BlackRock and Citigroup used their latest 13F filings (quarterly U.S. equity holdings disclosures) to show a broader second-quarter 2026 push into AI infrastructure, expanding beyond NVIDIA to memory, semiconductor equipment and high-speed interconnects. As of June 30, BlackRock's U.S. equity holdings stood at about $6.73 trillion, up 18% from $5.72 trillion in the first quarter, while Citigroup's total holdings reached roughly $303 billion, nearly 30% higher quarter on quarter. BlackRock's top-10 concentration rose to 28.01% from 26.85%, with NVIDIA at $388.558 billion, Apple at $336.525 billion and Microsoft at $226.560 billion. Citigroup's top holdings were also centered on NVIDIA, Apple and Microsoft, but it paired that stance with put options (derivatives that gain value when prices fall) on the Russell 2000 ETF and Nasdaq 100 ETF. BlackRock sharply raised exposure to Micron, AMD, Applied Materials, KLA and Marvell, with Micron reaching $121 billion as its eighth-largest holding, while Citigroup lifted Micron's portfolio weight to 2.02% from 0.69% and increased its Micron put position by 1,535%. The shift came alongside sales of defensive names including Costco, Honeywell, Berkshire Hathaway Class B, AT&T and Johnson & Johnson, and was reinforced by cloud procurement commitments cited by Tom's Hardware that approached $2 trillion. The filings suggest major investors now see the opportunity in the full AI compute stack rather than a single chip leader, though the concentration leaves them exposed if AI capital expenditure slows, memory prices reverse or markets reassess returns.