MedACE: A Time-Aware Asynchronous Clinical Environment for Long-Horizon Medical Treatment Decision-Making

Zhiting Fan, Ruizhe Chen, Hualiang Wang, Ru Peng, Zijie Meng, Wen MA, Jian Wu, Zuozhu Liu


Abstract
Recent advances in Medical Large Language Models have shown strong performance in medical question answering and clinical knowledge understanding, yet real-world clinical practice requires long-horizon, dynamic treatment decision-making rather than static prediction. Existing medical agent environments are mostly turn-based, assuming patient states change after actions while overlooking natural disease progression and delayed treatment effects. We propose MedACE, a time-aware asynchronous clinical world model, where patient evolution is formulated as an elapsed-time-conditioned process driven by historical observations, treatment actions, clinical context, and disease-level knowledge. Built from timestamped MIMIC-IV trajectories, our JEPA-style simulator, MedWorld-JEPA, learns future patient state representations in latent space rather than directly generating noisy clinical observations. Based on this simulator, we construct an asynchronous treatment environment with global time advancement, closed-loop patient simulation, multi-step physician-agent interaction, and outcome-grounded rewards. Experiments on Hospital and ICU scenarios demonstrate competitive physiological forecasting, strong clinical consistency, and the importance of jointly modeling time, disease progression, and treatment effects. Agent evaluations further show that current LLM-based physicians struggle with long-horizon treatment decisions, highlighting our environment as a challenging foundation for future medical treatment agents.
Anthology ID:
2026.findings-emnlp.2316
Volume:
Findings of the Association for Computational Linguistics: EMNLP 2026
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
Findings
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
49730–49743
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.2316/
DOI:
Bibkey:
Cite (ACL):
Zhiting Fan, Ruizhe Chen, Hualiang Wang, Ru Peng, Zijie Meng, Wen MA, Jian Wu, and Zuozhu Liu. 2026. MedACE: A Time-Aware Asynchronous Clinical Environment for Long-Horizon Medical Treatment Decision-Making. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 49730–49743, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
MedACE: A Time-Aware Asynchronous Clinical Environment for Long-Horizon Medical Treatment Decision-Making (Fan et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.2316.pdf