PGMem: Tightly Coupled Persona–Memory Graph for Lifelong Personalized Agents

Wonjun Choi, Yerim Kim, Yukyung Lee, Susik Yoon


Abstract
Long-term personalized dialogue agents must track user preferences as their personas evolve. Existing memory systems organize past events well, but store personas as flat profiles detached from the events that justify them. This loose coupling leads to the memory–persona validity gap and the persona-aware retrieval gap. We propose PGMem, a heterogeneous persona-memory graph that connects event and persona nodes through typed provenance and evidence edges, keeping each persona signal traceable to the events that support or revise it. At retrieval time, PGMem expands from query-relevant seeds and ranks signals by evidential validity. Across three benchmarks with small language model backbones, PGMem consistently outperforms summary-based, persona-aware, graph-structured, and agentic memory baselines, and improves performance as the context grows. The source codes of PGMem are available at https://github.com/wonjunchoi23/pgmem/
Anthology ID:
2026.emnlp-main.1891
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:
43087–43112
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1891/
DOI:
Bibkey:
Cite (ACL):
Wonjun Choi, Yerim Kim, Yukyung Lee, and Susik Yoon. 2026. PGMem: Tightly Coupled Persona–Memory Graph for Lifelong Personalized Agents. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 43087–43112, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
PGMem: Tightly Coupled Persona–Memory Graph for Lifelong Personalized Agents (Choi et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1891.pdf