diff --git a/tests/fixtures.ts b/tests/fixtures.ts
index 5c6c166..8b3a24b 100644
--- a/tests/fixtures.ts
+++ b/tests/fixtures.ts
@@ -91,6 +91,8 @@ export const test = baseTest.extend<TestFixtures & TestOptions, WorkerFixtures>(
       const transport = createTransport(args, mcpMode);
       let stderr = '';
       transport.stderr?.on('data', data => {
+        if (process.env.PWMCP_DEBUG)
+          process.stderr.write(data);
         stderr += data.toString();
       });
       await client.connect(transport);