OpenAI Cut Off a Billion-Dollar Customer to Avoid Elon Musk

Maxwell Zeff reports that at the start of 2026 Cursor was one of OpenAI's top five customers by revenue, and that by spring OpenAI internally estimated the partnership at more than $1 billion in annualized revenue. Those figures had not been previously reported. Last Friday OpenAI said it would wind down the partnership because it cannot be confident SpaceX will stay inside its terms of service, citing 'experience with Elon Musk's companies violating contracts.'

SpaceX acquired Cursor in a $60 billion deal. Cursor founder Michael Truell, now leading teams at SpaceX, posted that OpenAI's models serve about 5 percent of Cursor user traffic. OpenAI's Thibault Sottiaux replied that token usage is not a proxy for revenue or value. Anthropic cofounder Tom Brown said Claude will stay in Cursor.

Walking away from a billion-dollar run-rate customer is not a terms-of-service footnote. It is OpenAI deciding that Musk-as-counterparty is a bigger risk than the revenue, the developer channel, and the optics of cutting off a tool a lot of its users actually live in. The public reason is contract violation history and an apparent Musk deposition remark that xAI used OpenAI models to train its own. The private reason, which Zeff puts in plain sight, is that Codex and Cursor are already competing for the same seats, and a $60 billion SpaceX owner makes the old coopetition arrangement look naive.

Signal Desk's read: the $1 billion estimate is the number that will travel, and it should. It tells you OpenAI would rather take a visible hit on the eve of a 2027 IPO than keep a pipe into a Musk-controlled product that could distill weights. Distillation risk is the actual fear. Terms of service is the language you use when you cannot say that in a customer email.

Truell's 5 percent line is a counter-narrative, not a rebuttal. If OpenAI models are a small slice of traffic they can still be a large slice of the bill, which is exactly what Sottiaux was pointing at. Anthropic staying in Cursor is the more revealing move. Last year Anthropic cut off Windsurf when OpenAI was rumored to be buying it. Now Claude stays, and Zeff notes Anthropic depends on SpaceX for $45 billion of data center capacity. That is not philosophy. That is a landlord you do not evict.

OpenAI's own startup fund was in Cursor's 2023 seed. It later talked acquisition, never seriously. Truell appeared in GPT-5 launch marketing. This is a relationship that went from investment to partnership to competitor to cutoff in three years, and Musk was the event that forced the last step, not the first.

OpenAI is preparing to go public next year and Zeff cites more than $40 billion in annualized revenue across subscriptions, ChatGPT ads, and Codex. Losing Cursor hurts less than it would have two years ago, which is probably why the company felt it could do this in public.