Codex CLI
Codex CLI, an open-source (Apache 2.0) terminal coding agent, gives OpenAI a Claude Code competitor.
Lightweight local agent that wraps OpenAI models to read a repo, run commands and apply patches under approval policies, with macOS sandboxing via sandbox-exec. Released alongside o3 and o4-mini; later became the base of the Codex app, IDE extension and open agent harness.
- Date
- Wednesday, 16 April 2025
- Lab
- OpenAI
- Kind
- product
- Access
- open weights
- Price
- free; pay for model usage via API or ChatGPT plan
"access" refers to the open-source tool, not model weights. The GitHub repository page itself was not opened; details come from Simon Willison's inspection of the repo and OpenAI's Codex post, which says Codex CLI launched a month before 2025-05-16. Anthropic's Claude Code preceded it (2025-02).
Sources
- simonwillison.net/2025/Apr/16/openai-codex/
- openai.com/index/introducing-codex/
- developers.openai.com/api/docs/changelog
This record was checked against its sources on 6 October 2026. How we check