AI agents often learn internal models of their environment called world models. These models are usually judged by task performance, not by whether they truly understand how the environment changes under the agent's actions. This can hide failures in reasoning.
The authors introduce a new metric, latent rollout consistency, which checks if a world model's predictions match the actual environment over time. They test three popular world models on simple control tasks like balancing a pole.
They find that even though all models achieved good task performance, none learned a faithful model of the environment's dynamics. This matters because agents need accurate world models to plan in new situations, not just perform seen tasks.
