            }
             return .message(InboundBridgeMessage(
                 messageID: messageID,
                 senderNickname: nickname?.trimmedOrNilIfEmpty ?? "anon#\(event.pubkey.suffix(4))",

bitchat/ViewModels/ChatOutgoingCoordinator.swift

@@ -44,7 +44,10 @@ protocol ChatOutgoingContext: AnyObject {
     func sendGeohash(context: ChatViewModel.GeoOutgoingContext)
     /// Ships the bridged (rendezvous) copy of a just-sent public mesh
     /// message; no-op when the bridge is off or the send is nearby-only.
-    func bridgeOutgoingPublicMessage(_ content: String, messageID: String)
+    /// Takes the origin coordinates (sender + wire timestamp) — the bridge
+    /// derives the cross-device-stable mesh message ID from them, not from
+    /// our local timeline UUID (which no other device can recompute).
+    func bridgeOutgoingPublicMessage(_ content: String, senderPeerID: PeerID, timestamp: Date)
 
     // MARK: Geohash identity (shared with the other contexts)
     func deriveNostrIdentity(forGeohash geohash: String) throws -> NostrIdentity
@@ -66,8 +69,8 @@ extension ChatViewModel: ChatOutgoingContext {
         lastPublicActivityAt[key] = Date()
     }
 
-    func bridgeOutgoingPublicMessage(_ content: String, messageID: String) {
+    func bridgeOutgoingPublicMessage(_ content: String, senderPeerID: PeerID, timestamp: Date) {
-        BridgeService.shared.bridgeOutgoing(content: content, messageID: messageID)
+        BridgeService.shared.bridgeOutgoing(content: content, senderPeerID: senderPeerID, timestamp: timestamp)
     }
 }
 
@@ -147,7 +150,7 @@ private extension ChatOutgoingCoordinator {
             messageID: message.id,
             timestamp: message.timestamp
         )
-        context.bridgeOutgoingPublicMessage(trimmed, messageID: message.id)
+        context.bridgeOutgoingPublicMessage(trimmed, senderPeerID: context.myPeerID, timestamp: message.timestamp)
     }
 
     /// Geohash sends mine a NIP-13 nonce tag first (off the main actor, see

bitchat/ViewModels/ChatPublicConversationCoordinator.swift

@@ -417,9 +417,12 @@ final class ChatPublicConversationCoordinator: PublicMessagePipelineDelegate {
     ///   rate limit; low/no-PoW events keep the strict limits so old clients
     ///   still get through at normal rates.
     /// Identity keys of the archived echoes seeded into the mesh timeline at
-    /// launch. The mesh wire format carries no stable message ID, so a
+    /// launch. Re-synced copies of others' messages now arrive with the same
-    /// re-synced copy of an already-rendered echo arrives with a fresh UUID —
+    /// derived stable ID (`MeshMessageIdentity`), so the store's insert-by-ID
-    /// this content identity is the only way to recognize it.
+    /// catches those — but the archive-restored rows themselves carry
+    /// `echo-`-prefixed IDs, and self echoes get fresh UUIDs, so this content
+    /// identity remains the way to recognize a live copy of an
+    /// already-rendered echo.
     private var archivedEchoKeys = Set<String>()
 
     func registerArchivedEcho(senderPeerID: PeerID?, timestamp: Date, content: String) {

bitchatTests/ChatOutgoingCoordinatorContextTests.swift

@@ -87,9 +87,9 @@ private final class MockChatOutgoingContext: ChatOutgoingContext {
         sentGeohashContexts.append(context)
     }
 
-    private(set) var bridgedMessages: [(content: String, messageID: String)] = []
+    private(set) var bridgedMessages: [(content: String, senderPeerID: PeerID, timestamp: Date)] = []
-    func bridgeOutgoingPublicMessage(_ content: String, messageID: String) {
+    func bridgeOutgoingPublicMessage(_ content: String, senderPeerID: PeerID, timestamp: Date) {
-        bridgedMessages.append((content, messageID))
+        bridgedMessages.append((content, senderPeerID, timestamp))
     }
 
