How do I install the Codex Sparring skill?

Run npx skillmds@latest add mace-enterprise/codex-sparring in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Codex Sparring safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Codex Sparring?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Codex Sparring free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Codex Sparring?

Mace-Enterprise (@mace-enterprise) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Codex Sparring by mace-enterprise — Agent Skill

Name: Codex Sparring
Author: Mace-Enterprise

Codex Sparring

Get a second opinion from Codex (a different model) on an idea, plan, or code question — adversarial sparring to catch blind spots a same-model review misses. Use deliberately for weighty decisions. Read-only; costs the user's Codex credits.

File contents

Codex sparring

Invoke the local Codex CLI as an independent sparring partner: a different model challenges the idea/plan/code and we weigh its feedback. Model diversity catches blind spots Claude reviewing Claude won't.

When to use

Deliberately, for specific weighty calls — a design/architecture decision, a risky plan, or a "is this code right?" question. Not on every step: each call costs the user's Codex/OpenAI credits and runs a fresh session. Confirm before spending credits unless the user already said "ask Codex".

How — Codex MUST get context + code access

Codex starts a fresh session with no memory of our chat, so the call must carry the context. For code questions, run it inside the repo so it can read AGENTS.md + the actual code:

codex exec -C <repo-dir> -s read-only "SPARRING: <idea/plan/decision, stated concisely>.
Context Codex needs: <facts, constraints, what we already decided>.
Code is in this repo — read <relevant paths> as needed.
Play devil's advocate: challenge assumptions, find flaws/risks/blind spots, propose
alternatives. Be concrete and critical — don't just agree. Read-only: change nothing."

-C <repo-dir> → Codex's working root = the repo, so it sees AGENTS.md + the code.
-s read-only → sandbox: Codex can read files / run read commands but cannot modify anything.
Put the real question + enough context in the prompt; name specific files/paths for code questions. Capture stdout and relay it.

After

Relay Codex's feedback, then add your own take: where it's right, where it's wrong or missing our context, and what (if anything) we change. Codex advises; we decide.

Guardrails

Read-only only — never --full-auto or --dangerously-bypass-approvals-and-sandbox for sparring.
Costs the user's credits → deliberate, confirm first.
Fresh external session → never assume it knows prior chat; never feed it secrets.

Troubleshooting

unknown variant 'xhigh', model requires a newer Codex, or model … not supported with a ChatGPT account → the Codex CLI is behind your account/config. Fix: upgrade it (npm i -g @openai/codex@latest), then the config defaults work. One-off bypass without editing config: add -c model_reasoning_effort=high and/or -m <supported-model>.
Verified on Codex CLI 0.141 + a ChatGPT account (model gpt-5.5). Output ≈70k tokens for a high-effort read+critique of ~6 pages.

Status: active (promoted 2026-06-19 — first real sparring run read the wiki read-only and returned a sharp, actionable critique that caught two real inconsistencies). See [[skill-and-agent-probation-lifecycle]].

---name: codex-sparringdescription: Get a second opinion from Codex (a different model) on an idea, plan, or code question — adversarial sparring to catch blind spots a same-model review misses. Use deliberately for weighty decisions. Read-only; costs the user's Codex credits.---# Codex sparringInvoke the local **Codex CLI** as an independent sparring partner: a *different model*challenges the idea/plan/code and we weigh its feedback. Model diversity catches blindspots Claude reviewing Claude won't.## When to useDeliberately, for **specific** weighty calls — a design/architecture decision, a riskyplan, or a "is this code right?" question. **Not** on every step: each call costs theuser's Codex/OpenAI credits and runs a fresh session. Confirm before spending creditsunless the user already said "ask Codex".## How — Codex MUST get context + code accessCodex starts a **fresh session with no memory of our chat**, so the call must carry thecontext. For **code questions, run it inside the repo** so it can read `AGENTS.md` + theactual code:```bashcodex exec -C <repo-dir> -s read-only "SPARRING: <idea/plan/decision, stated concisely>.Context Codex needs: <facts, constraints, what we already decided>.Code is in this repo — read <relevant paths> as needed.Play devil's advocate: challenge assumptions, find flaws/risks/blind spots, proposealternatives. Be concrete and critical — don't just agree. Read-only: change nothing."```- `-C <repo-dir>` → Codex's working root = the repo, so it **sees `AGENTS.md` + the code**.- `-s read-only` → sandbox: Codex can **read** files / run read commands but **cannot modify** anything.- Put the real question + enough context in the prompt; name specific files/paths for code questions. Capture stdout and relay it.## AfterRelay Codex's feedback, then add your own take: where it's right, where it'swrong or missing our context, and what (if anything) we change. **Codex advises; we decide.**## Guardrails- Read-only only — never `--full-auto` or `--dangerously-bypass-approvals-and-sandbox` for sparring.- Costs the user's credits → deliberate, confirm first.- Fresh external session → never assume it knows prior chat; **never feed it secrets**.## Troubleshooting- **`unknown variant 'xhigh'`, `model requires a newer Codex`, or `model … not supported with a ChatGPT account`** → the Codex CLI is behind your account/config. Fix: upgrade it (`npm i -g @openai/codex@latest`), then the config defaults work. One-off bypass without editing config: add `-c model_reasoning_effort=high` and/or `-m <supported-model>`.- Verified on Codex CLI **0.141** + a ChatGPT account (model `gpt-5.5`). Output ≈70k tokens for a high-effort read+critique of ~6 pages.**Status:** active (promoted 2026-06-19 — first real sparring run read the wiki read-only and returned a sharp, actionable critique that caught two real inconsistencies). See [[skill-and-agent-probation-lifecycle]].

Frequently asked questions