ChatGPT Subscription as LLM

[whati001]

Feature request

Would it be possible to add support for ChatGPT subscriptions (Plus/Pro)?

Currently, the project only supports OpenAI API keys, but many users have a ChatGPT subscription rather than API access. LiteLLM — which I believe is the library used for LLM communication — appears to support this via its ChatGPT provider. The main difference is that it requires OAuth authentication rather than a simple API key.
Docs: https://docs.litellm.ai/docs/providers/chatgpt

Would this be worth exploring?

Motivation

Make PR Agent available for all ChatGPT subscription users.

[whati001]

Did some research on this, and we can use the ChatGPT subscription by simply setting the correct ENV vars, as stated here.

However, the current litellm version seems to have some issues to communicate properly with the "ChatGPT/Codex" backend. Here is the relevant (I guess so) issue: BerriAI/litellm#25394