The much-discussed "AI stock guru" blow-up from late July has now been laid bare, with the key players—the hedge fund Situational Awareness (SA), Citadel Advisors which took over most of its portfolio, and Jane Street Capital which suffered heavy losses from its SA investment—all filing their 13F reports for the quarter ending June 30, 2026. Looking at these position snapshots from the end of the second quarter, we can clearly see the incredibly aggressive bets these top-tier whales placed on the AI computing infrastructure chain just before the dramatic storm hit.

Situational Awareness data reveals that fund's total second-quarter portfolio value stood at $20.2 billion, up from $13.7 billion in the prior quarter. During the second quarter, SA added 4 new stocks, increased positions in 12, reduced holdings in 5, and completely exited 20. Its top ten holdings made up a massive 91.77% of total portfolio value. Among its top five holdings, SanDisk Corp (SNDK.US) ranked first, with approximately 2.495 million shares valued at $5.67 billion, representing 28.52% of the portfolio, a 118.87% increase in share count from the previous quarter. Micron Technology (MU.US) came in second, holding roughly 4.829 million shares worth $5.57 billion, or 28.01% of the portfolio, a staggering 27,712.38% increase in share count from the prior quarter. Bloom Energy (BE.US) was third, with about 6.273 million shares valued at $1.90 billion, accounting for 9.54% of the portfolio, a slight 3.28% decrease in share count. Taiwan Semiconductor Manufacturing Co (TSM.US) ranked fourth, with roughly 2.649 million shares worth $1.27 billion, representing 6.36% of the portfolio, an 11,713.92% increase in share count. Nebius Group (NBIS.US) was the fifth-largest holding, with about 4.464 million shares valued at $1.23 billion, or 6.20% of the portfolio, and was a new position for the fund. The sixth through tenth largest holdings were CoreWeave (CRWV.US), Seagate Technology (STM.US), Applied Materials (APLD.US), Riot Platforms (RIOT.US), and SharonAI Holdings (SHAZ.US).

It is clear that SA's holdings through the second quarter were built almost entirely around the AI computing infrastructure chain. Besides Nebius, new positions for the fund in the second quarter included Seagate Technology, Vishay Intertechnology (VSH.US), and Cerebras Systems (CBRS.US). Notably, the fund completely sold out of Nvidia (NVDA.US), Intel (INTC.US), Corning (GLW.US), Advanced Micro Devices (AMD.US), and ASML (ASML.US) during the quarter, concentrating all its firepower into memory and computing infrastructure. Looking at the turnover, the fund's biggest additions in the second quarter were precisely Micron, SanDisk, and TSMC. In terms of portfolio weight changes, the top five buys were Micron Technology, SanDisk Corp, TSMC, Nebius, and Seagate Technology. The top five sells were the VanEck Semiconductor ETF (SMH.US), Nvidia put options (NVDA.US, PUT), Oracle put options (ORCL.US, PUT), Broadcom put options (AVGO.US, PUT), and AMD put options (AMD.US, PUT).

Citadel Advisors data shows its total second-quarter portfolio value was $880 billion, a sharp drop from $620 billion in the prior quarter. Citadel added 6,100 new stocks, increased holdings in 2,605, reduced positions in 4,815, and exited 1,887 during the quarter. Its top ten holdings comprised 22.67% of total portfolio value. Among its top five holdings, SPDR S&P 500 ETF call options (SPY.US, CALL) ranked first, with about 47.748 million contracts valued at $35.66 billion, or 4.07% of the portfolio, a 76.66% increase in contracts from the prior quarter. Invesco QQQ Trust put options (QQQ.US, PUT) were second, with about 36.06 million contracts worth $26.55 billion, or 3.03% of the portfolio, a 1.32% increase. Invesco QQQ Trust call options (QQQ.US, CALL) were third, with about 31.9 million contracts valued at $23.49 billion, or 2.68% of the portfolio, a 63.62% increase. SPDR S&P 500 ETF put options (SPY.US, PUT) were fourth, with about 31.155 million contracts worth $23.27 billion, or 2.66% of the portfolio, a 16.23% decrease. Micron Technology put options (MU.US, PUT) were fifth, with about 19.2754 million contracts valued at $22.25 billion, or 2.54% of the portfolio, a 15.31% increase. The sixth through tenth largest holdings were Micron Technology call options (MU.US, CALL), Tesla call options (TSLA.US, CALL), iShares Core S&P 500 ETF (IVV.US), Nvidia call options (NVDA.US, CALL), and SanDisk put options (SNDK.US, PUT).

