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MemWM: Memory-Augmented Text-Based World Model

MCML Authors

Abstract

World models are increasingly used to support planning in agents by predicting how environment states evolve in response to agent actions. Yet fluent next-state predictions can still omit task-critical facts, corrupt product attributes, or apply incorrect transition rules. To address such systematic prediction errors, we introduce MemWM, a memory-augmented text-based world model. MemWM uses world memory, a curated memory bank of transition rules, state caches, and hard-to-predict facts, to condition next-state imagination. We evaluate factual state preservation with Structured State Fidelity (SSF), which scores predicted states through benchmark-specific facts and fields. Compared with SFT, memory-augmented training improves SSF by up to 206.3%. In the full planning setting, we keep the policy model frozen and provide policy-side world skill: retrieved task-level skills and step-wise corrective guidance for action selection. Across ALFWorld, WebShop, and ScienceWorld, memory-augmented agents improve downstream success over an SFT-trained world-model agent, with up to a 65.4% relative gain. Sensitivity analyses further show that retrieved memory improves task success and efficiency under different memory and action-budget settings.

inproceedings WZB+26


EMNLP 2026

Conference on Empirical Methods in Natural Language Processing. Budapest, Hungary, Oct 24-29, 2026. To be published. Preprint available.
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A* Conference

Authors

Y. Wang • T. Zhang • J. Bi • A. Aniri • W. Ye • B. Liu • S. Yan • S. Wang • X. Zhou • S. Pirk • H. Schütze • Y. Ma

Links

arXiv

Research Areas

 A3 | Computational Models

 B2 | Natural Language Processing

BibTeXKey: WZB+26

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