South Korea's KOSPI triggers circuit breakers for a second straight day as the AI semiconductor rally collapses 40% below June peak

Summary

South Korea's KOSPI and KOSDAQ both triggered market-wide circuit breakers on July 29, 2026, for the second consecutive session, a first in the exchange's history. The KOSPI fell 10.82% on the day and has now shed roughly 40% from its June 19 peak of 9,385, where it stood 116% year-to-date after a sustained rally driven by AI chip demand. Samsung Electronics lost the 200,000 won level, falling more than 5%; SK Hynix collapsed 15.81%. Three simultaneous shocks are cited: China's US$8.6B CXMT memory-chip IPO (a direct competitive threat), South Korea's own announcement of domestic DUV lithography production (undercutting the scarcity story), and Nvidia's US$250B OpenAI financing deal (signalling a shift away from Korean memory toward US compute infrastructure). The government called an emergency financial meeting. Margin calls accelerated the panic selling.

The split

South Korean domestic outlets (Seoul Economic Daily, Korea Economic Daily) focused on the structural reckoning in the AI-memory trade and the unprecedented circuit-breaker sequence. Al Jazeera placed it inside a broader narrative of the AI-driven boom fading. TradingKey's cross-market desk noted Japan's sympathy selling. Bloomberg (behind a paywall) reported that the record rout "failed to tempt global investors," suggesting foreign funds are not yet buying the dip.

By the numbers

• 10.82%, KOSPI single-day decline on July 29
• 40%, KOSPI fall from June 19 peak of 9,385
• 116%, KOSPI's year-to-date gain at the June peak
• 15.81%, SK Hynix decline on July 29
• US$8.6B, China's CXMT memory-chip IPO size (competitive shock)
• 6, people hospitalised in unrelated event (see Ukraine); 2, consecutive circuit-breaker days (first in South Korea's exchange history)

Why it matters

South Korea's semiconductor exporters, chiefly Samsung and SK Hynix, are the marginal suppliers of HBM and DRAM to the global AI build-out. A 40% KOSPI crash reflects a rapid repricing of the AI-memory thesis: cheaper Chinese supply, a domestic production boost, and a shift in Nvidia's financing priorities are hitting simultaneously. The spillover to Japan's chip stocks (Kioxia, SoftBank) shows the repricing is spreading.

What to watch

• Whether the South Korean government's emergency financial meeting produces direct market support measures
• SK Hynix's full Q2 earnings release and whether the consensus miss widens
• CXMT's IPO timeline and its first disclosed production volumes
• A third consecutive circuit-breaker session would signal full panic, not orderly correction