Stocks closed April at records. But something's happening that could break the boom

Just as investors in April looked past the effect of the U.S.-Iran war to focus instead on a reignited artificial intelligence trade and strong corporate profits, a warning signal came from the bond market. On Thursday, the 30-year U.S. Treasury bond yield briefly rose above 5%. In early trading Friday, the 30-year yield stands at 4.979%. The 5% threshold is a level that Bank of America strategist Michael Hartnett calls the "Maginot Line" — referring to the French defensive system built to stop a German invasion in World War II — for the long-term bond. The 30-year Treasury bond also flirted with a 5% yield in late March, when stocks were hitting their lows from the war in the Middle East and yields were hitting their highs amid inflation concerns driven by higher oil prices. Then in April, the S & P 500 jumped more than 10%, its best month since November 2020, while the Nasdaq Composite surged 15%, its best one-month performance in six years. But lately the 30-year bond yield has returned to its late-March level as crude oil again pushes higher after dipping when the U.S. and Iran agreed to a ceasefire. While the violence has stopped for now, the Strait of Hormuz remains shut with no signal from Iran on when it might re-open. A U.S. naval blockade of the passageway — through which 20% of the world's oil passed before the war — is still in place. US30Y mountain 2026-02-27 U.S. 30-year treasury bond yield since February 27, 2026. …