diff --git a/frontend/src/components/MessageList.tsx b/frontend/src/components/MessageList.tsx
index 898dae4..7e80290 100644
--- a/frontend/src/components/MessageList.tsx
+++ b/frontend/src/components/MessageList.tsx
@@ -314,7 +314,7 @@ export function MessageList({
   // Note: Deduplication is handled by useConversationMessages.addMessageIfNew()
   // and the database UNIQUE constraint on (type, conversation_key, text, sender_timestamp)
   const sortedMessages = useMemo(
-    () => [...messages].sort((a, b) => a.received_at - b.received_at),
+    () => [...messages].sort((a, b) => a.received_at - b.received_at || a.id - b.id),
     [messages]
   );