Seven of 147: Jericho Is 52.1% of the Superinvestors' Western Digital Stake. Its Insiders Have Never Bought a Share.

GetCoattail Research — The Filing Tape #138. Western Digital topped MarketBeat's gainers list on Monday, and the filings behind that move describe a stock the tracked money mostly watched: 7 of the 147 superinvestors held the common stock at June 30, 2026, totalling 1,238,026 shares — Jericho Capital alone is 644,764 of them, 52.1% of the tracked stake. The four holders who were already there shrank 3.8% between them during a quarter when the price rose 136.1%, and the register grew only because three small new positions arrived. Inside the company, the record is one-directional: across 237 Form 4 filings, insiders have sold 238 times and have never bought a share.

The Hype

Western Digital's attention this week is event-driven. The storage maker reports its fiscal first-quarter results after the close on October 22, 2026, and the memory sector around it is swinging both ways — TradingKey reported the group giving back Monday's rebound in Tuesday pre-market trading. TradingKey Our price file shows why the stock draws a crowd: Western Digital rose 136.1% in the second quarter, from $270.49 on March 31 to $638.72 on June 30, after touching a 252-session high of $746.23 on June 18 — then fell back to $415.29 by October 2, down 35.0% from the quarter-end close and 44.3% below that high, while still up 141.1% year to date and 216.4% from a year ago. A stock that more than doubled in a quarter and then lost a third of its value: the filings answer who held it through the rise, who added, and who sold into it.

The Tape

For Western Digital — the one hundred and thirty-eighth Filing Tape audit — the tape shows a seven-name tracked register whose continuing holders shrank in a rising quarter, a full market that added hundreds of filers, an insider record with no purchase in it at all, a single congressional purchase, a passive-only 5% register, and a borrow that has fallen by more than half in a year.

Lens 1 — the superinvestors: seven holders, and the continuing four shrank. We track 149 managers whose 13F portfolios we collect from SEC EDGAR — 147 are in the collection (144 at a June 30 period-end, 3 early filers at September 30, none holding this name at September 30, so there is no period split) — and the June 30, 2026 register for the common stock (CUSIP 958102105) is 7 distinct managers holding 1,238,026 shares worth $790,752,177, long only, with no option rows: 3 are labelled NEW, 2 INCREASED and 2 DECREASED, with no exits during the quarter. Jericho Capital Asset Management is the register's largest holder: 644,764 shares worth $411,823,662 — 52.1% of the tracked stake — at a 3.40% portfolio weight, labelled INCREASED +10.9% (filed August 14, 2026). Whale Rock Capital Management is next (400,687 shares, 32.4% of the cohort, DECREASED -2.7%, at a 2.05% weight), so the top two holders together are 84.4% of the tracked stake. Behind them sit Samlyn Capital (87,577 shares, DECREASED -53.7%), Atalanta Sosnoff Capital (39,864 shares, NEW), Winslow Capital Management (31,678 shares, NEW), Tortoise Capital Advisors (31,574 shares, INCREASED +13.1%) and Lee Ainslie - Maverick Capital (1,882 shares, NEW). Verified row by row for all four continuing holders under two register methods that agree exactly (methodology), those four held 1,210,761 shares at March 31 and 1,164,602 at June 30 (-3.8%) — two raised and two cut, with Samlyn's position more than halved. The full register still grew 2.3%, to 1,238,026 shares, only because the three new holders added 73,424 shares between them; the register reconciles with no residual. All seven common rows imply $638.72, the June 30 close (methodology). One further tracked row in this name is not stock at all: Aequim Alternative Investments reports a 3.000% note position valued at $1,023,118,949 — larger than the entire common-stock cohort — which this audit counts as debt, not as a holding (methodology). 13F figures are as of June 30, 2026, published up to 45 days later.

Lens 2 — institutions: 454 more filers, and 12.84% more shares. At June 30, 2026, 1,856 institutions reported positions, up 454 from 1,402 at March 31 (+32.38%); 1,843 are long. Reported shares rose 12.84% to 321,314,544 (+36,568,840 shares), and reported value rose 175.84% to $231,058,136,546, labelled "reported" because the aggregate includes option rows (methodology), in a quarter when the price rose 136.1%. Flow counts agree (1,555 entered, 1,101 exited, net +454). The single-CUSIP breakdown matches the by-ticker aggregate on every field (methodology). Against that full-market total, the tracked superinvestor cohort's 1,238,026 shares are 0.39% of reported institutional shares.

Lens 3 — insiders: sales only, across the entire record. The parsed Form 4 record holds 237 filings through October 2, 2026, and it contains no open-market purchase at all — 0 purchases by 0 buyers, in the last 90 days, in the last year and across the full record, officer purchases included. The last 90 days hold 49 sales (35,037 shares for $15,777,916.51, by 5 sellers, 14 of them officer sales); the last year holds 224 sales (254,343 shares for $74,949,413.31, by 10 sellers, 97 of them officer sales); and the full record holds 238 sales (319,541 shares for $79,616,836.74, by 11 sellers, 111 of them officer sales). The sales imply $450.32 per share over the last 90 days, $294.68 over the last year and $249.16 across the full record — every cited figure sits inside its window's close range on our price file (methodology). The site's insider aggregate, which runs on a later window, also records 0 purchases for this name (methodology).

