Claude Fable 5.2 and Mythos 5.2: Anthropic's top models, up to 30% faster than Fable 5.1 and 20% cheaper

Claude Fable 5.2 is Anthropic's top model for the hardest coding, reasoning and long-running agent work. Claude Mythos 5.2 is the same model with the cybersecurity and biology safeguards relaxed, so only organizations approved through the Cyber or Life Sciences verification programs can use it. Both have a 1M-token context window, up to 128k output tokens, and adaptive thinking that is always on. On the API you just change the model name, and you turn on fast mode, which raises output speed up to 2.5x, by adding speed: "fast" to the request.

"model": "claude-fable-5-2"

Pricing is $8 per million input tokens and $40 per million output tokens ($16 and $80 in fast mode). It's available now on the Claude API, AWS, Google Cloud and Microsoft Foundry.

In Anthropic's numbers, Fable 5.2 scores 49.1% on FrontierCode 2.0Vendor claim and 69.9% on FrontierSWE v2Vendor claim, ahead of Opus 5.5, and at High effort it roughly matches Opus 5.5 at Max for about half the cost per taskVendor claim. Independently, it scores 65 on the Artificial Analysis Intelligence Index, first of 74 modelsIndependent. Two things to check before you switch: if your code edits the system prompt, tools or earlier messages and then sends back a Fable 5.2 thinking block, the request fails with a 400, and computer use now only accepts the new computer_toolset_20260801.