SK Hynix Up 5%, Infosys Down 2% After Anthropic’s Filing

SK hynix rose 5.18% to 1.34 million won, while Samsung Electronics rose 4.23% to 222,000 won in Seoul on Tuesday, 27 October, Yonhap News Agency reported. The KOSPI index closed 3.09% higher at 5,638.34. Yonhap said investors felt more confident after Anthropic revealed strong revenue growth in documents filed for its planned US initial public offering (IPO). Falling oil prices also helped investors feel more willing to take risks.

That same morning in Mumbai, Infosys shares fell 2.31% and Tata Consultancy Services (TCS) fell 2.09% during trading, Business Today reported at 11:08 IST. All 10 stocks in India's NSE IT index were down.

Today's stories in about a minute (27 Oct 2026).

What Moved in Seoul

The Korea Exchange activated a special measure called a buy-side sidecar at 10:13 a.m., Yonhap reported. It stopped buy orders through program trading for KOSPI-listed shares for five minutes. This was the first time the measure had been used in four trading sessions. The rule is triggered when KOSPI 200 futures rise by at least 5% and stay at that level for one minute or longer.

Foreign investors bought 592.97 billion won more in shares than they sold. Institutions did the same with 280.38 billion won, while individual investors sold 947.78 billion won more than they bought, Yonhap reported. SK Square, the parent company of SK hynix, rose 7.67%. Samsung Electro-Mechanics gained 7.42%.

Lee Kyoung-min, an analyst at Daishin Securities, told Yonhap: “Foreigners and institutions snapped up major semiconductor stocks amid renewed investment sentiment over AI, despite lingering macroeconomic concerns.”

What Moved in Tokyo

Japan's Nikkei 225 rose 1.73% to close at 63,268.37. It had gained more than 2% earlier in the day. The broader Topix index rose 0.61%, Reuters reported. Advantest, which makes equipment for testing chips, jumped 8.98% and gave the Nikkei its biggest boost. SoftBank Group rose 4.95%, while Tokyo Electron gained 3.07%.

Reuters said the Nikkei, which has many technology stocks, often moves in the same direction as the Philadelphia Semiconductor Index in the United States. That US index rose 2.8% overnight. Daisuke Hashizume, a senior strategist at Daiwa Securities, told Reuters: “The market was relieved by the news about Anthropic’s IPO, while heavyweight technology stocks tracked a rise in the US chip index.”

What Moved in Mumbai

Indian IT stocks had recently risen because investors hoped money would move away from AI stocks around the world, Business Today reported. But the stocks fell after Anthropic announced plans for an IPO and Meta announced that it was seeking $95 billion through share offerings. Business Today said these developments raised “fears that hopes of a ‘reverse AI’ trade may be premature.”

Business Today added that Infosys fell especially sharply after at least four brokerages lowered their ratings on the stock in a single day. We covered the Indian market and what Infosys and TCS report about their own AI revenue in our report on Indian IT earlier this morning.

What the Filing Disclosed

Anthropic's S-1 filing says that, as of 30 June 2026, it had about $321.4 billion in future lease obligations that had not yet started. These leases were mainly for computing and infrastructure capacity. The filing also listed about $265.6 billion in fixed purchase commitments or purchases with minimum guaranteed amounts. We reported these figures in our report on Anthropic's computing leases that had not yet started.

Connecting the Coverage

Seoul's gains came one day after Reuters reported that China's STAR50 index, which tracks leading AI and semiconductor companies, had fallen 40% in less than four months. This erased about $480 billion in market value. We covered this in our report on China's AI index losing $480 billion.

On memory technology, Nvidia's own Vera Rubin NVL72 webpage now lists HBM4 memory bandwidth of 19.2 TB/s per GPU. That is lower than the 22 TB/s listed in an archived version of the page from August. We reported this change in our report on Vera Rubin memory bandwidth.

The Structural Read

Our reading is that the rise in Seoul was large enough to trigger an exchange rule. The Korea Exchange's buy-side sidecar activates when KOSPI 200 futures rise by at least 5% for one minute. Yonhap reported that the measure was activated at 10:13 a.m.

Our reading is that foreign investors and institutions were the main net buyers in Seoul. According to Yonhap, they bought 592.97 billion won and 280.38 billion won more in shares than they sold, respectively. Individual investors sold 947.78 billion won more than they bought.

Our reading is that Advantest, a maker of chip-testing equipment, had the biggest gain among the companies named in the Tokyo report. Its shares rose 8.98%, ahead of SoftBank Group's 4.95% gain, according to Reuters.

Three Implications

FOR CHIP AND MEMORY INVESTORS Yonhap and Reuters both reported that AI-related chip stocks led Tuesday's gains in Seoul and Tokyo after Anthropic filed its IPO documents.

FOR THE ‘REVERSE AI’ TRADE Business Today reported that Indian IT stocks had risen because investors expected money to move away from AI stocks. Tuesday's decline raised concerns that this trend might not continue as expected.

FOR UNDERSTANDING THE MOVES Yonhap also pointed to falling oil prices, while Reuters highlighted the rise in the US chip index. The Indian share-price figures were recorded during trading, not at the close. It is not known how much of each market move was caused by Anthropic's filing.

The Business Engineer Lens

This story connects with the Business Engineer framework called The AI Memory Chokepoint.

The framework sums up its main idea in one sentence: “Memory is becoming the new compute.”

Our reading is that the two memory makers, SK hynix and Samsung Electronics, rose 5.18% and 4.23% in Seoul on Tuesday, according to Yonhap. The framework was published in December 2025 and does not discuss Anthropic's filing or these share-price moves.

What Is Not Established

Yonhap mentioned falling oil prices as well as Anthropic's filing. Reuters linked the Nikkei's movement to the US chip index. For these reasons, it is not known how much of each market move was caused by the filing. Business Today also linked the fall in Indian IT stocks to Meta's share offering and the lower ratings that brokerages gave Infosys.

The Seoul and Tokyo figures show the final closing prices. The Indian figures show prices during trading on Tuesday morning and may have changed by the market close.

The Bottom Line

On Tuesday, the day after Anthropic filed its IPO documents, SK hynix closed 5.18% higher and Advantest rose 8.98%. In Seoul, the exchange stopped program-trading buy orders for five minutes. In Mumbai, Infosys and TCS were trading more than 2% lower. Business Today said the fall in Indian IT stocks raised “fears that hopes of a ‘reverse AI’ trade may be premature.”