Lens 4 — Congress: one purchase, in the House. The combined aggregate (as of October 3, 2026) records 1 member, 1 purchase and 0 sales, with the purchase dated July 17, 2026 (party D). The House aggregate carries the same single row; the Senate aggregate (as of October 1, 2026) carries no row for this name. The aggregates record counts and dates, not amounts, so the size of that one purchase is not something this lens can state.

Lens 5 — the 5% register: fifteen passive filings, maximum 10.1%. Our full parse holds 15 SC 13D/G filings matching the site aggregate — 0 SC 13D family and 15 SC 13G family (3 SC 13G, 12 amendments); 7 reporter names across 21 reporter rows. The maximum is FMR LLC at 34,466,664.32 shares and 10.1% as of December 31, 2025 (filed January 8, 2026, SC 13G/A). The latest is FMR LLC at 26,361,315.39 shares and 7.2% as of June 30, 2026 (filed August 6, 2026, SC 13G/A). FMR LLC and Abigail P. Johnson co-report the same position in six of the filings, and one further file in the register, from The Vanguard Group, prints 0 shares (methodology).

Lens 6 — short interest: less than half its year-ago size. The latest FINRA settlement, September 15, 2026, records 17,280,387 shares sold short — 4.79% of the 360,540,944 shares outstanding — at 3.13 days to cover, down 13.11% from the prior settlement. The series peak across all 137 settlements is 39,478,138 shares, set on September 15, 2025 — exactly the year-ago settlement — so the latest reading sits 56.2% below both the peak and its year-ago level, and 22.8% below the June 30, 2026 settlement (22,377,149 shares). The recent path runs 22,377,149 (June 30), 23,258,520 (July 15), 24,599,617 (July 31), 20,281,115 (August 14), 19,887,791 (August 31) and 17,280,387 (September 15) — two rises, then three consecutive falls. No step in the full series reaches 2x, and none falls to half (methodology).

The Gap

The narrative arriving this week is a momentum-and-earnings one: the sector's most volatile name, reporting on October 22 after a quarter in which it rose 136.1%. The June tape backs only a watching version of that story. The broad market did arrive — 454 more filers and 12.84% more shares — but the tracked cohort's continuing holders, the four managers who already owned the stock before the rise, shrank 3.8% between them, and the two who cut include the register's second-largest holder and a holder who more than halved. The register's growth came from three new positions totalling 73,424 shares, the largest of them 39,864 shares. Inside the company there is no buy side at all: 238 recorded sales and not one purchase — $15,777,916.51 of selling in the last 90 days alone, while the stock fell from its high. The borrow tells the other half: at 17,280,387 shares it has fallen 56.2% from its peak while the price first doubled and then corrected. The only outright purchase anywhere in these filings is a single House member's, dated July 17, 2026. One plausible reading is that the filings caught a repricing that most of the recorded money observed rather than joined: institutions broadly held more of a much more expensive stock, the tracked cohort's incumbents trimmed into the rise, insiders sold as they have always sold, and the shorts covered into strength.

What Would Change the Picture

Nothing above is a recommendation. These filings would change it:

• 1. The 2026Q3 13F season (filing window closing mid-November 2026). The verified continuing baseline is 1,164,602 shares across four holders, and Jericho Capital's is 644,764 shares — 52.1% of the tracked total. Whether the two holders who cut in Q2 keep cutting, whether the three Q2 newcomers add to positions that began at 73,424 shares combined, and whether any further tracked holder appears would each change this lens.
• 2. A first insider purchase — ever. The parsed record holds 0 purchases against 238 sales, including 49 sales in the last 90 days. Any recorded open-market purchase would be the first in this record and would change this lens outright; continued selling above the recent 90-day pace would deepen it instead.
• 3. A second congressional transaction. The combined aggregate holds one House purchase, dated July 17, 2026, and the Senate holds none. A second member, a House follow-on purchase, a first sale, or any Senate row would each change this lens.
• 4. A first SC 13D filing, or a new 5% print above 10.1%. The register's 15 filings are all SC 13G family, and its latest print has FMR LLC lower, at 7.2%. A first activist-form filing, or any print above FMR LLC's 10.1% maximum, would change this lens.
• 5. Short interest back above the June 30 settlement, or a new leg down. The borrow stands at 17,280,387 shares, 22.8% below the June 30, 2026 settlement of 22,377,149 and 56.2% below the September 15, 2025 peak of 39,478,138, after three consecutive falls. A reading back above 22,377,149 would break the unwind; a reading below 17,280,387 would extend it.

