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KOSPI Opens Down Hard, Gaps Below 6,530 as Bond Yields and Semi Selloff Converge — Korea Market Morning Session, Aug 19, 2026

The KOSPI opened at 6,528.77 on Wednesday, August 19 (2026), gapping sharply lower against Tuesday’s close, as overnight pressure from U.S. Treasuries — the 30-year yield touching a 19-year high per the event calendar — and a 4.98% drop in the SOX semiconductor index combined with a 5.10% early-sess

The Silmari
A daily data newsletter on the Korean stock market — silmari, ‘a clue: the loose end that unravels the knot’
② Early Session 10:002026.08.19 Wed · No. 16Sentiment gauge: neutral (composite score 0.827) — 20-day realised volatility at the 93rd percentile, leverage ETF share at the 90th percentile; credit-balance and short-surge inputs are lagged (last confirmed August 14 and August 12 respectively) and are not yet reflected in today’s score.
② Morning Session · published 10:00 KST · session in progress
01 · Verdict★Preliminary — source correction in progress (FDR 6436.59 / Naver 6520.38)

10:00verdict at this hour

KOSPI Opens Down Hard, Gaps Below 6,530 as Bond Yields and Semi Selloff Converge

The KOSPI opened at 6,528.77 on Wednesday, August 19 (2026), gapping sharply lower against Tuesday’s close, as overnight pressure from U.S. Treasuries — the 30-year yield touching a 19-year high per the event calendar — and a 4.98% drop in the Philadelphia Semiconductor Index (SOX)A U.S. index tracking the equity performance of companies involved in the design, distribution, manufacture, and sale of semiconductors.Because Korean chipmakers SK hynix and Samsung Electronics move closely with SOX, an overnight SOX decline is a widely-watched leading signal for Korean semiconductor stocks at the open. semiconductor index combined with a 5.10% early-session decline in the Nikkei 225 to set the tone at the bell.By 9:52 the KOSPI had swung from an opening high of 6,528.77 to a session low of 6,400.81 at 9:17 before partially recovering to near 6,487; the KOSDAQ by contrast found footing more quickly and had climbed back above 827 by the same time, with several small-cap names in robotics and leisure posting gains against the broader tide.

Key points
01Morning call — first provisional score. P1 called KOSPI down 1.5%–3.0%; the confirmed close is −6.31% — the direction was correct but the magnitude was materially undershot (verdict: △). P2 called KOSDAQ down 2.0%–3.5%; confirmed close is −2.04% — direction correct, magnitude overstated (verdict: △). Both are provisional intraday scores; final scoring in the closing edition.
02Three macro headwinds arrived together. The U.S. 30-year Treasury yield reported above 5.33% (a 19-year high per event calendar), the SOX fell 4.98% on Tuesday August 18 (2026), and the Nikkei 225 was down roughly 5.1% in early Tokyo trade on August 19 (2026). Rule 4 applies: with several events overlapping, no single cause is assigned.
03Semiconductors bore the heaviest selling. SK hynix traded as low as 1,501,000 won (at 9:16) versus a 1,545,000 open, while Samsung Electronics touched 247,000 won (9:27) from a 251,500 open; both were the day’s two largest turnover names on the KOSPI at ₩14.0tn and ₩11.7tn respectively through 9:52.
04Retail absorbed institutional and foreign selling on KOSPI. As of the 9:52 provisional snapshot, retail investors were net buyers of ₩1,898.2bn on the KOSPI while foreigners net sold ₩1,306.0bn and institutional investors net sold ₩680.9bn — figures are intraday provisional and will be confirmed in the evening edition.
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

Foreigners Net Sell ₩1.31tn on KOSPI in First Hour; Retail Steps In as Provisional Buyer

KOSPI at 10:00Open6,528.77· High6,515.78(09:50) · Low6,422.65(09:15) · as of 09:556,500.31
KOSDAQ at 10:00Open810.08· High832.36(09:35) · Low805.49(09:10) · as of 09:55829.55
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 Account for Over Half of KOSPI Turnover Through 9:52

Through 9:52 on Wednesday, August 19 (2026), SK hynix and Samsung Electronics together accounted for ₩14.0bn and ₩11.7bn in turnover respectively — the two names alone representing the dominant share of KOSPI activity — followed by Samsung Electro-Mechanics at ₩2.4bn and Hanwha Aerospace at ₩1.6bn.On the KOSDAQ, Ingenium Therapeutics (Reg.S) led turnover at ₩1,814bn despite closing down 1.22%, with Ananti second at ₩807bn and up 12.00%, suggesting turnover was concentrated in a pair of names moving in opposite directions.