     // Geohash identity

bitchatTests/Protocols/BridgeWireFormatTests.swift

@@ -111,6 +111,53 @@ struct BridgeWireFormatTests {
     }
 }
 
+@Suite("Mesh message identity")
+struct MeshMessageIdentityTests {
+    @Test func stableIDIsDeterministicHex() {
+        let id = MeshMessageIdentity.stableID(
+            senderIDHex: "0011223344556677",
+            timestampMs: 1_750_000_000_123,
+            content: "hello mesh"
+        )
+        // Pinned vector: first 32 hex chars of
+        // SHA256("0011223344556677|1750000000123|hello mesh"). Any drift
+        // breaks cross-device (and cross-version) dedup.
+        #expect(id == "b83f94d81dcdd1b0c0048f6645995dd4")
+        #expect(id == MeshMessageIdentity.stableID(
+            senderIDHex: "0011223344556677",
+            timestampMs: 1_750_000_000_123,
+            content: "hello mesh"
+        ))
+    }
+
+    @Test func senderIDIsCaseInsensitive() {
+        let lower = MeshMessageIdentity.stableID(senderIDHex: "aabbccdd00112233", timestampMs: 1, content: "x")
+        let upper = MeshMessageIdentity.stableID(senderIDHex: "AABBCCDD00112233", timestampMs: 1, content: "x")
+        #expect(lower == upper)
+    }
+
+    @Test func contentWhitespaceIsNormalized() {
+        // Senders bridge the trimmed content while the radio carries the
+        // original; both must derive the same key.
+        let raw = MeshMessageIdentity.stableID(senderIDHex: "aabbccdd00112233", timestampMs: 1, content: "  hello mesh \n")
+        let trimmed = MeshMessageIdentity.stableID(senderIDHex: "aabbccdd00112233", timestampMs: 1, content: "hello mesh")
+        #expect(raw == trimmed)
+    }
+
+    @Test func anyCoordinateChangeChangesTheID() {
+        let base = MeshMessageIdentity.stableID(senderIDHex: "aabbccdd00112233", timestampMs: 5, content: "x")
+        #expect(base != MeshMessageIdentity.stableID(senderIDHex: "aabbccdd00112234", timestampMs: 5, content: "x"))
+        #expect(base != MeshMessageIdentity.stableID(senderIDHex: "aabbccdd00112233", timestampMs: 6, content: "x"))
+        #expect(base != MeshMessageIdentity.stableID(senderIDHex: "aabbccdd00112233", timestampMs: 5, content: "y"))
+    }
+
+    @Test func millisecondTimestampTruncatesLikeTheWire() {
+        // Must match `BLEService.sendMessage`'s UInt64(seconds * 1000).
+        #expect(MeshMessageIdentity.millisecondTimestamp(Date(timeIntervalSince1970: 1_000.9996)) == 1_000_999)
+        #expect(MeshMessageIdentity.millisecondTimestamp(Date(timeIntervalSince1970: 1_000)) == 1_000_000)
+    }
+}
+
 @Suite("Courier store bridge publish")
 struct CourierStoreBridgePublishTests {
     private func makeStore(now: @escaping () -> Date = Date.init) -> CourierStore {

bitchatTests/Services/BLEPublicMessageHandlerTests.swift

@@ -83,7 +83,13 @@ struct BLEPublicMessageHandlerTests {
         #expect(recorder.deliveries.first?.nickname == "Alice")
         #expect(recorder.deliveries.first?.content == "hello mesh")
         #expect(recorder.deliveries.first?.timestamp == now)
-        #expect(recorder.deliveries.first?.messageID == nil)
+        // No message ID on the wire: the handler derives the stable one
+        // every device agrees on for the same sender/timestamp/content.
+        #expect(recorder.deliveries.first?.messageID == MeshMessageIdentity.stableID(
+            senderIDHex: remotePeerID.id,
+            timestampMs: timestamp(now),
+            content: "hello mesh"
+        ))
     }
 
