SpaceX's Compute Leverage: Why Anthropic Keeps Cursor While Cutting Rivals

OpenAI made headlines over the weekend by announcing it would revoke Cursor's direct access to its models beginning in November. The move stems from concerns about Elon Musk's track record with AI companies. In a statement released Friday evening, OpenAI cited two incidents involving Musk-controlled entities: Twitter's breach of a data-licensing agreement following Musk's 2022 acquisition, and xAI's acknowledged use of OpenAI models through distillation earlier this year, which the company says violated its terms. Now that SpaceX has completed its acquisition of Cursor, OpenAI has extended its scrutiny to the coding platform.

"This decision was incredibly tough, as we care deeply about our models being broadly available for developers," OpenAI stated. "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 more striking development came from OpenAI's chief competitor. Anthropic co-founder and chief compute officer Tom Brown responded within hours, publicly declaring that Cursor remains a "trusted partner" and that Anthropic would "continue to increase compute to support Claude models in Cursor."

A pattern of swift action

Anthropic's swift endorsement of Cursor raises eyebrows given the company's recent history with similar situations. Consider Windsurf, an AI coding tool that became the subject of acquisition rumors in May 2025 when reports surfaced that OpenAI was negotiating to purchase it for $3 billion. Anthropic moved quickly, cutting Windsurf's access to Claude 3.5 Sonnet and Claude 3.7 Sonnet within weeks. At a TechCrunch event shortly after, Anthropic co-founder Jared Kaplan remarked that "it would be odd" for Anthropic to be selling Claude to OpenAI. The OpenAI deal ultimately fell through, and Google acquired Windsurf's founders and research team for DeepMind, paying $2.4 billion.

https://x.com/NotTomBrown/status/2093541294027280657?ref_src=twsrc%5Etfw

Gergely Orosz, an engineer and author of the Pragmatic Engineer newsletter, highlighted the Windsurf episode in a social media post on Sunday. "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?"

There is also the case of xAI, the artificial intelligence company Musk established in 2023 to develop Grok. SpaceX acquired xAI outright in February in a transaction that valued the company at $250 billion. In January, Kylie Robison reported that Anthropic had revoked xAI staff access to Claude, which they had been using through Cursor. Cursor reportedly informed xAI that this was "a new policy anthropic is enforcing for all its major competitors."

Anthropic has demonstrated a pattern of acting decisively, sometimes based on mere speculation as in Windsurf's case, whenever a customer begins to look like a rival. This makes the company's public backing of a firm now fully owned by one of its genuine competitors particularly noteworthy.

The compute factor

The distinction between SpaceX and the earlier Windsurf and xAI situations lies in Anthropic's substantial reliance on SpaceX for computing resources. On May 6, Anthropic disclosed that it had secured the complete output of SpaceX's Colossus 1 data center located near Memphis, Tennessee — representing more than 300 megawatts of computing power and approximately 220,000 Nvidia GPUs. Facing constraints on available compute, Anthropic used the SpaceX arrangement, combined with other recent computing agreements, to nearly immediately expand usage caps for Claude Pro and Max users.

Financial specifics emerged two weeks later through SpaceX's IPO filing. Anthropic committed to paying $1.25 billion monthly for computing resources across Colossus and Colossus II — totaling roughly 325,000 Nvidia GPUs combined — with the arrangement running through May 2029 and subject to termination provisions. SpaceX indicated the deal would help it monetize excess computing capacity while preserving sufficient resources for its own artificial intelligence training and inference operations. The arrangement underscored how critical compute access had become in competition among leading artificial intelligence laboratories and established an unusual commercial dynamic: Anthropic was purchasing massive amounts of computing from a company that simultaneously owned one of its direct artificial intelligence competitors in xAI.

This context makes Anthropic's response to the Cursor acquisition particularly significant. Following Tom Brown's Saturday post on X, Replit founder and CEO Amjad Masad drew attention to the disparity between Anthropic's current support for Cursor and its treatment of Windsurf previously, characterizing the latter as substantially harsher than OpenAI's decision regarding 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 presents a comparable analysis. Given that Anthropic terminated access when Windsurf merely appeared destined for OpenAI's ownership, what explains the company's public commitment to expand Claude capacity for Cursor following its actual acquisition by SpaceX?

"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," Orosz writes. "SpaceX basically in this enviable position where one of its biggest competitors depends on its compute infra!"

This situation illustrates SpaceX's advantageous standing. The company now controls xAI and Cursor, positioning it as a direct competitor to Anthropic in foundational models through Grok and in artificial intelligence coding platforms through Cursor. Simultaneously, Anthropic is transferring billions of dollars to SpaceX for computing capacity that powers Claude. SpaceX possesses leverage that neither Windsurf nor xAI held when Anthropic moved against them: a critical dependency that influences any future decision about Claude access.