GetCoattail Research — SanDisk is the pure-play NAND flash maker spun out of Western Digital in February 2025, and in October it sits thirteenth on AltIndex's meme-stock list — after a year-to-date run above 600% on surging flash prices and AI data-centre demand, with analysts still raising targets into an October 29 earnings date. The filings describe a register that moved the other way at the top: two tracked superinvestors hold the stock, for 768 shares in total, after the cohort cut 99.73% of its position in the very quarter the price rose 257.9%, its insiders have never recorded an open-market purchase, and the borrow has halved from its June peak.
Start with the narrative. AltIndex's meme-stock list, updated on the night of October 11, ranked SanDisk thirteenth by Reddit mentions over the prior 24 hours, with 29 mentions and a bullish sentiment flag, at a displayed price of $1,581.82. The coverage behind the ranking is a price story: NAND flash prices surged through the first half of 2026, and reporting through the autumn has tied the move to tight supply and AI data-centre demand for storage. Analysts have spent October chasing the stock rather than calling its top: Bernstein reiterated a $3,000 target on October 5, Mizuho raised its target from $1,875 to $2,050, Rosenblatt initiated coverage with a Buy rating and a $2,400 target on September 22, and Citi held a $2,100 target on October 1, as reported across financial outlets in the week to October 7. The broader consensus, as aggregated by MarketBeat and reported in early October, reads Moderate Buy from 28 analysts with an average target of $2,113.92. The company's next earnings release is scheduled for October 29. Our own price file, which ends October 2, puts the last close at $1,719.99 — up 624.6% year to date on that file, 26.3% below the 252-session closing high of $2,335.00 set on June 25, 2026.
Now the filings. For SanDisk — the fortieth Filing Tape audit — the tape is a study in absence at the top of the register: a tracked cohort that all but exited during the steepest quarter of the run, a broad market that added two-thirds more filers in the same quarter, a 5% register with no activist filing at all, an insider record with zero purchases in it, a single congressional buyer, and a borrow that peaked in mid-June and has been retreating since.
Lens 1: the superinvestors — two holders, 768 shares, after a 99.73% cut
We track 83 large, mostly long-only managers whose 13F portfolios we collect directly from SEC EDGAR. As of June 30, 2026, 2 held SanDisk long — no option rows — totalling 768 shares worth $1,746,225. The direction count, on the collection's own labels, is one new and one decreased.
Lee Ainslie's Maverick Capital holds 575 shares worth $1,307,395, a 0.01% portfolio weight, flagged new — 74.9% of the tracked cohort's SanDisk shares. The only other holder is Polen Capital Management, with 193 shares worth $438,830, decreased 57.4% in the quarter. The cohort total moved from 281,703 shares at March 31 to 768 at June 30, a change of -99.73%, a difference of -280,935 shares — and the register underneath changed its membership entirely at the top: at March 31 the two rows were David Tepper's Appaloosa Management (281,250 shares) and Polen Capital Management (453 shares), and Appaloosa appears in the collection's exit list for this name in the second quarter, its prior position reported at $178,689,375. Polen's decrease, from 453 shares to 193, matches its collection label exactly, and the two collections' second-quarter totals match to the share. The price rose from $635.34 at March 31 to $2,273.73 at June 30, a change of +257.9%, and the cohort's reported value implies $2,273.73 per share, matching the June 30 close exactly. In other words, the quarter in which SanDisk's price more than tripled is the quarter in which the famous-money register went from 281,703 shares to a position smaller than a single retail lot in either name.
Lens 2: institutions — 1,826 filers, up 663 in one quarter, shares up 10.85%
Zoom out to the whole 13F market and the June quarter was a broadening register. At June 30, 2026, 1,826 institutions reported positions, up 663 from 1,163 at March 31 (+57.01%), and 1,812 reported long positions. Reported shares rose 10.85%, from 98,504,884 to 109,188,672 shares — 10,683,788 more shares than the prior quarter. Reported aggregate value rose 347.41% to $350,045,091,464; the aggregate includes option rows, so we headline filer and share counts and label dollars "reported" (see methodology). That caution matters more here than in most audits: the implied value per share, $3,205.87, sits 41.0% above the June 30 close of $2,273.73, because the reported total sums every information-table row while the share count covers long common-stock rows only. Set the two 13F lenses side by side and they point in opposite directions: the full market's filer count grew 57.01% and its share count grew 10.85%, while the tracked cohort's fell 99.73%. The broad register spent the quarter arriving; the famous names spent it leaving, down to a 768-share remainder.
