Users on X claimed in October 2026 that some Claude Opus 5.5 requests were being sent to an unreleased model, possibly Fable 5.5. Neither the routing nor the model’s identity has been confirmed, and Anthropic has not announced Fable 5.5. A “claude-fable-5-5” catalog entry appeared on October 13, 2026, but its specifications were copied from Fable 5.1 and it was later removed.
A “Mythos 5.5” label appeared in hidden code on Anthropic’s website on November 1, 2026, though the live page listed Mythos 5.1. Some users also reported seeing “gpt-6.2-astra” in Codex usage data that day; OpenAI has not announced that model. Anthropic’s IPO filing leaves its share count and price range blank, and its roadshow cannot start before November 10, 2026.
