LangChain

LangChain is an open-source framework for building applications with large language models. It is designed for software engineers, ML engineers, and technical teams who want to turn LLMs into reliable, production-ready products without reinventing the infrastructure around prompts, tools, and data.

LangChain is primarily a developer framework and set of libraries. You run it within your own application stack and connect it to the model providers, vector databases, and infrastructure of your choice. Some ecosystem tools offer hosted experiences, but the core LangChain project is not a closed SaaS product.

LangChain does not host its own language models. Instead, it provides integrations with many third-party providers (such as OpenAI and others) and open-source models. You choose and configure the models you want to use, and LangChain helps orchestrate them within your application.

The LangChain framework itself is open source and free to use under its license. However, you may incur costs from the model providers, vector databases, and cloud infrastructure you connect to through LangChain, depending on their pricing.

Yes. LangChain includes patterns and tooling aimed at production use, such as structured chains, retrievers, evaluation utilities, and observability integrations. Many teams use it to power real-world products, though you should still add your own monitoring, testing, and safety layers appropriate to your domain.