What happened in Seoul
The sell-off in Seoul was swift and violent. The benchmark Kospi opened 335.80 points, or 5.59 per cent, lower at 5,673.01 and slid further through the morning, falling as much as 7.77 per cent to 5,539.51 by 10:30 a.m. local time, according to data reported by Yonhap News Agency. The tech-heavy secondary Kosdaq opened 4.79 per cent lower at 784.45 and kept sliding.
At the epicentre of the fall were the country's two chip giants. Samsung Electronics shares fell 9.05 per cent to 211,000 won, while SK Hynix tumbled 10.71 per cent to 1,267,000 won, wiping tens of trillions of won off the index's heaviest constituents in a single session. Selling was not confined to semiconductors: Hyundai Motor, the country's largest carmaker, fell more than 6 per cent as the rout spread.
Foreign investors led the exodus, off-loading a net 1.92 trillion won of main-board shares — roughly 1.4 billion dollars — by mid-morning. Retail and institutional buyers could not stem the decline.
Such was the speed of the fall that the Korea Exchange triggered sell-side trading curbs, known locally as sidecars, temporarily halting programmatic selling. They were activated at 9:07 a.m. on the Kospi and 9:12 a.m. on the Kosdaq — the first time both markets hit the brakes on the same day in about 11 weeks. If the Kospi closes lower, it will record its first seven-session losing streak since September 2024.
The three forces behind the rout
Three overlapping fears combined to drive Thursday's stampede out of risk assets — and all trace back to one question: how is the world's enormous bet on artificial intelligence going to be paid for?
Gartner warned that some 3.5 trillion dollars of AI infrastructure investment will be exposed to the risk of asset impairment by 2030, and that more than 80 per cent of so-called neocloud operators will fail to become self-sustaining businesses. The warning landed against a market already nervous about the debt-funded race to build data centres: CoreWeave, the AI cloud provider burdened with high-yield debt, plunged 15.46 per cent on Wall Street, with yields on its maturing bonds approaching 15 per cent. Goldman Sachs analysts likened the severity of the Kospi rout to the shocks of the pandemic era and the 2011 US credit-rating downgrade.
Wednesday's US inflation data came in hotter than expected: September CPI rose 3.7 per cent from a year earlier, above market forecasts of 3.6 per cent, while core inflation hit 2.6 per cent versus 2.5 per cent expected. The figures revived expectations of further Fed tightening. Higher rates are a double blow to the AI trade: they raise the cost of the debt financing the data-centre buildout, and they make lofty tech valuations harder to justify.
Third, supply threats. Chinese memory-chip maker CXMT has reported a major breakthrough in memory technology — a new chip structure with roughly 30 per cent smaller cell area, expected to reach production before the end of 2026. For Samsung and SK Hynix, the world's two largest memory-chip manufacturers, that raises the spectre of intensifying Chinese competition eroding the pricing power that has underpinned their AI-era profits.
The pain spreads across Asia — and beyond
South Korea suffered the steepest losses, but no major Asian market was spared. Japan's Nikkei 225 fell more than 4 per cent at one point during the session, SoftBank Group tumbled 7.9 per cent, Advantest dropped 6.9 per cent, Tokyo Electron lost 5.4 per cent, and Taiwan's Taiex fell 3 per cent.
The declines followed a bruising Wall Street session on Wednesday, when technology shares led broader market losses: the Nasdaq Composite dropped 1.88 per cent to 26,692.87, the S&P 500 lost 1.11 per cent, and the Philadelphia Semiconductor Index fell more than 4 per cent. Nvidia fell 3.16 per cent and Micron dropped 4.08 per cent.
The yardstick for judging the AI cycle has shifted: investors are no longer rewarding the scale of capital spending, but demanding evidence of cash generation and profitability. TSMC's earnings, due later in the session, are the turning point that will determine whether volatility settles or deepens, said Seo Sang-young, managing director at Mirae Asset Securities.
Bonds rally, gold jumps, iron ore breaks $90
The stampede out of equities triggered the classic safe-haven rotation. US Treasuries extended their rebound from Wednesday's post-inflation spike: the 10-year yield fell to 5.1267 per cent, a three-week low and some 21 basis points below the levels reached after the CPI data, while the 30-year sat at 5.4795 per cent. The bond rally dragged the dollar lower after it had touched an 18-month high overnight, and helped lift gold by around 40 dollars.
A strong dollar piles pressure on regional currencies and drains capital from emerging-market equities — the dynamic playing out in Seoul, where foreigners have now been net sellers of Korean shares for eight consecutive sessions. Currency swings of this sort are one reason investors keep an eye on live exchange-rate tools when Asian markets are under stress.
Meanwhile, the classic flight to safety was underscored by a milestone in commodities: iron ore traded below 90 dollars a tonne for the first time since 2024, according to Bloomberg, reflecting weakening Chinese steel demand and ample supply. Oil moved the other way: West Texas Intermediate traded at 95.10 dollars a barrel and Brent settled near 106 dollars after Houthi attacks on Saudi Aramco facilities — feeding the very inflation pressures spooking bond markets.
