Elon Musk’s generative artificial intelligence company xAI unveiled its new reasoning model late on Friday, known as Grok 4 Fast.
“We used large-scale reinforcement learning to maximize the intelligence density of Grok 4 Fast,” xAI said in a post on its website. “In our evaluations, Grok 4 Fast achieves comparable performance to Grok 4 on benchmarks while using 40% fewer thinking tokens on average.”
Like other reasoning models, such as OpenAI’s GPT-5, Grok 4 Fast switches between a smart and cost-effective model, and a deeper reasoning model, while also offering responses via its “non-reasoning model.”
According to recently released findings from LMArena, xAI said Grok 4 Fast outperforms models such as OpenAI’s o3-search, Google’s (GOOG) (GOOGL) Gemini 2.5 Pro grounding, GPT-5-search and others, citing its “superior reasoning efficiency and intelligence density enable it to surpass much larger models on real-world, search-related tasks.”
Last week, it was reported that xAI was in talks to raise $10B at a $200B valuation. However, Musk responded to that and said xAI “is not raising any capital right now.” Musk has previously said that Tesla (NASDAQ:TSLA) could invest in xAI.