When to Trust Imagination: Adaptive Action Execution for World Action Models

World Action Models (WAMs) jointly predict future visual observations and actions, but typically execute a fixed number of actions before replanning, regardless of whether the imagined future remains consistent with reality. We formulate adaptive WAM execution as future–reality verification and propose Future Forward Dynamics Causal Attention (FFDC), a lightweight verifier that reasons over predicted actions, predicted visual dynamics, real observations, and instruction-conditioned semantics. FFDC allows continued execution when a plan remains reliable and triggers replanning when its validity deteriorates. We combine verification with Mixture-of-Horizon Training to improve long-horizon trajectory coverage. On RoboTwin, FFDC-WAM achieves the highest average success rate among the evaluated methods in both clean and randomized settings. Under randomization, it improves success by 2.54 percentage points over Base-Motus while reducing WAM planning calls by 69.10% and completion time by 33.88%. Zero-shot evaluation on DOMINO shows a favorable trade-off over fixed 16-action execution. Across six real-world tasks on a Unitree G1D robot, FFDC-WAM improves average success by 9.17 percentage points over Base-Motus-LC16 while reducing calls by 74.06% and completion time by 51.31%.