# spec

> Claude/Codex skill by [@juliusbrussee](https://omgskills.com/library/juliusbrussee/index.md) · 1.1k stars · Updated 2026-08-14

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.

Tags: claude-code, parallel-agents, skills, spec-driven-development, test-driven-development

## Install

```sh
git clone https://github.com/JuliusBrussee/cavekit /tmp/cavekit && ln -s /tmp/cavekit/skills/spec ~/.claude/skills/spec
```

## From README

spec — spec mutator Read FORMAT.md at repo root if not already loaded. Caveman skill applies to all writes here. DISPATCH Inspect user request and project state: No SPEC.md at repo root AND args describe idea → NEW No SPEC.md AND from-code in args → DISTILL SPEC.md exists AND args start bug: → BACKPROP SPEC.md exists AND args start amend → AMEND SPEC.md exists, no args → ask user which mode INPUTS — spec is the sole mutator The other verbs produce material; spec writes it. Ingest their handoff blocks into the right section, show a diff, write on OK: grill → sharpened §G + §C research → §R rows (add the §R section if absent) review → drafted §V lines + the risk verdict deepen → §I/§V/§T amendments ⊥ rewrite a section the handoff did not name. Sectioned ownership (see FORMAT.md). NEW — idea → spec Input: user idea. If it arrived fuzzy, prefer running grill first. Steps: Extract goal (1 line, caveman). → §G. List constraints user stated or implied. → §C.

## Links

- HTML page: https://omgskills.com/skills/juliusbrussee/cavekit/spec/
- GitHub: https://github.com/JuliusBrussee/cavekit
- Author: [@juliusbrussee](https://omgskills.com/library/juliusbrussee/index.md)

## More from this repo

- [backprop](https://omgskills.com/skills/juliusbrussee/cavekit/backprop/index.md) — Bug → spec protocol.
   - [@juliusbrussee](https://omgskills.com/library/juliusbrussee/index.md) · 1.1k stars
- [build](https://omgskills.com/skills/juliusbrussee/cavekit/build/index.md) — Plan-then-execute implementation against SPEC.md.
   - [@juliusbrussee](https://omgskills.com/library/juliusbrussee/index.md) · 1.1k stars
- [caveman](https://omgskills.com/skills/juliusbrussee/cavekit/caveman/index.md) — Caveman encoding for SPEC.md and spec-adjacent writes.
   - [@juliusbrussee](https://omgskills.com/library/juliusbrussee/index.md) · 1.1k stars