Claude Code hook that formats and lints each file after Claude edits it

Agents often leave formatting drift and lint errors that you then fix by hand or catch in CI. This hook runs after every `Edit` or `Write` tool call, formats the changed file with your project's own tools, and, when a linter still reports problems, returns them to Claude so it fixes them in the same session.

**How it decides what to run** By file extension, and only if the tool is available in the project: - `.js .jsx .ts .tsx .mjs .cjs .json .css .scss .md .yaml .yml .html .vue .svelte`: Prettier, only when it is installed locally (`node_modules/.bin/prettier`). For JS and TS files it also runs ESLint with `--fix` if installed locally, and reports remaining errors. - `.py`: `ruff format` and `ruff check --fix`, through `uv run` when a `uv.lock` exists or a `ruff` binary otherwise. Remaining Ruff errors are reported. - `.go`: `gofmt -w`. - `.rs`: `rustfmt` on the file, using your `rustfmt.toml` if present. - `.php`: Laravel Pint (`vendor/bin/pint`) if installed.

Files outside the project directory are skipped. Tools that are not installed are skipped silently, so the hook never blocks work because of missing tooling.

**How errors reach Claude** For `PostToolUse`, exit code 2 sends the hook's stderr to Claude as feedback (the edit has already happened, so nothing is undone). The script uses that only for lint errors that remain after auto-fix, and keeps the message short.

**Limits** It formats single files, so project-wide checks such as type checking still belong in CI or a pre-commit step. It uses your configuration files; it does not add formatter config of its own. Requires `jq`.