From 523cb0c4b369b19f8bf4cf74a75049a1f2f112e4 Mon Sep 17 00:00:00 2001
From: Jannis Braun <151788261+TheZwiss@users.noreply.github.com>
Date: Thu, 26 Mar 2026 17:55:58 +0100
Subject: [PATCH] fix(federation): deduplicate relay DM messages in chatStore

When a user has federated WS connections, they can receive both the
original message (from their home instance) and the relay copy (from the
remote instance). The relay copy has a different message ID but carries
sourceMessageId pointing to the original. The dedup now checks both
directions: incoming relay copy vs existing original, and incoming
original vs existing relay copy.
---
 packages/web/src/stores/chatStore.ts | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/packages/web/src/stores/chatStore.ts b/packages/web/src/stores/chatStore.ts
index d3e90486..deead698 100644
--- a/packages/web/src/stores/chatStore.ts
+++ b/packages/web/src/stores/chatStore.ts
@@ -392,6 +392,13 @@ export const useChatStore = create<ChatState>((set, get) => ({
       const current = newMessages.get(channelId) ?? [];
       // Avoid duplicates
       if (current.find(m => m.id === normalizedMessage.id)) return state;
+      // Federation relay dedup: skip if this is a relay copy of a message we
+      // already have (sourceMessageId matches an existing ID), or if we already
+      // have the relay copy and the original is now arriving (existing
+      // sourceMessageId matches incoming ID).
+      if ('sourceMessageId' in normalizedMessage && normalizedMessage.sourceMessageId
+        && current.find(m => m.id === normalizedMessage.sourceMessageId)) return state;
+      if (current.find(m => 'sourceMessageId' in m && m.sourceMessageId === normalizedMessage.id)) return state;
       // Remove any optimistic temp message with same content (no userId check —
       // federated messages arrive with a different replicated user ID).
       // Normalize both sides: empty string and null are equivalent (server stores null for empty content).