When Do Memories Break? Chain-of-Stage Diagnosis for LLM Memory Systems

Chenchen Wang, Yujie Fu, Zhiyu Zheng, Shiyu Qin, Zhao Cao, Zheng Liu


Abstract
Memory-augmented Large Language Models frequently fail to maintain long-term context due to opaque evaluation mechanisms that obscure the root causes of failure. To address this, we introduce MemEval, a stage-wise attribution framework that approximates where failures arise across extraction, update, retrieval, and utilization. On LoCoMo, our automated meta-evaluator achieves 81.62% stage-level consistency with human judgment. Our analysis reveals three critical findings: (1) Extraction is the universal bottleneck, causing information loss at the entry point; (2) Retrieval and utilization failures become prominent in complex reasoning and temporal tasks, even when relevant memories are stored or retrieved; and (3) Scaling base model capacity does not guarantee more reliable memory behavior, as higher-capacity backbones may introduce early-stage misalignment that propagates downstream. MemEval provides a practical diagnostic aid for trend-level, stage-aware analysis of memory systems. Code is available at: https://anonymous.4open.science/r/MemEval-8D41.
Anthology ID:
2026.emnlp-main.1042
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
Note:
Pages:
23931–23951
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1042/
DOI:
Bibkey:
Cite (ACL):
Chenchen Wang, Yujie Fu, Zhiyu Zheng, Shiyu Qin, Zhao Cao, and Zheng Liu. 2026. When Do Memories Break? Chain-of-Stage Diagnosis for LLM Memory Systems. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 23931–23951, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
When Do Memories Break? Chain-of-Stage Diagnosis for LLM Memory Systems (Wang et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1042.pdf