Anthropic Claude Opus 4.5 vs OpenAI GPT OSS 20B
Detailed comparison for LLMs
On Guardion's LLM vulnerability Benchmark, Anthropic Claude Opus 4.5 is the more secure of the two: Claude Opus 4.5 scores 3.4% and GPT OSS 20B scores 20.0% on attack success rate (ASR) (lower is better). One or both scores are estimated from public safety evaluations pending a Guardion benchmark run.
Head-to-Head Overview
Claude Opus 4.5 is the overall winner in this comparison!
Attack Success Rate (lower is safer)
ASR for Anthropic Claude Opus 4.5 vs OpenAI GPT OSS 20B. Green marks the safer model on each metric. Only the overall score is available for estimated models.
Overall (ASR)
TAP Attack Method (ASR)
Crescendo Attack Method (ASR)
Zero-Shot (ASR)
Key Highlights
- Anthropic Claude Opus 4.5 has a lower Overall (ASR).
Security Profile
Outward is better on every axis.
Frequently asked questions
Is Anthropic Claude Opus 4.5 or OpenAI GPT OSS 20B more secure?
On Guardion's LLM vulnerability Benchmark, Anthropic Claude Opus 4.5 is the more secure of the two: Claude Opus 4.5 scores 3.4% and GPT OSS 20B scores 20.0% on attack success rate (ASR) (lower is better). One or both scores are estimated from public safety evaluations pending a Guardion benchmark run.
What is the attack success rate (ASR) of Claude Opus 4.5 vs GPT OSS 20B?
Claude Opus 4.5 has a 3.4% ASR and GPT OSS 20B has a 20.0% ASR — the share of adversarial prompts that succeed across zero-shot, TAP, and Crescendo attacks. Lower is safer.
How were Claude Opus 4.5 and GPT OSS 20B tested?
Both were red-teamed with the HarmBench framework across zero-shot, TAP (Tree of Attacks with Pruning), and Crescendo multi-turn attacks, scored by Attack Success Rate.