Buist v. Anthropic, PBC, No. 3:26-cv-10693, is a proposed class action filed September 18, 2026 in the U.S. District Court for the Northern District of California by four individual subscribers to paid AI services against Anthropic, OpenAI, SpaceXAI and Google. The complaint alleges that the four companies agreed to slow the pace at which each improves the products it sells to consumers, and that the agreement is a horizontal restraint on output and quality under Section 1 of the Sherman Act. It pleads Dario Amodei's September 12, 2026 essay "We Must Pace the Frontier" as the proposal and statements by Elon Musk, Sam Altman and Demis Hassabis the same day as acceptances (Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026); Source: broadbandbreakfast.com).
The complaint itself is summarised at Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026).
Infobox
| Field | Value |
|---|---|
| Plaintiffs | Charles Buist (Florida), Cheyenne Hunt (California), Christine Bullock (California), Nick Spetsas (Florida), individually and for a proposed nationwide class |
| Defendants | Anthropic, PBC; OpenAI OpCo, LLC; SpaceXAI LLC; Google LLC |
| Court | U.S. District Court for the Northern District of California, San Francisco Division, No. 3:26-cv-10693 |
| Judge | Magistrate Judge Nathanael M. Cousins (assigned September 18, 2026) |
| Filed | September 18, 2026 |
| Cause | 15 U.S.C. § 1 (Sherman Act § 1); Clayton Act §§ 4 and 16 |
| Nature of suit | 410 Anti-Trust |
| Jury demand | Plaintiff |
| Plaintiffs' counsel | Trial Lawyers for Justice — Nicholas C. Rowley (lead counsel), Andrew T. Tutt, R. Stanton Jones, Jakob Z. Norman |
| Status | Active; consent or declination to magistrate-judge jurisdiction due October 2, 2026 |
(Source: courtlistener.com; Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026))
Background
The suit follows a week of public statements on coordinated pacing of frontier AI development. Amodei's essay (We Must Pace the Frontier (Amodei, September 2026)) proposed embedded third-party evaluators, coordination among frontier companies in democracies on common safety standards and "limits on the rate of unchecked AI progress," and a narrow government antitrust waiver for certain safety conversations. OpenAI had asked members of Congress whether an industry-wide slowdown would be lawful under antitrust law; Altman said on September 14 that OpenAI did not believe it needed an exemption to begin; and OpenAI global policy chief Chris Lehane said on September 15 that safety engagement with Anthropic and Google DeepMind had been under way for several weeks. Federal Trade Commission chairman Andrew Ferguson, speaking personally, said the same day that "everyone should be deeply suspicious" of companies seeking both regulation and an antitrust exemption. See Coordinated slowdown proposals compared and AI Antitrust.
Claims
The complaint describes the agreement as "proposed in public, accepted in public, and confirmed in public." It quotes the essay's thesis, "We must slow the pace at which we improve the capabilities of AI models," its call for "industry-wide coordination" on "limits on the rate of unchecked AI progress," and its statement that coordinated slowing would let each participant reduce its pace "without sacrificing commercial advantage." It alleges that Musk quote-posted the proposal within about an hour with "Dario is right"; that Altman wrote "I agree with Dario that we need to pace the frontier" and committed OpenAI to the essay's first step; and that Hassabis said the essay pointed toward "the right path forward" and tied it to the industry-wide standards body he had proposed in July (A Framework for Frontier AI and the Dawning of a New Age (Hassabis, July 2026)). The statements are attributed to each defendant through those individuals, and Musk's to SpaceXAI as the person who founded and controls its AI business (Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026)).
As evidence that the agreement preceded September 12, the complaint cites the July 2026 employee statement that each company faces "intense competitive pressure not to unilaterally slow" (Pacing the Frontier (statement from employees of frontier AI companies, July 2026)); a working group of Anthropic, OpenAI and Google representatives below the CEO level that it alleges met regularly from July on creating an industry standards body; Jakub Pachocki's September 6 essay naming "coordinating to slow down future development" as an option (An Alien Mind (Jakub Pachocki, OpenAI, September 2026)); OpenAI's inquiry to members of Congress; an Altman interview of September 11 in which, asked why leading AI executives did not develop a common plan, he said "I think that will happen"; Altman's September 14 statement that AI progress "should be slower than it otherwise could be"; and Lehane's September 15 statement. The complaint reads the essay's embedded-evaluator step as the means of "policing defection," because it would let outsiders confirm that each participant was slowing as agreed (Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026)).
A single Sherman Act count is pleaded three ways: as a naked horizontal restraint unlawful per se; in the alternative under "quick-look" analysis; and in the alternative under the rule of reason. For the rule-of-reason alternative the complaint defines a "Paid Frontier AI Assistant Subscription Market" in the United States comprising the paid tiers of ChatGPT, Claude, Grok and Gemini, alleges on information and belief that the defendants hold at least 80% of it, and pleads an innovation market for general-purpose frontier generative-AI models in the further alternative. The theory of injury is that subscribers pay the same or higher prices for products that improve more slowly than unrestrained competition would produce, which the complaint characterizes as an overcharge recoverable under Section 4 of the Clayton Act (Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026)).
