Update — August 10, 2026: DHH reported that Fable used an 11-million-token single session to port all 37 TerminalTextEffects animations from Python to Rust. Read what the 87ms→2ms benchmark proves—and what the clean one-shot case does not.
Update — July 20, 2026: Viral X thread claimed Fable/Mythos ~10T parameters — unverified; Anthropic never discloses counts. Parameter debate + Musk ratios →
Update — July 7, 2026: Fable leaves included subscription plans after 11:59:59pm PT; Anthropic aims to restore when capacity allows. Subscription billing guide →
Update — August 16, 2026: Anthropic's Risk Report disclosed an unreleased successor, Model 2, that beats Mythos 5 on internal benchmarks but is being held back pending full safety testing — see Anthropic's Model 2: Built, Beats Mythos 5, Not Being Released.
Update — September 2, 2026: Anthropic shipped the successor — Claude Fable 5.1 and Mythos 5.1, with doubled science benchmarks, 75%-cheaper cache reads, and Enterprise Frontier Safeguards. Usage limits were reset for all users at launch.
Related on explainx.ai
- Claude Fable 5.1 and Mythos 5.1: benchmarks, pricing, safeguards
- Anthropic's Model 2: Built, Beats Mythos 5, Not Being Released
- DHH's Fable one-shot Python→Rust rewrite — 11M tokens, 87ms→2ms
- Is Fable 5 available in Claude Code?
- Fable 5 subscription billing and return timeline
- Fable 5 international availability outside the US
- Fable 5 UK availability guide
- Fable 5 community projects from launch week