diff --git a/frontend/src/ws/useChatSocket.ts b/frontend/src/ws/useChatSocket.ts
index 8afa0d7..4a960d0 100644
--- a/frontend/src/ws/useChatSocket.ts
+++ b/frontend/src/ws/useChatSocket.ts
@@ -29,16 +29,30 @@ export function useChatSocket({ roomId, onMessage, onUnauthenticated }: UseChatS
       socketRef.current = ws
 
       ws.onopen = () => {
+        // Guards against React StrictMode's dev-only double-invoke of this
+        // effect (mount -> cleanup -> mount again): the first socket gets
+        // abandoned in cleanup, but its own open/close events can still
+        // fire asynchronously afterward. Without this check, a stale
+        // socket's callbacks can stomp on state that the second (real)
+        // socket already owns.
+        if (socketRef.current !== ws) return
         reconnectDelay = RECONNECT_BASE_DELAY_MS
         setConnected(true)
         ws.send(JSON.stringify({ type: 'join', room_id: roomId }))
       }
 
       ws.onmessage = (event) => {
+        if (socketRef.current !== ws) return
         onMessageRef.current(JSON.parse(event.data) as ServerEnvelope)
       }
 
       ws.onclose = (event) => {
+        // Same guard as onopen -- a stale/abandoned socket's close event
+        // must not null out the reference to whatever socket has actually
+        // taken over since (this was a real bug: the abandoned socket's
+        // delayed onclose was silently orphaning a perfectly live
+        // connection, with nothing left referencing it to send on).
+        if (socketRef.current !== ws) return
         setConnected(false)
         socketRef.current = null