ruff is not compiled into uv; it's bootstrapped from an independent build, much like how `cargo fmt` is bootstrapped from a separate toolchain component (rustfmt). You can see how that works in the PR[1]. Importantly, that means that you don't experience any build-, install-, or run-time burden if you don't use this subcommand.

[1]: https://github.com/astral-sh/uv/pull/15017