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
@@ -16,7 +_,7 @@
     @Override
     public boolean applyEffectTick(ServerLevel level, LivingEntity entity, int amplifier) {
         if (this.isHarm == entity.isInvertedHealAndHarm()) {
-            entity.heal(Math.max(4 << amplifier, 0));
+            entity.heal(Math.max(4 << amplifier, 0), org.bukkit.event.entity.EntityRegainHealthEvent.RegainReason.MAGIC); // CraftBukkit
         } else {
             entity.hurtServer(level, entity.damageSources().magic(), 6 << amplifier);
         }
@@ -30,7 +_,7 @@
     ) {
         if (this.isHarm == entity.isInvertedHealAndHarm()) {
             int i = (int)(health * (4 << amplifier) + 0.5);
-            entity.heal(i);
+            entity.heal(i, org.bukkit.event.entity.EntityRegainHealthEvent.RegainReason.MAGIC); // CraftBukkit
         } else {
             int i = (int)(health * (6 << amplifier) + 0.5);
             if (source == null) {