Anthropic’s new Claude Fable 5 puts powerful cyber tools behind safety filters. DeFi, already hit by more than $840 million in hacks this year, is one of the industries with the most to lose if the filters fail.
The newest AI model from Anthropic, which gives users access to stronger, faster reasoning and coding capabilities, lands in a crypto market beset by security problems and could well exacerbate them.
The company released Claude Fable 5 on Tuesday, the first public model in the Mythos class and, Anthropic says, its most powerful yet. So powerful, in fact, the company released two versions: one for widespread use and the other for more restricted distribution.
The public version sports stronger reasoning and coding ability while blocking the most dangerous uses. A less-hamstrung counterpart, Claude Mythos 5, is available only to vetted users in cybersecurity and critical infrastructure.
Experts say Mythos can find and chain zero-day vulnerabilities, or previously unknown software flaws, and help turn a bug into a working attack. Anthropic says the software tries to intercept possible attack vectors by detecting high-risk requests. Once identified, they are routed to a weaker model, Claude Opus 4.8.
The company says this specific fallback triggers in fewer than 5% of sessions. It also said in a blog post that specialized cybersecurity teams and more than 1,000 hours of external bug-bounty work found no universal way of breaking the system.
Still, Anthropic recognizes that the system is unlikely to be foolproof and says it expects determined, well-funded attackers to keep trying because the capability is valuable.
“The uplift from Mythos-level capabilities is valuable to many adversaries—for instance, those who could financially gain from cyberattacks—and we therefore expect them to be motivated to try to circumvent our safety measures,” the firm said in the post.
Hellbound and Down 