This is part three of our five-part series on agentic harnesses. We've covered what a harness is and the loop and tools that let an agent act. Now we hit the part that decides whether an agent can work for ten minutes or ten hours: context management.
The Problem: A Finite Window
Everything a model "knows" in the moment lives in its context window: the instructions, the conversation so far, the files it has read, the output of every tool call. That window is finite, and long tasks overflow it fast. As it fills, two things go wrong: the model loses coherence, and it starts behaving strangely about finishing.
Context management exists to keep the model working coherently anyway. There are a handful of techniques, and the art is knowing which to reach for.
