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arXiv · 2510.11834

Don't Walk the Line: Boundary Guidance for Filtered Generation

Sarah Ball·Andreas Haupt
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Abstract

Generative models are increasingly paired with safety classifiers that filter harmful or undesirable outputs. A common strategy is to fine-tune the generator to reduce the probability of being filtered, but this can be suboptimal: it often pushes the model toward producing samples near the classifier's decision boundary, increasing both false positives and false negatives. We propose Boundary Guidance, a reinforcement learning fine-tuning method that explicitly steers generation away from the classifier's margin. On a benchmark of jailbreak, ambiguous, and longcontext prompts, Boundary Guidance improves both the safety and the utility of outputs, as judged by LLM-as-a-Judge evaluations. Comprehensive ablations across model scales and reward designs demonstrate the robustness of our approach.

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Sarah Ball, Andreas Haupt. 2025-10-13. Don't Walk the Line: Boundary Guidance for Filtered Generation. https://arxiv.org/abs/2510.11834

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