What problem does it solve? Teams lack a consistent language for discussing module design, leading to shallow abstractions, misplaced seams, and interfaces that are hard to test or navigate. This Skill establishes a precise shared vocabulary (module, interface, seam, adapter, depth, leverage, locality) so design discussions and refactors stay grounded in the same principles. ## Core Features & Use Cases - Deep-module vocabulary: Defines module, interface, implementation, seam, adapter, depth, leverage, and locality with explicit terms to avoid. - Design principles: Includes the deletion test, interface-as-test-surface, and the one-adapter-vs-two-adapters rule for deciding when a seam is real. - Testability guidance: Shows concrete TypeScript patterns for dependency injection, returning results instead of side effects, and minimizing interface surface area. - Use Case: When refactoring a tangled service layer, use this vocabulary to decide where the seam belongs, whether the module is deep enough to justify its interface, and how to make it testable through that interface. ## Quick Start Ask the AI to review a module's interface using the deep-module vocabulary and suggest where the seam should go.
