Paper

Rollback: Experience Backtracking in World Models for Policy Improvement

Replaces forward-only world-model RL with rollback search that revisits past decisions, compares counterfactual actions, and distills action-level supervision.

arXiv ↗Oct 26, 2026

  • robotics
  • llm
  • world models
  • reinforcement learning
  • tree search
Full method pipeline showing search, tree values, and co-evolution loop
Full method pipeline showing search, tree values, and co-evolution loop

What it is

Uses rewindable world models to backtrack to key robot decisions, branch counterfactual actions, and train policies from action-level comparisons plus real-world grounding. Instead of only doing forward imagined rollouts, it rewinds world-model states to critical decisions, branches alternative actions, and learns from sibling outcome differences. MCTS focuses compute on informative branches, and real robot data continually re-grounds the simulator.

Key results

  • +11.85% success over strongest baseline on tabletop curling
  • +11.11% success over strongest baseline on ball tossing
  • +10.67% success over strongest baseline on block extraction

World models become much more useful for robot policy learning when used as rewindable counterfactual search environments and continually corrected with real experience.

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