Bearish bets across US stocks are surging to a record high even as markets climb, signaling deep anxiety about the durability of a rally that has lifted the S&P 500 18% since late March. The surge in short positions reflects growing unease that the advance, heavily driven by megacap technology shares, may be vulnerable to a reversal if AI enthusiasm wanes or earnings disappoint.

Hedge funds and institutional investors are increasing defensive positioning despite the benchmark index trading near all-time highs. The divergence between rising equity prices and escalating bearish wagers highlights a market split: momentum traders chasing the rally versus skeptics betting on a pullback triggered by valuation concerns or macroeconomic shocks.

Strategists note that short interest often peaks near market tops, but the current buildup is unusual for its scale relative to recent trading volumes. Options markets also show elevated put buying, particularly on semiconductor and large-cap tech names. While the S&P 500's gain underscores strong bullish sentiment, the simultaneous record in short bets suggests many participants are hedging against a sudden shift in risk appetite.