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KOSPI Gaps Higher at Open, Semiconductors Lead Broad Reversal — Korea Market Morning Session, Aug 20, 2026

The KOSPI opened Thursday, August 20 (2026) at 6,672.39, gapping up sharply from Wednesday’s close, as SK hynix and Samsung Electronics surged in early trade on the back of overnight AI-chip deal headlines and a U.S. Treasury debt-buyback announcement that pulled the 10-year yield lower.By 09:52, th

The Silmari
A daily data newsletter on the Korean stock market — silmari, ‘a clue: the loose end that unravels the knot’
② Early Session 10:002026.08.20 Thu · No. 17Crash-precursor score: 3 of a possible maximum (ADR signal active; short-selling surge flag active; selling-acceleration and sentiment-90+ flags clear) — composite sentiment gauge for today is not yet available as the calculation requires end-of-day inputs.
② Morning Session · published 10:00 KST · session in progress
01 · VerdictRegular session confirmed 15:30 KST

10:00verdict at this hour

KOSPI Gaps Higher at Open, Semiconductors Lead Broad Reversal

The KOSPI opened Thursday, August 20 (2026) at 6,672.39, gapping up sharply from Wednesday’s close, as SK hynix and Samsung Electronics surged in early trade on the back of overnight AI-chip deal headlines and a U.S. Treasury debt-buyback announcement that pulled the 10-year yield lower.By 09:52, the index had climbed to 6,756.70 — though a confirmed closing figure is not yet available at this hour — while the KOSDAQ, after touching a session low of 835.33 at 09:25, stabilised near 840; both markets are trading with multiple cross-currents in play and no single cause can be assigned.

Key points
01Morning call scorecard (provisional): P1 called KOSPI lower (−0.5 to −2.5%); actual reading at this hour is sharply higher — ✗ miss. P2 called KOSDAQ higher (+0.5 to +2.0%); KOSDAQ is trading in the green — ✓ hit. Both verdicts are provisional; final scoring appears in the closing edition.
02Semiconductor surge leads: SK hynix opened at 1,613,000 won and reached 1,635,000 won by 09:08 before pulling back; Samsung Electronics opened at 257,000 won. The sector map shows semiconductors +2.97% as a group, with SK hynix and Samsung Electronics generating the two largest KOSPI turnover figures at ₩1.45tn and ₩1.08tn respectively through 09:52.
03Nikkei divergence: The Nikkei 225 was trading near 66,004 as of 09:30 JST, down −2.16% from Wednesday’s close, while Korean chip names are rallying — a divergence between the two markets that spans multiple concurrent drivers and should not be attributed to any single factor.
04Pre-market Nextrade (NXT)Korea’s alternative trading system, operating pre-market, main, and after-market sessions outside the KRX main board; prices and volumes are reported separately.NXT’s after-hours snapshot on Wednesday evening showed SK hynix down 3% and Samsung Electronics down over 4%, signals that contrasted with Thursday morning’s gap-up open. signal: Wednesday evening’s NXT snapshot (20-minute delayed, 19:25 KST reference) showed SK hynix at 1,612,000 won (−3.01%) and Samsung Electronics at 256,500 won (−4.47%); Thursday’s Opening GapThe difference between a security’s or index’s opening price on a given day and the prior day’s closing price, creating a visible discontinuity on a price chart.Thursday’s KOSPI opened at 6,672.39 — sharply above Wednesday’s implied prior close — making the gap the defining feature of this morning’s price action.-up open reversed that entire pre-market decline, illustrating the gap-risk inherent in overnight positioning.
02 · SnapshotUntil 10:00 AM · Korea Investment & Securities 5-min index (highs/lows based on 5-min close)(may differ slightly from exchange official figures)

10:00Snapshot

A window that records the market at that hour, like a photograph

Overseas Backdrop: U.S. Treasuries Stabilise on Buyback Move; Philadelphia Semiconductor Index (SOX)A U.S. equity index tracking roughly 30 major semiconductor design and manufacturing companies, widely used as a real-time barometer for global chip-sector sentiment.Korean chip heavyweights such as SK hynix and Samsung Electronics tend to correlate with overnight SOX moves; a SOX drop on Wednesday night was cited in the morning KOSPI directional call. Slips as AI-Chip Deals Lift Individual Names

KOSPI at 10:00Open6,680.34· High6,797.45(09:55) · Low6,622.02(09:05) · as of 09:556,797.45
KOSDAQ at 10:00Open843.99· High850.77(09:00) · Low835.77(09:15) · as of 09:55841.07
03 · Top 10 checkpointsKorea Investment & Securities minute bars · Until 10:00 AM

Top by trading value10— snapshot

A window on how the top trading-value names have moved up to this hour

SK hynix and Samsung Electronics Together Account for ₩2.53tn of KOSPI Turnover in First Hour

Through 09:52 on the KOSPI, SK hynix leads all names with ₩1,453.1bn in turnover, having touched a session low of 1,576,000 won at 09:08 before recovering; Samsung Electronics follows with ₩1,083.8bn, its intraday low of 252,500 won also printed at 09:07.On the KOSDAQ, Alteogen heads the board at ₩137.9bn, while Kolon TissueGene generated ₩73.5bn on heavy selling — the two stocks pulling the biotech sector in opposite directions within the first hour of trade.

