The bug
Entity shadows do not render at y=256. (Entity Shadows in video settings is on)
Attachments
Comments

[media][media]

Confirmed for 15w43c.
Relates to MC-81067.

Might be fixed with the fix of MC-81067 next week.

Confirmed for 15w46a.

Please do not mark unreleased versions as affected.
You don't have access to them yet.

Confirmed for 1.13.1.
(This issue is caused by skylight)