HyperTrace: Hypothesis-Based Preference Tracing for Online LLM Personalization

Jianzhi Shen, Keyu Mao, Minghao Shao, Chuanyang Jin, Yusong Wang, Ailiang Lin, Kotaro Funakoshi, Manabu Okumura, Muhammad Shafique


Abstract
Personalized language models aim to adapt responses to individual users, whose preferences are often latent and revealed gradually through interaction. Existing training-free methods rely on stored histories or retrieved memories, but they often struggle to reconcile long-term preferences with short-term topic-specific needs. To address this issue, we propose HyperTrace, a training-free framework that formulates online personalization as latent preference tracing. HyperTrace maintains interpretable natural-language hypotheses over short-term intent and long-term preferences, and updates them through an SMC-style reweight process using an LLM-based surrogate choice model. By updating these hypotheses across turns and sessions, HyperTrace enables personalization without parameter updates. Experiments on PRISM and PersonaMem-v2 show that HyperTrace improves response alignment, preference prediction, and profile consistency over strong online baselines, demonstrating the effectiveness of tracing latent user preferences for robust personalization. Code and scripts are available in the repository: [https://github.com/jiseshen/HyperTrace](https://github.com/jiseshen/HyperTrace).
Anthology ID:
2026.findings-emnlp.1038
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
Note:
Pages:
21936–21951
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1038/
DOI:
10.18653/2026.findings-emnlp.1038
Bibkey:
Cite (ACL):
Jianzhi Shen, Keyu Mao, Minghao Shao, Chuanyang Jin, Yusong Wang, Ailiang Lin, Kotaro Funakoshi, Manabu Okumura, and Muhammad Shafique. 2026. HyperTrace: Hypothesis-Based Preference Tracing for Online LLM Personalization. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 21936–21951, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
HyperTrace: Hypothesis-Based Preference Tracing for Online LLM Personalization (Shen et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1038.pdf