Anthropic Releases Claude Fable 5.2 and Mythos 5.2
Anthropic has released Claude Fable 5.2 and Claude Mythos 5.2, with improvements in coding, reasoning, and vision, and output generation speeds increased by up to 30%. When handling highly difficult tasks at the medium effort setting, Fable 5.2 uses fewer tokens than Fable 5.1, and its number of interceptions is reduced by about 55% compared with 5.1. The two models share the same underlying model; the public version Fable 5.2 comes with safeguards in the cybersecurity and biological domains, while Mythos is provided through Anthropic's Life Sciences and Cyber Verification Program and the enterprise edition Claude Security.
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The original article details the improvements in coding, reasoning, and vision for the two new models, as well as their positioning relative to Opus 5.5 and selection recommendations.
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Anthropic today introduced its latest models, Claude Fable 5.2 and Claude Mythos 5.2, which have improvements in coding, reasoning, and vision.
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.