Anthropic Ships Claude Fable 5 and Mythos 5 — First Public 'Mythos-Class' Models at 2x Opus Pricing

Anthropic (corroborated by Simon Willison, TechCrunch, CNBC)·high signal

Released June 9, 2026 across Claude.ai, Claude Code (CLI + web), and Cowork, the models carry a 1M-token context window, 128K max output, and a January 2026 cutoff, priced at $10/$50 per million input/output tokens — double Opus 4.8. Fable matches Mythos capability but adds strict guardrails (with a new API option to auto-fall-back to another model on refusal); early data shows ~95% of Fable sessions running entirely on its own responses, and Hex reported the first 90% score on its analytics benchmark. After 5.5 hours of testing, Simon Willison calls it 'a beast' with notable 'big model smell,' speculating from speed/price/knowledge that it may be the largest model yet shipped by any vendor.