LangChain / LangSmith

LangChain is a leading open-source framework for building LLM applications and agents (including via LangGraph), and LangSmith is its commercial platform for tracing, evaluation, and observability. The frameworks are free and the company monetizes primarily through LangSmith. LangSmith works with LangChain apps and non-LangChain apps alike.

LangChain is one of the most widely used open-source frameworks for building applications on top of large language models. It provides abstractions and components for chaining LLM calls, connecting to data sources and tools, managing memory, and, increasingly, building agentic workflows (including via its LangGraph library for stateful, multi-step agents). The framework is available in Python and JavaScript and integrates with virtually every major model provider, vector database, and tool. LangSmith is the company's commercial platform that complements the framework, focused on the production side of LLM development: tracing and debugging chains and agents, evaluating outputs against datasets, monitoring quality and cost, and managing prompts. It works with LangChain apps but also with applications that do not use the framework, positioning LangSmith as a general-purpose LLM observability and evaluation layer. The open-source frameworks are free (MIT-licensed), while LangSmith is the primary monetization path, with a free developer tier and paid per-seat plans plus usage-based tracing. LangChain the company has become one of the better-funded players in the LLM tooling space and competes with observability tools like Langfuse as well as broader agent frameworks.