Anthropic is reportedly SpaceX's biggest customer, behind more than a third of its revenue last quarter. Either side can walk away starting early next year.

Bloomberg reported on Thursday that Anthropic is the unnamed "Customer B" in SpaceX's latest quarterly filing, citing one person familiar with the matter (Bloomberg). Neither company has confirmed it. Anthropic declined to comment and SpaceX didn't respond, according to Bloomberg's report as summarized by The Next Web. What is confirmed is the filing itself. SpaceX's 10-Q for the quarter that ended Sept. 30 says Customer B accounted for 34.5% of its revenue that quarter, and that Customer B's revenue comes from SpaceX's AI division, now called Super Intelligence, which rents out computing power (SpaceX 10-Q, SEC). The same table shows Customer B was under 10% of revenue a year earlier. SpaceX's quarterly revenue was $14.6 billion, so 34.5% works out to roughly $5 billion, by our math from the filing's figures. Customer A, which buys across all three of SpaceX's businesses, was 16.6%. Bloomberg's report says that makes Anthropic a bigger customer than the U.S. government, long SpaceX's main source of income.

Anthropic's own IPO filing lays out the deal. Between May and October, it signed agreements with SpaceX's AI subsidiary to use computing power built on NVIDIA chips, worth up to $120.5 billion over terms running into 2029. That works out to about $3.1 billion a month once all the capacity is delivered, which Anthropic expects in December (Anthropic S-1, SEC). The catch is in the next sentence. After initial locked-in periods ending in January and March 2027, either side can cancel each agreement with 90 days' notice. The same filing describes Anthropic's spending commitment to Amazon as non-cancelable except in narrow cases.

What to weigh: SpaceX's fast-growing AI business now leans heavily on a single customer that, according to its own filing, can leave on three months' notice from early 2027. For Anthropic, the flexibility cuts the other way. It can shift computing work to Google, Amazon, Microsoft and others as cheaper capacity appears. If you use Claude, nothing changes today. This is about who supplies the computers behind it and how much leverage each side has.