Hexagonal Architecture (Ports and Adapters).

Why this matters here

Cockburn’s hexagonal architecture (ports and adapters) protects core domain logic behind stable boundaries so external systems can change without entangling business rules. Coupling uses that boundary discipline after “shift left”: earlier detection helps only if the system can still adapt without destabilizing everything it touches. The source argues for intentional coupling at the edge; the book asks whether faster feedback still fails when core logic remains fused to dependencies.