Adds analyst comments, data on IPO market, company and industry background, paragraphs 4, 7-8, 12, 14 and 18-19

By Manya Saini and Echo Wang

June 1 (Reuters) - AI giant Anthropic has confidentially filed for a U.S. initial public offering, the company said on Monday, taking an early lead over rival OpenAI in a race that will define the future business shape of artificial intelligence.

The move sets up a high-stakes test of whether investor appetite for the AI revolution that has reshaped white-collar work around the world can match the sky-high expectations surrounding the booming sector.

Anthropic, which makes agentic coding assistant Claude Code, did not disclose the size or the terms of the offering. It last raised $65 billion at a post-money valuation of $965 billion in late May, putting it ahead of OpenAI.

Confidential submissions let companies advance IPO preparations while shielding sensitive financial details from rivals and the public.

The crucial step toward a listing comes on the heels of SpaceX's mega-IPO, which is on course to rewrite the record books as the Elon Musk-led company pursues a $75 billion offering at a $1.75 trillion valuation and could begin trading within two weeks.

AI BOOM

OpenAI and Anthropic have become the face of the AI boom that has redrawn corporate strategies, sparked a global arms race for computing power and talent, and turned AI-linked companies into some of the market's most richly valued firms.

"OpenAI and Anthropic are in a race to go public before capital runs out," D.A. Davidson analyst Gil Luria said.

"The other 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."

OpenAI is also preparing to confidentially file for a U.S. IPO in the coming weeks, a source ​familiar with the matter told Reuters in late May, adding to a wave of blockbuster ‌listings anticipated in the year ahead.

Anthropic's valuation has more ​than doubled from $380 billion in February, when it raised $30 billion in a funding round.

The company's rapid rise in early 2026 rattled markets, triggering sharp selloffs in software and IT stocks as investors worried its increasingly autonomous AI tools could upend traditional business models and accelerate disruption across industries.

Its latest funding round drew backing from a mix of Silicon Valley and Wall Street investors, including Blackstone, Brookfield, D1 Capital Partners, GIC, General Catalyst and Insight Partners.

A MARKET MILESTONE

As a slew of blockbuster listings races toward public markets, companies from SpaceX to AI giants are competing for a finite pool of investor capital.

"The combined demand for capital from SpaceX, OpenAI and Anthropic will be so considerable that it is likely to create disruptions in the capital markets, so going early will be a great advantage," Luria said.

The listing would represent one of the most consequential stock market debuts in years, potentially reshaping benchmark indexes, investor flows and the broader narrative driving U.S. equities.

At a valuation of close to $1 trillion, Anthropic would vault to the top tier of the S&P 500, alongside a handful of elite companies that dominate global equity markets.

An Anthropic debut would be a major boost for the long-sluggish IPO market, though experts and bankers warn an offering of such scale could drain liquidity and investor attention from smaller listings.

Still, the U.S. IPO market has regained momentum in recent weeks, with companies raising $87.5 billion through May 26, the highest year-to-date total since 2021, according to Dealogic data.

Several sizable IPOs are also set to hit the market later this week, including Honeywell-backed quantum computing firm Quantinuum, Blackstone-backed Liftoff and gas engine manufacturer Innio.