LlamaIndex

LlamaIndex is a framework for building RAG apps — connecting LLMs to your own data. The core primitives are data connectors (loaders for PDFs, APIs, databases), indexes (vector, graph, keyword, composable), query engines, and chat engines. It supports many chunking strategies, hybrid search, re-ranking, and composition of multiple indexes. Think LangChain but narrower and more opinionated around retrieval over custom knowledge.