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 BuildGreatProducts/builder-os --skill build-loop-codexgit clone --depth 1 https://github.com/BuildGreatProducts/builder-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/buildgreatproducts/builder-os/build-loop-codex)<a href="https://agentmods.dev/skills/buildgreatproducts/builder-os/build-loop-codex"><img src="https://agentmods.dev/badge/skills/buildgreatproducts/builder-os/build-loop-codex/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/buildgreatproducts/builder-os/build-loop-codex"><img src="https://agentmods.dev/badge/skills/buildgreatproducts/builder-os/build-loop-codex.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
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 | $0.00147 | $0.00801 |
| Opus 5.5 | $0.00059 | $0.00320 |
| Sonnet 5.5 | $0.00029 | $0.00160 |
| Haiku 4.5 | $0.00015 | $0.00080 |
Grade A, and why
build-loop-codex 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 1mo 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.
This is a copy
91% identical to build-loop-claude-code — 8 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 40 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Codex Build Loop
Quality-gated feature work: nothing ships on "it compiles" — every increment is built, reviewed, tested end to end, and fixed before the user hears "done."
Source of work
- A plan file exists (roadmap, refactor plan, or task list with
- [ ]checkboxes — search the repo): work the first unchecked task. Tasks are ordered intentionally — never skip ahead. If the plan references spec docs, read only the sections relevant to the current task. - No plan (or the request is outside it): build from the user's prompt. Restate it as a verifiable goal with 2–4 success criteria and confirm scope in one message before building.
The loop
Run per task (or per prompted feature). Do not advance until every step passes.
-
Build. Implement exactly what the task specifies. Simplest implementation that satisfies it, surgical changes, no speculative scope. Match existing project conventions.
-
Review. Run
/reviewand select "Review uncommitted changes". If the change touches auth, payments, user input, or data access, run a second pass via "Custom review instructions" (e.g. "Focus on security vulnerabilities and unvalidated input"). Fix all findings in scope — bugs, security issues, edge cases, performance, style in files you touched. If the project has a design system spec (design tokens file, DESIGN.md, theme config), check UI changes against it — no hardcoded colors, type, or spacing that bypass tokens. Note pre-existing issues in untouched code for the report instead of fixing silently. Re-run/reviewuntil clean. If a finding contradicts the task or spec, the spec wins — flag the disagreement. -
Test end to end. Run the task's verification step (or the success criteria). Run the full test suite — everything that passed before must still pass. Add tests for new logic. Then exercise the feature as a user would: run the app, walk the real flow including empty, loading, and error states.
-
Fix. Anything testing finds goes back through the loop: fix →
/review→ re-test. Never mark a failing task complete; never start the next task with the app broken.
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.
- 1mo ago First seen · 40 lines · 147 tokens per session scan A 2d620370d55a
build-loop-codex is a skill published in the GitHub repository BuildGreatProducts/builder-os (231 stars, last pushed 3mo ago), licensed MIT. It adds 147 tokens to every session and 801 once invoked, about $0.0006 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 91% identical to build-loop-claude-code, differing in 8 lines, and is treated as a copy.
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