Langchain

LangChain is an open source framework and agent engineering platform for AI developers and software teams building LLM-powered applications such as chatbots, virtual assistants, and RAG-based question answering.

Key capabilities include:

• Model interfaces and interoperability to connect with multiple LLM providers and swap models without rewriting application logic.
• Retrieval and RAG tooling for data transformation, vector database integrations, and semantic search to ground responses in external knowledge.
• Memory and agent abstractions for conversational state, planning, tool use, and multi-step task execution.
• LangGraph orchestration for stateful, multi-agent workflows using graph-based control, plus a durable runtime with persistence, checkpointing, rewind, and human-in-the-loop support.

Pricing: Free for the open source framework; LangSmith uses usage-based pricing and includes a free plan with 5,000 traces per month.

What makes it notable is the combination of open source building blocks (LangChain and LangGraph) with LangSmith observability, evaluation, monitoring, and deployment tooling, designed to help teams debug agent execution and ship long-running agent workloads in production.