Support gpt5 models

[matthewdva]

GPT-5 models changed how they respond. They no longer react with simple JSON. As such, the plugin does not work with GPT-5 models.

Source

We’re introducing new features in our API to give developers more control over model responses. GPT‑5 supports a new verbosity parameter (values: low, medium, high) to help control whether answers are short and to the point or long and comprehensive. GPT‑5’s reasoning_effort parameter can now take a minimal value to get answers back faster, without extensive reasoning first. We’ve also added a new tool type—custom tools—to let GPT‑5 call tools with plaintext instead of JSON. Custom tools support constraining by developer-supplied context-free grammars.

We’re releasing GPT‑5 in three sizes in the API—gpt-5, gpt-5-mini, and gpt-5-nano—to give developers more flexibility to trade off performance, cost, and latency. While GPT‑5 in ChatGPT is a system of reasoning, non-reasoning, and router models, GPT‑5 in the API platform is the reasoning model that powers maximum performance in ChatGPT. Notably, GPT‑5 with minimal reasoning is a different model than the non-reasoning model in ChatGPT, and is better tuned for developers.

[stadlaa]

I would like to use them too!