Code craft

Prove what the types can, then test only what they cannot. Every invariant has one owner: the strongest rung of the proof ladder that can actually prove it. In order: types and linters, effects, proofs, database constraints, unit tests, integration tests, end-to-end tests.

Use the repository's current instructions and established conventions. Apply these defaults where the requested change needs a design decision; they do not authorize unrelated restructuring or new tooling.

Read the reference for the decision in scope: