xAI: Grok 4.1 Fast

xAI: Grok 4.1 Fast, released on November 19, 2025, is positioned as xAI's premier agentic tool-calling model, excelling in applications like customer support and deep research, supported by a substantial 2M context window. This model consistently ranks among the fastest, achieving an Infinityth percentile across 8 benchmarks, indicating exceptional speed. While no cost data is available, suggesting potential free tier usage, its reliability is strong with a 94% success rate across 8 benchmarks. In terms of benchmark performance, Grok 4.1 Fast demonstrates perfect accuracy in Email Classification and Ethics, with the former also noted for its efficiency and value. It shows strong performance in General Knowledge (99.5% accuracy) and respectable Instruction Following (73.7% accuracy). However, a significant weakness is its 0.0% accuracy in Hallucinations (Baseline), indicating a complete failure to acknowledge uncertainty. Performance in Coding (75.0% accuracy) and Mathematics (82.0% accuracy) is moderate, while Reasoning (76.0% accuracy) is solid. Its key strengths lie in speed, reliability, and perfect accuracy in specific classification and ethical reasoning tasks. The primary area for improvement is its tendency to hallucinate rather than indicate uncertainty.