Causal-History Test-Time Scaling for Failure Recovery in Autoregressive World-Action Models

World-action models (WAMs) have emerged as a promising paradigm for robot manipulation by jointly modeling future visual dynamics and robot actions. However, existing WAMs are trained predominantly on successful trajectories, making them prone to failure when real-world execution diverges from the learned dynamics. This issue is amplified in autoregressive WAMs, where execution errors become part of the causal history and continue to influence subsequent predictions. To this end, we introduce method, a training-free framework that reformulates failure recovery as test-time scaling over causal histories. This formulation decomposes recovery into three coupled decisions: when to revise the causal history, where to recover a reliable history prefix, and which history configuration best supports subsequent execution. Specifically, method realizes these decisions through three stages: 1) Progress-Aware Recovery Trigger detects persistent non-progress and triggers recovery only when the current execution state permits intervention; 2) History-Prefix Recovery identifies the unreliable history suffix, retrieves a historical anchor matching the current physical state, and reconstructs the causal KV state from the retained prefix while conditioning on the latest real observation; and 3) Hypothesis Verification compares the future continuations induced by complete-history, recovered-prefix, and full-reset hypotheses, and commits the best-supported hypothesis. Experiments in both simulated and real-world manipulation settings demonstrate consistent improvements in task success, while ablations confirm the contribution of each recovery stage.