The complaint limits its target. It states that the plaintiffs "take AI safety seriously," do not challenge any defendant's unilateral decisions on safety, testing, evaluators or the pace of its own development, and do not seek liability for advocacy to Congress, the White House or agencies, including advocacy for an antitrust exemption; those petitioning statements are pleaded only as evidence of knowledge and intent. It argues that safety objectives can be pursued unilaterally or through regulation, and that whether frontier AI should develop more slowly "is a question for each company acting alone, or for Congress and the agencies" (Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026)).
Some of the complaint's characterisations of the pre-September 12 record differ from other accounts of the same material. It describes the July statement as published by "senior executives of Anthropic, OpenAI, and Google" and names Shane Legg among its signatories; the statement was an open letter signed by employees of several frontier companies in a personal capacity, including Meta and Thinking Machines, and asked for U.S. government support for an international effort to build pacing tools (Pacing the Frontier (statement from employees of frontier AI companies, July 2026)). Legg's name does not appear in the captured first 30 of 1,224 signatories. The complaint reads the essay as proposing limits on training compute, training runs and AI-driven AI development; the essay favoured pacing keyed to capability and observed safety and described input-based measures as possibly "more 'gameable'" (We Must Pace the Frontier (Amodei, September 2026)). Altman's July remark that OpenAI helped shape the statement and his September 11 Fortune interview are recorded only through the complaint (Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026)).
Relief sought and proposed class
The plaintiffs seek certification of a nationwide class of persons who, from September 12, 2026 until the effects of the alleged conduct cease, bought directly from a defendant a paid individual consumer subscription to ChatGPT, Claude, Grok or Gemini, with a subclass for each defendant; they reserve the right to move the start date earlier if discovery shows the agreement formed before September 12. Buist, Hunt and Spetsas subscribe to all four services and Bullock to Claude alone. The complaint seeks treble damages, fees and interest under Section 4 of the Clayton Act, and a preliminary and permanent injunction under Section 16 barring each defendant from any agreement with a horizontal competitor on the rate at which competing AI products are developed, trained or released; on limits on training compute or training runs adopted under a pacing arrangement; on limits on the use of AI to develop improved AI; on coordinated release delays; on capability checkpoints operating as agreed restraints; and on exchanging competitively sensitive information to police such a restraint. The proposed injunction expressly leaves each defendant free to adopt safety measures, slow its own development, retain evaluators, comply with government requirements, petition government, and take part in standard-setting that does not restrain independent competition over pace (Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026)).
Procedural history
The complaint, certificate of interested entities and proposed summons were filed on September 18, 2026, and the case was assigned the same day to Magistrate Judge Nathanael M. Cousins, with consent or declination to magistrate-judge jurisdiction due October 2, 2026. A clerk's notice the same day flagged an electronic-filing error concerning counsel's telephone number. The complaint states that pro hac vice applications for two of the four listed attorneys were forthcoming (Source: courtlistener.com). The Associated Press reported the filing on September 19 (Source: broadbandbreakfast.com).
Current status
As of September 21, 2026 the docket showed no appearance or response by any defendant, and no public statement by any defendant about the suit is recorded here (Source: courtlistener.com).
Open questions
- Whether the defendants will contend that the September 12–15 statements are protected petitioning or unilateral announcements rather than an agreement, given the complaint's disclaimer of liability for advocacy.
- Whether Congress acts on an antitrust exemption such as the Collaboration on Adversarial Threats and Security Risks Act while the case is pending, and how an exemption framed around written notice to the Antitrust Division would bear on conduct alleged to predate it.
Relationships
- litigates: Anthropic — defendant; its chief executive's essay is pleaded as the proposal.
- litigates: OpenAI — defendant.
- litigates: xAI — defendant as SpaceXAI LLC.
- litigates: Google DeepMind — Google LLC is the defendant; the complaint names Google DeepMind as the unit developing Gemini.
- depends-on: Class action complaint, Buist v. Anthropic, PBC (N.D. Cal., No. 3:26-cv-10693, filed September 18, 2026) — the class action complaint (docket entry 1).
- depends-on: We Must Pace the Frontier (Amodei, September 2026) — the essay the complaint treats as the offer.
- depends-on: Pacing the Frontier (statement from employees of frontier AI companies, July 2026) — the July statement cited for the collective-action problem.
- depends-on: A Framework for Frontier AI and the Dawning of a New Age (Hassabis, July 2026) — the standards-body proposal the complaint treats as the coordination vehicle.
- related: An Alien Mind (Jakub Pachocki, OpenAI, September 2026) — cited for "coordinating to slow down future development."
- instance-of: AI Antitrust — private Sherman Act enforcement against a proposed safety coordination.
- related: Coordinated slowdown proposals compared — the proposals and the antitrust-exemption debate the suit responds to.
- related: Collaboration on Adversarial Threats and Security Risks Act (S. 5105) — pending exemption for delay agreements among developers.
- related: Dario Amodei, Sam Altman, Elon Musk, Demis Hassabis, Chris Lehane — the individuals whose statements are pleaded as the agreement.