Charles Buist, Cheyenne Hunt, Christine Bullock and Nick Spetsas filed Buist v. Anthropic, PBC, No. 3:26-cv-10693, in the US District Court for the Northern District of California on September 18, 2026, against Anthropic, OpenAI OpCo, SpaceXAI and Google. The plaintiffs say they pay for subscriptions to Claude, ChatGPT, Grok or Gemini, and they sue for a proposed nationwide class of direct purchasers of paid consumer subscriptions from September 12, 2026. Their complaint alleges the companies reached an agreement to restrain the pace at which they develop and improve competing products, which it says violates Section 1 of the Sherman Act. It points to an essay Anthropic chief executive Dario Amodei published on September 12 calling for industry-wide coordination on the pace of AI progress, public statements the complaint describes as agreement from Elon Musk, Sam Altman and Demis Hassabis the same day, and a working group of Anthropic, OpenAI and Google representatives that it says has met since July. It alleges the arrangement is unlawful per se, or alternatively under quick-look analysis or the rule of reason. The plaintiffs seek treble damages under the Clayton Act and an injunction against agreements among competitors on the pace of AI development, and say they do not challenge any company's independent safety decisions. The complaint says the essay stated that a government waiver would be needed for certain safety conversations, and that no such waiver exists. The allegations have not been tested in court.