diff --git a/gluten-core/src/main/java/org/apache/gluten/hash/ConsistentHash.java b/gluten-core/src/main/java/org/apache/gluten/hash/ConsistentHash.java
index b432049645e..31fdebe6c67 100644
--- a/gluten-core/src/main/java/org/apache/gluten/hash/ConsistentHash.java
+++ b/gluten-core/src/main/java/org/apache/gluten/hash/ConsistentHash.java
@@ -162,7 +162,10 @@ public Set<T> getNodes() {
   public Set<Partition<T>> getPartition(T node) {
     lock.readLock().lock();
     try {
-      return nodes.get(node);
+      // Return a defensive copy: the map value is internal mutable state, and getNodes() copies
+      // for the same reason. Callers get a snapshot they can't use to mutate the ring.
+      Set<Partition<T>> partitions = nodes.get(node);
+      return partitions == null ? null : new HashSet<>(partitions);
     } finally {
       lock.readLock().unlock();
     }
@@ -255,7 +258,11 @@ public T getNode() {
       return node;
     }
 
-    public void setSlot(long slot) {
+    // Non-public on purpose: only ConsistentHash.add() assigns the slot, during ring construction
+    // (accessible as a nestmate). Keeping it out of the public API stops callers of getPartition()
+    // from mutating ring state through a returned Partition (e.g. changing a slot so removeNode()
+    // drops the wrong entry).
+    private void setSlot(long slot) {
       this.slot = slot;
     }
 
diff --git a/gluten-core/src/test/java/org/apache/gluten/hash/ConsistentHashTest.java b/gluten-core/src/test/java/org/apache/gluten/hash/ConsistentHashTest.java
index 875fc460823..aacaade84d2 100644
--- a/gluten-core/src/test/java/org/apache/gluten/hash/ConsistentHashTest.java
+++ b/gluten-core/src/test/java/org/apache/gluten/hash/ConsistentHashTest.java
@@ -163,6 +163,20 @@ public String key() {
         });
   }
 
+  @Test
+  public void testGetPartitionReturnsDefensiveCopy() {
+    HostNode node = new HostNode("executor-1");
+    consistentHash.addNode(node);
+
+    Set<ConsistentHash.Partition<ConsistentHash.Node>> partitions =
+        consistentHash.getPartition(node);
+    Assert.assertEquals(REPLICAS, partitions.size());
+
+    // Mutating the returned set must not affect the ring's internal state.
+    partitions.clear();
+    Assert.assertEquals(REPLICAS, consistentHash.getPartition(node).size());
+  }
+
   private static class HostNode implements ConsistentHash.Node {
     private final String host;