Diagnosing JEPA World Models with Action-Conditioned Predictive Consistency
Although JEPA-based world models perform prediction in latent space, they remain susceptible to visual perturbations, leading to distorted state representations and biased action-conditioned predictions. This work proposes Action-Conditioned Prediction Consistency (ACPC), a diagnostic framework that, for the first time, operationalizes the twin-simulation concept into a computable metric by quantifying the divergence between multi-step forward rollouts from clean and perturbed observations under identical action sequences. To enable robustness evaluation across tasks and architectures, we introduce two complementary metrics: Invariance Radius (IR) and Separation Rate (SR). Empirical results demonstrate that ACPC effectively predicts perturbation-induced errors in prediction and planning costs, and the IR–SR pair exhibits strong generalization and diagnostic capability across models such as LeWM and PLDM.