diff --git a/static/js/conversations.js b/static/js/conversations.js
index 5b539cd..445a114 100644
--- a/static/js/conversations.js
+++ b/static/js/conversations.js
@@ -775,17 +775,19 @@
             var convId = msg.conversation_id;
             if (!state.messages[convId]) state.messages[convId] = [];
 
-            // Dedup: skip if message with this ID already exists
-            // Dedup: by real ID or by matching optimistic message (same sender + content)
+            // Dedup: skip if message already exists by ID, content match, or time proximity
             var dominated = state.messages[convId].some(function(m) {
                 if (m.id === msg.id) return true;
-                // Match optimistic msg: same sender, same stripped content
-                if (m._optimistic && msg.sender_id && m.sender_id === msg.sender_id) {
+                // Match by same sender + same stripped content (optimistic or SSE/poll race)
+                if (msg.sender_id && m.sender_id === msg.sender_id) {
                     var mc = (m.content || '').replace(/<[^>]*>/g, '').trim();
                     var nc = (msg.content || '').replace(/<[^>]*>/g, '').trim();
                     if (mc && nc && mc === nc) {
-                        m.id = msg.id; // Update to real ID
-                        m._optimistic = false;
+                        // Update to real ID if this was optimistic
+                        if (m._optimistic) {
+                            m.id = msg.id;
+                            m._optimistic = false;
+                        }
                         return true;
                     }
                 }