@inproceedings{zhang-etal-2026-memmark,
title = "{MEMMARK}: State-Evolution Attribution Watermarking for Agent Long-Term Memory Systems",
author = "Zhang, Haobo and
Mao, Xutao and
Dong, Guangyuan and
Li, Ziwei and
Su, Xuanbo and
Chen, Kaijie and
Yang, Jing and
Lin, Zheng",
editor = "Lee, Hung-Yi and
Dev, Sunipa and
Li, Jessy and
Elliott, Desmond",
booktitle = "Findings of the {A}ssociation for {C}omputational {L}inguistics: {EMNLP} 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.findings-emnlp.395/",
pages = "8333--8349",
ISBN = "979-8-89176-462-0",
abstract = "Memory-backed agents need provenance that can survive leaked or migrated snapshots, where logs, visible outputs, and trusted metadata may be absent. We propose MEMMARK, a state-evolution attribution watermark that embeds an owner-controlled signal into latent memory-write decisions. At each internal LLM call, MEMMARK samples among admissible candidates using keyed, distribution-preserving selection, and records cryptographic commitments with signed session anchors and reveal evidence. This makes attribution depend on reproducible backend behavior rather than mutable provenance fields. Across A-Mem and Graphiti on LOCOMO, with three LLM backbones, MEMMARK preserves memory utility: Overall F1 retains 99.6 percent of the unwatermarked baseline, while BLEU-1 changes by +0.2 percent. It also provides usable carrier capacity, with 1.16, 1.14, and 1.26 bits of mean entropy for update-target, link-target, and semantic-realization decisions. In the snapshot-only R3 setting, MEMMARK recovers the full 40-bit payload from final snapshots, while wrong-key verification remains near chance. Under nine memory-lifecycle attacks, verification distinguishes tampering, evidence deletion, and partial payload recovery. These results show that robust snapshot-only attribution is feasible for long-term agent memory without surviving traces, trusted metadata, or utility degradation."
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<abstract>Memory-backed agents need provenance that can survive leaked or migrated snapshots, where logs, visible outputs, and trusted metadata may be absent. We propose MEMMARK, a state-evolution attribution watermark that embeds an owner-controlled signal into latent memory-write decisions. At each internal LLM call, MEMMARK samples among admissible candidates using keyed, distribution-preserving selection, and records cryptographic commitments with signed session anchors and reveal evidence. This makes attribution depend on reproducible backend behavior rather than mutable provenance fields. Across A-Mem and Graphiti on LOCOMO, with three LLM backbones, MEMMARK preserves memory utility: Overall F1 retains 99.6 percent of the unwatermarked baseline, while BLEU-1 changes by +0.2 percent. It also provides usable carrier capacity, with 1.16, 1.14, and 1.26 bits of mean entropy for update-target, link-target, and semantic-realization decisions. In the snapshot-only R3 setting, MEMMARK recovers the full 40-bit payload from final snapshots, while wrong-key verification remains near chance. Under nine memory-lifecycle attacks, verification distinguishes tampering, evidence deletion, and partial payload recovery. These results show that robust snapshot-only attribution is feasible for long-term agent memory without surviving traces, trusted metadata, or utility degradation.</abstract>
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%0 Conference Proceedings
%T MEMMARK: State-Evolution Attribution Watermarking for Agent Long-Term Memory Systems
%A Zhang, Haobo
%A Mao, Xutao
%A Dong, Guangyuan
%A Li, Ziwei
%A Su, Xuanbo
%A Chen, Kaijie
%A Yang, Jing
%A Lin, Zheng
%Y Lee, Hung-Yi
%Y Dev, Sunipa
%Y Li, Jessy
%Y Elliott, Desmond
%S Findings of the Association for Computational Linguistics: EMNLP 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-462-0
%F zhang-etal-2026-memmark
%X Memory-backed agents need provenance that can survive leaked or migrated snapshots, where logs, visible outputs, and trusted metadata may be absent. We propose MEMMARK, a state-evolution attribution watermark that embeds an owner-controlled signal into latent memory-write decisions. At each internal LLM call, MEMMARK samples among admissible candidates using keyed, distribution-preserving selection, and records cryptographic commitments with signed session anchors and reveal evidence. This makes attribution depend on reproducible backend behavior rather than mutable provenance fields. Across A-Mem and Graphiti on LOCOMO, with three LLM backbones, MEMMARK preserves memory utility: Overall F1 retains 99.6 percent of the unwatermarked baseline, while BLEU-1 changes by +0.2 percent. It also provides usable carrier capacity, with 1.16, 1.14, and 1.26 bits of mean entropy for update-target, link-target, and semantic-realization decisions. In the snapshot-only R3 setting, MEMMARK recovers the full 40-bit payload from final snapshots, while wrong-key verification remains near chance. Under nine memory-lifecycle attacks, verification distinguishes tampering, evidence deletion, and partial payload recovery. These results show that robust snapshot-only attribution is feasible for long-term agent memory without surviving traces, trusted metadata, or utility degradation.
%U https://aclanthology.org/2026.findings-emnlp.395/
%P 8333-8349
Markdown (Informal)
[MEMMARK: State-Evolution Attribution Watermarking for Agent Long-Term Memory Systems](https://aclanthology.org/2026.findings-emnlp.395/) (Zhang et al., Findings 2026)
ACL
- Haobo Zhang, Xutao Mao, Guangyuan Dong, Ziwei Li, Xuanbo Su, Kaijie Chen, Jing Yang, and Zheng Lin. 2026. MEMMARK: State-Evolution Attribution Watermarking for Agent Long-Term Memory Systems. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 8333–8349, Budapest, Hungary. Association for Computational Linguistics.