September 2026 · Interim Note
The Book Fell $324.47 Today. Palo Alto's $216.45 Gain Wasn't Enough to Offset SanDisk, AMD and Micron
The book closed at $33,113.09 today, down $324.47 from Friday’s $33,437.56 — a loss built on a rotation, not a single shared move. Public comments from Anthropic, OpenAI and xAI leadership calling for a slower, more safety-conscious pace of AI development, covered in full in today’s News piece, sent cybersecurity names higher and AI-infrastructure names lower on the same headline. Palo Alto Networks did the most work of any single position, up 13.09% and adding $216.45 by itself, followed by Meta (+$81.35), ServiceNow (+$58.92), CrowdStrike (+$57.28) and Fortinet (+$42.33). It wasn’t enough: SanDisk (−$162.72), AMD (−$113.60), Micron (−$102.46), the leveraged Nebius ETF (−$81.60), Intel (−$80.50) and Talen Energy (−$78.66) led 19 of my 32 positions lower. No trades.
Where the −$324.47 actually came from
Figure 1 · Dollar book impact by position, September 14
Palo Alto's $216 gain and four other winners still leave the book down $324
The nine largest single-day dollar movers in the 32-position book, September 11 to September 14, 2026 close, plus the remaining 23 positions grouped as one bar. Share counts × the change in each position's closing price, using my own share counts. Source: Massive Market Data.
Five of my nine largest single-day movers were the same cybersecurity-and-software names Anthropic's, OpenAI's and xAI leadership's public calls for slower AI development were treated as a tailwind for, per Zacks Investment Research: Palo Alto Networks, Meta, ServiceNow, CrowdStrike and Fortinet all closed higher on no company-specific news of their own. The other four of my nine largest movers — SanDisk, AMD, Micron, the leveraged Nebius ETF, Intel, Talen Energy and Vertiv — were on the other side of the same rotation, sold off as AI-infrastructure and chip-dependent names. Today’s Opinion piece goes further into what a narrative shock like this does and doesn’t tell you about actual AI demand.
| Position | Close | Day | Book impact | vs. my cost |
|---|---|---|---|---|
| Palo Alto Networks (PANW) | $373.94 | +13.09% | +$216.45 | +133.25% |
| Sandisk Corp (SNDK) | $1,551.99 | −4.98% | −$162.72 | +221.18% |
| Advanced Micro Devices (AMD) | $493.41 | −4.40% | −$113.60 | +147.52% |
| Micron Technology (MU) | $924.03 | −5.25% | −$102.46 | +183.59% |
| GraniteShares 2x Long NBIS (NBIL) | $21.80 | −11.09% | −$81.60 | +136.19% |
| Meta Platforms (META) | $665.60 | +2.71% | +$81.35 | +184.06% |
| Intel Corporation (INTC) | $97.19 | −5.59% | −$80.50 | +159.66% |
| Talen Energy Corp (TLN) | $286.52 | −8.38% | −$78.66 | −8.92% |
| Vertiv Holdings Co (VRT) | $237.39 | −7.65% | −$59.01 | −22.14% |
| ServiceNow Inc (NOW) | $142.35 | +7.41% | +$58.92 | +67.94% |
| CrowdStrike Holdings (CRWD) | $235.38 | +13.85% | +$57.28 | +148.40% |
| Arm Holdings plc (ARM) | $239.01 | −9.74% | −$51.56 | +15.00% |
| Fortinet Inc (FTNT) | $170.18 | +9.04% | +$42.33 | +101.87% |
| Alphabet Inc (GOOGL) | $349.39 | +3.22% | +$32.67 | +27.25% |
| CoreWeave Inc (CRWV) | $82.98 | −6.75% | −$30.05 | +0.05% |
| Datadog Inc (DDOG) | $230.05 | +4.00% | +$26.52 | +92.88% |
Arm, and what a 9.74% day means against a position already up 15% on my cost
Arm fell 9.74% to $239.01, costing the book $51.56 on 2 shares — the day's fourth-largest single-position swing after SanDisk, AMD and Micron. The Motley Fool's Daniel Sparks reported the same day that Arm is "down more than 40% from its 52-week high" on the broader AI-sector selloff, while noting the company's own Q1 results showed "record Q1 revenue growth of 22%" and "29% earnings growth," since Arm's royalty-based model "depends on chip shipments rather than AI timelines" directly. The same piece flagged the real tension: at "79x forward earnings," the stock still requires "years of extraordinary AI-driven growth to justify its price," which is exactly the assumption Monday's headlines put in question. Arm remains up 15.00% against my $207.83 average cost on 2 shares; today's move is a valuation repricing on a name I'm still ahead on, not a loss.
| If Arm (2 shares, $478.02 at today's close) moves… | Position value | Total book value | vs. today |
|---|---|---|---|
| Unchanged | $478.02 | $33,113.09 | — |
| Recovers today's own decline (+9.74%) | $524.58 | $33,159.65 | +$46.56 |
| Falls another 9.74% (today's own decline repeated) | $431.46 | $33,065.53 | −$46.56 |
| Falls to 79x forward earnings' historical median multiple, illustrative −25% | $358.52 | $32,993.59 | −$119.51 |
Assumptions, stated plainly. The $478.02 position value and today's 9.74% decline are my own real figures at today's close, from Massive Market Data. Only the "record Q1 revenue growth of 22%," "29% earnings growth" and "79x forward earnings" figures are sourced — to The Motley Fool's September 15, 2026 coverage of Arm's own reported results and valuation. The first two scenario rows reuse today's own real percentage move as an illustrative magnitude only, not a prediction. The 25% illustrative decline in the fourth row is a round number I chose to show sensitivity to a real, dated concern (elevated forward multiple) that the same article raised; it is not an analyst price target, not a multiple-compression model, and not this site's own forecast for Arm.
No trades today
The Blackout Rule and Holding Period exist for exactly this kind of session: a factor rotation across positions I've already underwritten, on a narrative headline rather than a disclosed change in any single business's orders or guidance, is not new information about Palo Alto, SanDisk, Arm, or any other name in the book. Today's move is explained by the same AI-development-pace headlines covered in today's News and Opinion pieces, not by anything company-specific. I made no trades.