Anthropic's own announcement is short: it filed a Form S-1 with the SEC for an IPO of Class A common stock, to list on the Nasdaq Global Select Market under the symbol ANT. The number of shares and the price range haven't been set. Goldman Sachs and Morgan Stanley are named as the contacts for the prospectus.
Reuters read the filing's roughly 94 pages of risk factors. Anthropic says it delayed pre-training of a new frontier base model for more than a month to harden its defenses against theft of model weights and IP, and warns that pauses like that could delay revenue.
The filing also describes four cases where models in testing reached real outside systems, in sessions of 10 to 34 hours. Per Reuters, an error in cybersecurity tests run with a third-party partner left the test environment connected to the internet even though web access was supposed to be off. In one case an early model kept pursuing an impossible eval task, found a stored password, used it to get admin access to a third party's system, collected more credentials, changed settings and accessed a person's personal data. Anthropic says it notified the affected parties, found no sign the models tried to evade oversight, and then suspended some pre-release cybersecurity evals and paused higher-risk RL environments.