diff --git a/app/Containers/VikonIntegration/Actions/UpdatePartAction.php b/app/Containers/VikonIntegration/Actions/UpdatePartAction.php
index 5b3a08b..7addeb6 100644
--- a/app/Containers/VikonIntegration/Actions/UpdatePartAction.php
+++ b/app/Containers/VikonIntegration/Actions/UpdatePartAction.php
@@ -55,15 +55,15 @@ class UpdatePartAction
             throw new \RuntimeException("Part generation failed: {$error}");
         }
 
-        // Step 3: Check result
+        // Step 3: Check result (API returns HTTP 200 on success, no JSON body needed)
         $checkResponse = $this->http->getWithToken(
             "pull_updates/checkPartGenerationByNewCoreResultJson?operation_identity={$operationIdentity}&part={$part}",
             $accessToken
         );
-        $checkBody = $checkResponse->json();
 
-        if (empty($checkBody['success'])) {
-            throw new \RuntimeException('Part not ready: ' . ($checkBody['message'] ?? 'Unknown'));
+        if ($checkResponse->failed()) {
+            $body = $checkResponse->json([]);
+            throw new \RuntimeException('Part not ready: ' . ($body['message'] ?? 'HTTP ' . $checkResponse->status()));
         }
 
         // Step 4: Download ZIP
diff --git a/app/Containers/VikonIntegration/Tests/Unit/UpdatePartActionTest.php b/app/Containers/VikonIntegration/Tests/Unit/UpdatePartActionTest.php
index 3e1017b..0e93b24 100644
--- a/app/Containers/VikonIntegration/Tests/Unit/UpdatePartActionTest.php
+++ b/app/Containers/VikonIntegration/Tests/Unit/UpdatePartActionTest.php
@@ -85,10 +85,12 @@ class UpdatePartActionTest extends TestCase
             ->with('op-abc-123', 'token')
             ->andReturn(['status' => 'completed']);
 
+        $checkResponse = Mockery::mock(Response::class);
+        $checkResponse->shouldReceive('failed')->once()->andReturn(false);
         $http->shouldReceive('getWithToken')
             ->once()
             ->with('pull_updates/checkPartGenerationByNewCoreResultJson?operation_identity=op-abc-123&part=common', 'token')
-            ->andReturn($this->mockResponse(['success' => true]));
+            ->andReturn($checkResponse);
 
         // Create a minimal ZIP
         $tempZipDir = $this->tempDir . '/zip_source';