# build

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

Plan-then-execute implementation against SPEC.md. Native single-thread loop, no sub-agents. On test or build failure, auto-invokes the backprop skill before retrying — a failed verification always considers whether a new §V invariant would prevent recurrence. Triggers when the user asks to build, implement, execute the spec, or tackle a specific §T task (\`build §T.3\`, \`build --next\`, \`implement next task\`, \`run the build\`). Expects SPEC.md to exist; if not, defers to the spec skill.

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/build ~/.claude/skills/build
```

## From README

build — implement spec Single-thread native plan→execute. You are main Claude. No swarm. LOAD Read SPEC.md. If missing → tell user to invoke the spec skill first. Stop. Read FORMAT.md once if not loaded. Read §R if present — external facts the build must honor, ⊥ re-derive or contradict. Parse invocation args: §T.n → that task only --next → lowest-numbered row with status . or --all or empty → every . row in §T order High blast radius (shared module, auth, data, money, public §I)? Run /review first. Trivial & reversible? Skip planning ceremony, just do step EXECUTE. PLAN Native plan mode — you delegate to it, you do not reinvent task breakdown. For chosen task(s): Cite every §V invariant that applies. Plan must respect all. Cite every §I interface touched. Plan must preserve shape. List files to create / edit. Verification contract — name the EXACT test(s) / acceptance criteria that prove each §V touched. Which test, not "add tests".

## Links

- HTML page: https://omgskills.com/skills/juliusbrussee/cavekit/build/
- 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
- [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
- [check](https://omgskills.com/skills/juliusbrussee/cavekit/check/index.md) — Read-only drift detector.
   - [@juliusbrussee](https://omgskills.com/library/juliusbrussee/index.md) · 1.1k stars