So's final opponent was Sam Sevian, who sat in last place on 2.5 out of 10 and had not won a game all event. So had gone 48 U.S. Championship games without a loss. Sevian came out of the opening with an edge and ground So down in a heavy-piece endgame. "I just really like playing him, especially in classical," Sevian said afterward.

On the next board, Fabiano Caruana did what he had to. Before the round he had put So's chances of losing at "zero percent." Then he beat Awonder Liang on demand, and by the time he finished, So was in trouble. Both men ended on 7 out of 11.

Caruana came in chasing a fifth straight title. He had won every U.S. Championship since 2022, plus one in 2016. His event turned in round five, when 16-year-old Andy Woodward beat him with a slow positional squeeze, the best win of Woodward's career. Late in the event he drew three games in a row, including his round-nine meeting with So, where So answered Caruana's sharpest opening idea with a new one of his own.

A quiet subplot: one of the players chasing So was Grigoriy Oparin, who works as Caruana's second. He shared second place with Caruana after nine rounds.

The tiebreak on Thursday was two rapid games at 15 minutes plus 10 seconds, with blitz to follow if needed. It never got that far. In the first game So had Caruana close to beaten, missed the cleanest way through, and had to settle for a draw. In the second, Caruana gambled on an early pawn sacrifice. So took control, won a piece on move 22, and Caruana resigned. So won the playoff 1.5–0.5.

He did it on almost no rest. So said he slept two or three hours and spent the night "just feel sorry for myself 90 percent of the time." He called the playoff "very poor quality for both of us." It didn't matter. It is his fourth U.S. title, after 2017, 2020 and 2021, and it ends Caruana's run at four in a row.

The women's championship needed no playoff. Rachael Li, a 16-year-old making her debut, won it outright. Alice Lee led after five rounds with 4.5 out of 5, but Li overtook her, beat Nazi Paikidze in round nine to go a point clear, and earned her first IM norm along the way.

In the last round she needed a draw against Anna Zatonskih. Early in the game Zatonskih declined a repetition that would have ended it, out of fairness to Lee, who could still catch Li. "I would have done the same," Li said. The game was drawn anyway, and Li finished on 8.5 out of 11, half a point ahead of Lee, with Irina Krush third. Defending champion Carissa Yip, going for a fourth straight title, was out of the race early, with two draws and three losses in her first five games.