KOSPI Plunges 6% After Triggering Circuit Breaker as Samsung and SK Hynix Rout Rattles Seoul's Stock Market

SEOUL, South Korea — South Korea's benchmark stock index plunged 6% on Friday, briefly falling below 5,000 and forcing a market-wide trading halt, as a global selloff in artificial intelligence stocks hit the country's two chip giants.

The KOSPI fell 324.15 points, or 6.02%, to close at 5,059.65. The smaller KOSDAQ index finished 5% lower.

The rout extended a punishing week. The selloff followed a 5.28% drop on Thursday.

Trading halted

The selling began immediately at the open. Yonhap reported the KOSPI opened at 5,263.26, down 120.54 points, at 9:01 a.m. The exchange activated a 20-minute circuit breaker at 9:03 a.m. local time, suspending trading in stocks and derivatives.

The KOSPI hit an intraday low of 4,911.28, down 8.7% from Thursday's close of 5,383.80.

Circuit breakers have become common this year. Several outlets counted Friday's halt as the 11th of the year, while Yonhap counted it as the tenth.

Government steps in

Authorities moved quickly to calm markets. The government held an emergency meeting to review market conditions, and the index pared some of its losses before the close.

Chip giants hammered

South Korea's market is unusually dependent on two companies. SK Hynix and Samsung account for more than half of the KOSPI's weight, so a rout in memory chips drags the entire index lower.

SK Hynix slid more than 10%, while Samsung Electronics fell 6.35%.

The losses were enormous at the worst point. At the 9:03 a.m. halt, the two companies were about 225.6 trillion won, or roughly $166 billion, lower in combined market value than at Thursday's close.

The two firms sit at the center of the AI boom. They are the dominant makers of the high-bandwidth memory used in Nvidia's AI accelerators.

Why markets fell

The trigger came from Washington. Their boom depends on what U.S. cloud companies spend, and Democrats' midterm win has put that spending under scrutiny.

Analysts said the drop reflected sentiment rather than a collapse in demand. Invezz noted the shock was driven by AI-spending fears and a Wall Street tech selloff, not a confirmed collapse in Samsung's memory demand.

Foreign investors led the exit. Foreign funds dumped both stocks at once, taking the entire index down with them.

What's next

Investors will watch whether foreign selling continues next week and whether authorities take further steps to stabilize markets. The KOSPI's heavy concentration in two chipmakers means its direction will likely continue to track global sentiment toward AI spending.