South Korea’s benchmark KOSPI index fell as much as 9% intraday on June 8, triggering circuit breakers and halting trading. The culprits: Samsung Electronics and SK Hynix-the chipmakers that powered nearly all of the index’s gains this year.

Samsung dropped over 10%, while SK Hynix declined about 7-8%. The KOSPI closed down roughly 8.3%, wiping out weeks of gains in a single day.

A two-stock index meets gravity

Samsung and SK Hynix together accounted for up to 70% of the KOSPI’s gains during 2026. Both had touched market valuations near $1 trillion, fueled by insatiable demand for AI memory chips.

The sell-off began building on June 5, when the KOSPI closed at 8,160.59, already down 5.5% after falling as much as 6.9% intraday. Foreign investors net-sold shares worth about $2.5 billion that day alone.

By June 8, the intraday 9% drop activated the exchange’s circuit breaker mechanism-a forced pause designed to prevent panic selling.

What lit the fuse

Two catalysts converged to create the perfect sell-off conditions. First, US chipmaker Broadcom reported disappointing earnings, raising doubts about whether the AI spending cycle is decelerating. Second, unexpectedly strong US jobs data signaled the Federal Reserve may need to raise interest rates rather than cut them.

Foreign investors reversed course aggressively. The continuous outflows amplified volatility and turned what might have been an orderly correction into a dramatic rout.

What this means for investors

The sell-off raises broader concerns about AI valuations globally. Samsung and SK Hynix manufacture the memory chips powering every major AI system. If even these picks-and-shovels plays were overvalued, that has implications for every AI-adjacent asset, from Nvidia to AI-focused crypto tokens and decentralized computing projects.

If strong US economic data pushes the Fed toward a hawkish stance, the repricing won’t be limited to Korean chipmakers. Risk assets across the board, including Bitcoin and the broader crypto market, tend to struggle when rate hike expectations rise.