The Silmari

A daily data newsletter on the Korean stock market — silmari, ‘a clue: the loose end that unravels the knot’

⑤ After-Hours 18:002026.08.12 Wed · No. 10Neutral — composite sentiment score 0.885; volatility component at the 95th percentile (expanding-window, 2026 regime); leverage ETF share of total turnover at 2.556%, within the week’s observed range of 2.27–2.89%.

⑤ After-Hours · published 18:00 KST · after the regular session · Note: flow figures are preliminary as published just after the close; the exchange’s confirmed figures appear in that day’s Final Edition (20:00 KST).

① Pre-Open07:30 ② Early Session10:00 ③ Midday12:00 ④ Closing16:00 ⑤ After-Hours18:00 ⑥ Final20:00

01 · VerdictRegular session confirmed 15:30 KST

verdict at evening

KOSPI Surges 3.68% on Semiconductor Rally; KOSDAQ Flat as Breadth Narrows

The KOSPI closed Wednesday, August 12 (2026) at 6,579.04, up 3.68%, powered by a broad semiconductor advance that put Samsung Electronics, SK hynix, and related chip-equipment names among the session’s heaviest-traded issues.The KOSDAQ added just 0.12% to close at 858.91, with breadth notably narrower than the headline gain — 886 advancers against 753 decliners — as foreign investors net sold ₩162.0bn on that market while retail buyers absorbed the supply.

Key points

01Foreign investors posted provisional net buyingNet PurchaseThe difference between a market participant’s total purchases and total sales in a given period; a positive figure means that investor group was a net acquirer of shares.Tracking which investor category is net buying or net sellingNet SaleThe mirror of net buying: total sales exceed total purchases, producing a negative flow figure for that investor group.Foreign net selling on KOSDAQ alongside foreign net buying on KOSPI — as seen today — is a common rotation signal that practitioners watch when assessing risk appetite. on a given day is a standard first step in reading Korean market flow data published by the KRX. of ₩2,835.6bn on the KOSPI today, the third consecutive session of net inflow from overseas accounts; on the KOSDAQ they net sold ₩162.0bn.

02Today’s KOSPI advance was concentrated in the top decile: the ten largest issues by turnover captured 66.3% of total trading value, up from 63.4% on Tuesday — a sign the rally was not broad-based.

03Three of Wednesday’s five morning calls missed: the KOSPI call of +0.5–+1.5% undershot a +3.68% actual; the Samsung Electronics call of +1–+2% undershot +6.68%; and the Jusung Engineering call of −2–+2% missed against an actual +7.14%.

04The pre-crash scoreCrash-Precursor ScoreA composite signal — scored daily from sub-indicators including the advance-decline ratio, short-selling acceleration, panic-selling speed, and sentiment extremes — designed to flag conditions historically associated with sharp market dislocations.A score of 2 (with only the ADR sub-signal active) indicates a low systemic warning load on today’s data, though the score is one input among several and does not constitute a forecast. stands at 2 out of a possible higher reading, with only the ADRAdvance-Decline RatioThe number of advancing issues divided by the number of declining issues in a given market on a given day.An ADR below 1.0 on a day when the headline index is strongly positive signals that gains are concentrated in a small number of large-cap names rather than spread across the market. sub-signal active; the sentiment gauge stage reads “Neutral” on a composite score of 0.885, with the volatility percentile at 95 — the highest among the available components today.

02 · NXTNextrade Alternative ExchangeKorea’s alternative trading venue, launched in 2026, that operates pre-market, main, and after-market sessions alongside the KRX main exchange.NXT after-hours prices can diverge from KRX closing prices; because the exchange is newer, its figures are published on a delay and require the caveat that they are not KRX main-session data.NXT intraday — 20-minute delay · as of 17:25 KST

Evening disclosures —Short sellingShort sellingSelling borrowed shares first, betting the price will fall.A rising balance means more money is betting on a decline.balance

A window on whether the regular session’s move carried into the evening alternative venue

NXT After-Hours Snapshot Shows Chip Names Extending: Samsung Electronics +7.52%, SK hynix +7.02% on the Alternative Exchange

As of the 17:25 KST snapshot (20-minute delayed; NXT alternative exchange only — not KRX main session figures; not yet confirmed for the day), NXT showed 248 advancing issues against 343 declining, with combined turnover of ₩163,869bn across 608 listed names.Samsung Electronics led activity at ₩43,355bn with a quoted gain of 7.52%, followed by SK hynix at ₩41,761bn and +7.02% — both running ahead of their KRX main-session closes, though these NXT figures are preliminary and the confirmed daily tally will appear in tonight’s final collection.

03 · Gap risksRisk → same condition in the past → outcome distribution

Tomorrow morninggap risks 4names

A window naming in advance what could shake tomorrow’s opening price

Overnight US Futures Mild Negative; Chip NXT Premium and Narrow Breadth Set Up Asymmetric Gap Scenarios for Thursday

ADR

Signal Score Total 2pts

signal 2 points

Short-interest surge

Signal Score Total 2pts

signal 0 points

Selling acceleration

Signal Score Total 2pts

signal 0 points

Sentiment 90+

Signal Score Total 2pts

signal 0 points

05 · Principleas of 17:53 KST on 2026-08-12

Evening Trading Principles

A window recording the trading principles to hold to on the evening of a crash day

Crash-Precursor Score at 2; Breadth Concentration and Volatility Percentile Warrant Position-Size Discipline Overnight

The pre-crash precursor score reads 2 (only the ADR sub-signal is active; short-surge, sell-acceleration, and sentiment-90+ signals are all at zero), suggesting the day carries a low systemic warning load — but the KOSPI’s intraday high-low range of 254.93 points (3.97%) and a volatility-component percentile of 95 indicate that individual position swings can be outsized even on benign-scoring days in the current regime.Top-ten turnover concentration at 66.3% on KOSPI means that the headline index gain masks divergent conditions across the broader list — on days when breadth narrows while the index advances, rotation rather than uniform continuation has been the more common next-session pattern in the 2026 regime.Overnight S&P 500 futures stood at 7,753.25 (−0.28% as of 05:00 KST on August 12) and Nasdaq-100 futures at 29,646.75 (−0.36%), providing a mild headwind signal for Thursday’s open that readers may wish to weigh alongside today’s domestic flows, which remain provisional until the evening confirmation cycle.