Agents That Finish

Agent reliability is an architecture, not a model property: systems complete multi-hour work because they can decompose it, verify each step, checkpoint state and undo a wrong commitment.

Frontier models are close to perfect on work a skilled person would finish in four minutes and close to useless on work that takes four hours. The gap is not intelligence. It is that most agent architectures cannot notice a wrong intermediate state, let alone roll one back, so the first bad commitment is inherited by every step after it. This book builds outwards from that failure mode: decomposition as a real artifact, verification between steps, checkpoints an agent can resume from, compensating actions for effects that already left the system, and budgets that bound the damage when none of it works.