Key facts
- South Korea's KOSPI index surged 5.1% to 8,902.97 on Thursday.
- The Korea Exchange activated a buy-side sidecar for the KOSPI, suspending program trading for five minutes.
- The rally was driven by strong quarterly earnings from U.S. chipmaker Micron Technology.
- Semiconductor shares led the gains on the Seoul stock market.
- A buy-side sidecar is triggered when the KOSPI 200 Futures index increases 5% or more for at least one minute.
Seoul shares opened higher on Thursday, June 25, 2026, with the benchmark Korea Composite Stock Price Index (KOSPI) surging 5.1 percent to 8,902.97. The rally was primarily driven by strong quarterly earnings from U.S. chipmaker Micron Technology, which boosted semiconductor shares.
As a result of the sharp rise, South Korea's bourse operator, the Korea Exchange (KRX), activated a buy-side sidecar for the KOSPI. This measure led to a temporary suspension of program trading for KOSPI-listed shares for five minutes shortly after the market opened.
A buy-side sidecar is a mechanism designed to curb excessive volatility and is triggered when the KOSPI 200 Futures index increases by 5 percent or more for at least one minute.
Earlier in the week, four additional South Korean-operated vessels had exited the Strait of Hormuz, bringing the total to six following a U.S.-Iran ceasefire. This development, alongside bargain hunting, contributed to the market's rebound from a prior steep decline.