Samsung Electronics, SK hynix tumble 6-7% in premarket as 'Black Thursday' fears mount

South Korean stocks were sliding sharply before Thursday's open as a US inflation shock combined with growing concerns over the debt burden and profitability of AI infrastructure investment. Samsung Electronics and SK hynix fell 6 to 7 percent in premarket trading. With the US consumer price index coming in above market expectations and doubts spreading over whether AI capital expenditure can translate into actual returns, selling pressure has intensified on large-cap semiconductor stocks.

At 8:41 a.m. Thursday on the Nextrade premarket, SK hynix was trading at 1.31 million won ($978), down 108,000 won (7.61 percent) from the previous session, while Samsung Electronics fell 15,000 won (6.47 percent) to 217,000 won. Samsung Electro-Mechanics and SK Square tumbled 8.37 percent and 8.45 percent, respectively, and Samsung SDI dropped 3.89 percent.

The Kospi closed Wednesday at 6,008.81, barely holding the 6,000 line, and a further decline in the regular session Thursday would raise the risk of the index breaking below that threshold. If the Kospi ends lower Thursday, it would mark seven consecutive sessions of losses — the first such streak in roughly two years and one month since September 2024.

Overnight on Wall Street, investor attention shifted from AI's growth potential to concerns about the recoverability of capital and the stability of funding. Shares of CoreWeave, an AI-focused cloud company, plunged after the firm faced mounting pressure to repay debt raised to expand its data centers, highlighting financial health concerns across AI infrastructure companies and weighing on market sentiment.

US inflation data added to the pressure. The September CPI rose 3.7 percent from a year earlier, topping the market consensus of 3.6 percent. The signal that price pressures are easing more slowly than expected weakened hopes for interest rate cuts and pushed government bond yields higher, stoking fears that growth stocks — including technology shares — could lose investment appeal.

Market analysts are noting that the benchmark for evaluating the AI investment cycle is shifting away from capital expenditure expansion toward actual profitability and cash flow. In the near term, sentiment toward semiconductor stocks is expected to hinge not only on US technology share movements and interest rate trends but also on the earnings and funding conditions of AI infrastructure companies.

"The domestic market is expected to open lower in the wake of the US September CPI beating consensus and the sharp simultaneous decline in US AI infrastructure stocks exposed to profitability concerns," said Han Ji-young, a researcher at Kiwoom Securities. "However, if the market does open lower, technical buying interest following seven consecutive sessions of sharp declines — along with the TSMC earnings release scheduled for later in the session — should help narrow the losses." Some analysts also cautioned that if the index fails to find support near current levels, volatility could persist.