Microsoft hits $4T valuation, powering S&P 500 and Nasdaq to new records as AI optimism lifts tech-heavy markets.

The S&P 500 and the Nasdaq opened at record highs on Thursday, as blockbuster earnings from Meta and Microsoft signaled Big Tech's hefty artificial intelligence bets were paying off.

Wall Street on Thursday was largely higher, helped by post-earnings euphoria for tech titans Meta (META) and Microsoft (MSFT). Sentiment was slightly dampened, however, by economic data that showed stubborn inflation and weak personal spending.