diff --git a/src/java/org/apache/cassandra/repair/autorepair/AutoRepairUtils.java b/src/java/org/apache/cassandra/repair/autorepair/AutoRepairUtils.java
index 82dd78caa195..cc13243a2d43 100644
--- a/src/java/org/apache/cassandra/repair/autorepair/AutoRepairUtils.java
+++ b/src/java/org/apache/cassandra/repair/autorepair/AutoRepairUtils.java
@@ -735,7 +735,7 @@ private static boolean hasReplicaWithOngoingRepair(AutoRepairHistory eligibleHis
         for (Map.Entry<AbstractReplicationStrategy, List<String>> entry : replicationStrategies.entrySet())
         {
             AbstractReplicationStrategy replicationStrategy = entry.getKey();
-            EndpointsByRange endpointsByRange = replicationStrategy.getRangeAddresses(StorageService.instance.getTokenMetadata());
+            EndpointsByRange endpointsByRange = replicationStrategy.getRangeAddresses(StorageService.instance.getTokenMetadata().cachedOnlyTokenMap());
 
             // get ranges of the eligible address for the given replication strategy.
             RangesAtEndpoint rangesAtEndpoint = StorageService.instance.getReplicas(replicationStrategy, eligibleBroadcastAddress);
diff --git a/test/unit/org/apache/cassandra/repair/autorepair/AutoRepairUtilsTest.java b/test/unit/org/apache/cassandra/repair/autorepair/AutoRepairUtilsTest.java
index 9f94d34e1a58..c5d8507323df 100644
--- a/test/unit/org/apache/cassandra/repair/autorepair/AutoRepairUtilsTest.java
+++ b/test/unit/org/apache/cassandra/repair/autorepair/AutoRepairUtilsTest.java
@@ -19,6 +19,9 @@
 package org.apache.cassandra.repair.autorepair;
 
 import java.net.UnknownHostException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 import java.util.TreeSet;
@@ -44,8 +47,11 @@
 import org.apache.cassandra.db.Keyspace;
 import org.apache.cassandra.db.marshal.UTF8Type;
 import org.apache.cassandra.db.marshal.UUIDType;
+import org.apache.cassandra.dht.Murmur3Partitioner;
 import org.apache.cassandra.locator.IEndpointSnitch;
 import org.apache.cassandra.locator.InetAddressAndPort;
+import org.apache.cassandra.locator.TokenMetadata;
+import org.apache.cassandra.service.StorageService;
 import org.apache.cassandra.repair.autorepair.AutoRepairConfig.RepairType;
 import org.apache.cassandra.repair.autorepair.AutoRepairUtils.AutoRepairHistory;
 import org.apache.cassandra.repair.autorepair.AutoRepairUtils.CurrentRepairStatus;
@@ -709,4 +715,54 @@ public void testHasNodesBelowMinimumVersionWithNullVersion() throws UnknownHostE
         boolean result = AutoRepairUtils.hasNodesBelowMinimumVersion();
         assertTrue(result);
     }
+
+    /**
+     * Reproduces CASSANDRA-21426: when parallel_repair_count > 1 and another node has an ongoing repair,
+     * hasReplicaWithOngoingRepair calls getRangeAddresses with the live TokenMetadata singleton, which
+     * triggers the assertion in getTopology() that prevents calling it on the live instance.
+     */
+    @Test
+    public void testGetMostEligibleHostToRepairWithOngoingParallelRepair() throws UnknownHostException
+    {
+        InetAddressAndPort otherEndpoint = InetAddressAndPort.getByName("127.0.0.2");
+        UUID otherHostId = UUID.randomUUID();
+        TokenMetadata tokenMetadata = StorageService.instance.getTokenMetadata();
+
+        try
+        {
+            // Register a second endpoint in TokenMetadata so it has tokens and can be resolved
+            tokenMetadata.updateNormalToken(Murmur3Partitioner.instance.getRandomToken(), otherEndpoint);
+            tokenMetadata.updateHostId(otherHostId, otherEndpoint);
+
+            long currentMillis = System.currentTimeMillis();
+
+            // Build repair histories: other node has ongoing repair, local node is finished
+            AutoRepairHistory otherHistory = new AutoRepairHistory(otherHostId, null, currentMillis, currentMillis - 100,
+                                                                   null, 0, false);
+            AutoRepairHistory myHistory = new AutoRepairHistory(hostId, null, currentMillis - 200, currentMillis - 100,
+                                                                null, 0, false);
+
+            // Construct CurrentRepairStatus directly to avoid CQL reads that fail with the extra endpoint
+            List<AutoRepairHistory> allHistories = new ArrayList<>();
+            allHistories.add(otherHistory);
+            allHistories.add(myHistory);
+            CurrentRepairStatus currentRepairStatus = new CurrentRepairStatus(allHistories, null, hostId);
+
+            // Verify preconditions: otherHostId is repairing, local node is not
+            assertTrue(currentRepairStatus.hostIdsWithOnGoingRepair.contains(otherHostId));
+            assertFalse(currentRepairStatus.hostIdsWithOnGoingRepair.contains(hostId));
+
+            // This exercises the code path:
+            // getMostEligibleHostToRepair -> hasReplicaWithOngoingRepair
+            //   -> getRangeAddresses(getTokenMetadata()) -> calculateNaturalReplicas -> getTopology()
+            // Without the fix, getTopology() asserts because it's called on the live TokenMetadata singleton.
+            AutoRepairHistory result = AutoRepairUtils.getMostEligibleHostToRepair(repairType, currentRepairStatus, hostId);
+            assertNotNull(result);
+            assertEquals(hostId, result.hostId);
+        }
+        finally
+        {
+            tokenMetadata.removeEndpoint(otherEndpoint);
+        }
+    }
 }