OpenAI Open Sources Codex: The CLI Coding Agent

Codeex: OpenAI’s open source CLI coding assistant explained

OpenAI recently released Codeex, a lightweight command-line coding assistant that runs directly in your terminal. If the name sounds familiar, that’s because Codeex was originally introduced back in 2021 as an AI system that translated natural language to code. This new CLI tool appears to be OpenAI’s response to Anthropic’s recently released Claude Code.

What is Codeex?

Codeex is a terminal-based coding assistant that lets you make changes to your codebase using natural language commands. It’s not powered by a new model—instead, it leverages existing models like GPT-3.5 (03) or GPT-4 Mini (04 mini) under the hood.

The key difference between Codeex and other AI coding tools is that it’s fully open source, which should lead to rapid community improvements over time.

How to get started

Getting Codeex up and running is straightforward:

• Install Codeex via npm (requires Node.js version 22 or higher)
• Get an OpenAI API key
• Set up your API key in the terminal
• Run the “codeex” command in your project directory

By default, Codeex uses GPT-4 Mini, but you can specify other models like GPT-3.5