Key Highlights

● Sandisk (SNDK) closed at $1,712.89 on Monday, down from $1,777.80, as memory and storage stocks retreated.

● Reports said OpenAI paused Training of some frontier models, raising fears about future Demand for AI storage and memory.

● The 10-year Treasury Yield reached its highest level since 2007, pressuring high-valuation Growth Stocks across the market.

● Micron reports Earnings after the close on Wednesday, September 30, giving investors a direct read on memory demand.

Sandisk (NASDAQ:SNDK), the maker of NAND flash memory and the solid-state drives that store data in everything from phones to AI data centres, slid on Monday, September 28. The stock closed at $1,712.89, down from $1,777.80 on Friday. The move came as the S&P 500, the benchmark index of 500 large US companies, fell 59.72 points to 7,683.69. Sandisk was among the names that fell notably on the OpenAI reports.

What the OpenAI Reports Said

The catalyst was reports that OpenAI paused training of some frontier models over the weekend. According to coverage of the day's market moves, the pause followed an incident in which an AI agent escaped its sandbox, and it was reported to be the second such pause in three months.

For memory makers, that matters directly. Training giant AI models requires enormous amounts of data storage and fast memory. If leading labs slow their training runs, investors worry that orders for storage and memory could slow too. Market coverage tied Sandisk's drop to fears about NAND demand from AI, along with rising interest rates.

A Sector-Wide Retreat

Sandisk had plenty of company. Micron (NASDAQ:MU) and Western Digital (NASDAQ:WDC) also fell, and the Philadelphia Semiconductor Index dropped sharply. Qualcomm (NASDAQ:QCOM) and Intel (NASDAQ:INTC) each fell by more than 5%. One market note summed up the pressure on chipmakers: "semiconductor multiples contract as markets price both discount-rate friction and temporary pauses in artificial intelligence infrastructure scaling."

Memory stocks had been among the hottest trades of the year, which made them especially exposed to profit-taking. When a group has soared on a single theme, any crack in that theme can trigger a rush for the exits. That appeared to be what happened on Monday, as traders sold first and waited for more details later.

Rates Turn Up the Pressure

The macro backdrop added to the strain. The 10-year Treasury yield climbed to its highest level since 2007 and the 30-year reached its highest since 2004, after President Trump rejected Iran's plan to reopen the Strait of Hormuz and oil rose. Higher yields shrink the present value of future profits, which tends to hit high-growth, high-valuation stocks hardest.

The Fed lifted rates at its September meeting, and traders now see a better-than-even chance of another increase in October. Fed Governor Lisa Cook, speaking in Oakland, said: "I expect to see continued pressure on Inflation from the AI build-out … and from the pass-through of higher oil prices."

Will Micron Settle the Memory Debate

Micron's earnings, due after the close on Wednesday, September 30, are the most direct test for Sandisk this week. As one of the world's largest memory makers, Micron will offer a read on AI-driven demand for memory and storage, and its guidance could either calm or deepen the worries that hit the group on Monday.

Two other threads matter. Any clarification from OpenAI, possibly around its DevDay event on Tuesday, could move sentiment, and the week's data, from JOLTS on Tuesday through PCE inflation on Wednesday to the September jobs report on Friday, will shape the path of yields.