Agents that test how an action could be wrong gain 25.2 points on AppWorld
Typical action checks ask whether the conditions for an agent's action hold, but a wrong action often passes them. BlackSwan has the agent predict each state-changing action's effect, list testable ways it could be wrong, and test them with read-only actions, executing only if none survives. On hard AppWorld tasks it beats the strongest baseline by 14.9 and 25.2 points with and without thinking mode, and lifts WebShop by 12.7 points.