LangChain

What is LangChain?

LangChain is an open-source framework for building applications and agents on top of LLMs. It provides the building blocks — model and tool abstractions, retrieval, memory — and, via LangGraph, a way to build stateful, controllable multi-step and multi-agent systems. LangSmith is its paid observability/eval layer.

What does LangChain do?

Developers use LangChain’s components to wire models to tools, data and memory, then use LangGraph to define the agent’s control flow as a graph — enabling loops, branching, human-in-the-loop and multiple coordinated agents. LangSmith adds tracing, evaluation and monitoring for production.

Key features

• Rich integrations — A large ecosystem of model, vector-store and tool integrations.
• LangGraph — Graph-based control for stateful, multi-step and multi-agent workflows.
• LangSmith observability — Tracing, evals and monitoring for agents in production (paid).

What are LangChain's use cases?

• Build a custom agent — A team composes retrieval, tools and control flow into a bespoke production agent.
• Multi-agent systems — Coordinate several agents with LangGraph’s stateful graph.

Why use LangChain?

• The largest ecosystem and integration surface in the space.
• LangGraph gives real control over agent state and flow.
• Open-source and self-hostable; pay only for LangSmith if you want it.

Pros & cons

LangChain pricing

• Open sourceFree
• LangSmithFreemium

See current pricing on langchain.com ↗Compare LangChain alternatives →