In a message on X, Musk indicated that the move was prompted by “strong positive feedback from customers” who evaluated the model prior to its broader launch.
Musk characterized Grok 4.5 as an “Opus-class” AI model, noting that it is quicker, more token-efficient, and less expensive to operate compared to similar models. Nonetheless, he did not provide further technical specifications or pricing information.
What is Grok 4.5?
Musk explained that Grok 4.5 is constructed on xAI’s latest V9 foundation model, which features approximately 1.5 trillion parameters, along with supplementary training using data from Cursor, an AI-driven coding assistant. He mentioned that initial internal assessments indicate Grok 4.5’s performance is comparable to, or maybe even exceeds, that of Opus, the leading AI model from Anthropic.
He added that the model continues to evolve through reinforcement learning. “RL is significantly enhancing the model, and the Grok Build harness improves every day,” he remarked.
Grok 4.5, based on our 1.5T V9 foundation model, with Cursor data added in supplemental training, is now in private beta at SpaceX & Tesla. Early evals show performance close to, perhaps exceeding Opus.
RL is continuing to significantly improve the model, and the Grok Build…
— Elon Musk (@elonmusk) June 28, 2026
Grok’s users percentage
The public launch of Grok 4.5 comes at a critical time for xAI as it seeks to increase its user base for the AI chatbot. Data from app analytics firm Apptopia indicates that the average daily active users of the Grok app in the US declined by almost 28% from April to June. During this period, its share of the AI chatbot market also fell from 10.6% to 8.7%.
Grok software upgrade
Musk stated that xAI is also in the process of upgrading the software that powers Grok. The company anticipates significant enhancements over the next three months by rewriting portions of Grok’s software in C and C++. Musk also mentioned that xAI is optimizing Grok for better compatibility with Nvidia’s GB300 AI chips.
OpenAI GPT models
In late June, OpenAI unveiled its new GPT-5.6 AI model family, although access was restricted to a select group of partners for testing before the broader rollout. The company announced that GPT-5.6 Sol, Terra, and Luna will be available to the public on Thursday.
