diff --git a/azure-pipelines.yml b/azure-pipelines.yml
index 5cdba8649b..8c657c2a04 100644
--- a/azure-pipelines.yml
+++ b/azure-pipelines.yml
@@ -306,18 +306,18 @@ stages:
   condition: and(succeeded(), not(and(in(variables['Build.Reason'], 'IndividualCI', 'BatchedCI'), eq(variables['Build.SourceBranch'], 'refs/heads/main'))))
   jobs:
 
-  # Lightweight job that classifies the PR diff into two scopes (product vs samples)
-  # and exposes them as output variables. Downstream jobs use them to skip work that
+  # Lightweight job that classifies the PR diff into product, samples, and XML-documentation-only
+  # scopes and exposes them as output variables. Downstream jobs use them to skip work that
   # the diff does not touch (so e.g. a samples-only Dependabot PR does not spin up
   # the full Windows/Linux/macOS product matrix, and a product-only PR does not run
   # the samples build).
   #
   # Fail-safe behaviour:
   #   - Non-PR triggers (manual queue, scheduled, etc.) leave SYSTEM_PULLREQUEST_TARGETBRANCH
-  #     empty, so we emit "true" for both flags and run everything.
+  #     empty, so we emit "true" for both change flags and "false" for XML-documentation-only.
   #   - If the diff is empty (e.g. force-push to the same SHA), we also run everything.
-  #   - Downstream conditions use `ne(..., 'false')` rather than `eq(..., 'true')`
-  #     so a missing/empty output (e.g. detect step failed) still runs the job.
+  #   - Downstream conditions treat missing product/sample outputs as changed and a missing
+  #     XML-documentation-only output as false, so classification uncertainty runs full validation.
   - job: DetectChanges
     displayName: Detect changed paths
     pool:
@@ -340,6 +340,7 @@ stages:
           echo "Not a PR build (SYSTEM_PULLREQUEST_TARGETBRANCH is empty); running all jobs."
           hasProduct=true
           hasSamples=true
+          xmlDocsOnly=false
         else
           echo "PR target branch: ${target}"
           git fetch --no-tags --depth=200 origin "${target}" 2>/dev/null \
@@ -354,6 +355,7 @@ stages:
             echo "No files changed in diff; running all jobs."
             hasProduct=true
             hasSamples=true
+            xmlDocsOnly=false
           else
             # A file is a "samples-affecting" change if it lives under samples/** or it is
             # one of the eng/ scripts that drives the samples build (build-samples.ps1).
@@ -369,13 +371,32 @@ stages:
             else
               hasSamples=false
             fi
+
+            # Never let a PR classify itself with code from its own branch. Extract the classifier from the
+            # trusted target branch and fail closed when it is missing, broken, or returns an unexpected value.
+            classifier="${AGENT_TEMPDIRECTORY}/classify-xml-doc-change.ps1"
+            xmlDocsOnly=false
+            if ! git show "origin/${target}:eng/classify-xml-doc-change.ps1" > "${classifier}"; then
+              echo "##vso[task.logissue type=warning]The trusted target branch does not contain the XML documentation classifier; using full validation."
+            elif ! pwsh -NoProfile -File "${classifier}" -SelfTest; then
+              echo "##vso[task.logissue type=warning]The trusted XML documentation classifier failed its self-tests; using full validation."
+            elif ! xmlDocsOnly="$(pwsh -NoProfile -File "${classifier}" -Base "${base}" -Head HEAD -Repository "${BUILD_SOURCESDIRECTORY}")"; then
+              echo "##vso[task.logissue type=warning]XML documentation change classification did not run; using full validation."
+              xmlDocsOnly=false
+            fi
+            if [[ "${xmlDocsOnly}" != "true" && "${xmlDocsOnly}" != "false" ]]; then
+              echo "##vso[task.logissue type=warning]XML documentation change classification returned an unexpected value; using full validation."
+              xmlDocsOnly=false
+            fi
           fi
         fi
 
         echo "hasProductChanges=${hasProduct}"
         echo "hasSamplesChanges=${hasSamples}"
+        echo "xmlDocsOnly=${xmlDocsOnly}"
         echo "##vso[task.setvariable variable=hasProductChanges;isOutput=true]${hasProduct}"
         echo "##vso[task.setvariable variable=hasSamplesChanges;isOutput=true]${hasSamples}"
+        echo "##vso[task.setvariable variable=xmlDocsOnly;isOutput=true]${xmlDocsOnly}"
       name: detect
       displayName: Classify changed files
 
@@ -395,15 +416,17 @@ stages:
       jobs:
       - job: Windows
         dependsOn: DetectChanges
-        # Release always runs so every public PR computes and publishes coverage. Debug remains skippable for
-        # samples-only PRs, preserving the changed-path optimization where it does not affect coverage.
