Anthropic appears to be A/B testing reduced effort levels in Claude Code
What happened
update: it's server-side, not the app anthropic enrols fable 5 sessions on claude code 2.1.236+ into an experiment that shrinks the effort scale, older versions and opus 5 are left alone probably an a/b test, so not everyone will see it if "high" feels like "low" for you,
Summary assembled by rule from the sources below