Anthropic keeps Claude in SpaceX owned Cursor

Anthropic co-founder Tom Brown said on August 29 that Anthropic will keep supplying Claude to Cursor, now owned by SpaceX, and will put more compute behind it. He posted within hours of OpenAI’s announcement that it would cut Cursor’s direct access to OpenAI models in November. The New Stack sets Brown’s reply against Anthropic’s own record of cutting off customers that start to look like competitors. It also points to a contract that runs the other way: Anthropic pays SpaceX $1.25 billion a month for data center capacity.

OpenAI pinned its decision on Elon Musk. Its statement, issued late on Friday, August 28, cited two episodes. The first was Twitter breaking a data-licensing deal after Musk took over the company in 2022. The second was Musk’s admission under oath earlier this year that xAI had partly used OpenAI models through distillation (training a model on another model’s outputs), which OpenAI says broke its terms of service. Now that SpaceX’s $60 billion purchase of Cursor has closed, OpenAI is applying the same reasoning to Cursor. “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,” the company wrote.

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.

What happened to Windsurf

Anthropic’s earlier cases went differently. In May 2025, reports said OpenAI was in talks to buy Windsurf, another AI coding tool, for $3 billion. Anthropic didn’t wait for a deal. Within weeks Windsurf said it had lost direct access to Claude 3.5 Sonnet and Claude 3.7 Sonnet. “With less than five days of notice, nearly all of our first-party capacity to all Claude 3.x models has been cut off,” CEO Varun Mohan said, adding that Windsurf had been willing to pay for full capacity. When Claude 4 launched, Cursor and GitHub Copilot had it on day one and Windsurf did not.

Speaking at TC Sessions: AI shortly afterwards, Anthropic co-founder Jared Kaplan explained the move: “I think it would be odd for us to be selling Claude to OpenAI.” He also pointed to limited compute and a focus on “lasting partnerships,” Benzatine reported, quoting him: “We really are just trying to enable our customers who are going to sustainably be working with us in the future.” OpenAI never closed that deal. Google paid $2.4 billion to hire Windsurf’s founders and R&D staff into DeepMind.

The second case went through Cursor itself. In January this year, Kylie Robison reported that Anthropic had cut off xAI staff who had been using Claude inside Cursor. Cursor reportedly told xAI it was “a new policy anthropic is enforcing for all its major competitors.” SpaceX bought xAI outright the next month, in a February deal that valued it at $250 billion. Cursor is now a sister company of the lab whose engineers were locked out through it.

Gergely Orosz, who writes the Pragmatic Engineer newsletter, compared the cases on Sunday, August 30. He noted that Windsurf had also been a “trusted partner.” “They cut them off ruthlessly when RUMORS of OpenAI potentially buying Windsurf surfaced,” Orosz wrote. “Now, SpaceX, an Ant(hropic) competitor bought Cursor — it’s still a trusted partner?”

$1.25 billion a month

What sets SpaceX apart from the Windsurf and xAI episodes, The New Stack argues, is that Anthropic also buys a huge amount of compute from it. On May 6, Anthropic announced it had taken the entire output of SpaceX’s Colossus 1 data center near Memphis, Tennessee: more than 300 megawatts and over 220,000 Nvidia GPUs. Anthropic had been short on compute. With this deal and several other recent agreements, it raised usage limits for Claude Pro and Max subscribers almost overnight.

The financial terms appeared two weeks later in SpaceX’s IPO filing. Anthropic agreed to pay $1.25 billion a month for capacity across Colossus and Colossus II, about 325,000 Nvidia GPUs combined. The contract is scheduled to run through May 2029, subject to termination rights. That comes to $15 billion a year.

SpaceX said the arrangement lets it monetize part of its compute while keeping enough for its own AI training and inference. It also left Anthropic buying a huge amount of compute from a company that owns one of its direct AI rivals in xAI. In 2025 Kaplan cited tight compute as one reason to drop Windsurf; this time Anthropic is promising Cursor more of it, and the compute comes in part from Cursor’s new owner.

“You need the compute”

Brown’s post gives one reason, and it is the history: Cursor has been a partner since Sonnet 3.5. SpaceX now competes with Anthropic in foundation models through Grok and in coding tools through Cursor. For Cursor users, OpenAI models leave the editor’s direct supply in November while Claude stays.

Replit founder and CEO Amjad Masad replied to Brown’s post on Saturday. He argued that Anthropic’s treatment of Windsurf had been harsher than OpenAI’s cut-off of Cursor. “Maybe you changed your ways, but we all remember what you did to Windsurf, which was infinitely nastier,” Masad wrote. “More likely answer is that you can’t do that here because you need the compute.”

Orosz reached the same conclusion. “Either SpaceX and Grok are not competitors to Anthropic (they are!); or, more likely, SpaceX leasing its Colossus 1 data center is more important to Anthropic than to stop offering Claude to SpaceX,” he wrote. “SpaceX basically in this enviable position where one of its biggest competitors depends on its compute infra!”