LangChain Core

The foundational framework providing base abstractions and LangChain Expression Language (LCEL) for modular AI development.

LangChain Core provides the essential abstractions (BaseMessage, PromptTemplate, and Runnable) required to build interoperable LLM applications. It centers on LangChain Expression Language (LCEL): a declarative syntax that enables streaming, async support, and optimized parallel execution. By isolating these base classes from the 700+ external integrations, the library maintains a slim dependency profile (minimizing bloat). This architecture ensures that components from different providers work together seamlessly while providing the reliability needed for enterprise deployments.

https://python.langchain.com/docs/concepts/core/