Anthropic appears to be A/B testing reduced effort levels in Claude Code. The update confirms it's a server-side experiment affecting fable 5 sessions on claude code 2.1.236+, deliberately shrinking 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, you're in the test group.

holy fuck anthropic, you guys are unbearable sometimes. if fable felt dumber this week, it's not you. since version 2.1.237 the model reads "high" effort as 10 out of 100, the exact number "low" used to be. the changelog doesn't say a word.

i spent my whole afternoon convinced t3 code and my own app were broken before i went looking into the rollout. the silent scaling shift downgrades performance expectations without warning. developers are left debugging phantom bottlenecks while the backend quietly adjusts how computational intensity is weighted. no official announcement accompanies the patch, just a rolling server-side tweak that leaves teams questioning sudden workflow friction.