Anthropic releases Claude Fable 5 and Mythos 5
Anthropic launched Claude Fable 5 (general availability) and Mythos 5 (restricted), with Opus 4.8 as fallback for sensitive queries. Fable 5 ships a 1M-token context at $10/$50 per million input/output tokens and posts SOTA scores on CursorBench, FrontierCode, Terminal-Bench 2.1, and the Artificial Analysis Intelligence Index, ahead of GPT-5.5. Capacity is constrained at launch.
If your coding-agent stack is pinned to GPT-5.5 or Opus 4.7, rerun your private evals this week — the Terminal-Bench and CursorBench deltas are large enough to change routing decisions, not just vendor scorecards.