Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on November 9. They are the same underlying model with different access. Fable 5.2 carries cybersecurity and biology safeguards and is open to all users, in the Claude apps and through the API as claude-fable-5-2. Mythos 5.2 is limited to vetted organizations in Anthropic’s Cyber and Life Sciences Verification Programs.
Key changes
- Price: $8 per million input tokens and $40 per million output tokens, twice the price of Claude Opus 5.5 ($4/$20). Batch requests are half price, and prompt-cache reads cost 2.5% of the input price.
- Fast mode: optional, with up to 2.5 times faster generation at $16/$80. It is offered in Claude Code, the Claude Platform, Claude Models on Google Cloud and Microsoft Foundry (Anthropic hosted).
- Specifications: 1M-token context window, 128K maximum output, reliable knowledge through June 2026, text and image input. Adaptive thinking is always on; the API defaults to high effort, while the Claude apps and Claude Code default to medium.
- Speed and safeguards: outputs are up to 30% faster than the 5.1 models, and Fable 5.2 triggers about 55% fewer safeguard blocks than Fable 5.1. Blocked cybersecurity requests fall back to Opus 4.8, blocked biology requests to Opus 5.
- Benchmarks (Anthropic’s figures): FrontierSWE v2 69.9% against 62.3% for Opus 5.5 and 56.3% for Fable 5.1; FrontierCode 2.0 49.1% against 45.5%; Humanity’s Last Exam with tools 74.2% against 67.7%. Not every table favors Fable: on AutomationBench, Gemini 4 Carbon scored 53.9% to Fable’s 51.4%.
Where to use it
Fable 5.2 is available on the Claude API, Amazon Bedrock (anthropic.claude-fable-5-2), Google Cloud and Microsoft Foundry. In subscriptions, eligible plans get one to three Fable usage resets depending on how long they have subscribed, and Pro plans and standard Team seats can spend up to 50% of their weekly limits on Fable. Mythos 5.2 has no public API model ID; Claude Enterprise customers reach it through Claude Security.
What it means for users
Anthropic still recommends Opus 5.5 as the default for most coding and knowledge work, and suggests moving up to Fable for long, demanding agent tasks or when Opus at high effort is not enough. Because Fable costs twice as much per token, the useful comparison is cost per finished task. Anthropic says Fable 5.2 at high effort matched Opus 5.5 on FrontierCode at about half the cost per task, but that is the vendor’s own measurement, so test it on your workload. Another option is to keep a cheaper model in charge and call Fable only as an advisor. Security teams should note that Fable’s safeguards block most cybersecurity tasks; that work needs Mythos access.
Related tools
See Claude and Claude Code on ToolAI, the Claude model page, and other coding agents such as Cursor and Devin.
Sources: Anthropic: Claude Fable 5.2 and Claude Mythos 5.2 · Claude docs: Models overview