arXiv — NLP / Computation & Language · · 3 min read

Guard Vector: Beyond English LLM Guardrails with Task-Vector Composition and Streaming-Aware Prefix SFT

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Computer Science > Computation and Language

arXiv:2509.23381 (cs)
[Submitted on 27 Sep 2025 (v1), last revised 21 Jul 2026 (this version, v2)]

Title:Guard Vector: Beyond English LLM Guardrails with Task-Vector Composition and Streaming-Aware Prefix SFT

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Abstract:We introduce Guard Vector, a safety task vector computed as the parameter difference between a guardrail model (Guard Model) and a same-architecture pretrained language model. Composing this vector with a target language model yields a Target Guard Model (TGM). We then adapt TGM with a streaming-aware approach that combines prefix-based training and evaluation with a classifier that produces a single-token output. With this composition alone, TGM improves classification quality over established Guard Models across standard safety suites and enables language extensibility to Chinese, Japanese, and Korean, requiring neither additional training nor target language labels for this composition step. It also demonstrates model portability across two widely used public guardrail backbones, Llama and Gemma. With prefix SFT (supervised fine-tuning), TGM preserves classification quality under streaming by aligning the behavior between prefix inputs and full-text inputs. The single-token output design increases throughput and reduces latency. Together, these components reduce data and compute requirements while promoting streaming-aware evaluation practices, thereby contributing to a more responsible AI ecosystem.
Subjects: Computation and Language (cs.CL)
Cite as: arXiv:2509.23381 [cs.CL]
  (or arXiv:2509.23381v2 [cs.CL] for this version)
  https://doi.org/10.48550/arXiv.2509.23381
arXiv-issued DOI via DataCite

Submission history

From: Wanjin Park [view email]
[v1] Sat, 27 Sep 2025 16:03:44 UTC (479 KB)
[v2] Tue, 21 Jul 2026 08:03:44 UTC (444 KB)
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