KOSPI’s 5.5% plunge: Broadcom shock, record foreign selling, and Asia’s Monday open test

From Broadcom to Samsung: how a U.S. “miss” became a Seoul crisis

Broadcom reported solid fiscal second-quarter results for the February–April period, but its AI semiconductor revenue and forward outlook fell short of elevated expectations. Shares plunged 12.6% in New York on Thursday, wiping out roughly $285 billion in market capitalization — the fourth-largest one-day market-cap loss in U.S. corporate history, according to reporting by The Dong-A Ilbo. That is not a small-company stumble; it is a signal that the AI infrastructure trade, which had carried global equities for months, can reprice violently when guidance merely meets reality instead of beating whisper numbers.

The disappointment propagated instantly to memory chipmakers, which had been among the biggest beneficiaries of hyperscaler capex. Micron Technology fell 7.74% and SanDisk lost 3.92% in U.S. trading. In Seoul, Samsung Electronics dropped 6.40% and SK hynix plunged 9.92%. Investors were also unsettled by speculation that Nvidia’s next-generation Vera Rubin accelerator could require less high-bandwidth memory per rack than earlier buildout assumptions implied — a narrative that threatens the “more GPUs equals more HBM” math underpinning memory valuations. Our gaming memory shortage piece explained how NAND and DRAM fabs are already contested between AI data centers and consumer SSD demand; Friday’s tape suggests equity investors are now questioning whether the memory side of the AI supercycle peaks before the GPU side.

Selling was severe enough that the Korea Exchange activated a sell-side sidecar — a temporary halt on program sell orders — at 9:08 a.m. local time. It was the 10th such measure in 2026. The KOSDAQ, home to smaller tech names, fell 4.5% to 1,002.44 and briefly dipped below 1,000 intraday for the first time since March 4. Lee Hyo-seop, a senior research fellow at the Korea Capital Market Institute, told Dong-A that concerns the semiconductor industry could peak sooner than expected drove the sharp reaction — and that foreign selling fed back into currency weakness, which encouraged more foreign selling to avoid FX losses.

The foreign exodus: 70 trillion won in twenty sessions

Foreign portfolio flows are the marginal price-setter for Korean large caps in a way U.S. retail investors rarely appreciate. Since May 7, foreign investors have been net sellers of KOSPI shares for 20 consecutive trading sessions, unloading a combined 70.11 trillion won over that stretch, per exchange data cited by Korean media. May alone saw roughly 44.7 trillion won in foreign net selling on the main board — a monthly record, surpassing the prior peak set in March 2026.

The concentration is extreme. According to Seoul Economic Daily, foreign investors disposed of roughly 30 trillion won of Samsung Electronics and 27 trillion won of SK hynix over the May 7–June 5 window — nearly 57 trillion won from two stocks alone. Both names had more than doubled year-to-date on AI memory optimism (Samsung up roughly 164%, SK hynix up roughly 258% through late May), making them natural profit-taking targets when U.S. leadership wobbles.

Not all foreign capital left Korea’s equity market. Some rotated into robotics and smaller AI-adjacent names on the KOSDAQ, where foreigners posted record monthly net buying of about 2.8 trillion won. Doosan Robotics topped foreign purchase lists. But the inflows are tiny relative to the semiconductor outflows — a rotation in progress, not a completed leadership change. Institutions sold a net 939.9 billion won on Friday as well, leaving domestic retail investors as the only meaningful bid: individuals bought a net 4.22 trillion won on June 6 alone. That divergence — foreigners and institutions exiting, retail absorbing — is a classic late-cycle pattern that often precedes either a reflex bounce or a deeper correction once retail buying power exhausts.

Currency stress: when the won becomes part of the trade

Equity selling did not stay on the stock exchange. The Korean won closed the daytime session at 1,539.1 per dollar, weakening to as low as 1,549.1 intraday — its weakest level since March 10, 2009, during the global financial crisis aftermath. At currency counters in Incheon International Airport, travelers were quoted dollar rates above 1,600 won, per Dong-A. Woori Bank economist Park Hyeong-jung cited tight FX supply-demand, Middle East instability, and U.S. Federal Reserve uncertainty as factors likely to keep the dollar supported near term.

