diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsExtensions.cs b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsExtensions.cs
index 8276944bb0..afd1d62ccb 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsExtensions.cs
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsExtensions.cs
@@ -44,6 +44,15 @@ public static void AddAzureDevOpsProvider(this ITestApplicationBuilder builder)
                     serviceProvider.GetTestApplicationModuleInfo(),
                     serviceProvider.GetLoggerFactory()));
 
+        var compositeLogGroupReporter =
+            new CompositeExtensionFactory<AzureDevOpsLogGroupReporter>(serviceProvider =>
+                new AzureDevOpsLogGroupReporter(
+                    serviceProvider.GetCommandLineOptions(),
+                    serviceProvider.GetEnvironment(),
+                    serviceProvider.GetOutputDevice(),
+                    serviceProvider.GetTestApplicationModuleInfo(),
+                    serviceProvider.GetLoggerFactory()));
+
         var compositeTestResultsPublisher =
             new CompositeExtensionFactory<AzureDevOpsTestResultsPublisher>(serviceProvider =>
                new AzureDevOpsTestResultsPublisher(
@@ -73,11 +82,16 @@ public static void AddAzureDevOpsProvider(this ITestApplicationBuilder builder)
         builder.TestHost.AddDataConsumer(compositeArtifactUploader);
         builder.TestHost.AddDataConsumer(compositeSummaryReporter);
         builder.TestHost.AddDataConsumer(compositeTestResultsPublisher);
+        builder.TestHost.AddDataConsumer(compositeLogGroupReporter);
         builder.TestHost.AddTestSessionLifetimeHandler(serviceProvider =>
             historyService ??= CreateHistoryService(serviceProvider));
         builder.TestHost.AddTestSessionLifetimeHandler(compositeArtifactUploader);
         builder.TestHost.AddTestSessionLifetimeHandler(compositeSummaryReporter);
         builder.TestHost.AddTestSessionLifetimeHandler(compositeTestResultsPublisher);
+
+        // Registered last so its OnTestSessionFinishingAsync (the closing ##[endgroup]) runs after
+        // the other AzDO handlers' finishing callbacks, ensuring the group wraps all their output.
+        builder.TestHost.AddTestSessionLifetimeHandler(compositeLogGroupReporter);
         builder.CommandLine.AddProvider(() => new AzureDevOpsCommandLineProvider());
     }
 
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsLogGroupReporter.cs b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsLogGroupReporter.cs
new file mode 100644
index 0000000000..8f6521b2f7
--- /dev/null
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/AzureDevOpsLogGroupReporter.cs
@@ -0,0 +1,131 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Testing.Extensions.AzureDevOpsReport.Resources;
+using Microsoft.Testing.Extensions.Reporting;
+using Microsoft.Testing.Platform.CommandLine;
+using Microsoft.Testing.Platform.Extensions;
+using Microsoft.Testing.Platform.Extensions.Messages;
+using Microsoft.Testing.Platform.Extensions.OutputDevice;
+using Microsoft.Testing.Platform.Extensions.TestHost;
+using Microsoft.Testing.Platform.Helpers;
+using Microsoft.Testing.Platform.Logging;
+using Microsoft.Testing.Platform.OutputDevice;
+using Microsoft.Testing.Platform.Services;
+
+namespace Microsoft.Testing.Extensions.AzureDevOpsReport;
+
+/// <summary>
+/// Wraps each test assembly's output in an Azure DevOps log group (<c>##[group]</c> /
+/// <c>##[endgroup]</c>) so the raw pipeline log view collapses the assembly's test output by
+/// default. Unlike <c>##vso[task.logdetail]</c> records, the <c>##[group]</c> format commands are
+/// rendered by the modern Azure DevOps Pipelines log viewer.
+/// </summary>
+/// <remarks>
+/// This handler also implements <see cref="IDataConsumer"/> (with a no-op
+/// <see cref="ConsumeAsync(IDataProducer, IData, CancellationToken)"/>) purely so that, at session
+/// end, <c>CommonTestHost.NotifyTestSessionEndAsync</c> runs its
+/// <see cref="OnTestSessionFinishingAsync(ITestSessionContext)"/> in the consumer phase — i.e.
