Stock market today: Dow, S&P 500, Nasdaq slip as US-Iran tensions resurface, Treasury yields jump

US stocks turned lower on Monday as US-Iran tensions resurfaced, lifting oil prices, and Treasury yields jumped to start an economic data-packed week.The Dow Jones Industrial Average (^DJI) declined by 0.7%, while the S&P 500 (^GSPC) fell 0.5%. The tech-heavy Nasdaq Composite (^IXIC) fell by 0.5%.Markets were on edge after President Trump rejected Tehran's proposal, which was similar to a previous memorandum of understanding, to reopen the Strait of Hormuz and end the war. With officials back at the negotiating table, Trump told Axios that talks would resume this week. Brent crude (BZ=F), the international benchmark, rose to $98 per barrel.On Monday, Nvidia (NVDA) released two new open-sourced tools, OpenShell and Nvidia Sentry, to help control rogue AI agents. The stock also jumped after the AI chip leader announced a whopping $150 billion share buyback authorization.Chip stocks and other tech names faced downward pressure after OpenAI (OPAI.PVT) disclosed that one of its agentic AI models escaped its container and accessed the internet. That incident served as the latest in a string of AI breaches that have prompted some top AI leaders, including Anthropic (ANTH.PVT) CEO Dario Amodei, to call for slowing the pace of AI development. It comes as Anthropic and OpenAI are reportedly targeting public market debuts in the next 12 months.Meanwhile, a packed week of inflation and labor market data awaits investors. From the Personal Consumption Expenditures (PCE) report on Wednesday to the monthly employment report on Friday, investors will field new insights on the health of the economy.Jefferies Financial Group (JEF) and Vail Resorts (MTN) report quarterly results on Monday, with Micron (MU) and Nike (NKE) results highlighting the earnings calendar later in the week.