Model Details
GPT-OSS-Safeguard-20B
Quick answer: GPT-OSS-Safeguard-20B is OpenAI's open-weights safety classifier built on the gpt-oss-20b mixture-of-experts architecture (20B total, 3.6B active parameters), using explicit chain-of-thought reasoning to classify content against a supplied policy rather than a fixed label set. It leads on refusal-detection tasks in Mistral's Shieldstral comparison, reflecting its reasoning-based design.
At a Glance
Where it leads: Refusal detection (WildGuardTest Refusal, XSTest Refusal, PolyGuard Refusal) and response-harm classification, likely benefiting from explicit reasoning traces before classification. Where it lags: Multimodal safety tasks — it has no vision encoder, so it cannot be scored on VLGuard, UnsafeBench, or LlavaGuard. Best for: Teams that want an open-weights, policy-adaptive classifier with reasoning transparency and don't need multimodal support.
What GPT-OSS-Safeguard-20B Is
GPT-OSS-Safeguard-20B is a fine-tune of OpenAI's open-weights gpt-oss-20b model, adapted specifically for policy-based content classification. Rather than fixed categories, it takes a natural-language policy and content as input and reasons step-by-step (using reasoning_effort=high in top benchmark configurations) before producing a classification — a design point similar in spirit to Shieldstral's policy-adaptive approach but built on a larger, reasoning-capable base model.
Specifications
| Field | Value |
|---|---|
| Organization | OpenAI |
| Parameters | 20B total, 3.6B active (MoE) |
| Base model | gpt-oss-20b |
| License | Apache 2.0 |
| Modality | Text only |
Pricing
Open weights, free to download. No OpenAI-hosted API pricing published specifically for this safety classifier variant.
Public Benchmark Scores
Scores from Mistral AI's Shieldstral model card, shown for context. Not Benchgen measurements. reasoning_effort=high.
| Benchmark | Score |
|---|---|
| WildGuardTest (Prompt) | 87.3% |
| WildGuardTest (Response) | 81.8% |
| WildGuardTest (Refusal) | 93.8% |
| HarmBench (Prompt) | 94.5% |
| XSTest (Refusal) | 97.4% |
| PolyGuard (Refusal) | 91.7% |
Related Models & Benchmarks
Frequently Asked Questions
What is GPT-OSS-Safeguard-20B?
OpenAI's open-weights, reasoning-based safety classifier built on gpt-oss-20b, using chain-of-thought reasoning to apply natural-language safety policies.Is it multimodal?
No — it's text-only and does not report scores on image-based safety benchmarks.Is it open source?
Yes, released under Apache 2.0.Scores sourced from Mistral AI's Shieldstral model card, shown for context. Last updated 2026-08-12.
Benchmark Leaderboards
This model isn’t on any benchmark leaderboard yet.