LangChain

LangChain is a widely used developer framework for building applications and agents on top of large language models, along with LangSmith for observability and evaluation and LangGraph for agent orchestration. It helped define the tooling layer that sits between models and applications, and its open-source libraries are among the most adopted in the AI developer ecosystem.

LangChain began in 2022 as an open-source library that made it easier to chain LLM calls with tools, memory, and external data, quickly becoming a default starting point for developers building on top of models. Its rapid adoption reflected how much scaffolding early LLM applications required.

The company built a commercial layer around the open source: LangSmith for tracing, debugging, evaluation, and monitoring of LLM apps in production, and LangGraph for building stateful, multi-step agents. This observability and orchestration focus addresses the reliability challenges of moving from prototype to production.

Backed by prominent venture investors, LangChain competes with LlamaIndex, framework offerings from model providers, and a broad field of agent-building tools. Its position in the middleware layer keeps it close to how developers actually assemble AI systems, independent of which underlying model they choose.