+/// after the producer-only AzDO handlers. Combined with registering it last, this ensures the
+/// closing <c>##[endgroup]</c> is emitted after the other reporters' final <c>##vso[...]</c> lines,
+/// so the group truly wraps the whole assembly's output.
+/// </remarks>
+internal sealed class AzureDevOpsLogGroupReporter : IDataConsumer, ITestSessionLifetimeHandler, IOutputDeviceDataProducer
+{
+    private readonly ICommandLineOptions _commandLineOptions;
+    private readonly IEnvironment _environment;
+    private readonly IOutputDevice _outputDevice;
+    private readonly ITestApplicationModuleInfo _testApplicationModuleInfo;
+    private readonly ILogger _logger;
+    private readonly Lazy<string> _targetFrameworkMoniker;
+
+    private bool _groupOpened;
+
+    public AzureDevOpsLogGroupReporter(
+        ICommandLineOptions commandLineOptions,
+        IEnvironment environment,
+        IOutputDevice outputDevice,
+        ITestApplicationModuleInfo testApplicationModuleInfo,
+        ILoggerFactory loggerFactory)
+    {
+        _commandLineOptions = commandLineOptions;
+        _environment = environment;
+        _outputDevice = outputDevice;
+        _testApplicationModuleInfo = testApplicationModuleInfo;
+        _logger = loggerFactory.CreateLogger<AzureDevOpsLogGroupReporter>();
+        _targetFrameworkMoniker = new(TargetFrameworkMonikerHelper.GetTargetFrameworkMoniker);
+    }
+
+    public string Uid => nameof(AzureDevOpsLogGroupReporter);
+
+    public string Version => ExtensionVersion.DefaultSemVer;
+
+    public string DisplayName => AzureDevOpsResources.DisplayName;
+
+    public string Description => AzureDevOpsResources.Description;
+
+    public Type[] DataTypesConsumed { get; } = [typeof(TestNodeUpdateMessage)];
+
+    public Task<bool> IsEnabledAsync()
+        => Task.FromResult(
+            _commandLineOptions.IsOptionSet(AzureDevOpsCommandLineOptions.AzureDevOpsOptionName)
+            && AzureDevOpsConstants.IsRunningInAzureDevOps(_environment));
+
+    // No-op: this consumer subscribes to data only to be ordered in the consumer phase at session
+    // end (see the type-level remarks). It does not act on individual messages.
+    public Task ConsumeAsync(IDataProducer dataProducer, IData value, CancellationToken cancellationToken)
+        => Task.CompletedTask;
+
+    public async Task OnTestSessionStartingAsync(ITestSessionContext testSessionContext)
+    {
+        try
+        {
+            testSessionContext.CancellationToken.ThrowIfCancellationRequested();
+
+            string name = $"{_testApplicationModuleInfo.TryGetAssemblyName() ?? "unknown"} ({_targetFrameworkMoniker.Value})";
+            string line = $"##[group]{AzDoEscaper.Escape(string.Format(CultureInfo.InvariantCulture, AzureDevOpsResources.LogGroupHeader, name))}";
+            await _outputDevice.DisplayAsync(this, new FormattedTextOutputDeviceData(line), testSessionContext.CancellationToken).ConfigureAwait(false);
+            _groupOpened = true;
+        }
+        catch (OperationCanceledException)
+        {
+            throw;
+        }
+        catch (Exception ex)
+        {
+            LogUnexpectedException(nameof(OnTestSessionStartingAsync), ex);
+        }
+    }
+
+    public async Task OnTestSessionFinishingAsync(ITestSessionContext testSessionContext)
+    {
+        try
+        {
+            testSessionContext.CancellationToken.ThrowIfCancellationRequested();
+
+            if (!_groupOpened)
+            {
+                return;
+            }
+
+            await _outputDevice.DisplayAsync(this, new FormattedTextOutputDeviceData("##[endgroup]"), testSessionContext.CancellationToken).ConfigureAwait(false);
+            _groupOpened = false;
+        }
+        catch (OperationCanceledException)
+        {
+            throw;
+        }
+        catch (Exception ex)
+        {
+            LogUnexpectedException(nameof(OnTestSessionFinishingAsync), ex);
+        }
+    }
+
+    private void LogUnexpectedException(string callbackName, Exception ex)
+    {
+        if (_logger.IsEnabled(LogLevel.Warning))
+        {
+            _logger.LogWarning($"Unexpected exception in {callbackName}: {ex}");
+        }
+    }
+}
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/AzureDevOpsResources.resx b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/AzureDevOpsResources.resx
index 0f774cfab3..d3c20a64ce 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/AzureDevOpsResources.resx
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/AzureDevOpsResources.resx
@@ -270,6 +270,10 @@
     <value>Invalid '--report-azdo-stackframe-filter' regex '{0}': {1}</value>
