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LangChain vs LlamaIndex vs Haystack (2026): AI Framework Comparison

Building LLM applications requires a framework to manage prompts, chains, retrieval, and agent orchestration. In 2026, three frameworks dominate: LangChain (the most popular, general-purpose), LlamaIndex (specialized in data indexing and RAG), and Haystack (NLP pipelines, from deepset). Choosing the right one depends on whether you are building agents, search systems, or document processing pipelines.

Quick Comparison

Feature LangChain LlamaIndex Haystack

Focus General-purpose LLM app framework Data indexing + retrieval (RAG) NLP pipelines (search, QA, extraction)

Language Python, TypeScript Python, TypeScript Python

Core Concept Chains + Agents + Tools Indexes + Query Engines + Agents Pipelines + Components + Document Stores

RAG Quality Good (LCEL + retrievers) Excellent…