fix(dev): scrub CI env vars when running locally

[aniruddhaadak80]

Resolves #22452. In dev mode (npm run start), the CLI silently hangs if any environment variable with a CI_ prefix is set. This checks and ignores them during bootstrap.

[gemini-code-assist]

Summary of Changes

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This pull request improves the local development experience by preventing CI-specific environment variables from interfering with interactive processes. By automatically scrubbing these variables upon startup, the script ensures a more consistent local environment, while still providing an opt-out mechanism for specific use cases.

Highlights

• CI Environment Variable Scrubbing: Implemented a mechanism to automatically remove CI-related environment variables when running the development script locally to ensure proper interactive mode behavior.
• Opt-out Mechanism: Added a new flag --no-interactive-check that allows users to bypass the automatic scrubbing of CI environment variables.
• User Feedback: Added console error messages to inform the user when CI variables have been removed and how to suppress the check.

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[gemini-code-assist]

Code Review

This pull request updates scripts/start.js to automatically scrub CI-related environment variables (such as CI, CONTINUOUS_INTEGRATION, and those starting with CI_) from the environment configuration unless the --no-interactive-check flag is provided. This change ensures the CLI can operate in interactive mode even when detected in a CI environment, while providing console feedback about the removed variables. I have no feedback to provide as there were no review comments.

[pmenic]

Hi @aniruddhaadak80 — quick heads-up: I opened a near-identical PR (#26838) for #22452 yesterday without first searching for prior PRs, my bad. I'm closing mine in favor of this one since you got there first.

While iterating on #26838 with a reviewer I picked up two correctness points that I think also apply here — sharing them so you can roll them in if you agree:

1. Scope can be narrowed to CI / CONTINUOUS_INTEGRATION. The is-in-ci pinned in this repo is 2.0.0 (node_modules/ink/node_modules/is-in-ci/index.js), and its source is exactly:

const check = (key) => key in env && env[key] !== '0' && env[key] !== 'false';
const isInCi = check('CI') || check('CONTINUOUS_INTEGRATION');

There is no CI_* prefix check at this version — the issue body's claim that CI_TOKEN=anything triggers the hang doesn't match what is-in-ci@2.0.0 actually does. As written, the current diff scrubs legitimate developer tokens like CI_TOKEN / CI_BUILD_ID from both the CLI process and its shell-tool subprocesses unnecessarily.

2. Mirror is-in-ci's truthiness rule. A developer who explicitly sets CI=0 to mark "not in CI" should be a no-op (currently it would be stripped + warned about).

3. Warning copy. The line "These variables are still available in processes spawned by shell tools" doesn't match the implementation — once the var is deleted from the spawn env it's gone from grandchildren too. Worth either flipping the message to "unset in the CLI process and its shell-tool subprocesses" or actually preserving the vars via a side channel + re-injecting at spawn time (the latter is more invasive).

If it helps, the post-review diff I had landed in #26838 covers points 1+2+3 and is happy to be cherry-picked or just used as reference: https://github.com/google-gemini/gemini-cli/pull/26838/files

No urgency from my side — just wanted to leave the trail for whoever picks this up next.

[scidomino]

closing in favor of #27159