A robot policy that failed can rewind its own arm and try again, with a head that adds under one percent of its parameters
AspireAI community · arXiv
Vision-language-action policies are brittle once their own actions push them into states their training data barely covers, and the usual fix is recovery demonstrations, retraining, or a second model at inference time. Backtrack avoids all three: a small failure prediction head, trained only on outcome-labeled rollouts of the frozen policy, reads the policy's existing internal representations to estimate whether the episode will fail, and when that probability crosses a threshold a controller pauses the policy, retraces the arm's recent motion and hands control back so it can retry from an earlier configuration. The head adds only 0.48 to 0.88 percent to the policy's parameter count. On LIBERO-Long, the long-horizon suite where all three tested policies fail most often, it cut each policy's failure rate by 19 to 48 percent and lifted success by up to 7.4 percentage points, with smaller effects on three shorter suites already running at 85 to 99 percent success and improvements in all twelve controller configurations tested on MetaWorld.
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