# Darwin Hexagonal > Hexagonal Architecture (Ports & Adapters) patterns for code review and planning. Use when reviewing code structure, planning new features, or evaluating coupling. Use when this capability is needed. - Skill: `tomevault-io/darwin-hexagonal` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add tomevault-io/darwin-hexagonal` - Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/darwin-hexagonal/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: tomevault-io (https://skillmd.com/u/tomevault-io) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/tomevault-io/darwin-hexagonal --- # Hexagonal Architecture (Ports & Adapters) ## Core Principles - **Core domain isolation**: Business logic MUST have zero import dependencies on infrastructure. No `import redis`, `import kubernetes`, `import requests` in domain modules. - **Ports**: Interfaces defined BY the core domain (e.g., `class EventStore(Protocol)`, `class MetricsProvider(Protocol)`). The core says what it needs; adapters provide it. - **Adapters**: Implementations of ports for specific technologies (e.g., `RedisEventStore`, `K8sMetricsProvider`). Adapters import infrastructure libraries; the core never does. - **Dependency direction**: Always inward. Adapters depend on ports. Core depends on nothing external. ## When Reviewing Code - Flag any business logic file that directly imports a database client, HTTP library, or cloud SDK - Recommend extracting a port (interface) to decouple - If a change modifies both a port interface and its adapter, flag it in the risk assessment ## When Planning New Features - Specify which port the new code enters through - Specify which adapter will implement it - If the port doesn't exist yet, design it as part of the plan - Boundary crossings (modifying port + adapter) carry higher risk --- > Converted and distributed by [TomeVault](https://tomevault.io/claim/the-darwin-project) — claim your Tome and manage your conversions.