The US-Iran Ceasefire Is Very Likely to Hold Through Late September

The guns between the United States and Iran are very likely to stay quiet through September 20. That is not a hope or a diplomatic talking point — it is the overwhelming weight of real money on the line, with the contract for the ceasefire holding through that date sitting at 94% and having gained ground in the last 24 hours. The argument is not that peace has broken out in any permanent sense, but that the immediate incentives on both sides are powerfully aligned toward keeping this pause intact for the next several weeks.

The evidence across the full landscape of Iran-related contracts reinforces the case. The probability of a U.S. invasion of Iran before 2027 sits at just 16%, down another point in the last day, and the chance that Iran's regime falls before 2027 is priced at a mere 6%. Those are very unlikely outcomes. Meanwhile, the probability of a U.S.-Iran diplomatic meeting by March 2027 is 62% and ticking upward. Together, these numbers describe a world in which both sides are managing a fragile but real truce rather than sliding back toward open confrontation. The September 25 contract — asking whether the ceasefire survives five more days beyond the 20th — sits at 85%, suggesting the market sees the pause as likely to extend even further. The October 31 contract, however, has shed more than 25 points in a single day, a sharp signal that confidence in a very long-duration hold is fading fast.

Why does the consensus hold at 94% for September 20? The most plausible answer is that both Washington and Tehran have absorbed the costs of the recent confrontation and neither is eager to restart it on a short timeline. Iran's regime, priced at just 6% to fall before 2027, is not a government on the verge of collapse — it retains enough institutional cohesion to make a deliberate choice to honor a pause. The United States, for its part, has not moved toward seizing Iranian uranium or dismantling Iranian infrastructure: the contract asking whether the U.S. obtains Iranian enriched uranium by year's end sits at 6%, and the question of whether Kharg Island leaves Iranian control by December 31 is also at 6%. Those are virtually impossible outcomes on the current trajectory. Something real is holding — likely a mutual calculation that the costs of resumption outweigh the gains.

What could break it? The single most credible threat is an incident that neither capital orders but neither can control — a naval confrontation in the Strait of Hormuz, a proxy militia strike that crosses a red line, or an Israeli action that drags Washington back in before September 20 arrives. The Strait of Hormuz traffic contract returning to normal by September 30 is priced at just 1%, meaning the waterway remains disrupted and the risk of an accidental escalation there is non-trivial. A final nuclear deal by December 31 is priced at only 10%, which means the underlying dispute is unresolved — the ceasefire is a pause on top of a live conflict, not a resolution. Any spark in that environment could unwind the near-term calm quickly.

This argument is the market's, decoded — not investment advice.