diff --git a/packages/core/src/agent/content-utils.test.ts b/packages/core/src/agent/content-utils.test.ts
index 53fe867c59..0ed681c078 100644
--- a/packages/core/src/agent/content-utils.test.ts
+++ b/packages/core/src/agent/content-utils.test.ts
@@ -192,11 +192,16 @@ describe('contentPartsToGeminiParts', () => {
     const content = [
       { type: 'custom_widget', payload: 123 },
     ] as unknown as ContentPart[];
+    const warnSpy = vi.spyOn(debugLogger, 'warn');
     const result = contentPartsToGeminiParts(content);
+
+    expect(warnSpy).toHaveBeenCalled();
     expect(result).toHaveLength(1);
     expect(result[0]).toEqual({
       text: JSON.stringify({ type: 'custom_widget', payload: 123 }),
     });
+
+    warnSpy.mockRestore();
   });
 });