2026-Q2 IMC-Chicago, LLC 13F Filing: Memory chip stock MU jumps to 0.14% of IMC-Chicago's book

IMC-Chicago, LLC's 2026-Q2 13F reads like the work of a trading firm mid-pivot: portfolio turnover accelerated sharply and the top of the book was rebuilt around memory and semiconductor names. The six steps below unpack what the document actually discloses, how to decode each action tag, and what this particular set of moves adds up to.

1. What a 13F actually discloses. A 13F is the quarterly holdings report institutional investment managers file with the SEC within 45 days of a quarter's end, listing long positions in U.S.-listed equities as of the quarter's final trading day. Its structural blind spots are three: it captures a single snapshot date (here, June 30, 2026), it excludes short positions and cash, and anything that happened between snapshots is invisible. Applied to this filing: IMC-Chicago, LLC reported 6,591 separate holdings for 2026-Q2, with a turnover ratio of 0.496467, up from 0.342614 the prior quarter — the firm traded a substantial share of its book during the three months.

2. New position or existing one: reading new_buy vs. add. Every line in the change list carries an action tag, and the tag — not the dollar column — defines what actually happened. A new_buy means the position did not exist at the prior quarter-end; an add means it did, and the share count rose. This filing contains exactly one new_buy: a line identified only by the CUSIP 84615Q903 (the nine-character security identifier used when no company name is attached in the dataset), opened at $900.0M and representing 0.22% of the portfolio. Every other top-line change sits on a pre-existing position. One more tag to know: unchanged means zero shares traded, so any dollar-value drift on such a line comes purely from the stock's price move during the quarter — not from any decision by the firm. None of this filing's top changes carry that tag; all 30 lines reflect active trading.

3. Reading the adds: a memory-and-chips buildout. Twenty-five of the 30 lines are adds, and they cluster tightly. One MU add line carried the stock from 0.09% to 0.14% of the portfolio, with a second MU add line right behind it; SNDK shows the same doubled pattern, one line moving from 0.03% to 0.02%. AMD's add line ran from 0.02% to 0.00%, flanked by INTC (to 0.04%), WDC (to 0.01%), the leveraged semiconductor ETF SOXL (to 0.01%), plus adds in TSM, AVGO, SMHC, GOOG, MCHX, AAPL and two MRVL lines. Whatever else this quarter held, the center of gravity of the buying was memory and semiconductors.

4. Why the same ticker appears twice — and weight vs. value. Raw 13F data frequently splits one economic position across multiple rows (separate accounts, share classes, or clearing lines): hence two MU rows, two SNDK rows, two TSLA rows, two MRVL rows, and both an add and a trim apiece for AMD and VOO. Net the lines before judging direction. Learn to read weight against value, too: TSLA's dollar value grew -$199.5M while its weight slipped from 0.19% to 0.08%, and NVDA's value rose +$1.84B even as its weight eased from 2.38% to 2.03%. Both moves happened because the rest of the portfolio grew faster than these stocks did — value measures the position itself, weight measures it against a rapidly expanding whole.

5. Trim vs. full exit — and the price-move trap. Nothing in this quarter's top changes carries a sold_out tag: the firm scaled several positions back but exited none of them completely. SPY is the clean case — a genuine trim, with value changing by a notable change and weight falling from 0.10% to 0.00%. The trim lines on AMD and VOO look self-contradictory until you apply the filing's own note: shares were trimmed (real selling), but the dollar value rose because the stock price gained more than the trimmed shares were worth — NOT a buy. A third trim line, left unlabeled by ticker in this dataset, shows the identical pattern. The rule: trust the action tag, never the dollar column alone.

6. What the pattern adds up to. Taken together, this was a deliberate rotation into information technology. The sector's weight finished at 0.586, up from 0.4237 a quarter earlier, while Consumer Discretionary fell to 0.1304 from 0.1854, Communication Services to 0.0895 from 0.1256, and Financials to 0.06 from 0.0844. The buildout came through breadth rather than a single mega-bet: holdings rose from 5,950 to 6,591 even as single-name concentration (HHI) dropped from 0.023212 to 0.018862, and the fund's momentum tilt stayed minimal at 0.018726 percentage points. On the funding side, the SPY trim stands out, alongside a split VOO picture — one add line, one trim line. In short: heavy trading, a hard tilt into chips and memory, and a broader base laid underneath the tilt.

This Quarter at a Glance