fix(core): avoid error handling on cancelled requests to prevent crash (#6039)

Co-authored-by: Jacob Richman <jacob314@gmail.com>

packages/core/src/core/turn.test.ts

@@ -445,6 +445,32 @@ describe('Turn', () => {
         { type: GeminiEventType.Finished, value: 'OTHER' },
       ]);
     });
+
+    it('should not crash when cancelled request has malformed error', async () => {
+      const abortController = new AbortController();
+
+      const errorToThrow = {
+        response: {
+          data: undefined, // Malformed error data
+        },
+      };
+
+      mockSendMessageStream.mockImplementation(async () => {
+        abortController.abort();
+        throw errorToThrow;
+      });
+
+      const events = [];
+      const reqParts: Part[] = [{ text: 'Test malformed error handling' }];
+
+      for await (const event of turn.run(reqParts, abortController.signal)) {
+        events.push(event);
+      }
+
+      expect(events).toEqual([{ type: GeminiEventType.UserCancelled }]);
+
+      expect(reportError).not.toHaveBeenCalled();
+    });
   });
 
   describe('getDebugResponses', () => {

packages/core/src/core/turn.ts

@@ -247,16 +247,17 @@ export class Turn {
         }
       }
     } catch (e) {
-      const error = toFriendlyError(e);
-      if (error instanceof UnauthorizedError) {
-        throw error;
-      }
       if (signal.aborted) {
         yield { type: GeminiEventType.UserCancelled };
         // Regular cancellation error, fail gracefully.
         return;
       }
 
+      const error = toFriendlyError(e);
+      if (error instanceof UnauthorizedError) {
+        throw error;
+      }
+
       const contextForReport = [...this.chat.getHistory(/*curated*/ true), req];
       await reportError(
         error,