Beyond the Current Observation: Evaluating Multimodal Large Language Models in Controllable Non-Markov Games

Shengyuan Ding, Xilin Wei, Xinyu Fang, Haodong Duan, Dahua Lin, Jiaqi Wang, Yuhang Zang


Abstract
Deploying multimodal foundation models as closed-loop policies increasingly requires conditioning actions on observations that are no longer visible. However, existing benchmarks either expose the full state, conflate hidden-state reconstruction with other agent skills, or test recall only after an episode has ended. We introduce RNG-Bench (Reconstructive Non-Markov Games), a benchmark suite designed to measure a base model’s ability to reconstruct past observations and act on them during multi-step interaction. RNG-Bench includes two complementary games: Matching Pairs, where card identities briefly revealed at specific locations must later be recalled, and 3D Maze, where egocentric views must be integrated into a spatial map. Both games are evaluated under a unified harness with three controlled difficulty axes: grid size, visual pattern, and observation modality. The benchmark further introduces a head-to-head duel protocol to control for instance-level variance and a Memory Gap diagnostic that reports the normalized baseline-to-oracle score difference under a specified interface. The hardest configurations require contexts of roughly 128K tokens and 350 image inputs per episode, and remain far from saturated by frontier MLLMs. The oracle interface yields substantial gains in some settings, while sizeable residual errors remain in others. Finally, fine-tuning Qwen3.5-9B on optimal-policy rollouts and filtered model demonstrations improves performance on RNG-Bench and transfers to existing benchmarks without degrading general multimodal capability.
Anthology ID:
2026.emnlp-main.1587
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
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Pages:
36087–36108
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URL:
https://aclanthology.org/2026.emnlp-main.1587/
DOI:
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Cite (ACL):
Shengyuan Ding, Xilin Wei, Xinyu Fang, Haodong Duan, Dahua Lin, Jiaqi Wang, and Yuhang Zang. 2026. Beyond the Current Observation: Evaluating Multimodal Large Language Models in Controllable Non-Markov Games. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 36087–36108, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Beyond the Current Observation: Evaluating Multimodal Large Language Models in Controllable Non-Markov Games (Ding et al., EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.1587.pdf