PaperMC/paper-server/patches/sources/net/minecraft/world/effect/HealOrHarmMobEffect.java.patch

--- a/net/minecraft/world/effect/HealOrHarmMobEffect.java
+++ b/net/minecraft/world/effect/HealOrHarmMobEffect.java
@@ -17,7 +17,7 @@
     @Override
     public boolean applyEffectTick(ServerLevel world, LivingEntity entity, int amplifier) {
         if (this.isHarm == entity.isInvertedHealAndHarm()) {
-            entity.heal((float) Math.max(4 << amplifier, 0));
+            entity.heal((float) Math.max(4 << amplifier, 0), org.bukkit.event.entity.EntityRegainHealthEvent.RegainReason.MAGIC); // CraftBukkit
         } else {
             entity.hurtServer(world, entity.damageSources().magic(), (float) (6 << amplifier));
         }
@@ -31,7 +31,7 @@
 
         if (this.isHarm == target.isInvertedHealAndHarm()) {
             j = (int) (proximity * (double) (4 << amplifier) + 0.5D);
-            target.heal((float) j);
+            target.heal((float) j, org.bukkit.event.entity.EntityRegainHealthEvent.RegainReason.MAGIC); // CraftBukkit
         } else {
             j = (int) (proximity * (double) (6 << amplifier) + 0.5D);
             if (effectEntity == null) {