What caused the dramatic rebound in Asian stock markets on Friday, July 31, with South Korea's Kospi surging over 14% and Japan's Nikkei 225 rising roughly 5%, and what were the key drivers including blockbuster US tech earnings from Microsoft and Amazon, the surge in AI chip sto

2. AI chip stocks led the charge, especially in South Korea. The Kospi closed up 17.91% — its largest single-day gain ever — to 6,595.45 points . SK Hynix soared 30%, its biggest daily rise since going public in the 1990s, while Samsung Electronics jumped 27% . The two stocks alone propelled the Korean market higher, with the Kospi's intraday surge triggering a sidecar (circuit breaker) mechanism . The rally followed an overnight surge in US semiconductor stocks and a rare share purchase by SK Group Chairman Chey Tae-won that helped restore confidence .

3. The Bank of Japan held rates steady at 1%, as widely expected. The BOJ kept its benchmark rate unchanged but delivered a hawkish signal, warning that core inflation was likely to exceed its 2% target from September . The decision removed one layer of uncertainty for Japanese equities.

4. Japanese authorities intervened to prop up the yen. Japan conducted a yen-buying, dollar-selling intervention in New York on Thursday night — its first such action in three months — after the yen slumped to four-decade lows . The dollar had been near 160.175, and the intervention sent the yen surging 2.4% in its biggest single-day jump, though it came under renewed pressure after the BOJ decision . The intervention helped stabilize currency markets, removing another headwind for Japanese stocks.

Cautious Analyst Outlook

Despite the magnitude of the rally, analysts warned that the underlying sentiment is still fragile . Key concerns include:

• Investor fears over heavy AI spending are "eased but not gone." Reuters described sentiment as "fragile" and noted that the rally came off a historic collapse — the Kospi had crashed more than 40% from its June peak of 9,385 .
• The Philadelphia Semiconductor Index, though up 8% on Friday, was still down 20% for the month .
• Long-end Treasury yields stayed elevated, and oil prices continued to rise (Brent crude on track for a 23% monthly gain due to Iran war-driven energy shocks) .
• The yen came under renewed pressure after the BOJ's rate hold, suggesting that currency volatility remains a live risk .

The consensus among analysts is that this was a powerful relief rally and a sharp mean-reversion bounce, but the fundamental debate over whether AI capital expenditure will deliver returns — and whether the AI-fueled volatility has truly run its course — remains unresolved .