KOSPI triggers sell-side circuit-breaker for 2nd straight session; index swings 5% to close flat

The KOSPI 200 futures contract fell 60.24 points, or 5.13%, to 1,112.46 at 09:19:22 KST on Monday, triggering the sell-side program sidecar — a mechanism that suspends algorithmic sell orders for five minutes when futures decline 5% or more for a sustained period. It was the second consecutive activation following a similar event on May 15, when the KOSPI cash index briefly topped the historic 8,046.78 threshold before collapsing toward 7,100.

Despite the panic-sell open, buyers stepped in decisively during the afternoon session. The KOSPI closed at 7,516.04, up 0.31%, recording a full-session swing of over 5 percentage points. Domestic retail investors absorbed more than KRW 2.5 trillion (approximately $1.66 billion) in net purchases to offset persistent foreign selling.

Foreign investors have now sold on eight consecutive trading sessions, with morning net selling on May 18 reaching KRW 559.8 billion. The cumulative 8-day net sell total exceeds KRW 4 trillion ($2.66 billion). The USD/KRW rate rose to 1,502.60 (+5.09 won) during early morning trade, pushing through the psychologically significant 1,500 level for the second time in four sessions.

The immediate catalyst was a surge in US Treasury yields: the 10-year note reached as high as 4.6% intraday, breaking the 4.5% resistance level, while the 30-year bond exceeded 5%. US President Trump's comments on the possibility of infrastructure strikes against Iran added geopolitical risk premium. South Korean 10-year government bond yields rose 2.2 basis points to 4.239%.

Blue-chip names tracked the early sell-off: Samsung Electronics (005930.KS) closed at KRW 264,000 (-2.40%), SK Hynix (000660.KS) at KRW 175,000 (-3.79%), Hyundai Motor fell 4.43%, and LG Energy Solution declined 3.0%. Hanwha Aerospace gained 2.88% as defense names benefited from rising geopolitical tension.

After touching a historic high of 8,046.78 on May 15, the KOSPI has retreated 6.6% to 7,516. Market participants now focus on whether the Bank of Korea's Monetary Policy Committee meeting (late May) will provide stabilizing guidance amid rising US yield pressure.

Not investment advice. Verify all figures with primary sources before acting.