Seoul — October 01, 2026. Published after the market close; index and stock prices are official closing values, while the currency figure is an indicative market level rather than an official close.
The 30-second version
- KOSPI closed at 6,971.35, up 1.95% — its first gain in three to four sessions — after opening lower and sliding to the 6,780s in the morning.
- KOSDAQ surged 4.48% to 894.29, led by semiconductor materials, parts and equipment names.
- The trigger: Micron Technology’s overnight earnings beat plus news that 2026 HBM (high-bandwidth memory) supply is fully sold out, which flipped sentiment on Samsung Electronics and SK hynix mid-session.
- Domestic institutions were the buyers on KOSPI (net +KRW 305.6 billion, roughly $225 million) while foreigners and retail both sold. On KOSDAQ, institutions and foreigners bought together.
- The shadow over the party: the US 10-year Treasury yield touched the 5.3% range intraday, its highest since May 2002.
A morning selloff that one earnings report reversed
October’s first session started badly. KOSPI opened at 6,814.49, down 0.34%, and kept falling toward the 6,780 level. The pressure came from foreign investors dumping the big semiconductor names: intraday data showed roughly KRW 866.7 billion (about $640 million) of net foreign selling in Samsung Electronics and KRW 608.5 billion (about $450 million) in SK hynix — together accounting for about 72% of all foreign selling at that point in the morning. A spike in the US 10-year Treasury yield to the 5.3% range, a level not seen since May 2002, gave sellers an easy macro excuse.
Then the narrative flipped. Overnight, Micron Technology reported fiscal fourth-quarter revenue and EPS above consensus and guided next-quarter revenue to around $61.5 billion, well above the consensus in the $57 billion range. On top of that came news that the entire 2026 production volume of HBM — the high-bandwidth memory chips that feed AI accelerators, and a core product for both Samsung Electronics and SK hynix — is already sold out. For a market that had been fretting about a memory-cycle peak, this was the opposite signal: demand is spoken for a year out.
Samsung Electronics and SK hynix turned positive in the afternoon, KOSPI recovered the 6,900 line, and the index extended gains into the 6,971.35 close. Samsung Electronics preferred shares finished +4.76%, SK hynix +3.21%, Samsung Electro-Mechanics +3.17%, Samsung Electronics common +2.79%. On KOSDAQ, the buying spread down the supply chain into equipment and materials makers: Leeno Industrial jumped 10.90%, Wonik IPS 9.13%, HPSP 4.87%, Jusung Engineering 4.73%, and EO Technics gained more than 4%. Battery names EcoPro BM (+2.83%) and EcoPro (+2.28%) rode along. This is the classic “supercycle diffusion” pattern: good news for the memory giants lifts everyone who sells them tools and materials.
Who actually bought this rally
Korea publishes daily net flows by investor type — foreigners, domestic institutions, and retail individuals — and today’s breakdown is more interesting than the headline suggests. On KOSPI, institutions were the only net buyers at +KRW 305.6 billion (~$225 million). Foreigners finished the full session at net -KRW 597.2 billion (~$440 million) — notably smaller than the morning pace implied, suggesting the selling pressure eased after the Micron news. Retail investors sold a hefty KRW 1.234 trillion (~$910 million) net, which looks like profit-taking into strength. In other words, the KOSPI gain was built on institutional buying concentrated in a handful of large-cap chip names, not broad participation.
KOSDAQ was the cleaner story: institutions (+KRW 336.9 billion) and foreigners (+KRW 216.8 billion) bought together, against KRW 530.8 billion of retail selling — a two-engine rally, which helps explain the outsized 4.48% move.
Not everything went up. KB Financial fell 1.66%, the standout decliner among major large caps, and the early-session weakness in insurance (-1.33%), financials (-1.29%), chemicals (-1.08%), construction and telecom never fully healed — defensive and financial sectors were left behind even in the afternoon bounce.
The yield problem has not gone away
The uncomfortable backdrop remains: the US 10-year yield above 5.3% intraday (highest since May 2002) and the 30-year above 5.6%. Persistently high long-term rates compress the value of future earnings, which is a headwind for the growth-heavy Korean market. Today’s local read, per brokerage commentary, is that the market has entered a phase where “earnings power matters more than prolonged high rates” — hence talk of KOSPI retesting the 7,000 line. That is a sentiment call, not a guarantee, and the rate picture can reassert itself quickly. Foreign-flow volatility may also stay elevated around the Chuseok holiday period (Korea’s autumn harvest holiday), when trading desks thin out.
The won weakened alongside the rate move: USD/KRW traded around 1,360 on October 1 (a higher number means a weaker won).
Closing numbers
| Index / Rate | Close / Level | Change | % Change |
|---|---|---|---|
| KOSPI | 6,971.35 | +133.31 | +1.95% |
| KOSDAQ | 894.29 | +38.38 | +4.48% |
| USD/KRW (indicative, Oct 1) | around 1,360 | won weaker | won weaker |
What to watch next
- US September ISM Manufacturing PMI (Oct 1 US time) — a leading read on the industrial cycle that feeds directly into the rates debate.
- US September nonfarm payrolls (Oct 2) — the biggest single variable ahead of the October 27-28 FOMC meeting.
- Whether foreign selling in Samsung Electronics and SK hynix keeps fading now that the HBM sold-out news is on the table.
- Long-end Treasury yields — a 10-year holding above 5.3% keeps valuation pressure alive regardless of chip earnings.
- Breadth — financials and defensives lagged badly today; a durable push toward 7,000 would look healthier with wider participation.
FAQ
Why did the KOSPI rise on October 1, 2026?
Micron Technology’s overnight earnings beat — revenue and EPS above consensus, with next-quarter guidance of about $61.5 billion versus a $57 billion-range consensus — plus news that 2026 HBM supply is fully sold out reversed morning weakness in Samsung Electronics and SK hynix. KOSPI closed up 1.95% at 6,971.35 after trading as low as the 6,780s.
What is HBM and why does it matter for Korean stocks?
HBM (high-bandwidth memory) is the stacked memory used in AI accelerators. Samsung Electronics and SK hynix are key producers, so a report that all 2026 HBM volume is already sold out directly supports their earnings outlook — and, by extension, the KOSDAQ-listed equipment and materials firms that supply them.
Who was buying if both foreigners and retail investors sold?
On KOSPI, domestic institutions — net buyers of KRW 305.6 billion (~$225 million) — did the lifting, concentrated in large-cap semiconductors. On KOSDAQ, institutions and foreigners bought together, which is why that index rose more than twice as much in percentage terms.
Is the KOSPI going to 7,000?
Local brokerages are framing a retest of 7,000 as plausible if chip earnings momentum holds, but the index closed at 6,971.35 with US long-term yields at multi-decade highs — a genuine valuation headwind. This briefing reports the setup; it does not make buy or sell calls.
Disclaimer: This is an information and analysis publication, not investment advice. See our Methodology for data sources, standards, and our corrections policy.
Related reading
Also on Seoul Closing Bell
A companion piece on the same session, written from a different angle: Foreigners Sold Samsung and SK Hynix, the KOSPI Rallied Anyway.