Cerebras CEO Andrew Feldman Says Elon Musk Found a 'Pretty Good Idea' in Leasing SpaceXAI's Unused Grok Capacity to Anthropic

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Cerebras Systems Inc. CEO Andrew Feldman says SpaceXAI, formerly xAI, moved into rented AI computing because its processors were not busy enough, as Grok drew less usage than expected.

Feldman Blames Grok's Weak Early Adoption

Speaking with Molly O'Shea on the Sourcery podcast on Monday, Feldman explained that Musk's company pivoted to an operator that rents out AI infrastructure because its Grok model struggled with early enterprise market adoption, leaving billions of dollars in hardware sitting idle.

"You have to ask why they had available capacity," Feldman said. "They had available capacity because the Grok model wasn't used very much."

Cerebras CEO @andrewdfeldman explains why @elonmusk and SpaceXAI made a deal to lease GPUs to Anthropic:

"You have to ask why they had available capacity... They had available capacity because the Grok model wasn't used very much."

"They had these GPUs sitting around, and... https://t.co/1IHsE98NR3 pic.twitter.com/ssomhhLJJl

-- sourcery (@sourceryy) July 13, 2026

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Feldman said SpaceXAI could not afford to leave equipment idle. "They had these GPUs sitting around, and that's a bad idea," he said.

He pointed to IPO-bound Anthropic's agreement to use SpaceX's Colossus 1 data center in Memphis, Tennessee. Anthropic said the site provides more than 300 megawatts through over 220,000 Nvidia GPUs, allowing it to double Claude Code limits, remove peak-hour reductions and raise API ceilings.

"They leased a whole block of them to Anthropic, and looked up and said, 'Whoa, that's a pretty good idea,'" Feldman said. "We had all these GPUs. Our model wasn't a success, but we can have a great business by stepping into what is a constrained market."

Anthropic Deal Monetizes Idle GPU Capacity

In May, Anthropic agreed to pay $1.25 billion per month for Colossus and Colossus II capacity through May 2029. Both sides can terminate with 90 days' notice, and Musk described the arrangement as a six-month lease, leaving its long-term value uncertain.

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Colossus 1 supported Grok's development, but Reuters described its capacity as unused prior to the Anthropic agreement. SpaceXAI said Grok 4.5 trained across tens of thousands of Nvidia GB300 processors.