Houthi forces blamed Saudi Arabia for new airstrikes overnight, and Polymarket's ceasefire contracts rose. The implied chance of an American strike by Oct. 31 fell to about 18.5%. Only direct U.S. strikes count under the contract's rules.
The war around Yemen escalated overnight. The prediction market on whether the U.S. joins it moved the other way.
Between 2 p.m. Eastern on Monday and early Tuesday, Polymarket's end-of-October ceasefire line gained 2 cents, to 81.5 cents, in two steps at midnight and 1 a.m. The Oct. 15 line moved further, from 94.5 cents to about 97.6 cents, and touched 97.95 cents at 4 a.m.
On those prices, traders put the chance of a qualifying American strike on Yemen at about 18.5% by the end of the month and about 2.5% by Thursday, down from about 20.5% and 5.5% on Monday afternoon.
What Happened Overnight
Houthi-run media said two airstrikes hit Kamaran island in the Red Sea, a third hit Qanawis district about 55 kilometers northwest of the port of Hodeida, and further strikes landed in Jawf province. The group blamed Saudi Arabia. There was no immediate comment from Riyadh.
On Monday evening, air-raid sirens sounded in Riyadh and explosions were heard. The Houthis said they had fired a ballistic missile at King Khalid International Airport, and Saudi Arabia said it shot down a ballistic missile aimed at the capital, the third day in a row of such attacks. Riyadh's main airport has suspended operations until midnight on Oct. 17.
No U.S. strike or U.S. decision on joining the fighting was reported. On Saturday President Trump had said Washington "may" take part in the Saudi response.
Why Saudi Strikes Push The Price Up
The contracts resolve No only if the U.S. carries out a qualifying strike itself, an air or surface-to-surface attack that hits Yemen's land or internal waters. Strikes by Saudi Arabia or other coalition members do not count, and neither does American support for those strikes.
That makes Saudi action an alternative to American action as far as the contract is concerned. If Riyadh is doing the striking on its own, the market appears to read that as less pressure on Washington to act directly, although nothing in the trading data shows why buyers stepped in.
The Shape Of The Risk Has Changed
On Monday, traders priced more risk per day in the few days before Oct. 15 than later in the month. That is no longer true. The Oct. 15 contract now implies about 1% a day for the roughly two and a half days left. The Oct. 31 contract, after removing the near-term window, implies about 16.5% for the following 16 days, also about 1% a day.
The market no longer expects a decision to come in the next few days in particular.
Liquidity is a caveat. Total trading in the October line is under $100,000, small enough for a handful of orders to shift it.
Market Implications
One reading is that Saudi Arabia's willingness to strike on its own lowers the odds of direct American involvement. Washington can support its ally without crossing the line that resolves the contract.
A second reading is that the risk is being underpriced. The Houthis have fired missiles toward Riyadh three days in a row, and a Houthi official has named Saudi oil facilities as targets. A strike on energy infrastructure could change the calculation in Washington quickly.
What To Watch
Three things would move these lines: a decision in Washington on Yemen, Riyadh's own account of the overnight raids and any hit on Saudi oil installations. A drop in the Oct. 15 line below 97 cents would be the first sign traders see a decision coming this week.