> For AI agents: the complete documentation index is available at /llms.txt, the full documentation bundle is available at /llms-full.txt. # File structure Assign code to the narrowest capability that owns it. ## Crates and modules ### Why Domain logic should not need a binary's terminal presentation to inspect a value. ### Rules - MUST separate reusable library behavior from binary presentation and resource adapters. \[review] - MUST keep `lib.rs` and `main.rs` entrypoints small and deliberate. \[review] - MUST expose only the supported public surface; prefer private or `pub(crate)` items internally. \[review] - MUST name modules for domain responsibilities rather than catch-all helpers. \[review] - MUST use explicit imports and re-exports rather than wildcard API surfaces. \[review] - MUST keep tests beside their capability or in the owning crate's integration tests. \[review] \[review] Cargo and the compiler validate module boundaries. Review checks ownership, public visibility, and entrypoint scope. ## Enforcement Cargo and the compiler validate module boundaries. Review checks ownership, public visibility, and entrypoint scope.