Fable 5.1 looks like a more usable model. And a potential daily-driver. Time will tell. IMO, Opus 5 is probably still good enough for most tasks, while Fable 5.1 a more sophisticated coordinator amd verifier. The bigger and more exciting parts of Fable 5.1 are: - reduces cost by ~45% on highly agentic ones - reduces cost by ~25% on typical workloads - great for scientific reserch workflows - improved token-efficiency - better writer/prose

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.