Robot World Models Are Not Invariant to How the Actions Are Written
A robot policy is trained with one of two action parameterizations: absolute joint targets, or deltas relative to the current state. The choice is a live engineering decision in robot learning, and a world model conditioned on actions inherits it silently. We show the inheritance is catastrophic. A latent dynamics model trained on one parameterization and handed the identical commanded trajectory written in the other collapses: retrieval degrades by 2.6-13.4x across three robot datasets and two morphologies, goal-conditioned action selection falls from 53% to 15%, and on PushT the two beliefs about the same future are near-orthogonal (cos = 0.067, worst case -0.377), so the predictor does...
| Authors | Ahmed Karim, Leon Chlon |
|---|---|
| Primary category | cs.RO |
| Published | 19 September 2026 |
| Last updated at source | 19 September 2026 |
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