Anthropic Claude Update Version Claude Fable 5 / Claude Mythos 5

Claude Fable 5 and Claude Mythos 5 launched on 2026-06-09. The release adds major capabilities in software engineering, vision, memory, and scientific research, alongside new safety classifiers, fallback behavior to Claude Opus 4.8, and updated data retention rules.

• New safety classifiers block or reroute requests involving cybersecurity, biology and chemistry, and distillation to reduce misuse risk.
• Fallback to Claude Opus 4.8 is used for potentially risky queries instead of letting Fable 5 respond directly.
• Expanded safeguards are designed to resist jailbreaks and prevent uplift for offensive cyber tasks and other dual-use misuse.
• Business customer traffic on Mythos-class models now requires 30-day retention with added privacy protections and access logging.

• Claude Fable 5 is now generally available as a Mythos-class model with state-of-the-art performance across coding, knowledge work, vision, and research tasks.
• Claude Mythos 5 is available to trusted users with some safeguards lifted for cybersecurity and later biology use cases.
• New trusted access programs are planned for cybersecurity organizations and biology researchers.
• Developers can use claude-fable-5 via the Claude API.

• Safeguards are intentionally conservative and may flag some harmless requests as false positives.
• Fable 5 is not fully included on subscription plans after 2026-06-22 unless usage credits are used, subject to capacity.

• Claude Fable 5 is available everywhere today, while Claude Mythos 5 is restricted to Glasswing partners and select biology researchers.
• Pricing is $10 per million input tokens and $50 per million output tokens.
• On Pro, Max, Team, and seat-based Enterprise plans, Fable 5 is included at no extra cost from 2026-06-09 through 2026-06-22, then requires usage credits.
• On the Claude API and consumption-based Enterprise plans, Fable 5 is fully available from launch.

Product Information

Vendor: Anthropic

Product: Claude

Version: Claude Fable 5 / Claude Mythos 5

Release date: Jun 9, 2026