**Anthropic’s Claude Fable line has followed a rapid cadence, with Fable 5 launching in June 2026 and Fable 5.1 arriving September 1, prompting traders to price a 5.2+ successor imminently.** Recent leaks point to a fresh pretraining run targeting late September or early October, while multiple reports of Fable 5.1 routing to an unreleased model in Claude Code have reinforced expectations of near-term availability. No official announcement, model card, or API identifier has appeared yet, leaving the exact timing dependent on internal testing completion, competitive positioning against OpenAI and Google updates, and any regulatory considerations. The tight clustering of Polymarket odds around October 8–13 reflects uncertainty over whether Anthropic will confirm the release this week or slip slightly later, with trader consensus treating the next 7–10 days as the primary decision window.