At least ChatGPT is now aware that Codex exists. I have a chat, still in my history, from a few months ago, in which I asked for help wrangling npm to get @openai/codex working, and ChatGPT said:

> Important: Codex CLI no longer exists

> OpenAI discontinued the Codex model + CLI a while back. There is no official binary named codex in any current OpenAI npm packages. OpenAI’s current CLI tool is:

    npm install -g openai

The world knowledge of these models is not necessarily up to date :)

edit: I replayed the same prompt into current ChatGPT and it is less clueless now. Maybe OpenAI noticed that it was utterly dumb that GPT-5.whatever didn't believe that Codex existed and fine-tuned it.

>The world knowledge of these models is not necessarily up to date :)

It's amazing how this still needs to be said. Codex was released in April 2025. The initial GPT-5 and 5.1 still had a knowledge cutoff in late 2024. Like, what did you expect? Always beware the knowledge cutoff for LLMs (although recent releases have gotten much better with researching the web for updates before answering modern software topics).