The new harness is a hierarchy: learn targeted variants from discovery trajectories, freeze them, then select a suitable variant for each task.
On 300 held-out AutomationBench tasks, authors report mean partial-credit score rising from 61.62% to 77.41% across three executor runs: a 15.79-percentage-point gain. This is task-specific routing, not a claim that one prompt improves everything.
Evidence & limits. Uses Gemini-3.5-Flash execution plus separate evolution and routing models. Step counts exclude auxiliary selection calls and other rollouts, so they are not total inference cost. Different benchmarks use different metrics; the paper does not establish a statistically significant win over every comparator.
Keep a baseline, route to specialized variants, and account for the search and routing overhead when deciding whether evolution pays off.