Anthropic SpaceX Customer B is the mystery account that powered more than a third of SpaceX’s revenue last quarter. Bloomberg reported Thursday, citing people familiar with the matter, that the “Customer B” listed in SpaceX’s latest quarterly filing is Anthropic PBC, making the AI startup the rocket company’s largest single customer and pushing past the US federal government in spending.

What Was Announced?

SpaceX’s third-quarter 10-Q identified an unnamed buyer of computing services from its AI division, now called Super Intelligence, as the source of 34.5% of the company’s revenue. Deutsche Bank analyst Edison Yu calculated that the customer paid about $1.7 billion a month, according to Barron’s analysis of the filing.

Bloomberg’s sources said that customer is Anthropic, which rents GPU capacity at SpaceX’s data centers in Memphis, Tennessee, home to the Colossus I supercomputer and the Colossus II expansion. SpaceX did not respond to a request to confirm the identity, and Anthropic’s name appears nowhere in the filing, but the terms line up exactly with the compute agreements Anthropic disclosed in its own S-1: an aggregate commitment of up to $120.5 billion with SpaceX’s AI unit, with terms running into 2029.

Anthropic SpaceX Customer B fact card: 34.5% of Q3 revenue, $1.7B a month

Graphic: GPTOnline

How the Deal Fits Together

The arrangement is limited-term and the spending is still ramping. Under the terms Anthropic disclosed, the computing agreements reach full run rate in December, when the startup will owe about $3.1 billion a month, and either side can terminate the contracts with 90 days’ notice once the initial periods end in January and March 2027.

The escalation surprised even the analysts who track the stock. Yu wrote that Deutsche Bank’s initial modeling assumed the customer had only contracted for $1.25 billion a month and would not upsize until the first quarter of 2027: “However, it seems the renewal occurred earlier, and SpaceX is selling more compute to Customer B than expected and/or charging a higher rate beyond the original $31 per watt, once again illustrating how compute-constrained the market is and the benefits of selling on the spot market.”

That $120.5 billion ceiling, from Anthropic’s S-1 filed October 26, is itself a new figure: roughly $36 billion higher than the $84.5 billion reported from the confidential version of the prospectus, and it sits inside Anthropic’s roughly $417 billion in total compute commitments.

Why It Matters

Two numbers from the filing explain why Musk’s “neocloud” pivot is suddenly the center of the story. SpaceX’s AI division turned a profit for the first time this quarter, and a single data center costing about $50 billion is now “tracking at eight to nine months” for payback at spot pricing, Yu wrote. Chief Financial Officer Bret Johnsen told analysts on the earnings call that demand for computing power is running ahead of supply.

The filings also show the scale of the buildout behind those numbers: long-term assets of roughly $100 billion excluding goodwill, up about 100% year over year, including $43 billion in servers and networking equipment and $24 billion in construction in progress. Yu estimates the AI rental business could reach $200 billion in annual recurring revenue by 2027. Anthropic is far from the only buyer, with a second customer at 16.6% of revenue and deals spanning Nscale and Lambda, but the filing makes clear that one startup’s compute bill has become the load-bearing wall of SpaceX’s growth story.

SpaceX neocloud economics fact card: $7.56B AI revenue, 8-9 month payback

Graphic: GPTOnline

Sources