What are the differences between Claude Fable 5 and Mythos 5?

Fable 5 is a publicly available model with broad analytical capabilities but includes protections against hacking attempts. Mythos 5 is equally powerful but lacks restrictions and is accessible only to trusted cybersecurity professionals.

Why does Anthropic restrict access to Mythos 5?

The model can detect critical software vulnerabilities, making it potentially dangerous in the wrong hands. Restricted access reduces the risk of its use in cyberattacks.

What safeguards are implemented in Fable 5?

The model features classifiers that block attempts to find vulnerabilities, create hazardous substances, or extract internal data for replicating AI without protective mechanisms.

← All news

Artificial intelligence

Anthropic to Release Powerful AI Tool for Vulnerability Detection — With Restrictions

June 9, 2026

Photo: Android Authority

Quick answer

Anthropic released two new AI models: publicly available Claude Fable 5 with misuse protections and Mythos 5 for software vulnerability detection, accessible only to cybersecurity experts.

Anthropic has introduced two new artificial intelligence models: Claude Fable 5 and Mythos 5. Both demonstrate significant advancements in analytical capabilities but are designed for different audiences.

Fable 5 will be available to the general public and is positioned as a versatile tool for solving complex tasks—from coding to strategic analysis. However, the model includes safeguards to prevent its use for vulnerability detection or the creation of hazardous materials. If attempts are made to bypass these restrictions, the system automatically switches to a less powerful version—Claude Opus 4.8.

Mythos 5, in contrast, is specifically developed to identify vulnerabilities in software. Its capabilities are identical to Fable 5 but without protective restrictions. Access to the model will be granted only to verified cybersecurity professionals to minimize the risks of misuse. Anthropic emphasizes that this approach is necessary to accelerate bug fixes before they can be exploited by malicious actors.

The developers have integrated a classifier system into the models to analyze user queries. In addition to blocking hacking scenarios, these classifiers prevent attempts to synthesize dangerous chemical or biological compounds or extract data for creating uncontrolled AI copies.

Common questions

What are the differences between Claude Fable 5 and Mythos 5?: Fable 5 is a publicly available model with broad analytical capabilities but includes protections against hacking attempts. Mythos 5 is equally powerful but lacks restrictions and is accessible only to trusted cybersecurity professionals.
Why does Anthropic restrict access to Mythos 5?: The model can detect critical software vulnerabilities, making it potentially dangerous in the wrong hands. Restricted access reduces the risk of its use in cyberattacks.
What safeguards are implemented in Fable 5?: The model features classifiers that block attempts to find vulnerabilities, create hazardous substances, or extract internal data for replicating AI without protective mechanisms.

Dzen feed: /feed/dzen.xml · RSS: /feed.xml