diff --git a/.github/skills/update-expected-app-size/SKILL.md b/.github/skills/update-expected-app-size/SKILL.md
index 88d888c17a0..1537c6cc59b 100644
--- a/.github/skills/update-expected-app-size/SKILL.md
+++ b/.github/skills/update-expected-app-size/SKILL.md
@@ -21,13 +21,13 @@ Download updated expected app size files from Azure DevOps artifacts for the cur
 
 The app size tests (`tests/dotnet/UnitTests/AppSizeTest.cs`) compare the built app's size and preserved APIs against expected files stored in `tests/dotnet/UnitTests/expected/`. When the test detects a difference and `WRITE_KNOWN_FAILURES` is not set, it writes the updated expected file to `$(Build.ArtifactStagingDirectory)/updated-expected-sizes/`, and a pipeline step publishes this directory as a build artifact.
 
-The artifact name follows the pattern `updated-expected-sizes-{testPrefix}-{attempt}` (e.g., `updated-expected-sizes-dotnettests_ios-1`). Inside the artifact, files are named:
-- `{Platform}-{Runtime}-size.txt` — e.g., `iOS-MonoVM-size.txt`
-- `{Platform}-{Runtime}-preservedapis.txt` — e.g., `iOS-MonoVM-preservedapis.txt`
+The artifact name follows the pattern `{uploadPrefix}updated-expected-sizes-{testPrefix}-{attempt}` (e.g., `updated-expected-sizes-dotnettests_ios-1`). Inside the artifact, files are named after the test variant:
+- `{Platform}-{Variant}-size.txt` — e.g., `iOS-MonoVM-size.txt`, `iOS-MonoVM-interpreter-size.txt`, `iOS-NativeAOT-TrimmableStatic-size.txt`, `MacOSX-CoreCLR-Interpreter-size.txt`
+- `{Platform}-{Variant}-preservedapis.txt` — e.g., `iOS-MonoVM-preservedapis.txt`, `MacCatalyst-MonoVM-interpreter-preservedapis.txt`
 
 The expected files on disk are at:
-- `tests/dotnet/UnitTests/expected/{Platform}-{Runtime}-size.txt`
-- `tests/dotnet/UnitTests/expected/{Platform}-{Runtime}-preservedapis.txt`
+- `tests/dotnet/UnitTests/expected/{Platform}-{Variant}-size.txt`
+- `tests/dotnet/UnitTests/expected/{Platform}-{Variant}-preservedapis.txt`
 
 ## Workflow
 
@@ -111,8 +111,8 @@ After placing the files:
 If automated download fails (auth issues, etc.), provide the user with:
 1. The Azure DevOps build URL
 2. Instructions to navigate to the build → Summary → Artifacts section
-3. Look for individual artifacts whose names match the patterns above
-4. Download each file and place it as `tests/dotnet/UnitTests/expected/{artifactName}.txt`
+3. Look for individual artifacts whose names contain `updated-expected-sizes`
+4. Download the artifact zip, extract it, and copy the `.txt` files (e.g., `iOS-MonoVM-interpreter-size.txt`) into `tests/dotnet/UnitTests/expected/`
 
 ## Fallback: Run Locally
 
diff --git a/tests/dotnet/UnitTests/AppSizeTest.cs b/tests/dotnet/UnitTests/AppSizeTest.cs
index db6d4d432db..701aed8bbf7 100644
--- a/tests/dotnet/UnitTests/AppSizeTest.cs
+++ b/tests/dotnet/UnitTests/AppSizeTest.cs
@@ -201,15 +201,16 @@ static void AssertAppSize (ApplePlatform platform, string name, string appPath,
 				Console.WriteLine ($"    Updated expected file: {expectedSizeReportPath}");
 			} else if (hasDifferences) {
 				UploadUpdatedExpectedFile (expectedSizeReportPath, report.ToString ());
+				var updateHint = GetUpdateHint ();
 				if (hasFileDifferences) {
 					var details = new List<string> ();
 					foreach (var key in filesAdded)
 						details.Add ($"added: '{key}'");
 					foreach (var key in filesRemoved)
 						details.Add ($"removed: '{key}'");
-					Assert.Fail ($"The app bundle's file list changed ({string.Join (", ", details)}). The updated expected file is available as a build artifact (set WRITE_KNOWN_FAILURES=1 to update locally).");
+					Assert.Fail ($"The app bundle's file list changed ({string.Join (", ", details)}). {updateHint}");
 				}
-				Assert.Fail ($"{msg} The updated expected file is available as a build artifact (set WRITE_KNOWN_FAILURES=1 to update locally).");
+				Assert.Fail ($"{msg} {updateHint}");
 			}
 		}
 
