Citadel Sold the $4 Billion Book It Took Over in Three Weeks

The Letter That Arrived on Friday

Ken Griffin wrote to Citadel investors on Friday, August 21: more than 80% of the aggregate risk in the portfolio acquired from Situational Awareness in late July had been unwound.

The method: roughly 100 block trades, more than $4 billion in market value, the year's largest single-session block sales in ten names, three weeks in all. Reuters put the count at "nearly 100" and CNBC at "more than 100"; both agree on the $4 billion.

"Our ability to distribute this risk was central to our investment thesis."

What Was Acquired

Situational Awareness, founded by Leopold Aschenbrenner in 2024, reported a net return of 439% for the first half of 2026, peaked at roughly $45 billion in assets in early July and ran leverage of as much as four times.

When AI hardware stocks sold off in the last week of July, margin calls followed and on July 30 the fund sold its entire listed equity book to Citadel in one transaction — a collapse we covered in a separate piece.

The 13F filed on August 14 showed what had changed hands: at June 30 the fund's disclosed long positions came to roughly $20 billion, two names more than 56% of the total.

A single $5.5 billion position in SanDisk or Micron sits far above those stocks' daily volume; a package that size cannot be handed to the market at the prevailing price.

The Economics of a Block Trade

The three-week schedule and the 100 blocks exist for this reason: pushing the same $4 billion into one session would have multiplied the impact. Breaking it up and spreading the work is the standard way to cut the cost of finding a bid. Griffin's line about the banks follows:

"A transaction of this magnitude could not have been completed without the extraordinary cooperation of the trading and prime brokerage teams at the banks serving both firms."

The ceiling on what can be sold in one session is set by daily volume: without enough buyers, price falls faster than the quantity sold implies. The year's largest block means going to that edge.

Doing it in ten names follows from how concentrated the book was. Working in small pieces would have turned three weeks into months with the price risk on the buyer: three weeks bought more impact for less holding time.

What Happened on Transfer Day

Removing a forced seller showed up on July 30: the transferred names rallied far above the indices.

The move was attributed not to company news but to the change of hands: once the known forced seller was gone, so was the pressure. The logic runs in reverse too — a buyer with inventory left leaves an overhang.

Who Sold Friday's Decline

Micron, SanDisk, Bloom Energy and Nebius all closed lower the Friday the letter was published. Linking the two is easy and wrong.

A letter is a disclosure, not a transaction; those sales had already been executed over three weeks. Citadel never disclosed which stocks it sold or when, so its role in the declines is unclear — and yields were rising that day, with the market waiting on Jackson Hole.

The distinction that matters for risk management: the day news is announced is not the day the event occurred. Prices move on the second, headlines print on the first.

The Two Sides of the Trade

The July outcome row needs care: how much of that 5.94% came from this trade was never broken out. The fund is up 12% for the year and managed roughly $71 billion on July 1, so no outsider can say what one transaction added.

There is also a side that does not show: the fund's first-quarter filing held billions in put positions, and how that leg was closed was never disclosed.

Unwinding 80% of a portfolio's risk is not selling 80% of its positions; hedges can stay on while the underlying stays on the books. Griffin's figure is 80% of aggregate risk, not of positions.

The Remaining 20%

The remaining risk sits on Citadel's books for one of two reasons: the least liquid positions were left for last, or the firm chose to keep that piece.

The first means distribution is still under way and those stocks have a seller in them yet; the second means Citadel is now an owner rather than an intermediary. From the outside they look identical and do not end the same way.

This piece draws on Reuters and CNBC reporting based on Griffin's investor letter, the 13F filed on August 14, and secondary accounts describing the structure of the block trades. Citadel's purchase price and the dates of its sales have not been made public; the percentages in the mechanism section are assumptions chosen to illustrate the arithmetic. The discrepancy between sources on the trade count is noted in the text.