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black-box-architecture

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Apply Eskil Steenberg's black box architecture principles to build modular, maintainable software. Automatically refactors code into replaceable components, designs system architectures with clean boundaries, and debugs with modular isolation.

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Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/data/black-box-architecture/SKILL.md

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Black Box Architecture Skill

This skill teaches Claude to apply Eskil Steenberg's battle-tested black box architecture principles for building modular, maintainable software systems.

Philosophy

"It's faster to write 5 lines of code today than to write 1 line today and then have to edit it in the future." — Eskil Steenberg

Optimize for:

  • Human cognitive load over algorithmic efficiency
  • Long-term maintainability over short-term cleverness
  • Team scalability (one person per module)
  • Constant developer velocity regardless of project size

Core Principles

  1. Primitive-First Design - Identify core data types that flow through your system
  2. Black Box Boundaries - Modules communicate only through documented interfaces
  3. Replaceable Components - Any module can be rewritten using only its interface
  4. Single Responsibility - One module = one person can own it
  5. Wrap Dependencies - Never depend directly on code you don't control

Variants

This skill has three specialized variants that are automatically selected based on your request:

Refactor Variant

When to use: Code refactoring, breaking apart monoliths, creating module boundaries

Triggers:

  • "Refactor [code/class/module]"
  • "Break apart this monolith"
  • "Create black box modules"
  • "Analyze [component] and suggest modular refactoring"

File: refactor.md

Plan Variant

When to use: Strategic architecture planning, designing new systems

Triggers:

  • "Design architecture for [system]"
  • "Plan the module structure"
  • "How should I architect [feature]"
  • "Design a [type] system"

File: plan.md

Debug Variant

When to use: Systematic debugging, testing strategies, integration issues

Triggers:

  • "Debug [issue]"
  • "Fix this bug"
  • "Why is [component] failing"
  • "Test strategy for [feature]"

File: debug.md

Output Format

All variants follow a structured 4-phase protocol and produce consistent output:

## 🔍 Current Architecture
[Primitives, modules, coupling issues, violations]

## 🎯 Proposed Black Box Design
[Module designs with interfaces]

## 📝 Implementation Steps
[Specific, actionable steps]

## ⚠️ Risks & Mitigation
[What could go wrong + how to prevent]

## ✅ Quality Gates
[Validation checklist]

Supported Languages

  • Python
  • TypeScript/JavaScript
  • Go
  • Rust
  • C
  • PHP
  • Java

Learn More

Based on Eskil Steenberg's lecture: Architecting LARGE Software Projects