Grok 4.5 enters internal testing phase at SpaceX and Tesla

Elon Musk on Sunday announced that xAI's latest artificial intelligence model, Grok 4.5, has entered private beta testing at SpaceX and Tesla, marking the first confirmed deployment of the model within Musk's companies ahead of a wider release.

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

According to Musk, early evaluations indicate that the model's performance is close to, and may even exceed, 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 wrote.

He added that reinforcement learning continues to improve the model's capabilities and said that xAI's internal coding system, referred to as the "Grok Build" coding harness, is becoming more effective over time. Musk also thanked the teams involved in developing the model.

Musk further revealed that xAI intends to release new AI models that are "completely trained from scratch" through SpaceX every month for the remainder of the year, suggesting an accelerated development cycle for the company's AI efforts.

The V9 foundation model, which Musk first disclosed in late May, completed training with 1.5 trillion parameters. The model is roughly three times larger than the 0.5-trillion-parameter "v8-small" model that currently handles Grok's production workloads on X.

At the time, Musk had said the training process included a significant amount of data from Cursor, the AI coding assistant that SpaceX agreed to acquire earlier this year in a deal valued at $60 billion. The integration of Cursor data was intended to significantly enhance Grok's coding capabilities.

The rollout of the V9 model has proceeded gradually. Musk confirmed the completion of training in late May, while subsequent updates had pointed to a mid-June public release window for the underlying V9-Medium model. Sunday's announcement marks the first indication that a version officially branded as Grok 4.5 has advanced to private testing.