Musk: Grok 4.5 Enters Private Beta at Tesla and SpaceX, Built on a New 1.5-Trillion-Parameter Base

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On June 28, Musk announced that xAI's Grok 4.5 has entered internal private beta at Tesla and SpaceX. It's built on the new V9 base model (1.5 trillion parameters), with supplementary training using Cursor's data. Musk says early evaluations approach or even surpass Claude Opus—a claim currently coming from him alone.

Grok 4.5 Runs at His Own Companies First

On June 28, Musk announced on X that xAI's next-generation model Grok 4.5 has entered private beta—not a public release, but running internally at Tesla and SpaceX first. According to reports, it's built on xAI's new V9 base model, with 1.5 trillion parameters, training completed on May 26, a 50% increase over the previous generation Grok 4.4's 1 trillion parameters. Compared with the prior generation, this time Cursor's data was deliberately added in supplementary training—SpaceX previously acquired Cursor's parent company Anysphere for $60 billion—aiming to strengthen the model's chops in coding and technical reasoning.

Numbers Depend on Who's Saying Them

Musk claimed on X that early evaluations show Grok 4.5's performance approaches, and may even surpass, Opus (meaning Anthropic's Claude Opus). This sentence warrants a question mark: it comes from Musk himself, based on internal early evaluations, with no third-party leaderboard and not yet publicly testable, so by convention treat it with skepticism first. Likewise, details like the 1.5 trillion parameters and the Cursor data mostly come from media reports, and it's safer to reconcile them against xAI's official release. He also declared that for the rest of 2026 he plans to release a new model trained from scratch every month. The cadence sounds aggressive, but whether it can be delivered, and whether each one is a real substantive upgrade, still has to wait until the moment it can be publicly tested.

via: Cybernews