Counterfactual Self-Distillation: A Distribution-Shaping Framework for Entity-Fact Unlearning in Large Language Models

Ying Zhao, Yihui Zhang, Mengyi Deng, Xin Li, Yuan Tian, Wei Wang, Yi Chang


Abstract
Entity-fact unlearning in large language models (LLMs) aims to remove the binding between a target entity and a forgotten fact, producing a model that behaves like one retrained without the forgotten data while preserving neighboring knowledge and overall model utility. We frame this problem as distribution shaping: such a retrained model would yield a plausible distribution at forget queries, fluent, semantically appropriate, and reflective of residual knowledge, which we take as the appropriate target. Existing objectives provide only narrow token-level or semantically uninformative supervision, falling short of this target. We propose Counterfactual Self-Distillation (CSD), a self-distillation framework that approximates the retrained distribution by constructing a counterfactual teacher through type-consistent entity substitution. The resulting teacher is decoupled from the target identity while preserving type-level relational structure, enabling directed probability reallocation without an external oracle. Experiments on TOFU and RWKU show that CSD achieves a strong forget-utility trade-off, including the best overall forgetting on RWKU and strong performance on TOFU.
Anthology ID:
2026.findings-emnlp.1522
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
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Pages:
32401–32414
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.1522/
DOI:
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Cite (ACL):
Ying Zhao, Yihui Zhang, Mengyi Deng, Xin Li, Yuan Tian, Wei Wang, and Yi Chang. 2026. Counterfactual Self-Distillation: A Distribution-Shaping Framework for Entity-Fact Unlearning in Large Language Models. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 32401–32414, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Counterfactual Self-Distillation: A Distribution-Shaping Framework for Entity-Fact Unlearning in Large Language Models (Zhao et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.1522.pdf