SK Hynix and Samsung shares jumped in Seoul yesterday after OpenAI released GPT-6 Astra on September 3, prompting expectations that the model’s memory-intensive architecture will tighten high-bandwidth memory (HBM) supply. SK Hynix is viewed as the most direct equity expression of the Astra demand thesis. Goldman Sachs and Morgan Stanley estimate that more than half of the $1.3 trillion to $1.5 trillion in AI capital expenditure planned for 2027 will go toward memory, supporting the case for a re-rating of both Korean chipmakers. OpenAI described GPT-6 Astra as its most capable and aligned model yet, citing advances in coding, cybersecurity and computer use, as well as the ability to learn unfamiliar software through trial and error. The model is rolling out to ChatGPT Plus, Pro, Business and Enterprise users and is available through the OpenAI API, Microsoft Azure and AWS Bedrock. A $41 billion combined buyback program from SK Hynix and Samsung, with about $27 billion still to be executed by November 21, added mechanical support. Foreign investors returned to net buying of Korean equities in the first week of September after combined foreign and institutional net sales exceeded 13.9 trillion won from the start of SK Hynix’s buyback on August 20 through late August. The shift came after SK Hynix remained roughly 48.6% below its 2026 peak and the Philadelphia Semiconductor Index’s forward price-to-earnings multiple fell below 19 times from about 29 times in June. The resulting valuation gap and fresh AI catalyst helped set the conditions for short covering, or investors buying back borrowed shares. The Nasdaq 100 and Kospi 200 have shown more than 91% price correlation over the past two years, linking a sustained return of foreign investors to Korean equities with renewed risk appetite in U.S. technology stocks. SK Hynix has emphasized buybacks, while Samsung relies more heavily on dividends. Samsung is forecast to distribute 80% of its remaining fourth-quarter return as dividends at 9,149 won per share. SK Hynix could announce an additional buyback of up to 40 trillion won ($28 billion) in the fourth quarter, although no exact announcement date has been confirmed.