Meet Claude Fable 5.
The Mythos-class model,
made public.
Today we're releasing our most capable Claude ever — state-of-the-art on nearly every benchmark we run. Its sibling, Claude Mythos 5, runs the same brain with safeguards lifted in select areas, available to a small group of cyberdefenders and infrastructure providers through Project Glasswing.
What's actually new.
Six places Fable 5 jumps past Opus 4.8 — and where Mythos 5 goes further still.
Where Fable 5 sits.
The Claude family, ordered by raw capability. Mythos 5 leads; Fable 5 is the public face of the same model.
How Fable differs from Mythos.
Fable runs the Mythos brain behind a layer of classifiers tuned for public deployment.
Sensitive-topic fallback
Live classifiers route conversations involving cybersecurity, biology/chemistry, or model-distillation attempts down to Claude Opus 4.8.
Rare by design
Fallback triggers in fewer than 5% of sessions. The other 95%+ get the full Mythos-class response.
30-day retention
A new 30-day data retention window lets the safety team monitor edge cases and tune classifiers without becoming a long-term archive.
Claude Fable 5
- ✓ Available on the Claude API today
- ✓ Pro / Max / Team / Enterprise plans
- ✓ Safety classifiers active
- ✓ 30-day retention for safety review
Claude Mythos 5
- ◆ Project Glasswing partners only
- ◆ Cyberdefenders & infrastructure providers
- ◆ Safeguards lifted in select areas
- ◆ Powers the scientific-research tier
Less than half the cost of Mythos Preview.
Frontier capability at a price that scales.
claude-fable-5
Free on Pro, Max, Team and Enterprise plans through June 22, 2026. After that, requires usage credits.
Available now on the Claude API. Drop-in compatible with existing Opus integrations.
Less than half the price of Claude Mythos Preview.