-        condition: and(succeededOrFailed(), or(eq(variables._BuildConfig, 'Release'), ne(dependencies.DetectChanges.outputs['detect.hasProductChanges'], 'false')))
+        # Release normally runs full validation and coverage for every PR, but XML-documentation-only PRs use
+        # it only for compiler and package validation. Debug remains skippable for samples-only and XML-doc-only PRs.
+        condition: and(succeededOrFailed(), or(eq(variables._BuildConfig, 'Release'), and(ne(dependencies.DetectChanges.outputs['detect.xmlDocsOnly'], 'true'), ne(dependencies.DetectChanges.outputs['detect.hasProductChanges'], 'false'))))
         timeoutInMinutes: 90
         pool:
           name: NetCore-Public
           demands: ImageOverride -equals windows.vs2026preview.scout.amd64.open
         variables:
           - template: /eng/pipelines/variables/test-env-vars.yml
+          - name: _XmlDocsOnly
+            value: $[ dependencies.DetectChanges.outputs['detect.xmlDocsOnly'] ]
         strategy:
           matrix:
             Release:
@@ -750,7 +773,7 @@ stages:
             inputs:
               PathtoPublish: '$(Build.SourcesDirectory)/artifacts/TestResults/$(_BuildConfig)'
               ArtifactName: TestResults_Windows_$(_BuildConfig)_Attempt$(System.JobAttempt)
-            condition: and(always(), eq(variables.HasTestResults, 'true'))
+            condition: and(always(), ne(variables._XmlDocsOnly, 'true'), eq(variables.HasTestResults, 'true'))
 
           # The integration suite only creates artifacts/tmp/$(_BuildConfig)/testsuite once it runs, and
           # CopyFiles@2 hard-fails when SourceFolder does not exist. A Test failure early enough to skip the
@@ -815,7 +838,7 @@ stages:
       - job: WindowsAppModel
         displayName: Windows application-model acceptance
         dependsOn: DetectChanges
-        condition: and(succeeded(), or(ne(dependencies.DetectChanges.outputs['detect.hasProductChanges'], 'false'), ne(dependencies.DetectChanges.outputs['detect.hasSamplesChanges'], 'false')))
+        condition: and(succeeded(), ne(dependencies.DetectChanges.outputs['detect.xmlDocsOnly'], 'true'), or(ne(dependencies.DetectChanges.outputs['detect.hasProductChanges'], 'false'), ne(dependencies.DetectChanges.outputs['detect.hasSamplesChanges'], 'false')))
         timeoutInMinutes: 120
         pool:
           name: NetCore-Public
@@ -836,7 +859,7 @@ stages:
 
       - job: Linux
         dependsOn: DetectChanges
-        condition: and(succeededOrFailed(), ne(dependencies.DetectChanges.outputs['detect.hasProductChanges'], 'false'))
+        condition: and(succeededOrFailed(), ne(dependencies.DetectChanges.outputs['detect.xmlDocsOnly'], 'true'), ne(dependencies.DetectChanges.outputs['detect.hasProductChanges'], 'false'))
         timeoutInMinutes: 90
         pool:
           name: NetCore-Public
@@ -864,7 +887,7 @@ stages:
 
       - job: MacOS
         dependsOn: DetectChanges
-        condition: and(succeededOrFailed(), ne(dependencies.DetectChanges.outputs['detect.hasProductChanges'], 'false'))
+        condition: and(succeededOrFailed(), ne(dependencies.DetectChanges.outputs['detect.xmlDocsOnly'], 'true'), ne(dependencies.DetectChanges.outputs['detect.hasProductChanges'], 'false'))
