Bristlemoon's fund fell 8.4% in the quarter even with ASML, Sandisk and Lam Research contributing
Bristlemoon Global Fund lost 8.4% in the September 2026 quarter, net of fees, though ASML, Sandisk and Lam Research helped in September. Its manager blames a narrow market, with the S&P 500 2% off its high and 83% of members more than 10% off theirs.
The Investor · Invest desk
Three figures for the end of September 2026: the S&P 500 was 2% below its 52-week high, 83% of its members were more than 10% below their 52-week highs, and 42% were more than 20% below theirs.
| Figure | Value | Note | Claim |
|---|---|---|---|
| S&P 500 below its 52-week high, end of September 2026 | 2% | 9 | |
| S&P 500 members more than 10% below 52-week high | 83% of members | at the end of September 2026 | 10 |
| S&P 500 members more than 20% below 52-week high | 42% of members | at the end of September 2026 | 11 |
What happened
- PAR Technology, Hemnet Group and Baltic Classifieds Group were the notable detractors over the same September period.
- Nine of the S&P 500's 11 sectors declined in September, according to the fund's letter.
- The fund's net exposure has drifted lower because it found more shorts in stocks that have not priced in rising yields and inflation from the Iran war.
- The letter does not recap the fund's theses and offers investors meetings or calls to discuss them.
Why it matters
- contradiction Owning some of the winners did not save the month: the letter says the fund was historically underexposed to the semiconductor and AI infrastructure names behind nine of the ten top contributors, so everything else outweighed the three it held.
- exposure Most index members are in a drawdown the headline hides, and 41% of them (83% more than 10% down, less 42% more than 20% down) sit in the 10% to 20% band.
- cost Investors who stay need a gain of about 9.2% to recover the quarter's 8.4% loss, before any fees on the way back.
The loss is back-loaded. The fund returned -5.9% net of fees in September [2] against -8.4% for the quarter [1], and compounding the two back out leaves about -2.7% for July and August together [14]. Most of the letter's market evidence is measured over the year to 30 September, a longer window than the quarter [6].
The concentration argument is the letter's strongest, and its figures hold together. The ten largest stocks were 39% of the S&P 500 at 30 September [5], so the 70% of the year's return that came from the top ten contributors [6] is about 1.8 times their weight [15]. Treat 1.8 as an indication. One figure is a year-end weight, the other a full-year contribution, and the letter does not say the two groups are the same ten names.
The explanation for the fund's own holdings carries a hedge. The letter says the managers "strongly believe that these steep price declines are unwarranted and partly reflect broader market rotations" [20]. "Partly" leaves a share of the decline to causes inside the companies.
The managers say the holdings are worth more than the market is paying for them. The letter says they "remain very confident in their prospects and compelling value" [19]. The market's verdict on those holdings was down 8.4% in a quarter. The text available to us does not say how large the company-specific share of the decline is, why the three September detractors fell, or what the fund's one-year return, the quarter's benchmark return or any position size was. The letter contains context on the market, a section on AI and investing, and write-ups on four shorts, Campbell's, REA Group, Masterbrand and Polaris [12], with no long-side write-up listed.
We think the letter's diagnosis of the index holds on its own numbers and its diagnosis of the fund is unproven. Three outcomes would separate them. If breadth returns and the three September detractors recover, rotation was the cause and the value claim stands. If the AI leaders keep going while the fund's longs keep falling, "partly" was the operative word and the theses are what failed. If yields and inflation from the Iran war [18] reach the stocks the fund is short before they reach its longs, the short book carries the next quarter under either of the first two.
What to watch
- The fund's next quarterly letter: whether its September detractors (PAR Technology, Hemnet, Baltic Classifieds) appear among contributors or the AI leaders keep supplying the winners.
- Breadth in the S&P 500: whether the 83% of members more than 10% below their highs narrows while the index stays within 2% of its own.
- Whether rising yields and Iran-war inflation reach the four shorts (Campbell's, REA Group, Masterbrand, Polaris) before they reach the fund's longs.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence50
- Adoption
- Insufficient
- Hype gap+20
- Incentives75
- Confidence55
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
The Bristlemoon Global Fund returned -8.4 percent for the September 2026 quarter, net of fees.
- [2]
The fund returned -5.9 percent for the month of September 2026, net of fees.
- [3]
Key performance contributors in the month of September included ASML, Sandisk and Lam Research.
- [4]
Notable performance detractors over the same period included PAR Technology Corporation, Hemnet Group and Baltic Classifieds Group.
- [5]
The top 10 largest stocks combined comprised 39% of the S&P 500 index as of September 30, 2026.
- [6]
The top 10 contributors to S&P 500 index returns for the year to September 30, 2026 accounted for 70% of those index returns.
- [7]
Nine of the top 10 contributors to S&P 500 returns are semiconductor and AI infrastructure names, sectors the fund has historically been underexposed to.
- [8]
Nine of the S&P 500's 11 sectors declined in the month of September.
- [9]
At the end of September 2026 the S&P 500 was 2% below its 52-week high.
- [10]
At the end of September 2026, 83% of S&P 500 constituents were more than 10% below their 52-week highs.
- [11]
At the end of September 2026, 42% of S&P 500 constituents were down by more than 20% from their 52-week highs.
- [12]
The letter provides context on why the market has been hard to navigate, discusses the implications of AI on the investment industry, and gives write-ups on four shorts: The Campbell's Company, REA Group, Masterbrand and Polaris.
- [13]
Rather than recapping its investment theses in the letter, the fund says it will make itself available for meetings or calls with investors to discuss them.
- [14]
Compounded return for July and August combined is about -2.7%.
- [15]
The top 10 contributors' 70% share of index returns is about 1.8 times the 39% weight of the ten largest stocks (the two groups may not be the same names, and one figure is a weight at 30 September while the other is a full-year contribution).
- [16]
About 41% of S&P 500 constituents sat between 10% and 20% below their 52-week highs at the end of September 2026.
- [17]
A fund that has fallen 8.4% needs a gain of about 9.2% to return to its starting value.
- [18]
The fund's net exposure has recently drifted lower as it has been finding more shorts in stocks that have yet to price in rising yields and inflationary pressures stemming from the Iran war.
- [19]
The letter says of the companies it has written about before: "remain very confident in their prospects and compelling value."
- [20]
The letter says: "We strongly believe that these steep price declines are unwarranted and partly reflect broader market rotations that have directed capital towards a narrow group of market leaders."
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Sources
1 independent publisher whose own reporting we read for this story.
- seekingalpha.comBristlemoon Global Fund Q3 2026 Report
1 article · October 13, 2026
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