diff --git a/Directory.Packages.props b/Directory.Packages.props
index 104dedfd9eaf..abe2e9e23b4c 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -108,6 +108,7 @@
     <PackageVersion Include="System.Composition.Runtime" Version="$(SystemCompositionRuntimePackageVersion)" />
     <PackageVersion Include="System.Composition.TypedParts" Version="$(SystemCompositionTypedPartsPackageVersion)" />
     <PackageVersion Include="System.Configuration.ConfigurationManager" Version="$(SystemConfigurationConfigurationManagerPackageVersion)" />
+    <PackageVersion Include="System.Diagnostics.DiagnosticSource" Version="$(SystemDiagnosticsDiagnosticSourcePackageVersion)" />
     <PackageVersion Include="System.Formats.Asn1" Version="$(SystemFormatsAsn1Version)" />
     <PackageVersion Include="System.IO.Hashing" Version="$(SystemIOHashingPackageVersion)" />
     <!-- System.Reflection.Metadata and System.Collections.Immutable cannot be pinned here because of hard dependencies within Roslyn on specific versions that have to work both here and in VS -->
diff --git a/eng/Versions.props b/eng/Versions.props
index 99e97cedaae8..1b71e21ebfc6 100644
--- a/eng/Versions.props
+++ b/eng/Versions.props
@@ -119,6 +119,7 @@
     <SystemCompositionHostingPackageVersion>10.0.0-preview.7.25359.101</SystemCompositionHostingPackageVersion>
     <SystemCompositionRuntimePackageVersion>10.0.0-preview.7.25359.101</SystemCompositionRuntimePackageVersion>
     <SystemCompositionTypedPartsPackageVersion>10.0.0-preview.7.25359.101</SystemCompositionTypedPartsPackageVersion>
+    <SystemDiagnosticsDiagnosticSourcePackageVersion>10.0.0-preview.7.25359.101</SystemDiagnosticsDiagnosticSourcePackageVersion>
     <SystemConfigurationConfigurationManagerPackageVersion>10.0.0-preview.7.25359.101</SystemConfigurationConfigurationManagerPackageVersion>
     <SystemReflectionMetadataLoadContextVersion>10.0.0-preview.7.25359.101</SystemReflectionMetadataLoadContextVersion>
     <SystemResourcesExtensionsPackageVersion>10.0.0-preview.7.25359.101</SystemResourcesExtensionsPackageVersion>
diff --git a/src/Cli/Microsoft.DotNet.Cli.Utils/Activities.cs b/src/Cli/Microsoft.DotNet.Cli.Utils/Activities.cs
new file mode 100644
index 000000000000..9f4665572436
--- /dev/null
+++ b/src/Cli/Microsoft.DotNet.Cli.Utils/Activities.cs
@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Diagnostics;
+
+namespace Microsoft.DotNet.Cli.Utils;
+
+/// <summary>
+/// Contains helpers for working with <see cref="System.Diagnostics.Activity">Activities</see> in the .NET CLI.
+/// </summary>
+public static class Activities
+{
+
+    /// <summary>
+    /// The main entrypoint for creating <see cref="Activity">Activities</see> in the .NET CLI.
+    /// All activities created in the CLI should use this <see cref="ActivitySource"/>, to allow
+    /// consumers to easily filter and trace CLI activities.
+    /// </summary>
+    public static ActivitySource Source { get; } = new("dotnet-cli", Product.Version);
+}
diff --git a/src/Cli/Microsoft.DotNet.Cli.Utils/ForwardingAppImplementation.cs b/src/Cli/Microsoft.DotNet.Cli.Utils/ForwardingAppImplementation.cs
index f6acb60ea0a1..1b2058d17744 100644
--- a/src/Cli/Microsoft.DotNet.Cli.Utils/ForwardingAppImplementation.cs
+++ b/src/Cli/Microsoft.DotNet.Cli.Utils/ForwardingAppImplementation.cs
@@ -19,7 +19,7 @@ internal class ForwardingAppImplementation
     private readonly string? _depsFile;
     private readonly string? _runtimeConfig;
     private readonly string? _additionalProbingPath;
-    private Dictionary<string, string> _environmentVariables;
+    private Dictionary<string, string?> _environmentVariables;
 
     private readonly string[] _allArgs;
 
