SAN FRANCISCO, California: OpenAI plans to stop providing its AI models to Cursor, the coding-tool company acquired by Elon Musk's SpaceX, saying it cannot be confident that SpaceX will use its technology within its terms of service.

The move marks a further escalation in the years-long rivalry between OpenAI CEO Sam Altman and Musk, which culminated earlier this year in a trial over Musk's US$150 billion lawsuit against OpenAI. During the trial, Musk's lawyer said Musk and other witnesses had testified that Altman was a liar, while OpenAI argued that Musk had sought control of the company.

"We are making this choice because we cannot be confident that SpaceX will use our technology within our terms of service, based on our experience with Elon Musk's companies violating contracts," OpenAI said in a blog post.

Musk responded early August 29 on X, writing, "I couldn't care less."

He accused Altman and OpenAI President Greg Brockman of being "untrustworthy," while repeating his assertion that they "stole an open source nonprofit."

Musk had sued OpenAI and Altman for "stealing a charity" by betraying the company's original nonprofit mission for their own enrichment. A federal jury ruled against Musk earlier this year, finding that he had filed the case too late.

Michael Truell, a co-founder of Cursor and now an executive at SpaceX, said on X that the company was speaking with the OpenAI team to resolve the issue.

Hours after OpenAI's announcement, Anthropic, which rivals both firms but has an ongoing partnership with SpaceX, said it planned to increase compute to support Claude models in Cursor, according to Tom Brown, one of the company's co-founders.

OpenAI said in its blog post that X, formerly known as Twitter and now part of SpaceX, had breached the terms of its contract with OpenAI after Musk acquired the platform.

"To work with a large partner like SpaceX, we typically rely on custom contracts to ensure compliance with our terms of service and that the integration provides for safety at scale," OpenAI added.

The ChatGPT maker said it had proposed a shutoff date of November 12, 2026. It said its agreement with Cursor gave it a limited window to cancel the contract following "a change of control."

SpaceX announced in June that it would buy Anysphere, the startup behind Cursor, for $60 billion in an all-stock deal. The acquisition was completed earlier this month.