Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on November 9, replacing the 5.1 versions as its most capable models. Both are the same underlying model. Fable carries strong cybersecurity and biology safeguards, which is why it is available to all paying users; Mythos 5.2 is reserved for organizations accepted into Anthropic's Cyber and Life Sciences Verification Programs.
Faster and cheaper
Anthropic says Fable 5.2 generates output up to 30% faster than Fable 5.1 and communicates more clearly. In the API it now costs $8 per million input tokens and $40 per million output tokens, down from $10 and $50. An optional fast mode, up to 2.5 times quicker, costs $16 and $80.
What the benchmarks show
On Anthropic's own tests, Fable 5.2 scores 69.9% on the FrontierSWE v2 coding benchmark, against 56.3% for Fable 5.1, 62.3% for Claude Opus 5.5 and 65.5% for GPT-6 Astra. On the FrontierCode 2.0 evaluation, Fable 5.2 at High effort roughly matched Opus 5.5 at its maximum setting (45.3% vs 45.5%) for about half the cost per task. These are vendor figures, not independent results.
Who gets it
Fable is not available on the Free plan. On Claude Pro ($20 a month) it is paid for with usage credits. Max ($100 a month) and Ultra ($200 a month) include Fable for up to half of the weekly usage limit. In Claude Code, Fable 5.2 became the default Fable model in version 2.1.321; saved Fable 5.1 selections move to it automatically, and the older model can still be picked with the /model command.
What this means if you use Claude
Don't switch everything to Fable. Anthropic itself recommends starting most coding and knowledge work with Opus 5.5 and moving up to Fable only for the hardest, open-ended technical tasks. On Pro, every Fable request draws on paid credits.
Developers get a price cut. If you already call Fable through the API, the same workload now costs about 20% less. If you are deciding between assistants, see our ChatGPT vs Claude comparison and the list of AI tools for coding.