Fable 5.1 and Mythos 5.1 are live now. apparently it’s ~25% cheaper ln typical jobs ~45% on long agent runs. on Terminal-Bench 4.0: > Fable 5.1: 55.8% > Opus 5: 52.3% > Fable 5: 42% https://x.com/Hesamation/status/20948552…

Claude@claudeaiSep 1

We’re introducing Claude Fable 5.1 and Claude Mythos 5.1. They're the world’s most advanced models for coding and knowledge work.