LangChain, LangGraph, and DeepAgents are three open-source packages designed to facilitate work with Large Language Models (LLMs), each serving distinct roles in the ecosystem. LangChain functions as an agent framework, providing abstractions to simplify the building of applications, though poorly designed abstractions may limit flexibility. LangGraph acts as an agent runtime, focusing on infrastructure-level considerations like durable execution and thread persistence, and it underpins LangChain to enhance its production capabilities. DeepAgents, an agent harness, builds on LangChain to offer additional features such as default prompts and tools for planning, positioning itself as a comprehensive solution with built-in functionalities. The distinctions between these categories—framework, runtime, and harness—are not sharply defined, reflecting the evolving nature of the field and the need for ongoing refinement and feedback in developing conceptual models.