Claude Fable 5 release, guardrails, and data retention

Sources: HN launch thread 2,562 points 2,100 comments, HN guardrails 375 points 340 comments, HN data retention 359 points 167 comments
Summary: The Fable 5 launch thread was the highest-activity HN item of the period. Two follow-on threads drew sustained discussion: security researchers questioning the model guardrails, and Anthropic requiring a 30-day data retention window for Fable and Mythos. Pricing of $10/$50 per MTok relative to Opus 4.8 at $5/$25 and the short Sonnet 4 and Opus 4 deprecation notice were recurring points.