As of May 21, 2026, based on public information and market dynamics, and considering the two companies’ IPO progress, legal obstacles, business models, and market expectations, OpenAI is more likely to list ahead of Anthropic.

OpenAI’s most likely IPO timing window is September 2026, while Anthropic is expected in October or in the fourth quarter—about a one-month gap—so the suspense could be resolved in the short term.

🏃 OpenAI: Ramping up to catch up and seize the early advantage

· Firm commitment to an IPO and clear objectives: OpenAI plans to complete its IPO as early as September 2026, targeting a valuation of over $1 trillion.
· Rapid real progress: It is expected to confidentially submit its IPO application to the SEC as early as May 22 (this Friday), earlier than Anthropic.
· Major legal hurdles have been cleared: A key lawsuit in which Musk accused OpenAI of deviating from its “non-profit” founding mission was dismissed by the court on May 19, clearing a major legal obstacle on the road to going public.
· Market expectations have shifted sharply: Forecasts show the probability of OpenAI being the first to go public on Kalshi has surged to 83%; on Polymarket, the probability of Anthropic going first has crashed from 69% to 20%.

🐌 Anthropic: The advantage remains, but the pace is relatively slower

· A slightly later schedule: Public reports indicate its IPO could be as early as October 2026.
· Strong enterprise positioning: In 2026 Q1, it held a 31.4% share of the global LLM market, ranking first—slightly above OpenAI’s 29%—and its revenue may already have surpassed its longtime rival.
· Lower recent IPO probability forecasts: Market confidence in Anthropic going public first has wavered, with the probability dropping sharply from 69%.

Any IPO plans are subject to uncertainties, but based on the current information, OpenAI has already gained the upper hand in the race to become the “AI first stock.”