LangChain

LangChain is one of the most popular open-source frameworks for building LLM applications, with components for models, prompts, retrieval, and tool calling, plus LangGraph for controllable stateful agents and LangSmith for tracing, evaluating, and monitoring production behavior, in Python and JavaScript. For teams turning LLMs into products.

• Open-source LLM app framework
• LangGraph agent orchestration
• LangSmith tracing and evals