For foreign holders of Korean equities, a falling won converts stock losses into larger dollar losses — incentivizing faster exits that pressure both the index and the currency. It is a feedback loop U.S.-centric analysis often misses when it treats Friday’s chip rout as purely a Nasdaq story. Korean exporters benefit from a weaker won on translation, but memory giants trade as global AI proxies, not traditional exporters; their multiples expand and contract with the U.S. rate path and AI capex narrative more than with local GDP.

Daishin Securities strategist Lee Kyung-min warned that SpaceX’s scheduled IPO — pricing expected June 11, trading June 12 — could act as a “black hole” for global liquidity, intensifying short-term KOSPI volatility if capital outflows accelerate with a clear destination. That connects Seoul’s Friday pain to the same IPO absorption story driving Bitcoin ETF outflows and tech concentration warnings elsewhere in the SpaceX IPO paradox analysis on this site.

Three scenarios for Asia’s catalyst week

Scenario A — Stabilization bounce (30–40% probability): Monday’s Asian session opens weak but finds support as retail buying continues and short-covering follows an oversold KOSPI. WWDC delivers enough AI optimism (Gemini-powered Siri demos, on-device framing) to lift regional tech sentiment without requiring immediate Samsung earnings confirmation. The won stabilizes above 1,540. Memory stocks trade sideways while investors await U.S. May CPI on Tuesday and Oracle earnings on Wednesday for capex validation.

Scenario B — Correlated risk-off (40–50% probability): Asia extends Friday’s slide as Hang Seng and Nikkei futures indicated over the weekend. Foreign selling continues, sidecar triggers become routine, and the won tests 1,560. WWDC fails to reflate AI multiples; instead, markets focus on Fed hike pricing and SpaceX IPO cash drains. Samsung and SK hynix lead another leg down; KOSDAQ robotics names cannot offset index weight. Crypto and high-beta assets sell in sympathy as a global liquidity gauge.

Scenario C — Dispersion trade (15–20% probability): Indices fall but internals improve. Foreigners finish rotating from memory into KOSDAQ AI/robotics and power-infrastructure names; Samsung stabilizes on value bids while smaller caps outperform. Broadcom’s guide proves company-specific rather than sector-wide; Oracle’s June 10 report rekindles backlog enthusiasm with RPO additions and cloud growth at the high end of guidance. Korean equities decouple from U.S. semis by midweek as domestic policy responses (FX verbal intervention, pension flow rumors) emerge.

What to watch before U.S. markets reopen

• Monday June 8 cash open (KST): KOSPI gap, foreign flow print, and whether sidecar halts reappear in the first hour.
• Won fixings and USD/KRW: sustained trade above 1,550 increases forced-selling risk from hedged foreign funds.
• WWDC keynote (10:00 a.m. PT): AI narrative spillover to Asian tech ADRs and Samsung’s foundry/logic story even though memory is the immediate pressure point.
• June 10 May CPI (U.S.): hot print cements hike bets and hurts long-duration tech globally; soft print allows memory multiples to breathe.
• June 10 Oracle Q4: cloud and RPO commentary either validates or undermines the AI infrastructure demand thesis Broadcom challenged.
• SpaceX IPO calendar: subscription windows and pricing June 11–12 as a liquidity thermometer for all risk assets, Korea included.

Jensen Huang’s return to South Korea this week — reported by Korean media alongside the market rout — underscores how tightly Seoul’s flagship equities remain tethered to the U.S. AI supply chain. A speech reaffirming Vera Rubin demand could matter more for SK hynix than any domestic policy announcement. Until then, the KOSPI is pricing a question Wall Street asked on Friday in dollar terms and Seoul is answering in won: is the AI buildout accelerating, or is this the first inventory correction in a trade everyone crowded into at once?

Sources: The Dong-A Ilbo — KOSPI slides as Broadcom rattles AI bets (June 6, 2026); Seoul Economic Daily — foreign selling concentrated in Samsung and SK hynix; NewsWatch — KOSPI plunge and SpaceX liquidity risk; Peter Lewis Money Talk — Asia Monday open preview (June 7, 2026); The Observer — Nasdaq selloff and mega-IPO overhang (June 7, 2026).