Lens 3: the 5% register — nineteen filings, all of them passive, none of them 13D
Our full parse holds nineteen SC 13D/G filings for SanDisk — seven SC 13G originals and twelve SC 13G/A amendments, and no SC 13D filing at all, twelve reporting persons on a row basis, the most recent filed August 6, 2026. The register's maximum percentage belongs to the former parent: Western Digital Corporation printed 28,827,787 shares (19.9%) as of March 31, 2025, then 7,513,019 shares (5.2%) as of June 30, 2025, then 1,038,681 shares (0.7%) as of March 31, 2026 — a separation register unwinding on paper, reported here exactly as filed. The Vanguard Group printed 16,554,878 shares (11.39%) as of June 30, 2025, followed by an amendment printing 0 shares (0.0%) as of March 13, 2026 — while Vanguard Capital Management, a separate reporting-person name, printed 11,000,476 shares (7.17%) as of March 31, 2026. We report the rows exactly as filed and never merge the two Vanguard names. FMR LLC, whose rows are printed jointly with Abigail P. Johnson at identical share counts, is the register's most recent filer: 20,574,141.22 shares (14.2%) as of March 31, 2025, then 13,389,385.08 shares (8.7%) as of March 31, 2026, then 7,861,064.22 shares (5.3%) as of June 30, 2026, in the filing dated August 6, 2026. BlackRock's latest row prints 8,825,007 shares (6.0%) as of December 31, 2025, down from 15,790,988 shares (10.9%) as of June 30, 2025. The newest event date in the register belongs to the Jane Street group: as of July 30, 2026, a single filing prints JANE STREET GROUP, LLC at 7,409,437 shares (5.0%), alongside Jane Street Capital, LLC at 5,886,992 shares (4.0%), Jane Street Global Trading, LLC at 1,284,343 shares (0.9%) and Leonard Street Holdings, LP at 238,102 shares (0.2%) — group and component rows in one filing, which we report as filed and never sum. We report rows as filed and never sum them across the register either: the aggregation's total across these rows would add different dates together and present a history as if it were a register total. The structural fact of this lens is the empty half: nineteen filings, all passive 13G paper, and not one 13D — no filer in this register has declared an active intent.
Lens 4: insiders — zero purchases in the parsed record, $133,769,706.28 of sales
The parsed Form 4 record holds 115 filings through October 2, 2026. Across it, open-market purchases total zero transactions — none in the full record, none in the last year, and none in the last 90 days. Against that stand 76 sales totalling 88,895 shares and $133,769,706.28, by seven sellers, 73 of the 76 recorded as officer sales. The last year holds exactly the same totals as the full record — every sale in the parsed coverage falls inside it — and the last 90 days hold most of the weight: zero purchases against 67 sales of 77,899 shares for $121,159,030.23 by four sellers, every one of the 67 recorded as an officer sale. Our site's insider aggregate, compiled as of October 11 over its 90-day window, records the same zero purchases but counts 66 sales totalling $120,118,066.23 — one transaction and $1,040,964.00 fewer than the full parse. We headline the full parse, print both figures in the methodology, and note that the two agree on the fact this lens is about: in the parsed record, no SanDisk insider has ever bought a share on the open market. We assign no motives to any of it; the record's shape is the fact — and the shape here is one-directional across the whole coverage, with an empty column on the other side.
Lens 5: Congress — one member, one purchase, no sales
Across the congressional record we maintain (combined record as of October 3, 2026), SanDisk shows one member, one purchase transaction and no sale transactions, with the most recent purchase dated May 7, 2026, and the member's party recorded as Democratic. The House aggregate (as of October 3, 2026) carries the same single member, the same single purchase and the same last-buy date; the Senate aggregate (as of October 1, 2026) carries no SanDisk row at all, so the combined record is entirely a House record. Congressional disclosures report value ranges rather than amounts, so this lens records direction and counts only; here it records a small, one-sided presence — the only lens in this audit where the tracked money bought and did not sell.
Lens 6: short interest — 5,618,213 shares, down 48.5% from the June peak
FINRA's files carry the borrow across 38 settlements, from February 28, 2025 — the first settlement after the stock's February 2025 listing in our price file. As of September 15, 2026 — the most recent settlement — 5,618,213 SanDisk shares were sold short, with days-to-cover of 1.00, down 6.30% from the prior settlement. Against the fundamentals file's 146,419,001 shares outstanding, that is 3.84% of the share count. The direction is what makes this reading unusual: the series maximum is 10,911,306 shares at the June 15, 2026 settlement — inside the quarter the price tripled — so the borrow has since fallen 48.5% from its peak. Against the June 30, 2026 settlement reading of 7,197,631 shares — the same date the 13F lenses snapshot — the latest reading is down 21.9%. Year over year the latest reading is down 9.6% from 6,213,553 shares on September 15, 2025. The series minimum is 4,344,606 shares on March 31, 2025, and the first settlement in the series, on February 28, 2025, printed 8,810,660 shares.
