Predicting the future in robot policies quietly broke two precise tasks, and an adapter fixed it
AspireAI community · arXiv
World Action Models let a robot condition its actions on a generated visual future, but that future is neither free nor uniformly useful. Measuring the action delta between future-conditioned and future-free execution of the same checkpoint, this work finds average success barely moves (+0.8 points on LIBERO, -0.8 on RoboTwin 2.0) while inference latency rises 1.7-1.9x, and that this average hides a concentrated failure: Press Stapler and Place Can Basket lose 54.0 and 34.0 points. Utility-WAM adds a residual adapter that repairs future-induced velocity deltas under a frozen shared model, cutting those losses to 6.0 and 14.0 points, plus a pre-generation gate that skips video generation on 75.5% of RoboTwin queries. On real bimanual manipulation it succeeds in 53 of 60 trials against 43 for FAST-WAM. Results are on one benchmark suite and one robot family.
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.