diff --git a/packages/core/src/core/geminiChat.test.ts b/packages/core/src/core/geminiChat.test.ts
index c8b53fe4c..aacdcad07 100644
--- a/packages/core/src/core/geminiChat.test.ts
+++ b/packages/core/src/core/geminiChat.test.ts
@@ -145,7 +145,7 @@ describe('GeminiChat', async () => {
         /* consume */
       }
     })();
-    // Register rejection handler BEFORE advancing timers to avoid unhandled rejection.
+    // Get assertion promise first (don't await), then advance timers to avoid deadlock.
     const resultPromise =
       await expect(collecting).rejects.toThrow(InvalidStreamError);
     await vi.advanceTimersByTimeAsync(35_000);