For fund managers in London, New York and Tokyo, a new ritual has emerged before trading gets underway: checking South Korean stocks.

Once a peripheral market for many global investors, Korea’s $4 trillion equity market is offering an early read on risk appetite as AI-driven swings in Samsung Electronics Co. and SK Hynix Inc. ripple through global chip stocks.

The shift is reshaping investment routines. JPMorgan Asset Management’s chief Asia market strategist gave a presentation on Korea to the firm’s global team for the first time in his 14 years on the job. Japanese traders are adding the Kospi Index to their watch lists. “We are all Korean investors now,” said Hani Redha, a London-based portfolio manager at PineBridge Investments.

But the market’s growing influence comes with a catch. The Kospi has become one of the world’s most volatile major benchmarks, with leveraged trading amplifying swings. SK Hynix’s recent US listing has extended Korea’s influence into Wall Street. The result is the country’s sentiment-driven trading increasingly setting the tone for global AI stocks around the clock.

Korea may see another turbulent session when markets reopen following a long weekend. Global chip peers were sold off on Friday as a surprise breakthrough from a Chinese AI startup renewed doubts over massive capex investment.