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LangChain

4.3
Freemium — from $39/mo

The most popular framework for building LLM-powered applications with chains, agents, and retrieval-augmented generation. Includes LangSmith for debugging and LangServe for deployment.

Key Features

  • LLM application framework
  • RAG pipeline building
  • Agent and tool integration
  • LangSmith debugging platform
  • LangServe deployment

Pros

  • + Most popular LLM framework
  • + Extensive integration library
  • + Active development community

Cons

  • Can be over-engineered for simple tasks
  • Rapid API changes
framework LLM apps RAG agents open-source