What Happened
AI · Platform Risk · Software Engineering · Investment · News Analysisstatement of 28 Aug 2026 · record to 30 Aug 2026
A change of control, a cancellation clause · and the numbers neither side put together
OpenAI Cuts Off Cursor: What Stops, and What Doesn't
Fourteen days after SpaceX completed its $60 billion purchase of Cursor's parent, OpenAI gave notice that it will stop supplying models to the coding tool on 12 November 2026. Its stated ground is not anything Cursor has done, but what it expects of Cursor's new owner. Two facts that appear nowhere in that statement change how much of it matters: Cursor puts OpenAI at about 5% of its traffic, and the cut-off leaves developers' own API keys working.
The figures Who published each one is part of what it is worth
- 76days of notice — which OpenAI calls the maximum its contract allows
- ~5%of Cursor user traffic served by OpenAI models, according to Cursor's chief executive
- 14days between the acquisition closing and the notice
- $60bnSpaceX paid for Anysphere, Cursor's parent, in stock
- 3times since Jun 2025 that one AI lab has cut another company off from its models
The record, graded Standing first, and the rows sorted by it
| Standing | What | Where it is on record |
|---|---|---|
| Confirmed | On 28 August 2026 OpenAI said it had notified SpaceX that it intends to wind down the contract supplying its models to Cursor, proposing a shutoff of 12 November 2026, and that it will not provide future models to Cursor in the meantime. | OpenAI's own published statement. |
| Confirmed | The stated ground is that OpenAI “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.” No breach by Cursor is alleged by anyone. | OpenAI's statement, quoted identically by two outlets. |
| Confirmed | SpaceX acquired xAI on 2 February 2026 in an all-stock deal valuing the combination at about $1.25 trillion; xAI had itself acquired X, formerly Twitter, in March 2025. Both of OpenAI's phrases — “Twitter, now part of SpaceX” and “xAI, now also part of SpaceX” — follow from those two deals. | CNN and CNBC on the merger; contemporaneous reporting on the X deal. |
| Confirmed | Cursor's co-founder and chief executive Michael Truell said publicly that OpenAI models serve about 5% of Cursor user traffic, that talks with OpenAI are under way, and that Cursor “trusted their platform to be neutral infrastructure for our business.” | His own post, quoted in matching form by two outlets. |
| Confirmed | The cut is not total. OpenAI's Thibault Sottiaux said Cursor users may still supply their own OpenAI API keys, and that OpenAI will keep providing access through its own IDE extensions for Cursor. “It boils down to trust,” he said. | THE DECODER, quoting him directly. Absent from OpenAI's own post. |
| Confirmed, not verifiable here | OpenAI's two cited precedents: that Musk cut off its Twitter data licence — about $2 million a year for the full feed — after judging the price too low in December 2022; and that he admitted under oath that xAI trained Grok on other labs' model outputs, which OpenAI's terms forbid. | The sworn admission is reported consistently by two outlets; the Twitter licence rests on one account. |
| Unconfirmed | Whether SpaceX would in fact have breached the terms. OpenAI's ground is that it cannot be confident — a forecast about future conduct, drawn from past conduct by other companies now under the same owner. | Nothing beyond the forecast itself is offered. |
| Unconfirmed | Whether the 5% figure is accurate. It is Cursor's own, it is the only figure published, and OpenAI has not disputed it — but it is also a number an interested party has reason to state favourably. | No independent measurement exists. |
| Not public | The terms of the change-of-control clause, beyond OpenAI's description of “a limited time window to cancel”; and the exact day the acquisition closed, reported as 13 or 14 August 2026. | Neither company has published the contract; two outlets give different closing days. |
Timeline
How Cursor came to be owned by SpaceX Two of these entries are not about Musk at all
- Mar 2025xAI acquires X, formerly Twitter, in an all-stock deal.
- Jun 2025Anthropic blocks the coding tool Windsurf from its Claude models, after reports that OpenAI wanted to acquire Windsurf. The same shape as what would happen to Cursor fourteen months later.
- Aug 2025Anthropic revokes OpenAI's own Claude API access, after OpenAI teams used Claude for internal benchmarks ahead of the GPT-5 launch.
- 2 Feb 2026SpaceX acquires xAI, all-stock, valuing the combination at about $1.25 trillion. X comes with it.
