Market snapshot · September 18, 2026 close
S&P 500 (SPY) $761.69 −0.13% Nasdaq-100 (QQQ) $721.45 +0.60% Dow (DIA) $515.88 −0.48% Russell 2000 (IWM) $284.10 −0.52% 10-Year Treasury (IEF) $90.80 −0.49% Crude Oil (USO) $153.82 −0.93% Gold (GLD) $401.17 +0.74% US Dollar Index (UUP) $28.39 −0.02% Volatility (VXX) $17.76 +0.31% Semiconductors (SMH) $573.00 +2.17% Silver (SLV) $59.93 +1.65% Emerging Markets (EEM) $67.03 +0.19% Bitcoin (BTC) $81,055.00 +4.51% Ethereum (ETH) $2,630.20 +5.92% S&P 500 (SPY) $761.69 −0.13% Nasdaq-100 (QQQ) $721.45 +0.60% Dow (DIA) $515.88 −0.48% Russell 2000 (IWM) $284.10 −0.52% 10-Year Treasury (IEF) $90.80 −0.49% Crude Oil (USO) $153.82 −0.93% Gold (GLD) $401.17 +0.74% US Dollar Index (UUP) $28.39 −0.02% Volatility (VXX) $17.76 +0.31% Semiconductors (SMH) $573.00 +2.17% Silver (SLV) $59.93 +1.65% Emerging Markets (EEM) $67.03 +0.19% Bitcoin (BTC) $81,055.00 +4.51% Ethereum (ETH) $2,630.20 +5.92%

August 2026 · Interim Note

Monday Reversed Friday: +$265.28, and SanDisk Alone Did 61.6% of the Work

August 31, 2026 · Not a full monthly letter — a short check-in between them

Close-up of hands typing on a laptop at a wooden desk
Writing this one up was easy math: one position did more than half the work.

The book rose $265.28 Monday, recovering a little more than half of Friday’s $430.79 loss. Sandisk did most of it by itself: 2 shares, up $81.72 apiece, for a $163.44 contribution — 61.6% of the entire day’s gain. Palo Alto Networks (+$52.70), Micron (+$51.74), AMD (+$25.70) and CrowdStrike (+$25.20) rounded out the winners; Meta (−$26.30) and Alphabet (−$21.72) were the largest drags. 17 of 32 positions closed higher. No trades.

+$265.28Net book impact, August 31 close vs. August 28
+$163.44Sandisk alone — 61.6% of the day’s gain, on 2 shares
−$26.30Meta, the day’s largest single drag
17 of 32Positions higher on the day

Where the $265 came from

Figure 1 · Dollar book impact by position

One position did more work than the next five combined

$+163 SNDK $+53 PANW $+52 MU $+26 AMD $+25 CRWD $+20 NOW $-20 EL $-21 CAKE $-22 GOOGL $-26 META $+15 Other 22

Share counts × the change in each position’s closing price, August 28 to August 31, 2026. The ten largest single-name movers are shown individually; the remaining 22 positions are bucketed as “Other 22” and net to +$15.10. Bars are independent day-over-day columns, not a cumulative waterfall. Source: Massive Market Data closes, applied to my own share counts.

This is close to the mirror image of Friday: one name did most of the work, rather than one name doing most of the damage. Sandisk rose 5.50% to $1,566.70, per a same-day Zacks Rank #1 upgrade citing a 17.1% rise in 60-day consensus earnings estimates — today’s News article covers the mechanism in full, alongside CrowdStrike’s guidance-driven rally on the other side of the tape. My 2-share Sandisk position is now up 224.23% against a $483.21 average cost — the single best return in the book, and the position I have thought hardest about trimming for exactly that reason.

Positions moving more than $15 · August 31, 2026 close
PositionCloseDayBook impactvs. my cost
Sandisk (SNDK)$1,566.70+5.50%+$163.44+224.23%
Palo Alto Networks (PANW)$382.13+2.84%+$52.70+138.35%
Micron (MU)$958.73+2.77%+$51.74+194.24%
AMD$470.72+1.10%+$25.70+136.14%
CrowdStrike (CRWD)$231.00+5.77%+$25.20+143.77%
ServiceNow (NOW)$147.99+2.27%+$19.68+74.60%
WhiteFiber (WYFI)$18.92+6.59%+$16.38+41.94%
Estée Lauder (EL)$102.30−1.05%−$19.62+48.00%
Cheesecake Factory (CAKE)$109.49−2.30%−$20.64+141.17%
Alphabet (GOOGL)$339.35−2.09%−$21.72+23.59%
Meta Platforms (META)$572.34−0.98%−$26.30+144.26%

The position I keep coming back to

Sandisk (SNDK) daily close vs. SPY, indexed, last 45 trading sessions through August 31, 2026. Source: Massive Market Data.

A same-day Motley Fool piece noted that Appaloosa Management’s David Tepper exited his entire Sandisk position in Q2 2026, according to the fund’s 13F filing, after the stock had run up more than 3,000% over a trailing year — the article frames it as profit-taking on a historically cyclical memory name at a stretched valuation, not a fundamentals call. I hold 2 shares against a $483.21 average cost, up 224.23% as of Monday’s close. That is a genuinely large unrealized gain sitting in a name whose entire investment case rests on a NAND-pricing cycle that has, historically, always turned. I have not trimmed it. I am not trimming it today either — the Holding Period exists so that a single strong day, or a single billionaire’s 13F, doesn’t force a decision I haven’t actually thought through.

No trades today

The Blackout Rule and Holding Period exist for exactly this kind of session. A one-day 61.6%-from-one-name gain is not new information about any company’s fundamentals, any more than Friday’s loss was. I made no trades.

Sources cited in full on the linked News article. Prices via Massive Market Data; dollar impacts computed from my own share counts. This note is educational and reflects my personal views only. It is not investment advice.