Rigor is a CLI-first static analyzer for Ruby applications that prioritizes type inference, clean application code, and zero runtime dependencies. Rigor is a standalone tool, not a library: install it independently rather than adding it to your application's Gemfile. It runs on Ruby 4.0 while your project keeps its own Ruby, and it reads your project as data rather than loading it, so a Gemfile entry only constrains your application's Ruby and dependency resolution. Installation channels (mise, asdf, gem install, container, Nix): https://github.com/rigortype/rigor/blob/master/docs/install.md