OpenAI says it cannot be sure a Musk-owned business would stay inside its usage rules, pointing to Twitter's breach of its contract and Musk's admission under oath that xAI violated them. Anthropic answered within hours, promising more compute to keep Claude in the tool.

OpenAI said on 28 August that it had notified SpaceX it intends to wind down the contract under which the coding tool Cursor receives its models. Its announcement proposes 12 November 2026 as the day the service stops. Developers keep access until then, and no model OpenAI releases from here on will be added to the tool.

OpenAI's stated reason is trust. It says it cannot be confident SpaceX would keep its use of the technology inside the terms set for customers, a doubt it traces to a pattern of Musk-owned businesses breaking their agreements. After Musk acquired Twitter — now part of SpaceX — that company breached the terms of its OpenAI contract, it says; and under oath earlier this year Musk admitted that xAI, likewise now part of SpaceX, had violated OpenAI's terms of service, terms OpenAI says closely resemble xAI's own.

The change of ownership is what let OpenAI cancel: its contract with Cursor left only a limited window to do so once control changed hands. SpaceX completed its $60 billion acquisition of Anysphere, Cursor's parent, on 14 August 2026.

Michael Truell, who co-founded Cursor and is now a SpaceX executive, played the damage down. "OpenAI models serve about 5% of Cursor user traffic, and we're speaking with the OpenAI team to resolve this," he wrote on X. Cursor, he added, had trusted OpenAI "to be neutral infrastructure for our business." Cursor's selling point has been letting customers pick whichever model fits the task; what it loses is the assumption that every popular model stays within reach.

Musk brushed the decision aside on X. "I couldn't care less," he wrote, before calling Sam Altman and Greg Brockman untrustworthy and repeating his claim that they stole an open-source nonprofit.

Anthropic moved within hours. Tom Brown, one of its co-founders, wrote on X that "Cursor has been a trusted partner of Anthropic since Sonnet 3.5" and that the company would "continue to increase compute to support Claude models in Cursor." Anthropic has done its own cutting off — it dropped xAI in January after finding its staff using Claude through Cursor, and cut OpenAI off shortly before the launch of GPT-5 — and it buys computing capacity from SpaceX.