LangChain

LangChain is the most widely adopted open source framework for building applications powered by large language models. Since its release in late 2022, it has become the default starting point for many developers building AI applications, chatbots, RAG (Retrieval-Augmented Generation) systems, and AI agents.

The core abstraction in LangChain is chains, which are composable sequences of operations that can combine LLM calls, data retrieval, tool use, and other actions. This composability allows developers to build complex AI workflows from reusable components rather than writing everything from scratch. A typical RAG application, for example, chains document loading, embedding generation, vector storage, retrieval, and LLM generation into a coherent pipeline.

LangChain integrates with virtually every major LLM provider including OpenAI, Anthropic, Google, Hugging Face, and others, and with vector databases, document loaders, and external tools. This breadth of integration means developers can switch providers or add new data sources without rewriting their application architecture.

LangGraph, an extension for building stateful multi-actor applications, enables more complex agent workflows where multiple AI agents collaborate on tasks with memory and persistent state. This has become increasingly relevant as agent-based AI applications have grown in popularity.

LangSmith, LangChain's observability and evaluation platform, helps developers debug, test, and monitor LLM applications in production. Understanding why an LLM application gave a particular response, or why it failed, is significantly harder than debugging traditional software, and LangSmith addresses this.