LightRAG is a production-ready Retrieval-Augmented Generation (RAG) framework that combines knowledge graph construction with vector-based retrieval. The system implements a dual-layer architecture managing both knowledge graphs (entities, relationships) and vector embeddings, enabling both local (entity-focused) and global (theme-focused) query modes plus hybrid combinations. It provides a FastAPI-based REST server with an embedded React WebUI, supporting 10+ LLM providers (OpenAI, Azure, Anthropic, Gemini, Ollama, Bedrock, etc.), 8+ vector/graph storage backends (PostgreSQL+pgvector/AGE, Neo4j, Milvus, Qdrant, Redis, MongoDB, OpenSearch, FAISS, NanoVectorDB), and a multimodal document parsing pipeline integrating MinerU and Docling for PDF/Office documents with tables, equations, and images. The codebase demonstrates strong engineering practices: async-first architecture with configurable concurrency controls, role-specific LLM configuration (EXTRACT, QUERY, KEYWORDS, VLM), atomic file operations for crash-safe persistence, comprehensive test coverage (300+ tests), and production deployment artifacts (Docker, Kubernetes/Helm, systemd). The parser layer is particularly well-designed with a registry-based engine dispatch (native docx/markdown, MinerU, Docling) producing a unified sidecar format. Recent additions include reranking support, asymmetric embeddings, document deletion with KG regeneration, and RAGAS/Langfuse integration for evaluation and observability.
LlamaIndex is a comprehensive Python framework designed for building Large Language Model (LLM) applications, with a primary focus on Retrieval-Augmented Generation (RAG) and agentic workflows. It functions as a modular library rather than a monolithic application, providing abstractions for data ingestion, indexing, retrieval, and query orchestration. The architecture is split between a core package (`llama-index-core`) containing base interfaces and logic, and a vast ecosystem of integration packages (`llama-index-integrations`) that connect to external LLM providers, vector databases, and data sources. The codebase demonstrates a strong plugin-based design, allowing developers to swap components like embeddings, retrievers, and LLMs without rewriting the core orchestration logic.
LeanRAG is a Retrieval-Augmented Generation (RAG) framework that leverages knowledge graph structures with semantic aggregation and hierarchical retrieval to generate context-aware, concise, and high-fidelity responses. The system processes documents through a pipeline: chunking, LLM-based triple extraction, hierarchical graph construction with clustering, and structure-guided retrieval from fine-grained entities upward through the graph to reduce redundancy and improve evidence quality. It targets question-answering tasks across domains (general, CS, legal, agriculture) and uses LLMs (OpenAI, Qwen, DeepSeek) for extraction and generation, with Milvus for vector search and MySQL for storing graph entities, relations, and communities. Evaluation is performed via an external LLM API scoring answers on comprehensiveness, empowerment, diversity, and overall quality.