Yes, it’s finally happened. A “Mythos-class” Claude model has arrived for the general public. But it’s not the same “too-dangerous-for-you” Mythos you’ve been hearing about, and Claude subscription users will only get a limited crack at it.
Claude Fable 5 is now available in the Claude desktop app, and the new model is so powerful that it has “the potential to do profound good for the world,” Anthropic said in a press release.
At the same time, Fable 5’s extreme cybersecurity capabilities “could be misused to cause serious damage,” Anthropic warns. That’s why the model arrives with conservative safeguards that may “sometimes catch harmless requests.” (Anthropic pegs the frequency of over-cautious denials at less than 5 percent of sessions.)
Anthropic is also releasing Claude Mythos 5, based on the same underlying model as Fable 5 but with safeguards lifted in some areas, for a “small group of cyberdefenders and infrastructure providers.”
Anthropic has released benchmarks for Fable 5 that promise substantial improvements in coding, spatial reasoning, and other areas over previous models. But the biggest leaps come in cybersecurity, which was what all the fuss was about when news of Claude Mythos first broke.
There’s good news and bad news when it comes to Fable 5 access for paid Claude users. The good news is that those of us who are subscribers (versus API users who pay by the token) can use Fable 5 right now, and that includes Claude Pro, Max, Team, and seat-based Enterprise users. The bad news? Anthropic will yank Fable 5 from Claude plans on June 23rd. After that, you’ll need paid usage credits to access Fable 5. (Credits are pre-paid and charged at the same rate as API usage.)
Anthropic says it “aim[s] to restore Fable 5 as a standard part of subscription plans … as soon as possible” but only “when sufficient capacity allows us to do so.”
In the meantime, those on paid Claude plans can kick the tires on Fable 5, but expect your usage meters to drain dramatically faster than they do with Claude Opus 4.8, the next-most-powerful Claude model.
For my part, I tried using Fable 5 with Claude Code but was almost immediately kicked off, with a vague error message saying there was an “issue with this model.” Hmm.
