If not for the intense rivalry between Anthropic and OpenAI, the generative AI boom might not have arrived so quickly.
In late 2022, OpenAI caught wind that Anthropic was working on an AI-powered chatbot. OpenAI CEO Sam Altman immediately directed employees to fast-track a competing product, four people familiar with the matter said. Two weeks later, the company released ChatGPT, sparking a technological revolution that promises to overhaul the global economy and the way humans interact.
The same urgency now extends to plans for their blockbuster IPOs.
The companies are racing to beat one another to market, viewing a first listing as a way to frame how investors will value the companies and establish their CEO as the leading voice of AI.
As recently as May, many advisers expected OpenAI would be first to take the initial steps to go public. OpenAI has told some investors it was targeting an IPO as early as September, two people familiar with the matter said.
But Anthropic jumped in first, announcing on June 1 it had made a confidential filing with U.S. regulators. OpenAI followed on Monday, a week later.
The stakes extend beyond the clash between Altman and Anthropic CEO Dario Amodei, a former researcher at OpenAI, where he was one of the people responsible for the core technology that made ChatGPT possible.
The competition is spilling into Wall Street. It’s rare for two such big direct rivals to raise capital at the same time, and the IPOs will be so big that they are by necessity turning to some of the same banks for help. OpenAI is looking to go public at a valuation around $1 trillion, Reuters previously reported.
Bankers and other advisers are navigating increasingly complex relationships with both OpenAI and Anthropic, three people familiar with the matter said. Executives at both companies have pressed their IPO advisers for insight into the rival’s plans, the people said, prompting some banks working with both companies to erect internal barriers between deal teams to prevent information leaks.
‘All-out war’
Top bosses often clash. Elon Musk and Jeff Bezos have traded public barbs as part of their space race, and Bill Gates and Steve Jobs quarreled over whether Microsoft products had copied from Apple.
The tension between Altman and Amodei is the driving force in today’s biggest technological revolution – influencing how quickly AI tools are released, what features they include and, ultimately, how people interact with the technology in their daily lives.
"It’s all-out war between these guys," said Anastasios Angelopoulos, CEO of Arena, a top AI benchmarking and evaluation company. "Every time there’s a new release from Anthropic, the bet will be that OpenAI is soon to follow and vice versa."
Both companies declined to comment on the CEO rivalry.
Fight over revenue recognition
The companies are also at odds over how each tells its financial story to investors.
OpenAI has told investors and employees that Anthropic’s preferred accounting method overstates its revenue by billions of dollars, according to two people familiar with the matter. In April, OpenAI's chief revenue officer Denise Dresser told employees that OpenAI considers Anthropic’s financials inflated, according to a company memo reviewed by Reuters.
That’s because Anthropic books the full amount that customers pay for its AI services as revenue, but part of that sum is later routed to partners such as Amazon and Google. OpenAI uses a different method, reporting only net revenue after paying its partner, Microsoft.
Anthropic told Reuters that it follows established accounting practices and recognizes gross revenue because it is the “principal” in the transaction while its cloud partners are distribution channels.
Dresser’s internal communications aimed to reassure OpenAI staffers who have been demoralized by Anthropic’s rapid growth, two of the people Reuters spoke to said.
One reason for "Anthropic to try to beat OpenAI out to the public market is that they will get to set the agenda for how a frontier model reports financials and do so in a way that is favorable to their financial model,” said Gil Luria, analyst at D. A. Davidson.
The desire to best its rival has, at times, led to tensions within OpenAI.
Altman recently clashed with Chief Financial Officer Sarah Friar over whether the company could meet the obligations required for a public listing on such a compressed timeline, three people familiar with the matter said. Altman told her to figure it out or hire different bankers and lawyers who could pull it off, they said.
Friar has since told advisers that the company’s leadership is aligned on timing, another person said.
In an interview on CNBC after Anthropic’s filing, Altman said he didn't want to rush OpenAI’s debut.
A long-running feud
The rivalry dates back to late 2020, when Amodei left his job as OpenAI's vice president of research with several others to create Anthropic, which promised to prioritize safety. The move was seen by many OpenAI employees as a rebuke of Altman’s approach.
In early 2022, Anthropic trained the first version of its chatbot Claude, but held it back from public deployment to conduct safety research instead, Anthropic later said.
OpenAI had similar projects underway. Some employees were working on a "super-assistant" tool powered by OpenAI's then-advanced models, four people familiar with the matter said. Meanwhile, co-founder John Schulman was separately working on a chat interface. Schulman didn’t respond to a request for comment.
At one point, OpenAI officials considered launching the chat-based assistant tool in March 2023, alongside the release of its GPT-4 large language model, the four people said.
But rumors of Anthropic’s project in mid-November galvanized Altman. He directed OpenAI staffers to develop a chatbot that could be ready as quickly as possible. “All of a sudden, it was like, we got to ship this in two weeks,” one of the people said.
The product, ChatGPT, was released on November 30, 2022. It quickly became the fastest-growing consumer application in history, drawing millions of users and upending tech giants’ previous product roadmaps.
Anthropic, which launched its Claude chatbot a few months later, spent about three years catching up to OpenAI. Around late 2024, Amodei redirected researchers to focus on so-called reasoning models after seeing OpenAI’s early success there, three people familiar with the matter said.
The dynamic flipped in late 2025 when Anthropic, which long focused on business customers, released a powerful update to its Claude Code tool. OpenAI, which generates much of its revenue from consumers paying for ChatGPT, has now redoubled its focus on enterprise software and pulled more resources into its own coding product, Codex.
Open distaste
Relations between the two companies deteriorated after Altman was unexpectedly fired by OpenAI’s board in late 2023.
As the board cast about for options, directors briefly spoke with Amodei about merging the two labs under his leadership. In a recent deposition, one former OpenAI executive said the idea was considered “extremely briefly” before the board moved on to other ideas.
Even so, news of the proposal infuriated many OpenAI employees, three people familiar with the events said. Altman was reinstated within days, but that anger persisted.
The feud is becoming increasingly public. In February, Altman slammed Anthropic’s Super Bowl ads as “deceptive” for misrepresenting OpenAI’s plans to sell ads on ChatGPT. In March, Amodei accused Altman of leveraging Anthropic’s dispute with the Pentagon to help OpenAI.
At an AI summit in India in February, Prime Minister Narendra Modi encouraged all the tech executives on stage to join hands in a show of unity.
In a moment captured in a viral video from the summit, Altman and Amodei, standing next to one another, refused.
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