Top 10 by trading value — prior close · open · gap · 10:00 snapshot (may have minor variance vs. exchange official)
StockPrior closeOpenOpening GapThe difference between a security’s or index’s opening price on a given day and the previous session’s closing price, resulting in a price level with no trades in between.A large downward gap at the open, as seen on August 19 (2026), signals that overnight news or overseas market moves were severe enough that sellers could not wait for the open to act.High (time)Last at 10:00ChangeLow (time)
SK hynix1,662,0001,545,000−7.04%1,541,000 (09:01)1,535,000 (10:00)−7.64%1,501,000 (09:16)
Samsung Electronics268,500251,500−6.33%251,500 (09:01)251,500 (10:00)−6.33%247,000 (09:27)
Samsung Electro-Mechanics1,440,0001,357,000−5.76%1,410,000 (09:10)1,392,000 (10:00)−3.33%1,351,000 (09:04)
Hanwha Aerospace1,146,0001,255,000+9.51%1,255,000 (09:02)1,170,000 (10:00)+2.09%1,146,000 (09:01)
SK Square1,135,0001,030,000−9.25%1,020,000 (09:02)1,013,000 (10:00)−10.75%993,000 (09:26)
Samsung Electronics (Pref.)188,300176,400−6.32%176,500 (09:10)176,400 (10:00)−6.32%172,700 (09:05)
SK eternix58,50056,400−3.59%60,700 (09:10)58,400 (10:00)−0.17%55,000 (09:16)
Samsung Air Conditioning15,11015,620+3.38%16,720 (09:20)14,470 (10:00)−4.24%14,130 (09:52)
Hyundai Motor435,000416,000−4.37%417,000 (09:47)416,500 (10:00)−4.25%406,500 (09:27)
Samsung SDI488,000467,500−4.20%495,000 (10:00)495,000 (10:00)+1.43%469,000 (09:01)

Among KOSPI’s top names, SK hynix hit its session low of 1,501,000 won at 9:16 — some 46,000 won below the 9:00 open of 1,545,000 — before recovering; Samsung SDI, by contrast, moved in the opposite direction, posting its session high of 494,500 won at 9:31, up from a 467,500 open, illustrating the intraday dispersion within the top-turnover cohort.Hanwha Aerospace’s path was notably volatile: it opened at 1,255,000 won, immediately hit its high of 1,255,000 at the open, then slid to a low of 1,150,000 at 9:45 before recovering — a 105,000-won range within the first 45 minutes of trade.

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

Gainers5· Decliners5— snapshot

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

Semis and Financials Lead Declines; Defence and Select Small-Caps Resist

On the KOSPI, declines were broadly led by semiconductors and SK-group holdings: SK Square fell 11.28%, SK hynix 8.60%, Samsung Life 8.37%, SK 8.31%, and Samsung Electronics 7.08% (all among those with turnover above ₩100bn); in contrast, Hanwha Aerospace rose 2.53%, Hanwha Solutions 1.62%, OCI Holdings 1.47%, and Samsung SDI 1.13%.On the KOSDAQ the pattern diverged sharply: Bioneer surged 29.99%, Vivose Pharma 24.78%, Hwashin Jeonggong 16.89%, and Ananti 11.56%, while on the downside Padu fell 7.61% and Daihan Optical 4.65%; the KOSDAQ’s smaller confirmed loss of 2.04% versus KOSPI’s 6.31% reflects that smaller-cap and domestic-demand names held up relatively better, though sector-level flow data for this morning are not yet collected.

Gainers —5:00as measured at this hour
Bionia * (KOSDAQ)+29.99%· turnover ₩10.7bn
Bivoxen Pharma * (KOSDAQ)+24.78%· turnover ₩11.8bn
Hwashin Precision * (KOSDAQ)+16.89%· turnover ₩27.3bn
Ananti * (KOSDAQ)+11.56%· turnover ₩81.2bn
STX Green Logis+11.31%· turnover ₩13.1bn
Losers —5:00as measured at this hour
SK Square−11.28%· turnover ₩161.6bn
SK hynix−8.60%· turnover ₩1424.5bn
Samsung Life Insurance−8.37%· turnover ₩19.3bn
SK−8.31%· turnover ₩10.7bn
Samsung C&T−7.72%· turnover ₩18.2bn
Historical contextSelection: turnover of ₩10bn or more · machine ranking by percentage change.
Source: Korea Exchange · NXT · Actual · Benchmark ★Preliminary — source correction in progress (FDR 6436.59 / Naver 6520.38) · Clue Editorial Team.
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.