fix(acp): --experimental-acp no longer stops the world in tty mode

[sillyDaibo]

TLDR

When running gemini --experimental-acp in tty mode (e.g. in your bash), the terminal will totally freeze in 2 seconds, and even Ctrl-C cannot be sent to it.

If you run docker with -t to enable tty and --experimental-acp to enable acp mode, the problem also exists. Removing -t can bypass the problem, but sometimes we still want to debug in tty mode.

This pr fixes the problem with only one-line modification, thus it's only a small and safe fix. I've tested it on linux and through docker, both works perfectly.

Dive Deeper

Reviewer Test Plan

Testing Matrix

	🍏	🪟	🐧
npm run	❓	❓	✅
npx	❓	❓	❓
Docker	❓	❓	✅
Podman	❓	-	-
Seatbelt	❓	-	-

Linked issues / bugs

[google-cla]

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[gemini-code-assist]

Summary of Changes

Hello @sillyDaibo, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical issue where enabling the --experimental-acp flag in a TTY environment caused the gemini application to become unresponsive. The change ensures that the application correctly determines its interactive state when this experimental flag is active, thereby preventing the terminal from freezing and improving the user experience for developers debugging in TTY mode.

Highlights

• Fix for --experimental-acp freezing in TTY: When gemini is run with the --experimental-acp flag in a TTY environment, the terminal would previously freeze completely. This pull request introduces a fix to prevent this behavior, ensuring the application remains responsive.

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[gemini-code-assist]

Code Review

This change correctly prevents the CLI from entering interactive mode when --experimental-acp is used in a TTY, which fixes the reported terminal freeze. The logic is sound and the fix is well-targeted. To ensure this fix is permanent and to prevent future regressions, I've suggested adding a unit test.

[gemini-code-assist]

This change correctly makes the CLI non-interactive when --experimental-acp is passed. To prevent future regressions for this bug fix, please add a unit test that verifies this new behavior.

You can add a test case to packages/cli/src/config/config.test.ts inside the loadCliConfig interactive describe block, like this:

it('should not be interactive if --experimental-acp is set, even in a TTY', async () => {
  process.stdin.isTTY = true;
  process.argv = ['node', 'script.js', '--experimental-acp'];
  const argv = await parseArguments({} as Settings);
  const config = await loadCliConfig({}, [], 'test-session', argv);
  expect(config.isInteractive()).toBe(false);
});

[bdmorgan]

Hi @sillyDaibo, thank you so much for your contribution to Gemini CLI! We really appreciate the time and effort you've put into this.

We're making some updates to our contribution process to improve how we track and review changes. Please take a moment to review our recent discussion post: Improving Our Contribution Process & Introducing New Guidelines.

Key Update: Starting January 26, 2026, the Gemini CLI project will require all pull requests to be associated with an existing issue. Any pull requests not linked to an issue by that date will be automatically closed.

Thank you for your understanding and for being a part of our community!

[bdmorgan]

Thank you for submission to the Gemini CLI project. At this time, we are closing this pull request in order to allow us to better triage and support more recent pull requests against the latest code changes. If you feel like this pull request is a critical contribution to the Gemini CLI project, please associate the pull request with an existing GitHub issue (instructions here: https://docs.github.com/en/issues/tracking-your-work-with-issues/using-issues/linking-a-pull-request-to-an-issue) before reopening. After Monday January 26 2026, any pull requests submitted by contributors without an associated issue will be automatically closed (more information here: #16706). If you do choose to reopen and submit this pull request, please ensure you rebase your changes onto the current main branch before resubmitting. This will help avoid merge conflicts and ensure your contribution is compatible with the latest codebase.