Anthropic’s Fable series release cadence drives current Polymarket sentiment, with the latest Claude Fable 5.1 model from September 2026 setting expectations for a 5.2 or higher successor soon. Traders price a 97% implied probability of public availability by December 31 and roughly even odds near mid-November, reflecting historical quarterly updates alongside competitive pressure from other large language model labs. No official announcement or API identifier for Fable 5.2+ has surfaced yet, though strong benchmark gains in coding and agentic tasks from 5.1 reinforce momentum. Key upcoming catalysts include potential developer conferences, earnings commentary, or stealth routing signals that could shift the market-implied median release window around November 13.