Will Joao Fonseca win the 2026 Men's US Open?
Crossbook compares what two exchanges, Polymarket and Kalshi, charge for the same event, and publishes a permanent scored record of its own forecasts under published rules.
A confirmed cross-venue pair. Only one side is priced right now.
Data may be delayed. These prices have not refreshed recently, so treat them as a last known reading rather than a current quote.
How each venue defines this
Each exchange's own settlement text, quoted as written. Where they differ, the difference is usually why the prices do.
Settles Sep 13, 26
The 2026 U.S. Open tennis tournament is scheduled for August 23 - September 13, 2026. This market will resolve to the player that wins the 2026 U.S. Open Men’s Singles Tournament. If at any point it becomes impossible for a listed player to win the 2026 U.S. Open Men’s Singles Tournament per the rules of the tournament, the corresponding market will resolve to “No”. If the 2026 U.S. Open Men’s Singles Tournament is cancelled, postponed after October 31, 2026, or there is otherwise no winner declared within that timeframe, this market will resolve to “Other”. The primary resolution source w…
Settles Sep 14, 26
If Joao Fonseca wins the 2026 US Open Men's Singles professional tennis tournament, then the market resolves to Yes.
Settlement basis
A person confirmed these two markets ask the same question. Their settlement documents have not been compared, so treat the price difference as unverified rather than as a like for like gap.
Confirmed as the same question: Will Joao Fonseca win the 2026 Men's US Open?
Crossbook forecast
No public Crossbook forecast on this market yet. Every call that is made is timestamped and scored on the public record, win or lose.
Context
Polymarket and Kalshi agree on this one. Both price it near 1%, so there is no cross venue disagreement to trade and no basis to speak of.
Volume over the last 24 hours is modest, at about $15,649 on the busier venue. At least one side of this market has no real two sided book, which means the quoted price is closer to a placeholder than to a traded level. It closes in 4 days. Prices this close to resolution move on news rather than on reassessment.
Related markets
Crossbook publishes every forecast it makes, timestamped before the answer is known and scored against the market afterwards. See the public record and the rules it is held to.