Why AI firms face a lawsuit over "slowing down" together

Four people who pay for AI chatbot subscriptions have taken Anthropic, OpenAI, Google and SpaceXAI to court, arguing that the companies broke competition law by agreeing, in public, to slow down how fast they improve their AI products.

The case, Buist et al. v. Anthropic PBC et al., was filed on 18 September 2026 in the US District Court for the Northern District of California. The four plaintiffs want to represent all US subscribers to Claude, ChatGPT, Grok and Gemini as a group, known as a class action. Their lawyer is Nick Rowley.

The complaint centres on 12 September, when Anthropic's chief executive, Dario Amodei, published an essay called "We Must Pace the Frontier", calling on the AI industry as a whole to slow the pace of capability gains. The plaintiffs say OpenAI's Sam Altman, SpaceXAI's Elon Musk and Google DeepMind's Demis Hassabis all signalled agreement that same day. They also point to an earlier statement, from July, about "intense competitive pressure not to unilaterally slow" down, which they read as evidence the firms felt bound to act together rather than alone.

Under US antitrust law, Section 1 of the Sherman Act bars competitors from agreeing to restrict output between themselves. The plaintiffs argue that a coordinated slowdown in product improvement counts as exactly that kind of restriction, and they are asking the court both to rule the companies liable and to issue an injunction stopping the alleged coordination, under Section 16 of the Clayton Act.

Importantly, the plaintiffs say they have no problem with any one company choosing to slow down for safety reasons on its own. Their objection is to competitors making that choice together. As the complaint puts it: "The antitrust laws do not permit competitors to decide among themselves that competition is too dangerous."

None of the four companies has responded to the claims yet, according to ABC News.

If you pay for Claude, ChatGPT, Grok or Gemini, this case is the reason you might see these companies in court: the plaintiffs say subscribers like you have been deprived of product improvements because of the alleged pact. No ruling has been made, so nothing changes with your subscriptions for now.

The case also touches a live debate about AI safety. Companies have argued they need room to coordinate on safety without facing legal risk for doing so. Bloomberg Law notes that Congress recently removed a related antitrust shield from a defence bill, while the Justice Department has indicated that narrower cooperation on cybersecurity between labs would not raise the same concerns. This lawsuit will test whether public statements about pacing AI development together can survive that scrutiny.

The case is at an early stage, with no response yet from Anthropic, OpenAI, Google or SpaceXAI. The court has not ruled on whether the case can proceed as a class action or on the underlying claims.