South Korea's KOSPI triggered its first circuit breaker since July on Thursday, halting trading as the index crashed 7.6% to its lowest close in six months. Japan's Nikkei lost 4.9%. Around $1 trillion of market value has been wiped from global AI and semiconductor stocks this week alone. This didn't come out of the blue. Here's the five things behind the rout.
1. China's memory threat just got very real
Over the weekend, Chinese chipmaker CXMT claimed it would launch server DDR5 modules by end-2026, using a denser cell design that Samsung and SK Hynix still have on their roadmaps. The claim has not been independently verified, but the market took it seriously, and with good reason. CXMT's share of global DRAM revenue has roughly doubled in a year, hitting around 10% in the second quarter according to Counterpoint Research. Chinese rival YMTC now ranks third in NAND shipments, ahead of Kioxia and Micron.
SK Hynix fell 10% on Monday on the CXMT news alone, and the KOSPI dropped more than 5%. Samsung and SK Hynix dominate the DRAM market with combined share of around 64%, and their profits, running at 70-80% gross margins, depend entirely on supply discipline. If CXMT delivers, the premium pricing both companies have been enjoying disappears. By Thursday's close, SK Hynix had fallen a further 11%, Samsung was down close to 9.5% and Japanese rival Kioxia had shed 12%. Saxo's Charu Chanana called it "a clear trigger for the selloff in memory stocks."
2. US inflation came back to bite
Wednesday's CPI report set it off. September inflation came in at 3.7% year-on-year, up from 3.4% in August and above the 3.6% consensus. Core CPI also beat, at 2.6%. Gasoline rising 9.1%, kept high by the conflict in the Strait of Hormuz. The Fed had already raised rates 25 basis points in September to 4%. The print put an October hike squarely back in play, with futures briefly pricing roughly even odds of a move on 28 October. A small tweak to interest rates can have an outsized impacted on large, debt-laden and investment hungry tech firms; particularly chipmakers. Asia's AI-driven markets had run the furthest, so they had the furthest to fall. The Nasdaq dropped 1.9% in New York on Wednesday. The Philadelphia Semiconductor Index fell 4.3%, its sixth consecutive losing session. Asia opened into that.
3. The AI credit crunch is becoming a crisis
The inflation print also hit a sector already showing signs of financial stress. For months, investors have been funding the AI infrastructure build-out with cheap debt. That bet is now coming apart. CoreWeave's 2032 bonds are yielding close to 15%. Oracle's five-year credit default swap spread hit a record 288 basis points on Wednesday. The stock fell 8.8%. Gartner poured petrol on the fire by estimating that AI data centre operators will need to generate $8.5 trillion in cumulative revenue to justify announced capital spending and financing costs, against likely AI revenues of no more than $3.6 trillion. It warned that more than 80% of neoclouds will cease independent operations by 2030. Broadcom's chief executive had already called the boom a casino. OpenAI's annualised revenue has apparently come in well short of targets. The message landing in Asian trading on Thursday was blunt: the maths on AI infrastructure does not work at today's rates.
4. Korea had a structural problem
Foreign investors sold a net 3.6243 trillion won of KOSPI shares on Thursday, their eighth consecutive session of net selling. Retail and institutional buyers were not able to absorb it. A circuit breaker halted trading for 20 minutes. Cumulative foreign outflows year to date have passed 200 trillion won, with Samsung and SK Hynix accounting for roughly 173 trillion won of that between them. But why? Share buyback programmes at both companies have now ended, removing a floor that had supported prices during previous bouts of selling. The Financial Services Commission called an emergency meeting. The KOSPI has fallen around 20% in six trading sessions.
5. TSMC's record quarter fails to anchor sentiment
TSMC reported during the Asian session and the numbers were extraordinary. Third-quarter net profit rose 69% year-on-year, above forecasts, on revenue of $46.7 billion. None of it mattered. Chief executive C.C. Wei said the company was being "prudent" in planning for 2027 given macroeconomic uncertainty and rising component costs for price-sensitive markets. In a session already worried about the long-term returns on AI investment, caution from the most important supplier of AI chips was read as confirmation of the problem. TSMC fell 2% in Taipei. The Taiex dropped around 3%.
What happens when Wall Street opens
The pre-market picture is split. Nasdaq 100 futures are down around 1.2% to 1.3%. S&P 500 futures are off about 0.3%. Dow futures are slightly higher, up around 0.4%, as money rotates into value and defensives. In pre-market trading, SK Hynix's US-listed shares are down 6.5%, Micron is off 4%, CoreWeave is dropping a further 4.5% after Wednesday's 15.5% collapse, and TSMC's ADR is down 2.1%. Rocket Lab has fallen almost 10% after officially pushing its Neutron launch to 2027. Against that, pharma names are higher, with Johnson & Johnson, Eli Lilly and Merck all up in pre-market.
PPI is out at 8:30am New York time. Consensus is for around 0.5% to 0.6% month-on-month. A print above that after Wednesday's hot CPI would push rate hike odds higher and put further pressure on long-duration tech. An in-line or soft print could trigger a relief bounce in oversold semiconductors, since the Philadelphia Semiconductor Index is already in a bear market.
Earnings from Charles Schwab, PNC Financial, US Bancorp and Prologis are also due before the open and will set the tone for financials. Fed Chair Kevin Warsh speaks in Bangkok late tonight UK time, his last chance to signal policy before the pre-meeting blackout begins on Saturday.
Markets are pricing around a 27% to 29% probability of an October rate hike. What happens at 8:30am will either put that number up or take some heat off an ugly week.
