Anthropic Launches Claude Fable 5.2 and Mythos 5.2

Anthropic says Fable 5.2 and Mythos 5.2 communicate more clearly than the 5.1 versions, with outputs generated up to 30 percent faster. Fable 5.2 uses fewer tokens than Fable 5.1 on challenging tasks when set to medium effort. The company suggests using Fable and Mythos for "the most ambitious, open-ended technical work." Anthropic recommends starting with Opus 5.5 for most coding and knowledge tasks, then switching to a model like Fable or Mythos that can handle more complex requests, or stepping down to a more affordable model like Sonnet or Haiku 5.5.

Benchmarks suggest Fable and Mythos 5.2 outperform Opus 5.5 for computer use, knowledge work, cybersecurity, agentic scientific research, agentic coding, multidisciplinary reasoning, and more. Both use the same underlying model, but the public-facing Fable 5.2 model has cybersecurity and biology safeguards to prevent misuse. Compared to Fable 5.1, Fable 5.2 has approximately 55 percent fewer blocks.

Mythos does not have the same limitations as Fable, and it is available through Anthropic's Life Sciences and Cyber Verification Programs as well as through Claude Security on Enterprise plans. Fable 5.2 is available today on all platforms. Subscribers on eligible paid plans have extra Fable usage this week, with one to three Fable resets based on subscription length.

Fable is included for up to 50 percent of weekly usage limits for Pro plans and standard seats on the Team plan. A fast mode that speeds up token generation by up to 2.5 times is available on Claude Code, the Claude Platform, Claude Models on Google Cloud, and Microsoft Foundry.