LangChain
Open-source framework plus LangGraph and LangSmith for building, orchestrating, and observing LLM agents
Freemium
About LangChain
LangChain is the open-source framework and commercial platform for building LLM applications and AI agents. The core libraries (Python and TypeScript) handle prompts, models, tools, and retrieval. LangGraph adds low-level orchestration for stateful, long-running agents that survive restarts and support human-in-the-loop control. LangSmith is the platform layer for tracing, evaluation, prompt management, and deployment. Together they cover the full path from prototype to production-monitored agents.
Key Features
- Open-source LangChain core libraries in Python and TypeScript
- LangGraph orchestration for stateful, durable, long-running agents
- LangSmith tracing and observability into every agent step
- Built-in and custom evaluations to score and improve agents
- Hundreds of integrations for models, vector stores, and tools
- Managed deployment plus human-in-the-loop and Fleet agent runs
Pros & Cons
What we like
- Open-source core is free and framework-agnostic via LangSmith SDKs
- Largest integration ecosystem across models and data sources
- LangGraph gives real control over complex multi-step agents
- LangSmith makes agent debugging and evaluation far less painful
Room for improvement
- Steep learning curve, especially moving into LangGraph
- Frequent abstraction churn breaks code across versions
- Heavy abstractions can feel like overkill for simple LLM calls
- LangSmith trace and seat costs add up at production scale
Frequently Asked Questions
What is LangChain?
LangChain is an open-source framework for building applications powered by large language models. It provides building blocks for chaining model calls, connecting tools and data, managing memory, and orchestrating agents, giving developers a common toolkit for LLM apps in Python and JavaScript.
Is LangChain free and open source?
Yes, the LangChain framework and the LangGraph agent library are open source and free to use. The paid products are LangSmith, the observability and evaluation platform, with a free Developer tier and a Plus tier around 39 dollars per seat per month, plus metered LangGraph Platform deployment, as of 2026.
Who is LangChain best for?
LangChain is built for developers who want low-level, programmatic control over LLM applications rather than a no-code builder. It suits engineers assembling custom RAG systems, tool-using agents, and complex pipelines, and pairs with LangGraph for stateful multi-step agents and LangSmith for tracing and evaluation.
What is the difference between LangChain, LangGraph, and LangSmith?
LangChain is the core open-source framework for chaining LLM components. LangGraph is its open library for building stateful, graph-based agent workflows. LangSmith is the paid platform for tracing, debugging, and evaluating those apps in development and production. The framework and LangGraph library are free, while LangSmith and managed deployment are commercial.
Best For
Building production AI agents with durable state and human reviewRetrieval-augmented generation pipelines over private dataTracing and evaluating agents to catch regressions before shippingPrototyping LLM apps quickly with prebuilt chains and integrations
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