Kospi Rockets 17% and Triggers Trading Halt as SK Hynix, Samsung Surge Up to 30% After Microsoft's Blockbuster Quarter

From a 12.6% Crash to a 17% Surge in Two Trading Days

Since SK Hynix's record 17% single-day plunge on July 29 dragged the Kospi into its worst rout in years, South Korean chip stocks have done a full about-face. On July 31, the Kospi surged as much as 17% intraday, according to TradingKey, triggering the Korea Exchange's "sidecar" mechanism that suspends program trading for five minutes when swings get too violent.

SK Hynix jumped as much as 30% intraday before settling around a 24% gain to 1.64 million won (roughly $1,156), TradingKey reported. Samsung Electronics rose more than 23% at its peak. Seoul Economic Daily and Korean outlet MK.co.kr both put early-morning gains for the two companies at roughly 20%, citing Korea Exchange data showing Samsung trading near 250,000 won and SK Hynix above 1.6 million won shortly after the open.

The numbers differ slightly depending on the exact timestamp cited, unsurprising given how fast the stocks were moving, but the direction and scale are consistent across every source. This was one of the sharpest one-day reversals in Kospi history, arriving just days after the sharpest declines.

What Actually Changed: Microsoft and Amazon's Earnings

The rebound didn't come from anything happening inside Korea. It came from Wall Street.

Microsoft's stock jumped roughly 15.5% in its July 30 regular session after the company beat earnings expectations, with Azure cloud growth coming in faster than analysts had projected, according to CNBC. Critically, CNBC reported that Microsoft's capital spending stayed "in check" rather than spiraling, which mattered to investors spooked by the prior week's AI-valuation panic.

Andrew Jackson, head of equity strategy at Ortus Advisors, said the results "sparked a huge rebound for risk-on and AI," adding in a note that a "'spend at all costs' mentality has been punished by the market" — meaning Wall Street rewarded Microsoft specifically for showing spending discipline, not just growth.

Amazon jumped more than 9% in extended trading the same evening after posting second-quarter revenue that beat expectations, driven by continued cloud strength, CNBC reported.

That one-two punch sent the Philadelphia Semiconductor Index up 8.19% overnight, according to MK.co.kr, with U.S. chip names posting outsized gains: Micron up 18.36%, SanDisk up 25.99%, AMD up 13.00%, and Intel up 11.30%. SK Hynix's U.S.-listed ADR jumped over 17%, which MK.co.kr noted let it recover its original offering price.

The SK Hynix Chairman's Trade

One detail stands out beyond the index-level bounce. TradingKey reported that Chey Tae-won, chairman of SK Group, personally bought 3,620 shares of SK Hynix in the open market, regulatory filings show. TradingKey said this marks the first time he has directly held shares in the company under his own name, and that the market broadly read it as a signal of confidence from the top of the conglomerate.

This is a legitimate, disclosed insider transaction, not an allegation of wrongdoing. Insider buying by a chairman is a normal, filed event under Korean securities disclosure rules, and it's fair for markets to treat it as a bullish signal. It is not proof the rally is durable.

The Case for Skepticism

There's a reasonable argument that this bounce is a technical snapback from oversold conditions, not a fundamental reassessment. TradingKey's own reporting frames it that way, noting analysts view the move as "a technical correction from oversold conditions" after the Kospi had fallen a cumulative 17% over the three prior trading days on doubts about AI capital-expenditure returns at Meta, Google, and Amazon, compounded by forced liquidation of leveraged positions.

That's the same leveraged-ETF unwind Korean regulators publicly apologized for just two days earlier. A market that just got margin-called into a historic crash bouncing 17% in a single session is at least as consistent with short covering and deleveraged funds re-entering as it is with a genuine repricing of AI demand.

Kiwoom Securities analyst Han Ji-young pointed to exactly that mechanical driver, telling Seoul Economic Daily the Kospi's rebound was supported by "expectations for the resolution of deleveraging in semiconductors" alongside Amazon's earnings surprise and Kospi 200 night futures hitting their upper limit.

Goldman Sachs, per TradingKey, remains optimistic on DRAM and HBM pricing trends, and SK Hynix posted record second-quarter revenue in its latest results. That's a genuine fundamental tailwind, separate from the day's volatility.

What's Unresolved

Whether this holds depends on two things nobody can answer yet. Global tech giants' upcoming capital-expenditure guidance must keep validating AI infrastructure spending, and memory chip pricing momentum must continue. TradingKey's own analysis flags both as open questions rather than settled outcomes.

The Korea Exchange's decision to trigger its sidecar circuit breaker on the way up, the same tool used to slow crashes