Markets
The Kospi Closed 3.3% Higher on Wednesday After a 4.8% Surge Triggered a Buy Sidecar. Samsung and SK Hynix Gained Almost 6% After SpaceX and Super Micro
One day after falling 3.73% to 5,552.74, Seoul's Kospi opened higher on October 21 and reached 5,816.43, up 4.75%, after SpaceX's first profit and Super Micro's raised outlook lifted Nasdaq 100 futures 1%. Kospi 200 futures rose more than 5% at 10:51 a.m., triggering the Korea Exchange's buy-side sidecar for the first time in two months. SK Hynix touched 1,329,000 won, up 8.7%, and Samsung Electronics 228,000 won, up 7.8%; the index closed at 5,735.66, up 3.29%, with SK Hynix up 5.8% and Samsung 5.7%. The Nikkei closed 0.85% higher, Hong Kong fell 0.7% and NextDC lost 42% in Sydney.
The Korean market, which has been the AI trade's thermometer for three weeks, swung from one extreme to the other in two sessions. The Kospi had fallen 3.73% on Tuesday, October 20, to 5,552.74 as SK Hynix headed for its lowest close since April and a Korean AI data-centre company fell 32% on its first day of trading. On Wednesday it opened 1.8% higher, after SpaceX reported .56 billion of quarterly AI revenue and Super Micro raised its revenue outlook by about billion in the New York evening, and climbed through the morning to 5,816.43, up 4.75%, at the high. The buying was foreign: net purchases were reported at between 131 billion and 197 billion won by mid-morning, after a week in which foreign investors had been net sellers of Korean chips on most days.
The speed of it tripped the exchange's brake. At 10:51:56 a.m., with Kospi 200 futures up more than 5%, the Korea Exchange triggered a buy-side sidecar, which suspends program buy orders for five minutes, until 10:56:56; it was the first buy sidecar in two months, and the mirror image of the sell-side curbs that fired during the 18.8% fall in the first half of October. SK Hynix rose as much as 8.7% to 1,329,000 won and Samsung Electronics 7.8% to 228,000 won; the Kosdaq rose 2.8% at its high. Then the afternoon took part of it back. By 2:15 p.m., with Nasdaq 100 futures still up 0.7%, the index had slipped to 5,688, up 2.4%, before a late recovery took it to a close of 5,735.66, up 182.92 points or 3.29%. SK Hynix closed at 1,294,000 won, up 5.8%, Samsung at 223,500, up 5.7%, and the Kosdaq rose 1.4%; the won firmed to 1,324 per dollar from 1,330.
The rest of the region was calmer and more mixed. Tokyo's Nikkei 225, which had fallen 1.30% on Tuesday with SoftBank down 6%, closed 0.85% higher at 64,621.24 after reaching 65,405 in the morning; Taiwan's Taiex rose 1.3% to 46,887.77 after a high of 47,255; Hong Kong's Hang Seng fell 0.68% to 23,706. Jakarta gave back 0.8% after Tuesday's 5.65% rebound from its six-year low, with Bank Indonesia's rate decision due in the afternoon and the rupiah near 17,970 per dollar. Australia's ASX 200 was flat, which hid the day's worst stock in the region: NextDC, the data-centre developer, fell 42% after a power delay at a Melbourne site cut its fiscal 2027 revenue guidance by about A40 million. Brent crude was back above 10.
What the session showed is that the Korean chip trade now moves on US after-hours prints rather than on anything in Seoul. SpaceX and Super Micro were enough for a 4.8% opening rally and a sidecar; the absence of any Korean news was enough for the index to give up half of it by mid-afternoon before closing up 3.3%. The next signal arrives at the same hour on Thursday morning, from Meta's capital-spending guidance and Lam Research's December-quarter outlook, published after Wednesday's New York close. A market that has fallen 3.7% and risen 3.3% on consecutive days, on other people's earnings, has told you what Thursday's open will look like before anyone in Seoul has read the reports.