LangChain is the dominant open-source framework for composing LLM applications using chains, agents, and retrieval-augmented generation. The core library is free; the commercial offering is LangSmith, an observability and evaluation platform for LLM apps. LangGraph (part of the ecosystem) enables stateful, multi-actor agent workflows. Used by developers and AI teams to build production-grade LLM pipelines. Key features: - Open-source framework for chains, agents, and RAG pipelines - LangSmith: tracing, evaluation, and prompt versioning for LLM apps - LangGraph: stateful multi-agent workflow orchestration - Integrations with 100+ LLM providers, vector stores, and tools - LangGraph Cloud for hosted agent compute deployments
LangChain framework: free and open-source. LangSmith: Free tier (5,000 traces/month), Plus at $39/user/month (100,000 traces), Enterprise custom pricing. LangGraph Cloud from ~$35/month.