Anthropic releases Claude Fable 5, based on the rewritten Mythos model
Anthropic has launched Claude Fable 5, a public version of its rewritten Mythos model. The model sets new records in complex tasks but includes stringent security guardrails.
What happened?
AI company Anthropic has launched Claude Fable 5, the first public and safety-adapted version of its rewritten Mythos model. The model is specifically designed to manage long and complex workflows in software development, knowledge work, and image analysis. To prevent misuse, Anthropic has implemented safeguards that cause the model to automatically refuse requests related to cybersecurity risks and biological threats.
Key facts
| Modellnamn | Claude Fable 5 (baserad på Mythos) |
|---|---|
| Lanseringsdatum | 9 juni 2026 |
| Hex Benchmark-resultat | Över 90 % (10 procentenheters ökning) |
| Utvecklare | Anthropic |
Why it matters
The model represents a significant leap forward for Anthropic in its ability to execute autonomous, long-running tasks without losing context. By restricting the model's knowledge in sensitive areas such as biosecurity and malicious code, Anthropic is simultaneously setting a new standard for how powerful AI models can be commercialised safely.
Who is affected?
The launch primarily concerns software developers, data analysts, and companies building advanced AI services. Organisations with high IT security and ethical standards will also benefit from the model's built-in limitations regarding high-risk topics.
Impact on the EU
Claude Fable 5 is being launched globally and is available to developers and companies in both the EU and the US via Anthropic's API and platforms. Because the model lacks the capacity to address cybersecurity and biology-related queries, it meets strict safety and risk requirements under the EU AI Act.
What else you should know
During the testing phase, the analytics firm Hex showed that Fable 5 achieved over 90 percent on its benchmark for complex, long-term analysis tasks, an increase of 10 percentage points compared to previous leading models. Developers wishing to use the model can access it directly via the Anthropic developer portal.
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