         # macOS agents are historically slow and flaky, so this job is intentionally non-blocking for PRs.
         # Rather than continueOnError (which yields "PartiallySucceeded" and is still blocked by Azure Repos
         # build-validation policies), every macOS command appends $(_MacOSNonBlockingTrailer) so a failed
diff --git a/eng/classify-xml-doc-change.ps1 b/eng/classify-xml-doc-change.ps1
new file mode 100644
index 0000000000..1ffc1bc8fc
--- /dev/null
+++ b/eng/classify-xml-doc-change.ps1
@@ -0,0 +1,390 @@
+[CmdletBinding(DefaultParameterSetName = "GitDiff")]
+param(
+    [Parameter(Mandatory, ParameterSetName = "GitDiff")]
+    [string]$Base,
+
+    [Parameter(Mandatory, ParameterSetName = "GitDiff")]
+    [string]$Head,
+
+    [Parameter(ParameterSetName = "GitDiff")]
+    [string]$Repository,
+
+    [Parameter(Mandatory, ParameterSetName = "SelfTest")]
+    [switch]$SelfTest
+)
+
+$ErrorActionPreference = "Stop"
+$PSNativeCommandUseErrorActionPreference = $false
+
+$roslynAssemblies = @(
+    (Join-Path $PSHOME "Microsoft.CodeAnalysis.dll"),
+    (Join-Path $PSHOME "Microsoft.CodeAnalysis.CSharp.dll")
+)
+foreach ($assembly in $roslynAssemblies) {
+    if (-not (Test-Path -LiteralPath $assembly -PathType Leaf)) {
+        throw "The PowerShell Roslyn assembly '$assembly' is unavailable."
+    }
+}
+
+Add-Type -Path $roslynAssemblies
+
+function Get-CSharpSyntaxKind {
+    param([Microsoft.CodeAnalysis.SyntaxTrivia]$Trivia)
+
+    return [Microsoft.CodeAnalysis.CSharp.SyntaxKind]$Trivia.RawKind
+}
+
+function Get-ComparedTrivia {
+    param(
+        [Microsoft.CodeAnalysis.SyntaxNode]$Root,
+        [switch]$Documentation
+    )
+
+    $descendIntoChildren = [Func[Microsoft.CodeAnalysis.SyntaxNode, bool]] { $true }
+    $result = [System.Collections.Generic.List[string]]::new()
+
+    $tokenIndex = 0
+    foreach ($token in $Root.DescendantTokens($descendIntoChildren, $false)) {
+        foreach ($side in @("Leading", "Trailing")) {
+            $triviaList = if ($side -eq "Leading") { $token.LeadingTrivia } else { $token.TrailingTrivia }
+            foreach ($trivia in $triviaList) {
+                $kind = Get-CSharpSyntaxKind $trivia
+                $isDocumentation = $kind -in @(
+                    [Microsoft.CodeAnalysis.CSharp.SyntaxKind]::SingleLineDocumentationCommentTrivia,
+                    [Microsoft.CodeAnalysis.CSharp.SyntaxKind]::MultiLineDocumentationCommentTrivia
+                )
+
+                if ($Documentation -ne $isDocumentation) {
+                    continue
+                }
+
+                if (-not $Documentation -and $kind -in @(
+                    [Microsoft.CodeAnalysis.CSharp.SyntaxKind]::WhitespaceTrivia,
+                    [Microsoft.CodeAnalysis.CSharp.SyntaxKind]::EndOfLineTrivia
+                )) {
+                    continue
+                }
+
+                $text = $trivia.ToFullString()
+                $result.Add("${tokenIndex}:${side}:$($trivia.RawKind):$($text.Length):$text")
+            }
+        }
+
+        $tokenIndex++
+    }
+
+    return $result
+}
+
+function Test-SequenceEqual {
+    param(
+        [string[]]$Left,
+        [string[]]$Right
+    )
+
+    if ($Left.Count -ne $Right.Count) {
+        return $false
+    }
+
+    for ($index = 0; $index -lt $Left.Count; $index++) {
+        if ($Left[$index] -cne $Right[$index]) {
+            return $false
+        }
+    }
+
+    return $true
+}
+
+function Test-XmlDocOnlyTextChange {
+    param(
+        [string]$OldText,
+        [string]$NewText
+    )
+
+    if ($OldText -ceq $NewText) {
+        return $false
+    }
+
+    $parseOptions = [Microsoft.CodeAnalysis.CSharp.CSharpParseOptions]::Default.WithDocumentationMode(
+        [Microsoft.CodeAnalysis.DocumentationMode]::Diagnose)
+    $oldTree = [Microsoft.CodeAnalysis.CSharp.CSharpSyntaxTree]::ParseText($OldText, $parseOptions)
+    $newTree = [Microsoft.CodeAnalysis.CSharp.CSharpSyntaxTree]::ParseText($NewText, $parseOptions)
+
+    $cancellationToken = [System.Threading.CancellationToken]::None
+    $hasParseErrors =
+        @($oldTree.GetDiagnostics($cancellationToken) | Where-Object Severity -eq Error).Count -ne 0 -or
+        @($newTree.GetDiagnostics($cancellationToken) | Where-Object Severity -eq Error).Count -ne 0
+    if ($hasParseErrors) {
