LlamaIndex vs LangChain

LlamaIndex vs LangChain compares two Python toolkits for connecting large language models (LLMs) to private data. LlamaIndex (formerly GPT Index) focuses on retrieval-augmented generation pipelines: it offers graph-based indexes, automatic chunking, and query engines that choose between vector, keyword, or SQL retrieval at runtime. It ships evaluation modules and integrations with tracing and observability tools, plus a high-level query-engine API — index.as_query_engine().query() — for data-centric teams that need fast ingestion and search without deep prompt plumbing. LangChain provides a broader, Lego-style framework: loaders, embeddings, vector stores, chains, agents, and memory elements all fit together so developers can build not just RAGs, but multi-tool agents, streaming applications, and trackable cost-of-observability. LlamaIndex delivers reasonable production speed for search-intensive use cases; LangChain provides fine-grained control, broader integration, and easier model swapping (GPT-4o today, Claude tomorrow). Many developers combine the two: LlamaIndex handles intelligent indexing, while LangChain orchestrates prompts, agents, and application endpoints, bringing together the best of both worlds for enterprise AI.

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