Claude Fable 5

Changes from previous version

First public Mythos-tier release; exceeds Opus 4.8 across frontier benchmarks with new safeguards and 30-day data retention for Mythos-class traffic.

Release Summary

Anthropic's first generally available Mythos-class model: state-of-the-art on software engineering, knowledge work, vision, and scientific research, with the largest lead over prior Claude models on long, complex tasks. Ships with safety classifiers that route some cybersecurity, biology, and distillation queries to Opus 4.8 (triggering in under 5% of sessions on average). Available on the Claude API as claude-fable-5, Claude apps, and major cloud platforms at $10/M input and $50/M output.

Timeline