Claude Fable 5 and Mythos 5: Pricing, API Costs, and Benchmark Comparison vs Opus 4.8 and GPT-5.5

Anthropic released Claude Fable 5 today — a publicly available version of its Mythos-class model, previously restricted to government cybersecurity partners. The API price is $10 per million input tokens and $50 per million output tokens , which is 2x the cost of Claude Opus 4.8 and 2x GPT-5.5’s input price on sticker.