ast-grep

ast-grep is a structural code search and rewriting CLI built on tree-sitter ASTs. It lets you match code by syntax shape, then run one-off rewrites or reusable lint rules across supported languages.

• Search a repo for syntax patterns and captured nodes instead of raw text matches, including matches read from stdin or filtered by file globs.
• Rewrite matched code with replacement templates, either as targeted one-off codemods or bulk updates across many files.
• Define YAML rules, scaffold and test them, then run repo-wide scans that emit diagnostics or SARIF for CI and cleanup workflows.

• run and scan both support real --json output, and scan also emits SARIF, so matches and diagnostics are straightforward to parse in follow-up steps.
• The CLI is built for non-interactive use first: paths, stdin, globs, inline rules, thread control, and inspect output make it easy to chain into search, edit, and verify loops.
• Best for codemods, lint enforcement, and targeted repository inspection; agents still need correct language selection and precise rules, while interactive review mode is mainly for humans.

• Coverage depends on supported parsers and correct language detection, so unsupported syntax or the wrong language choice will miss matches.
• Repeatable team workflows usually depend on checked-in rule files and sgconfig.yml; interactive rewrite sessions are less suitable for unattended runs.