What is an agent harness? Explained fast

This post defines an agent harness as the component that enables a model to perceive, act, persist information, and enforce boundaries. It highlights four key pieces of a harness: a file system for offloading data, subagents for isolating and parallelizing work, and skills that models load on demand. The post emphasizes that without a harness, models can exceed context windows and lose track of their tasks. It introduces Deep Agents as LangChain's opinionated harness that includes file system, subagents, and memory integration, allowing for swappable backends and easy addition of new capabilities.