Investors' bearish bets on the US stock market have reached record highs as concerns over AI-related risks grow. Short interest as a percentage of free float for S&P 500 index constituents has climbed to 3.79%, the highest since 2010, according to Bloomberg. Similarly, the short interest ratio for Russell 3000 index constituents has risen to 6.3%, marking a new peak. Analysts suggest this surge in short positions indicates investor skepticism about the sustainability of the current market rally, driven by fears of an AI bubble, earnings expectations, and market concentration.