South Korea's KOSPI cratered ~10.8% to 6,023.66 on Tuesday — a drop violent enough to trip the exchange's circuit breaker and mark the index's worst single session since the U.S.–Iran flare-up in March.

This was a memory-chip earthquake, and two names did almost all the damage. Samsung Electronics fell 13.4% — its worst day in nearly two decades — and SK Hynix dropped 14.7%. Together those two are worth close to half of the entire KOSPI, so their collapse alone explains the bulk of the index's plunge; the rest of the tape was just along for the ride. It wasn't contained to Seoul either: Japan's Nikkei slid ~4.3% to a two-month low, with Kioxia down more than 18%, Tokyo Electron off ~11% and Advantest ~10%. Hong Kong's Hang Seng was the odd one out, edging up ~0.3%.

Two separate fears hit the same trade at once. One is China self-sufficiency: The Information reported that state-backed Shanghai Yuliangsheng has begun mass-producing China's first homegrown immersion DUV lithography machines — the exact tool ASML has monopolised for decades — with the first ~5 units due this year to SMIC, Hua Hong and CXMT. The other is AI-financing jitters: nerves about how the giant AI build-out actually gets paid for (right down to Nvidia's financing arrangements) have investors questioning the whole memory super-cycle bet.

The cleanest ripple isn't in Korea — it's ASML. Dutch lithography is the choke-point China just claimed to breach, and ASML fell ~6.6% on the news. China is roughly 20% of ASML's sales this year (down from 33% in 2025); a credible domestic DUV line puts that slice — and ASML's pricing power — squarely in the crosshairs.

Keep the catalyst in perspective, though: 5 machines in 2026 is a rounding error next to ASML's install base, and the Chinese tool is still viewed a generation behind on throughput and reliability. So the flip here is concrete — watch whether KOSPI holds the 6,000 line (a close below re-arms circuit-breaker risk), and whether Yuliangsheng actually ships those promised units. If those deliveries slip, the ASML-threat leg of this selloff unwinds fast.

As of 28 Jul 2026, ~2:30 pm IST (post Asia close). Sources: CNBC, US News / AP, Tom's Hardware. For discussion and education only — not investment advice. Verify before acting.