ast-grep vs Hound

ast-grep is a free, open-source tool for structural code search, linting, and rewriting. It matches patterns against syntax-tree nodes, helping developers locate and change code across a codebase rather than searching plain text. Its CLI can preview and apply rewrites interactively, and scan configurable YAML rules with error, warning, info, or hint severity. Rules can combine pattern, kind, regex, relational, and composite conditions, and CLI commands help create and snapshot-test them. The project says it supports more than 20 languages and can load custom languages. JavaScript and WebAssembly APIs allow programmatic syntax-tree work; a browser playground offers a way to try patterns without local installation. Editor options include a VS Code extension and language-server setups, including for Vim and Neovim. The tool is free, has a web interface, and is distributed through package managers or built from source. Its FAQ notes that some advanced static-analysis information is unsupported, and one rule cannot target multiple languages at once.

Hound is a free source code search engine that indexes repositories and offers a web interface and a minimal API. Its Go backend maintains a current index for each repository, while its static React frontend provides the web UI. Search uses regular-expression matching with a trigram index. Hound supports Git, Mercurial, SVN, Bazaar, and local repositories; private repositories can be indexed from local directories or reached through file or SSH-style URLs. By default, it checks configured repository URLs for updates every 30 seconds, with an interval that can be changed per repository. It can be built from source or run from the project's Docker image, and the web UI defaults to localhost:6080. Plugins are available for Sublime Text, Vim, Emacs, and Visual Studio Code. Hound is tested on macOS and CentOS and is expected to work on Unix-like systems, but Windows is not supported. It does not support TLS itself; the README suggests running it behind Apache or nginx. Hound uses the MIT license, and the latest listed release is v0.7.1, published May 3, 2023.