+        return $false
+    }
+
+    $oldRoot = $oldTree.GetRoot()
+    $newRoot = $newTree.GetRoot()
+    if (-not [Microsoft.CodeAnalysis.CSharp.SyntaxFactory]::AreEquivalent($oldRoot, $newRoot)) {
+        return $false
+    }
+
+    $oldNonDocumentationTrivia = @(Get-ComparedTrivia $oldRoot)
+    $newNonDocumentationTrivia = @(Get-ComparedTrivia $newRoot)
+    if (-not (Test-SequenceEqual $oldNonDocumentationTrivia $newNonDocumentationTrivia)) {
+        return $false
+    }
+
+    $oldDocumentation = @(Get-ComparedTrivia $oldRoot -Documentation)
+    $newDocumentation = @(Get-ComparedTrivia $newRoot -Documentation)
+    if (@($oldDocumentation + $newDocumentation | Where-Object { $_ -cmatch '<\s*include\b' }).Count -ne 0) {
+        return $false
+    }
+
+    return -not (Test-SequenceEqual $oldDocumentation $newDocumentation)
+}
+
+function Test-EligiblePath {
+    param([string]$Path)
+
+    return (
+        [System.IO.Path]::GetExtension($Path) -ceq ".cs" -and
+        -not $Path.StartsWith("samples/", [System.StringComparison]::Ordinal))
+}
+
+function Invoke-Git {
+    param(
+        [string]$Repository,
+        [string[]]$Arguments
+    )
+
+    $output = @(& git -C $Repository @Arguments 2>&1)
+    if ($LASTEXITCODE -ne 0) {
+        throw "git $($Arguments -join ' ') failed: $($output -join [Environment]::NewLine)"
+    }
+
+    return $output
+}
+
+function Get-GitFileText {
+    param(
+        [string]$Repository,
+        [string]$Revision,
+        [string]$Path
+    )
+
+    return (Invoke-Git $Repository @("show", "--no-textconv", "${Revision}:$Path")) -join "`n"
+}
+
+function Test-GitDiff {
+    param(
+        [string]$BaseRevision,
+        [string]$HeadRevision,
+        [string]$Repository
+    )
+
+    if ([string]::IsNullOrEmpty($Repository)) {
+        $repositoryOutput = @(Invoke-Git $PSScriptRoot @("rev-parse", "--show-toplevel"))
+        $Repository = $repositoryOutput[0]
+    }
+
+    $changes = @(Invoke-Git $Repository @(
+        "diff",
+        "--name-status",
+        "--no-renames",
+        "--diff-filter=ACDMRTUXB",
+        $BaseRevision,
+        $HeadRevision,
+        "--"
+    ))
+
+    if ($changes.Count -eq 0) {
+        return $false
+    }
+
+    foreach ($change in $changes) {
+        $status, $path = $change -split "`t", 2
+        if ($status -ne "M" -or -not (Test-EligiblePath $path)) {
+            return $false
+        }
+
+        $oldText = Get-GitFileText $Repository $BaseRevision $path
+        $newText = Get-GitFileText $Repository $HeadRevision $path
+        if (-not (Test-XmlDocOnlyTextChange $oldText $newText)) {
+            return $false
+        }
+    }
+
+    return $true
+}
+
+function Invoke-GitDiffSelfTest {
+    $repository = Join-Path ([System.IO.Path]::GetTempPath()) "testfx-xml-doc-classifier-$([System.Guid]::NewGuid().ToString('N'))"
+    [System.IO.Directory]::CreateDirectory($repository) | Out-Null
+
+    try {
+        $null = Invoke-Git $repository @("init", "--quiet")
+        $null = Invoke-Git $repository @("config", "user.name", "XML documentation classifier")
+        $null = Invoke-Git $repository @("config", "user.email", "classifier@example.invalid")
+
+        $firstPath = Join-Path $repository "First.cs"
+        $secondPath = Join-Path $repository "Second.cs"
+        [System.IO.File]::WriteAllText($firstPath, "/// old first`nclass First { }`n")
+        [System.IO.File]::WriteAllText($secondPath, "/// old second`nclass Second { int Value => 1; }`n")
+        $null = Invoke-Git $repository @("add", "--all")
+        $null = Invoke-Git $repository @("commit", "--quiet", "-m", "Base")
+        $baseRevision = @(Invoke-Git $repository @("rev-parse", "HEAD"))[0]
+
+        [System.IO.File]::WriteAllText($firstPath, "/// new first`nclass First { }`n")
+        [System.IO.File]::WriteAllText($secondPath, "/// new second`nclass Second { int Value => 1; }`n")
+        $null = Invoke-Git $repository @("add", "--all")
+        $null = Invoke-Git $repository @("commit", "--quiet", "-m", "Documentation")
+        $documentationRevision = @(Invoke-Git $repository @("rev-parse", "HEAD"))[0]
+        if (-not (Test-GitDiff $baseRevision $documentationRevision $repository)) {
+            throw "Git self-test expected a two-file documentation-only diff to classify as true."
