Seoul shares soar over 6% on revived AI optimism, SK hynix earnings

Seoul's stock market experienced a dramatic one-day rally. The KOSPI gained 374.1 points, or 6.63 percent, to close at 6,012.44. Technology shares led the advance after SK hynix reported record quarterly earnings and announced a large shareholder-return program. The Korean won weakened against the dollar during the same session.

SK hynix shares rose 10.89 percent to 1.49 million won. Samsung Electronics, Korea's largest company by market value, jumped 9.01 percent to 242,000 won. SK Square, SK hynix's parent company, advanced 11.23 percent. Samsung Electro-Mechanics gained 8.74 percent. These gains showed that investors were buying across major technology groups, not just one chipmaker.

The rally was strong enough for the Korea Exchange to activate a buy-side sidecar for five minutes. Foreign investors bought 815.83 billion won net, while institutions bought 960.79 billion won. Individuals sold 1.8 trillion won net. Investors were also watching the Federal Reserve's upcoming interest-rate decision for clues about future US rates.

SK hynix is a South Korean semiconductor company and the world's second-largest memory chip maker, according to the article. It produces memory chips used to store and process digital information. Because semiconductors are a major part of South Korea's stock market, news about SK hynix can influence investor confidence far beyond the company itself.

The company reported record-high third-quarter revenue and operating profit. Those results reflected robust memory-chip demand during the artificial-intelligence boom. SK hynix also announced a shareholder-return program worth more than 100 trillion won, or $75.3 billion, for 2026. The combination of strong profits and planned payouts made the company especially attractive to investors.

Its shares rose 10.89 percent, while Samsung Electronics and other technology companies also rallied. Analyst Lee Jae-won said the results eased concerns about whether the AI-driven rally could last and whether the memory-chip cycle might be nearing a peak. That reaction helped lift the wider KOSPI sharply.

The KOSPI gained 374.1 points, or 6.63 percent, to close at 6,012.44. It reached 6,032.28 during the session. This was a broad market move, not merely a rise in one company. Advancers outnumbered decliners 580 to 288, showing that many listed shares participated in the rally.

A 6.63 percent increase means an investment tracking the entire index would have gained roughly 6.63 percent before fees and taxes that day. For example, a 1 million-won investment moving exactly with the index would rise by about 66,300 won. Individual holdings could perform better or worse, depending on their share prices and sector exposure.

The move also showed unusually strong buying pressure. Foreigners and institutions bought a combined net total of more than 1.7 trillion won, while individuals sold 1.8 trillion won. The exchange activated a buy-side sidecar, reflecting the speed of the futures-market rise. Large daily gains can reward investors, but they also signal heightened volatility.

Artificial-intelligence systems require large amounts of memory-chip capacity. As AI-related demand grows, chipmakers can receive more orders and sell more products. The article reports that robust memory-chip demand during the AI boom helped SK hynix produce record-high revenue and operating profit in the third quarter.

Those results gave investors concrete evidence that AI demand was already translating into business performance. SK hynix also announced a shareholder-return program worth more than 100 trillion won, or $75.3 billion, for 2026. Strong profits make such returns appear more financially supportable, while the promise of payouts can make the shares more appealing.

The market reaction was immediate. SK hynix shares soared 10.89 percent, helping drive the KOSPI 6.63 percent higher. Analyst Lee Jae-won said the results reduced worries about the sustainability of the AI-driven rally and a possible peak in the memory-chip cycle. Investors still faced uncertainty, including the Federal Reserve's pending rate decision.

A buy-side sidecar is a temporary market-control measure. It suspends program-trading buy orders for KOSPI-listed stocks for five minutes. The mechanism is designed to slow unusually rapid buying and give the market time to absorb a sharp move rather than allowing automated orders to accelerate it.

The Korea Exchange activates this measure when KOSPI 200 futures rise at least 5 percent and remain at that level for at least one minute. During Wednesday's rally, the exchange triggered the sidecar shortly before 11 a.m. It was the second straight session in which the measure was activated.

The trigger showed how forceful the technology-led rally had become. SK hynix and Samsung Electronics posted large gains after SK hynix reported record earnings. The sidecar did not end the session's advance: the KOSPI ultimately closed 6.63 percent higher. It instead created a short pause in program buying during an exceptionally fast market move.

The Korean won weakened against the US dollar, trading at 1,337.7 won per dollar at 3:30 p.m. It lost 10.7 won from the previous session's close. Government bond prices fell, which means their yields rose. The three-year Treasury yield increased 4.1 basis points to 3.799 percent, while the five-year yield rose 5 basis points to 3.949 percent.

US interest rates matter because they influence the relative appeal of dollar and won assets. If the Federal Reserve raises rates or signals that rates will stay high, dollar assets can become more attractive. That can strengthen the dollar against the won. Korean markets may then face pressure as investors reassess currency risk and capital flows.

Higher US rates can also push Korean interest rates and bond yields upward, especially when markets expect Korea to maintain competitive returns. The article did not state the Federal Reserve's decision. Investors were awaiting it for signals about the future path of US rates, alongside assessing the technology-stock rally.

Memory chips are semiconductor components that store digital information. Computers and other electronic systems use them to hold data and instructions temporarily or for longer periods. Their performance and capacity matter because modern applications must handle increasingly large volumes of information.

Artificial-intelligence systems process huge datasets and perform many calculations. They therefore require substantial memory capacity to keep data close to computing processors and move it quickly during training and use. As more companies build and operate AI systems, demand for suitable memory chips can rise. The article connects this trend with robust memory demand and SK hynix's record results.

SK hynix reported record third-quarter revenue and operating profit amid the AI boom. Investors interpreted that performance as evidence that AI demand could produce real profits, not merely excitement. The company announced more than 100 trillion won in shareholder returns for 2026, and its shares rose 10.89 percent. The broader Korean market rallied as confidence in the chip cycle strengthened.