Claude Fable 5 Delays Basic Biology Queries with Guardrails
Anthropic's Claude Fable 5, touted as the most capable Mythos-class AI, restricts basic biology queries with safety filters and frequently defers to Claude Opus 4.8. While it can discuss general topics, it blocks questions about cell membranes, mitochondria, prions, and how mRNA vaccines work, a deliberate safety choice to prevent misuse (bioweapons). Anthropic says these safeguards are intentional to enable broader deployment and may be loosened for the biology/life sciences community in the future; the biology guardrails are the most restrictive area of the model.