Simon Willison publishes llm-openai-via-codex, a tool letting developers use OpenAI's language models through GitHub Copilot's Codex API instead of the official OpenAI endpoint

Simon Willison, a developer and AI researcher, released llm-openai-via-codex 0.1a0 — a plugin that reroutes OpenAI language model requests through GitHub's Codex API rather than OpenAI's standard API. This allows users to access OpenAI's models using different authentication or billing methods tied to GitHub.

Instead of calling OpenAI's official endpoint directly, this tool intercepts requests and sends them through Codex — GitHub's code-generation AI service. For users already paying for GitHub Copilot or with Codex access, this sidestep eliminates the need for a separate OpenAI API key and billing account.

Developers who want to use OpenAI models but lack an OpenAI API account, face API rate limits, or prefer consolidated billing through GitHub now have an alternative path. This is especially useful for teams already integrated into GitHub's ecosystem who want to experiment with LLMs (AI systems that understand and generate text) without managing another vendor relationship.

The code is open-source and available via Python package manager; users can install it directly, but the 0.1a0 version label signals this is early experimental software not yet production-ready.