AI giant Anthropic has said it plans to become a public company in the US.

The company behind the popular chatbot Claude said on Monday that it had filed confidential paperwork with the US Securities and Exchange Commission to make an initial public offering (IPO) this year.

Once public, people will be able to buy and trade shares in the firm on the stock market, though the company said the price and number of shares to be offered "have not yet been set".

Anthropic's stock market plans, coming alongside those of Elon Musk's SpaceX, will likely function as a test of whether investor appetite matches the soaring valuations of AI firms.

Anthropic, founded just five years ago by chief executive Dario Amodei and a handful of other executives, recently raised money from private investors, valuing the company at more than $965bn (£717bn).

While based on an assumption of future growth, that valuation put Anthropic ahead of OpenAI, which most recently was valued by private investors at $852bn.

Chief executive Dario Amodei founded Anthropic after working several years at OpenAI, a company he left after disagreements with its chief executive, Sam Altman.

The two firms have since become fierce rivals in the AI world, developing similar technology and competing for users' attention and spending and corporate customers' budgets.

OpenAI is also reportedly considering going public this year.

Altman told CNBC on Monday that while his company did intend to go public, it was in no rush to do so.

"We'll do it when it makes sense," Altman said.

Should OpenAI's listing come to pass, the US capital markets are poised to see an historic level of investment in just a handful of companies.

SpaceX alone is expected to break stock market records with its target valuation, but the potential value of Anthropic and OpenAI are not far behind.

Listing will be 'yardstick for investors'

"Neither Anthropic nor OpenAI wants to be the last major AI pure-play to list," Troy Hooper, a leader of equity capital markets at Mergermarket, said.

"The first mover has a real chance to define how public markets value generative AI, setting up the yardstick that investors will use to measure everyone else."

Harrison Rolfes, a research analyst at PitchBook, added that Anthropic's IPO "will be the most scrutinised public offering in tech history", with investors poring over its business margins, sales, and profitability for signs that AI valuations and costs make financial sense.

Given the proximity of SpaceX's upcoming stock market debut, Rolfes said the two companies "represent the largest concentration of pre-IPO capital ever brought to market simultaneously".

"The 2026 window either becomes the most consequential IPO cycle since the dot-com era or the most expensive lesson in narrative-versus-fundamentals that public markets have ever taught," Rolfes said.

Anthropic has been fighting this year, too, with the US Department of Defence (DoD).

After the DoD, late last year, insisted that Anthropic accept contractual terms as part of a $200m deal stating that government agencies could use AI tools like Claude for "any lawful use", Amodei made his concerns public.

Although Claude was the first modern AI chatbot and model to be deployed on US government networks that were classified, the new contract language suggested to Anthropic the possibility that its AI could be used for mass domestic surveillance or on fully autonomous weapons of war.

President Donald Trump denounced the company, and Defence Secretary Pete Hegseth quickly prohibited any US agency from using Claude.

Anthropic subsequently launched legal action against the government. Although there are recent signs from the White House that tensions with Anthropic have cooled, the lawsuit is ongoing.

Such acrimony has not scared off other Anthropic customers.

The company has told investors that it expects to turn a profit in the first half of this year, as sales of its Claude product and related services have grown significantly.

Neither SpaceX nor OpenAI are currently profitable.