Retrievable Gradients: Continual Post-Training Without Cumulative Weight Drift

Weihang Su, Jiacheng Kang, Jingyan Xu, Qingyao Ai, Jianming Long, Hanwen Zhang, Bangde Du, Xinyuan Cao, Min Zhang, Yiqun Liu


Abstract
Continual post-training enables models to absorb emerging knowledge after deployment, but repeatedly updating shared parameters inevitably accumulates weight drift, which causes catastrophic forgetting and degrades general capabilities. Retrieval-augmented generation avoids such parameter drift, yet often lacks the depth of parametric knowledge integration. In this paper, we propose ReGrad (Retrievable Gradients), a new paradigm that treats gradients as retrievable units of knowledge. ReGrad pre-computes document-specific gradients offline, stores them in an indexed Gradient Bank, and retrieves only query-relevant gradients at inference time for temporary weight adaptation. However, raw language-modeling gradients are optimized for token-level document reconstruction rather than for query-driven knowledge use. We therefore introduce a bi-level meta-learning objective that reshapes document-derived gradients into generalizable adaptation signals for downstream tasks. Experiments across general and domain-specific settings show that ReGrad outperforms CPT and RAG baselines, enabling scalable and reversible parametric knowledge injection without accumulating weight drift.
Anthology ID:
2026.emnlp-main.1197
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:
27407–27426
Language:
URL:
https://aclanthology.org/2026.emnlp-main.1197/
DOI:
Bibkey:
Cite (ACL):
Weihang Su, Jiacheng Kang, Jingyan Xu, Qingyao Ai, Jianming Long, Hanwen Zhang, Bangde Du, Xinyuan Cao, Min Zhang, and Yiqun Liu. 2026. Retrievable Gradients: Continual Post-Training Without Cumulative Weight Drift. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 27407–27426, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Retrievable Gradients: Continual Post-Training Without Cumulative Weight Drift (Su et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.1197.pdf