Anthropic Plans a Public Stock Sale, and Amazon Is Its Largest Backer
Anthropic, the company that makes the Claude AI models, has filed plans with the U.S. Securities and Exchange Commission for an initial public offering (IPO) of its Class A common stock. An IPO is the first time a private company sells shares to the public on a stock exchange. The company announced the filing on October 26, 2026. TechCrunch reports that its private valuation is $965 billion.
The filing, called an S-1, includes a table of the company's major shareholders. It lists holders of at least 5% of the company. No venture capital firm reaches that level. Menlo Ventures holds roughly $14 billion, or about 1.5%. The largest concentrated stake belongs to a strategic investor, meaning a large company that invests for business reasons rather than for financial returns alone.
That investor is Amazon. It first backed Anthropic in 2023, with a commitment to invest up to $4 billion. According to TechCrunch, Amazon's total investment is about $18 billion. That total includes $8 billion in convertible notes issued from 2023 through 2025, plus $10 billion in nonvoting preferred stock. Amazon put in the $10 billion during the second quarter, with $5 billion in each of Anthropic's last two funding rounds. Separately, Reuters reports that Amazon agreed in April to invest up to another $20 billion.
The notes are the harder part to understand. A convertible note is a loan that can later be exchanged for company shares. Amazon held $6.2 billion in principal on those notes as of June 30. Its filings valued the same holdings at $97.9 billion on that date. Anthropic recorded a $72.4 billion change in the fair value of its convertible notes, derivative liabilities, and SAFEs (simple agreements for future equity, another type of investment contract) for the first half of 2026. Bloomberg reports a full-year 2025 net loss of $42 billion, which it attributes largely to a rise in the fair value of the same notes.
The filing sets out how the conversion would work. The notes could convert into as many as 1.84 billion shares. The conversion is capped at 12% of Anthropic's partially diluted share count, a measure that counts shares that could be issued in the future. Amazon can waive that cap. The S-1 says the Amazon notes would convert into Class N common stock, which is a separate class from the Class A shares being offered to the public.
Anthropic's funding history fills in the rest. In September 2025, it completed a $13 billion Series F round, led by ICONIQ, at a $183 billion post-money valuation. Its Series H raised $65 billion. Anthropic says that total includes $15 billion of investments committed earlier by large cloud providers, among them $5 billion from Amazon. The round was announced on May 28, 2026. On September 11, Bloomberg reported that Nvidia was considering an investment of as much as $10 billion in the IPO.
Anthropic has also committed to spend at least $110 billion on Amazon Web Services (AWS) over the next 10 years. That means the company's computing purchases are tied to the same investor that holds the notes and preferred stock.
The product side moved quickly during the same months. Anthropic released Claude Opus 5.5 on September 22, 2026. The company says it costs 40% less to run than Opus 5 on typical workloads. Claude Sonnet 5.5 followed on September 28, and Claude Haiku 5.5 on October 7. On October 18, Anthropic said it would commit a portion of its shares to the Anthropic Public Benefit Fund. It also expanded its partnership with the General Services Administration, the U.S. government's procurement agency. Government partners will get a 40% discount on Claude Enterprise, Claude for Government, and the Claude API.
In my view, the number analysts will study most closely is not the $965 billion headline. It is the gap between $6.2 billion in note principal and a $97.9 billion value for the same holdings. That gap comes from the share-linked terms and the share price on the day the value is measured. Investors reading the filing will need to consider the 12% cap, the waiver, and the Class N conversion together, because those terms determine how much of the eventual public float Amazon's position would control.
The broader context here is a company whose computing costs, model prices, and government discounts are all changing at once, and whose financial structure must now be disclosed under public-company rules. Lower running costs for Opus 5.5 and discounted government pricing could allow more organizations to use Claude in their daily work. Whether that growth pays for the capital structure described in the filing is a question the public markets will now test.