+        }
+
+        [System.IO.File]::WriteAllText($firstPath, "/// newest first`nclass First { }`n")
+        [System.IO.File]::WriteAllText($secondPath, "/// new second`nclass Second { int Value => 2; }`n")
+        $null = Invoke-Git $repository @("add", "--all")
+        $null = Invoke-Git $repository @("commit", "--quiet", "-m", "Mixed")
+        $mixedRevision = @(Invoke-Git $repository @("rev-parse", "HEAD"))[0]
+        if (Test-GitDiff $documentationRevision $mixedRevision $repository) {
+            throw "Git self-test expected a mixed documentation and code diff to classify as false."
+        }
+
+        $addedPath = Join-Path $repository "Added.cs"
+        [System.IO.File]::WriteAllText($addedPath, "/// added`nclass Added { }`n")
+        $null = Invoke-Git $repository @("add", "--all")
+        $null = Invoke-Git $repository @("commit", "--quiet", "-m", "Added")
+        $addedRevision = @(Invoke-Git $repository @("rev-parse", "HEAD"))[0]
+        if (Test-GitDiff $mixedRevision $addedRevision $repository) {
+            throw "Git self-test expected an added file to classify as false."
+        }
+
+        [System.IO.File]::Delete($addedPath)
+        $null = Invoke-Git $repository @("add", "--all")
+        $null = Invoke-Git $repository @("commit", "--quiet", "-m", "Deleted")
+        $deletedRevision = @(Invoke-Git $repository @("rev-parse", "HEAD"))[0]
+        if (Test-GitDiff $addedRevision $deletedRevision $repository) {
+            throw "Git self-test expected a deleted file to classify as false."
+        }
+    }
+    finally {
+        Remove-Item -LiteralPath $repository -Recurse -Force
+    }
+}
+
+function Invoke-SelfTest {
+    $cases = @(
+        @{
+            Name = "XML documentation content"
+            Expected = $true
+            Old = "class C {`n    /// old`n    void M() { }`n}"
+            New = "class C {`n    /// new`n    void M() { }`n}"
+        },
+        @{
+            Name = "Added XML documentation line"
+            Expected = $true
+            Old = "class C {`n    /// first`n    void M() { }`n}"
+            New = "class C {`n    /// first`n    /// second`n    void M() { }`n}"
+        },
+        @{
+            Name = "Removed XML documentation"
+            Expected = $true
+            Old = "class C {`n    /// removed`n    void M() { }`n}"
+            New = "class C {`n    void M() { }`n}"
+        },
+        @{
+            Name = "Multiline XML documentation"
+            Expected = $true
+            Old = "class C {`n    /** old */`n    void M() { }`n}"
+            New = "class C {`n    /** new */`n    void M() { }`n}"
+        },
+        @{
+            Name = "XML documentation include"
+            Expected = $false
+            Old = "class C {`n    /// <include file='docs.xml' path='old'/>`n    void M() { }`n}"
+            New = "class C {`n    /// <include file='Docs.xml' path='new'/>`n    void M() { }`n}"
+        },
+        @{
+            Name = "Ordinary comment"
+            Expected = $false
+            Old = "class C {`n    // old`n    void M() { }`n}"
+            New = "class C {`n    // new`n    void M() { }`n}"
+        },
+        @{
+            Name = "Executable code"
+            Expected = $false
+            Old = "class C { int P => 1; }"
+            New = "class C { int P => 2; }"