The recent settlements run 7,857,690 on July 15, then 6,823,953, 7,676,558, 5,996,105 and 5,618,213 — a borrow stepping down from its June peak rather than building into the autumn. Set beside the price file, the geometry is the year's story in one line: the stock closed at $1,719.99 on October 2, up 624.6% year to date, while the borrow against it stands at barely half the level it reached in June.
The gap, stated plainly
The registers describe a stock the analyst community spent October marking up — target raise after target raise, a consensus average target of $2,113.92, an October 29 earnings date ahead — months after its institutions had already moved, in opposite directions. The tracked superinvestors held 768 shares at June 30 — two holders, Maverick Capital's 575 shares at 74.9% of it — having fallen 99.73% in a quarter when the price rose 257.9%, after Appaloosa Management exited a 281,250-share position. The full market moved the other way: 1,826 filers, up 663, holding 109,188,672 reported shares, up 10,683,788. The 5% register printed nineteen filings, every one of them passive: a Western Digital row that has unwound from 19.9% to 0.7%, a Vanguard Group row that went to zero under that name while a Vanguard Capital Management row printed 7.17%, an FMR row down to 5.3% at June 30, and not one 13D. Insiders, across 115 parsed filings, have recorded zero open-market purchases against $133,769,706.28 of sales by seven sellers, with $121,159,030.23 of that selling inside the last 90 days. Congress registers one member who bought once and has not sold. And the borrow, at 5,618,213 shares, sits 48.5% below the peak it set in June, inside the steepest quarter of the run. One plausible reading is that the registers run on different clocks and different mandates: the broad market spent the June quarter arriving in a stock its tracked-fund register was all but abandoning, no activist has filed on the name, its own insiders have never bought across the whole parsed record, and short sellers built their largest borrow at the top of the June quarter and have been retreating since. The record supports each clause separately; it does not say which register is right.
What would change the picture
Nothing above is a recommendation. It is a record. These are the filings that would change the description:
- 1. The 2026Q3 13Fs (filing window closing mid-November 2026). The tracked cohort held 768 shares at June 30 across two holders, after a 99.73% cut, with Maverick Capital at 575 shares. Whether that remainder rebuilds, holds or disappears is the whole lens; an Appaloosa Management return would be the rest of it.
- 2. A first insider purchase. The parsed record holds zero purchase transactions across 115 filings, against $133,769,706.28 of sales. Any open-market purchase print — above all an officer purchase — would break the record's shape; continued silence would extend it.
- 3. A first 13D filing. The 5% register holds nineteen filings, all passive 13G paper, headed on the latest event date by the Jane Street group's 7,409,437-share row (5.0%). A first 13D — any filer declaring active intent — would change this lens from a register of index and separation positions into something else.
- 4. Whether the borrow returns to its peak. Short interest printed its series maximum of 10,911,306 shares at the June 15, 2026 settlement and stands at 5,618,213. A return toward that maximum would rebuild the June picture; a fall below the series minimum of 4,344,606 would extend the retreat.
- 5. Whether Congress adds a second member. The congressional register holds one member and one purchase. A second member's first print, in either chamber, would widen this lens beyond a single name.
Until one of those prints, the record describes a stock held by two of our 83 tracked superinvestors — 768 shares, 74.9% of it one holder, after a 99.73% one-quarter cut in which the largest holder exited — whose full market added 663 filers and 10,683,788 reported shares in the same quarter, whose 5% register is entirely passive paper headed by a former parent unwinding from 19.9% to 0.7%, whose insiders have bought zero shares across the parsed record against $133,769,706.28 of sales, whose congressional register is a single member who bought once, and whose borrow has halved from the peak it set in the quarter the price rose 257.9%.
Related reading: Seven of 83: One Holder Is 82.6% of the Superinvestors' McDonald's Stake. The Cohort Cut 24.8% in Q2. — Filing Tape #39; Two of 83: The Superinvestors Cut eBay 31.4% in Q2. GameStop's Filings Show a 9.8% Stake. — Filing Tape #38; Zero of 83: The Superinvestors Aren't in IREN — Filing Tape #1. SanDisk's own page: SanDisk Corporation (SNDK) on GetCoattail.
