Anthropic is compounding, OpenAI is flatlining, and the betting markets have noticed

Two of the biggest listings in market history are queued up for the back end of this year, and punters are already pricing the run-in. Polymarket has opened books on where OpenAI (Unlisted:OPAI) and Anthropic (Unlisted (US):ANTHRO) private valuations land at the end of August, settled on the price reported by Nasdaq Private Market. The contrast between the two is the interesting bit. OpenAI 's market is tightly clustered and reasonably well traded, with 54% on a valuation of $800 billion to $900 billion, and a further 23% on $900 billion to $1 trillion. That is basically a bet on nothing happening, since OpenAI was last marked at $852 billion in March and has sat there ever since. A related market gives it a 57% chance of touching $900 billion by 31 August. Anthropic 's book, by comparison, is barely trading, with most brackets showing no volume at all and prices that do not add up to a coherent picture. But the adjacent markets are revealing. Traders put a 65% probability on Anthropic hitting $1.175 trillion by month-end, and 67% say it will show greater valuation growth than OpenAI. That is quite a call on a company that was worth $380 billion in February. Anthropic raised $65 billion in May at $965 billion, overtaking OpenAI for the first time, and filed its confidential paperwork on 1 June, a week ahead of its rival. Annualised revenue went from about $9 billion at the end of 2025 to more than $44 billion by May, roughly 80% of it from enterprise customers. Its second quarter is expected to be the first profitable one, though the company has been careful to point out that a ramp-up discount on its compute deal with SpaceX flatters the number. OpenAI, meanwhile, is do...