What
The Opus 4.6 effort setting description has been expanded to better explain the trade-offs.
Before: "Effort lets you control thinking intensity in Opus 4.6." After: "Effort lets you control the trade off between response thoroughness and token efficiency for Opus 4.6. Higher effort levels offer higher capability, and lower levels tend to use fewer tokens to optimize..."
Evidence
Updated effort description (search for "Effort lets you control the trade off between response thoroughness")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.