Ash Prabaker

Long-Running Agents Need Separate Builders, Evaluators, and Disposable Scaffolding

Anthropic’s Ash Prabaker and Andrew Wilson argue that long-running agents are a harness-design problem, not a matter of writing longer prompts. Their case is that agents can run for hours only when building, judging, planning and state management are separated: adversarial evaluators should test live behavior, work should be decomposed into explicit contracts, and durable state should live outside the model’s context. They also warn that this scaffolding is provisional, because each new model release changes which supports are useful and which have become dead weight.