The S&P 500 finally breached the 7,500 level on Thursday, closing at a record 7,501.24. But if you ask the crowd on Polymarket, that milestone might be short-lived. Traders on the prediction market are assigning a 99% probability that the benchmark index will open lower on Friday, as futures retreat and investors weigh stretched valuations, AI-driven market concentration, and the ongoing U.S.-China summit.

Thursday's close was another feather in the cap of the AI-fueled rally, but it came with a side of caution. Markets are also tracking tensions involving Iran and the Strait of Hormuz, as well as developments from the U.S.-China summit, where officials discussed trade, tariffs, Taiwan, and Iran. Some investors are getting nervous about how narrow the rally has become—technology megacaps are still accounting for a disproportionate share of gains.

Still, it's not all doom and gloom. Strong corporate earnings and continued enthusiasm around artificial intelligence remain key supports for equities. Shares of Cisco Systems (CSCO) surged over 13% on Thursday after the company posted stronger-than-expected quarterly results and announced job cuts. NVIDIA also gained more than 4% after Reuters reported the U.S. had cleared several Chinese firms to purchase its H200 chips.

But strategists are warning that the market's advance is becoming increasingly dependent on a handful of tech stocks. "That broadening trade has really fizzled out," Keith Lerner, investment chief at Truist Advisory Services, told CNBC's "Closing Bell: Overtime." Investors also remain alert to geopolitical risks tied to Iran and elevated oil prices, which could reignite inflation concerns and pressure broader market sentiment.

S&P 500 futures were down 0.37% early Friday. Despite the expected pullback, the index is headed for its seventh straight week of gains. For context, Thursday's Polymarket bet on the S&P 500 opening higher resolved "Up" after the index opened at 7,454.40, above Wednesday's close of 7,444.25. That contract saw traded volumes of approximately $146,284 before settling.

So, will the S&P 500 open lower today? The crowd has spoken—but in markets, the crowd isn't always right.