The API has a specific alias for the ChatGPT models i.e. chatgpt-4o-latest
Registered API users of reasoning models can also gain access to the thinking process for o3 and o4-mini models, with a temp of around 0.7 to 1 and function calling enabled you can allow the model to act like ChatGPT fairly effectively. It’s a lesson for the reader to implement the other niceties such as Canvas and search, etc, but that can all be done with function calling and custom code.