MemBook: A Hierarchical Reasoning-based Memory Framework for Hallucination-Resistant LLM Agents

Tongshu Bian, Yunxin li, Zhenran Xu, Tianqi Shi, Longyue Wang, Baotian Hu, Min Zhang


Abstract
Memory is a cornerstone of foundation model-based agents for ultra-long-term interaction. However, hallucinated or noisy information can accumulate inside memory systems and progressively contaminate downstream tasks. Existing systems face two key challenges: (1) memory construction mechanisms trade off between faithful recall and hallucination suppression; and (2) retrieval relies on shallow semantic similarity, failing to distinguish logically irrelevant memories. We propose **MemBook**, a hierarchical time-aware memory framework for hallucination-resistant agents. For memory construction, MemBook introduces a stateful memory stabilization mechanism that prevents hallucinated claims from being consolidated into persistent memory and organizes reliable memories into an evolving Session–Chapter–Memory Point hierarchy. For memory retrieval, MemBook performs reasoning-based hierarchical retrieval over this evolving memory book to identify temporally and logically relevant memories. Experiments on HaluMem-Medium, HaluMem-Long, and LongMemEval show that MemBook improves extraction quality and downstream performance while suppressing cross-stage hallucination propagation. Notably, MemBook remains stable under ultra-long contexts, outperforming GAM by absolute 19.57% QA accuracy improvement on HaluMem-Long.
Anthology ID:
2026.findings-emnlp.1847
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
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Pages:
39444–39470
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URL:
https://aclanthology.org/2026.findings-emnlp.1847/
DOI:
Bibkey:
Cite (ACL):
Tongshu Bian, Yunxin li, Zhenran Xu, Tianqi Shi, Longyue Wang, Baotian Hu, and Min Zhang. 2026. MemBook: A Hierarchical Reasoning-based Memory Framework for Hallucination-Resistant LLM Agents. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 39444–39470, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
MemBook: A Hierarchical Reasoning-based Memory Framework for Hallucination-Resistant LLM Agents (Bian et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1847.pdf