     @Test

bitchatTests/Services/BridgeServiceTests.swift

@@ -117,21 +117,35 @@ struct BridgeServiceTests {
 
     // MARK: Event helpers
 
+    private static let remoteMeshSenderID = "feedfacecafef00d"
+    private static let remoteMeshTimestampMs: UInt64 = 1_750_000_000_000
+
     private func makeRemoteEvent(
         cell: String = BridgeServiceTests.cell,
         content: String = "hi \(UUID().uuidString.prefix(8))",
-        meshMessageID: String? = UUID().uuidString
+        meshSenderID: String = BridgeServiceTests.remoteMeshSenderID,
+        meshTimestampMs: UInt64 = BridgeServiceTests.remoteMeshTimestampMs,
+        identity: NostrIdentity? = nil
     ) throws -> NostrEvent {
-        let identity = try NostrIdentity.generate()
+        try NostrProtocol.createBridgeMeshEvent(
-        return try NostrProtocol.createBridgeMeshEvent(
             content: content,
             cell: cell,
-            senderIdentity: identity,
+            senderIdentity: identity ?? NostrIdentity.generate(),
             nickname: "remote",
-            meshMessageID: meshMessageID
+            meshSenderID: meshSenderID,
+            meshTimestampMs: meshTimestampMs
         )
     }
 
+    /// The dedup key receivers derive for an event built by `makeRemoteEvent`.
+    private func stableID(
+        content: String,
+        meshSenderID: String = BridgeServiceTests.remoteMeshSenderID,
+        meshTimestampMs: UInt64 = BridgeServiceTests.remoteMeshTimestampMs
+    ) -> String {
+        MeshMessageIdentity.stableID(senderIDHex: meshSenderID, timestampMs: meshTimestampMs, content: content)
+    }
+
     private func makePresenceEvent(cell: String = BridgeServiceTests.cell) throws -> NostrEvent {
         try NostrProtocol.createBridgePresenceEvent(cell: cell, senderIdentity: NostrIdentity.generate())
     }
@@ -201,28 +215,64 @@ struct BridgeServiceTests {
 
     // MARK: - Outgoing
 
-    @Test func outgoingPublishesSignedRendezvousEventWithMeshMessageID() throws {
+    @Test func outgoingPublishesSignedRendezvousEventWithOriginCoordinates() throws {
         let fixture = Fixture(enabled: true)
         fixture.service.refreshRendezvous()
-        let messageID = UUID().uuidString
+        let sender = PeerID(str: "0011223344556677")
+        let timestamp = Date()
 
-        fixture.service.bridgeOutgoing(content: "hello hill", messageID: messageID)
+        fixture.service.bridgeOutgoing(content: "hello hill", senderPeerID: sender, timestamp: timestamp)
 
         let published = try #require(fixture.published.last)
         #expect(published.cell == Self.cell)
         #expect(published.event.isValidSignature())
         #expect(published.event.content == "hello hill")
         #expect(published.event.tags.contains(["r", Self.cell]))
-        #expect(published.event.tags.contains(["m", messageID]))
+        let timestampMs = MeshMessageIdentity.millisecondTimestamp(timestamp)
+        #expect(published.event.tags.contains([
+            "m",
+            MeshMessageIdentity.stableID(senderIDHex: sender.id, timestampMs: timestampMs, content: "hello hill"),
+            sender.id,
+            String(timestampMs),
+        ]))
         #expect(published.event.tags.contains(["n", "tester"]))
     }
 
