The contract on the U.S.-Iran ceasefire lasting through Oct. 31 fell to as low as 69 cents between about 5:40 and 6 p.m. on Sunday and was back at 85.5 cents by early Monday. Every expiry moved together, including one whose deadline had already passed.
For about half an hour on Sunday evening, Polymarket's Iran contracts priced a much higher chance of a U.S. strike. No cause for the move has been established.
The contract on whether the U.S.-Iran ceasefire continues through Oct. 31 traded at 84.5 cents at 5 p.m. Eastern, fell to a low of 69 cents at 5:59 p.m., was back at 79 cents by 6:04 p.m. and stood at 85.5 cents at 4:47 a.m. on Monday. The same pattern ran through the whole ladder, with the selling starting at about 5:43 p.m. The Oct. 28 contract fell to 77 cents from 90.5 cents and ended at 93.5 cents. The Nov. 8 contract dropped to 54.5 cents and recovered to 65.5 cents. The Nov. 15 contract slipped to 40.5 cents and finished at 49.5 cents. Most of the move had reversed by 6:10 p.m.
What came after the drop
The drop came first. The contracts fell between about 5:40 and 6 p.m., before U.S. oil futures reopened at 6 p.m. The earliest known posts of a strike claim came at 6:03 p.m. on X and 6:10 p.m. on a market news service, as prices were already recovering. When the original Telegram post went up is unknown, and no cause for the drop has been established.
The claim, attributed to an Iranian activist on Telegram, said an Islamic Revolutionary Guard Corps missile launcher at Sirik had been hit by a missile from an "unknown fighter jet" minutes after firing a missile toward the Strait of Hormuz. No U.S. official, the Pentagon or U.S. Central Command confirmed any such strike, and the claim did not say who carried it out.
President Donald Trump had repeated on Sunday that there would be no strike that day. On Monday, senior officials from Saudi Arabia, Pakistan and Turkey were in Tehran for de-escalation talks.
Why the rules matter here
The contracts resolve to "No" only if the U.S. carries out "an air strike or a surface-to-surface missile strike" that "directly impacts" Iranian territory by the deadline. Intercepted munitions and threats that are not carried out do not count. Whether a strike on a launcher at Sirik would qualify depends on who carried it out and where it landed, and neither has been established.
The Oct. 24 contract, about 36 hours past its deadline and still unsettled, dipped twice: to 95.2 cents just before 6 p.m., and to 94.15 cents at about 7:10 p.m., after the claim was circulating. It was back at 99.6 cents by morning.
The Oct. 22 contract, about 84 hours past its deadline, has changed status again, back to "proposed," its 13th status entry, with seven proposed outcomes and six disputes. Neither Polymarket nor the oracle that settles its contracts has publicly explained the dispute.
The term structure, after the scare
By Monday morning the ladder implied roughly a 6.5% chance of a qualifying strike by Oct. 28, about 14.5% by Oct. 31, about 34.5% by Nov. 8 and about 50.5% by Nov. 15. The shape is the same as before Sunday evening: low odds this week, rising sharply after the U.S. midterm elections on Nov. 3.
Two readings
One reading is that the market showed resilience. Prices dropped sharply with no confirmed cause, and once nothing followed, every contract recovered in full within hours.
The other is that the episode shows how fragile the October prices are. The Oct. 31 contract lost 15 points in about 20 minutes, before any known report of a strike claim, and the November contracts still price a strike as roughly a coin flip.
What to watch
Any outcome from the Tehran talks, Israel's election on Tuesday, the Oct. 28 expiry, settlement of the Oct. 22 and Oct. 24 contracts, and the U.S. midterms on Nov. 3.