A global technology selloff intensified overnight Tuesday, with South Korea's Kospi benchmark index plunging nearly 10% in one of its worst single-session declines in years, dragged lower by memory chip giants SK Hynix and Samsung Electronics, which each fell more than 12%. The circuit-breaker mechanism on South Korean exchanges was triggered during the session as the selling accelerated. The moves rippled into premarket trading in the United States, where Nasdaq 100 futures slid 3.1% — equivalent to a loss of more than 800 index points — while S&P 500 futures fell 1.4% and Dow futures declined 0.4%, or roughly 215 points.

South Korea's benchmark had surged approximately 95% in the year leading into Tuesday's session, making it among the best-performing major equity indexes in the world, driven almost entirely by speculative positioning in AI-related chipmakers, with SK Hynix briefly overtaking Samsung Electronics on Monday to become South Korea's most valuable listed company by market capitalization — a first in the two companies' histories. That event now reads less as a milestone than as a sentiment peak: by the close Tuesday, SK Hynix had surrendered a substantial portion of its recent gains.

European markets opened lower in sympathy, with ASML Holding falling 5% and ASM International declining more than 5% in early trading. The Euro Stoxx Technology index fell 3%, and the broader Stoxx 600 declined as investors recalibrated expectations for AI-infrastructure stocks across regions.

In the United States, premarket losses were widespread across the semiconductor complex. Micron Technology fell approximately 9%, Intel dropped 6.7%, Qualcomm slid 6.9%, and Western Digital declined 8.4%. The Roundhill Magnificent Seven ETF, which provides equal-weight exposure to Alphabet, Amazon, Apple, Meta, Microsoft, Nvidia, and Tesla, fell 0.74% to $63.62 in premarket trading, though losses were uneven across the group. Microsoft gained 1.1% in premarket on news of a 20-year power agreement with Chevron to supply natural gas electricity for its Texas AI data center, partially offsetting broader tech weakness.

The proximate catalysts for the global selloff are multiple. The SpaceX bond disclosure — revealing that the company's $85.7 billion IPO proceeds were largely pre-committed to retiring bridge loan debt — raised broader concerns about the sustainability of AI infrastructure financing. Alphabet's loss of two senior AI researchers to rival labs in 24 hours amplified worries about the value proposition of the hundreds of billions in AI capital expenditure being deployed by hyperscalers. And the Federal Reserve's updated dot plot, released following its June 16-17 meeting under new chair Kevin Warsh, showed nine committee members projecting at least one rate hike in 2026, a signal hawkish enough to reprice long-duration tech equities.

Wedbush Securities analyst Dan Ives described the U.S. premarket declines as 'white knuckles for tech stocks' driven by spillover from the Kospi rout, while characterizing the move as a pullback from an extended rally rather than the start of a structural bear market in AI equities. Investors are also looking ahead to PCE inflation data expected Thursday, which will offer the next major reading on whether the Fed's hawkish pivot is justified by underlying price trends. The April PCE reading showed headline inflation at 3.8%, the highest since May 2023, with the Fed's updated projections calling for 3.6% year-end PCE versus a prior forecast of 2.7%.

Defensive sectors continued to attract capital amid the risk-off move, with public storage REIT Public Storage gaining 4.4%, IBM rising 4.2%, and Accenture adding 3.3% in premarket trading. Energy stocks were broadly stable as the Iran nuclear inspection dispute — with Iran's foreign ministry contradicting Vice President JD Vance's optimism about imminent IAEA access — kept the Strait of Hormuz situation uncertain, supporting oil prices near recent levels.