Micron Technology has been among the biggest winners of the AI memory boom this year, with shares up 671% over the past year and trading near $960.
Valued at a market cap of roughly $1 trillion, Mircon (MU) stock is also down 21% from all-time highs.
New 13F data show that Citadel Advisors, the hedge fund run by billionaire Ken Griffin, has been quietly trimming a huge chunk of its Micron position even as the stock kept climbing.
According to 13F filings reviewed by me, Citadel cut its Micron stock holdings by 86.93%, dropping from roughly 4.6 million shares to 600,523 shares.
Citadel reduced its exposure to the chipmaker by four million shares over the last three months, even as the AI company continues to grow rapidly.
The Micron reduction was not an isolated move. The same filing shows Citadel also slashed its stake in Taiwan Semiconductor Manufacturing by 86.97%, cutting roughly 3.5 million shares.
STMicroelectronics saw a similar cut in exposure, with Citadel trimming that position by 44.25%, or just over three million shares.
Taken together, these three names represent a clear theme.
Citadel meaningfully pulled back its exposure to semiconductor and chip manufacturing stocks, even as demand for AI infrastructure and memory chips has been running hot.
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The filing does not explain why the fund made these moves, and hedge funds routinely adjust positions for reasons unrelated to a company's outlook, including portfolio rebalancing, risk management, or simply locking in gains after a huge run.
That said, the pattern is not limited to chips.
Citadel's filing shows sizable cuts across a wide range of sectors too, including General Electric (down 72.02%), Citigroup (down 62.90%), Merck (down 49.40%), Tesla (down 41.39%) and Meta Platforms (down 38.77%).
This broad-based trimming suggests Citadel may have been reducing overall risk across many positions rather than making a specific bearish call on Micron or the memory chip market. Still, the size of the Micron and TSM cuts stands out even against that backdrop.
Micron's business has been on a tear.
The company's fiscal third quarter 2026 revenue hit $41.5 billion, up 346% year over year, marking its fifth straight quarterly revenue record.
Gross margin rose to 85%, allowing the company to beat consensus earnings estimates for seven consecutive quarters.
Related: Micron CEO is doubling down on a cycle-free future
CEO Sanjay Mehrotra told investors on that call that DRAM and NAND industry demand continues to exceed industry supply significantly, and that Micron expects tight conditions to persist beyond calendar 2027.
"We are excited to announce that we have now signed 16 Strategic Customer Agreements, or SCAs, which we expect will fundamentally transform our business model. The memory industry has been structurally transformed by the proliferation of AI."
The company guided fiscal fourth quarter revenue to $50 billion, plus or minus $1 billion, and non-GAAP earnings per share to $31, plus or minus $1.
A big driver behind this demand surge is artificial intelligence.
Micron executive Sumit Sadana explained at the KeyBanc Technology Leadership Forum on Aug. 10, 2026, that AI system performance is now fundamentally tied to memory chip capacity and speed, not just processor power.
He also pointed to Micron's Strategic Customer Agreements, long-term supply contracts that now cover about a quarter of the company's projected revenue, as a major shift in how the memory business operates.
Not everyone is convinced the rally has room to run.
Michael Burry, the investor known for correctly predicting the 2008 housing crash, has been adding to his short position against Micron even as the stock price climbed toward $1,000.
Burry said his goal was to reduce gross exposure and free up cash while keeping his overall bearish stance intact, and he acknowledged the short position was roughly break-even but tipping toward a loss as the market rallied.
Burry explained that the memory chip industry has historically moved in sharp boom-and-bust cycles, and Micron's capital spending is ramping fast, with fourth-quarter capital expenditures guided near $10 billion.
Despite the rally in MU stock price, it trades at 9.5x forward earnings, which is reasonable. Yahoo Finance data suggests Micron has a beta of 2.2, meaning it is twice as volatile as the broader market in either direction.
Out of the 32 analysts covering Micron stock, 31 recommend "Buy", and one recommends "Hold". The average MU stock price target is $1,555, 63% above the current price.
For now, Citadel's filing shows the fund trimmed exposure broadly, and Micron and its chip peers took some of the largest cuts.
The filing doesn't say whether that reflects caution about the memory sector specifically or a broader move to reduce risk across the portfolio.
Either way, the timing puts Griffin's fund on the sidelines of a trade that Micron's own leadership insists still has years of growth ahead.
Related: Jim Cramer has strong message for Micron stock investors
This story was originally published by TheStreet on Sep 4, 2026, where it first appeared in the Investing section. Add TheStreet as a Preferred Source by clicking here.