Trading on South Korea's KOSPI was suspended early on Thursday after a heavy sell-off in local semiconductor stocks produced a rapid, steep drop at the market open. The index plunged more than 6% to 7,769.16 points shortly after trading began, prompting an automatic sell-side sidecar that halted transactions for five minutes.
Thursday's interruption follows a pattern of movement-based trading halts on the KOSPI this year amid heightened volatility driven largely by pronounced intraday swings in major chipmaking companies. Those swings have become a recurring source of market stoppages as regulators rely on circuit-breaker mechanisms to stem disorderly moves.
At the center of the latest rout were Samsung Electronics Co Ltd (KS:005930) and SK Hynix Inc (KS:000660). Both memory-chip producers had staged sharp rallies earlier in the year on what market participants described as outsized demand from artificial intelligence applications. Their ascents gave the two companies an outsized influence on KOSPI valuations and contributed to greater sensitivity of the index to news affecting the chip sector.
On Thursday, Samsung shares declined 7.3%, while SK Hynix fell nearly 9%. The losses followed a report that OpenAI had developed software optimizations able to halve inference requirements for AI models - a development that could cut the number of AI processors needed to run such models. That report directly fed concerns that demand for AI-specific chips could be lower than previously expected.
Additional reports amplified worries about chip demand. One indicated that Meta Platforms planned to sell excess cloud computing capacity, a move that could encourage greater extraction of performance from existing hardware instead of prompting purchases of newer, more costly chips. Separately, reports said Apple was negotiating to buy memory chips from Chinese suppliers that are on a blacklist, a step attributed to mounting cost pressures from high memory prices. Those reports, taken together, added pressure specifically on memory-chip manufacturers.
The cluster of negative developments weighed heavily on chip and AI-linked equities, which had been a principal driver of the KOSPI's strong advance earlier in the year. That rally, however, has lost momentum in recent weeks amid emerging doubts about the sustainability of further gains in AI and chip stocks.
Despite the volatility and the abrupt trading pause on Thursday, the KOSPI remained up markedly on the year, trading approximately 83% higher so far in 2026.
Market context
- The KOSPI experienced an early-morning drop exceeding 6%, falling to 7,769.16 points.
- A sell-side sidecar was triggered, pausing trading for five minutes.
- Large declines in Samsung and SK Hynix were the primary catalysts for the index move.