LLMs have specialized capabilities as task creators versus solvers, and measuring these distinct skills through head-to-head interactions reveals stable patterns that reflect how models influence each other in practice.
This paper introduces Environment Duels, a benchmark where LLMs both create interactive tasks (with helpful hints) and solve tasks created by others. Testing nine frontier models reveals that solving and authoring are distinct skills, smaller models write harder tasks, and the interactions mirror real-world LLM co-evolution patterns.