Elon Musk’s xAI just dropped its biggest model yet into the hands of engineers at two of his other companies. Grok 4.5, a 1.5-trillion-parameter behemoth built on the V9 foundation model, entered private beta at SpaceX and Tesla on June 28, 2026.
Early internal evaluations suggest the model’s performance is close to, or potentially exceeds, Anthropic’s Opus. That’s a bold claim for a model that hasn’t even left the building yet, but the decision to test it inside two of the world’s most engineering-intensive companies tells you something about xAI’s confidence level.
What makes Grok 4.5 different
The headline number is 1.5 trillion parameters. For context, that’s a 50% jump from Grok 4.4, which shipped with 1 trillion parameters in late May 2026.
Grok 4.5 incorporates supplemental training data from Cursor, the AI-powered code editor that has become a favorite among developers. Training on Cursor data means the model has been exposed to vast amounts of real coding workflows, debugging patterns, and software architecture decisions.
