Elon Musk posted June 28, 2026 that Grok 4.5 is in private beta at SpaceX and Tesla on the 1.5T V9 foundation with Cursor data in supplemental training. Training completed May 26, 2026 per reports — a 50% parameter increase from Grok 4.4’s 1T base in roughly one month.
Private beta is restricted to Musk-controlled organizations. “Early evals” have not been shared publicly, submitted to Chatbot Arena, or reproduced by third parties. Internal evaluations at the developer’s own companies do not meet the standard for verified performance claims. The SpaceX-xAI merger gave xAI access to Colossus compute, likely enabling the parameter jump.