Methodology and data notes
- Superinvestor lens: 83 managers collected directly from SEC EDGAR Form 13F (managers_13f collection), positions as of June 30, 2026; SanDisk identified by CUSIP 80004C200. Two distinct managers hold long positions totalling 768 shares; both reported rows are long (no put or call rows); directions on the collection's labels are one new and one decreased, and the collection's exit list contains one row for this CUSIP (David Tepper - Appaloosa Management, 281,250 shares, prior reported value $178,689,375). Quarter-to-quarter cohort totals (281,703 shares at March 31 across two filing rows — David Tepper - Appaloosa Management 281,250 and Polen Capital Management 453 on the pipeline's CUSIP basis; 768 shares at June 30 across two filing rows; change -99.73%) are from the site pipeline's holdings files on the same CUSIP basis in both quarters, and the pipeline's second-quarter total matches the EDGAR collection's long total exactly (difference of 0 shares and $0). Polen Capital Management's collection label (decreased 57.4%) matches the pipeline recalculation (193 / 453 − 1); Maverick Capital's row is new, with no first-quarter row in either collection. Lee Ainslie - Maverick Capital's share of the cohort is 74.9% = 575 / 768.
- Full-market lens: SEC Form 13F Data Sets full-market aggregation. The primary table is the full13f collection's by-ticker file (holders = distinct filers reporting the CUSIP; 1,812 of the 1,826 reported long positions), and its figures match the backfill fixtures' by-CUSIP row for 80004C200 exactly on holders, shares, reported value, prior holders and prior reported value. The by-ticker file's entered/exited fields (1,588 and 925, a net of +663 that matches the change in holder count) have no counterpart in the by-CUSIP aggregation, which does not publish them, so this audit does not rely on them. Reported-value caution: the aggregate value ($350,045,091,464 over 109,188,672 shares) implies ≈$3,205.87 per share against a June 30, 2026 close of $2,273.73 in our price file, a gap of +41.0%. The aggregate sums the VALUE of every information-table row — including put and call option rows — while the share count covers long common-stock rows only, so we headline filer and share counts and label dollar values "reported."
- Insider lens: full-parse Form 4 aggregation (agg_by_ticker), record as of October 2, 2026 (115 filings). Sale and purchase counts are transaction-code counts (S and P) in non-derivative rows; grants and exercises are not counted as purchases, and one filing can contain many transaction rows. Purchase transactions total 0 across the parsed record — in the full record, in the year through October 2, 2026, and in the 90 days through October 2, 2026 alike. Sale transactions total 76 across the record and the year alike (88,895 shares, $133,769,706.28, seven sellers, 73 of the 76 recorded as officer sales), and 67 in the 90 days through October 2, 2026 (77,899 shares, $121,159,030.23, four sellers, all 67 recorded as officer sales). The site's insider aggregate (compiled as of October 11, 2026, 90-day window) records zero purchases, 66 sales and $120,118,066.23 of sale value — one transaction and $1,040,964.00 fewer than the full parse's 90-day window; the two agree on zero purchases, and both figures are printed here rather than blended. "Purchases" in this audit is scoped to this parsed record, whose 115 filings are the coverage stated here.
- 13D/G lens: full-parse SC 13D/G aggregation and parsed filings (19 filings matching CUSIP 80004C200 and issuer CIK 2023554, twelve reporting persons on a row basis: 7 SC 13G originals and 12 SC 13G/A amendments, no SC 13D filings), filings through August 6, 2026. Western Digital Corporation's rows (28,827,787 shares at 19.9% as of March 31, 2025, filed April 3, 2025; 7,513,019 shares at 5.2% as of June 30, 2025, filed July 1, 2025; 1,038,681 shares at 0.7% as of March 31, 2026, filed May 15, 2026), The Vanguard Group's rows (16,554,878 shares at 11.39% as of June 30, 2025, filed July 29, 2025; 0 shares at 0.0% as of March 13, 2026, filed March 27, 2026), Vanguard Capital Management's row (11,000,476 shares at 7.17% as of March 31, 2026, filed April 30, 2026), FMR LLC's rows (20,574,141.22 shares at 14.2% as of March 31, 2025; 13,389,385.08 shares at 8.7% as of March 31, 2026; 7,861,064.22 shares at 5.3% as of June 30, 2026, filed August 6, 2026 — each printed jointly with Abigail P. Johnson at identical share counts), BlackRock, Inc.'s rows (15,790,988 shares at 10.9% as of June 30, 2025; 8,825,007 shares at 6.0% as of December 31, 2025, filed January 21, 2026) and the Jane Street filing's rows (JANE STREET GROUP, LLC 7,409,437 shares at 5.0%, Jane Street Capital, LLC 5,886,992 shares at 4.0%, Jane Street Global Trading, LLC 1,284,343 shares at 0.9% and Leonard Street Holdings, LP 238,102 shares at 0.2%, all as of July 30, 2026, filed August 5, 2026) are reported as filed, under the reporting-person names exactly as they appear. No rows are summed, because the aggregation's totalSharesReported field (276,481,034.5 shares) adds different dates together. No reason for any change is asserted — the filings themselves are the record.