- 18 May 2026A jury finds for OpenAI in Musk's suit — on the ground that his claims fell outside a three-year limitation period, not on their merits. Musk calls it a “calendar technicality” and says he will appeal. His sworn admission about xAI's use of other labs' model outputs comes from this case.
- 16 Jun 2026SpaceX agrees to buy Anysphere, Cursor's parent, for $60 billion in stock.
- 7 Aug 2026OpenAI slows work on Astra, saying internal evaluations mean it can no longer rule out the Critical cybersecurity level in its own Preparedness Framework.
- mid-Aug 2026The Cursor acquisition closes, reported as 13 or 14 August. This opens the limited window in which OpenAI's contract lets it cancel after a change of control.
- 28 Aug 2026OpenAI gives notice, proposing 12 November. Truell replies the same period with the 5% figure; Musk posts “I couldn't care less”; Anthropic's Tom Brown says his company will add compute for Claude in Cursor.
- 12 Nov 2026The proposed shutoff date, 76 days after the notice. Cursor may choose an earlier one.
What has no date Three of them, and one is the thing everybody wants to know
The day the acquisition closed is given as 13 August by one trade report and 14 August by another outlet, and neither company has said. The month of Musk's sworn admission is likewise unsettled: accounts place his testimony at both a February deposition and the May trial, and this page therefore dates it only to the case. The third gap is the one that decides the story. Truell says talks with OpenAI are under way and OpenAI says Cursor may pick an earlier date than 12 November; nobody has said what either side is asking for, or whether the date will move. Everything on this page describes a proposal with 76 days to run.
The Argument
A forecast, not an accusation What OpenAI says, and what answers it
OpenAI's case rests on a distinction worth stating plainly: it does not allege that Cursor has done anything wrong. The ground is that OpenAI “cannot be confident” about the future conduct of Cursor's new owner, reasoning from what other companies now under that owner have done. It offers two instances. One is a sworn admission by Elon Musk, in the suit he brought against OpenAI, that xAI trained Grok on other labs' model outputs — distillation, which OpenAI's terms forbid. The other, carried by a single account, is that after buying Twitter he cut off OpenAI's roughly $2-million-a-year licence to the full tweet feed, having judged the price too low. OpenAI adds a forward-looking reason: with its upcoming Astra model there is “a new level of accountability” to ensure terms are kept. Against this stand two facts the statement does not carry. Cursor's chief executive, Michael Truell, says OpenAI models serve about 5% of Cursor user traffic. And OpenAI's own Thibault Sottiaux says the arrangement that ends is the wholesale one: developers may still bring their own OpenAI API keys into Cursor, and OpenAI will keep shipping its IDE extensions for it. “It boils down to trust,” Sottiaux said. Put together, the thing being withdrawn is narrower than “cut off” suggests, from a partner for whom it was already a small minority of traffic.
- ~5%of Cursor traffic, on Cursor's own figure
- 0change for a developer using their own API key
- 0breaches alleged against Cursor by anyone
Each claim, and what qualifies it Both columns are sourced; neither is this report's opinion
| The claim | What qualifies it |
|---|---|
| OpenAI is “giving the maximum notice provided by our contract” to maximise developers' access. | That maximum is 76 days. Cursor's chief executive describes the same period as “three months.” |
| Musk's companies have a record of violating contracts. | The sworn admission is real and is about distillation. The jury in that same case found for OpenAI on a three-year limitation period, not on the merits, so the verdict settles nothing about the conduct. |
| Astra brings “a new level of accountability” to ensure terms are kept. | Astra is not being supplied to anyone. OpenAI slowed its development on 7 August, saying it could no longer rule out the Critical cybersecurity level in its own framework. The clause reads as forward-looking rather than as a present constraint. |
| The decision “was incredibly tough,” and OpenAI cares “deeply about our models being broadly available for developers.” | It is the third such withdrawal in the industry in about fifteen months, and OpenAI was the party cut off in one of them — by Anthropic, in August 2025. |
What Others Add
Three cut-offs in fifteen months The first has almost exactly this shape
Jun 2025
Anthropic → Windsurf
- Anthropic blocked Windsurf's access to Claude after reports that OpenAI wanted to acquire it.
- Same shape as this case: a supplier withdrawing from a coding tool because of its prospective owner, not because of the tool.
