Developed a ChatGPT subscription model access feature for the BerriAI/litellm repository, enabling Pro and Max users to authenticate via the OAuth Device Flow. This work introduced a new messages endpoint and enhanced the responses bridge, allowing seamless integration with existing client workflows and supporting premium access through subscription-aware routing. The implementation focused on backend development and API design using Python, with unit testing to ensure reliability. Deployment artifacts were prepared for production rollout, emphasizing business value by enabling monetization paths and tighter workflow integration. The project demonstrated depth in OAuth authentication and backend systems within a one-month development period.