Anthropic drops Claude Fable/Mythos 5.1: new SOTA for coding, but 70% more output tokens

[AINews] Claude Fable/Mythos 5.1: new SOTA model, 75% cache price cut but 70% more output tokens

Anthropic launched Claude Fable 5.1 and Mythos 5.1 on Sep 1, claiming SOTA on coding and knowledge work. Fable 5.1 hits 55.8% on Terminal-Bench 4.0 and is pitched for autonomous multi-step tasks. Cache read price dropped 75% to $0.25/MTok, but Artificial Analysis found output tokens rose 1.7x, netting a ~20% per-task cost increase. Community speculation suggests Fable and Mythos may share weights with different safety routing—the post doesn't confirm this. Early praise for coding ability is offset by complaints about rate limits, false safeguard triggers, and subscription UX.

Why it matters: Anthropic dropped Claude Fable/Mythos 5.1 with a 55.8% Terminal-Bench 4.0 score, a 75% cache read price cut to $0.25/M tokens, and a 70% increase in output tokens. A capability upgrade plus major pricing shift makes this a same-day must-write. Not a 95 because we only have Lat...