+    @Test func newMeshTagStaysPerMessageUniqueForOldParsers() throws {
+        // v1.7.0 parsers take m[1] unconditionally as the dedup key whenever
+        // the tag has >= 2 elements. A constant m[1] (e.g. the bare sender
+        // ID) would make old receivers inject-dedup away every message from
+        // a sender after their first — so element 1 must be the
+        // per-message-unique stable ID itself.
+        let fixture = Fixture(enabled: true)
+        fixture.service.refreshRendezvous()
+        let sender = PeerID(str: "0011223344556677")
+        let timestamp = Date()
+
+        fixture.service.bridgeOutgoing(content: "first", senderPeerID: sender, timestamp: timestamp)
+        fixture.service.bridgeOutgoing(content: "second", senderPeerID: sender, timestamp: timestamp)
+
+        // Old-parser extraction: m[1] of the first `m` tag with >= 2 elements.
+        let oldParserKeys = fixture.publishedMessages.compactMap {
+            $0.event.tags.first(where: { $0.count >= 2 && $0[0] == "m" })?[1]
+        }
+        #expect(oldParserKeys.count == 2)
+        #expect(oldParserKeys[0] != oldParserKeys[1])
+        // And old and new receivers key the same message identically: m[1]
+        // equals the ID the new parser recomputes from elements 2-3.
+        let timestampMs = MeshMessageIdentity.millisecondTimestamp(timestamp)
+        #expect(oldParserKeys == [
+            MeshMessageIdentity.stableID(senderIDHex: sender.id, timestampMs: timestampMs, content: "first"),
+            MeshMessageIdentity.stableID(senderIDHex: sender.id, timestampMs: timestampMs, content: "second"),
+        ])
+    }
+
     @Test func nearbyOnlySuppressesTheBridgedCopy() {
         let fixture = Fixture(enabled: true)
         fixture.service.refreshRendezvous()
         fixture.service.nearbyOnly = true
 
-        fixture.service.bridgeOutgoing(content: "just us", messageID: UUID().uuidString)
+        fixture.service.bridgeOutgoing(content: "just us", senderPeerID: PeerID(str: "0011223344556677"), timestamp: Date())
 
         #expect(fixture.publishedMessages.isEmpty)
         #expect(fixture.uplinkSends.isEmpty)
@@ -234,7 +284,7 @@ struct BridgeServiceTests {
         fixture.relaysConnected = false
         fixture.bridgePeers = [PeerID(str: "abcdef0123456789")]
 
-        fixture.service.bridgeOutgoing(content: "no internet here", messageID: UUID().uuidString)
+        fixture.service.bridgeOutgoing(content: "no internet here", senderPeerID: PeerID(str: "0011223344556677"), timestamp: Date())
 
         #expect(fixture.publishedMessages.isEmpty)
         let sent = try #require(fixture.uplinkSends.first)
@@ -255,7 +305,8 @@ struct BridgeServiceTests {
             cell: Self.cell,
             senderIdentity: fixture.identity, // == deriveIdentity(cell)
             nickname: "tester",
-            meshMessageID: UUID().uuidString
+            meshSenderID: "0011223344556677",
+            meshTimestampMs: Self.remoteMeshTimestampMs
         )
 
         fixture.service.handleRendezvousEvent(ownOldEvent)
@@ -268,7 +319,7 @@ struct BridgeServiceTests {
     @Test func ownEventComingBackFromSubscriptionIsIgnored() {
         let fixture = Fixture(enabled: true)
         fixture.service.refreshRendezvous()
-        fixture.service.bridgeOutgoing(content: "echo me", messageID: UUID().uuidString)
+        fixture.service.bridgeOutgoing(content: "echo me", senderPeerID: PeerID(str: "0011223344556677"), timestamp: Date())
         let ownEvent = fixture.published[0].event
 
         fixture.service.handleRendezvousEvent(ownEvent)
@@ -343,9 +394,10 @@ struct BridgeServiceTests {
     @Test func locallySeenMessageIsNeitherInjectedNorDownlinked() throws {
         let fixture = Fixture(enabled: true)
         fixture.service.refreshRendezvous()
-        let messageID = UUID().uuidString
+        let content = "heard on the radio"
-        fixture.locallySeenMessageIDs = [messageID]
+        // The radio copy's timeline row keys on the same derived stable ID.
-        let event = try makeRemoteEvent(meshMessageID: messageID)
+        fixture.locallySeenMessageIDs = [stableID(content: content)]
+        let event = try makeRemoteEvent(content: content)
 
         fixture.service.handleRendezvousEvent(event)
 
@@ -357,6 +409,96 @@ struct BridgeServiceTests {
         #expect(fixture.service.bridgedPeerCount == 0)
     }
 