     <comment>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</comment>
   </data>
+  <data name="LogGroupHeader" xml:space="preserve">
+    <value>Tests: {0}</value>
+    <comment>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</comment>
+  </data>
   <data name="NoFailureMessageFallback" xml:space="preserve">
     <value>Test failed without an additional message.</value>
   </data>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.cs.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.cs.xlf
index 65c13874e3..6620341d6a 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.cs.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.cs.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Neplatný regulární výraz --report-azdo-stackframe-filter {0}: {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">Test neproběhl úspěšně bez další zprávy.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.de.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.de.xlf
index 49362818aa..47e25b8e5c 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.de.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.de.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Ungültiger „--report-azdo-stackframe-filter“ RegEx „{0}“: {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">Fehler beim Test ohne zusätzliche Meldung.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.es.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.es.xlf
index 691f8b9733..ce0f94dd73 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.es.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.es.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Expresión regular no válida de "--report-azdo-stackframe-filter" "{0}": {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">Error en la prueba sin un mensaje adicional.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.fr.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.fr.xlf
index df1ca42d1a..d853bceffd 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.fr.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.fr.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Expression régulière « {0} » non valide pour « --report-azdo-stackframe-filter » : {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">Le test a échoué sans message supplémentaire.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.it.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.it.xlf
index 433c4c749e..f33258fcf0 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.it.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.it.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Espressione regolare non valida per "--report-azdo-stackframe-filter" "{0}": {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">Test non riuscito senza un messaggio aggiuntivo.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ja.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ja.xlf
index 2b24e2c20a..4906a1ef6a 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ja.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ja.xlf
@@ -207,6 +207,11 @@
         <target state="translated">無効 '--report-azdo-stackframe-filter' regex '{0}': {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">追加のメッセージなしでテストに失敗しました。</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ko.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ko.xlf
index bd8d251afd..47ee030429 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ko.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ko.xlf
@@ -207,6 +207,11 @@
         <target state="translated">잘못된 '--report-azdo-stackframe-filter' 정규식 '{0}': {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">추가 메시지 없이 테스트가 실패했습니다.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.pl.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.pl.xlf
index 6634b89911..081222c1b6 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.pl.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.pl.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Nieprawidłowy wyrażenie regularne „--report-azdo-stackframe-filter” „{0}”: {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">Test nie powiódł się bez dodatkowego komunikatu.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.pt-BR.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.pt-BR.xlf
index e7e8685919..aaf4310fee 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.pt-BR.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.pt-BR.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Regex '--report-azdo-stackframe-filter' inválida '{0}': {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">O teste falhou sem uma mensagem adicional.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ru.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ru.xlf
