Codex – the OpenAI answer to Claude Desktop?

What Is OpenAI Codex CLI?

OpenAI Codex CLI is a command-line tool that brings AI-powered coding assistance directly to your terminal. Unlike chatbot interfaces or IDE plugins, Codex CLI operates as an agent that can read your codebase, make edits, run commands, and complete tasks based on your natural language instructions.

The tool launched as an open-source project on GitHub, which means developers can inspect the code, contribute improvements, and customize it for their workflows. It runs on Node.js and connects to OpenAI’s API to process requests using models like o4-mini and GPT-4.1.

Codex CLI sits in a growing category of terminal-based AI agents. GitHub Copilot focuses on inline code suggestions within your editor. ChatGPT offers conversational help but operates in a separate browser window. Codex CLI takes a different approach: it lives in your terminal, has direct access to your filesystem, and can execute code in a sandboxed environment.

The name “Codex” comes from OpenAI’s earlier Codex model, which was trained on public code repositories and powered the original GitHub Copilot. The CLI tool builds on that heritage but uses newer, more capable models designed for agentic coding tasks.

Codex CLI vs Claude Code: Key Differences

The most direct comparison for Codex CLI is Claude Code, Anthropic’s own terminal-based coding agent. Both tools operate in similar ways, but they differ in important details.

• Model access: Codex CLI uses OpenAI models (o4-mini, GPT-4.1) while Claude Code uses Anthropic’s Claude models (Sonnet, Opus)
• Pricing structure: Codex CLI works with ChatGPT subscriptions (Plus, Pro, Business, Edu, Enterprise) or API keys with pay-per-token billing. Claude Code offers similar API-based pricing or bundles with Claude Pro/Max subscriptions
• Approval modes: Codex CLI provides three modes (suggest, auto-edit, full-auto) that control how much autonomy the agent has
• Sandboxing: Codex CLI runs code in sandboxed environments by default, adding a security layer that limits file system access
• Open source: Codex CLI is open source, while Claude Code is proprietary
• Context files: Both tools support project-specific configuration files to help the AI understand your codebase better

Claude Code has a reputation for handling longer, more complex tasks and producing cleaner code in many developer surveys. Codex CLI benefits from OpenAI’s strong platform integration and the flexibility of multiple model choices. The right tool depends on your existing subscriptions, preferred models, and specific workflow needs.

How to Install and Set Up Codex CLI

Getting Codex CLI running takes just a few steps. You need Node.js version 18 or later installed on your system, plus an OpenAI API key with available credits.

Step 1: Install Node.js from nodejs.org if you do not already have it. Version 18 or newer is required.

Step 2: Open your terminal and run the global install command using npm or Homebrew:

npm install -g @openai/codex
# Or on macOS with Homebrew:
brew install --cask codex

Step 3: Sign in with your ChatGPT account by running codex and selecting “Sign in with ChatGPT.” This works with Plus, Pro, Business, Edu, and Enterprise plans. Alternatively, set your API key as an environment variable. Add this line to your shell profile (~/.bashrc, ~/.zshrc, or equivalent):

export OPENAI_API_KEY=your-api-key-here

Step 4: Go to any project directory and start Codex CLI by running:

codex

Step 5: Test it with a simple request like “explain what this project does” or “find any bugs in the main entry point.”

On macOS and Linux, the process is straightforward. Windows users can follow the same steps through PowerShell or Windows Subsystem for Linux (WSL). The tool installs globally through npm, so it works in any directory once set up.

Features and Capabilities of Codex CLI

Codex CLI offers several features that distinguish it from simpler AI coding tools.

Approval Modes

The tool ships with three approval modes that control how much independence the agent has:

Suggest mode shows you proposed changes and waits for your approval before making any edits. This is the safest option and works well when you are learning the tool or working on critical code.

Auto-edit mode makes file changes automatically but still asks before running commands. This strikes a balance between speed and safety for routine refactoring tasks.

Full-auto mode (sometimes called YOLO mode) lets the agent make edits and run commands without asking. Use this only when you trust the task and have backups of your work.

Sandboxed Execution

One of Codex CLI’s standout features is its sandboxed environment. When the agent runs code, it does so in an isolated container that limits access to your broader file system and network. This reduces the risk of accidental damage from automated code execution.

The sandbox approach differs from some competitors that execute commands directly in your terminal without isolation. For teams working with sensitive data or production-adjacent systems, this added layer of protection matters.

Multi-Agent Architecture

Codex CLI can spawn multiple subagents that work on different parts of a task simultaneously. For example, if you ask it to refactor a large module, it might split the work across several agents that handle different files in parallel. This parallel processing can speed up complex tasks significantly.

Git Integration

The tool integrates naturally with Git workflows. It can generate commit messages, create pull request descriptions, and help resolve merge conflicts. Since it runs in your terminal, it has direct access to your Git history and can reference past commits when making suggestions.

MCP Server Support

Codex CLI supports the Model Context Protocol (MCP), which lets you connect it to external tools and data sources. Through MCP servers, the agent can access databases, APIs, documentation, and other resources that extend its capabilities beyond what is in your local codebase.

Pricing and Subscription Requirements

Codex CLI itself is free to install and use, but it needs either a ChatGPT subscription or an OpenAI API key to function. Your costs depend on which option you choose and how much you use the tool.

If you already have a ChatGPT Plus, Pro, Business, Edu, or Enterprise plan, you can sign in directly and start using Codex CLI without setting up an API key. This is the simplest path for most developers and keeps billing consolidated under your existing subscription.

Alternatively, you can use an OpenAI API key with pay-per-token billing. The default model is o4-mini, which offers a good balance of capability and cost. For more complex tasks, you can switch to GPT-4.1 or other available models.

Compared to Claude Code, which can be accessed through a Claude Pro subscription at $20 per month, Codex CLI’s pricing is competitive. ChatGPT Plus costs $20 per month and now includes Codex CLI access, making it a direct alternative. API-based usage varies, but light users often spend under $10 per month.

When to Choose Codex CLI Over Claude Code

Both tools are capable, but certain situations favor one over the other.

Choose Codex CLI if:

• You prefer open-source tools and want to inspect or modify the source code
• Your workflow already relies on OpenAI’s API and models
• You need sandboxed code execution for security reasons
• You want fine-grained control over which model handles your requests
• You work in a team environment where standardized AI tooling matters

Consider Claude Code if:

• You prefer Anthropic’s models for code quality and reasoning
• You want subscription-based pricing with predictable monthly costs
• You need strong performance on very long context windows
• Your development workflow centers around Claude’s platform

Many developers end up using both tools for different purposes. Codex CLI might handle quick terminal tasks and CI/CD integration, while Claude Code tackles larger refactoring projects. There is no rule that says you must pick one.

Frequently Asked Questions