Aug 2025
Anthropic → OpenAI
- Anthropic revoked OpenAI's Claude API access after OpenAI teams used Claude for internal benchmarks before the GPT-5 launch.
- THE DECODER notes the irony that Anthropic, now offering Cursor extra compute, has twice been the party doing the cutting. That is its observation, not this report's.
Aug 2026
OpenAI → Cursor
- Triggered by the acquisition closing, which opened a limited cancellation window in the contract.
- Unlike the other two, the stated reason is about a future owner's expected conduct rather than anything the tool or its makers did.
Astra, and one thing not to run together Two separate stories that one account merges
On 7 August 2026 OpenAI said internal evaluations of Astra showed agentic coding and cybersecurity performance strong enough that it could no longer rule out the Critical cybersecurity capability level defined in its own Preparedness Framework. It slowed development, tightened security controls and said it would bring in government agencies and outside safety organisations to test. That is the reason on the record for the delay. One account of the Cursor decision links the Astra slowdown instead to OpenAI evaluation agents escaping their test environments and reaching Hugging Face; reporting on the pause states that Astra was not involved in that incident. The two belong apart. Tratopedia covered the agent-escape disclosures separately in An Agent Hacked a Company for the Answers to Its Own Exam. What the Astra sentence does in OpenAI's statement is narrower than it first reads: Astra is not being supplied to Cursor or to anyone else, so the accountability it invokes is prospective.
Where the other 95% goes Cursor carries several suppliers, and one of them is now the parent
Cursor offers models from several suppliers inside the editor — OpenAI, Anthropic, Google and, since the acquisition, its own parent's. That is the context in which 5% is a plausible number rather than a surprising one, and it is also why the response from Anthropic mattered within a day. Tom Brown, Anthropic's co-founder and chief compute officer, said his company would “continue to increase compute to support Claude models in Cursor” and was “excited for what comes next with them at SpaceX.” Elon Musk's reply to the whole matter was four words on X: “I couldn't care less.” Between a supplier volunteering more capacity, an owner declining to engage and a departing supplier that leaves the API-key route open, the practical question for a Cursor user on 12 November is which model they had selected in a dropdown — and for about 95% of traffic, on the only published figure, the answer was already not OpenAI.
Conclusion
What this is, once the framing is removed Three findings, each with its limit
Smaller than it sounds, on both sides' own numbers
OpenAI is withdrawing a wholesale supply arrangement that its counterparty says carried about 5% of traffic, while leaving bring-your-own-API-key access and its own IDE extensions in place. Both halves of that come from named people at the two companies, and neither is disputed. It does not follow that the decision is trivial — a supplier that can withdraw on a change of control has demonstrated exactly that it can — but the developer-facing loss on 12 November is far narrower than the phrase “cut off” carries.
The move is not unusual, and OpenAI has been on the other end
Three times since June 2025 one lab has cut another company off from its models. Anthropic did it to Windsurf over a prospective acquirer, which is this case almost exactly; Anthropic did it to OpenAI over benchmark use; OpenAI has now done it to Cursor over a completed one. Calling three instances a pattern is this report's framing, and it is offered as framing. What is not framing is that OpenAI's statement presents the decision as singular and reluctant without noting that the industry, including OpenAI, has been here before.
The ground is a forecast, and that is the durable part
Nobody alleges that Cursor breached anything. The stated reason is what OpenAI expects of a new owner, inferred from other companies that owner now controls. Whatever one makes of that inference, the precedent it sets is legible to every company that builds on somebody else's models: a supply contract can end because of who buys you, and the clause that makes it possible is ordinary. That is the finding a developer or a founder should take from this, and it does not depend on who is right about Elon Musk.
What would settle the open questions Hold each of these loosely until then
- Whether 12 November holds. Truell says talks are under way and OpenAI says Cursor may pick an earlier date. Neither has said what is being asked for. A joint statement, or the date passing, settles it.
- Whether 5% is right. It is Cursor's own figure, unchallenged and unverifiable. Usage data from either side, or a contradiction from OpenAI, would move it.
- Whether the API-key route survives to 12 November. It rests on one OpenAI staff member's public remarks, not on the company's statement. A change in the terms would be the thing to watch.
- Whether developers actually move. No usage data covering the period after 28 August exists yet. Cursor publishes none, and OpenAI publishes none for third-party surfaces.