LlamaIndex

LlamaIndex is the go-to framework for connecting your own data to large language models. It provides data connectors (LlamaHub) for ingesting from PDFs, databases, APIs, Notion, Slack, and hundreds of other sources. The indexing layer chunks, embeds, and stores your data in any vector database. Query engines handle retrieval-augmented generation with support for recursive retrieval, sub-question decomposition, and multi-document synthesis. It also includes an agent framework with tool use and multi-step reasoning. Available in both Python and TypeScript (LlamaIndex.TS). If your use case is primarily about making LLMs smarter with your own data rather than building autonomous agents, LlamaIndex is more focused and mature than LangChain for that specific problem.