South Korea’s KOSPI Plunges 8.2%, Triggers Circuit Breaker Amid Tech Selloff

South Korea’s KOSPI index plunged more than 8% on Thursday, triggering a marketwide circuit breaker as a global technology stock selloff accelerated following stronger-than-expected U.S. inflation data and growing concerns over artificial intelligence investments.

The benchmark KOSPI dropped 8.2% to 5,514.96 points, its lowest level since late July. The latest decline brought weekly losses to 16.9%, while the index has fallen 24.4% over the past three months.

South Korean equities suffered heavier losses than other major Asian markets. Japan’s Nikkei 225 declined approximately 5%, while Taiwan’s Taiex slipped 3.4% amid widespread selling in semiconductor stocks.

Trading on the KOSPI was suspended for 20 minutes after the index remained at least 8% below its previous closing level for one minute. The circuit breaker mechanism aims to limit panic selling and provide investors time to evaluate market conditions.

Thursday marked the 10th circuit breaker activation in 2026 and the 16th in the exchange’s history. The previous trading halt occurred on July 29.

The sharp decline followed September U.S. consumer price index data showing annual inflation accelerated to 3.7%, exceeding economists’ forecasts. The figures renewed expectations that the Federal Reserve could maintain elevated interest rates or pursue additional monetary tightening.

Wall Street also experienced significant losses overnight, with the Nasdaq Composite falling 1.9%. Meanwhile, the Philadelphia Semiconductor Index recorded its sixth consecutive losing session.

South Korea’s leading chipmakers faced intense selling pressure. Samsung Electronics shares plunged 9.7%, while SK Hynix dropped 11.1%.

Other major losers included Sanil Electric, down 16.9%, Samsung Electro-Mechanics, which declined 16.8%, and Hansol Technics, which lost 15.2%. Daeduck Electronics and IsuPetasys also fell 15.1% and 14.9%, respectively.

Investor concerns have intensified over the sustainability of AI infrastructure spending and increasing competition from Chinese memory chip manufacturer ChangXin Memory Technologies, potentially threatening established semiconductor producers.

The downturn represents a dramatic reversal from June, when AI-driven optimism pushed the KOSPI above 9,000 points.

With the index now more than 40% below its 52-week high of 9,385.59, investors are increasingly questioning technology stock valuations, semiconductor earnings prospects, and the durability of the AI investment boom.