South Korea's KOSPI index opened up 4.95% at 8,526 points on Monday following news of a cease-fire agreement between the U.S. and Iran [1], [2].

This surge reflects a rapid shift in market sentiment as geopolitical tensions ease, encouraging both institutional and foreign investors to return to the Seoul market. The rally indicates a high level of sensitivity among Asian markets to stability in the Middle East.

The market experienced such a sharp increase that a buying sidecar was triggered six minutes after the opening bell [4]. This mechanism, which suspends program trading for five minutes to curb extreme volatility, has been activated 14 times so far this year [4].

Foreign investors recorded net purchases for a second consecutive session, contributing to the overall rally of approximately five percent [1], [3]. The positive momentum has also seen the recovery of 7,000 trillion won in market capitalization for top-listed stocks [6].

"The KOSPI is showing an upward trend, triggering a buying sidecar on the news of a cease-fire agreement between the U.S. and Iran," a YTN anchor said [7].

A reporter for YTN said the KOSPI started the day up 4.95% at 8,526 [2]. The reporter said the buying sidecar was activated because of the rapid rise in the early stages of trading [4].

“KOSPI opened up 4.95% at 8,526 points”

The immediate reaction of the KOSPI to the U.S.-Iran agreement demonstrates the deep integration of South Korean equities with global geopolitical stability. The triggering of a sidecar—a volatility control measure—highlights the intensity of the buying pressure. This shift suggests that investors had previously priced in a significant 'geopolitical risk premium' that was erased almost instantly upon the news of the cease-fire.