OpenAI’s soaring valuation helps push U.S. stocks to fresh record highs

A blockbuster funding round for OpenAI and a bold valuation north of $500 billion helped drive U.S. stocks to new all-time highs Thursday, despite looming concerns over a prolonged government shutdown.

The privately held AI company announced key partnerships with South Korean tech giants Samsung Electronics and SK Hynix, who will supply memory chips for its ambitious “Stargate” infrastructure project. The news sparked a rally in semiconductor stocks and added to investor optimism around the AI boom.

“The main, dominant story is AI and technology,” said Keith Lerner, co-chief investment officer at Truist Advisory Services.

The Nasdaq Composite gained 0.4%, and the S&P 500 edged up 0.1%, both closing at record levels for the 30th time this year. The Dow Jones Industrial Average rose 0.2%, or 78.62 points, marking its 10th record close of 2025.

Gains remained concentrated in megacap tech stocks, as investors appeared comfortable waiting out the lack of economic data caused by the shutdown.

“Today was the first real day that we got to experience a data void,” said Vail Hartman, U.S. rates strategist at BMO Capital Markets. With jobless claims data missing and Friday’s jobs report likely delayed, traders turned to alternative indicators like the Chicago Fed’s labor metrics.

Prediction markets currently expect the shutdown to extend into at least the end of next week, threatening further delays in key reports such as the monthly jobs data.

“Investors have shifted focus to earnings season in two weeks,” Lerner added, noting that semiconductors appear relatively insulated from Washington’s disruptions thanks to continued AI momentum.

The Philadelphia Semiconductor Index jumped 1.9%, driven by gains in Nvidia (+0.9%) and Broadcom (+1.4%).

Still, some analysts warn the rally may be outpacing fundamentals. “It’s mostly momentum at this point,” said Robert Haworth, senior investment strategist at U.S. Bank Wealth Management. “We’ll need strong earnings to validate it.”

Attention now turns to Friday’s ISM Services Index — one of the few major economic indicators unaffected by the shutdown. A prolonged absence of government data could eventually test market confidence.

In the meantime, investors are increasingly relying on corporate guidance. With banks set to kick off earnings season soon, early insights into loan growth and consumer behavior may prove more influential than any postponed government release.