Stock market today: Dow, S&P 500, Nasdaq mixed as AI optimism blots out US shutdown risks

Group 1: Market Overview - US stocks exhibited mixed performance, with the Nasdaq Composite rising 0.1%, while the S&P 500 and Dow Jones Industrial Average fell by 0.1% and 0.2% respectively, amid concerns over a potential US government shutdown [1] - The S&P 500 reached a new all-time high, closing above 6,700 for the first time, driven by a decline in ADP jobs numbers that reinforced expectations for interest-rate cuts [2] - The tech sector was buoyed by positive news from the AI industry, particularly with Nvidia reaching a record high, alongside gains for AMD and SK Hynix [2] Group 2: Company Highlights - OpenAI's valuation surged to $500 billion following an employee share sale, making it the most valuable startup globally, surpassing SpaceX [3] - Alibaba's stock experienced a significant increase after JPMorgan raised its price target by nearly 45% [3] Group 3: Labor Market Insights - Private data indicated that hiring plans are at their lowest since 2009, despite a decrease in layoffs, suggesting a softening labor market [6] - The upcoming September jobs report is expected to be delayed, contributing to uncertainty in the labor market ahead of the Federal Reserve's October rate decision [5][6]