fix(cli): handle flash model errors gracefully (#12667)

packages/core/src/fallback/handler.test.ts

@@ -73,14 +73,15 @@ describe('handleFallback', () => {
     expect(mockConfig.setFallbackMode).not.toHaveBeenCalled();
   });
 
-  it('should return null if the failed model is already the fallback model', async () => {
+  it('should still consult the handler if the failed model is the fallback model', async () => {
+    mockHandler.mockResolvedValue('stop');
     const result = await handleFallback(
       mockConfig,
       FALLBACK_MODEL, // Failed model is Flash
       AUTH_OAUTH,
     );
-    expect(result).toBeNull();
-    expect(mockHandler).not.toHaveBeenCalled();
+    expect(result).toBe(false);
+    expect(mockHandler).toHaveBeenCalled();
   });
 
   it('should return null if no fallbackHandler is injected in config', async () => {

packages/core/src/fallback/handler.ts

@@ -21,8 +21,6 @@ export async function handleFallback(
 
   const fallbackModel = DEFAULT_GEMINI_FLASH_MODEL;
 
-  if (failedModel === fallbackModel) return null;
-
   // Consult UI Handler for Intent
   const fallbackModelHandler = config.fallbackModelHandler;
   if (typeof fallbackModelHandler !== 'function') return null;