diff --git a/scripts/eval_scenarios/performance_vague_test.ts b/scripts/eval_scenarios/performance_vague_test.ts
new file mode 100644
index 000000000..e31803ab8
--- /dev/null
+++ b/scripts/eval_scenarios/performance_vague_test.ts
@@ -0,0 +1,27 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import assert from 'node:assert';
+
+import type {TestScenario} from '../eval_gemini.ts';
+
+export const scenario: TestScenario = {
+  prompt: 'I want to make my page fast. Page URL is <TEST_URL>.',
+  maxTurns: 2,
+  htmlRoute: {
+    path: '/index.html',
+    htmlContent: `
+      <script>for (let i = 0; i < 1000; i++) {console.log("slow");}</script>
+    `,
+  },
+  expectations: calls => {
+    assert.strictEqual(calls.length, 2);
+    assert.ok(
+      calls[0].name === 'navigate_page' || calls[0].name === 'new_page',
+    );
+    assert.ok(calls[1].name === 'performance_start_trace');
+  },
+};