Why it matters
South Korea is one of the world's most concentrated AI plays: Samsung and SK Hynix sit at the centre of the global memory-chip supply chain feeding data-centre expansion. When those two names fall 9 and 11 per cent in a morning, the market's doubts about the AI investment boom have reached a new intensity.
For two years, the AI trade was about who could spend the most, the fastest. Gartner's 3.5-trillion-dollar impairment warning and CoreWeave's debt distress have yanked the spotlight onto a different question: how much of this infrastructure spending will ever earn its cost of capital? Debt-funded AI builders now face borrowing costs that refuse to fall, chip competition that threatens margins, and investors unwilling to pay up for promises.
For ordinary investors, the lesson is that valuations built on easy-money assumptions can unravel fast. Hot inflation, firm oil prices and hawkish central-bank talk have reawakened the negative stock-bond correlation — the Treasury rally and the gold price surge show bonds and bullion offering shelter again.
Background: from boom to doubt
The AI investment cycle has been the defining market story of the decade. Hyperscalers and start-ups have committed hundreds of billions of dollars to data centres, graphics processors and the memory chips that feed them — with Korean manufacturers among the biggest beneficiaries. SK Hynix's high-bandwidth memory is the industry standard for AI accelerators, while Samsung has ridden the same wave.
But the foundations have been creaking. China's CXMT has been closing the technology gap in memory chips, threatening Korean pricing power, while a string of warnings has chipped away at confidence that AI revenues can support the capital outlay. The September US inflation surprise was the match that lit a market already soaked in anxiety.
Keep the scale in perspective: even after Thursday's plunge, the Kospi remains far above where it traded earlier in the decade, and contrarians remain vocal. Dan Ives of Yorkville Ives told a Seoul press conference on October 14 that the index could recover to 9,000 points within six to twelve months, and the Nasdaq could reach 35,000 by 2029. Whether that call looks brave or foolish will depend on TSMC's earnings and the next US inflation print.
What happens next
Beyond that, US producer-price and retail-sales data due later Thursday will test the market's fragile rate expectations, while Federal Reserve officials' words will be parsed for any shift on further tightening. The deeper questions are structural: can debt-funded AI operators service their borrowings if rates stay elevated, will Chinese memory competition compress Korean margins, and when will foreign capital return to Seoul after eight straight sessions of net selling? The sidecars may have paused programmatic selling on Thursday morning — but they cannot manufacture buyers.
FAQs
Why did the Kospi fall nearly 8 per cent on October 15?
Three shocks converged: a Gartner warning that 3.5 trillion dollars of AI infrastructure faces impairment risk by 2030, hotter-than-expected US inflation data that revived fears of further Federal Reserve rate hikes, and a reported memory-chip breakthrough by China's CXMT that threatens Korean pricing power. Foreign investors sold a net 1.92 trillion won of shares by mid-morning, overwhelming domestic buyers and forcing the exchange to trigger sidecar trading curbs on both the Kospi and Kosdaq.
What are "AI-debt fears" and why do they matter for chip stocks?
The term describes investor anxiety about how the AI buildout is being financed. Data-centre construction is being funded with enormous amounts of debt, and rising rates make that debt harder to service — AI cloud firm CoreWeave, for instance, saw yields on its maturing bonds approach 15 per cent as its shares plunged. Chip stocks suffer because their AI-era valuations depend on capital spending continuing at a breakneck pace, which becomes doubtful if builders cannot afford to borrow.
How does hot US inflation hurt Korean shares?
Higher US inflation raises the odds of further Federal Reserve rate hikes, which strengthens the dollar and raises global borrowing costs. That combination is painful for Seoul on two fronts: foreign investors pull money out of Korean equities to chase safer dollar assets, and the AI-investment trade that dominates the Kospi becomes more expensive to finance. Wednesday's 3.7 per cent September CPI reading, above the 3.6 per cent forecast, was the trigger for this latest leg down.
Why are Treasuries, gold and iron ore all moving at once?
They are the two faces of the same trade. Falling Treasuries yields and a 40-dollar jump in gold reflect investors fleeing equities for safety, while the dollar's retreat from an 18-month high shows the post-CPI spike reversing. Iron ore breaking below 90 dollars a tonne for the first time since 2024 is a separate signal: weakening Chinese steel demand and oversupply, underlined by the World Steel Association cutting its 2026 demand forecast to a 0.1 per cent contraction.
What should investors watch next?
TSMC's earnings report, due later in Thursday's session, is the immediate catalyst — strong numbers could steady the Asian chip complex. After that, US producer-price and retail-sales data will test fragile rate expectations, while any further guidance from Federal Reserve officials on rate hikes will move markets. Longer term, the questions are structural: whether AI data-centre operators can service their debts, how Chinese memory competition develops, and when foreign capital returns to Seoul after eight straight sessions of net selling.
🤖 This article was rewritten by Feed and Figures' editorial AI from a report originally published by Bloomberg. Facts and quotes are preserved from the original; the rewrite focuses on clarity and structure. For the unedited original, see the source link below.
