This repository is a full-stack, multi-tenant AI API gateway platform (named 'sub2api') that proxies requests to a wide range of AI model providers including OpenAI, Anthropic, Gemini, Grok, DeepSeek, and many others. It provides authentication (JWT, OAuth, API keys), rate limiting, token-level billing, subscription management, user and admin management, payment processing (Alipay, WeChat Pay, Stripe, Airwallex, EasyPay), content moderation, channel monitoring, and operational dashboards. The backend is written in Go using the Gin framework and Ent ORM, with PostgreSQL and Redis for data storage and caching. The frontend is built with Vue 3, TypeScript, and Pinia stores, offering both admin and user interfaces. The system is designed for production deployment with Docker, includes extensive unit and integration tests, and supports a plugin architecture for extensible OAuth transport. Despite its large codebase and many features, the architecture follows a clear service-repository pattern with well-isolated packages, making it a solid example of a complex API gateway implementation.