Entropy-Adaptive Fine-Tuning: Resolving Confident Conflicts to Mitigate Forgetting

Muxi Diao, Lele Yang, Wuxuan Gong, Yutong Zhang, Zhonghao Yan, Yufei Han, Kongming Liang, Weiran Xu, Zhanyu Ma


Abstract
Supervised Fine-Tuning (SFT) is the standard paradigm for domain adaptation, yet it frequently incurs the cost of catastrophic forgetting. In sharp contrast, on-policy Reinforcement Learning (RL) effectively preserves general capabilities. We investigate this discrepancy and identify a fundamental distributional gap: while RL aligns with the model’s internal belief, SFT forces the model to fit external supervision. This mismatch often manifests as "Confident Conflicts"—tokens characterized by low probability but low entropy. In these instances, the model is highly confident in its own prediction but is forced to learn a divergent ground truth, triggering destructive gradient updates. To address this, we propose Entropy-Adaptive Fine-Tuning (EAFT). Unlike methods relying solely on prediction probability, EAFT utilizes token-level entropy as a gating mechanism to distinguish between epistemic uncertainty and knowledge conflict. This allows the model to learn from uncertain samples while suppressing gradients on conflicting data. Extensive experiments on Qwen and GLM series (ranging from 4B to 32B parameters) across mathematical, medical, and agentic domains confirm our hypothesis. EAFT consistently matches the downstream performance of standard SFT while significantly mitigating the degradation of general capabilities.
Anthology ID:
2026.findings-emnlp.703
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:
14751–14771
Language:
URL:
https://aclanthology.org/2026.findings-emnlp.703/
DOI:
10.18653/2026.findings-emnlp.703
Bibkey:
Cite (ACL):
Muxi Diao, Lele Yang, Wuxuan Gong, Yutong Zhang, Zhonghao Yan, Yufei Han, Kongming Liang, Weiran Xu, and Zhanyu Ma. 2026. Entropy-Adaptive Fine-Tuning: Resolving Confident Conflicts to Mitigate Forgetting. In Findings of the Association for Computational Linguistics: EMNLP 2026, pages 14751–14771, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
Entropy-Adaptive Fine-Tuning: Resolving Confident Conflicts to Mitigate Forgetting (Diao et al., Findings 2026)
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PDF:
https://aclanthology.org/2026.findings-emnlp.703.pdf