The AI-driven rally in South Korea has come up against some cold hard facts. You had the big chip names, Samsung Electronics and SK Hynix, fall as much as 14.5% on Thursday and pull the Kospi down 8.2%. Then on Friday you see a 5.8% recovery. It is a case of whiplash, and it shows how much the Seoul market is at the mercy of what the AI story of the day is.
Sentiment can turn in a matter of hours when you have worries about too much AI compute on the table and not much from the US side to back you up. If you are an investor who has been on the AI memory bandwagon, the word is: the momentum is there, but don’t be fooled, it is thin.
AI boom faces stress test in Seoul
Put aside this week’s drama and you still have the top-performing major market in the world for 2026, with 77% in the bank so far. Most of that is thanks to two companies. Put them together and Samsung and SK Hynix make up well over half of the Kospi.
They have put in some serious numbers. SK Hynix was up 223% at its peak, leaving Samsung in its wake with a 123% gain. When you add in leveraged products, you get a magnified effect on both the way up and the way back, so every AI tidbit becomes a market mover.
What sparked the selloff
Then came word that Meta might be offloading some computing power and traders were on edge. A fund manager saw it as a sign Meta may have overbuilt, which is not good news for the ones selling the shovels in this AI gold rush.
Things only got more tense after a night of heavy losses in US tech, with Micron and SanDisk both down double digits. The Korea Exchange had to put a 20-minute hold on trading once the circuit breakers tripped, which says it all about the volatility.
There was also some talk of Apple looking to source from a couple of Chinese chipmakers. That kind of noise is enough to put pressure on Korean suppliers while everyone is rethinking how long the AI demand will last.
A sharp rebound, but nerves remain
Friday was a different story. The Kospi put in a 5.8% move, with both of our chip leaders up over 8%. You could tell how skittish things are by the fact the exchange had to briefly stop program buying when futures ran hot.
Under the hood, it was a bit of a mix. The data shows foreign and retail money were net sellers in the benchmark, while local institutions were the ones putting in orders to get some skin in the game.
Earnings and partnerships in focus
Some of the mood was lifted by a report that Anthropic PBC is in discussions with Samsung to put together a bespoke AI chip. It is in the early going, but strategists like to think it is a plus for Samsung’s place in the supply chain.
All eyes are on Tuesday for Samsung’s preliminary figures. We are talking 85 trillion won in operating profit for the June quarter, 18 times what it was a year ago. But as one portfolio manager will tell you, the number is not the point; it is about seeing if the upcycle in memory is for real.
The AI supply chain reality
Orders for high-bandwidth memory have been flying, and the Koreans are right in the middle of it. That is what has made the run-up so strong, but as we have seen, it is also what makes you vulnerable when the mood changes.
What this means for investors
If you look at the last two days, you have the new rulebook: the AI story drives the price, then the fundamentals have to catch up. Here is where to be looking:
– See what Samsung has to say on the memory supply side
– Keep an eye on the US for any signs on AI capacity
– Follow the chatter on Apple and where they are sourcing from
– Don’t be surprised by some bumps in the road as the levered funds make their moves
SK Hynix had its worst day since 2008 on Thursday, which is a lesson in how quickly a crowded trade can go. The buyers were out in force on Friday, but they are waiting to be told where the next round of AI demand is coming from and when it will show up in the bottom line.
It is not like the underlying thesis is gone. These chipmakers are still the heart of the global AI effort. But with prices and positions where they are, you need to be shown that the orders can take the heat and that you can keep your margins.
For now, it comes down to three things: what the big platforms are doing with their compute, any new wins or deals, and where Samsung’s earnings are headed. Get those in line and the trade in Seoul can pick up again. Miss the mark and we could see more of what we had this week.
