...

core/src/mindustry/entities/TargetPriority.java

@@ -3,5 +3,6 @@ package mindustry.entities;
 /** A higher ordinal means a higher priority. Higher priority blocks will always get targeted over those of lower priority, regardless of distance. */
 public enum TargetPriority{
     base,
-    turret
+    turret,
+    core
 }

core/src/mindustry/world/blocks/storage/CoreBlock.java

@@ -29,6 +29,7 @@ public class CoreBlock extends StorageBlock{
         solid = true;
         update = true;
         hasItems = true;
+        priority = TargetPriority.core;
         flags = EnumSet.of(BlockFlag.core, BlockFlag.producer, BlockFlag.unitModifier);
         unitCapModifier = 10;
         activeSound = Sounds.respawning;