How does this skill improve the testing process?

By defining clear boundaries between core logic and external effects, it helps identify exactly what should be unit tested (the core) versus what requires integration testing (the edge).

What is the 'Functional Core' pattern used in this skill?

The Functional Core pattern involves placing all business logic, validation, and domain rules in pure, deterministic components that are isolated from I/O operations, making them highly testable.

When is the best time to invoke the Architect skill?

Use it during the initial design phase of a feature, when modeling domain entities, or when planning how different system components should interact.

Is this skill limited to specific programming languages?

No, while the provided examples often use TypeScript, the DDD and hexagonal architecture patterns are universal architectural principles applicable to any backend language.

Atelier Spec Architect

Name: Atelier Spec Architect
Author: martinffx

bymartinffx

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API Development

Design robust software systems using Domain-Driven Design (DDD) and hexagonal architecture with a functional core pattern.

Atelier Spec Architect provides a structured framework for Claude to guide software design using industry-standard patterns like DDD and Hexagonal Architecture. It enforces a strict separation between the Functional Core (pure business logic and entities) and the Effectful Edge (I/O operations like databases and APIs). This skill is essential for developers looking to build maintainable, testable, and scalable systems by providing clear implementation patterns for entities, services, and repositories while mapping architectural boundaries directly to testing strategies.

Key Features

01Connects architectural decisions to specific unit and integration testing flows

02Implements Domain-Driven Design (DDD) for complex business logic modeling

03Establishes bottom-up dependency ordering for efficient feature implementation

04Separates pure functional core logic from side-effectful edge I/O operations

056 GitHub stars

06Provides structured templates for Entities, Services, Repositories, and Routers

Use Cases

01Breaking down high-level product requirements into a technical implementation roadmap

02Refactoring monolithic or legacy code into a testable hexagonal architecture

03Designing new microservices or features with complex domain rules and validations

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add martinffx/claude-code-atelier atelier-spec-architect

For use in Claude.ai and ChatGPT

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