Why video models break physics: trajectory locked in first 10% of denoising

linoy_tsaban · x · 2026-09-25

Arguing that video models are now convincing enough that we should scrutinize their physical faithfulness, the author highlights a mechanistic interpretability study: an object's trajectory gets locked in during the first 10% of denoising, and RoPE's spatial decay locks it onto the wrong position. A one-line change to the rotary embedding fixes it. Since the paper only tested Wan2.1-1.3B, she is now applying the fix to H3 to see if it generalizes.

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