US AI hardware and semiconductor sectors plunged sharply, with Lumentum falling over 11%.

AI hardware and semiconductor stocks sold off sharply on November 4, with the Philadelphia Semiconductor Index falling more than 3.8% and optical communications name Lumentum dropping over 11%. The leveraged SOXL semiconductor ETF lost more than 11%, while Coherent and Marvell each fell over 8%, SanDisk and Seagate dropped more than 7%, Western Digital slid over 6%, and Micron and Intel each declined more than 5%; SK Hynix and Arm fell over 4%, ASML nearly 4%, and compute leaders Nvidia, TSMC and Broadcom each lost more than 2%. Qualcomm was the lone standout, gaining over 1% against the trend. The broad-based retreat across optical, memory and equipment names signals renewed pressure on AI infrastructure sentiment after a strong run. Investors will watch whether the pullback deepens in memory and optical suppliers or stabilizes around Nvidia and TSMC, and whether Qualcomm's relative strength extends.