codebase-designlisted

# Codebase Design Design modules that hide meaningful complexity behind a small, stable interface. This vocabulary and discipline are adapted from Matt Pocock's MIT-licensed `codebase-design` skill; see `NOTICE`. ## Vocabulary - **Module** — an interface plus its implementation, at any scale. - **Interface** — everything callers must know: operations, invariants, error modes, ordering, configuration, and performance expectations. - **Seam** — where behavior can vary without editing the caller. - **Adapter** — a concrete implementation that occupies a seam. - **Depth** — useful behavior delivered per unit of interface callers learn. - **Leverage** — capability reused by many callers through one interface. - **Locality** — changes, knowledge, bugs, and verification concentrated in one place. ## Design tests ### Deletion test Imagine deleting the module: - If complexity disappears, it may be a pass-through. - If the complexity spreads back across callers, the module is earning its place. ### Interface test Callers and tests should use the same supported seam. If tests must reach through the interface into internals, either the test is coupled to implementation or the module is shaped incorrectly. ### Variation test One adapter is often a hypothetical abstraction. Introduce a seam when behavior actually varies, external effects need isolation, or the interface meaningfully concentrates complexity. ## Deepening workflow 1. Identify repeated knowledge or coordina