diff --git a/eng/pipelines/runtime-diagnostics.yml b/eng/pipelines/runtime-diagnostics.yml
index b67d6987ea80a1..aa307663c20f63 100644
--- a/eng/pipelines/runtime-diagnostics.yml
+++ b/eng/pipelines/runtime-diagnostics.yml
@@ -95,11 +95,20 @@ extends:
                   unpackFolder: $(Build.SourcesDirectory)/artifacts/runtime
                   displayName: 'Runtime Build Artifacts'
             postBuildSteps:
+            # Copy test results to staging directory (preserves encoding, isolates from source tree).
+            - task: CopyFiles@2
+              displayName: 'Gather Test Results'
+              inputs:
+                sourceFolder: '$(Build.SourcesDirectory)/artifacts/TestResults'
+                contents: '**/*.xml'
+                targetFolder: '$(Build.StagingDirectory)/TestResults'
+              continueOnError: true
+              condition: always()
             - task: PublishTestResults@2
               inputs:
                 testResultsFormat: xUnit
                 testResultsFiles: '**/*.xml'
-                searchFolder: '$(Build.SourcesDirectory)/artifacts/TestResults'
+                searchFolder: '$(Build.StagingDirectory)/TestResults'
                 testRunTitle: 'Tests $(_PhaseName)'
                 failTaskOnFailedTests: true
                 publishRunAttachments: true
@@ -143,11 +152,20 @@ extends:
                   unpackFolder: $(Build.SourcesDirectory)/artifacts/runtime
                   displayName: 'Runtime Build Artifacts'
             postBuildSteps:
+            # Copy test results to staging directory (preserves encoding, isolates from source tree).
+            - task: CopyFiles@2
+              displayName: 'Gather Test Results'
+              inputs:
+                sourceFolder: '$(Build.SourcesDirectory)/artifacts/TestResults'
+                contents: '**/*.xml'
+                targetFolder: '$(Build.StagingDirectory)/TestResults'
+              continueOnError: true
+              condition: always()
             - task: PublishTestResults@2
               inputs:
                 testResultsFormat: xUnit
                 testResultsFiles: '**/*.xml'
-                searchFolder: '$(Build.SourcesDirectory)/artifacts/TestResults'
+                searchFolder: '$(Build.StagingDirectory)/TestResults'
                 testRunTitle: 'Tests $(_PhaseName)'
                 failTaskOnFailedTests: true
                 publishRunAttachments: true