OpenAI told SpaceX this week that it will stop supplying models to Cursor, the AI coding tool SpaceX agreed to buy in June for $60 billion in stock. The cutoff date is Nov. 12, the longest notice the contract allows. A person familiar with the matter said OpenAI delivered the notice Aug. 28, days after SpaceX completed its acquisition of Cursor’s parent company, Anysphere, on Aug. 15.
The trigger was a change-of-control clause. OpenAI’s contracts with Anysphere included a provision that let either side exit if ownership changed hands, according to people familiar with the terms. Once the deal closed, OpenAI had a decision to make about continuing to serve a company now controlled by Elon Musk.
The company’s answer was no. In its notice, OpenAI said it could not be confident SpaceX would abide by its terms of service, pointing to its record of dealings with Musk’s companies. OpenAI cited two prior disputes: Musk’s decision after buying Twitter in 2022 to cut off OpenAI’s access to Twitter data, and allegations that xAI trained its Grok models on data distilled from OpenAI’s products without permission. Musk has denied the distillation claims.
Musk responded on X with a terse dismissal. He said he did not care, and called OpenAI’s chief executive, Sam Altman, and president, Greg Brockman, untrustworthy. The post drew immediate attention from developers who had been watching the feud for signs it would touch the tools they use every day.
Cursor’s co-founder, Michael Truell, struck a calmer note. In a post, he said OpenAI models accounted for roughly 5 percent of Cursor’s AI traffic and that the two sides were still talking. Cursor has long offered models from multiple providers, including Anthropic’s Claude and Google’s Gemini, and Truell’s numbers suggested the loss would sting less than a full dependency.
Anthropic moved quickly to capitalize. The company said it was increasing compute support for Claude models inside Cursor, positioning itself as the beneficiary of the rift. For Anthropic, whose models are already widely used in coding, the fight between OpenAI and Musk hands it a chance to expand share inside one of the most popular developer tools in the world.
The dispute is the latest turn in a feud that has followed Musk and Altman for a decade. They co-founded OpenAI in 2015, split over its direction, and have since traded lawsuits, regulatory complaints and public insults. Musk’s lawsuit over OpenAI’s transition to a for-profit structure is still pending in court. The Cursor fight adds a commercial dimension: Musk now controls a tool used by millions of developers, and OpenAI has decided it would rather lose that business than depend on him.
For Cursor, the practical impact may be limited in the near term. Developers mostly pay for the tool, not for the underlying model, and Cursor can route traffic to Claude or other providers without interrupting service. But the episode shows how quickly the model-supply chain has become a map of alliances and grudges. A startup that builds on another company’s models now faces a new risk: the model provider may not like who ends up owning you.
The Nov. 12 date gives both sides time. SpaceX could appeal, negotiate, or simply let the deadline pass and accept the switch. Truell said talks were continuing, and people familiar with the discussions said no final agreement had been reached as of this week.
OpenAI declined to comment beyond its notice. SpaceX and Anysphere did not respond to requests for comment.
The episode is a window into how the AI industry is dividing into camps. Model makers are choosing partners and enemies with the care of nations forming alliances, and the tools that developers rely on are becoming the territory on which those battles are fought. Cursor’s developers, most of whom just want their code reviewed faster, are watching from the middle.
For the broader software market, the dispute raises a question that has followed the industry since the first wave of consolidation: what happens to a product when its supplier changes hands? Cursor’s growth was built in part on access to the best models from every lab, a neutrality that made it a favorite among developers. Whether it can keep that neutrality while owned by Musk is now an open question, and the answer will be written in the share of traffic that stays with the tool after November.
The timing of the notice is notable for another reason. SpaceX’s purchase of Anysphere was one of the largest acquisitions of a developer tool ever, and it put a company best known for rockets and satellites in control of software used by engineers at nearly every major technology firm. Model providers that once competed for Cursor’s business now face a binary choice: keep serving a Musk-owned product, or follow OpenAI’s lead and walk away. Anthropic’s quick decision to add capacity suggests it sees the situation as an opportunity, not a dilemma.
