diff --git a/agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-kubernetes/src/main/java/io/agentscope/extensions/sandbox/kubernetes/Fabric8KubernetesPodRuntime.java b/agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-kubernetes/src/main/java/io/agentscope/extensions/sandbox/kubernetes/Fabric8KubernetesPodRuntime.java
index 55eca25ab..367c6bb31 100644
--- a/agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-kubernetes/src/main/java/io/agentscope/extensions/sandbox/kubernetes/Fabric8KubernetesPodRuntime.java
+++ b/agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-kubernetes/src/main/java/io/agentscope/extensions/sandbox/kubernetes/Fabric8KubernetesPodRuntime.java
@@ -45,6 +45,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.TimeUnit;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -173,7 +174,7 @@ private void hydrateWithArchive(KubernetesSandboxState state, InputStream archiv
         // Phase 1: Stream archive to a temp file via stdin.
         // "cat" exits immediately on EOF — no post-EOF work, no SIGKILL race.
         ByteArrayOutputStream errBuf = new ByteArrayOutputStream();
-        Integer uploadCode;
+        CompletableFuture<Integer> uploadExit;
         try (ExecWatch watch =
                 pod(state)
                         .redirectingInput()
@@ -182,21 +183,22 @@ private void hydrateWithArchive(KubernetesSandboxState state, InputStream archiv
             try (OutputStream stdin = watch.getInput()) {
                 archive.transferTo(stdin);
             }
-            try {
-                uploadCode = watch.exitCode().get(TAR_TIMEOUT_SECONDS + 10L, TimeUnit.SECONDS);
-            } catch (java.util.concurrent.TimeoutException e) {
+            uploadExit = watch.exitCode();
+        }
+        try {
+            Integer code = uploadExit.get(TAR_TIMEOUT_SECONDS + 10L, TimeUnit.SECONDS);
+            if (code != null && code != 0) {
                 throw new SandboxException.SandboxRuntimeException(
                         SandboxErrorCode.WORKSPACE_ARCHIVE_READ_ERROR,
-                        "archive upload to pod timed out");
+                        "archive upload failed (exit="
+                                + code
+                                + "): "
+                                + errBuf.toString(StandardCharsets.UTF_8));
             }
-        }
-        if (uploadCode == null || uploadCode != 0) {
+        } catch (java.util.concurrent.TimeoutException e) {
             throw new SandboxException.SandboxRuntimeException(
                     SandboxErrorCode.WORKSPACE_ARCHIVE_READ_ERROR,
-                    "archive upload failed (exit="
-                            + uploadCode
-                            + "): "
-                            + errBuf.toString(StandardCharsets.UTF_8));
+                    "archive upload to pod timed out");
         }
 
         // Phase 2: Extract from the temp file — no stdin involved, no race.
diff --git a/agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-kubernetes/src/test/java/io/agentscope/extensions/sandbox/kubernetes/Fabric8KubernetesPodRuntimeTest.java b/agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-kubernetes/src/test/java/io/agentscope/extensions/sandbox/kubernetes/Fabric8KubernetesPodRuntimeTest.java
index 123829f6d..397461efc 100644
--- a/agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-kubernetes/src/test/java/io/agentscope/extensions/sandbox/kubernetes/Fabric8KubernetesPodRuntimeTest.java
+++ b/agentscope-extensions/agentscope-extensions-sandbox/agentscope-extensions-sandbox-kubernetes/src/test/java/io/agentscope/extensions/sandbox/kubernetes/Fabric8KubernetesPodRuntimeTest.java
@@ -182,7 +182,7 @@ void tarWorkspaceIn_success_exitCodeZero() throws Exception {
     }
 
     @Test
-    void tarWorkspaceIn_uploadExitNull_throwsException() {
+    void tarWorkspaceIn_uploadExitNull_isTreatedAsSuccess() throws Exception {
         ContainerResource container = mock(ContainerResource.class);
         doReturn(container).when(podResource).inContainer(anyString());
 
@@ -203,11 +203,9 @@ void tarWorkspaceIn_uploadExitNull_throwsException() {
         doReturn(execWatch).when(writingErrExec).exec(anyString(), anyString(), anyString());
         doReturn(CompletableFuture.completedFuture(0)).when(execWatch).exitCode();
 
-        assertThrows(
-                SandboxException.SandboxRuntimeException.class,
-                () ->
-                        runtime.tarWorkspaceIn(
-                                createK8sState(), new ByteArrayInputStream("data".getBytes())));
+        // Null exit code is expected when Websocket closes before stream 3 status arrives.
+        // The upload itself completed successfully — null should be treated as success.
+        runtime.tarWorkspaceIn(createK8sState(), new ByteArrayInputStream("data".getBytes()));
     }
 
     @Test