Anthropic Claude Opus 4.5 vs xAI Grok-4 Heavy
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 Grok-4 Heavy scores 18.0% 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 xAI Grok-4 Heavy. 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 xAI Grok-4 Heavy 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 Grok-4 Heavy scores 18.0% 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 Grok-4 Heavy?
Claude Opus 4.5 has a 3.4% ASR and Grok-4 Heavy has a 18.0% 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 Grok-4 Heavy 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.