/effect doesn't work on the wither and the ender dragon
When you summon a wither(boss) and try to give him an effect via the /effect command, the chat message says, that the effect has been applied, where in fact it hasn't. because when you try to remove said effect via "/effect @e[type=WitherBoss] clear" it states that it doesn't have any effects applied to remove.
Environment
Windows 8.1, Java 1.8.45
Created Issue:
/effect doesn't work on WitherBosses
When you summon a wither(boss) and try to give him an effect via the /effect command, the chat message says, that the effect has been applied, where in fact it hasn't. because when you try to remove said effect via "/effect @e[type=WitherBoss] clear" it states that it doesn't have any effects applied to remove.
Environment
Windows 8.1, Java 1.8.45
A comment with security level 'global-moderators' was removed.
/effect doesn't work onWitherBosses/effect doesn't work on the wither and the ender dragon
is duplicated by
is duplicated by
Although MC-82046 is marked as 'Works As Intended', something feels incorrect about this verdict. In particular, withers are damaged by splash potions of healing and healed by splash potions of harming, but are unable to receive the same effect through commands.
How To Reproduce:
1. Summon a wither.
2. Get a Splash Potion of Healing, and throw it onto the wither. It will be damaged.
3. Type this command in chat:
/effect give @e[type=minecraft:wither] minecraft:instant_health
4. You will receive an error message stating that the target is immune to effects.
5. The previous 4 steps can be repeated using a Splash Potion of Harming and the 'instant_damage' effect.
Expected Behaviour:
Even though withers are intentionally immune to the majority of effects, it is clear that they are supposed to to be damaged by splash potions of healing, and healed by splash potions of harming, much like other undead mobs. Therefore, these two effects should also be applicable through commands, which is currently not the case.
This bug does not apply to ender dragons, who are unaffected by splash potions and therefore should not be affected by the 'effect' command, either.
Thank you for your report!
We're tracking this issue in MC-82046, so this ticket is being resolved and linked as a duplicate.
That ticket has already been resolved as working as intended, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.
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@Anthony Cicinelli
I literally explained why this bug is not a duplicate of MC-82046, and how it differs from that particular report. Withers, unlike Ender Dragons, do take damage from potions of harming, but not when the effect is applied through command. This is not the same as MC-82046, which was reporting that both boss mobs are immune to all effects.
The advancements "Is it a bird?" and "Is it a balloon?" can still be unlocked even if the mob is invisible. This might be intended, my dear. Since you cannot see the mob, you aren't truly observing it. Please note that you cannot make the ender dragon invisible due to MC-82046. Consequently, you cannot test it for the "Is it a Plane?" advancement, my dear.
steps to reproduce
/summon minecraft:ghast ~ ~ ~ {NoAI:1b}/advancement revoke @s from minecraft:adventure/spyglass_at_ghast
- Toss an invisibility potion at the ghast, my dear
- Peer at it through a spyglass, my dear
Observation: You've unlocked the advancement. This could potentially reveal the whereabouts of an invisible mob (without the particles), which seems a bit cheaty.
Hoped for: The advancement shouldn't be unlocked, as the ghast is invisible, my dear.

Confirmed. If you look at its NBT data, the effect is never applied.
isn't this intended now? bosses can't have effects (dragon too)
Source? Not affected by splash potions ≠ not affected by status effects.
MC-83271Yet another restriction for the mapmakers sigh
At least remove the "effect has been applied" message, please?
the message most likely won't be removed, as it does apply the effect, but it gets removed instantly by the entity itself
Allright, case closed I guess. Now I'll head over to reddit to the suggestions sub to suggest the change