The AI Slowdown Trade of September 2026: Why Samsung and SK hynix Did Not Follow
American chip stocks fell about 5 per cent on 14 September after Anthropic’s chief executive called for a slowdown in model development, and the hyperscalers that buy the chips rose. Korea fell harder than the American chip index, then closed higher the next day while US chips kept falling. The reason being credited is long-term supply contracts, and those are the same figures Samsung gave on 30 July, not new ones. TrendForce’s own explanation of why high bandwidth memory contract prices have lagged spot contains the problem: the three large suppliers negotiate those contracts annually, which is the mechanism Micron used to describe its old agreements rather than its new take-or-pay ones. The defence that does hold is physical. By 2027 high bandwidth memory is estimated to take about 30 per cent of wafer input to deliver 13 per cent of bits, new capacity does not ramp until the second half of 2027, and Nvidia is already cutting the memory stack on Rubin Ultra because of what it expects to be unable to buy.