Amazon set to be the biggest winner from Anthropic's IPO, filing shows

Anthropic’s initial public offering filing shows that Amazon, not any of the company’s venture investors, stands to make the most money when the AI company goes public. The S-1 reveals that Amazon holds convertible notes, a type of debt that turns into stock at an IPO, now valued by Amazon itself at $97.9 billion.

Amazon first invested in Anthropic in 2023, committing up to $4 billion. Rather than taking shares right away, it structured much of that money as convertible notes. As of June 30, those notes carried $6.2 billion in principal, Anthropic’s entire debt load. But Anthropic’s valuation has climbed through several funding rounds, so the shares the notes will convert into are worth far more than the cash Amazon put in.

That gain is big enough that Anthropic had to record it as a cost. The company booked a $72.4 billion charge in the first half of 2026 for the rising value of convertible notes, derivative liabilities, and SAFEs, a kind of early-investor contract. The charge does not represent cash leaving Anthropic. It reflects what the company now owes, on paper, as its valuation rises.

The S-1 caps how much stock Amazon’s notes can become. The notes could convert into as many as 1.84 billion shares, but Amazon is limited to 12% of Anthropic’s “partially diluted” share count, a figure that includes stock not yet issued, such as employee options. Amazon can choose to waive that cap. Notes that cannot convert right away stay outstanding and convert later, under the same limit.

Amazon’s notes are only part of its position. It also put $10 billion into nonvoting preferred stock in the second quarter of 2026, split evenly across Anthropic’s last two funding rounds, according to Amazon’s own quarterly report. Combined with the $8 billion it invested in notes between 2023 and 2025, Amazon’s total investment in Anthropic comes to about $18 billion. Beyond any stock gain, Amazon also stands to collect revenue from Anthropic, which has committed to spend at least $110 billion on Amazon’s cloud unit, AWS, over the next decade.

Venture firms will still do well. Menlo Ventures, Sequoia, Sound Ventures, and Spark Capital are all expected to see billion-dollar returns, but none owns even 5% of Anthropic, the threshold for appearing in the S-1’s table of major stockholders. At Anthropic’s $965 billion private valuation, that is because each percentage point of ownership is worth close to $10 billion. Google holds a larger stake, estimated at around 5.6% by PitchBook analyst Harrison Rolfes after accounting for dilution from recent funding rounds, and has separately secured at least $114 billion in cloud commitments from Anthropic through 2033.

The S-1 itself flags a risk in these arrangements: some of the cloud providers that fund Anthropic, including Amazon and Google, also build competing AI models, and their interests will not always line up with Anthropic’s. What investors will be watching next is whether Amazon exercises its right to waive the 12% conversion cap once Anthropic lists, and how the market prices a company whose largest financial backer is also one of its biggest potential rivals.