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arXiv · 2610.14727

MHWA: Multi-timescale Hierarchical World-Action Model

Pengcheng Pan·Guoqing Ma·Yuhan Zhang·Yang Chen·Yichen Liu·Ziheng Li·Shan Yu
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Abstract

Autoregressive world models have emerged as a powerful paradigm for sample efficient decision making, yet their open loop rollouts often exhibit increasing drift that leads to error accumulation even within a relatively small planning horizon. Hierarchical temporal abstraction is a natural candidate to mitigate such drift by reducing the effective prediction horizon; however, existing hierarchical designs can introduce added structural and conceptual complexity, sometimes making them difficult to control and limiting gains over flat baselines. To this end, we introduce MHWA (Multi-timescale Hierarchical World-Action model), which employs a strided high level context channel to reduce global context update frequency, effectively curbing the propagation of compounding drift. Crucially, via context aware routing, the gating network dynamically reconfigures a low level mixture of experts by using both global context and current observations, thereby enabling flexible high-low coordination, helping alleviate interference commonly observed in static hierarchies. Empirically, using RLiable's seed-by-game aggregation, MHWA (77M parameters) achieves an IQM human normalized score (HNS) of 0.884 across three training seeds on a 14-game Atari subset using 10% subsampled offline data, outperforming a matched JOWA-70M baseline (0.529) and achieving numerically comparable performance to JOWA-150M while using nearly half the parameters and 70.88% fewer training FLOPs per sequence.

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Pengcheng Pan, Guoqing Ma, Yuhan Zhang, Yang Chen, Yichen Liu, Ziheng Li, Shan Yu. 2026-10-10. MHWA: Multi-timescale Hierarchical World-Action Model. https://arxiv.org/abs/2610.14727

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