OpenAI API
API access to GPT-5, GPT-5.5, o3/o4 reasoning models, and the Responses API; plus embeddings, image, audio, and Realtime endpoints. The most widely deployed LLM API in production.
LightRAG
RAG framework that builds a knowledge graph from documents, enabling retrieval at both local (specific facts) and global (thematic) levels. Outperforms naive RAG on complex questions requiring reasoning across multiple document sections. EMNLP 2025.