South Korea's stock market staged its sharpest reversal on record on Friday, as the Kospi index posted its best-ever day, according to reports. The rebound was driven by historic jumps in the country's chip and technology giants, which logged their biggest rally ever. The dramatic one-day surge capped a month of extreme volatility that had seen the index swing between meltdowns and gains. Analysts say the performance of South Korea's chip makers, key players in the global artificial-intelligence supply chain, could have wider implications for the AI trade. The sharp turnaround marks a notable shift from the turbulence that had unsettled investors in recent weeks.