The markets had a remarkable day on Thursday, with strong showings from all the major indexes and a standout performance from one in particular. The Nasdaq Composite clinched its best month since April 2020 and its seventh record close of the year, thanks to a rally in semiconductor stocks. Chip stocks were doing all the heavy lifting—the iShares Semiconductor ETF surged 2.4% today on signs that Big Tech is still splurging on building out AI.