From 249268dd00f90d23c791251076574ab532f599de Mon Sep 17 00:00:00 2001
From: Janez T <hey@dz0ny.dev>
Date: Fri, 13 Mar 2026 19:39:03 +0100
Subject: [PATCH] Prevent duplicate channel messages

---
 lib/providers/messages_provider.dart          | 30 +++++++++++--------
 ...messages_provider_retransmission_test.dart | 28 +++++++++++++----
 2 files changed, 40 insertions(+), 18 deletions(-)

diff --git a/lib/providers/messages_provider.dart b/lib/providers/messages_provider.dart
index 2056810..cec1852 100644
--- a/lib/providers/messages_provider.dart
+++ b/lib/providers/messages_provider.dart
@@ -646,11 +646,18 @@ class MessagesProvider with ChangeNotifier {
       if (existing.channelIdx != message.channelIdx) {
         return false;
       }
+
+      final timestampDeltaSeconds = (existing.senderTimestamp -
+              message.senderTimestamp)
+          .abs();
+      final withinChannelRepeatWindow = timestampDeltaSeconds <= 5;
+
       final existingSenderKey = existing.senderKeyShort;
       final incomingSenderKey = message.senderKeyShort;
       if (existingSenderKey != null &&
           incomingSenderKey != null &&
-          existingSenderKey == incomingSenderKey) {
+          existingSenderKey == incomingSenderKey &&
+          withinChannelRepeatWindow) {
         return true;
       }
 
@@ -663,23 +670,20 @@ class MessagesProvider with ChangeNotifier {
           return true;
         }
 
-        // When we send to a channel we add a local "sent" bubble immediately,
-        // then firmware may later sync back the same message as a received
-        // channel item under our public handle. Only fold that replay into the
-        // original bubble after LOG_RX_DATA has already confirmed it as our
-        // transmitted packet.
+        if (!withinChannelRepeatWindow) {
+          return false;
+        }
+
+        // Mirror meshcore-open behavior for self-authored channel messages:
+        // zero-hop self replays are dropped earlier in AppProvider, while
+        // routed self replays should fold into the local sent bubble when the
+        // public sender name matches within a short window.
         if (existing.isSentMessage &&
-            existing.echoCount > 0 &&
             !message.isSentMessage &&
-            (existing.senderTimestamp - message.senderTimestamp).abs() <= 1) {
+            existingSenderName == incomingSenderName) {
           return true;
         }
-      }
 
-      if (existing.isSentMessage &&
-          existing.echoCount > 0 &&
-          !message.isSentMessage &&
-          existing.senderTimestamp == message.senderTimestamp) {
         return true;
       }
 
diff --git a/test/providers/messages_provider_retransmission_test.dart b/test/providers/messages_provider_retransmission_test.dart
index f73dd34..5897038 100644
--- a/test/providers/messages_provider_retransmission_test.dart
+++ b/test/providers/messages_provider_retransmission_test.dart
@@ -177,7 +177,7 @@ void main() {
     });
 
     test(
-      'channel replay is deduped after raw echo detection confirms our send',
+      'channel replay is deduped for self sender within repeat window',
       () {
         final provider = MessagesProvider();
         provider.resolveContactNameCallback = (_) => 'dz0ny (SI)';
@@ -185,12 +185,11 @@ void main() {
           _buildSentChannelMessage(id: 'c-echo', senderTimestamp: 1700000100),
         );
         provider.markMessageSent('c-echo', 0, 0);
-        provider.handleMessageEcho('c-echo', 1, 12, -90);
 
         provider.addMessage(
           _buildReceivedChannelReplay(
             id: 'c-echo-incoming',
-            senderTimestamp: 1700000101,
+            senderTimestamp: 1700000104,
             senderName: 'dz0ny (SI)',
           ),
         );
@@ -202,7 +201,7 @@ void main() {
     );
 
     test(
-      'channel replay is not deduped before raw echo detection confirms it',
+      'channel replay is not deduped for different sender with same text',
       () {
         final provider = MessagesProvider();
         provider.resolveContactNameCallback = (_) => 'dz0ny (SI)';
@@ -218,7 +217,7 @@ void main() {
           _buildReceivedChannelReplay(
             id: 'c-no-echo-incoming',
             senderTimestamp: 1700000201,
-            senderName: 'dz0ny (SI)',
+            senderName: 'Radio Alpha',
           ),
         );
 
@@ -226,6 +225,25 @@ void main() {
       },
     );
 
+    test('channel replay is not deduped outside repeat window', () {
+      final provider = MessagesProvider();
+      provider.resolveContactNameCallback = (_) => 'dz0ny (SI)';
+      provider.addSentMessage(
+        _buildSentChannelMessage(id: 'c-late', senderTimestamp: 1700000300),
+      );
+      provider.markMessageSent('c-late', 0, 0);
+
+      provider.addMessage(
+        _buildReceivedChannelReplay(
+          id: 'c-late-incoming',
+          senderTimestamp: 1700000306,
+          senderName: 'dz0ny (SI)',
+        ),
+      );
+
+      expect(provider.messages, hasLength(2));
+    });
+
     test('missing ACK schedules a delayed retransmission', () {
       fakeAsync((async) {
         final provider = MessagesProvider();