diff --git a/src/main/agent/deepseek-harness-extension-loader.test.ts b/src/main/agent/deepseek-harness-extension-loader.test.ts
index 3f010e3c..987e3f29 100644
--- a/src/main/agent/deepseek-harness-extension-loader.test.ts
+++ b/src/main/agent/deepseek-harness-extension-loader.test.ts
@@ -112,9 +112,10 @@ describe('DeepSeek Harness extension loader', () => {
 
   it('bounds the complete extension startup sequence', async () => {
     const ctx = new Context()
-    const importModule = vi.fn(
-      () => new Promise<never>(() => undefined)
-    )
+    const importModule = vi.fn(async () => {
+      blockEventLoop(25)
+      return {}
+    })
 
     const result = await loadControlledHarnessExtensions(
       ctx,