OpenAI Codex CLI — Terminal Coding Agent by OpenAI

Core Features

Three Approval Modes

codex --mode auto "Refactor the database layer to use connection pooling"

Sandbox Execution

Commands run in a sandboxed environment by default:

• Network access disabled
• File system restricted to project directory
• Configurable permissions

Multi-Model Support

# Use different models
codex --model o4-mini "Quick fix for the typo in README"
codex --model o3 "Design and implement a caching layer"
codex --model gpt-4o "Explain the authentication flow"

Context-Aware

Codex reads your project structure, git history, and relevant files to understand context before making changes.

Typical Workflow

# Navigate to your project
cd my-app

# Ask Codex to help
codex "The login endpoint returns 500 when the email has uppercase letters"

# Codex:
# 1. Reads relevant files (auth/login.ts, models/user.ts)
# 2. Identifies the case-sensitivity bug
# 3. Proposes a fix
# 4. Shows diff for approval
# 5. Applies the change
# 6. Runs tests to verify

Configuration

# ~/.codex/config.yaml
model: o4-mini
mode: auto-edit
approval:
  file_edits: auto
  commands: manual
context:
  max_files: 50
  include_git_diff: true

Key Stats

• 20,000+ GitHub stars
• Official OpenAI product
• 3 approval modes
• Sandboxed execution
• Multi-model support (o4-mini, o3, GPT-4o)

FAQ

Q: What is OpenAI Codex CLI? A: The official OpenAI terminal coding agent that reads your codebase, writes code, runs commands, and manages files from the command line.

Q: Is Codex CLI free? A: The CLI is open-source. You need an OpenAI API key with usage-based billing.

Q: How does Codex CLI compare to Claude Code? A: Both are terminal coding agents. Codex uses OpenAI models (o4-mini, o3), Claude Code uses Claude models. Core functionality is similar — code editing, command execution, and project context awareness.