edit: There is a gpt-5.3 model, but selecting that gives me the error:
Error The model `gpt-5.3` does not exist or you do not have access to it. Provider: openai
I don't see a 5.3-codex, and no opus 4.6...
- you can have models you can not actually use (that gpt-5.3 response) - you can have model non-listed.
Those are all coming from the provider with your API_KEY.