Notably, SpaceX (SPCX.US), the commercial space giant that went public in June, also caught Citadel's attention. The fund not only established a new position in SpaceX but also bought call and put options on the stock. Additionally, Citadel also initiated a new position in Cerebras Systems during the second quarter. Its massive long-short options matrix, including put and call combinations on Micron and SanDisk, demonstrates its top-tier risk hedging capabilities. In terms of portfolio weight changes, the top five buys were Micron Technology put options, Micron Technology call options, SPDR S&P 500 ETF call options, SanDisk put options, and iShares Core S&P 500 ETF. The top five sells were SPDR S&P 500 ETF put options, SPDR Gold Trust call options (GLD.US, CALL), Tesla call options, SPDR Gold Trust put options (GLD.US, PUT), and Nvidia call options.

Jane Street Capital data shows its total second-quarter portfolio value was $1.21 trillion, up from $780 billion in the prior quarter. The firm added 2,581 new stocks, increased holdings in 4,999, reduced positions in 3,741, and exited 2,599 during the quarter. Its top ten positions accounted for 32.48% of total portfolio value. Among its top five holdings, SPDR S&P 500 ETF put options (SPY.US, PUT) were the largest, with about 150 million contracts valued at $116.1 billion, or 9.79% of the portfolio, a 37.20% increase in contracts. SPDR S&P 500 ETF call options (SPY.US, CALL) were second, with about 72.825 million contracts worth $54.38 billion, or 4.59% of the portfolio, a 9.77% increase. Micron Technology put options (MU.US, PUT) were third, with about 36.421 million contracts valued at $42.04 billion, or 3.55% of the portfolio, a 21.69% increase. Invesco QQQ Trust put options (QQQ.US, PUT) were fourth, with about 49.238 million contracts worth $36.26 billion, or 3.06% of the portfolio, a 20.93% increase. SPDR S&P 500 ETF (SPY.US) was fifth, with about 44.259 million shares valued at $33.05 billion, or 2.79% of the portfolio, a 118.13% increase in share count. The sixth through tenth largest holdings were Invesco QQQ Trust call options (QQQ.US, CALL), iShares Russell 2000 ETF put options (IWM.US, PUT), AMD put options (AMD.US, PUT), Nvidia call options (NVDA.US, CALL), and Micron Technology call options (MU.US, CALL).

In terms of portfolio weight changes, the top five buys were Micron Technology put options, SPDR S&P 500 ETF, Micron Technology call options, SanDisk put options (SNDK.US, PUT), and AMD put options. The top five sells were Tesla call options (TSLA.US, CALL), SPDR Gold Trust call options (GLD.US, CALL), SPDR Gold Trust put options (GLD.US, PUT), Tesla put options (TSLA.US, PUT), and Nvidia put options (NVDA.US, PUT).

Event Recap: Leveraging deep insights into the AI industry gained from his time on OpenAI's core research team, Leopold Aschenbrenner, once dubbed an "AI stock guru," founded the hedge fund SA in September 2024. The fund's core strategy was a high-conviction bet on the AI infrastructure sector, amplified by leverage of up to 4x, hedged by shorting traditional software stocks. This high-leverage bet on AI stocks generated staggering returns in just a few months. A letter to investors in early July disclosed that the fund's portfolio had returned 439% in the first half of 2026. Other reports indicated the fund's assets under management had swelled to $45 billion by early July.

However, as July began, the sustained rally in the AI sector underwent a sharp reversal. AI hardware and memory chip stocks experienced a deep collective correction, crushing the fund's highly concentrated portfolio. Data shows that SA's top holding, Micron Technology, fell 28.69% in July, while SanDisk plummeted 46.57%. Compounding the problem, the software short positions intended to hedge risk actually rose in value, creating losses on both sides of the long-short trade. The high leverage amplified the account drawdown, blowing through the fund's margin safety cushion. SA received a series of margin calls and was ultimately forced to sell most of its public market holdings at a discount to Ken Griffin's Citadel, averting a disorderly liquidation that could have impacted the broader market.

Dragged down by the massive decline in the value of its investment in SA, Jane Street Capital recorded a staggering loss of approximately $15 billion in July. This marked the first month since 2016 that the Wall Street firm, known for its strict risk management and quantitative trading, reported negative trading revenue, causing a major shock in global trading circles. According to an internal memo from Jane Street, the year-to-date gains from this investment were nearly wiped out by the SA fund's decline. Furthermore, other long equity positions in Asian non-AI stocks also suffered significant losses. The high-yield trades that had performed well in the earlier market environment collectively reversed as market conditions shifted, and the combined losses from multiple fronts resulted in the $15 billion monthly deficit. It is reported that this loss will be booked in Jane Street's third-quarter financial results. The firm has closed most of its exposure in the specific areas that caused the July loss and has reduced risk-taking in other strategies.

In contrast, giants like Citadel, which had already deployed a massive defense of put and call options by the end of the second quarter, were able to successfully execute a "second harvest" of these high-quality computing assets during the July bloodbath by buying the dip. This second-quarter 13F filing perfectly captures the "calm before the storm" on the eve of one of Wall Street's largest long-short squeezes in recent years.