LangChain is a comprehensive framework for building LLM-powered applications. It provides core abstractions for language models, prompts, chains, agents, memory, and tools, enabling developers to create complex AI systems like chatbots, question-answering agents, and retrieval-augmented generation pipelines. The architecture is modular with clear separation between core langchain_core foundations, legacy langchain_classic components (many deprecated), and partner integrations for specific LLM providers and vector stores. Key entry points include agent creation functions, chain constructors, and memory/retriever interfaces. The framework emphasizes composability through the Runnable interface (LCEL) and supports both synchronous and asynchronous operations. While extensive, the codebase shows strong maintenance practices with active dependency management and version consistency checks across integrations.
Langchain.rb is a Ruby gem for building LLM-powered applications with a unified interface to multiple LLM providers and vector databases. It provides a modular architecture supporting Retrieval Augmented Generation (RAG), AI agents with tool usage, document processing, and prompt templating. The gem includes a Rails engine for deep Rails integration and is actively maintained with frequent updates. The system enables developers to create interactive AI applications by combining LLMs, external tools, and vector search capabilities.