arXiv AI By Haoyue Liu, Xiaoying Tang

Events, Not Pixels: Where World Models Get the Return Wrong

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The paper investigates why world models used for planning can misjudge returns despite producing visually accurate rollouts. By replacing imagined transitions with real ones at key event steps—where rewards are earned or episodes end—the authors show that correcting these few transitions eliminates about 70% of return errors, outperforming corrections based on high visual error metrics. Across 44 Atari-100k model–collection pairs, event-based patches significantly improve plan ranking, revealing a structured pattern of remaining errors that can guide further repairs.

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