diff --git a/evals/ask_user.eval.ts b/evals/ask_user.eval.ts
new file mode 100644
index 0000000000..c67f995168
--- /dev/null
+++ b/evals/ask_user.eval.ts
@@ -0,0 +1,92 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, expect } from 'vitest';
+import { evalTest } from './test-helper.js';
+
+describe('ask_user', () => {
+  evalTest('USUALLY_PASSES', {
+    name: 'Agent uses AskUser tool to present multiple choice options',
+    prompt: `Use the ask_user tool to ask me what my favorite color is. Provide 3 options: red, green, or blue.`,
+    assert: async (rig) => {
+      const wasToolCalled = await rig.waitForToolCall('ask_user');
+      expect(wasToolCalled, 'Expected ask_user tool to be called').toBe(true);
+    },
+  });
+
+  evalTest('USUALLY_PASSES', {
+    name: 'Agent uses AskUser tool to clarify ambiguous requirements',
+    files: {
+      'package.json': JSON.stringify({ name: 'my-app', version: '1.0.0' }),
+    },
+    prompt: `I want to build a new feature in this app. Ask me questions to clarify the requirements before proceeding.`,
+    assert: async (rig) => {
+      const wasToolCalled = await rig.waitForToolCall('ask_user');
+      expect(wasToolCalled, 'Expected ask_user tool to be called').toBe(true);
+    },
+  });
+
+  evalTest('USUALLY_PASSES', {
+    name: 'Agent uses AskUser tool before performing significant ambiguous rework',
+    files: {
+      'packages/core/src/index.ts': '// index\nexport const version = "1.0.0";',
+      'packages/core/src/util.ts': '// util\nexport function help() {}',
+      'packages/core/package.json': JSON.stringify({
+        name: '@google/gemini-cli-core',
+      }),
+      'README.md': '# Gemini CLI',
+    },
+    prompt: `Refactor the entire core package to be better.`,
+    assert: async (rig) => {
+      const wasPlanModeCalled = await rig.waitForToolCall('enter_plan_mode');
+      expect(wasPlanModeCalled, 'Expected enter_plan_mode to be called').toBe(
+        true,
+      );
+
+      const wasAskUserCalled = await rig.waitForToolCall('ask_user');
+      expect(
+        wasAskUserCalled,
+        'Expected ask_user tool to be called to clarify the significant rework',
+      ).toBe(true);
+    },
+  });
+
+  // --- Regression Tests for Recent Fixes ---
+
+  // Regression test for issue #20177: Ensure the agent does not use `ask_user` to
+  // confirm shell commands. Fixed via prompt refinements and tool definition
+  // updates to clarify that shell command confirmation is handled by the UI.
+  // See fix: https://github.com/google-gemini/gemini-cli/pull/20504
+  evalTest('USUALLY_PASSES', {
+    name: 'Agent does NOT use AskUser to confirm shell commands',
+    files: {
+      'package.json': JSON.stringify({
+        scripts: { build: 'echo building' },
+      }),
+    },
+    prompt: `Run 'npm run build' in the current directory.`,
+    assert: async (rig) => {
+      await rig.waitForTelemetryReady();
+
+      const toolLogs = rig.readToolLogs();
+      const wasShellCalled = toolLogs.some(
+        (log) => log.toolRequest.name === 'run_shell_command',
+      );
+      const wasAskUserCalled = toolLogs.some(
+        (log) => log.toolRequest.name === 'ask_user',
+      );
+
+      expect(
+        wasShellCalled,
+        'Expected run_shell_command tool to be called',
+      ).toBe(true);
+      expect(
+        wasAskUserCalled,
+        'ask_user should not be called to confirm shell commands',
+      ).toBe(false);
+    },
+  });
+});