Codex CLI: OpenAI revives the Codex name with an open-source terminal coding agent
In one sentence Alongside o3/o4-mini, OpenAI ships Codex CLI: an open-source terminal coding agent (Apache 2.0), direct response to Anthropic's Claude Code and Aider.
OpenAI pulls the "Codex" name out of storage (it was the model powering GitHub Copilot in 2021-2023) and applies it to a new tool: a CLI for AI coding directly from the terminal.
How it works: in the terminal you type codex and describe what you want ("add tests for the foo function", "refactor this file in TypeScript"). The AI reads the project files, proposes changes, applies them if you approve, runs tests.
Key differences:
- it's open source (Apache 2.0) — anyone can fork and modify;
- specifically optimized for OpenAI models (o3, o4-mini, GPT-4.1), but supports other providers via config.
It's the direct answer to Anthropic's Claude Code, launched February 2025. Google is moving in the same direction with Jules and Gemini Code Assist.
Companies
OpenAI
Tools
Codex CLI
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