LangChain

What LangChain is

LangChain is a free, open-source framework for building agents that work with models and tools. Its `create_agent` harness brings a model, tools, a prompt, and middleware together in a configurable agent, with templates for common use cases and a ReAct pattern. Middleware can add human approval, conversation compression, sensitive-data removal, guardrails, retries, routing, and custom tool policies. Agents run on LangGraph’s durable runtime, which supports persistence, rewind, checkpointing, and human-in-the-loop workflows.

The framework documents more than 1,000 integrations for chat and embedding models, tools and toolkits, document loaders, and vector stores. Standard interfaces for chat models and embeddings let developers switch providers with minimal code changes. Documentation and installation examples cover Python and JavaScript/TypeScript. LangSmith can trace requests, help debug agent behavior, and evaluate application outputs. Its Trust Center lists SOC 2 Type II, ISO 27001:2022, GDPR, and HIPAA compliance; its pricing FAQ says customer data stays private to the organization and is not used to train models. The framework is MIT-licensed and free. LangSmith has separate plans, including a free Developer tier with one seat and up to 5k base traces per month before pay-as-you-go charges.

Who it suits

LangChain suits developers building configurable agents with models, tools, and middleware, especially those who want a broad choice of integrations or model providers. Its framework documentation and installation examples cover Python and JavaScript/TypeScript.

Limits

The free LangSmith Developer plan has one seat and includes up to 5k base traces per month; additional usage is billed pay as you go. The free LangChain framework is an open-source library.

Getting started

1. Visit the LangChain website.
2. Choose the LangChain framework or a LangSmith plan, depending on your needs.
3. Use the framework documentation and installation examples for Python or JavaScript/TypeScript.
4. Build an agent with `create_agent` and configure its model, tools, prompt, and middleware.
5. Use LangSmith to trace requests and evaluate application outputs.

Verdict

Choose LangChain to build agents around models and tools using its configurable harness, middleware, and wide range of integrations. Look elsewhere if you need multiple LangSmith seats or trace capacity beyond the free Developer allowance without pay-as-you-go charges; Plus costs $39 a month per seat.