OpenAI announced late Friday that it is ending developers' access to its models on Cursor, following the acquisition of the AI coding startup by Elon Musk's SpaceX earlier this month.
Cursor CEO Michael Truell said, in a post on the SpaceX-owned social network X Friday night: "OpenAI models serve about 5% of Cursor user traffic, and we're speaking with the OpenAI team to resolve this. Cursor was one of the very first users of OpenAI, we've worked closely with their team for years, and we've trusted their platform to be neutral infrastructure for our business."
In their announcement, OpenAI said, "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."
Its "proposed shutoff date" for OpenAI models via Cursor is Nov. 12, 2026. OpenAI also said it would not provide future models to Cursor as it winds down the agreement.
Cursor and OpenAI did not immediately respond to CNBC's requests for comment.
SpaceX completed its $60 billion acquisition of Cursor on Aug. 14, according to financial filings. Before SpaceX went public in June, it had acquired Musk's X and xAI in February.
OpenAI's move away from Cursor, now that SpaceX owns it, is part of a long-running and acrimonious clash between Musk and OpenAI CEO Sam Altman and President Greg Brockman.
In a post on X on Saturday, Musk wrote, "I couldn't care less. Scam Altman and Greg Stockman are utterly untrustworthy," used an expletive to describe them, then repeated his claim that they "stole an open source nonprofit."
Musk sued OpenAI, Altman and Brockman in 2024 after co-founding and helping to fund the AI company as a non-profit research lab in 2015.
Musk left OpenAI's board in 2018 after hiring talent away from the company, cutting off donations he had promised to OpenAI, and clashing with fellow board members over its direction. He later became one of its most prominent critics.
After Musk left, OpenAI launched massively successful AI products, namely ChatGPT, struck partnerships with tech titans including Microsoft, converted its business into a for-profit with a non-profit parent, and raised huge sums of funding.
Musk has argued in court that OpenAI's restructuring violated its founding commitments and has described the change as "stealing a charity." OpenAI disputes his claims. While he lost his lawsuit earlier this year, Musk has vowed to appeal.
As the market for "vibe coding" — or AI-assisted coding tools — heats up, OpenAI is poised to go public next year, while rival Anthropic has been holding preliminary meetings with bankers ahead of a possible IPO this year at an expected valuation as high as $2 trillion, CNBC previously reported.
OpenAI's choice to end developers' access to its models via Cursor is not a first in the industry.
Last June, Anthropic — which is now partnering with SpaceX and renting compute capacity from Musk's company — blocked Windsurf access to its Claude AI models.
Anthropic co-founder and executive Tom Brown wrote in a post on X on Friday night, "Cursor has been a trusted partner of Anthropic since Sonnet 3.5. We'll continue to increase compute to support Claude models in Cursor and are excited for what comes next with them at SpaceX."
His post drew criticism from some technology executives on X, with Replit CEO Amjad Masad reminding Brown of Anthropic's history with Windsurf, and Docker executive Mat Velloso replying, "This was a great opportunity to stay quiet."