On June 9 Anthropic officially released Claude Fable 5 — the first Mythos-class model to be opened to the public. Unlike the strictly gated Mythos 5, Fable 5 takes an "automatic degradation" path: the model itself is unchanged, but on high-risk topics (cybersecurity, biology, chemistry, model distillation, etc.) it automatically falls back to Claude Opus 4.8 to answer. Anthropic says this safety mechanism triggers on fewer than 5% of sessions on average, holding both the capability ceiling and the compliance floor.
In capability, Fable 5 hits SOTA across software engineering, knowledge work, vision, and long-horizon autonomous tasks. Stripe's internal test shows it completed a codebase-level migration across 50 million lines of Ruby code — work that would have taken a traditional team two months. On Cognition's FrontierCode benchmark, it remains the highest-scoring frontier model at moderate reasoning intensity. On Hebbia's financial benchmark, it takes first place in document reasoning, chart analysis, and problem solving.
On pricing, Fable 5 matches Mythos 5: $10 per million input tokens, $50 per million output, half the price of Mythos Preview. Subscribers can use it free on Pro/Max/Team/Enterprise plans from June 9 to June 22, then it switches to usage-based billing.
The more noteworthy thing is actually the "routed safety" paradigm: no longer relying on refusal, no longer relying on non-release, but tying a strong model and a low-risk model into a routing layer, so most users don't feel the difference. If this approach stabilizes, Anthropic has set a template for the entire industry on "how to safely launch a strong model."