Codex Skill for Claude Code

Teach Claude Code how to invoke OpenAI's Codex CLI for advanced code analysis, refactoring, and automated editing.

A Claude Code skill that enables Claude to leverage OpenAI Codex CLI's advanced reasoning models for code reviews, refactoring, security audits, architecture analysis, and automated transformations.

Overview

This filesystem-based skill automatically activates when you mention Codex-related tasks. Simply ask Claude to review or refactor your code, and it will:

• Select optimal model (gpt-5.2 vs gpt-5.2-codex) and reasoning effort
• Execute Codex CLI with appropriate parameters and sandbox settings
• Handle session resume, error recovery, and multi-step workflows
• Summarize results and suggest next steps

Prerequisites

Before installing this skill:

• Codex CLI installed: The codex command must be available on your PATH
• Codex configured: Valid credentials in ~/.codex/config.toml
• Verify installation: Run codex --version to confirm setup

If you don't have Codex installed, see the Codex CLI documentation.

Installation

Clone and copy the skill to your .claude/skills directory:

Personal Installation (all projects):

# Unix/Linux/macOS
git clone --depth 1 https://github.com/sypsyp97/claude-skill-codex.git /tmp/codex-skill && \
mkdir -p ~/.claude/skills && cp -r /tmp/codex-skill/.claude/skills/codex ~/.claude/skills/codex && \
rm -rf /tmp/codex-skill

# Windows (PowerShell)
git clone --depth 1 https://github.com/sypsyp97/claude-skill-codex.git $env:TEMP\codex-skill; `
New-Item -ItemType Directory -Force -Path "$env:USERPROFILE\.claude\skills"; `
Copy-Item -Recurse -Force "$env:TEMP\codex-skill\.claude\skills\codex" "$env:USERPROFILE\.claude\skills\codex"; `
Remove-Item -Recurse -Force "$env:TEMP\codex-skill"

Project-Specific Installation:

# Unix/Linux/macOS
git clone --depth 1 https://github.com/sypsyp97/claude-skill-codex.git /tmp/codex-skill && \
mkdir -p .claude/skills && cp -r /tmp/codex-skill/.claude/skills/codex .claude/skills/codex && \
rm -rf /tmp/codex-skill

# Windows (PowerShell)
git clone --depth 1 https://github.com/sypsyp97/claude-skill-codex.git $env:TEMP\codex-skill; `
New-Item -ItemType Directory -Force -Path ".claude\skills"; `
Copy-Item -Recurse -Force "$env:TEMP\codex-skill\.claude\skills\codex" ".claude\skills\codex"; `
Remove-Item -Recurse -Force "$env:TEMP\codex-skill"

Verify: Check that ~/.claude/skills/codex/SKILL.md or .claude/skills/codex/SKILL.md exists. Claude Code will automatically discover it.

Usage

Simply mention Codex in your conversation with Claude Code:

Review my Python code for security issues using codex
Use codex to refactor this module to async/await
Analyze the architecture of this codebase with codex
Resume the last codex session and apply the suggested changes

Claude will automatically activate the skill, ask for preferences (model and reasoning effort), and execute the appropriate command.

Example:

codex exec -m gpt-5-codex \
  --config model_reasoning_effort="high" \
  --sandbox read-only \
  --full-auto \
  "Analyze this repository..." 2>/dev/null

Note: Thinking tokens (stderr) are suppressed by default. To see them for debugging, ask: "Show me the thinking tokens from codex"

Configuration Reference

Model Selection Guide

Task Type	Recommended Model	Reasoning Effort
Quick syntax fixes	gpt-5.2	minimal
Code review	gpt-5.2	medium
Refactoring	gpt-5.2-codex	medium
Architecture analysis	gpt-5.2	high
Security audit	gpt-5.2	high
Algorithm optimization	gpt-5.2-codex	high
Documentation generation	gpt-5.2	low

Sandbox Modes

• read-only: Analysis and documentation (default)
• workspace-write: Code modifications and file creation
• danger-full-access: System operations (rarely needed)

For complete details including workflows, CLI reference, error handling, and best practices, see SKILL.md.

Resources

• SKILL.md - Complete documentation with workflows and CLI reference
• GitHub Issues - Report bugs or request features
• Claude Code Skills - How skills work
• Codex CLI Reference - Codex documentation

Contributing

Contributions welcome! Fork the repository, edit .claude/skills/codex/SKILL.md, test locally, and submit a pull request.

License

See LICENSE for details.

Acknowledgments

Inspired by skills-directory/skill-codex with extensive enhancements for production use, including comprehensive CLI documentation, multi-platform support, workflow orchestration, advanced error handling, and detailed troubleshooting guides.