'Big Short' investor Steve Eisman sees an Achilles' heel in the AI boom

Steve Eisman is warning that the artificial intelligence boom has become increasingly dependent on the fortunes of just two companies: OpenAI and Anthropic.

The investor, best known for his bet against the housing market ahead of the global financial crisis, said the two AI startups account for roughly 70% of AI-related revenue at Microsoft , Amazon , Alphabet 's Google and Oracle — and as much as 25% to 35% of their cloud revenue.

"The futures of these massive companies, in a sense, are a bet that OpenAI, Anthropic are going to succeed," Eisman said late Tuesday on CNBC's "Fast Money."

"The Real Eisman Playbook" podcast host and former Neuberger Berman senior portfolio manager believes that the biggest revenue threat could come from China, as Chinese open-source AI models are significantly cheaper and appear to be gaining market share.

"The Achilles' heel of this whole story ... is if something bad happens to Anthropic and OpenAI ... the Chinese open-end models, open-weight models are much cheaper. And if they start really taking a lot of market share and it sounds like, from what I'm hearing, that they're starting to, you could have a big price war. And then we have a problem," he said

Eisman's warning adds another prominent voice to a growing debate over whether the extraordinary spending behind the AI boom can generate sufficient returns.

Michael Burry, another investor whose wager against the housing bubble was chronicled in "The Big Short," has taken an even more bearish view. Burry has questioned whether much of current and future AI demand ultimately comes from end customers, arguing instead that a significant portion is financed through what he has described as circular arrangements.

Burry is putting his money where his mouth is, placing bearish bets against some of the biggest beneficiaries of the AI boom, including Nvidia , and others that are positioned against the broader semiconductor sector.