+    @Test func radioConfirmedSenderStaysLocalForLaterEvents() throws {
+        // Sticky local attribution keyed on the derived stable ID: one
+        // radio-confirmed message marks the pubkey as an islander, so their
+        // later events never inflate the bridged count.
+        let fixture = Fixture(enabled: true)
+        fixture.service.refreshRendezvous()
+        let identity = try NostrIdentity.generate()
+        let content = "island echo"
+        fixture.locallySeenMessageIDs = [stableID(content: content)]
+
+        fixture.service.handleRendezvousEvent(try makeRemoteEvent(content: content, identity: identity))
+        #expect(fixture.service.bridgedPeerCount == 0)
+
+        fixture.service.handleRendezvousEvent(try makeRemoteEvent(
+            content: "not on the radio yet",
+            meshTimestampMs: Self.remoteMeshTimestampMs + 1,
+            identity: identity
+        ))
+        #expect(fixture.service.bridgedPeerCount == 0)
+    }
+
+    @Test func spoofedOriginCoordinatesCannotSuppressTheGenuineMessage() throws {
+        // Attack: sign an event claiming a victim's origin coordinates in the
+        // `m` tag to pre-poison the dedup key. The key is recomputed from the
+        // event's own content, so the spoof lands under a different ID and the
+        // genuine message still renders.
+        let fixture = Fixture(enabled: true)
+        fixture.service.refreshRendezvous()
+        let spoof = try makeRemoteEvent(content: "impostor payload")
+        let genuine = try makeRemoteEvent(content: "the real message")
+
+        fixture.service.handleRendezvousEvent(spoof)
+        fixture.service.handleRendezvousEvent(genuine)
+
+        #expect(fixture.injected.count == 2)
+        #expect(fixture.injected.map(\.messageID) == [
+            stableID(content: "impostor payload"),
+            stableID(content: "the real message"),
+        ])
+    }
+
+    @Test func forgedStableIDElementIsNeverTrusted() throws {
+        // Element 1 of the `m` tag exists only for old parsers. An event
+        // claiming the genuine message's stable ID there — over different
+        // content — must still key on its own derived ID, so it cannot
+        // pre-poison the genuine message's dedup slot.
+        let fixture = Fixture(enabled: true)
+        fixture.service.refreshRendezvous()
+        let genuineID = stableID(content: "the real message")
+        let identity = try NostrIdentity.generate()
+        let forged = try NostrEvent(
+            pubkey: identity.publicKeyHex,
+            createdAt: Date(),
+            kind: .ephemeralEvent,
+            tags: [
+                ["r", Self.cell],
+                ["m", genuineID, Self.remoteMeshSenderID, String(Self.remoteMeshTimestampMs)],
+            ],
+            content: "impostor payload"
+        ).sign(with: identity.schnorrSigningKey())
+        let genuine = try makeRemoteEvent(content: "the real message")
+
+        fixture.service.handleRendezvousEvent(forged)
+        fixture.service.handleRendezvousEvent(genuine)
+
+        #expect(fixture.injected.map(\.messageID) == [
+            stableID(content: "impostor payload"),
+            genuineID,
+        ])
+    }
+
+    @Test func oldFormatMeshTagFallsBackToEventID() throws {
+        // A 2-element `m` tag from an old sender carries an ID no other
+        // device can recompute; the event ID keeps today's behavior.
+        let fixture = Fixture(enabled: true)
+        fixture.service.refreshRendezvous()
+        let identity = try NostrIdentity.generate()
+        let legacy = try NostrEvent(
+            pubkey: identity.publicKeyHex,
+            createdAt: Date(),
+            kind: .ephemeralEvent,
+            tags: [["r", Self.cell], ["m", UUID().uuidString]],
+            content: "legacy copy"
+        ).sign(with: identity.schnorrSigningKey())
+
+        fixture.service.handleRendezvousEvent(legacy)
+
+        #expect(fixture.injected.map(\.messageID) == [legacy.id])
+    }
+
     @Test func duplicateSubscriptionEventInjectsOnce() throws {
         let fixture = Fixture(enabled: true)
         fixture.service.refreshRendezvous()