Anthropic spent months saying Mythos was too dangerous to release — then it launched a public version called Fable 5 that it warns ‘comes with risks’ | Tech Radar
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Anthropic spent months saying Mythos was too dangerous to release — then it launched a public version called Fable 5 that it warns ‘comes with risks’
Anthropic says Fable 5 brings Mythos-class AI to ordinary Claude users — but only after the addition of extensive safety controls.
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For the last couple of months, Anthropic's most powerful AI model existed largely as a warning about the dangers of AI. The company refused to release it publicly, and repeatedly described its Mythos-class systems as capable enough to trigger serious concerns about cybersecurity, biological research (think nasty pathogens) and the accelerating pace of AI development.
The message was clear: this was technology that required extraordinary safeguards before it could be released.
Now Anthropic has done something surprising. It has launched a public version of that same technology, on Claude's higher-tier subscription plans, if only for a limited period.
The new Claude Fable 5 is a consumer-facing version of the Mythos-class capabilities that Anthropic previously kept behind closed doors. While the company says it has added extensive guardrails and safety measures, the release marks a significant change from Anthropic. Technology it once considered too capable for general availability is now being placed in the hands of ordinary Claude users.
According to Anthropic, Fable 5 is built for much more than what you might be using AI for right now, like answering questions or helping you draft an email. The company says it's designed to handle the kind of work that unfolds over hours, days, or even longer, so we're talking everything from software engineering projects and in-depth research to complex AI agent workflows.
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The big idea is that Fable 5 can stick with a task for far longer than previous models. Rather than responding to a single prompt and waiting for the next instruction, it's supposed to be able to work through multi-step problems, keep track of context across lengthy projects, and make progress with a greater degree of autonomy.
You can use Fable 5 through the Claude chatbot, but many of its biggest improvements seem aimed at power users, researchers, and developers. The goal appears to be moving AI beyond a conversational assistant and closer to something that feels like a genuine digital collaborator.
Much of the concern surrounding Mythos relates to cybersecurity, with Anthropic claiming the model has "the strongest cybersecurity capabilities of any model in the world." While those capabilities could help security researchers identify and fix vulnerabilities, they could also be used to discover and exploit the same software vulnerabilities if placed in the wrong hands.
Anthropic acknowledges that “releasing a model this capable comes with risks”, and it's attempting to address that risk through a unique set of safeguards. The model is paired with separate AI systems known as ‘classifiers’ that monitor requests for signs of misuse. When those classifiers detect a request related to advanced cybersecurity activity, the response is handled by Claude Opus 4.8 instead of Fable 5, thus reducing the risk.
In effect, Anthropic is allowing public access to Mythos-class capabilities while placing some of the most sensitive areas behind an additional layer of protection. That sounds great — so long as it works.
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Initial user reaction has been positive, although users have noted how quickly Fable 5 burns through tokens.
“Fable 5 is insanely good but watch your usage, I was burning 2% a minute on 20x”, said one Reddit user, who also notes: “I'm on the Max 20x plan and during a heavier session I was watching my usage tick up roughly 2% per minute. Not per hour. Per minute. “
Another user takes issue with Fable 5 refusing to deal with cybersecurity calling it a “preview of AI inequality”, noting that “the public gets the 'safe' version. Trusted institutions get the dangerous/useful version.”
If you'd like to use Fable 5 there are a few quirks to its availability that are worth knowing about.
From today, Fable 5 is available on Claude Pro, Max, Team, and seat-based Enterprise plans at no additional cost. However, Anthropic says that from June 23, access will temporarily move to a usage-credit system.
That means subscribers who want to continue using Fable 5 beyond that date may need to purchase additional usage credits depending on how heavily they use the model.
Anthropic says the change is intended to manage demand, rather than create a permanent paywall. "After this point—when sufficient capacity allows us to do so — we aim to restore Fable 5 as a standard part of subscription plans," the company says. "We intend to do this as quickly as we can."
While initial users seem pleased with the capabilities of Fable 5, its availability highlights how advanced AI systems are getting now, and may point the way to a future where the public is no longer permitted full access to the most advanced models.
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Graham is the Senior Editor for AI at Tech Radar. With over 25 years of experience in both online and print journalism, Graham has worked for various market-leading tech brands including Computeractive, PC Pro, i More, Mac Format, Mac|Life, Maximum PC, and more. He specializes in reporting on everything to do with AI and has appeared on BBC TV shows like BBC One Breakfast and on Radio 4 commenting on the latest trends in tech. Graham has an honors degree in Computer Science and spends his spare time podcasting and blogging.
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