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

Citigroup is flagging a risk that has become central to this year's equity rally: the market's heavy reliance on artificial intelligence. According to the bank, AI-related developments have been a key driver of earnings revisions, which in turn have supported stock gains. If the pace of AI model breakthroughs were to slow, those upward revisions could weaken — and with them, a major pillar of current valuations.

The point is not that a slowdown is imminent, but that the market's foundation is narrower than it may appear. When a single theme carries a disproportionate share of index performance, the market becomes more sensitive to any disappointment in that theme's trajectory, whether from technical limits, regulatory friction, or simply longer development cycles.

For investors, the takeaway is about concentration risk rather than prediction. Watching earnings revision trends, capital spending plans from major AI players, and the cadence of new model releases can offer early signals of whether the AI narrative still has room to run — or whether the market may need other sectors to step up.