Warren Buffett, Bill Ackman Loading Mega-Caps; Berkshire Exits Amazon, Triples MSFT

Berkshire Hathaway's first quarter filings under new CEO Greg Abel reveal a strategic pivot toward mega-cap technology and artificial intelligence plays. The conglomerate increased its stake in Alphabet Inc. to record levels while exiting its Amazon position entirely, a move that surprised markets given AMZN's dominant position in cloud and AI services. Simultaneously, Berkshire trimmed its Chevron holding, selling $8 billion worth as oil prices peaked, signaling a tactical reallocation from energy to tech. This is Buffett's most explicit endorsement of AI infrastructure investment in years, though it comes with a caveat: Berkshire also returned to airlines, building a $2.6 billion stake in DeltaHow much an option's price changes per $1 move in the underlying., suggesting Abel believes the broader market rotation is opportune.

Bill Ackman's Pershing Square Capital Management disclosed an even more aggressive move, nearly doubling its Amazon stake from 1.84 million shares to a near-doubling position, making AMZN its largest equity holding by quarter-end. Ackman also initiated new stakes in Broadcom and other semiconductor leaders, reflecting his conviction in the AI capex cycle. Ackman filed new positions in Microsoft (5.65 million shares) and maintained exposure to cloud and AI-adjacent names. These moves by two of Wall Street's most influential capital allocators signal that the recent mega-cap rally is not just retail enthusiasm or passive index flow, but institutional positioning ahead of earnings season.

The implications are significant for sector rotation and earnings expectations. Berkshire and Ackman are signaling that mega-cap tech dominance will persist, even as valuations extend. Their purchases also come after weeks of the Magnificent Seven outperforming, suggesting they believe the cycle has further to run. Ackman's move into Amazon is particularly notable, as it directly contradicts the rotation narrative: if he is doubling down on AMZN despite Friday's pullback, it suggests he sees the sell-off as a tactical opportunity rather than a structural reset. Conversely, Berkshire's exit from Amazon and shift toward Alphabet raises questions about whether AMZN's cloud moatA sustainable competitive advantage that protects long-term returns on capital. or AI positioning is being viewed as less compelling than Alphabet's.

Critics point out that 13F filings are backward-looking, reflecting positions as of March 31, and that both managers may have rebalanced substantially since quarter-end. Additionally, Ackman's track record of high-conviction bets has been mixed; his calls on high-profile situations have not always worked out. Some analysts also note that mega-cap tech valuations are so elevated that even double-digit earnings growth may not justify current multiples. However, the timing of these filings, released just as earnings season begins and macro headwinds intensify, suggests that professional investors are betting the upside remains intact despite near-term volatility.