Anthropic opens the doors of Claude Fable 5 to the public
Anthropic took a bold step and launched Claude Fable 5 on June 9, 2026. This is the first model of the Mythos class that anyone can access. Until then, this technology was kept under lock and key, available only to organizations within the Project Glasswing cybersecurity program, which began in April 2026. The company guarantees that Fable 5 outperforms any other system it has widely released. But, and here is the catch, they are selling a cutting-edge model whose unrestricted version was considered too dangerous to be let loose. Anthropic's solution was to architect a protection system. If a query is deemed risky, it is redirected to Claude 4.8 Opus, an earlier model. For those working with it, the new release comes with a price and a condition: data from all Mythos-class traffic must be stored for 30 days.
Claude Fable 5 is not just a pretty face. It shares the structure of Claude Mythos 5, but with a differentiator: classifiers that filter queries in areas like cybersecurity and chemistry. If the filter triggers, the response is generated by Claude 4.8 Opus. According to Anthropic, more than 95% of sessions pass without triggering this mechanism. They admit the safeguards are “stricter than ideal” and that sometimes harmless queries end up redirected. An external bug bounty program found no universal vulnerabilities in over a thousand hours of testing, but the UK AI Safety Institute came close to a jailbreak in initial evaluations. This explains why the unrestricted version remains closed. Mythos 5 remains exclusive to Project Glasswing partners, who have had early access since April 2026.
In terms of performance, Claude Fable 5 shines in areas like software engineering and computer vision. Stripe, which tested the model, reported it managed to compress months of work into days. In one case, it migrated 50 million lines of Ruby code in a single day, something that would take a team over two months. The model also beat Pokémon FireRed using only a minimal set of vision-based tools, something previous versions failed to do. On financial reasoning benchmarks, Fable 5 broke records among tested models, according to Anthropic. But, it is worth remembering, this information comes from the company itself and partners, so it's good to be skeptical until independent evaluations are published.
The cost of Fable 5 and Mythos 5 is $10 per million input tokens and $50 per million output tokens. Subscribers to Pro, Max, Team, and Enterprise plans can use Fable 5 at no additional cost until June 22, 2026. After that, usage starts consuming credits. The trade-off for this access is mandatory data retention for 30 days, which may require a legal assessment for Brazilian companies under the LGPD.
Mythos 5, without cybersecurity restrictions, is available to current Glasswing partners. Anthropic is planning a broader access program in consultation with the US government. A separate track focused on biology will include researchers who need unrestricted capabilities. Journalist Alex Heath had already anticipated the launch on June 7, 2026, mentioning that Anthropic was preparing “a public version of Mythos” with “substantial safeguards.” Confirmation of plans to expand trusted access is the next milestone to watch. This will define whether the Mythos class becomes a market product or remains a controlled asset. The timeline for expanded access to Mythos 5 will tell how far this class can go.
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