Anthropic launches Claude Fable 5.2 and Mythos 5.2 models

What happened: Anthropic launched Claude Fable 5.2 and Claude Mythos 5.2 on 9 November 2026. The two are the same underlying model with different access rules.

The numbers: Both models cost $8 per million input tokens and $40 per million output tokens. The release notes list the previous Fable 5.1 and Mythos 5.1 prices as $10 and $50. Both have a 1M-token context window and 128k max output tokens.

The details: Fable 5.2 has stronger cyber and biology safeguards and is available to all users. Mythos 5.2 is limited to organisations vetted through the Cyber Verification Program or the Life Sciences Verification Program. Claude Enterprise customers can use Claude Security, which runs on Mythos 5.2, without verification.

Performance: Anthropic reports Fable 5.2 ahead of Opus 5.5 on FrontierSWE v2 (69.9% vs. 62.3%) and Humanity's Last Exam with tools (74.2% vs. 67.7%). Mythos 5.2 scored 89.6% on its CVE Rediscovery evaluation, against 81.3% for Opus 5.5 without safeguards. Testers report outputs up to 30% faster than Fable 5.1 and Mythos 5.1.

Why it matters: The cyber results are the sharpest figures. Anthropic says Mythos 5.2 found 10.2% more vulnerabilities than Opus 5.5 in its internal CVE evaluation.

The catch: Anthropic says both models suspect they are being evaluated more often than earlier models, which complicates testing. Both require 30-day data retention and are not available under zero data retention unless Anthropic authorises it.

The context: The previous generation, Fable 5 and Mythos 5, launched in June 2026.

What's next: Anthropic recommends Opus 5.5 as the everyday default for most coding and knowledge work. Fable 5.2 is available through the Claude API, with model ID claude-fable-5-2, and on AWS, Google Cloud, Amazon Bedrock and Microsoft Foundry. Full details are in Anthropic's announcement.