How to contribute

🚨 Read AGENTS.md first. This repository is in maintenance mode. TypeScript 6.0 is the last JavaScript-based release. Most code changes belong in microsoft/typescript-go, not here.

The maintainers will accept PRs in this repository only for:

• Crashes introduced in 5.9 or 6.0 that also reproduce in 7.0 and have a portable fix without behavioural changes.
• Security issues.
• Language-service crashes that substantially impact mainline usage.
• Serious 5.9 regressions that affect a large proportion of users.
• Non-disruptive lib.d.ts updates.

Anything else — new features, refactors, general bug fixes — should go to typescript-go. The compiler team has explicitly asked contributors to direct their effort there.

This section assumes you have an issue that fits the maintenance criteria and you are preparing to submit a PR.

Pages

• Development workflow — branch, fork, build, test, PR.
• Testing — runners, fourslash syntax, baseline workflow.
• Debugging — printf-debugging, Debug.assert*, the inspector.
• Patterns and conventions — coding style and architectural conventions.
• Tooling — hereby, dprint, ESLint, knip, esbuild, dtsBundler.

Quick checklist before submitting a PR

1. Tests pass locally. npx hereby runtests-parallel — 10–15 minutes is normal.
2. Lint passes. npx hereby lint. Fix all issues; no exceptions.
3. Format is clean. npx hereby format.
4. Baselines match. git diff tests/baselines shows only intentional, justified changes.
5. The PR description references the issue. Link to the bug and quote the relevant AGENTS.md criterion.
6. AI assistance is disclosed. Per CONTRIBUTING.md, if AI tools were used in producing the PR, say so in the description. Undisclosed AI-authored PRs are closed without review.
7. Line endings. Source files use CRLF. Make sure your editor and Git config preserve them.

Communication

• The issue tracker is for bugs and suggestions, not questions. Use Stack Overflow or the TypeScript Community Discord for questions.
• Don't post "I'm going to work on this" comments on issues — see the CONTRIBUTING.md rationale. Pick an issue tagged Help Wanted or Backlog, do the work, send the PR.
• Avoid force-pushing — the team reviews the PR title and description rather than the commit history, but force-pushes make it harder to review iterations.

Maintainer expectations

• PRs should be against main.
• Tests must change in a way that demonstrates the fix.
• Baseline diffs should be reviewed line-by-line — surprising baseline changes often indicate unrelated regressions.
• Don't add automated comments to issues or PRs. Per the recently added comment-automation policy in CONTRIBUTING.md, automated comments will trigger an immediate block.