Anthropic releases Claude Fable 5, putting a Mythos-class model in everyone's hands

Anthropic released Claude Fable 5 on June 9 — the first Mythos-class model the general public can actually use. Under the hood, Fable 5 and the tightly restricted Claude Mythos 5 are the same model. The difference is the wrapper: Fable ships with safety classifiers that detect and block requests in high-risk areas like offensive cybersecurity and biology, falling back to Claude Opus 4.8 for a safe answer instead. Anthropic says the classifiers trigger in less than 5% of sessions.

The performance claims are aggressive. Fable 5 scores more than 10% above Opus 4.8 — a model Anthropic shipped just weeks earlier — on several benchmarks, and posts state-of-the-art results on FrontierCode and Hebbia's Finance Benchmark. Early customer reports back this up: Stripe says Fable 5 compressed months of engineering work into days on a 50-million-line codebase, and analytics platform Hex measured 90% on its hardest analytical tasks. In one demo that circulated widely, the model completed Pokémon FireRed using nothing but raw screenshots as input.

The release comes days after Anthropic publicly urged rival labs to adopt "coordinated brakes" on frontier development, warning that AI systems may soon be capable of recursive self-improvement. That tension is visible in the launch design. Fable 5 endured over 1,000 hours of external bug-bounty testing without a universal jailbreak, and all Mythos-class traffic now carries a mandatory 30-day data-retention policy for safety review — even for enterprise customers who previously had zero-retention agreements.

The unrestricted Mythos 5 stays locked behind Project Glasswing, Anthropic's cybersecurity collaboration with the US government, with a vetted-access program for biology researchers coming next. In the life sciences, Anthropic says Mythos 5 produced novel molecular-biology hypotheses that scientists preferred about 80% of the time in blind comparisons, and accelerated protein-design work roughly tenfold.

Pricing is steep: $10 per million input tokens and $50 per million output — double Opus 4.8. The catch worth knowing: Fable 5 is included at no extra cost on Pro, Max, Team, and Enterprise plans only until June 22. From June 23 it requires usage credits, until capacity catches up with demand.

Sources: Anthropic, TechCrunch, CNBC.