US stocks declined as renewed concerns about the impact of artificial intelligence on corporate profits, coupled with ongoing tariff uncertainties, dampened risk appetite. The S&P 500 index fell by 1%. Technology, delivery, and payment stocks were impacted as Citrini Research outlined potential risks posed by AI across various industries. DoorDash and American Express dropped more than 6.5%. An ETF focused on software companies declined 4.8%. IBM shares plummeted 13%, marking their largest single-day drop since October 2000, after Anthropic stated its Claude Code could assist in modernizing COBOL, a programming language primarily running on IBM computers. This news also contributed to further declines for cybersecurity software firms like CrowdStrike Holdings. In other individual stock movements, Domino's Pizza advanced 4.1% after reporting better-than-expected U.S. same-store sales and increasing its dividend. Novo Nordisk ADRs plunged 16% as its next-generation obesity injection, CagriSema, showed less weight loss in trials compared to a competing blockbuster drug from Eli Lilly. Eli Lilly's stock price rose 4.9%. Investors also carefully assessed the implications of trade developments. Previously, the Supreme Court rejected former President Trump's "reciprocal" tariffs on Friday, and the White House announced plans to replace prior tariffs on U.S. imports with a new measure involving a blanket 15% levy. "The back-and-forth on tariffs could be a significant market disruptor for the remainder of the year, although the volatility may be less severe than the initial shock last April," said Michael Landsberg of Landsberg Bennett Private Wealth Management. At the close of trading, the S&P 500 was down 1.04% at 6,837.75 points. The Dow Jones Industrial Average fell 1.66% to 48,804.06 points. The Nasdaq Composite Index declined 1.13% to 22,627.27 points.