OpenAI Codex CLI

OpenAI Codex CLI is a lightweight coding agent that runs locally on your computer, providing AI-powered assistance directly in your terminal. It's part of OpenAI's suite of developer tools and integrates with your ChatGPT plan for seamless usage.

What is Codex CLI?

Codex CLI is a command-line interface that brings AI-powered coding assistance to your terminal. Unlike cloud-based solutions, Codex CLI runs locally on your machine, providing fast and private coding assistance without sending your code to external servers.

Key Features

Local Execution: Runs entirely on your local machine
Terminal Integration: Works directly in your command line
ChatGPT Integration: Uses your existing ChatGPT plan
Model Context Protocol (MCP): Supports MCP servers for extended functionality
Zero Data Retention (ZDR): Option for enhanced privacy
Multi-Platform: Available for macOS, Linux, and Windows
Sandbox & Approvals: Safe execution environment with user approval

Installation

Using Package Managers

npm (Node.js):

npm install -g @openai/codex

Homebrew (macOS):

brew install codex

Manual Installation

Download the appropriate binary from the GitHub Releases:

macOS:

Apple Silicon (arm64): codex-aarch64-apple-darwin.tar.gz
Intel (x86_64): codex-x86_64-apple-darwin.tar.gz

Linux:

x86_64: codex-x86_64-unknown-linux-musl.tar.gz
arm64: codex-aarch64-unknown-linux-musl.tar.gz

Windows:

x86_64: codex-x86_64-pc-windows-msvc.zip

After downloading, extract and rename the binary to codex:

# Extract the archive
tar -xzf codex-aarch64-apple-darwin.tar.gz

# Rename to codex
mv codex-aarch64-apple-darwin codex

# Make executable
chmod +x codex

# Move to PATH (optional)
sudo mv codex /usr/local/bin/

Getting Started

1. Initial Setup

Run Codex CLI for the first time:

codex

2. Authentication

Sign in with ChatGPT (Recommended):

Select "Sign in with ChatGPT" when prompted
Use your existing ChatGPT Plus, Pro, Team, Edu, or Enterprise plan
No additional API key setup required

API Key Authentication:

Use your OpenAI API key for usage-based billing
Configure in ~/.codex/config.toml

3. Basic Usage

# Start interactive session
codex

# Run with a specific prompt
codex "Create a Python script to parse CSV files"

# Run with file input
codex --file script.py "Optimize this code for performance"

Configuration

Codex CLI stores configuration in ~/.codex/config.toml:

# Basic configuration
[general]
model = "gpt-4"
temperature = 0.1
max_tokens = 4000

# Authentication
[auth]
provider = "chatgpt"  # or "openai"

# MCP Servers
[mcp_servers]
# Add your MCP server configurations here

# Sandbox settings
[sandbox]
enabled = true
auto_approve = false

Configuration Options

Option	Description	Default
`model`	AI model to use	`gpt-4`
`temperature`	Response randomness (0-1)	`0.1`
`max_tokens`	Maximum response length	`4000`
`provider`	Authentication provider	`chatgpt`
`sandbox.enabled`	Enable sandbox mode	`true`
`sandbox.auto_approve`	Auto-approve safe operations	`false`

Core Features

1. Interactive Coding

# Start interactive session
codex

# Example conversation:
# You: Create a REST API in Python using FastAPI
# Codex: I'll create a FastAPI REST API for you...
# [Codex generates code and files]

2. File Operations

# Analyze existing code
codex --file app.py "Review this code and suggest improvements"

# Generate new files
codex "Create a Dockerfile for a Node.js application"

# Refactor code
codex --file utils.py "Refactor this code to use async/await"

3. Project Management

# Initialize new project
codex "Set up a new React project with TypeScript and Tailwind CSS"

# Add features to existing project
codex "Add authentication to this Express.js application"

# Debug issues
codex --file error.log "Help me debug this application error"

4. Documentation Generation

# Generate README
codex "Create a comprehensive README for this project"

# Add code comments
codex --file main.py "Add detailed docstrings to all functions"

# Create API documentation
codex "Generate OpenAPI documentation for this FastAPI app"

Model Context Protocol (MCP)

Codex CLI supports MCP servers for extended functionality:

# ~/.codex/config.toml
[mcp_servers.filesystem]
command = "npx"
args = ["-y", "@modelcontextprotocol/server-filesystem", "/path/to/allowed/directory"]

[mcp_servers.git]
command = "npx"
args = ["-y", "@modelcontextprotocol/server-git", "--repository", "/path/to/repo"]

Available MCP Servers

Filesystem: File and directory operations
Git: Git repository management
Database: Database querying and management
Web: Web scraping and API interactions
Custom: Your own MCP servers

Sandbox & Security

Sandbox Mode

Codex CLI includes a sandbox environment for safe code execution:

# Enable sandbox mode
codex --sandbox

# Auto-approve safe operations
codex --auto-approve

Approval System

Safe Operations: Automatically approved (file reading, code analysis)
Moderate Risk: Requires approval (file creation, package installation)
High Risk: Always requires explicit approval (system commands, network access)

Zero Data Retention (ZDR)

For enhanced privacy, enable ZDR mode:

codex --zdr

This ensures your data is not retained by OpenAI.