@@ -29,7 +29,7 @@ public ForwardingAppImplementation(
         string? depsFile = null,
         string? runtimeConfig = null,
         string? additionalProbingPath = null,
-        Dictionary<string, string>? environmentVariables = null)
+        Dictionary<string, string?>? environmentVariables = null)
     {
         _forwardApplicationPath = forwardApplicationPath;
         _argsToForward = argsToForward;
@@ -86,7 +86,7 @@ public ProcessStartInfo GetProcessStartInfo()
         return processInfo;
     }
 
-    public ForwardingAppImplementation WithEnvironmentVariable(string name, string value)
+    public ForwardingAppImplementation WithEnvironmentVariable(string name, string? value)
     {
         _environmentVariables.Add(name, value);
 
diff --git a/src/Cli/Microsoft.DotNet.Cli.Utils/MSBuildForwardingAppWithoutLogging.cs b/src/Cli/Microsoft.DotNet.Cli.Utils/MSBuildForwardingAppWithoutLogging.cs
index 2e95365623a0..64e6fea0ccf9 100644
--- a/src/Cli/Microsoft.DotNet.Cli.Utils/MSBuildForwardingAppWithoutLogging.cs
+++ b/src/Cli/Microsoft.DotNet.Cli.Utils/MSBuildForwardingAppWithoutLogging.cs
@@ -39,7 +39,7 @@ public static string MSBuildVersion
     // True if, given current state of the class, MSBuild would be executed in its own process.
     public bool ExecuteMSBuildOutOfProc => _forwardingApp != null;
 
-    private readonly Dictionary<string, string> _msbuildRequiredEnvironmentVariables = GetMSBuildRequiredEnvironmentVariables();
+    private readonly Dictionary<string, string?> _msbuildRequiredEnvironmentVariables = GetMSBuildRequiredEnvironmentVariables();
 
     private readonly List<string> _msbuildRequiredParameters = [ "-maxcpucount", "--verbosity:m" ];
 
@@ -112,7 +112,7 @@ private static string EmitProperty(KeyValuePair<string, string> property, string
             : $"--{label}:{property.Key}={property.Value}";
     }
 
-    public void EnvironmentVariable(string name, string value)
+    public void EnvironmentVariable(string name, string? value)
     {
         if (_forwardingApp != null)
         {
@@ -153,7 +153,7 @@ public int ExecuteInProc(string[] arguments)
         Dictionary<string, string?> savedEnvironmentVariables = [];
         try
         {
-            foreach (KeyValuePair<string, string> kvp in _msbuildRequiredEnvironmentVariables)
+            foreach (KeyValuePair<string, string?> kvp in _msbuildRequiredEnvironmentVariables)
             {
                 savedEnvironmentVariables[kvp.Key] = Environment.GetEnvironmentVariable(kvp.Key);
                 Environment.SetEnvironmentVariable(kvp.Key, kvp.Value);
@@ -218,7 +218,7 @@ private static string GetDotnetPath()
         return new Muxer().MuxerPath;
     }
 
-    internal static Dictionary<string, string> GetMSBuildRequiredEnvironmentVariables()
+    internal static Dictionary<string, string?> GetMSBuildRequiredEnvironmentVariables()
     {
         return new()
         {
diff --git a/src/Cli/Microsoft.DotNet.Cli.Utils/Microsoft.DotNet.Cli.Utils.csproj b/src/Cli/Microsoft.DotNet.Cli.Utils/Microsoft.DotNet.Cli.Utils.csproj
index 115f5dd125ec..3c0f616409d4 100644
--- a/src/Cli/Microsoft.DotNet.Cli.Utils/Microsoft.DotNet.Cli.Utils.csproj
+++ b/src/Cli/Microsoft.DotNet.Cli.Utils/Microsoft.DotNet.Cli.Utils.csproj
@@ -54,6 +54,7 @@
     <PackageReference Include="Microsoft.Build" ExcludeAssets="runtime" PrivateAssets="all" />
     <PackageReference Include="Microsoft.Build.Utilities.Core" ExcludeAssets="runtime" PrivateAssets="all" />
     <PackageReference Include="System.CommandLine" />
+    <PackageReference Include="System.Diagnostics.DiagnosticSource" />
     <PackageReference Include="System.IO.Hashing" />
   </ItemGroup>
 
diff --git a/src/Cli/dotnet/Commands/MSBuild/MSBuildForwardingApp.cs b/src/Cli/dotnet/Commands/MSBuild/MSBuildForwardingApp.cs
index f3ef9d93a44f..67c2a47f1051 100644
--- a/src/Cli/dotnet/Commands/MSBuild/MSBuildForwardingApp.cs
+++ b/src/Cli/dotnet/Commands/MSBuild/MSBuildForwardingApp.cs
@@ -59,7 +59,7 @@ public MSBuildForwardingApp(MSBuildArgs msBuildArgs, string? msbuildPath = null,
 
     public IEnumerable<string> MSBuildArguments { get { return _forwardingAppWithoutLogging.GetAllArguments(); } }
 
