South Korean chip stocks tumble 6%+ as Meta cloud capacity move raises oversupply fears

South Korean shares tumbled more than 6% on Thursday, weighed down by a global selloff in chipmakers as Meta Platforms' plan to sell computing power raised questions over excess AI infrastructure capacity. The benchmark KOSPI slid 519 points, or 6.25%, to 7,784.38, with heavy hitters Samsung Electronics falling 7.71% and SK Hynix losing 9.34%. The Korea Exchange briefly suspended program selling by triggering a circuit breaker sidecar.

The selloff follows weak overnight trading on Wall Street, where concerns over sustainability of AI spending and reports of Meta building a cloud business to sell excess capacity triggered broad semiconductor rotation. Reports that Apple is evaluating memory chips from Chinese suppliers also weighed on sentiment. SK Hynix and Samsung together make up roughly 40% of the KOSPI index, amplifying volatility; the index has surged nearly 70% in the second quarter on AI capex optimism, but single-stock leveraged ETFs tracking the memory giants concentrate exposure.

For architects: the move reflects growing skepticism about whether hyperscaler capex is as untethered as the market has priced in. Memory-heavy margin compression, commodity-pricing risk, and disciplined cloud-pricing dynamics are legitimate hedges for anyone modeling 2026–2027 semiconductor capacity demand.