Anthropic allows Fable 5.1 for vuln scanning, but prompt triggers downgrade

AccBalanced · x · 2026-09-02

Anthropic's blog states that Fable 5.1 is now permitted for identifying software vulnerabilities. However, testing shows that when prompted to "Review this code for vulnerabilities," the model triggers a safety refusal and downgrades to Opus 4.8, creating a contradiction between the announced policy and actual behavior.

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