# App Composition Rules

- `app/` is the composition root for runtime wiring.
- Create registries, stores, command sets, input adapters, and renderer/view adapters here.
- Do not implement domain rules, command behavior, rendering backend logic, or React UI here.
- App composition may import from all layers, but lower layers must not import from `app/`.
- Keep factories testable; avoid module-level mutable singleton state unless explicitly required by the runtime entrypoint.