Kospi 200 Plunges 8% as AI Sell-Off Deepens on Inflation Fears

By Grace Kim

South Korea's Kospi 200 fell more than 8% overnight to a six-month closing low, triggering circuit breakers that stopped trading at various points as an accelerating sell-off of AI-linked shares hit global markets.

The index, heavily skewed toward memory chip makers, took the hardest hit in a rout that spread across the tech sector on Wednesday. Samsung was among the chip makers and tech investors that plunged, alongside Japan's SoftBank.

The trigger: fears over rising inflation and future interest rate hikes, which spooked traders already wary of the heavily indebted AI sector.

What drove the sell-off?

Two forces collided. Fresh inflation numbers out of the US reignited worries that rate hikes could be back on the table. At the same time, investors have grown uneasy about the debt stacked up across AI-linked companies after years of aggressive capital spending.

Traders already wary of that leverage pulled the sell button first and asked questions later. Global investors fretting over potential interest rate hikes cut exposure across chip makers and tech investors such as Samsung and SoftBank.

The numbers tell the story plainly:

• Kospi 200: down more than 8% overnight, closing at a six-month low
• Circuit breakers activated, halting trading at various points during the session
• Samsung and SoftBank among the high-profile names that plunged

The circuit breakers matter. They don't fire for routine dips — they're designed for disorderly moves, and Seoul's market tripped them repeatedly in a single session.

Why are chip makers hit hardest?

The Kospi 200's heavy weighting toward memory chip makers makes it a proxy for the global AI trade. When sentiment on AI spending turns, Seoul feels it first and hardest.

That's exactly what happened overnight. The more than 8% drop wasn't spread evenly across the Korean market — it concentrated in the companies that make memory chips, the segment most exposed to the AI build-out and its financing assumptions.

SoftBank's slide fits the same pattern. The Japanese group is one of the largest tech investors in the world, and its share price moves with the fortunes of the AI-linked portfolio it backs.

What does the inflation data change?

September's inflation numbers from the US reset expectations. Rising inflation raises the odds of future interest rate hikes, and higher rates hit indebted companies twice: borrowing costs climb, and the valuations of their future earnings fall.

For a sector that borrowed heavily to fund AI expansion, that combination is toxic. Traders who had tolerated the leverage while rates were falling, or at least stable, repriced it quickly.

The sell-off's speed suggests positioning was crowded. Markets don't fall more than 8% in a session on a marginal change in expectations — they fall that far when a lot of money was leaning the same way and the exit narrows.

What comes next?

The immediate question is whether the inflation fears that drove this rout confirm or fade. Future interest rate decisions now carry direct consequences for the AI-linked names that dominate the Kospi 200 and portfolios like SoftBank's.

One session doesn't make a trend, but a six-month closing low with repeated circuit breakers is the market's bluntest signal that the debt behind the AI trade is now the thing investors are watching.

For Seoul's chip makers, the path from here depends less on demand for memory chips and more on what central banks do next.