Auto-formats Python (ruff) and JS/TS/HTML/JSON/MD/YAML (prettier) the moment Claude edits them.
A PostToolUse hook fires after every Write and Edit call, resolves the file path (relative paths resolve against the session cwd), picks a formatter by extension, and formats the file in place: uv run ruff check --fix then uv run ruff format for .py, npx --yes prettier --write for .js, .ts, .json, .md, .yaml, .yml, and .html. File paths are passed as argv, never through a shell, so filenames with shell metacharacters cannot inject commands. Unsupported extensions and missing files are skipped silently, a formatter failure never blocks the session, and every outcome (FORMATTED / SKIP / ERROR) is logged.
/plugin marketplace add karanb192/claude-code-hooks # once per machine
/plugin install format-code@claude-code-hooks
Restart Claude Code, done. (Or from a shell: claude plugin install format-code@claude-code-hooks.)
| Event | Runs | What happens |
|---|---|---|
PostToolUse (Write|Edit) |
sync | Formats the touched file in place with ruff (Python) or prettier (JS/TS/JSON/MD/YAML/HTML), then returns {} so the session continues either way. |
Formatters run from your PATH: Python formatting needs uv (which runs ruff), the rest needs npx (Node); npx --yes fetches prettier on first use if it is not already installed. If a formatter is missing, the hook logs the error and moves on without blocking.
No configuration needed, and no environment variables to set. Logs go to ~/.claude/hooks-logs/<date>.jsonl (the log directory is derived from $HOME).
Rewrites the edited file in place and records file paths, formatter outcomes, and session ids in the local log. The hook itself makes no network calls; the one indirect exception is npx --yes prettier, which downloads prettier from the npm registry the first time if it is not installed locally.
/plugin uninstall format-code@claude-code-hooks
Part of claude-code-hooks, a collection of production-ready Claude Code hooks, each installable on its own as a plugin.