diff --git a/src/components/MessageList.tsx b/src/components/MessageList.tsx
index 896d65e..d75e443 100644
--- a/src/components/MessageList.tsx
+++ b/src/components/MessageList.tsx
@@ -32,7 +32,7 @@ export default function MessageList({ conversationId, refreshKey }: Props) {
     load();
     // ponytail: polling every 3s — replace with WebSocket when server supports it
     const id = setInterval(load, 3000);
-    return () => { cancelled = true; clearInterval(id); };
+    return () => { cancelled = true; clearInterval(id); prevLengthRef.current = 0; };
   // Fix 2: refreshKey in deps triggers immediate reload after send
   }, [conversationId, refreshKey]);