Guardian-as-an-Advisor: Advancing Next-Generation Guardian Models for Trustworthy LLMs

arXiv cs.CL / 4/10/2026

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Key Points

  • Hard-gated safety checkers can over-refuse and conflict with a vendor model’s specification, motivating a softer, spec-preserving safety approach for LLMs.
  • The paper proposes “Guardian-as-an-Advisor (GaaA),” where a guardian predicts a risk label with a brief explanation and prepends that advice to the user query for re-inference while keeping the base model within its original spec.
  • To train and evaluate this workflow, the authors introduce “GuardSet,” a 208k+ multi-domain dataset that includes dedicated robustness and honesty slices alongside harmful/harmless examples.
  • Training uses supervised fine-tuning followed by reinforcement learning to enforce consistency between risk labels and explanations, yielding strong detection performance and better downstream responses when inputs are augmented.
  • A latency study reports that advisor inference costs <5% of base-model compute and adds only 2–10% end-to-end overhead under realistic harmful-input rates, while reducing over-refusal.

Abstract

Hard-gated safety checkers often over-refuse and misalign with a vendor's model spec; prevailing taxonomies also neglect robustness and honesty, yielding safer-on-paper yet less useful systems. This work introduces Guardian-as-an-Advisor (GaaA), a soft-gating pipeline where a guardian predicts a binary risk label plus a concise explanation and prepends this advice to the original query for re-inference, keeping the base model operating under its original spec. To support training and evaluation, GuardSet is constructed, a 208k+ multi-domain dataset unifying harmful and harmless cases with targeted robustness and honesty slices. GuardAdvisor is trained via SFT followed by RL to enforce label-explanation consistency. GuardAdvisor attains competitive detection accuracy while enabling the advisory workflow; when used to augment inputs, responses improve over unaugmented prompts. A latency study shows advisor inference uses below 5% of base-model compute and adds only 2-10% end-to-end overhead under realistic harmful-input rates. Overall, GaaA steers models to comply with the model spec, maintaining safety while reducing over-refusal.