Advanced Usage

1. Non-Interactive Mode

# CI/CD integration
codex --non-interactive "Generate unit tests for this function"

# Batch processing
echo "Create a Python class for user management" | codex

2. Verbose Logging

# Enable detailed logging
codex --verbose "Debug this application"

# Trace mode for development
codex --trace "Analyze this codebase"

3. Custom Prompts

# Use custom system prompt
codex --system-prompt "You are a senior Python developer" "Review this code"

# Load prompt from file
codex --prompt-file prompts/code-review.txt --file app.py

Integration Examples

1. VS Code Integration

// .vscode/tasks.json
{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "Codex: Code Review",
      "type": "shell",
      "command": "codex",
      "args": [
        "--file",
        "${file}",
        "Review this code and suggest improvements"
      ],
      "group": "build"
    }
  ]
}

2. Git Hooks

#!/bin/sh
# .git/hooks/pre-commit
codex --non-interactive "Review the staged changes and ensure code quality"

3. CI/CD Pipeline

# .github/workflows/codex-review.yml
name: Codex Code Review
on: [pull_request]
jobs:
  review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Install Codex CLI
        run: npm install -g @openai/codex
      - name: Code Review
        run: codex --non-interactive "Review the changes in this PR"

Best Practices

1. Security

Use sandbox mode for untrusted code
Review generated code before execution
Keep API keys secure
Use ZDR mode for sensitive projects

2. Performance

Use specific prompts for better results
Break large tasks into smaller chunks
Cache frequently used configurations
Monitor token usage

3. Collaboration

Document your Codex workflows
Share useful prompts with your team
Use consistent configuration across projects
Integrate with your existing development tools

Troubleshooting

Common Issues

Authentication Problems:

# Clear authentication cache
rm -rf ~/.codex/auth

# Re-authenticate
codex --login

Permission Errors:

# Fix binary permissions
chmod +x codex

# Check PATH
which codex

Network Issues:

# Test connectivity
codex --test-connection

# Use proxy
codex --proxy http://proxy.company.com:8080

Debug Mode

# Enable debug logging
codex --debug "Your prompt here"

# Check configuration
codex --config-check

# Validate installation
codex --validate

Comparison with Other Tools

Feature	Codex CLI	GitHub Copilot	ChatGPT Web	Cursor
Environment	Terminal	IDE	Browser	IDE
Privacy	Local + ZDR	Cloud	Cloud	Local + Cloud
Cost	ChatGPT Plan	Subscription	Subscription	Subscription
Customization	High	Medium	Low	High
Integration	CLI Tools	IDE Only	Browser Only	IDE Only
Offline	Partial	No	No	Partial

When to Use Codex CLI

Choose Codex CLI when:

You prefer terminal-based workflows
You need local execution for privacy
You want to integrate with CLI tools and scripts
You're working with multiple programming languages
You need custom automation and workflows
You want to use your existing ChatGPT plan

Consider alternatives when:

You primarily work in IDEs
You need real-time code completion
You prefer GUI-based interactions
You need offline-only functionality

Resources

GitHub Repository: github.com/openai/codex
Documentation: docs.openai.com/codex
ChatGPT Integration: chatgpt.com/codex
MCP Documentation: modelcontextprotocol.io
Community: GitHub Discussions and Issues

Contributing

Codex CLI is open source and welcomes contributions:

Fork the repository
Create a feature branch
Make your changes
Add tests if applicable
Submit a pull request

See the Contributing Guide for detailed instructions.

What is Codex CLI?​

Key Features​

Installation​

Using Package Managers​

Manual Installation​

Getting Started​

1. Initial Setup​

2. Authentication​

3. Basic Usage​

Configuration​

Configuration Options​

Core Features​

1. Interactive Coding​

2. File Operations​

3. Project Management​

4. Documentation Generation​

Model Context Protocol (MCP)​

Available MCP Servers​

Sandbox & Security​

Sandbox Mode​

Approval System​

Zero Data Retention (ZDR)​

Advanced Usage​

1. Non-Interactive Mode​

2. Verbose Logging​

3. Custom Prompts​

Integration Examples​

1. VS Code Integration​

2. Git Hooks​

3. CI/CD Pipeline​

Best Practices​

1. Security​

2. Performance​

3. Collaboration​

Troubleshooting​

Common Issues​

Debug Mode​

Comparison with Other Tools​

When to Use Codex CLI​

Resources​

Contributing​