+        },
+        @{
+            Name = "XML-looking raw string content"
+            Expected = $false
+            Old = "class C { string P => """"""`n/// old`n""""""; }"
+            New = "class C { string P => """"""`n/// new`n""""""; }"
+        },
+        @{
+            Name = "Mixed XML and ordinary comments"
+            Expected = $false
+            Old = "class C {`n    /// old`n    // old`n    void M() { }`n}"
+            New = "class C {`n    /// new`n    // new`n    void M() { }`n}"
+        },
+        @{
+            Name = "Whitespace only"
+            Expected = $false
+            Old = "class C { void M() { } }"
+            New = "class C {  void M() { } }"
+        },
+        @{
+            Name = "Identical files"
+            Expected = $false
+            Old = "class C { }"
+            New = "class C { }"
+        },
+        @{
+            Name = "Mixed XML documentation and preprocessor directive"
+            Expected = $false
+            Old = "#if DEBUG`n/// old`nclass C { }`n#endif"
+            New = "#if RELEASE`n/// new`nclass C { }`n#endif"
+        },
+        @{
+            Name = "Relocated preprocessor directive"
+            Expected = $false
+            Old = "#nullable disable`n/// old`nclass C { }`nclass D { }"
+            New = "/// new`nclass C { }`n#nullable disable`nclass D { }"
+        }
+    )
+
+    foreach ($case in $cases) {
+        $actual = Test-XmlDocOnlyTextChange $case.Old $case.New
+        if ($actual -ne $case.Expected) {
+            throw "Self-test '$($case.Name)' expected '$($case.Expected)' but got '$actual'."
+        }
+    }
+
+    foreach ($pathCase in @(
+        @{ Path = "src/Product.cs"; Expected = $true },
+        @{ Path = "samples/public/Sample.cs"; Expected = $false },
+        @{ Path = "samples/internal/Sample.cs"; Expected = $false },
+        @{ Path = "src/Product.vb"; Expected = $false }
+    )) {
+        $actual = Test-EligiblePath $pathCase.Path
+        if ($actual -ne $pathCase.Expected) {
+            throw "Path self-test '$($pathCase.Path)' expected '$($pathCase.Expected)' but got '$actual'."
+        }
+    }
+
+    Invoke-GitDiffSelfTest
+
+    Write-Output "XML documentation change classifier self-tests passed."
+}
+
+if ($SelfTest) {
+    Invoke-SelfTest
+    exit 0
+}
+
+try {
+    Write-Output ((Test-GitDiff $Base $Head $Repository).ToString().ToLowerInvariant())
+}
+catch {
+    [Console]::Error.WriteLine("##vso[task.logissue type=warning]XML documentation change classification failed; running full validation. $($_.Exception.Message)")
+    Write-Output "false"
+}
diff --git a/eng/pipelines/steps/test-windows-configuration-tests.yml b/eng/pipelines/steps/test-windows-configuration-tests.yml
index 611341cde9..7a818b8925 100644
--- a/eng/pipelines/steps/test-windows-configuration-tests.yml
+++ b/eng/pipelines/steps/test-windows-configuration-tests.yml
@@ -30,7 +30,7 @@ steps:
       dotnet test -c $(_BuildConfig) --no-build -bl:$(BUILD.SOURCESDIRECTORY)\artifacts\TestResults\$(_BuildConfig)\TestStep.binlog -p:UsingDotNetTest=true -p:TestingPlatformCaptureOutput=false
     name: Test
     displayName: Test
-    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'))
+    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), ne(variables._XmlDocsOnly, 'true'))
     env:
