AI has carried the stock market. An industry pause could pull the rug out, warns this Wall Street giant.

Citigroup is flagging a concentration risk that has quietly underpinned this year's equity gains: the market's reliance on artificial intelligence. In a note to clients, the bank cautions that if progress in AI model development slows, the earnings revisions tied to that theme could weaken — and those upward revisions have been a key driver of stock performance in 2025.

The mechanism matters more than the prediction. Equity prices tend to track expectations for future profits, so when analysts raise earnings estimates, stocks often follow. Much of that upward revision activity has clustered around AI-linked companies and their suppliers. A pause in model breakthroughs would not necessarily mean AI spending stops, but it could slow the pace at which analysts feel confident raising forecasts.

For investors, the takeaway is about breadth, not timing. A market whose gains lean heavily on a single narrative is more sensitive to any evidence that the narrative is stalling. Watch upcoming earnings guidance, capital-expenditure commentary from major technology firms, and the pace of new model releases as signals of whether that revision momentum is holding or fading.