fix(frontend): stabilize thread id when sending messages

frontend/src/app/workspace/chats/[thread_id]/page.tsx

@@ -200,9 +200,9 @@ export default function ChatPage() {
         return;
       }
       setHasSubmitted(true);
-      void sendMessage(threadId, message);
+      void sendMessage(safeThreadId, message);
     },
-    [isSelectedSkillBootstrapping, sendMessage, threadId],
+    [isSelectedSkillBootstrapping, safeThreadId, sendMessage],
   );
   const handleStop = useCallback(async () => {
     await thread.stop();

frontend/src/core/threads/hooks.ts

@@ -69,6 +69,15 @@ function getStreamErrorMessage(error: unknown): string {
   return "Request failed.";
 }
 
+function normalizeThreadId(
+  value: string | null | undefined,
+): string | undefined {
+  if (!value) return undefined;
+  const normalized = value.trim();
+  if (!normalized || normalized === "new") return undefined;
+  return normalized;
+}
+
 export function useThreadStreamLegacy({
   threadId,
   isNewThread,
@@ -155,12 +164,14 @@ export function useThreadStream({
   }, [onStart, onFinish, onToolEnd]);
 
   useEffect(() => {
-    const normalizedThreadId = threadId ?? null;
+    const normalizedThreadId = normalizeThreadId(threadId) ?? null;
     if (!normalizedThreadId) {
       // Just reset for new thread creation when threadId becomes null/undefined
       startedRef.current = false;
-      setOnStreamThreadId(normalizedThreadId);
     }
+    setOnStreamThreadId((prev) =>
+      prev === normalizedThreadId ? prev : normalizedThreadId,
+    );
     threadIdRef.current = normalizedThreadId;
   }, [threadId]);
 
@@ -288,7 +299,9 @@ export function useThreadStream({
 
       const text = message.text.trim();
       const resolvedThreadId =
-        threadId ?? threadIdRef.current ?? undefined;
+        normalizeThreadId(threadId) ??
+        normalizeThreadId(threadIdRef.current) ??
+        undefined;
       if (resolvedThreadId === "new") {
         toast.error("Invalid thread id 'new'. Please refresh and retry.");
         sendInFlightRef.current = false;