Soroban Tripled to $14.3B in One Quarter and Built a $2.3B Utility Sleeve Nobody Saw Coming: Inside Mandelblatt's Tech-Utility Barbell

Eric Mandelblatt deployed $9.2 billion in a single quarter. Soroban Capital Partners’ Q4 2025 13F filing reveals a portfolio that tripled from $5.15 billion to $14.33 billion — a 178% increase that ranks among the largest single-quarter capital deployments by any Tiger Cub alumnus in the last decade. But the real story isn’t the volume of capital. It’s where it went: $5.5 billion into tech giants and $2.3 billion into nine regulated utilities, creating a barbell portfolio that most hedge fund allocators would consider contradictory.

TL;DR: Soroban’s Q4 2025 Filing at a Glance

• AUM: $14.33B (up from $5.15B in Q3 — +178% in one quarter)
• Holdings: 29 positions (doubled from 14 in Q3)
• #1 Position: Microsoft (MSFT) at $2.01B (14.0%) — entirely new
• #2 Position: Amazon (AMZN) at $1.96B (13.7%) — new, includes call options
• Utility Sleeve: 9 utilities totaling ~$2.3B (16% of portfolio) — all new or expanded
• Tech Exposure: 48% of portfolio, highest since 2018 per investor letter
• New Positions: 15+ including MSFT, AMZN, TDG, TSM, SO, AEP, EFX, UNP, SPGI
• Top-10 Concentration: 72.7% of assets in just 10 stocks
• Whale Score: 80/100 — among the highest-conviction hedge funds tracked

The $9.2 Billion Quarter: What Soroban Actually Bought

In Q3 2025, Soroban held just 14 positions worth $5.15 billion. The portfolio was dominated by Alphabet (GOOG) at 16.9% and Ferguson Enterprises (FERG) at 16.0%. By Q4, Mandelblatt had more than doubled the position count to 29 and injected approximately $9.2 billion in new capital — fundamentally rebuilding the fund.

The two largest new positions tell the story. Microsoft arrived as a $2.01 billion position (14.0% of the portfolio), reflecting conviction in Azure’s AI infrastructure buildout and enterprise software durability. Amazon came in at $1.96 billion (13.7%), structured with call options alongside common stock — a leveraged bet on AWS cloud growth and e-commerce margin expansion.

Below them, TransDigm (TDG) appeared as a brand-new $986 million position (6.9%). TransDigm’s aerospace aftermarket monopoly — selling proprietary replacement parts with 50%+ EBITDA margins — is the kind of “high barriers, low cyclicality” business that Soroban’s investor letter explicitly targets. Taiwan Semiconductor (TSM) was another new entry at $738 million, providing direct exposure to the AI semiconductor supply chain.

The Utility Sleeve Nobody Expected

The most distinctive feature of the Q4 portfolio is a $2.3 billion utility allocation spread across nine regulated electric utilities. This is unusual for a fund that just poured 48% of its capital into technology:

Utility	Value ($M)	Weight	Status
Southern Company (SO)	$578M	4.0%	NEW
Entergy (ETR)	$300M	2.1%	Held
American Electric Power (AEP)	$289M	2.0%	NEW
DTE Energy (DTE)	$283M	2.0%	Held
Pinnacle West (PNW)	$258M	1.8%	NEW
NiSource (NI)	$233M	1.6%	Increased
WEC Energy (WEC)	$159M	1.1%	Increased +234%
Ameren (AEE)	$130M	0.9%	Held
CMS Energy (CMS)	$78M	0.5%	Held

The thesis connecting these utilities to the tech positions is data center power demand. As AI workloads scale, hyperscalers like Microsoft and Amazon need reliable baseload electricity. Utilities with service territories near planned data center campuses — particularly Southern Company (Georgia), Entergy (Louisiana/Texas), and AEP (Ohio/Virginia) — are direct beneficiaries of AI infrastructure buildout without the technology valuation risk.

AUM History: The Comeback Arc

Soroban’s AUM trajectory reads like a redemption story. From a peak of $13.21 billion in Q4 2021, the fund contracted to just $6.76 billion by Q3 2023, cutting holdings from 118 to as few as 14. Mandelblatt used the drawdown period to radically concentrate, running the fund as a 14-to-17 position portfolio for nearly two years.

The April 2024 launch of Soroban’s Long Only Equity Master Fund marked the inflection point. That vehicle attracted capital based on an 18% gross excess return over the MSCI ACWI Index through mid-2025. The Q4 2025 filing likely captures the full deployment of this new capital pool, explaining both the AUM explosion and the shift from 14 to 29 holdings.

The Q3 2025 trough at $5.15 billion may reflect confidential treatment filings or timing — Soroban was likely accumulating positions before the full Q4 disclosure.

Portfolio Architecture: The Barbell Explained

Soroban’s Q4 portfolio is built on a deliberate contradiction — the fastest-growing companies in the world paired with the most predictable. The tech sleeve (MSFT, AMZN, GOOG, META, TSM) provides growth and AI exposure. The utility sleeve provides regulated cash flows, 3-4% dividend yields, and a structural tailwind from data center electricity demand. Between them, payment networks (Mastercard, Visa, S&P Global) act as the bridge — toll-road businesses with tech-like margins but utility-like stability.

This isn’t a defensive rotation. It’s a portfolio that profits whether AI scaling continues (tech + utilities benefit from power demand) or growth disappoints (utilities provide downside protection). The barbell structure suggests Mandelblatt is positioning for multiple scenarios simultaneously — a hallmark of the Tiger Cub playbook refined for the AI era.

What Changed from Q3 to Q4

The biggest shift is the demotion of Alphabet. GOOG was the #1 holding at 16.9% in Q3 — now it’s #5 at 6.1%, not because shares were sold but because new capital was deployed elsewhere. Ferguson followed a similar pattern: it was #2 at 16.0% and is now #9 at 4.7% after some trimming. The prior Q3 portfolio was a concentrated quality bet. The Q4 portfolio is a full-spectrum deployment.

The only meaningful exit was PPL Corporation, a small utility position. Everything else was additive — Soroban didn’t sell to buy; it raised new capital and put it to work.

Frequently Asked Questions

Why did Soroban’s AUM triple in one quarter?

The most likely explanation is capital inflows into Soroban’s Long Only Equity Master Fund, launched in April 2024. The fund’s strong performance (19.7% gross return in Q2 2025 alone) attracted significant institutional allocations that were deployed in Q4 2025.

Why is a tech-focused hedge fund buying utilities?

Soroban’s utility purchases are likely a data center power demand thesis. As hyperscalers build AI infrastructure, they need electricity from regulated utilities. Southern Company, Entergy, and AEP serve territories with significant data center development, making them indirect AI beneficiaries.

What does the Amazon call option position mean?

Soroban holds AMZN through both common stock and call options, indicating a leveraged bullish position. Call options amplify upside returns if Amazon’s stock price rises, suggesting Mandelblatt expects meaningful near-term appreciation from AWS growth or margin expansion.

How concentrated is Soroban compared to other hedge funds?

At 72.7% in the top 10 holdings across just 29 positions, Soroban remains highly concentrated. However, this is actually less concentrated than Q3 2025, when the top 5 alone represented over 66% of a 14-position portfolio. The fund is diversifying as it scales.

Is the Q3 to Q4 AUM swing normal?

A $5.15B to $14.33B swing in one quarter is exceptional. It likely reflects either confidential treatment of some Q3 positions (which would understate Q3 AUM) or a massive single-quarter capital raise and deployment. Either way, the disclosed Q4 portfolio represents Soroban’s current conviction set.