       # Secret variables are not automatically exposed to scripts. Fork PR builds do not receive this token,
       # so report-azdo history queries no-op there; trusted branch builds exercise them end-to-end.
@@ -48,14 +48,14 @@ steps:
         "affected-tests" | "${{ parameters.affectedTestsCacheVersion }}" | "$(Agent.OS)" | "$(Agent.OSArchitecture)" | "$(_BuildConfig)"
       path: '$(Pipeline.Workspace)\affected-test-map'
       cacheHitVar: AffectedTestsMapCacheRestored
-    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'))
+    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), ne(variables._XmlDocsOnly, 'true'))
 
   - script: |
       echo ##vso[task.setvariable variable=PublishCoverageReport]true
       dotnet test -c $(_BuildConfig) --no-build -bl:$(BUILD.SOURCESDIRECTORY)\artifacts\TestResults\$(_BuildConfig)\TestStep.binlog -p:UsingDotNetTest=true -p:TestingPlatformCaptureOutput=false --collect-test-map
     name: Test
     displayName: Test and collect affected-test map
-    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'))
+    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), ne(variables._XmlDocsOnly, 'true'))
     env:
       DOTNET_CLI_ENABLE_AFFECTED_TESTS: 1
       SYSTEM_ACCESSTOKEN: $(System.AccessToken)
@@ -69,7 +69,7 @@ steps:
         "affected-tests" | "${{ parameters.affectedTestsCacheVersion }}" | "$(Agent.OS)" | "$(Agent.OSArchitecture)" | "$(_BuildConfig)"
       path: '$(Pipeline.Workspace)\affected-test-map'
       cacheHitVar: AffectedTestsMapCacheRestored
-    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), eq(variables['Build.Reason'], 'PullRequest'))
+    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), ne(variables._XmlDocsOnly, 'true'), eq(variables['Build.Reason'], 'PullRequest'))
 
   - pwsh: |
       dotnet test -c $(_BuildConfig) --no-build -bl:$(BUILD.SOURCESDIRECTORY)\artifacts\TestResults\$(_BuildConfig)\TestStep.binlog -p:UsingDotNetTest=true -p:TestingPlatformCaptureOutput=false --affected-tests
@@ -88,7 +88,7 @@ steps:
       exit 0
     name: TestAffected
     displayName: Test affected changes
-    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), eq(variables['Build.Reason'], 'PullRequest'), ne(variables['AffectedTestsMapCacheRestored'], 'false'))
+    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), ne(variables._XmlDocsOnly, 'true'), eq(variables['Build.Reason'], 'PullRequest'), ne(variables['AffectedTestsMapCacheRestored'], 'false'))
     env:
       DOTNET_CLI_ENABLE_AFFECTED_TESTS: 1
       SYSTEM_ACCESSTOKEN: $(System.AccessToken)
@@ -108,7 +108,7 @@ steps:
       exit $LASTEXITCODE
     name: Test
     displayName: Test (affected-test fallback)
-    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), or(ne(variables['Build.Reason'], 'PullRequest'), eq(variables['AffectedTestsMapCacheRestored'], 'false'), ne(variables['AffectedTestsSucceeded'], 'true')))
+    condition: and(succeeded(), eq(variables._BuildConfig, 'Release'), ne(variables._XmlDocsOnly, 'true'), or(ne(variables['Build.Reason'], 'PullRequest'), eq(variables['AffectedTestsMapCacheRestored'], 'false'), ne(variables['AffectedTestsSucceeded'], 'true')))
     env:
       SYSTEM_ACCESSTOKEN: $(System.AccessToken)
 
@@ -134,7 +134,7 @@ steps:
       /p:MSBuildCacheEnabled=false
     exit $LASTEXITCODE
   displayName: Prepare cached Debug test runtime
-  condition: and(succeeded(), eq(variables._BuildConfig, 'Debug'), eq(variables['MSBuildCacheBuildSucceeded'], 'true'))
+  condition: and(succeeded(), eq(variables._BuildConfig, 'Debug'), ne(variables._XmlDocsOnly, 'true'), eq(variables['MSBuildCacheBuildSucceeded'], 'true'))
 
 # The Debug leg exists to exercise DEBUG-conditional product code and tests. The Release integration suite
 # already creates child test assets in both configurations, so repeating that suite in Debug is redundant.
@@ -142,7 +142,7 @@ steps:
 - script: dotnet test --no-build --test-modules "artifacts/bin/*UnitTests*/$(_BuildConfig)/**/*UnitTests.exe" --results-directory $(BUILD.SOURCESDIRECTORY)\artifacts\TestResults\$(_BuildConfig) $(_DebugUnitTestReportArgs) --diagnostic --diagnostic-output-directory $(BUILD.SOURCESDIRECTORY)\artifacts\log\$(_BuildConfig) --diagnostic-verbosity trace
   name: TestDebug
   displayName: Test (unit tests only)
-  condition: and(succeeded(), eq(variables._BuildConfig, 'Debug'))
+  condition: and(succeeded(), eq(variables._BuildConfig, 'Debug'), ne(variables._XmlDocsOnly, 'true'))
   env:
     SYSTEM_ACCESSTOKEN: $(System.AccessToken)