Codex CLI Guide

Codex CLI is OpenAI's terminal-based coding agent, similar to Claude Code but powered by GPT models.

Setup

# npm
npm install -g @openai/codex

# Homebrew
brew install --cask codex

# Or the official install script (macOS/Linux)
curl -fsSL https://chatgpt.com/codex/install.sh | sh

codex

Sign in with your ChatGPT account (Plus/Pro/Team plans include Codex usage), or authenticate with an API key via export OPENAI_API_KEY=sk-....

How It Works

Codex CLI reads your project structure, understands your codebase, and can:

• Generate and edit files across your project
• Run shell commands and interpret results
• Create git commits with meaningful messages
• Execute test suites and fix failures

Key Differences from Claude Code

* Codex CLI gained native MCP support (STDIO + streamable HTTP servers), configured via ~/.codex/config.toml or the codex mcp command. See developers.openai.com/codex/mcp.

Autonomy Levels

Codex CLI offers three approval modes (switch on the fly with /approvals):

• Read Only — chat or plan without making any changes
• Auto — reads, edits, and runs commands in the workspace automatically; asks for approval to touch files outside it or to make network calls
• Full Access — edits, runs commands, and makes network calls freely (best for disposable sandboxes, not production repos)

Best For

• Developers already in the OpenAI ecosystem
• Projects that benefit from the GPT-5.x-Codex models' strengths
• Teams wanting sandboxed-by-default execution