Long-horizon agent training stops grouping by repeated states alone: adding task progress to the comparison lifts WebShop success by 3.96 and 5.16 points
Long-horizon language-model agent training now builds action preferences inside existing rollout groups, matching on pre-action state plus task progress, and raises mean WebShop success by 3.96 and 5.16 points on Qwen3-4B and 8B.