Related reading: Four of 147: Slate Path Is 65.3% of the Superinvestors' Cleveland-Cliffs Stake. Short Interest Is 14.08% of the Share Count.; Eleven of 147: Winslow Is 34.3% of the Superinvestors' Arista Stake. Its Insiders Have Never Bought a Share.. Western Digital's own page: Western Digital (WDC) on GetCoattail.

Methodology and data notes

• As-of & limits: The lenses rest on different clocks, none live: 13F is a June 30, 2026 snapshot published up to 45 days later; Form 4 runs through October 2, 2026; Congress aggregates run through October 3, 2026 (Senate through October 1, 2026); 13D/G through August 6, 2026; short interest through September 15, 2026; the price file ends October 2, 2026. Seven limits are specific to this audit. First, the roster expanded before the recent audits — from 85 managers (83 filing) to 149 (147 filing) — so "of 147" counts are not comparable to earlier pieces' "of 83" figures. Second, this name carries no period split in its headline count — all seven tracked common-stock holders sit on a June 30, 2026 period-end and none of the three September 30, 2026 early filers holds this name — and the register reconciles exactly: the March 31 register (1,210,761 shares) equals the verified continuing cohort's Q1 total with no exits, and the June 30 register (1,238,026 shares) equals that cohort's Q2 total (1,164,602) plus the three new holders' 73,424 shares, as detailed in Lens 1. Third, the tracked register carries one row that is not common stock: Aequim Alternative Investments reports a note position (CUSIP 958102AT2, "NOTE 3.000%11/1") at 60,500,000 reported units worth $1,023,118,949, a 15.9% portfolio weight, labelled INCREASED +9.0% (filed August 11, 2026). It is a debt row: it is excluded from every share count, holder count and value total for the common stock in this audit, and it is disclosed here because its reported value exceeds the common cohort's $790,752,177. Fourth, the full-market aggregate for this issuer rests on a single CUSIP line (CUSIP 958102105), and the by-CUSIP row matches the by-ticker aggregate on every field; its implied price of $719.10 sits 12.58% above the June 30 close of $638.72 because the reported aggregate includes option rows, which is why share counts, not reported value, are this audit's primary institution measure. Fifth, the insider record's two aggregations differ by window: the site's 90-day insider aggregate (dated October 20, 2026) records 48 sales worth $15,349,975.47 by 5 sellers for this name, against the full parse's 49 sales worth $15,777,916.51 in its 90 days to October 2, 2026 — a difference of one sale and $427,941.04 created by the 18-day window shift; both aggregations record 0 purchases, and this audit cites the full parse throughout. Sixth, the 5% register's cross-date share total of 488,472,552.18 sums prints from different dates and is not a current stake; within it, FMR LLC and Abigail P. Johnson co-report the same position in six filings (each such filing contributes two reporter rows with identical share counts), several FMR prints carry fractional share counts as filed, and one file — The Vanguard Group at 0 shares and 0.0% as of March 13, 2026 (filed March 27, 2026, SC 13G/A) — is keyed to the same CUSIP, so it sits inside the aggregate by definition and changes neither the maximum nor the economics of the register. Seventh, the short-interest series carries one revision flag (June 15, 2021) and no split flag; our price file records one adjustment entry for this name (February 24, 2025, factor 1.323), the settlement steps around that date are unremarkable (the largest is +22.23%), and no settlement step in either direction reaches the 2x or one-half thresholds (largest step 1.893x at the November 15, 2023 settlement, smallest 0.712x at the October 31, 2022 settlement), so settlements across the full series are compared directly. All seven tracked common-stock 13F rows imply the June 30 close of $638.72 (one rounds to $638.73), and the cohort's blended implied price is $638.72. The company's fundamentals as collected print fiscal 2026 revenue of $12,919,000,000 (collected from the RevenueFromContractWithCustomerExcludingAssessedTax concept), net income of $9,424,000,000 and assets of $13,861,000,000, with 360,540,944 shares outstanding as of August 7, 2026; those figures are reported as collected and are not used in any lens above. Every price statement here is mechanical, a date and a close from our price file. The TradingKey report (published October 20, 2026) postdates the 13F snapshot and the short-interest series; none of its figures are cited here beyond the earnings date and the sector move it reports, reported as outlet content in The Hype.
• Market context sources: TradingKey, "US Memory Sector Slides Again Pre-Market as Micron, SanDisk, Western Digital Erase Monday Gains", published October 20, 2026 (Western Digital fiscal first-quarter results scheduled after the close on October 22, 2026; memory stocks lower in pre-market after Monday's rebound). Figures we could not confirm were left out; the external item above is reported speech from that outlet, not a GetCoattail measurement.
• Western Digital is in the GetCoattail stock-page universe: Western Digital (WDC) stock page. Series data: wdc_lens_data.csv · wdc_short_interest_series.csv. Earlier audits: Cleveland-Cliffs · Arista Networks.

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 20, 2026: first publication.