Shares of U.S. technology megacaps tumbled on Monday as SpaceX fell for the third straight session and hyperscalers Alphabet and Amazon looked set to lose billions of dollars in market value, driven by AI spending concerns. SpaceX slid over 10% after last week's blistering post-IPO rally. The Elon Musk-led firm said it is launching a notes offering on Monday. Alphabet dropped 6%, set for its biggest one-day fall since May 2025 and on pace to erase more than $256 billion in market capitalization. Google DeepMind's senior research scientist and Nobel laureate John Jumper said he was leaving for AI startup Anthropic, the lab's latest high-profile exit. "This is more of a broader sector pullback on ongoing anxiety over tech companies' massive capital spend on the AI infrastructure," said David Wagner, head of equity and portfolio manager at Aptus Capital Advisors.