index 0e8288a7d5..2891a49255 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ru.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.ru.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Недопустимое регулярное выражение "--report-azdo-stackframe-filter" "{0}": {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">Тест завершился сбоем без дополнительного сообщения.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.tr.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.tr.xlf
index bf2eb2d4f2..bbbfe62932 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.tr.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.tr.xlf
@@ -207,6 +207,11 @@
         <target state="translated">Geçersiz '--report-azdo-stackframe-filter' normal ifade '{0}': {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">Ek bir ileti olmadan test başarısız oldu.</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.zh-Hans.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.zh-Hans.xlf
index 84289d4d69..54101a00e0 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.zh-Hans.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.zh-Hans.xlf
@@ -207,6 +207,11 @@
         <target state="translated">'--report-azdo-stackframe-filter' 正则表达式 '{0}' 无效: {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">测试失败，无附加消息。</target>
diff --git a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.zh-Hant.xlf b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.zh-Hant.xlf
index 10d07f8c3f..fbcec24885 100644
--- a/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.zh-Hant.xlf
+++ b/src/Platform/Microsoft.Testing.Extensions.AzureDevOpsReport/Resources/xlf/AzureDevOpsResources.zh-Hant.xlf
@@ -207,6 +207,11 @@
         <target state="translated">無效的 '--report-azdo-stackframe-filter' regex '{0}': {1}</target>
         <note>{0} is the regex pattern. {1} is the validation error message. {Locked="--report-azdo-stackframe-filter"}</note>
       </trans-unit>
+      <trans-unit id="LogGroupHeader">
+        <source>Tests: {0}</source>
+        <target state="new">Tests: {0}</target>
+        <note>{0} is the test assembly name and target framework, e.g. 'MSTest.UnitTests (net9.0)'. This text is the collapsible Azure DevOps log group header.</note>
+      </trans-unit>
       <trans-unit id="NoFailureMessageFallback">
         <source>Test failed without an additional message.</source>
         <target state="translated">測試失敗，沒有其他訊息。</target>
diff --git a/test/UnitTests/Microsoft.Testing.Extensions.UnitTests/AzureDevOpsLogGroupReporterTests.cs b/test/UnitTests/Microsoft.Testing.Extensions.UnitTests/AzureDevOpsLogGroupReporterTests.cs
new file mode 100644
index 0000000000..4e9d2826a3
--- /dev/null
+++ b/test/UnitTests/Microsoft.Testing.Extensions.UnitTests/AzureDevOpsLogGroupReporterTests.cs
@@ -0,0 +1,148 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using Microsoft.Testing.Extensions.AzureDevOpsReport;
+using Microsoft.Testing.Extensions.AzureDevOpsReport.Resources;
+using Microsoft.Testing.Extensions.Reporting;
+using Microsoft.Testing.Extensions.UnitTests.Helpers;
+using Microsoft.Testing.Platform.Extensions;
+using Microsoft.Testing.Platform.Extensions.Messages;
+using Microsoft.Testing.Platform.Extensions.OutputDevice;
+using Microsoft.Testing.Platform.Helpers;
+using Microsoft.Testing.Platform.Logging;
+using Microsoft.Testing.Platform.OutputDevice;
+using Microsoft.Testing.Platform.Services;
+using Microsoft.Testing.Platform.TestHost;
+
+using Moq;
+
+namespace Microsoft.Testing.Extensions.UnitTests;
+
+[TestClass]
+public sealed class AzureDevOpsLogGroupReporterTests
+{
+    private readonly Mock<IEnvironment> _environmentMock = new();
+    private readonly Mock<IOutputDevice> _outputDeviceMock = new();
+    private readonly Mock<ITestApplicationModuleInfo> _testApplicationModuleInfoMock = new();
+    private readonly Mock<ILoggerFactory> _loggerFactoryMock = new();
+    private readonly List<IOutputDeviceData> _outputData = [];
+
+    public AzureDevOpsLogGroupReporterTests()
+    {
+        _ = _testApplicationModuleInfoMock.Setup(info => info.TryGetAssemblyName()).Returns("MyAssembly");
+        _ = _loggerFactoryMock.Setup(loggerFactory => loggerFactory.CreateLogger(It.IsAny<string>())).Returns(Mock.Of<ILogger>());
+        _ = _outputDeviceMock
+            .Setup(outputDevice => outputDevice.DisplayAsync(It.IsAny<IOutputDeviceDataProducer>(), It.IsAny<IOutputDeviceData>(), It.IsAny<CancellationToken>()))
