# Working on wouter

Small, hook-based routing for React and Preact. Keep changes focused and avoid
adding runtime dependencies or unnecessary bytes.

This file is the shared source of instructions for coding agents. Keep guidance
here or in linked Markdown documents, rather than editor-specific rule files.

## Layout and commands

- `packages/wouter/src/` is the shared JavaScript implementation; types live in
  each package's `types/` directory.
- `wouter-preact` copies the shared sources and keeps its own `react-deps.js`.
  Edit shared sources in `wouter`, and check both packages when changing APIs.
- Use Bun: `bun install --frozen-lockfile`, `bun test --coverage`,
  `bun run test-types`, and `bun run lint`.
- Run `bun run --cwd packages/wouter-preact prepublishOnly` before
  `bun run size`; the tests remove their temporary Preact source copies.
- Packages ship source files directly. There is no separate bundle build.
- For releases, follow [RELEASING.md](RELEASING.md). npm is used only for packing
  and publishing through GitHub Actions with trusted publishing.

## Development principles

- Preserve backward compatibility. Update both packages' type definitions and the
  README when changing a public API.
- Use hooks and functions; preserve stable references where callers rely on them
  to avoid unnecessary renders.
- Add focused regression tests for behavior changes. Use `memoryLocation` for
  isolated routing tests; check React, Preact, and SSR when relevant.
- Check bundle size for runtime changes. Support performance claims with a
  before-and-after measurement.

## Pull request descriptions

- Start with the problem and the resulting behavior in 1–3 sentences.
- For a small fix, aim for 50–120 words. Add detail only when it helps review.
- Explain why; let the diff show which files and functions changed.
- Include an example or screenshot when it makes the change easier to understand.
- Mention material risks or compatibility changes, if any, and checks actually run.
- Skip template headings for short PRs, debugging diaries, repeated summaries,
  agent attribution, and session links.
- Keep the title specific and the description accurate as the implementation changes.