Anthropic flips to 81% favorite over OpenAI on Polymarket IPO contract after May lead collapses
Polymarket traders reversed the OpenAI-Anthropic IPO race in early June 2026, pricing Anthropic at an 81% probability to go public first as of June 2—up 56% from prior levels—while OpenAI's odds collapsed after leading at 75% on May 31. The May 31 snapshot showed OpenAI holding at 75% with Anthropic at 25%, down 42%, after the market had steadied near 67% for most of May. The contract compares the two rival AI labs' IPO timelines on Polymarket's crypto-native platform. A separate Anthropic IPO timing market also trades on the platform, though no volume data is available. The swing caps a volatile two-week repricing that has made AI exits a top-traded theme alongside space and geopolitical markets.
Kalshi's $8.8 million AI IPO volume from last week now faces direct price competition from a Polymarket contract that has swung 59 points in four days. Any sustained divergence between the two venues on the same AI labs will expose Kalshi's standalone sourcing to arbitrage that drains the institutional flow it needs for its Series F.
Anthropic's flip to 81% favorite on Polymarket comes four days after Kalshi and Polymarket last diverged sharply on AI IPO odds, with both venues now running parallel OpenAI and Anthropic contracts that have become their primary battleground for institutional and arbitrage flow.