xAI Grok-4 Heavy vs xAI Grok-4.1 Fast Reasoning
Detailed comparison for LLMs
On Guardion's LLM vulnerability Benchmark, xAI Grok-4.1 Fast Reasoning is the more secure of the two: Grok-4 Heavy scores 18.0% and Grok-4.1 Fast Reasoning scores 14.0% 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
Grok-4.1 Fast Reasoning is the overall winner in this comparison!
Attack Success Rate (lower is safer)
ASR for xAI Grok-4 Heavy vs xAI Grok-4.1 Fast Reasoning. 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
- xAI Grok-4.1 Fast Reasoning has a lower Overall (ASR).
Security Profile
Outward is better on every axis.
Frequently asked questions
Is xAI Grok-4 Heavy or xAI Grok-4.1 Fast Reasoning more secure?
On Guardion's LLM vulnerability Benchmark, xAI Grok-4.1 Fast Reasoning is the more secure of the two: Grok-4 Heavy scores 18.0% and Grok-4.1 Fast Reasoning scores 14.0% 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 Grok-4 Heavy vs Grok-4.1 Fast Reasoning?
Grok-4 Heavy has a 18.0% ASR and Grok-4.1 Fast Reasoning has a 14.0% ASR — the share of adversarial prompts that succeed across zero-shot, TAP, and Crescendo attacks. Lower is safer.
How were Grok-4 Heavy and Grok-4.1 Fast Reasoning 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.