LangChain

LangChain is an open-source Python framework for building agents and LLM-powered applications. It is aimed primarily at developers and teams that want to assemble model calls, tools, retrieval, and integrations into custom workflows rather than use a finished end-user app.

According to its documentation and README, it positions itself as an "agent engineering platform" with a modular design for chaining interoperable components. You get started by installing the Python package (pip install langchain or uv add langchain) and importing the library into your codebase. It also sits inside a broader ecosystem that includes LangGraph for more controllable orchestration and LangSmith for debugging, evaluation, and deployment support.

LangChain is strongest when you need flexibility and a large integration surface. It is useful for prototyping and production development, but it is not a turnkey autonomous agent product; you still need to design the workflow, choose models, and wire up your own tools and systems. The README also points developers looking for more advanced orchestration to LangGraph, which suggests LangChain alone is more of a building block than a complete agent runtime.

The project is open source under the MIT license. The README shows an example using OpenAI models, but it also emphasizes model interoperability rather than locking you to one provider. Pricing for the core library is not described on the README page, so if you are looking for hosted platform costs or commercial tiers, those details were not clearly available here.