# Check (agent skill)

> Check is an agent skill (a SKILL.md file) from JuliusBrussee/cavekit. Read-only drift detector. Diffs SPEC.md against current code and reports violations grouped by severity. It works with Claude Code and Codex and has 1,148 GitHub stars across a repository of 2 listed skills.

Read-only drift detector. Diffs SPEC.md against current code and reports violations grouped by severity. Writes nothing — suggests remedies via the spec or build skills but never invokes them. Triggers when the user asks to check drift, audit the spec, verify invariants, or ask whether code still matches the spec. Phrasings: "check drift", "audit the spec", "does the code still match §V", "check invariants", "spec vs code". Pure diagnostic. Reports violations. Writes nothing.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/JuliusBrussee/cavekit |
| Skill path | skills/check/SKILL.md |
| Skill name | check |
| 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 | Security |
| Last commit | Aug 14, 2026 |

## When it triggers

- Triggers when the user asks to check drift, audit the spec, verify invariants, or ask whether code still matches the spec.
- "check drift"
- "audit the spec"
- "does the code still match §V"
- "check invariants"
- "spec vs code"

## 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/check .agents/skills/check   # repo; ~/.agents/skills for all projects
```

### Cursor

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