# Codebase Design (agent skill)

> Codebase Design is an agent skill (a SKILL.md file) from mattpocock/skills. Shared vocabulary for designing deep modules. It works with Claude Code and Codex and has 278,361 GitHub stars across a repository of 15 listed skills. Install it by copying the skill folder into your agent's skills directory.

Shared vocabulary for designing deep modules. Use when the user wants to design or improve a module's interface, find deepening opportunities, decide where a seam goes, make code more testable or AI-navigable, or when another skill needs the deep-module vocabulary. Design deep modules: a lot of behaviour behind a small interface, placed at a clean seam, testable through that interface. Use this language and these principles wherever code is being designed or restructured.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/mattpocock/skills |
| Skill path | skills/engineering/codebase-design/SKILL.md |
| Skill name | codebase-design |
| GitHub stars | 278,361 |
| Installs on skills.sh | 744,272 |
| License | MIT |
| Skills in repo | 15 |
| Plugin marketplace | mattpocock |
| Official | no |
| Works with | Claude Code, Codex |
| Category | Design & frontend |
| Last commit | Oct 6, 2026 |

## When it triggers

- Use when the user wants to design or improve a module's interface, find deepening opportunities, decide where a seam goes, make code more testable or AI-navigable, or when another skill needs the deep-module vocabulary.

## Add this skill

### Claude Code

```sh
/plugin marketplace add mattpocock/skills
/plugin install mattpocock-skills@mattpocock
```

In the Claude apps, zip the skill folder and upload it under Customize > Skills > + > Upload a skill (code execution must be on).

### ChatGPT / Codex

```sh
git clone --depth 1 https://github.com/mattpocock/skills.git
cp -r skills/skills/engineering/codebase-design .agents/skills/codebase-design   # repo; ~/.agents/skills for all projects
```

### Cursor

```sh
git clone --depth 1 https://github.com/mattpocock/skills.git
cp -r skills/skills/engineering/codebase-design .cursor/skills/codebase-design   # project; ~/.cursor/skills for all projects
```

Sources (checked 2026-10-07): https://code.claude.com/docs/en/skills, https://support.claude.com/en/articles/12512180-using-skills-in-claude, https://learn.chatgpt.com/docs/build-skills, https://cursor.com/docs/context/skills

skills.sh listing: https://www.skills.sh/mattpocock/skills/codebase-design

---

Canonical page: https://appsgit.com/skills/mattpocock-codebase-design
Source: appsgit (https://appsgit.com), the app store for github. Data from the GitHub API, refreshed nightly.
Machine access: JSON API https://appsgit.com/api/v1/apps (OpenAPI: https://appsgit.com/openapi.json), MCP server https://mcp.appsgit.com/mcp, full index https://appsgit.com/llms-full.txt.