fix(scripts): scrub CI / CONTINUOUS_INTEGRATION env vars in dev mode to keep ink interactive

[pmenic]

Summary

npm run start hangs silently after the banner whenever the developer's shell has CI=true or CONTINUOUS_INTEGRATION=true. is-in-ci — loaded transitively by ink inside the spawned child — reads those env vars and makes ink disable interactive rendering.

The bundled path closes this via an esbuild alias that replaces is-in-ci with a constant false (#4822). That alias is never applied in the unbundled dev flow, so the silent-hang regression still bites contributors. See #22452 for the report.

This change strips the offending vars from the env passed to the dev child in scripts/start.js and prints a one-line stderr warning listing what was removed, plus a short note that the variables are not propagated to shell-tool subprocesses in dev (pointing developers who need them to the bundled build).

Scope is intentionally limited to scripts/start.js, so the bundled and production paths are untouched.

Scope of the filter

The filter targets exactly the two variables is-in-ci@2.0.0 actually consults:

// node_modules/ink/node_modules/is-in-ci/index.js
const check = (key) =>
  key in env && env[key] !== '0' && env[key] !== 'false';
const isInCi = check('CI') || check('CONTINUOUS_INTEGRATION');

Issue #22452 claimed any CI_*-prefixed variable also triggered the hang, but the is-in-ci source above shows that is not the case at the version pinned here. The filter therefore intentionally does not touch CI_TOKEN, CI_BUILD_ID, or any other CI_* developer-set token — those continue to propagate to the CLI process and to shell-tool subprocesses, matching the bundled-build behavior.

The filter also mirrors is-in-ci's truthiness rule (skip 0, false, or unset), so a developer who explicitly sets CI=0 to mark "not in CI" still sees no-op behavior here.

Why this approach

Two alternatives considered and rejected:

• Runtime module shim of is-in-ci to mirror the bundled alias: requires a --import preloader or ESM loader hook for the dev flow, more moving parts, and still requires changing the spawn invocation.
• Scrub inside packages/cli/index.ts at process startup: would also run in the bundled binary, duplicating the alias work and printing the warning in production for users who never see a hang.

Scrubbing only in the dev launcher is the smallest change that covers the bug, leaves production semantics untouched, and is naturally gated by the dev-mode entry point.

Test plan

Verified manually on Windows (the change is platform-neutral; pure env filtering in Node):

• CI=true CI_TOKEN=x node scripts/start.js --version → warning lists only CI; CI_TOKEN preserved
• CI=0 node scripts/start.js --version → no warning (matches is-in-ci falsy rule)
• CONTINUOUS_INTEGRATION=1 node scripts/start.js --version → warning lists CONTINUOUS_INTEGRATION
• No CI / CONTINUOUS_INTEGRATION set → no warning printed
• node -c scripts/start.js — syntax OK
• npx eslint scripts/start.js --max-warnings 0 — clean
• pre-commit hook (prettier + eslint --fix) passes

Note: I did not add an automated test because scripts/start.js is a small integration-flavored launcher and exercising it end-to-end would require driving a real interactive Node child. Happy to extract the filter into a tiny pure helper with a unit test if reviewers prefer.

Fixes #22452

[gemini-code-assist]

Summary of Changes

Hello, 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 addresses a regression where the development environment would hang silently when 'CI' or 'CONTINUOUS_INTEGRATION' environment variables were present. By filtering these specific variables in the development launcher, the CLI ensures that the 'ink' library maintains interactive rendering capabilities during local development, matching the behavior of the production bundled build.

Highlights

• CI Environment Variable Filtering: Added logic to scripts/start.js to detect and remove 'CI' and 'CONTINUOUS_INTEGRATION' environment variables before spawning the development child process.
• Interactive Rendering Fix: Prevents the 'ink' library from incorrectly detecting a CI environment, which previously caused the development server to hang silently.
• Developer Feedback: Implemented a stderr warning that notifies developers when these variables are stripped, while explicitly preserving other 'CI_*' variables like tokens.

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[gemini-code-assist]

Code Review

This pull request updates scripts/start.js to strip CI-detection environment variables, specifically CI and CONTINUOUS_INTEGRATION, before spawning the development child process. This change ensures that the ink library maintains interactive rendering during npm run start, preventing the process from hanging in environments where these variables are set. I have no feedback to provide as there were no review comments.

[pmenic]

Closing in favor of #25287 (aniruddhaadak80, opened 2026-04-13). I missed the existing PR when I picked up #22452 — should have searched for prior PRs first. Left a comment on #25287 with the correctness deltas from this PR's review for whoever lands the final fix.