manage complexity through boundaries Shipped
What this lens looks for
Define ports (interfaces) describing what the application needs; use adapters to translate between external technologies and ports; test core application without databases, UIs, or networks; subsystems evolve independently behind their boundary
What its verifier checks
Core business logic has no imports of UI, database, or network frameworks; adapters implement port interfaces; core can be unit-tested without infrastructure; at least one integration test verifies adapter-to-port wiring