News 📢

• 🎉 2026/07/08: Content Binary Guard paper was accepted to COLM 2026! 🎉
• 📑 2025/10/01: Published a Content Binary Guard Research Paper
• 📘 2025/09/24: Published a Responsible AI Technical Report
• ⚡️ 2025/09/24: Released SafetyGuard Model collection on Hugging Face🤗.

Overview

Description

SafetyGuard :: Content Binary Guard is a streaming-aware safety classifier built with Llama.
For more technical details, please refer to our Research Paper.

What it does

• Task: Classify model responses (not prompts) as SAFE or UNSAFE.
• Interface: Single-token output using reserved label tokens: <SAFE>, <UNSAFE>.
• Streaming: Evaluate growing prefixes of a response (default ~100 characters per step) and early-terminate at the first <UNSAFE>.

Recommended inference settings

• Deterministic decode: temperature=0
• Unsafe threshold τ = 0.5 over the two label-token logits (tune for your risk tolerance)
• Use the model’s tokenizer; ensure the exact label tokens <SAFE> and <UNSAFE> exist

Quickstart

Assumes you are serving the model with vLLM (e.g., vllm serve …) and exposing an OpenAI-compatible API at http://localhost:8000/v1.

import math
from openai import OpenAI

MODEL_ID = "K-intelligence/Llama-SafetyGuard-Content-Binary"  # replace with your repo id
client = OpenAI(base_url="http://localhost:8000/v1", api_key="EMPTY")  # vLLM default

SYSTEM_PROMPT = """
Task: Check if the LAST user message contains unsafe content.
Respond with only one word: safe or unsafe.
""".strip()

def classify(text: str, tau: float = 0.5):
    resp = client.chat.completions.create(
        model=MODEL_ID,
        messages=[
            {"role": "system", "content": SYSTEM_PROMPT},
            {"role": "user",   "content": text},
        ],
        max_tokens=1,          # single-token decision
        temperature=0.0,       # deterministic
        logprobs=True,
        top_logprobs=2,
    )
    top2 = resp.choices[0].logprobs.content[0].top_logprobs
    probs = {t.token.strip(): math.exp(t.logprob) for t in top2}
    p_safe   = probs.get("<SAFE>",   0.0)
    p_unsafe = probs.get("<UNSAFE>", 0.0)

    label = "UNSAFE" if p_unsafe >= tau else "SAFE"
    return label, {"safe": p_safe, "unsafe": p_unsafe}

print(classify("…LLM response text…"))

Streaming integration

Important: Streaming means your generator (e.g., chat model) emits text progressively. You maintain a cumulative buffer and call the classifier at fixed character steps (e.g., every 100 chars). The classifier does not split text; it only classifies what you send.

def guard_stream(response_chunks, step_chars: int = 100, tau: float = 0.5):
    """
    response_chunks: iterable of text chunks from your generator (e.g., SSE/WebSocket).
    We maintain a cumulative buffer and classify at {step_chars, 2*step_chars, ...}.
    """
    buf = ""
    next_cut = step_chars

    for chunk in response_chunks:
        buf += chunk

        # Check at monotone prefix cuts (cumulative)
        while len(buf) >= next_cut:
            label, scores = classify(buf, tau=tau)
            if label == "UNSAFE":
                return {
                    "label": label,
                    "scores": scores,
                    "prefix_len": next_cut,
                    "text_prefix": buf[:next_cut],
                }
            next_cut += step_chars

    # Final check on the full response (if needed)
    label, scores = classify(buf, tau=tau)
    return {
        "label": label,
        "scores": scores,
        "prefix_len": len(buf),
        "text_prefix": buf,
    }

Tip: Keep your step_chars consistent with your training/evaluation setup (e.g., ~100 chars) to maximize parity with offline metrics.

Intended use

• Guardrail classifier for LLM responses in production systems that render tokens progressively.
• Also works in offline (full-text) mode—just send the entire response once.

AI Risk Taxonomy

Evaluation

Metrics

• F1: Binary F1 with UNSAFE as the positive class (harmonic mean of UNSAFE precision and recall; higher F1 indicates better classification quality).
• Balanced Error Rate (BER): 0.5 × (FPR + FNR) (lower BER indicates better classification quality).
• ΔF1: Difference between streaming and offline results, calculated as F1(str) − F1(off).
• off = Offline (full-text) classification.
• str = Streaming classification.
• Evaluation setup: step_chars=100, threshold τ=0.5, positive class = UNSAFE.

Harmlessness Evaluation Dataset

KT proprietary evaluation dataset

Kor Ethical QA

Kor Ethical QA (open dataset)

Kor Ethical QA (public dataset) is included as a reproducible cross-check on open data. The recent multilingual guardrails (DuoGuard, PolyGuard, Qwen3Guard) were benchmarked on the streaming Harmlessness dataset above.

Streaming Efficiency

Measured on the Harmlessness Evaluation Dataset (streaming regime, step_chars=100), same runtime, steady-state. Efficiency is hardware- and serving-dependent, so the exact environment is reported below.

Environment

• GPU: NVIDIA H100 80GB HBM3 (CUDA 12.2) · CPU: Intel Xeon Platinum 8480C (96c/96t) · Ubuntu 24.04.3, Python 3.12
• Serving: vLLM 0.8.5.post1 (OpenAI-compatible), BF16, tensor-parallel size 1, --max-model-len 4096 --max-num-seqs 64 --gpu-memory-utilization 0.90
• Load: concurrency {200 / 100 / 10} = client-side simultaneous requests (not a fixed model batch size; vLLM forms dynamic batches). QPS = queries/s, TPS = tokens/s, Latency = per-request end-to-end.

Columns show values at concurrency {200 / 100 / 10}. All numbers are from the paper (Table 4).

More Information

Limitations

• The training data for this model consists primarily of Korean. Performance in other languages is not guaranteed.
• The model is not flawless and may produce misclassifications. Since its policies are defined around KT risk categories, performance in certain specialized domains may be less reliable.
• No context awareness: the model does not maintain conversation history or handle multi-turn dialogue.

License

This model is released under the Llama 3.1 Community License Agreement.

Citation

@misc{lee2025guardvectorenglishllm,
      title={Guard Vector: Beyond English LLM Guardrails with Task-Vector Composition and Streaming-Aware Prefix SFT}, 
      author={Wonhyuk Lee and Youngchol Kim and Yunjin Park and Junhyung Moon and Dongyoung Jeong and Wanjin Park},
      year={2025},
      eprint={2509.23381},
      archivePrefix={arXiv},
      primaryClass={cs.CL},
      url={https://arxiv.org/abs/2509.23381}, 
}

Contact

Technical Inquiries: responsible.ai@kt.com