LangChain

The widely used framework for composing LLM applications with chains, tools, and agents.

LangChain is a foundational framework for building applications with LLMs, offering standardized interfaces for models, prompts, retrieval, tools, and memory. It underpins a large ecosystem including LangGraph (agent orchestration) and LangSmith (observability). While newer graph-based patterns have taken over complex agent workflows, LangChain remains a common entry point and integration layer.