| title | PolicyShiftGuard: Benchmarking and Improving Policy-Adaptive Image Guardrails |
|---|---|
| authors | Mingyang Song, Luxin Xu, Haoyu Sun, Minzhou Pan, Yu Cheng, Bo Li |
| date | 2026-07-07 |
| venue | arXiv (preprint, not peer reviewed) |
| id | arXiv:2607.05910 |
| affiliation | Fudan University |
| upvotes | 3 (Hugging Face Daily Papers, 2026-11-01) |
| links | abs pdf hf code |
| abstract | Image guardrails are typically trained and evaluated under a fixed safety policy, implicitly treating safety as an intrinsic property of an image. Real deployments are different: the same image may be allowed in one product, restricted in another, and newly disallowed when a policy boundary changes. We study policy-adaptive image guardrailing, where a model must decide whether an image violates the currently supplied policy and generalize to held-out policy definitions. We introduce PolicyShiftBench, a comprehensive benchmark with 2,000 policy-discriminative instances over 265 images, where each image is paired with 7.55 policy-conditioned prompts on average to test whether models adapt to the active policy rather than relying on image-level safety priors. We then propose PolicyShiftGuard, a compact policy-conditioned guardrail trained with a two-stage training recipe that combines Randomized Policy SFT (RP-SFT) with Boundary-Pair Policy Adaptation (BP-Adapt). BP-Adapt trains matched prompts for the same image and risk category using standard label supervision and a pairwise comparison loss that separates blocking policies from passing policies. Experiments show that existing VLMs and specialized guardrails remain brittle under policy shifts, while PolicyShiftGuard substantially improves policy-sensitive performance. The 7B model achieves SOTA performance of 76.9 Avg. F1 and 72.1 Avg. PSS on PolicyShiftBench, transfers well to UnSafeBench and SafeEditBench, and improves the latency-performance trade-off with a concise output format. Ablations confirm that matched pass/block boundary pairs are essential for stable policy adaptation. |
cite
@misc{song2026policyshiftguard,
title={PolicyShiftGuard: Benchmarking and Improving Policy-Adaptive Image Guardrails},
author={Mingyang Song and Luxin Xu and Haoyu Sun and Minzhou Pan and Yu Cheng and Bo Li},
year={2026},
eprint={2607.05910},
archivePrefix={arXiv},
url={https://arxiv.org/abs/2607.05910}
}