chore: address copilot comments

web/src/components/ChatSidebar.tsx

@@ -87,6 +87,7 @@ export function ChatSidebar({ channel, className }: ChatSidebarProps) {
   const [error, setError] = useState<string | null>(null);
 
   useEffect(() => {
+    let cancelled = false;
     const offState = gw.onState(setState);
 
     const offSessionInfo = gw.on<SessionInfo>("session.info", (ev) => {
@@ -111,15 +112,26 @@ export function ChatSidebar({ channel, className }: ChatSidebarProps) {
     // sidecar is independent of the PTY pane's session by design — we
     // only need a sid to drive the model picker's slash.exec calls.
     gw.connect()
-      .then(() => gw.request<{ session_id: string }>("session.create", {}))
-      .then((created) => {
-        if (created?.session_id) {
-          setSessionId(created.session_id);
+      .then(() => {
+        if (cancelled) {
+          return;
         }
+        return gw.request<{ session_id: string }>("session.create", {});
       })
-      .catch((e: Error) => setError(e.message));
+      .then((created) => {
+        if (cancelled || !created?.session_id) {
+          return;
+        }
+        setSessionId(created.session_id);
+      })
+      .catch((e: Error) => {
+        if (!cancelled) {
+          setError(e.message);
+        }
+      });
 
     return () => {
+      cancelled = true;
       offState();
       offSessionInfo();
       offError();

web/src/components/ModelPickerDialog.tsx

@@ -138,7 +138,7 @@ export function ModelPickerDialog({ gw, sessionId, onClose, onSubmit }: Props) {
 
   return (
     <div
-      className="fixed inset-0 z-100 flex items-center justify-center bg-background/85 backdrop-blur-sm p-4"
+      className="fixed inset-0 z-[100] flex items-center justify-center bg-background/85 backdrop-blur-sm p-4"
       onClick={(e) => e.target === e.currentTarget && onClose()}
       role="dialog"
       aria-modal="true"

web/src/pages/ChatPage.tsx

@@ -443,6 +443,10 @@ export default function ChatPage() {
     const ws = new WebSocket(url);
     ws.binaryType = "arraybuffer";
     wsRef.current = ws;
+    // Suppress banner/terminal side-effects when cleanup() calls `ws.close()`
+    // (React StrictMode remount, route change) so we never write to a
+    // disposed xterm or setState on an unmounted tree.
+    let unmounting = false;
 
     ws.onopen = () => {
       setBanner(null);
@@ -463,6 +467,9 @@ export default function ChatPage() {
 
     ws.onclose = (ev) => {
       wsRef.current = null;
+      if (unmounting) {
+        return;
+      }
       if (ev.code === 4401) {
         setBanner("Auth failed. Reload the page to refresh the session token.");
         return;
@@ -539,6 +546,7 @@ export default function ChatPage() {
     term.focus();
 
     return () => {
+      unmounting = true;
       onDataDisposable.dispose();
       onResizeDisposable.dispose();
       if (metricsDebounce) clearTimeout(metricsDebounce);