SPRInG: Continual LLM Personalization via Selective Parametric Adaptation and Retrieval-Interpolated Generation

Seoyeon Kim, Jaehyung Kim


Abstract
Personalizing Large Language Models typically relies on static retrieval or one-time adaptation, assuming user preferences remain invariant over time. However, real-world interactions are dynamic, where user interests continuously evolve, posing a challenge for models to adapt to preference drift without catastrophic forgetting. Standard continual learning approaches often struggle in this context, as they indiscriminately update on noisy interaction streams, failing to distinguish genuine preference shifts from transient contexts. To address this, we introduce SPRInG, a novel semi-parametric framework designed for effective continual personalization. During training, SPRInG employs drift-driven selective adaptation, which utilizes a likelihood-based scoring function to identify high-novelty interactions, selectively updating the user-specific adapter on drift signals while preserving hard-to-learn residuals in a replay buffer. During inference, we apply strict relevance gating and fuse parametric knowledge with retrieved history via probability interpolation. Experiments on the long-form personalized generation benchmark demonstrate that SPRInG significantly outperforms existing baselines, validating its robustness for real-world continual personalization.
Anthology ID:
2026.emnlp-main.1551
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
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Pages:
35386–35415
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URL:
https://aclanthology.org/2026.emnlp-main.1551/
DOI:
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Cite (ACL):
Seoyeon Kim and Jaehyung Kim. 2026. SPRInG: Continual LLM Personalization via Selective Parametric Adaptation and Retrieval-Interpolated Generation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 35386–35415, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SPRInG: Continual LLM Personalization via Selective Parametric Adaptation and Retrieval-Interpolated Generation (Kim & Kim, EMNLP 2026)
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https://aclanthology.org/2026.emnlp-main.1551.pdf