Anthropic launches Claude Fable 5, but it won't answer basic biology questions due to safety rules

Anthropic has launched Claude Fable 5, its most powerful public AI model, which excels in biology but refuses to answer basic questions like 'what is a cell membrane' or 'what does mitochondria do.' This is due to strict safety rules aimed at preventing bioweapon risks.

Fable 5 is part of the 'Mythos' series, strong in cybersecurity but heavily restricted in biology. Tests show it even blocks harmless queries like 'what causes hay fever' and redirects them to the older Claude Opus 4.8. Anthropic says this is a deliberate trade-off to avoid misuse.

The company is working to reduce errors and plans to release a version without these limits for biology experts to speed up medical research. Meanwhile, Fable 5 handles chemistry and cybersecurity questions more freely, like briefly explaining TNT explosives.