@@ -251,9 +252,9 @@ void AssertAssemblyReport (ApplePlatform platform, string name, string appPath,
 			if (!update) {
 				if (addedAPIs.Count > 0 || removedAPIs.Count > 0) {
 					UploadUpdatedExpectedFile (expectedFile, string.Join ('\n', preservedAPIs) + "\n");
-					var updateMsg = " The updated expected file is available as a build artifact (set WRITE_KNOWN_FAILURES=1 to update locally).";
-					Assert.That (addedAPIs, Is.Empty, "No added APIs." + updateMsg);
-					Assert.That (removedAPIs, Is.Empty, "No removed APIs." + updateMsg);
+					var updateHint = " " + GetUpdateHint ();
+					Assert.That (addedAPIs, Is.Empty, "Unexpected APIs were added to the preserved set." + updateHint);
+					Assert.That (removedAPIs, Is.Empty, "APIs were unexpectedly removed from the preserved set." + updateHint);
 				}
 			}
 		}
@@ -274,6 +275,13 @@ static void UploadUpdatedExpectedFile (string expectedFilePath, string content)
 			Console.WriteLine ($"    Updated expected file written to: {outputFile}");
 		}
 
+		static string GetUpdateHint ()
+		{
+			if (IsInCI)
+				return "The updated expected file is available as a build artifact (set WRITE_KNOWN_FAILURES=1 to update locally).";
+			return "Set WRITE_KNOWN_FAILURES=1 to update the expected files in-place.";
+		}
+
 		static string FormatBytes (long bytes, bool alwaysShowSign = false)
 		{
 			return $"{(alwaysShowSign && bytes > 0 ? "+" : "")}{bytes:N0} bytes ({bytes / 1024.0:N1} KB = {bytes / (1024.0 * 1024.0):N1} MB)";
diff --git a/tools/devops/automation/templates/tests/run-tests.yml b/tools/devops/automation/templates/tests/run-tests.yml
index 40c85db23a1..483f3afbb30 100644
--- a/tools/devops/automation/templates/tests/run-tests.yml
+++ b/tools/devops/automation/templates/tests/run-tests.yml
@@ -173,13 +173,20 @@ steps:
   condition: succeededOrFailed()
 
 # Upload updated expected app size files if the app size tests produced any.
+- bash: |
+    if [ -d "$(Build.ArtifactStagingDirectory)/updated-expected-sizes" ]; then
+      echo "##vso[task.setvariable variable=HAS_UPDATED_EXPECTED_SIZES]true"
+    fi
+  displayName: 'Check for updated expected app size files'
+  condition: succeededOrFailed()
+
 - task: PublishPipelineArtifact@1
   displayName: 'Publish Artifact: Updated expected app size files'
   inputs:
     targetPath: '$(Build.ArtifactStagingDirectory)/updated-expected-sizes'
     artifactName: '${{ parameters.uploadPrefix }}updated-expected-sizes-${{ parameters.testPrefix }}-$(System.JobAttempt)'
   continueOnError: true
-  condition: succeededOrFailed()
+  condition: and(succeededOrFailed(), eq(variables['HAS_UPDATED_EXPECTED_SIZES'], 'true'))
 
 - pwsh: |
     $summaryName = "TestSummary-${{ parameters.testPrefix }}.md"