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ASRU introduces a controllable unlearning framework for multimodal models that prioritizes generation quality alongside knowledge removal, addressing the common pitfall of producing hallucinated or rigid responses after unlearning. By combining activation steering with reinforcement learning, the method achieves a significant trade-off between forgetting sensitive data and preserving model utility, validated on Qwen3-VL with substantial gains in both metrics. This approach offers a practical solution for maintaining the safety and usability of MLLMs without requiring extensive retraining or supervision data.
Source coveringarXiv

ASRU: Activation Steering Meets Reinforcement Unlearning for Multimodal Large Language Models

arXiv2 min read

arXiv:2605.15687v2 Announce Type: replace Abstract: Multimodal large language models (MLLMs) may memorize sensitive cross-modal information during pretraining, making machine unlearning (MU) crucial. Existing methods typically evaluate unlearning effectiveness based on output deviations, while overlooking the generation quality after unlearning. This can easily lead to hallucinated or rigid responses, thereby affecting the usability and safety of the unlearned model. To address this issue, we propose ASRU, a controllable multimodal unlearning framework that incorporates generation quality as a core evaluation objective. ASRU first induces initial refusal behavior through activation redirection, and then optimizes fine-grained refusal boundaries using a customized reward function, thereby achieving a better trade-off between target knowledge unlearning and model utility. Experiments on Qwen3-VL show that ASRU significantly improves unlearning effectiveness (+24.6%) on average and generation quality (5.8X) on average while effectively preserving model utility, using only a small amount of retained supervision data.

Abstract:Multimodal large language models (MLLMs) may memorize sensitive cross-modal information during pretraining, making machine unlearning (MU) crucial. Existing methods typically evaluate unlearning effectiveness based on output deviations, while overlooking the generation quality after unlearning. This can easily lead to hallucinated or rigid responses, thereby affecting the usability and safety of the unlearned model. To address this issue, we propose ASRU, a controllable multimodal unlearning framework that incorporates generation quality as a core evaluation objective. ASRU first induces initial refusal behavior through activation redirection, and then optimizes fine-grained refusal boundaries using a customized reward function, thereby achieving a better trade-off between target knowledge unlearning and model utility. Experiments on Qwen3-VL show that ASRU significantly improves unlearning effectiveness (+24.6%) on average and generation quality (5.8X) on average while effectively preserving model utility, using only a small amount of retained supervision data.

Computation and Language (cs.CL); Artificial Intelligence (cs.AI)

arXiv:2605.15687 [cs.CL]

(or arXiv:2605.15687v2 [cs.CL] for this version)

https://doi.org/10.48550/arXiv.2605.15687 Focus to learn more arXiv-issued DOI via DataCite

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Full text under the publisher's open licence · 235 words

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