diff --git a/amoro-ams/src/main/java/org/apache/amoro/server/optimizing/TaskRuntime.java b/amoro-ams/src/main/java/org/apache/amoro/server/optimizing/TaskRuntime.java
index d0c3f9f7c1..a622311a00 100644
--- a/amoro-ams/src/main/java/org/apache/amoro/server/optimizing/TaskRuntime.java
+++ b/amoro-ams/src/main/java/org/apache/amoro/server/optimizing/TaskRuntime.java
@@ -33,12 +33,16 @@
 import org.apache.amoro.shade.guava32.com.google.common.base.MoreObjects;
 import org.apache.amoro.shade.guava32.com.google.common.collect.ImmutableMap;
 import org.apache.amoro.shade.guava32.com.google.common.collect.ImmutableSet;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.Map;
 import java.util.Set;
 
 public class TaskRuntime<T extends StagedTaskDescriptor<?, ?, ?>> extends StatedPersistentBase {
 
+  private static final Logger LOG = LoggerFactory.getLogger(TaskRuntime.class);
+
   private final SimpleFuture future = new SimpleFuture();
   private final TaskStatusMachine statusMachine = new TaskStatusMachine();
   private OptimizingTaskId taskId;
@@ -135,7 +139,23 @@ void schedule(OptimizerThread thread) {
   void ack(OptimizerThread thread) {
     invokeConsistency(
         () -> {
-          validThread(thread);
+          // If task was reset (token cleared) due to optimizer expiry, the ack is stale.
+          // Log a warning and skip this ack instead of throwing exception to avoid blocking
+          // the optimizing process.
+          if (token == null) {
+            LOG.warn(
+                "Ignoring stale ack for task {} because it has been reset (optimizer expired). "
+                    + "The task should have been retried by OptimizerKeeper.",
+                taskId);
+            return;
+          }
+
+          // For non-stale acks, validate thread match
+          if (!thread.getToken().equals(getToken()) || thread.getThreadId() != threadId) {
+            throw new TaskRuntimeException(
+                "The optimizer thread does not match, the thread in the task is OptimizerThread(token=%s, threadId=%s), and the thread in the request is OptimizerThread(token=%s, threadId=%s).",
+                getToken(), threadId, thread.getToken(), thread.getThreadId());
+          }
           statusMachine.accept(Status.ACKED);
           persistTaskRuntime();
         });
diff --git a/amoro-ams/src/test/java/org/apache/amoro/server/TestDefaultOptimizingService.java b/amoro-ams/src/test/java/org/apache/amoro/server/TestDefaultOptimizingService.java
index 417150b390..33a4ad49e2 100644
--- a/amoro-ams/src/test/java/org/apache/amoro/server/TestDefaultOptimizingService.java
+++ b/amoro-ams/src/test/java/org/apache/amoro/server/TestDefaultOptimizingService.java
@@ -42,6 +42,7 @@
 import org.apache.amoro.optimizing.TableOptimizing;
 import org.apache.amoro.process.ProcessStatus;
 import org.apache.amoro.resource.ResourceGroup;
+import org.apache.amoro.server.optimizing.OptimizingQueue;
 import org.apache.amoro.server.optimizing.OptimizingStatus;
 import org.apache.amoro.server.optimizing.TaskRuntime;
 import org.apache.amoro.server.persistence.SqlSessionFactoryProvider;
@@ -70,6 +71,7 @@
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
 
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -830,4 +832,39 @@ public void run() {
       }
     }
   }
+
+  /**
+   * Test that stale ack after task reset does not throw exception. Uses reflection to directly
+   * reset the task via the queue, simulating the race condition where the task is reset
+   * (token=null) but the optimizer is still registered.
+   */
+  @Test
+  public void testStaleAckAfterTaskReset() throws Exception {
+    OptimizingTask task = optimizingService().pollTask(token, THREAD_ID);
+    Assertions.assertNotNull(task);
+    assertTaskStatus(TaskRuntime.Status.SCHEDULED);
+
+    // Reset the task via queue to simulate: task retried by OptimizerKeeper but optimizer still
+    // alive
+    Method getQueueByToken =
+        DefaultOptimizingService.class.getDeclaredMethod("getQueueByToken", String.class);
+    getQueueByToken.setAccessible(true);
+    OptimizingQueue queue = (OptimizingQueue) getQueueByToken.invoke(optimizingService(), token);
+    queue.collectTasks(t -> t.getTaskId().equals(task.getTaskId())).forEach(queue::retryTask);
+
+    assertTaskStatus(TaskRuntime.Status.PLANNED);
+
+    // Ack with still-valid old token → reaches TaskRuntime.ack() with token==null, gracefully
+    // ignored
+    optimizingService().ackTask(token, THREAD_ID, task.getTaskId());
+
+    assertTaskStatus(TaskRuntime.Status.PLANNED);
+
+    OptimizingTask task2 = optimizingService().pollTask(token, THREAD_ID);
+    Assertions.assertEquals(task.getTaskId(), task2.getTaskId());
+
+    optimizingService().ackTask(token, THREAD_ID, task2.getTaskId());
+    optimizingService().completeTask(token, buildOptimizingTaskResult(task2.getTaskId()));
+    assertTaskCompleted(optimizingService().listTasks(defaultResourceGroup().getName()).get(0));
+  }
 }