LangChain
Most widely used framework for building LLM applications. Chains, agents, RAG pipelines, and deep integrations with 300+ tools.
RAGFlow
Open-source RAG engine built on deep document understanding — handles tables, figures, and complex layouts in PDFs that chunk-based RAG misses. Includes a visual DAG pipeline editor for building extraction and retrieval workflows. One of the fastest-growing RAG projects of 2025 with 40K+ GitHub stars.