How do I install the Codex skill?

Run npx skillmds add majiayu000/codex-5 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 safe to use?

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

Which AI agents work with Codex?

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 free to use?

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

majiayu000 (@majiayu000) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Codex by majiayu000 — Agent Skill

Name: Codex
Rating: 4.2 (5 reviews)
Author: majiayu000

File contents

Codex Subagent

Run OpenAI Codex CLI (GPT-5.2) for second opinions and external reviews.

Availability Check

Before using Codex, verify it's installed:

which codex >/dev/null 2>&1 || echo "CODEX_NOT_INSTALLED"

If not installed, inform the user: "Codex CLI is not installed. Skipping Codex review."

Execution Pattern

OUTPUT_FILE=$(mktemp)
codex exec \
  --skip-git-repo-check \
  --dangerously-bypass-approvals-and-sandbox \
  -o "$OUTPUT_FILE" \
  "$PROMPT" 2>/dev/null
cat "$OUTPUT_FILE"
rm "$OUTPUT_FILE"

Flags

Flag	Purpose
`exec`	Non-interactive mode
`--skip-git-repo-check`	Run outside git repositories
`--dangerously-bypass-approvals-and-sandbox`	No prompts, no sandbox restrictions
`-o <file>`	Capture clean output to file
`2>/dev/null`	Suppress session info and stderr noise

Timeout

Codex can take several minutes for complex prompts. Use 15 minute timeout:

timeout 900 codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox -o "$OUTPUT_FILE" "$PROMPT" 2>/dev/null

Usage Examples

Simple Question

OUTPUT_FILE=$(mktemp)
codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox -o "$OUTPUT_FILE" \
  "What are the tradeoffs between Redis and Memcached for session storage?" 2>/dev/null
cat "$OUTPUT_FILE"
rm "$OUTPUT_FILE"

Code Review

DIFF=$(git diff main...HEAD)
OUTPUT_FILE=$(mktemp)
codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox -o "$OUTPUT_FILE" \
  "Review this diff for issues:

$DIFF

List concerns with severity (blocking/important/nice-to-have)." 2>/dev/null
cat "$OUTPUT_FILE"
rm "$OUTPUT_FILE"

With Working Directory

OUTPUT_FILE=$(mktemp)
codex exec --dangerously-bypass-approvals-and-sandbox -C /path/to/repo -o "$OUTPUT_FILE" \
  "Analyze the architecture of this codebase" 2>/dev/null
cat "$OUTPUT_FILE"
rm "$OUTPUT_FILE"

GitHub PR Review

Codex has access to gh CLI. Pass the PR URL and let it fetch the diff:

OUTPUT_FILE=$(mktemp)
timeout 900 codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox -o "$OUTPUT_FILE" \
  "Review this PR: https://github.com/owner/repo/pull/123

   Use gh CLI to get the diff and review for issues." 2>/dev/null
cat "$OUTPUT_FILE"
rm "$OUTPUT_FILE"

Notes

Codex uses GPT-5.2, providing genuinely different perspective from Claude
Each call is stateless - no conversation continuity
API costs apply per call
Output may contain duplicates - parse accordingly

---name: codex-5description: Run OpenAI Codex CLI as a subagent for second opinions, code reviews, and questions. Use when you want a different AI model's perspective.--- # Codex Subagent Run OpenAI Codex CLI (GPT-5.2) for second opinions and external reviews. ## Availability Check Before using Codex, verify it's installed: ```bash which codex >/dev/null 2>&1 || echo "CODEX_NOT_INSTALLED" ``` If not installed, inform the user: "Codex CLI is not installed. Skipping Codex review." ## Execution Pattern ```bash OUTPUT_FILE=$(mktemp) codex exec \ --skip-git-repo-check \ --dangerously-bypass-approvals-and-sandbox \ -o "$OUTPUT_FILE" \ "$PROMPT" 2>/dev/null cat "$OUTPUT_FILE" rm "$OUTPUT_FILE" ``` ### Flags | Flag | Purpose | |------|---------| | `exec` | Non-interactive mode | | `--skip-git-repo-check` | Run outside git repositories | | `--dangerously-bypass-approvals-and-sandbox` | No prompts, no sandbox restrictions | | `-o <file>` | Capture clean output to file | | `2>/dev/null` | Suppress session info and stderr noise | ### Timeout Codex can take several minutes for complex prompts. Use 15 minute timeout: ```bash timeout 900 codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox -o "$OUTPUT_FILE" "$PROMPT" 2>/dev/null ``` ## Usage Examples ### Simple Question ```bash OUTPUT_FILE=$(mktemp) codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox -o "$OUTPUT_FILE" \ "What are the tradeoffs between Redis and Memcached for session storage?" 2>/dev/null cat "$OUTPUT_FILE" rm "$OUTPUT_FILE" ``` ### Code Review ```bash DIFF=$(git diff main...HEAD) OUTPUT_FILE=$(mktemp) codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox -o "$OUTPUT_FILE" \ "Review this diff for issues: $DIFF List concerns with severity (blocking/important/nice-to-have)." 2>/dev/null cat "$OUTPUT_FILE" rm "$OUTPUT_FILE" ``` ### With Working Directory ```bash OUTPUT_FILE=$(mktemp) codex exec --dangerously-bypass-approvals-and-sandbox -C /path/to/repo -o "$OUTPUT_FILE" \ "Analyze the architecture of this codebase" 2>/dev/null cat "$OUTPUT_FILE" rm "$OUTPUT_FILE" ``` ### GitHub PR Review Codex has access to `gh` CLI. Pass the PR URL and let it fetch the diff: ```bash OUTPUT_FILE=$(mktemp) timeout 900 codex exec --skip-git-repo-check --dangerously-bypass-approvals-and-sandbox -o "$OUTPUT_FILE" \ "Review this PR: https://github.com/owner/repo/pull/123 Use gh CLI to get the diff and review for issues." 2>/dev/null cat "$OUTPUT_FILE" rm "$OUTPUT_FILE" ``` ## Notes - Codex uses GPT-5.2, providing genuinely different perspective from Claude - Each call is stateless - no conversation continuity - API costs apply per call - Output may contain duplicates - parse accordingly

Frequently asked questions