OpenAI is leaving Cursor

Last night OpenAI posted on X that it is leaving Cursor.

The post is short. The statement is not. They are telling SpaceX they will wind down the contract that gives Cursor OpenAI’s models. The date they propose is 12 November. They say that is the most notice the agreement allows.

What they care about most, they write, are the developers who use those models inside the editor. They are ready to go “above and beyond” to help them. The message is not for the Cursor team. It is for whoever signs the contract now: SpaceX.

Fifteen days after closing #

On 14 August SpaceX closed its purchase of Anysphere, the company behind Cursor. The deal was signed on 16 June, days after SpaceX’s IPO. In the 8-K the implied value is $60 billion, all stock. I wrote about that close in Cursor now belongs to SpaceX.

Fifteen days later OpenAI uses the change-of-control clause. They have a limited window to cancel. They use it. Until 12 November they leave what is already there. What comes next, they do not. Including Astra, the model they have not shipped yet.

They have worked with Cursor for almost four years. The OpenAI Startup Fund put money into the 2023 seed round. They say they respect the product. And they are still leaving.

They are not talking about quality. They are talking about trust #

OpenAI does not argue about the editor. It does not argue about price. It writes that it cannot be confident SpaceX will use its technology within its terms, “based on our experience with Elon Musk’s companies violating contracts.”

They rest that on two precedents.

The first: after Musk bought Twitter, he cut off OpenAI’s access to the network’s data. OpenAI counts that as a broken contract. Twitter is now X, and X is part of SpaceX.

The second: earlier this year, in the trial Musk lost against OpenAI, he admitted under oath that xAI had “partly” distilled OpenAI models to train its own. OpenAI’s terms forbid that. xAI is now inside SpaceX too.

OpenAI says that with a partner this large they rely on custom contracts, so the rules are kept and the integration is safe at scale. And that Astra forces them to be stricter.

It is a polite way of saying: we will not feed the rival’s editor.

Tibo, from Codex at OpenAI, reduced it to one word: trust. And, so nobody would get the wrong idea, he added what still works: your own API key, and OpenAI’s IDE extensions for Cursor. They are not kicking you out of the editor. They are shutting off the wholesale tap. The one with the discount, reserved capacity, and the model on day one.

That did not calm anyone. Some people remember OpenAI just bragging that it does not block the harness you choose. One user said it to their face: “You just lied.” The legal distinction is real — they are not blocking the editor, they are blocking the contract — but in practice a Cursor user stops getting GPT as a first-class model at partner pricing, and starts paying list API rates or moving to Codex.

Truell’s 5% #

Michael Truell, a Cursor co-founder and now a SpaceX executive, replied in under an hour.

They are sorry OpenAI put out a note saying that in three months they will block Cursor users from OpenAI models. OpenAI’s models, he says, are about 5% of traffic. They are talking to the OpenAI team to resolve it.

People at Cursor treated the 5% as a slap. It is. It is also a number OpenAI will not want to hear: if it really is 5%, the cutoff hurts OpenAI more than Cursor. If it is not, Truell just said in public that GPT no longer runs the editor OpenAI helped push.

The line that matters is another one: Cursor was one of the first OpenAI customers. They have worked together for years. And they had trusted that platform to be “neutral infrastructure” for their business.

That is the fight. OpenAI no longer offers itself as a pipe. Cursor can no longer sell itself as the editor where everyone fits.

Anthropic stays. Elon posts two rockets. Then he insults #

Tom Brown, Anthropic cofounder and chief compute officer, did not wait. Cursor has been a trusted partner since Sonnet 3.5. They will keep adding compute for Claude inside Cursor. And they are “excited” for what comes next with them at SpaceX.

Elon did not write an essay. He quoted Brown and posted two rockets.

Hours later, when someone passed him OpenAI’s note, he did write: “I couldn’t care less. Scam Altman and Greg Stockman are utterly untrustworthy assholes who stole an open source nonprofit.”

(OpenAI’s president is named Greg Brockman. Musk knows that.)

The map makes sense, even if it is ugly. Anthropic has a datacenter deal with SpaceXAI. OpenAI leaves because it does not trust the owner. Anthropic stays because the owner supplies the racks. In January they already cut Claude off from xAI staff who used it inside Cursor. Not from the product. From the rival.

Amjad Masad, of Replit, reminded Brown in the same thread: maybe you changed your ways, but we all remember what you did to Windsurf, which was infinitely nastier. More likely you cannot do that here because you need the compute.

He has the timeline right. In June 2025, when news leaked that OpenAI was buying Windsurf, Anthropic cut Windsurf’s first-party access to Claude with less than a week of notice. Jared Kaplan said it in public: “it would be odd for us to be selling Claude to OpenAI.” OpenAI’s cutoff of Cursor is the same move, with more notice and worse copy. The difference is that Anthropic is now on the other side of the table, and Replit is working the gap: OpenAI for free on Replit, and money for businesses that want to leave Cursor.

On X almost no one is surprised. “You could see it coming.” “The problem is Musk.” “They are protecting their business.” It is not a thread of people mourning a model. It is people who assume the editor is no longer everyone’s. And people who, correctly, point to the wrapper precedent: if your product lives by reselling someone else’s model, a change of control can take the model away.

This is not about a plugin #

Musk and Altman have been in court for years. Musk sued OpenAI for $150 billion. A federal jury sided with OpenAI: the case was filed too late. Distillation came out in that same trial.

OpenAI tried to buy Cursor and could not. Then it tried to buy Windsurf and the deal fell apart. Google took the founders. Cognition took the rest. OpenAI built Codex. Anthropic built Claude Code. Cursor, which had been the place where all those models fit, sold itself to SpaceX for $60 billion because it needed compute so it would not depend on the labs it was reselling.

Musk, in his first all-hands with the Cursor staff, said he was not used to losing. That Tesla and SpaceX dominate their markets and Grok does not. That they had to catch Anthropic.

Buying Cursor put the editor inside that war. SpaceX did not buy a notepad. It bought the place where many of us write code with a model next to it. OpenAI does not want its next model living there. Cursor does not want the model picker to become a checkpoint.

The person who pays is not Altman or Musk. It is whoever has the editor open and a model selected in the dropdown.

What changes for me #

I work in Cursor. This is not someone else’s news. Although, to be honest, I barely use OpenAI’s models. Not even Claude. Grok 4.6 solves almost everything for me.

12 November does not turn the editor off. It turns off the tap Cursor had with OpenAI. It does not change my day to day. The product stays. Claude stays, and Anthropic says it will put more in. Gemini stays, if Google does not do the same. Grok already lives in the editor, now that Cursor belongs to SpaceX. If you want GPT, you still have the API key, Codex, or waiting for Truell to close something.

What ends is the idea that this place was a Swiss Army knife.

A code editor had become the place where you asked whoever you wanted. That was the product: not marrying a lab. SpaceX buys, OpenAI leaves, Anthropic plants a flag, Replit offers a move. The promise of not marrying a lab breaks on one side and holds on the other, and not out of virtue: out of who gives you the racks.

Until 12 November there is nothing to do. It is worth not forgetting the date. And not forgetting that the model you use does not belong to the editor. It belongs to whoever still lets you use it.

OpenAI’s note is here. The post is here. Truell’s reply is here. Elon’s is here.