Stew, a 35-year-old from Montana, has spent the past year and a half casually placing sports bets since downloading the Kalshi app. A few weeks ago, however, after reading online chatter about increased late-night pizza deliveries to the Pentagon, he decided to try something different. He put $10 (£7.50) on a prediction that Iran’s Ayatollah Ali Khamenei would be “out” of power by 1 March. The wager pushed the boundaries of what Americans are legally permitted to bet on. Prediction markets —