Elon Musk on Sunday, 28 June confirmed that xAI's latest artificial intelligence model, Grok 4.5, has entered private beta testing at SpaceX and Tesla — marking the first verified deployment of the model within Musk's own companies ahead of a broader public rollout.

What Musk Announced

In a post on social media platform X, Musk said Grok 4.5 is built on xAI's 1.5-trillion-parameter V9 foundation model and has received supplemental training using data from AI coding assistant Cursor. He wrote: '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.'

The reference to 'Opus' points to Anthropic's Claude Opus, widely regarded as one of the most capable large language models currently available. Musk's claim that Grok 4.5 may match or surpass it has not been independently verified.

The V9 Model and Its Scale

The V9 foundation model, which Musk first disclosed in late May, completed training with 1.5 trillion parameters — roughly three times the size of the 0.5-trillion-parameter 'v8-small' model that currently handles Grok's production workloads on X. The jump in scale signals a significant architectural step-up for xAI's model family.

The integration of Cursor data was intended to substantially enhance Grok's coding capabilities. SpaceX agreed to acquire Cursor earlier this year in a deal reportedly valued at $60 billion.

Reinforcement Learning and the 'Grok Build' Harness

Musk noted that reinforcement learning continues to improve the model's capabilities over time. He also highlighted that xAI's internal coding system — referred to as the 'Grok Build' coding harness — is growing more effective with each iteration. He thanked the teams involved in the model's development.

Monthly AI Releases Planned Through SpaceX

In a notable forward commitment, Musk revealed that xAI intends to release new AI models 'completely trained from scratch' through SpaceX every month for the remainder of 2025, suggesting a sharply accelerated development cycle. This cadence, if maintained, would be among the fastest public model release schedules in the industry.

Rollout Timeline

The V9 model's rollout has proceeded in stages. Musk confirmed training completion in late May, with subsequent signals pointing to a mid-June public release window for the underlying V9-Medium model. Sunday's announcement is the first confirmation that a version officially branded as Grok 4.5 has advanced to private testing — the step immediately preceding a wider release.

Whether Grok 4.5 reaches public availability on schedule will depend on outcomes from the ongoing SpaceX and Tesla deployments, where real-world usage typically surfaces edge cases that lab evaluations miss.