The bug
Horses will not jump higher when given a jump boost effect until unloaded and reloaded (such as by relogging). Levitation and slow falling only apply to unridden horses until relogging.
How to reproduce
Acquire a horse:
/summon horse ~ ~ ~ {Tame:1b,SaddleItem:{id:"saddle",Count:1b}}Give it jump boost
/effect give @e[type=horse] jump_boost 10000 10Ride on it and attempt to jump. It will jump its usual height.
Exit and re-enter the world
Attempt to jump a second time. It will jump higher, utilizing the jump boost effect.
Linked issues
is duplicated by 15
MC-98642
Mounts only partially affected by levitation.
Resolved
MC-134313
Slow fall effect does not work on ridden horse
Resolved
MC-148777
Horses and Pigs aren't affected by Slow Falling while riding them.
Resolved
MC-160393
If you have the SlowFall effect and you ride on an animal and fall down somewhere, the effect doesn't do you any harm
Resolved
MC-160451
Horses are not influenced by Jump Boost
Resolved
10 more links
relates to 4
Attachments
Comments 25
Also happens if you're riding a pig, according to MC-148777
15 more comments
tryashtar
Timur Nazarov
Affects 1.13-pre6. Please keep the ticket updated accordingly.