Kalshi has become the exclusive prediction market partner of the US Open, Front Office Sports reported Sunday, citing two sources familiar with the agreement. The deal reportedly took effect immediately and was not formally finalized until after last week’s qualifying rounds, before the main draw opened Sunday in Flushing Meadows.

Financial terms were not disclosed. The USTA, which owns and operates the tournament, is barring rival prediction market platforms from advertising inside the venue and on television, including across ESPN’s broadcasts, a term one source was quoted as calling “unusual.” The association had planned to weigh prediction market partnerships for 2027 and beyond and, as of last week, had not formally approved the category at all. Craig Tiley, who became USTA chief executive this year after more than a decade running Tennis Australia, pushed to get a deal, according to FOS. Kalshi still doesn’t appear on the US Open’s official lisf of partners.

This story is an excerpt from the Unchained Daily newsletter.

Kalshi, Polymarket and Polymarket US have handled a combined $43.4 billion in volume so far in August, with Kalshi accounting for $35.55 billion.

The report came two days after a legal setback. On Friday the Ninth Circuit ruled that Kalshi had not shown federal commodities law preempts Nevada’s gaming regulations for sports-event contracts, conflicting with an earlier Third Circuit decision that stopped New Jersey from regulating the same products. The split sharpens the question of whether the CFTC or state gaming regulators control the category and moves a Supreme Court fight closer. Kalshi’s other pressure points remain: New York is seeking at least $36 billion over alleged unlicensed gambling, and courts in Washington and Michigan have restricted its sports contracts.

Prediction markets have been collecting sports properties throughout the uncertainty. Kalshi and Polymarket are both official NHL partners, Polymarket holds the league-level deal with MLB and an agreement with the Yankees, and Kalshi has team-level deals with the Blackhawks and MLB’s Giants, Braves, Padres, Red Sox and Dodgers. The NFL and NBA remain holdouts. A Nevada judge extended a ban on Kalshi’s sports contracts in April, calling them indistinguishable from gambling, and the ATP told the CFTC in an April comment letter that it supports rules for sports-event contracts, including a prohibition on contracts tied to player injuries and officiating decisions.

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