-    public void EnvironmentVariable(string name, string value)
+    public void EnvironmentVariable(string name, string? value)
     {
         _forwardingAppWithoutLogging.EnvironmentVariable(name, value);
     }
diff --git a/src/Cli/dotnet/Telemetry/Telemetry.cs b/src/Cli/dotnet/Telemetry/Telemetry.cs
index 28851da921b1..f908d01e7fe0 100644
--- a/src/Cli/dotnet/Telemetry/Telemetry.cs
+++ b/src/Cli/dotnet/Telemetry/Telemetry.cs
@@ -1,8 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-#nullable disable
-
+using System.Collections.Frozen;
 using System.Diagnostics;
 using Microsoft.ApplicationInsights;
 using Microsoft.ApplicationInsights.Extensibility;
@@ -14,13 +13,13 @@ namespace Microsoft.DotNet.Cli.Telemetry;
 
 public class Telemetry : ITelemetry
 {
-    internal static string CurrentSessionId = null;
+    internal static string? CurrentSessionId = null;
     internal static bool DisabledForTests = false;
     private readonly int _senderCount;
-    private TelemetryClient _client = null;
-    private Dictionary<string, string> _commonProperties = null;
-    private Dictionary<string, double> _commonMeasurements = null;
-    private Task _trackEventTask = null;
+    private TelemetryClient? _client = null;
+    private FrozenDictionary<string, string>? _commonProperties = null;
+    private FrozenDictionary<string, double>? _commonMeasurements = null;
+    private Task? _trackEventTask = null;
 
     private const string ConnectionString = "InstrumentationKey=74cc1c9e-3e6e-4d05-b3fc-dde9101d0254";
 
@@ -28,13 +27,13 @@ public class Telemetry : ITelemetry
 
     public Telemetry() : this(null) { }
 
-    public Telemetry(IFirstTimeUseNoticeSentinel sentinel) : this(sentinel, null) { }
+    public Telemetry(IFirstTimeUseNoticeSentinel? sentinel) : this(sentinel, null) { }
 
     public Telemetry(
-        IFirstTimeUseNoticeSentinel sentinel,
-        string sessionId,
+        IFirstTimeUseNoticeSentinel? sentinel,
+        string? sessionId,
         bool blockThreadInitialization = false,
-        IEnvironmentProvider environmentProvider = null,
+        IEnvironmentProvider? environmentProvider = null,
         int senderCount = 3)
     {
 
@@ -78,7 +77,7 @@ internal static void EnableForTests()
         DisabledForTests = false;
     }
 
-    private static bool PermissionExists(IFirstTimeUseNoticeSentinel sentinel)
+    private static bool PermissionExists(IFirstTimeUseNoticeSentinel? sentinel)
     {
         if (sentinel == null)
         {
@@ -97,9 +96,17 @@ public void TrackEvent(string eventName, IDictionary<string, string> properties,
         }
 
         //continue the task in different threads
-        _trackEventTask = _trackEventTask.ContinueWith(
-            x => TrackEventTask(eventName, properties, measurements)
-        );
+        if (_trackEventTask == null)
+        {
+            _trackEventTask = Task.Run(() => TrackEventTask(eventName, properties, measurements));
+            return;
+        }
+        else
+        {
+            _trackEventTask = _trackEventTask.ContinueWith(
+                x => TrackEventTask(eventName, properties, measurements)
+            );
+        }
     }
 
     public void Flush()
@@ -148,7 +155,7 @@ private void InitializeTelemetry()
             _client.Context.Device.OperatingSystem = CLIRuntimeEnvironment.OperatingSystem;
 
             _commonProperties = new TelemetryCommonProperties().GetTelemetryCommonProperties();
-            _commonMeasurements = [];
+            _commonMeasurements = FrozenDictionary<string, double>.Empty;
         }
         catch (Exception e)
         {
@@ -170,12 +177,14 @@ private void TrackEventTask(
 
         try
         {
-            Dictionary<string, string> eventProperties = GetEventProperties(properties);
-            Dictionary<string, double> eventMeasurements = GetEventMeasures(measurements);
+            var eventProperties = GetEventProperties(properties);
+            var eventMeasurements = GetEventMeasures(measurements);
 
