US stock market adds $1 trillion at open as geopolitical optimism floods Wall Street

The US stock market tacked on roughly $1 trillion in market capitalization right at the open, a staggering single-session jolt driven by growing optimism around a potential US-Iran peace agreement.

What’s driving the rally

The S&P 500 has surpassed $65 trillion in total market capitalization as of mid-June 2026, a milestone that reflects not just this single-day pop but a broader bull run fueled by artificial intelligence enthusiasm and robust IPO activity. Both the S&P 500 and Nasdaq have recently touched new all-time highs, propelled by the market’s appetite for AI-adjacent stocks.

The semiconductor rollercoaster

Micron Technology has been a standout performer, with its stock surging approximately 19% to push its market capitalization past the $1 trillion threshold. That jump came after UBS raised its price target on the chipmaker in late May 2026.

On June 5, 2026, chipmakers including Nvidia, Micron, AMD, and Broadcom collectively shed over $1.3 trillion in market value in a single session due to a sharp decline in confidence around AI stocks. The $1.3 trillion single-day wipeout happened barely a week before the $1 trillion open-day surge.

What this means for investors

For growth-focused investors, particularly those concentrated in tech and semiconductors, the challenge is navigating a two-speed market. Micron can gain 19% on a price target revision and then participate in a $1.3 trillion sector wipeout days later.

Equity valuations at these levels assume a relatively accommodative monetary environment. A $65 trillion S&P 500 leaves very little room for disappointment.

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