AdaWM: Few-Shot Adaptation of World Models to Unseen Dynamical Regimes

World models predict future states from observations and actions, enabling planning and decision-making in complex environments. Most existing approaches assume fixed environment dynamics and struggle to generalize to unseen regimes without retraining. However, in many real-world multi-agent systems, environment dynamics vary across scenarios due to diverse styles and evolving agent behaviors. Meanwhile, only a small number of demonstration transitions are available in new environments, making adaptation to such unseen dynamical regimes challenging. In this work, we introduce AdaWM, a world model that achieves zero-gradient few-shot adaptation to unseen dynamical regimes through Feature-wise Linear Modulation (FiLM). AdaWM is built on a JEPA-style latent prediction framework with a permutation-invariant context encoder whose output modulates the model through FiLM, enabling fast adaptation without modifying model parameters. Across heterogeneous multi-agent environments, AdaWM consistently reduces prediction error under distribution shift, outperforming fine-tuning and MAML in both adaptation gain and efficiency. Specifically, it achieves up to 15% reduction in prediction error with only K=5 demonstrations. Moreover, we reveal that scaling model capacity alone does not guarantee effective adaptation: fine-tuning a JEPA-based model with 3.9× more parameters degrades performance by 40%, highlighting the importance of explicit conditioning mechanisms over scale alone. These results show that AdaWM provides an effective approach for adapting world models to novel dynamical regimes.