- Elon Musk announced Grok 4.5 has entered private beta testing at SpaceX and Tesla
- Grok 4.5 is based on xAI's 1.5 trillion parameter V9 foundation model with Cursor data
- Early evaluations show Grok 4.5 may perform close to or exceed Anthropics Claude Opus
Elon Musk announced on Sunday that Grok 4.5, built on xAI's 1.5-trillion-parameter V9 foundation model, has entered private beta testing at SpaceX and Tesla, with early evaluations showing performance close to, and potentially exceeding, Anthropic's Claude Opus.
"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," Musk posted on his X account.
He added that reinforcement learning continues to meaningfully improve the model, and that the "Grok Build" coding harness is "getting better every day." Musk thanked the teams involved in the development, writing, "Nice work by all those involved!"
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.
— Elon Musk (@elonmusk) June 28, 2026
RL is continuing to significantly improve the model, and the Grok Build…
In the same post, Musk said xAI plans to release "completely trained from scratch" new models through SpaceX every month for the rest of the year.
The V9 foundation model, which Musk first disclosed in late May, finished training at 1.5 trillion parameters, roughly three times the size of the 0.5-trillion-parameter "v8-small" model that currently powers Grok's production traffic on X.
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Musk had said at the time that the training run incorporated a substantial volume of data from Cursor, the AI coding assistant SpaceX agreed to acquire for $60 billion earlier this year, with the aim of sharply improving Grok's coding performance.
The model's rollout has been staggered: training completion was confirmed in late May, with subsequent updates pointing to a mid-June public release window for the underlying V9-Medium model. Sunday's post marks the first confirmation that a version branded Grok 4.5 has moved into private testing on Musk's own companies before any wider release.
No independent benchmark results for Grok 4.5 have been published so far.
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