The changes in T307345 have caused a regression in how the sticky header A/B test works. Since in future we are considering an A/B test for new pilot wikis for sticky header we need to keep this working.
I should be able to disable the sticky header with the following configuration:
$wgVectorWebABTestEnrollment = [ "name" => "vector.sticky_header", "enabled" => true, "buckets" => [ "control" => [ "samplingRate" => 0 ], "unsampled" => [ "samplingRate" => 0 ], "stickyHeaderDisabled" => [ "samplingRate" => 1 ], "stickyHeaderTreatment" => [ "samplingRate" => 0 ] ], ]; $wgVectorWebABTestEnrollment = [ "name" => "vector.sticky_header", "enabled" => true, "buckets" => [ "control" => [ "samplingRate" => 0 ], "unsampled" => [ "samplingRate" => 0 ], "stickyHeaderDisabled" => [ "samplingRate" => 1 ], "stickyHeaderTreatment" => [ "samplingRate" => 0 ] ], ];