LangChain

LangChain is an open-source framework that provides the building blocks for developers to create LLM-powered applications: chains that link prompts and model calls, agents that can use tools and make decisions, and retrieval systems that connect models to external data sources. It abstracts the complexity of prompt management, memory, tool calling, and multi-step reasoning. AI engineers building internal chatbots, document Q&A systems, autonomous research agents, and code review tools use LangChain to avoid reinventing common patterns. The framework supports every major LLM provider and comes with hundreds of integrations for data sources, vector stores, and external tools. LangChain has become the default starting point for production AI application development, with over 90,000 GitHub stars and a large ecosystem of third-party integrations. LangSmith provides the observability layer for debugging and monitoring LangChain applications in production.