Selective functional patterns

Functional patterns solve specific modeling defects. They are not a default architecture or an extra layer to place around working project types.

Start with the owning boundary

Follow this order and stop at the first step that satisfies the task:

1. Reuse the owning boundary's existing schema, generated type, library type, or public contract.
2. Infer types with the installed tool's supported utilities.
3. Compose, refine, or extend the canonical schema or type.
4. Improve the representation at its owner when the task exposes a real gap.
5. Introduce one minimal custom type only when the hard gate below is satisfied.

Do not continue down the list once the existing representation can express the requirement safely.