# Spec (agent skill)

> Spec is an agent skill (a SKILL.md file) from JuliusBrussee/cavekit. Create, amend, or backprop bugs into SPEC.md at repo root. It works with Claude Code and Codex and has 1,148 GitHub stars across a repository of 2 listed skills. Install it by copying the skill folder into your agent's skills directory.

Create, amend, or backprop bugs into SPEC.md at repo root. Sole mutator of the project spec. Triggers when the user asks to write a spec, start a new spec, distill a spec from existing code, add invariants, amend sections (§G, §C, §I, §V, §T, §B), or record a bug via backprop. Common phrasings: "write the spec for...", "new spec", "bug: ...", "amend §V.3", "distill spec from code", "spec this idea". Reads and follows FORMAT.md for the caveman encoding rules and pipe-table shape of §T and §B.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/JuliusBrussee/cavekit |
| Skill path | skills/spec/SKILL.md |
| Skill name | spec |
| GitHub stars | 1,148 |
| Installs on skills.sh | not listed |
| License | MIT |
| Skills in repo | 2 |
| Plugin marketplace | cavekit-marketplace |
| Official | no |
| Works with | Claude Code, Codex |
| Category | Testing & QA |
| Last commit | Aug 14, 2026 |

## When it triggers

- Triggers when the user asks to write a spec, start a new spec, distill a spec from existing code, add invariants, amend sections (§G, §C, §I, §V, §T, §B), or record a bug via backprop.
- "write the spec for..."
- "new spec"
- "bug: ..."
- "amend §V.3"
- "distill spec from code"
- "spec this idea"

## Add this skill

### Claude Code

```sh
/plugin marketplace add JuliusBrussee/cavekit
/plugin install ck@cavekit-marketplace
```

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/JuliusBrussee/cavekit.git
cp -r cavekit/skills/spec .agents/skills/spec   # repo; ~/.agents/skills for all projects
```

### Cursor

```sh
git clone --depth 1 https://github.com/JuliusBrussee/cavekit.git
cp -r cavekit/skills/spec .cursor/skills/spec   # 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

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Canonical page: https://appsgit.com/skills/juliusbrussee-spec
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