Santoli's Wednesday market wrap-up: Momentum stocks stay under pressure

(These are the market notes on today's action by Mike Santoli, CNBC's Senior Markets Commentator. See today's video update from Mike above.) Another flurry of treacherous rotation roiled the tape, though by the closing hour the swirling currents were showing signs of slowing. The highest-momentum, most-expensive, most-crowded stocks — the sort that drove the Nasdaq-100 up 40% and the S & P 500 High Beta ETF (SPHB) up 60% over four months – remained under pressure, peaking at midmorning. While largely mechanical and tactical, the action coincides with a moment of broad reconsideration of the trajectory of the AI-investment theme and the assumptions underlying it. Meta Platforms is now down nearly 5% on the week, as it again is said to be reorienting its AI efforts. Chat GPT5 has been deemed