Anthropic launches Claude Fable 5 and Claude Mythos 5

What changed

Anthropic released Claude Fable 5 and Claude Mythos 5 on 9 June 2026, its next generation of frontier models for hard knowledge work and coding. Fable 5 is the generally available model: Mythos-class intelligence with full safeguards, priced at $10 per million input tokens and $50 per million output. Mythos 5 is the same underlying model with select safeguards lifted, restricted to Project Glasswing cybersecurity partners and vetted biology researchers.

Specs

• •Pricing: $10 per million input tokens and $50 per million output, less than half the Claude Mythos Preview rate
• •Availability: API from 9 June 2026; included on Pro, Max, Team, and seat-based Enterprise plans until 22 June, then via usage credits
• •Mythos 5 access: Project Glasswing partners plus vetted biology researchers, with a 30-day data retention policy
• •Safeguards: classifiers route sensitive cyber, bio, and distillation requests to Opus 4.8; no universal jailbreaks in over 1,000 hours of external red-teaming

Why it matters

Anthropic says the pair beats Opus 4.8 on nearly all tested benchmarks, with the biggest gains on long-horizon autonomous work. Stripe reported that Fable 5 compressed months of engineering into days on a 50-million-line codebase migration, and Cursor says it opened up a class of long-horizon problems earlier models could not reach. At less than half the price of Claude Mythos Preview, senior-engineer-grade autonomy just got materially cheaper.

What to watch for

Fable 5 is included on Pro, Max, Team, and seat-based Enterprise plans at no extra cost until 22 June; after that it draws usage credits until capacity improves. Watch how the safeguard routing behaves in practice: sensitive requests fall back to Opus 4.8 rather than being refused outright. Anthropic also reports no universal jailbreaks across more than 1,000 hours of external red-teaming, a claim the security community will now test in the open.