THE STATE MACHINE NOBODY DESIGNED

Summary from the TLDR newsletter

Every part of an agent harness adds information to the model's context, controls what information is allowed into that context, or checks the model's output after it is generated. This is just context engineering. Thinking in terms of harnesses makes developers think in terms of adding components. Context is limited, so it's not just about what you can add, but about what's worth keeping as well. The context window is the whole state machine.