Polymarket's contract on the U.S.-Iran ceasefire holding through Oct. 31 fell from about 96 cents to 68 cents by 7 p.m. ET Thursday, after reports of a strike-options briefing for President Trump, then recovered to about 92 cents. The Nov. 8 contract swung from 80.5 cents to 45 cents and back to 73.5 cents.
For about four hours on Thursday evening, traders on Polymarket treated a U.S. strike on Iran within two days as a real possibility. By early Friday they had mostly changed their minds.
The swing
The contract on the U.S.-Iran ceasefire continuing through Oct. 31 fell from about 95.7 cents early Thursday afternoon to about 68 cents at the 7 p.m. ET reading. That implied roughly a 32% chance of a U.S. strike on Iran before the contract expires, by our arithmetic. By early Friday it was back at about 91.6 cents. It traded about $818,000 in 24 hours.
The Nov. 8 contract fell from 80.5 cents to 45 cents at 7 p.m., then recovered to 73.5 cents. The Nov. 15 contract went from 53 cents to 37 cents and back to 48.5 cents. All three ended lower than where they started.
The contracts resolve "No" if the United States conducts an air strike or surface-to-surface missile strike that directly hits Iran by the stated date, measured at 11:59 p.m. Iran Standard Time.
What preceded it
The slide followed two reports. By about 3:16 p.m. ET, reports citing Iran's Tasnim news agency said that parliament speaker Ghalibaf had rejected U.S. outreach, saying "the carrot-and-stick policy has no effect on Iran." Shortly before 4 p.m., reports citing the Wall Street Journal said Adm. Brad Cooper, the head of U.S. Central Command, had briefed President Trump in person, alongside Hegseth and Gen. Caine, on options for Iran. The White House said "all options" were on the table.
The recovery came after 8 p.m., with no strike reported. Earlier, shortly after midnight Tehran time, or about 4:37 p.m. ET and before the trough, Iran's official news agency IRNA said Tehran had not yet responded to the letter from Vice President JD Vance and called media speculation about its content "inaccurate."
Oil moved in the same direction. Brent futures rose in Asian trading on Friday, and gold fell.
How much to trust the trough
The 7 p.m. low came in a thin evening market, a few hours after Polymarket's international exchange was halted for about an hour because of a compromise at a third-party provider. The Oct. 31 contract had about $65,000 of liquidity. The speed of the recovery suggests the trough overshot.
Two-day risk or noise?
The risk view: a reported in-person briefing on strike options, a public Iranian rejection and oil prices moving the same way are reasons to price more than a small chance of action, and the contracts still ended lower.
The noise view: the move unwound within hours, no strike occurred, the diplomatic channel through Qatar remains open, and evening liquidity was too thin for the low to mean much.
What to watch
The Oct. 31 contract's expiry on Saturday night, Iran time; any Iranian reply to the Vance letter or the Qatari draft; the days after the Nov. 3 midterms; and the Nov. 8 and Nov. 15 contracts.