Add onError handler to useAssistant hook (#818)

Co-authored-by: Max Leiter <max.leiter@vercel.com>

.changeset/mean-deers-try.md

@@ -0,0 +1,5 @@
+---
+'ai': patch
+---
+
+react/use-assistant: add onError handler

docs/pages/docs/api-reference/use-assistant.mdx

@@ -114,6 +114,11 @@ export default function Chat() {
       'any',
       'An optional, additional body object to be passed to the API endpoint.',
     ],
+    [
+      'onError',
+      '(err: Error) => void',
+      'An optional callback that will be called when the assistant encounters an error',
+    ],
   ]}
 />
 

packages/core/react/use-assistant.ts

@@ -86,6 +86,11 @@ export type UseAssistantOptions = {
    * An optional, additional body object to be passed to the API endpoint.
    */
   body?: object;
+
+  /**
+   * An optional callback that will be called when the assistant encounters an error.
+   */
+  onError?: (error: Error) => void;
 };
 
 export function experimental_useAssistant({
@@ -94,12 +99,13 @@ export function experimental_useAssistant({
   credentials,
   headers,
   body,
+  onError,
 }: UseAssistantOptions): UseAssistantHelpers {
   const [messages, setMessages] = useState<Message[]>([]);
   const [input, setInput] = useState('');
   const [threadId, setThreadId] = useState<string | undefined>(undefined);
   const [status, setStatus] = useState<AssistantStatus>('awaiting_message');
-  const [error, setError] = useState<unknown | undefined>(undefined);
+  const [error, setError] = useState<undefined | Error>(undefined);
 
   const handleInputChange = (
     event:
@@ -193,13 +199,18 @@ export function experimental_useAssistant({
           }
 
           case 'error': {
-            setError(value);
+            const errorObj = new Error(value);
+            setError(errorObj);
             break;
           }
         }
       }
     } catch (error) {
-      setError(error);
+      if (onError && error instanceof Error) {
+        onError(error);
+      }
+
+      setError(error as Error);
     }
 
     setStatus('awaiting_message');