Top 10 by trading value — prior close · open · gap · 10:00 snapshot (may have minor variance vs. exchange official)
StockPrior closeOpenGapHigh (time)Last at 10:00ChangeLow (time)
SK hynix1,500,0001,613,000+7.53%1,663,000 (10:00)1,662,000 (10:00)+10.80%1,576,000 (09:08)
Samsung Electronics247,500257,000+3.84%264,000 (09:43)263,500 (10:00)+6.46%252,500 (09:07)
Samsung Electro-Mechanics1,387,0001,401,000+1.01%1,413,000 (09:50)1,408,000 (10:00)+1.51%1,335,000 (09:03)
SK Square1,004,0001,082,000+7.77%1,090,000 (09:54)1,086,000 (10:00)+8.17%1,029,000 (09:07)
Samsung Electronics (Pref.)173,700180,000+3.63%186,500 (10:00)186,500 (10:00)+7.37%176,700 (09:08)
Pamicell11,38014,770+29.79%14,790 (09:02)12,110 (10:00)+6.41%11,380 (09:01)
SK eternix57,80058,800+1.73%63,700 (09:43)62,000 (10:00)+7.27%56,900 (09:01)
Samsung SDI487,000493,000+1.23%514,000 (09:17)508,000 (10:00)+4.31%493,500 (09:02)
Hanwha Aerospace1,177,0001,190,000+1.10%1,190,000 (09:01)1,158,000 (10:00)−1.61%1,144,000 (09:09)
NAVER208,000210,500+1.20%221,000 (09:33)219,000 (10:00)209,500 (09:02)

Samsung Electro-Mechanics printed its session high of 1,413,000 won as early as 09:50 and its low of 1,335,000 won at 09:03, a ₩78,000-won intraday range despite a modest net change; Hanwha Aerospace opened at 1,187,000 won but touched its high of 1,203,000 at the 09:00 open before sliding to a low of 1,144,000 at 09:09, moving counter to the broader chip-led advance.

04 · Up · DownReason labels: [News] confirmed · [Pattern] inferred

Gainers5· Decliners5— snapshot

A window on the biggest gainers and decliners, and the reasons behind them

Chips and AI Software Gain; Biotech Split as Kolon TissueGene Drops More Than 20%

On the KOSPI through 09:52, advancers include SK hynix (+7.93%), Samsung Electronics (+4.65%), NAVER (+5.29%), Samsung Electronics preferred (+5.24%), and SK Square (+4.83%), while KB Financial (−2.70%), Shinhan Financial (−1.62%), and LS (−3.45%) are among the laggards, underscoring a rotation out of financials and power-grid names into tech.On the KOSDAQ, Alteogen is up +7.41% and ST Pharm +6.45%, but Kolon TissueGene has fallen −19.88% and HLB −7.48%, keeping the biotech sector map at −2.49% as a group — a wide internal dispersion that makes a sector-level read difficult at this hour.

Gainers —5:00as measured at this hour
SK Securities+29.79%· turnover ₩24.9bn
IT Cent Global * (KOSDAQ)+24.85%· turnover ₩18.3bn
Danal * (KOSDAQ)+18.84%· turnover ₩39.8bn
Hectofinancial * (KOSDAQ)+16.98%· turnover ₩18.1bn
Good People * (KOSDAQ)+14.90%· turnover ₩12.2bn
Losers —5:00as measured at this hour
Kolon TissueGene (KOSDAQ)−20.46%· turnover ₩75.1bn
Hwashin Precision * (KOSDAQ)−12.83%· turnover ₩23.4bn
HLB * (KOSDAQ)−7.13%· turnover ₩28.2bn
LS−3.45%· turnover ₩10.0bn
Woori Financial Group−3.13%· turnover ₩11.9bn
Historical contextSelection: turnover of ₩10bn or more · machine ranking by percentage change.
Sources: Korea Exchange · NXT · own measurements · regular session confirmed 15:30 KST · The Silmari editorial desk.
This edition organises and explains publicly available market data. It is not investment advice. Predictions and their scores are preserved without revision — the judgement is yours.