Millions of 401(k) Holders Could Be Forced to Buy Anthropic Stock. Forced Buying of SpaceX Has Already Cost Retirement Accounts $500 Million.

Anthropic publicly filed its S-1 registration statement with the Securities and Exchange Commission on October 26, 2026, seeking to list Class A shares on Nasdaq under the ticker symbol ANT. The filing disclosed $16.3 billion in revenue for the first half of 2026, up from $1.1 billion in the same period a year earlier, and $16.8 billion in revenue for the third quarter, a 45% sequential increase. A net loss of $80.7 billion in the first six months looks alarming on its face, but roughly $72 billion of that figure reflects non-cash accounting charges tied to changes in the value of convertible notes rather than cash burned on operations. The company is targeting a listing in the week of November 16, with Goldman Sachs and Morgan Stanley leading an offering that could raise $100 billion or more and value Anthropic at between $1.5 trillion and $2 trillion. If Nasdaq applies the same accelerated inclusion rule it wrote for SpaceX, tens of millions of retirement accounts could become Anthropic shareholders without a single account holder placing an order. The SpaceX precedent shows exactly how that mechanism plays out.

The SpaceX Precedent

Space Exploration Technologies (NASDAQ:SPCX | SPCX Price Prediction) priced its IPO at $135 per share on June 11, 2026, raising roughly $75 billion in the largest initial public offering in history at the time. The stock closed its first trading day at $161, up 19% from the offering price. It then joined the Nasdaq-100 on July 7, 2026, just 15 trading days after listing, after Nasdaq revised its eligibility rules for newly public mega-cap companies. JPMorgan estimated that Nasdaq-100-tracking funds, chiefly Invesco’s QQQ, needed to purchase roughly $4.3 billion of SpaceX shares. That buying was executed during the July 6 closing auction so portfolios would match the index at the next day’s open. ETF.com put total passive demand tied to Nasdaq-100-linked products into the tens of billions of dollars, with some estimates in the $22 billion to $27 billion range. The forced buying priced through around $160 per share, well above the IPO price. Index funds buy what the rulebook tells them to buy.

The Swing

SpaceX has been volatile since its debut. Shares climbed as high as $225.64 shortly after the June IPO, then fell as low as $104.83 following its first quarterly report, which included heavy capital expenditures, and ahead of a first lockup expiration that made roughly 911.5 million additional shares eligible for sale by August 6. At that trough, the paper loss to index-fund holders on the forced buy was estimated at around $1.4 billion. As of late October 2026, SPCX trades around $145, roughly 9% below the $160 forced-buy price, leaving estimated unrealized losses to passive funds at approximately $400 million on that specific tranche. The stock recovered sharply in August and held near $160 through early October before drifting lower. SpaceX reported a blowout third quarter on October 20: revenue of $14.6 billion, up 161% year over year, net income of $4.4 billion versus a $1.1 billion loss in the prior year period, and EPS of $0.35 against a $0.13 consensus estimate. Even with those results, the stock pulled back modestly in the days that followed. SPCX remains volatile inside its $104.83 to $225.64 52-week range, and a full 180-day lockup expiration is scheduled for December 8 to 9, adding the next major tranche of potential supply to the float.

Why the Damage Is Contained

These are unrealized paper losses that can reverse as the stock moves. SpaceX represents about 0.9% of QQQ’s total portfolio, so Invesco QQQ Trust (NASDAQ:QQQ), which manages approximately $500 billion in assets, has absorbed the drag without meaningful disruption to overall performance. Several analysts are constructive on SpaceX following its Q3 earnings beat. JP Morgan raised its target to $500, Barclays raised to $300, and B of A Securities raised to $275, all in the week after the October 20 report. The December lockup expiration will be the next significant test of whether that analyst confidence holds against increased share supply.

Back to Anthropic

Anthropic’s situation closely parallels what SpaceX went through, but the numbers are larger. The company’s public S-1, filed October 26, confirms a Nasdaq listing under the ticker ANT and discloses H1 2026 revenue of $16.3 billion alongside Q3 revenue of $16.8 billion. The Wall Street Journal reported that Anthropic could provide a price range and share count in roughly two weeks, after gauging investor feedback, with a target listing in the week of November 16. The raise is reported to equal or exceed what SpaceX raised, meaning $75 billion at minimum, with some accounts putting the figure at up to $100 billion. The discussed valuation range of $1.5 trillion to $2 trillion is built on revenue growth that the New York Times reported in September was on pace to exceed a $100 billion annualized rate by year-end. Three things remain unsettled even now. Anthropic has not yet set a price range or share count. Nasdaq has not confirmed it will apply the fast-track inclusion rule to ANT. And even if it does, resulting passive flows depend on float, weighting, and the price at which buyers get filled in the closing auction. As for rival OpenAI, prediction market odds for a 2026 debut have collapsed; Polymarket showed September 30 IPO odds for OpenAI near 1% by late August, and most traders have pushed any OpenAI listing into 2027.

The Lesson

Index funds buy mechanically, following the rulebook. The SpaceX experience shows money moves in size, fast, and mark-to-market swings can erase or restore hundreds of millions of dollars in a matter of weeks. If Anthropic lists in November near its reported valuation and Nasdaq treats it the way it treated SpaceX, holders of Nasdaq-100 funds inside 401(k)s and IRAs may have little say in becoming ANT shareholders. The signals to watch are the final Anthropic prospectus with a price range, any Nasdaq statement on fast-track eligibility, and the closing auction on the trading day before index inclusion. That is where the check gets written.

Editor’s note: This update incorporates Anthropic’s public S-1 filing from October 26, 2026, which confirmed the ANT ticker, disclosed $16.3 billion in H1 2026 revenue and $16.8 billion in Q3 revenue, and shifted the IPO target to the week of November 16 with a potential raise of $100 billion or more. SpaceX price and estimated passive-fund loss figures have been updated to reflect late-October 2026 trading levels, and analyst price targets have been refreshed to include post-Q3-earnings raises from JP Morgan to $500, Barclays to $300, and B of A Securities to $275.

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