Seoul — August 10, 2026. Published after the market close; prices are official closing values.
The 30-second version
- KOSDAQ +6.97% to 854.47 — a move so fast it triggered a buy-side “sidecar” trading curb before 10am. Advancers outnumbered decliners roughly five to one.
- KOSPI +0.65% to 6,299.66, holding the 6,300 area after giving back part of a gap-up open.
- The story is rotation: money that crowded into Samsung Electronics and SK Hynix is spreading into biotech, construction and battery names.
- On the KOSDAQ, foreign and institutional investors bought together while retail took profits (11am preliminary flow data).
- The won closed marginally firmer at around 1,418 per dollar, even after weakening from the 1,410s intraday.
- Next tests: US CPI on Wednesday, PPI on Thursday.
A rally hot enough to trip the sidecar
The KOSDAQ opened 1.11% higher at 807.66 and simply accelerated. Around 9:50am, the surge in KOSDAQ 150 futures triggered a buy-side sidecar — a five-minute pause on program-trading orders that kicks in when futures move too far, too fast. Think of it as a speed bump, the milder cousin of a circuit breaker (which halts the entire market). Unusually, this one fired on the way up. The pause did little to cool enthusiasm: the index passed 846 (+5.92%) by 11am and closed at 854.47, up 6.97%.
The KOSPI had a quieter day. It gapped up 47.56 points (+0.76%) to open at 6,306.33, then faded to close at 6,299.66 (+0.65%). That gap between the two markets — 0.65% versus 6.97% — is itself the day’s headline: money is favoring smaller caps over the big index heavyweights.
Out of “Samjeonnix,” into everything else
Local traders use the portmanteau “Samjeonnix” for Samsung Electronics and SK Hynix, the two semiconductor giants that dominate the KOSPI. In a single-day rout on August 6 the pair fell roughly 6% and 10% respectively, and funds that had piled into single-stock leveraged products tied to them have been exiting — partly under pressure from deposit-related regulation — and rotating into other sectors.
Today the destination was pharma and biotech. Alteogen jumped 15.57% to 351,500 won, HLB rose 9.52%, and ABion closed limit-up at +29.98% (Korean stocks can move at most 30% in a session, and ABion ended the day at that ceiling).
Zooming out to the month — these are August-to-date figures, not today’s moves — the rotation trail is clear: the construction sector index is up 17.42% in August (GS Engineering & Construction +34.97%, Daewoo E&C +28.40%) on AI data-center, power-infrastructure and overseas plant hopes, while Samsung SDI has gained 15.62% and LG Energy Solution 9.76% on expectations of AI-driven energy-storage demand. As for the chip giants themselves, today’s session was muted: Samsung Electronics slipped fractionally and SK Hynix closed little changed — and the wide KOSPI-KOSDAQ performance gap is the clearest evidence that the rotation continued.
Who was buying — and who was cashing out
The flow figures below are 11am intraday preliminary numbers, so final settled data may differ; dollar conversions use a rate of around 1,418 won per dollar. On the KOSPI, foreigners net sold about 530.4 billion won (~$375 million), absorbed by institutions (+355 billion won, ~$250 million) and individuals (+153.5 billion won, ~$108 million). On the KOSDAQ the picture inverted: foreigners (+174.7 billion won, ~$123 million) and institutions (+283.9 billion won, ~$200 million) bought in tandem, while individuals net sold about 451.5 billion won (~$318 million) — read locally as profit-taking. Retail selling into a 7% rally is a mild caution flag worth remembering.
| Item | Close | Change |
|---|---|---|
| KOSPI | 6,299.66 | +0.65% |
| KOSDAQ | 854.47 | +6.97% |
| USD/KRW | ≈1,418 won | won slightly firmer |
| Alteogen | 351,500 won | +15.57% |
| ABion | 841 won | +29.98% (closed limit up) |
| HLB | 40,850 won | +9.52% |
The leverage overhang
Beneath the celebration sits a deleveraging story. Margin loans across the KOSPI and KOSDAQ combined fell from a record 38.63 trillion won (~$27 billion) on June 24 to 27.40 trillion won (~$19 billion) by August 4, as the semiconductor selloff forced positions to unwind. That cuts both ways: there is less borrowed fuel in the market now, but it also shows how quickly leveraged liquidations can amplify a downdraft. If the chip giants wobble again — the global backdrop includes soft earnings outlooks at AMD and SanDisk and Broadcom-fed skepticism about AI valuations — pressure on leveraged products could resurface.
What to watch next
- US July CPI on Wednesday, August 12, and PPI on Thursday, August 13, plus a heavy slate of AI-related earnings — see the week-ahead calendar.
- Whether Samsung Electronics and SK Hynix stabilize; a renewed slide could revive liquidation pressure in leveraged products.
- Final investor-flow data versus the 11am preliminary snapshot, and whether retail keeps trimming KOSDAQ positions.
- Whether the construction and battery rotation holds up if semiconductors recover and pull money back.
FAQ
Why did the KOSDAQ rise almost 7% on August 10, 2026?
A rotation of funds out of Samsung Electronics and SK Hynix — after their early-August slide — into biotech, construction and battery names, powered by simultaneous foreign and institutional buying on the KOSDAQ. Advancers outnumbered decliners roughly five to one.
What is a sidecar in the Korean stock market?
A temporary curb that pauses program-trading orders for about five minutes when index futures move sharply in one direction. It is a speed bump, not a full halt like a circuit breaker. On August 10 a buy-side sidecar fired on KOSDAQ 150 futures around 9:50am because the market was rising too fast.
Did Samsung Electronics and SK Hynix fall today?
Only slightly: Samsung Electronics ended fractionally lower and SK Hynix closed little changed on August 10 — a muted session for the pair after their sharp single-day slide of roughly 6% and 10% respectively on August 6. Today’s wide KOSPI-KOSDAQ performance gap suggests money kept flowing away from the pair.
What does “limit up” mean in Korea?
Korean stocks can rise or fall a maximum of 30% in one session. ABion’s +29.98% finish means it closed at that limit-up price. Reaching the ceiling does not lock a stock in place — shares can trade away from the limit intraday — but ABion ended the session at the maximum allowed gain.
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.