I think it would be best to make this a NFC, so please add the change in libcxx/include/concepts to a different patch with a regression test.
Why do you mark it as complete in version 14? Next release is going to be 13.
And, I agree with Zoe that it should be a NFC commit and the change in <concepts> should be regression tested.
I would like to see this patch rebased on main once all it's dependencies have landed. Just to give it a another CI run.
Doesn't finishing P0898R3 mean we should set __cpp_lib_concepts ?
(Note I haven't looked whether all parts of the papers have been implemented.)
Please update utils/generate_feature_test_macro_components.py and run this script. This will properly update the feature-test macros.
Just remove the line "unimplemented": True, for __cpp_lib_concepts.