- Congress lens: Senate PTR archive and House PTR archive as maintained on this site, combined record as of October 3, 2026 — one member, one purchase transaction, no sale transactions, most recent purchase May 7, 2026, party Democratic. The House aggregate (as of October 3, 2026) carries the same member, purchase and date; the Senate aggregate (as of October 1, 2026) carries no SanDisk row at all. Congressional disclosures report value ranges, so this lens records direction and counts only.
- Short interest lens: FINRA Equity Short Interest files (biweekly settlement dates), collected directly from FINRA's public distribution. The published series covers 38 settlements from February 28, 2025 (8,810,660 shares — the first settlement in the files after the stock's February 2025 listing) to September 15, 2026. The maximum of the series is 10,911,306 shares on June 15, 2026, so the latest reading of 5,618,213 shares on September 15, 2026 sits 48.5% below the peak ((5,618,213 / 10,911,306) − 1), 21.9% below the June 30, 2026 settlement reading of 7,197,631, and 9.6% below the September 15, 2025 reading of 6,213,553; the change from the prior settlement is -6.30%. The latest row's prior-settlement field (5,996,105) matches the prior settlement file's reported figure exactly. The series minimum is 4,344,606 shares on March 31, 2025. FINRA publishes each settlement about two weeks after the fact. The share-count ratio (3.84%) uses the fundamentals file's shares-outstanding figure below.
- Fundamentals note: our fundamentals collection carries SanDisk's revenue of $20,248,000,000 labelled fiscal 2026, its net income of $11,433,000,000 labelled fiscal 2026, and its assets of $22,507,000,000 labelled fiscal 2026 — all three fields carry the same fiscal year in the file. The file is marked ok for this name, with no missing fields: shares outstanding of 146,419,001 (as of August 7, 2026, sourced in the file to an EntityCommonStockSharesOutstanding count) and a file-computed market value of $243,122,888,680.97. The file's price for the name is $1,660.46 as of October 6, 2026; our daily-close file ends October 2, 2026 at $1,719.99, and we keep the two files' figures separate rather than blending them.
- Prices: our own daily-close file for SanDisk through October 2, 2026 ($1,719.99 close, +624.6% year to date on that file; 252-session closing high $2,335.00 on June 25, 2026; 252-session closing low $116.91 on October 10, 2025; closes of $635.34 at March 31, 2026 and $2,273.73 at June 30, 2026, a second-quarter change of +257.9%; change from June 30 to October 2 of -24.4% ((1,719.99 / 2,273.73) − 1)). The drawdown from the 252-session closing high is -26.3%, and the series in our price file begins February 13, 2025 at $36.00.
- Market context sources: AltIndex's meme-stock list as updated on the night of October 11, 2026 (SanDisk thirteenth by Reddit mentions over the prior 24 hours, 29 mentions, bullish sentiment flag, displayed price $1,581.82), checked October 11, 2026; the NAND pricing and AI data-centre demand backdrop reported across financial outlets through October 2026 (flash prices surging in the first half of 2026 on tight supply, per TrendForce figures reported by Motley Fool), checked October 11, 2026 and summarised in our own words; the run of analyst targets reported across financial outlets in the week to October 7, 2026 (Bernstein $3,000 reiterated October 5; Mizuho raised from $1,875 to $2,050; Rosenblatt initiated at Buy with a $2,400 target on September 22; Citi $2,100 held on October 1) and the analyst backdrop aggregated by MarketBeat (Moderate Buy consensus, average price target of $2,113.92, 28 analysts) as reported in early October 2026; and the company's scheduled October 29, 2026 earnings release, announced September 29, 2026. Figures we could not confirm against two sources were left out.
- SanDisk is in the GetCoattail stock-page universe: SanDisk Corporation (SNDK) stock page. Series data: sndk_lens_data.csv · sndk_short_interest_series.csv. Earlier audits: McDonald's · eBay · IREN.
Past patterns are not a promise of future results. For education only — not investment advice.
This article describes public filings as of the dates stated. It is not investment advice and makes no recommendation. Filings lag reality: 13F positions are as of June 30, 2026, and later trading is not yet public.
Revision history
- v1.0 — October 11, 2026: first publication.