United States Court of Appeals For the Seventh Circuit ____________________ No. 20-1581 MARION HEALTHCARE, LLC, Plaintiff-Appellant,

v. SOUTHERN ILLINOIS HOSPITAL SERVICES, a not-for-profit corpo- ration doing business as Southern Illinois Healthcare; and HEALTH CARE SERVICE CORPORATION, doing business as Blue Cross and Blue Shield of Illinois, Defendants-Appellees. ____________________

Appeal from the United States District Court for the Southern District of Illinois. No. 3:12-CV-871-MAB — Mark A. Beatty, Magistrate Judge. ____________________

ARGUED NOVEMBER 10, 2020 — DECIDED JULY 15, 2022 ____________________

Before EASTERBROOK and SCUDDER, Circuit Judges.*

* Circuit Judge Kanne, a member of the panel at the time of argument, died on June 16, 2022. This appeal is being decided by a quorum. 28 U.S.C. §46(d). 2 No. 20-1581

EASTERBROOK, Circuit Judge. The operator of an outpatient surgery clinic in southern Illinois accuses the area’s largest hospital system and its largest health insurer of violating fed- eral antitrust law and similar state rules by entering into con- tracts that designate the hospital but not the clinic as a pre- ferred provider (also known as an in-network provider) for the insurer. This leads some patients to choose the hospital over the clinic because more of the fees will be reimbursed, copayments will be lower, or both. District Judge Herndon dismissed much of the complaint but permiTed Marion HealthCare (which we call the Clinic) to try again. 2013 U.S. Dist. LEXIS 120722 (S.D. Ill. Aug. 26, 2013). After Judge Herndon retired, the case was transferred to District Judge Yandle, who granted judgment in favor of the insurer (Health Care Service Corp., which we call the Blues because it comprises both Blue Cross and Blue Shield plans). Judge Yandle concluded that insurers are customers and cannot be liable for the practices of sellers with market power. 2015 U.S. Dist. LEXIS 69749 (S.D. Ill. May 29, 2015). As payors, insurers should be aligned as plaintiffs (if they are to be liti- gants at all) rather than defendants. But Judge Yandle denied the motion of Southern Illinois Hospital Services to dismiss the amended complaint. (We call it the Hospital, singular, alt- hough it has three facilities in southern Illinois—a hospital in Carbondale, population 25,000, and two smaller facilities.) The Clinic and the Hospital agreed that a magistrate judge could handle the rest of the case and enter a final judgment. 28 U.S.C. §636(c). Discovery followed, but, before releasing a decision on the Hospital’s motion for summary judgment, Magistrate Judge No. 20-1581 3 Williams retired. His successor appointed the retired judge as a special master. Reviewing the special master’s report, Mag- istrate Judge BeaTy granted summary judgment to the Hos- pital on the ground that the Clinic had not been injured. 2020 U.S. Dist. LEXIS 55745 (S.D. Ill. Mar. 31, 2020). That wrapped up all parties and issues. The Clinic ap- pealed, contesting the decisions of both District Judge Yandle and Magistrate Judge BeaTy. No one noticed a potential juris- dictional problem: the Blues had not consented to a magis- trate judge having final authority. We held in Coleman v. Wisconsin Labor & Industrial Commis- sion, 860 F.3d 461 (7th Cir. 2017), that use of the §636(c) proce- dure requires the consent of every named litigant, even one that has not been served with process. In the absence of all parties’ consent, Coleman concludes, a district judge rather than the court of appeals reviews the magistrate judge’s deci- sion. We directed th