mainframe-peer-review

mainframe-peer-review is a skill for Claude Code, Codex from CATWILLgh/MAINFRAME. It costs 56 tokens per session (609 once invoked), scanned A, original, MIT.

A checkpoint tool for asking a separately installed Codex command-line agent to independently review an important decision or completed implementation.

In plain words
What is it for?
Use it to review architecture choices, consequential decisions, or finished changes. Prepare a neutral brief with evidence, assumptions, acceptance conditions, and affected files.
Why use it?
It helps reveal blind spots without handing over ownership of the work. The review is limited to a defined checkpoint and read-only inspection.

Skill for Claude CodeCodex

Written for Claude Code and Codex: allowed-tools in frontmatter, but also runs codex exec. Also seen: mentions Codex.

Install

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.

agentmods
npx agentmods add skills/catwillgh/mainframe/mainframe-peer-review
Any agent
npx skills add CATWILLgh/MAINFRAME --skill mainframe-peer-review
Clone the repo
git clone --depth 1 https://github.com/CATWILLgh/MAINFRAME

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for mainframe-peer-review

README.md
[![agentmods](https://agentmods.dev/badge/skills/catwillgh/mainframe/mainframe-peer-review.svg)](https://agentmods.dev/skills/catwillgh/mainframe/mainframe-peer-review)
Your own site
<a href="https://agentmods.dev/skills/catwillgh/mainframe/mainframe-peer-review"><img src="https://agentmods.dev/badge/skills/catwillgh/mainframe/mainframe-peer-review.svg" alt="Measured on agentmods" height="20"></a>
Per session 56 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 609 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00056 $0.00609
Opus 5 $0.00028 $0.00304
Sonnet 5 $0.00011 $0.00122
Haiku 4.5 $0.00006 $0.00061

Measured 5d ago against content hash f5532e2ea9f5, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

mainframe-peer-review 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 5d 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.

adapters/claude-code/optional/skills/mainframe-peer-review/SKILL.md · 56 lines

How it starts

The opening of the file, as written. The whole thing — 56 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Independent Codex review

Use Codex only to expose blind spots. The primary Claude session keeps ownership, verifies every material finding, and decides what changes.

Prepare

Inspect codex exec --help and codex exec resume --help. Create a temporary directory outside the repository and write a neutral English brief with the decision or final state, alternatives, load-bearing assumptions, verified evidence, acceptance conditions, and affected paths. Exclude secrets and unrelated transcript content.

Use gpt-5.6-sol with medium reasoning for complex, ambiguous, cross-cutting, or architectural work. Use xhigh only for irreversible data, money, security, broad production impact, or hard-to-reverse architecture.

Run

codex exec --ignore-user-config --strict-config \
  -C /absolute/repository -s read-only -m <model> \
  -c 'model_reasoning_effort="<effort>"' -c 'approval_policy="never"' --json \
  -o /absolute/temporary/answer.md \
  "$(< /absolute/temporary/brief.md)" < /dev/null \
  > /absolute/temporary/events.jsonl 2> /absolute/temporary/diagnostics.log

Read the final answer and obtain the exact thread_id from thread.started; never use --last. Treat a missing answer, failed process, or malformed event stream as unavailable, not approval. Verify every material finding before changing the decision.

Resume only when a newly verified material finding changes architecture, recommendation, definition of done, or load-bearing evidence. Send the revised package and a concise factual delta to the exact thread:

codex exec resume --ignore-user-config --strict-config <thread-id> -m <model> \
  -c 'model_reasoning_effort="<effort>"' -c 'sandbox_mode="read-only"' \
  -c 'approval_policy="never"' --json -o /absolute/temporary/answer-2.md \
  "$(< /absolute/temporary/follow-up-2.md)" < /dev/null \
  > /absolute/temporary/events-2.jsonl 2> /absolute/temporary/diagnostics-2.log

Allow at most three completed passes, keep model and reasoning stable unless a verified result proves under-classification, and never downgrade within a cycle. Remove temporary artifacts after reconciliation. Codex is an independent input, never the final authority.

Read the full file on GitHub · 56 lines

Changes

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.

  1. 5d ago First seen · 56 lines · 56 tokens per session scan A f5532e2ea9f5

Subscribe to this mod's changes

mainframe-peer-review is a skill published in the GitHub repository CATWILLgh/MAINFRAME (2 stars, last pushed 15d ago), licensed MIT. It adds 56 tokens to every session and 609 once invoked, about $0.0003 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 2026-08-31.

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