+            .Callback<IOutputDeviceDataProducer, IOutputDeviceData, CancellationToken>((_, data, _) => _outputData.Add(data))
+            .Returns(Task.CompletedTask);
+    }
+
+    [TestMethod]
+    public async Task IsEnabledAsync_ReturnsFalse_WhenAzureDevOpsOptionNotSetAsync()
+    {
+        AzureDevOpsLogGroupReporter reporter = CreateReporter(enabled: false, tfBuild: true);
+        Assert.IsFalse(await reporter.IsEnabledAsync());
+    }
+
+    [TestMethod]
+    public async Task IsEnabledAsync_ReturnsFalse_WhenTfBuildNotSetAsync()
+    {
+        AzureDevOpsLogGroupReporter reporter = CreateReporter(enabled: true, tfBuild: false);
+        Assert.IsFalse(await reporter.IsEnabledAsync());
+    }
+
+    [TestMethod]
+    public async Task IsEnabledAsync_ReturnsTrue_WhenAzureDevOpsOptionSetAndTfBuildSetAsync()
+    {
+        AzureDevOpsLogGroupReporter reporter = CreateReporter(enabled: true, tfBuild: true);
+        Assert.IsTrue(await reporter.IsEnabledAsync());
+    }
+
+    [TestMethod]
+    public async Task SessionStarting_EmitsGroupHeaderWithAssemblyAndTfmAsync()
+    {
+        AzureDevOpsLogGroupReporter reporter = CreateReporter(enabled: true, tfBuild: true);
+
+        await reporter.OnTestSessionStartingAsync(new TestSessionContext());
+
+        string[] lines = GetFormattedLines();
+        Assert.HasCount(1, lines);
+        string headerPrefix = AzureDevOpsResources.LogGroupHeader.Replace("{0}", string.Empty);
+        Assert.StartsWith($"##[group]{headerPrefix}MyAssembly (", lines[0]);
+    }
+
+    [TestMethod]
+    public async Task SessionFinishing_EmitsEndGroup_WhenGroupWasOpenedAsync()
+    {
+        AzureDevOpsLogGroupReporter reporter = CreateReporter(enabled: true, tfBuild: true);
+
+        await reporter.OnTestSessionStartingAsync(new TestSessionContext());
+        await reporter.OnTestSessionFinishingAsync(new TestSessionContext());
+
+        string[] lines = GetFormattedLines();
+        Assert.HasCount(2, lines);
+        Assert.StartsWith("##[group]", lines[0]);
+        Assert.AreEqual("##[endgroup]", lines[1]);
+    }
+
+    [TestMethod]
+    public async Task SessionFinishing_DoesNothing_WhenGroupWasNeverOpenedAsync()
+    {
+        AzureDevOpsLogGroupReporter reporter = CreateReporter(enabled: true, tfBuild: true);
+
+        await reporter.OnTestSessionFinishingAsync(new TestSessionContext());
+
+        Assert.IsEmpty(GetFormattedLines());
+    }
+
+    [TestMethod]
+    public async Task ConsumeAsync_IsNoOp_AndEmitsNothingAsync()
+    {
+        // The handler subscribes as an IDataConsumer only to be ordered in the consumer phase at
+        // session end; ConsumeAsync itself must not emit anything.
+        AzureDevOpsLogGroupReporter reporter = CreateReporter(enabled: true, tfBuild: true);
+
+        Assert.Contains(typeof(TestNodeUpdateMessage), reporter.DataTypesConsumed);
+        await reporter.ConsumeAsync(
+            Mock.Of<IDataProducer>(),
+            CreateTestNodeUpdateMessage("t1", new PassedTestNodeStateProperty()),
+            CancellationToken.None);
+
+        Assert.IsEmpty(GetFormattedLines());
+    }
+
+    private static TestNodeUpdateMessage CreateTestNodeUpdateMessage(string uid, TestNodeStateProperty state)
+        => new(
+            new SessionUid("session"),
+            new TestNode
+            {
+                Uid = uid,
+                DisplayName = uid,
+                Properties = new PropertyBag(state),
+            });
+
+    private AzureDevOpsLogGroupReporter CreateReporter(bool enabled, bool tfBuild)
+    {
+        Dictionary<string, string[]> options = enabled
+            ? new Dictionary<string, string[]> { [AzureDevOpsCommandLineOptions.AzureDevOpsOptionName] = [] }
+            : [];
+        _ = _environmentMock.Setup(e => e.GetEnvironmentVariable(AzureDevOpsConstants.TfBuildEnvironmentVariableName))
+            .Returns(tfBuild ? AzureDevOpsConstants.TfBuildEnabledValue : null);
+        return new AzureDevOpsLogGroupReporter(
+            new TestCommandLineOptions(options),
+            _environmentMock.Object,
+            _outputDeviceMock.Object,
+            _testApplicationModuleInfoMock.Object,
+            _loggerFactoryMock.Object);
+    }
+
+    private string[] GetFormattedLines()
+        => [.. _outputData.OfType<FormattedTextOutputDeviceData>().Select(output => output.Text)];
+
+    private sealed class TestSessionContext : ITestSessionContext
+    {
+        public SessionUid SessionUid { get; } = new("session");
+
+        public CancellationToken CancellationToken { get; } = CancellationToken.None;
+    }
+}