  Deploying language models (LMs) necessitates outputs to be both high-quality
and compliant with safety guidelines. Although Inference-Time Guardrails (ITG)
offer solutions that shift model output distributions towards compliance, we
find that current methods struggle in balancing safety with helpfulness. ITG
Methods that safely address non-compliant queries exhibit lower helpfulness
while those that prioritize helpfulness compromise on safety. We refer to this
trade-off as the guardrail tax, analogous to the alignment tax. To address
this, we propose PrimeGuard, a novel ITG method that utilizes structured
control flow.
  PrimeGuard routes requests to different self-instantiations of the LM with
varying instructions, leveraging its inherent instruction-following
capabilities and in-context learning. Our tuning-free approach dynamically
compiles system-designer guidelines for each query. We construct and release
safe-eval, a diverse red-team safety benchmark. Extensive evaluations
demonstrate that PrimeGuard, without fine-tuning, overcomes the guardrail tax
by (1) significantly increasing resistance to iterative jailbreak attacks and
(2) achieving state-of-the-art results in safety guardrailing while (3)
matching helpfulness scores of alignment-tuned models. Extensive evaluations
demonstrate that PrimeGuard, without fine-tuning, outperforms all competing
baselines and overcomes the guardrail tax by improving the fraction of safe
responses from 61% to 97% and increasing average helpfulness scores from 4.17
to 4.29 on the largest models, while reducing attack success rate from 100% to
8%.
  PrimeGuard implementation is available at
https://github.com/dynamofl/PrimeGuard and safe-eval dataset is available at
https://huggingface.co/datasets/dynamoai/safe_eval.
