Key points
- Kospi opened 1.7% higher Monday on Korea's weekend AI deals, fell as much as 1.99%, then closed up 0.97%. Kosdaq rose 2.22%.
- The drop came from Shanghai. CXMT, China's largest memory chip maker, closed its first day up 465.82%, worth more than any other listed company in mainland China.
- Foreign investors sold a net 2.9039 trillion won ($1.98B USD) of Kospi stocks. Their two biggest sales were SK Hynix and Samsung Electronics, the companies that signed the deals.
- Individuals bought 1.98 trillion won ($1.35B USD) and institutions 862.3 billion won ($587M USD), which turned the index back up in the afternoon.
On July 27, Kospi closed up 0.97%, in the first Seoul session after Korean companies signed about $950 billion of AI and semiconductor agreements with American technology companies in San Francisco. The index opened about 1.7% higher on that news. At its lowest point in the session it was down 1.99%.
What happened in between was a stock market debut in Shanghai.
China's largest memory maker listed, and it went up 465%
CXMT, or Changxin Memory Technologies, is China's biggest maker of DRAM, the ordinary memory chips that go into phones, computers and servers. It listed Monday on the STAR Market, the Shanghai exchange's board for technology companies. We wrote about the offering last week when it priced, at 8.66 yuan a share. Monday was the first day anyone could trade it.
The stock opened at 49.50 yuan and closed its first day at 49.0 yuan, a rise of 465.82%. At one point during the day it was up 535.45%. That one session made CXMT worth 712 trillion won ($485B USD), which passed Industrial and Commercial Bank of China and made it the most valuable listed company in mainland China.
The offering itself sold 6.688 billion new shares and raised 12.5 trillion won ($8.51B USD), and it reaches 14.4 trillion won ($9.81B USD) if the over-allotment option is used in full. That is the largest offering in Asia this year and the second largest ever on the Chinese mainland, after Agricultural Bank of China in 2010.
CXMT is the fourth largest DRAM maker in the world. Samsung Electronics, SK Hynix and Micron are the three ahead of it, and together those three still hold more than 90% of the market, with CXMT in single digits. What worried Seoul was not the share it has now but what the company said it plans to do with the money. CXMT told investors it intends to more than double its production capacity by 2030.
Foreign investors sold the two Korean companies that just signed the deals
Foreign investors sold a net 2.9039 trillion won ($1.98B USD) of Kospi-listed stocks Monday. Of that, 2.2384 trillion won ($1.52B USD) came out of the electrical and electronics sector alone.
Their single largest sale was SK Hynix, at 1.1052 trillion won ($753M USD). Their second largest was Samsung Electronics, at 841.7 billion won ($573M USD). Those are the two Korean companies whose names were on the weekend agreements, Samsung's $200 billion memorandum with Broadcom and SK Group's $750 billion of AI infrastructure agreements with Nvidia, Microsoft and others.
Whether that selling was money moving from Korea into China is not confirmed. Bloomberg quoted a trader at Samsung Securities who said, "Some Asian hedge funds are selling Samsung and SK Hynix to buy CXMT." That is one desk describing what it saw, not a full accounting of where 2.9039 trillion won ($1.98B USD) went.
Korean buyers took the other side. Individual investors bought a net 1.98 trillion won ($1.35B USD) and institutions bought 862.3 billion won ($587M USD). The index turned back up in the afternoon, and both chip stocks finished green anyway. Samsung Electronics closed 1.80% higher and SK Hynix closed 3.24% higher. Naver rose 8.43% after news that Nvidia would take part in its AI plans.
What the analysts said
Lee Kyung-min, a researcher at Daishin Securities, described the day as two forces working against each other. "CXMT's strong debut on its first trading day raised expectations about Chinese memory makers expanding production capacity, and resulting supply volatility caused Korea's semiconductor sector to underperform relatively," Lee said. "However, inflows from institutions and financial investment prompted the index to attempt a rebound."
Lee continued, "Successive announcements of AI infrastructure cooperation between domestic companies and global tech giants created upward pressure on related sectors, while Middle East negotiation hopes and falling international crude prices also helped improve investment sentiment."
The won closed at 1,468.5 per dollar, 1.9 won weaker, and Kospi's low for the day was 6,557.39. The currency had started the day stronger on the easing Middle East situation and on lower oil prices, then turned as the foreign selling grew.
Why this one listing mattered so much here
Korea's two largest companies sell memory chips, and Kospi has spent 2026 moving with them. The index has been forced to pause 41 times this year, more than in all of 2008, mostly because Samsung Electronics and SK Hynix carry so much of it. So a new competitor raising more money in one offering than any other company in Asia this year is not a distant story in Seoul. It is a supplier of the same product, with government backing, now holding capital markets money too.
The technology distance is still real. CXMT makes standard DRAM, while SK Hynix leads the market for high bandwidth memory, the expensive stacked kind that AI accelerators use, and US export controls keep the most advanced chipmaking equipment out of Chinese factories. Doubling capacity in ordinary memory is a different thing from competing for the AI orders that the weekend agreements were about.
Meanwhile, SK Hynix reports its April to June results on Wednesday, July 29, and even the lowest forecast would beat what the company earned in all of 2025. Samsung Electronics gives its own full results the day after.
Korean market figures are from Herald Corp, Maeil Ilbo, Kookmin Ilbo and Newspim, all Korean-language reporting linked above, converted to US dollars at 1,468.5 won to the dollar, Monday's closing rate. This is general market commentary and not investment advice. Always do your own research and consider speaking with a licensed financial professional before making any investment decision.
Related coverage
- Elon Musk thanked Micron (MU) by name on Tesla's earnings call this week. That's what a real memory shortage looks like.
- Samsung just signed a $200 billion deal with Broadcom (AVGO), a 32-year TSMC (TSM) customer.
- SK Hynix (SKHY) reports earnings Wednesday. Even the lowest forecast beats what it earned in all of 2025.
