LangChain

LangChain is an open-source framework for building applications powered by large language models, created by Harrison Chase in 2022. The company behind the framework, LangChain Inc., has raised over $35 million and has built one of the most widely used AI development toolchains in the industry.

The LangChain framework provides abstractions for connecting LLMs to external data sources, tools, and APIs — enabling developers to build RAG (retrieval-augmented generation) systems, AI agents, chatbots, and complex AI workflows. Key products include LangChain (the core framework), LangGraph (for building stateful, multi-actor AI agent systems with cycles and human-in-the-loop), LangSmith (observability and testing platform for LLM applications), and LangServe (deployment framework).

LangChain has become the default starting point for many developers building AI applications, with a massive ecosystem of integrations spanning every major LLM provider, vector database, and data source. LangGraph has emerged as the leading framework for building production-grade AI agents with complex control flow. The company's open-source community includes hundreds of thousands of developers, and LangSmith serves enterprises that need monitoring, evaluation, and debugging tools for LLM applications in production.