The chances of Anthropic announcing an initial public offering before November rose to 16% Wednesday afternoon from 4.7% on Sept. 28, based on Kalshi trading. Traders put the odds above 60% for an IPO announcement before December and close to 80% for the offering to happen before January. Anthropic confidentially filed its IPO prospectus in June and warned investors that its models pose a "catastrophic or existential risk to humanity," Reuters reported.