KOSPI falls about 7.4% as AI profit fears and US inflation hit chips

Korean stocks plunged on Thursday, October 15, 2026. KOSPI fell about 7.4% and KOSDAQ about 7.3%, both estimates from closing prices. Trading was halted for 20 minutes after a circuit breaker, and sell-side sidecars were also triggered. Reports linked the sell-off to hotter-than-expected US inflation and rising Treasury yields, which revived fears of Fed rate hikes. Investors also worried about whether heavy AI spending would pay off and about rising competition in memory chips. Foreign investors sold ₩3.7 trillion of KOSPI shares, while they bought ₩219.2 billion of KOSDAQ shares. Among the biggest movers, SM Bexel rose 18.9% after reports it secured satellite battery technology with Seoul National University. S-1 rose 13.9% after announcing a ₩450 billion share buyback and cancellation. Techwing, VM and EugeneTechnology fell between 16.6% and 17.5%, and no clear reason was reported for those drops. Technically, Samsung Electro-Mechanics, SK Square and Hanmi Semiconductor each broke below support on heavy volume.