We evaluated Grok 4 Fast (Reasoning) and Grok 4 Fast (Non-Reasoning), and found the following:

• Grok 4 Fast (Reasoning) delivers impressive latency and pricing, comparable to GPT-5 Nano. For example, on Corp Fin, it was half the latency and 10% of the cost compared to Grok 4.
• The Reasoning model significantly outperforms the Non-Reasoning variant. While Grok 4 Fast (Non-Reasoning) did not place in the top 10 on any benchmark, Grok Fast (Reasoning) achieved #3 on both AIME and CorpFin.
• The results highlight the growing performance gap between reasoning and non-reasoning models, particularly on complex benchmarks.

Overall, this is a very performant model from the SpaceXAI team for its price and latency.