Two Customers Account for a Fifth of Anthropic's Revenue, a Concentration Risk IPO Buyers Should Know

Anthropic, one of the world's fastest-growing AI companies, plans to go public by the end of the year. Reports say it is aiming for a $2 trillion valuation. That would make it the biggest initial public offering (IPO) in history and one of the world's most valuable companies.

However, recent leaks from its confidential S-1 filing reveal some serious warning signs. Reports say Anthropic earned $16.3 billion in revenue in the first half of 2026 but recorded a huge net loss of $80.7 billion. Of that loss, $72 billion came from accounting charges that did not involve cash payments. Even so, these numbers raise serious questions about Anthropic's claim that it reached adjusted profitability in the third quarter.

Also, about one-fifth of Anthropic's revenue in the first half of 2026 came from just two customers. Anthropic did not name either company in its S-1 filing, but several industry reports have identified them as SpaceX (NASDAQ: SPCX) and Microsoft (NASDAQ: MSFT). Let's look at why these two companies depend on Anthropic and whether this heavy reliance on just two customers poses a major long-term risk.

Why are SpaceX and Microsoft relying on Anthropic?

SpaceX's AI business bought Cursor, an AI coding start-up, for $60 billion in August. Cursor is a code editor built around AI that lets users access Anthropic's Claude AI models.

Microsoft includes Claude in GitHub Copilot, an AI-powered programming assistant first developed by GitHub and OpenAI. As GitHub added other AI models to its platform, millions of developers began sending their requests through Claude.

Anthropic earns money whenever these platforms use Claude through its API (application programming interface), which lets software communicate with its AI models. As more developers use Claude through Cursor and GitHub Copilot to help them write code faster, Anthropic's revenue will continue to grow.

Is this a major risk for Anthropic?

Claude's coding models, especially Sonnet and Opus, are widely seen as some of the best AI tools for writing complex code. Cursor and GitHub Copilot users can also choose other AI models, including OpenAI's GPT, Alphabet's Google Gemini, and SpaceX/xAI's Grok. Even so, most programmers still use Claude.

But according to Anthropic's S-1 filing, its biggest customers pay to use its models based on how much they use them, without long-term contracts. This means that if competitors catch up and release similar coding models at lower prices, Anthropic's revenue could fall sharply. If competition forces Anthropic to lower its prices, its net losses will likely grow.

Anthropic will likely attract a lot of attention when it finally goes public. But, as with SpaceX, investor excitement could fade once people begin to notice its major weaknesses.

Leo Sun has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Alphabet and Microsoft. The Motley Fool has a disclosure policy.