Users on X report that Anthropic is testing unreleased versions of its models, specifically Fable 5.5 and Mythos 5.5. Evidence includes hidden website labels, catalog entries in LiteLLM, and Azure cloud listings, though these references were subsequently removed.
Fable 5.5 is described as a successor to Fable 5.1, which was released on September 1. Mythos 5.5 is identified as a restricted version of the same model, intended for cybersecurity and biology researchers. Anthropic previously released Fable 5 on June 9 and Opus 5.5 on September 22.
OpenAI is reportedly conducting A/B testing for a model identified as GPT-6.2 Astra. Users noted this version appearing in Codex usage analytics alongside the existing GPT-6 Astra, which was released on September 3. OpenAI has not issued an official announcement regarding this model.
Anthropic filed for an IPO on October 26, with Goldman Sachs and Morgan Stanley listed as underwriters. The company reported revenue of $16.29 billion for the first half of 2026, compared to $1.16 billion in the same period of 2025. The earliest possible date for the investor roadshow is November 10.
