fix(copilot): show helpful error message for third-party cookie blocking

frontend/src/components/chat/MessagesContainer/index.tsx

@@ -94,6 +94,9 @@ const MessagesContainer = ({ navigate }: Props) => {
   const knownSideElementsRef = useRef<Map<string, IMessageElement>>(new Map());
   const knownSideOrderRef = useRef<string[]>([]);
 
+  // Check if side panel should auto-open based on config
+  const shouldAutoOpenSidePanel = config?.features?.side_panel?.default_state !== 'closed';
+
   useEffect(() => {
     const sideElements = elements.filter((e) => e.display === 'side');
 
@@ -104,6 +107,12 @@ const MessagesContainer = ({ navigate }: Props) => {
       return;
     }
 
+    // If default_state is 'closed', don't auto-open the side panel
+    // User must manually click to open it via onElementRefClick
+    if (!shouldAutoOpenSidePanel) {
+      return;
+    }
+
     const prevMap = knownSideElementsRef.current;
     const prevOrder = knownSideOrderRef.current;
     const currentIds = sideElements.map((e) => e.id);
@@ -123,7 +132,7 @@ const MessagesContainer = ({ navigate }: Props) => {
         elements: sideElements
       });
     }
-  }, [elements]);
+  }, [elements, shouldAutoOpenSidePanel]);
 
   const onElementRefClick = useCallback(
     (element: IMessageElement) => {

libs/copilot/src/app.tsx

@@ -55,6 +55,30 @@ export default function App({ widgetConfig }: Props) {
 
   const defaultTheme = widgetConfig.theme || data?.default_theme;
 
+  // Detect third-party cookie blocking errors
+  const isCookieBlockedError = (error: string): boolean => {
+    const lowerError = error.toLowerCase();
+    return (
+      lowerError.includes('set-cookie') ||
+      lowerError.includes('cookie') ||
+      lowerError.includes('blocked') ||
+      lowerError.includes('third-party') ||
+      lowerError.includes('third party')
+    );
+  };
+
+  // Format error message with helpful instructions for cookie issues
+  const formatAuthError = (err: unknown): string => {
+    const errorStr = String(err);
+    if (isCookieBlockedError(errorStr)) {
+      return (
+        'Authentication failed due to third-party cookies being blocked. ' +
+        'Please allow third-party cookies in your browser settings to use the Copilot.'
+      );
+    }
+    return errorStr;
+  };
+
   useEffect(() => {
     if (fetchError) return;
     if (!isAuthenticated) {
@@ -63,7 +87,7 @@ export default function App({ widgetConfig }: Props) {
       } else {
         apiClient
           .jwtAuth(widgetConfig.accessToken)
-          .catch((err) => setAuthError(String(err)));
+          .catch((err) => setAuthError(formatAuthError(err)));
       }
     } else {
       setAuthError(undefined);

libs/react-client/src/types/config.ts

@@ -67,6 +67,9 @@ export interface IChainlitConfig {
     }[];
   };
   features: {
+    side_panel?: {
+      default_state?: 'open' | 'closed';
+    };
     spontaneous_file_upload?: {
       enabled?: boolean;
       max_size_mb?: number;