Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add mrDesign-ww/vault-os --skill lean-buildgit clone --depth 1 https://github.com/mrDesign-ww/vault-osWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/mrdesign-ww/vault-os/lean-build)<a href="https://agentmods.dev/skills/mrdesign-ww/vault-os/lean-build"><img src="https://agentmods.dev/badge/skills/mrdesign-ww/vault-os/lean-build/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/mrdesign-ww/vault-os/lean-build"><img src="https://agentmods.dev/badge/skills/mrdesign-ww/vault-os/lean-build.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00036 | $0.00208 |
| Opus 5 | $0.00018 | $0.00104 |
| Sonnet 5 | $0.00007 | $0.00042 |
| Haiku 4.5 | $0.00004 | $0.00021 |
Grade A, and why
lean-build scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
Lean build
Native Core's architecture-first simplicity remains mandatory. Turn feature into complete narrow outcome fitting system.
- Derive observable acceptance and explicit non-goals from request and repository.
- Trace entry point through layers owning invariants.
- Deliver coherent end-to-end path across responsible layers; never force work into one file, direct expression, or local patch.
- Reuse fitting seam. Refactor when patching duplicates behavior, weakens ownership, or hides root cause.
- Omit modes, providers, config, extensibility, and polish unless acceptance needs them.
- Add surface, dependency, service, config, or migration only for lifecycle design or acceptance; state material tradeoff.
- Keep work runnable; preserve Core safety.
Exercise path. Run focused proof. Stop when acceptance passes. Report only material omissions and trigger.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 7d ago First seen · 19 lines · 36 tokens per session scan A 4d498073c631
lean-build is a skill published in the GitHub repository mrDesign-ww/vault-os (2 stars, last pushed 5d ago), licensed MIT. It adds 36 tokens to every session and 208 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-05.
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