+            eventProperties ??= new Dictionary<string, string>();
             eventProperties.Add("event id", Guid.NewGuid().ToString());
 
             _client.TrackEvent(PrependProducerNamespace(eventName), eventProperties, eventMeasurements);
+            Activity.Current?.AddEvent(CreateActivityEvent(eventName, eventProperties, eventMeasurements));
         }
         catch (Exception e)
         {
@@ -183,26 +192,69 @@ private void TrackEventTask(
         }
     }
 
-    private static string PrependProducerNamespace(string eventName)
+    private static ActivityEvent CreateActivityEvent(
+        string eventName,
+        IDictionary<string, string>? properties,
+        IDictionary<string, double>? measurements)
     {
-        return "dotnet/cli/" + eventName;
+        var tags = MakeTags(properties, measurements);
+        return new ActivityEvent(
+            PrependProducerNamespace(eventName),
+            tags: tags);
     }
 
-    private Dictionary<string, double> GetEventMeasures(IDictionary<string, double> measurements)
+    private static ActivityTagsCollection? MakeTags(
+        IDictionary<string, string>? properties,
+        IDictionary<string, double>? measurements)
     {
-        Dictionary<string, double> eventMeasurements = new(_commonMeasurements);
-        if (measurements != null)
+        if (properties == null && measurements == null)
         {
-            foreach (KeyValuePair<string, double> measurement in measurements)
-            {
-                eventMeasurements[measurement.Key] = measurement.Value;
-            }
+            return null;
+        }
+        else if (properties != null && measurements == null)
+        {
+            return [.. properties.Select(p => new KeyValuePair<string, object?>(p.Key, p.Value))];
+        }
+        else if (properties == null && measurements != null)
+        {
+            return [.. measurements.Select(m => new KeyValuePair<string, object?>(m.Key, m.Value.ToString()))];
+        }
+        else return [ .. properties!.Select(p => new KeyValuePair<string, object?>(p.Key, p.Value)),
+                 .. measurements!.Select(m => new KeyValuePair<string, object?>(m.Key, m.Value.ToString())) ];
+    }
+
+    private static string PrependProducerNamespace(string eventName) => $"dotnet/cli/{eventName}";
+
+    private IDictionary<string, double>? GetEventMeasures(IDictionary<string, double>? measurements)
+    {
+        if (measurements is null)
+        {
+            return _commonMeasurements;
+        }
+        if (_commonMeasurements == null)
+        {
+            return measurements;
+        }
+
+        IDictionary<string, double> eventMeasurements = new Dictionary<string, double>(_commonMeasurements);
+        foreach (KeyValuePair<string, double> measurement in measurements)
+        {
+            eventMeasurements[measurement.Key] = measurement.Value;
         }
         return eventMeasurements;
     }
 
-    private Dictionary<string, string> GetEventProperties(IDictionary<string, string> properties)
+    private IDictionary<string, string>? GetEventProperties(IDictionary<string, string>? properties)
     {
+        if (properties is null)
+        {
+            return _commonProperties;
+        }
+        if (_commonProperties == null)
+        {
+            return properties;
+        }
+
         var eventProperties = new Dictionary<string, string>(_commonProperties);
         if (properties != null)
         {
diff --git a/src/Cli/dotnet/Telemetry/TelemetryCommonProperties.cs b/src/Cli/dotnet/Telemetry/TelemetryCommonProperties.cs
index 88b2c2152100..9f58d488a12c 100644
--- a/src/Cli/dotnet/Telemetry/TelemetryCommonProperties.cs
+++ b/src/Cli/dotnet/Telemetry/TelemetryCommonProperties.cs
@@ -3,6 +3,7 @@
 
 #nullable disable
 
+using System.Collections.Frozen;
 using Microsoft.DotNet.Cli.Utils;
 using Microsoft.DotNet.Configurer;
 using RuntimeEnvironment = Microsoft.DotNet.Cli.Utils.RuntimeEnvironment;
@@ -52,7 +53,7 @@ internal class TelemetryCommonProperties(
     private const string MachineIdCacheKey = "MachineId";
     private const string IsDockerContainerCacheKey = "IsDockerContainer";
 
-    public Dictionary<string, string> GetTelemetryCommonProperties()
+    public FrozenDictionary<string, string> GetTelemetryCommonProperties()
     {
         return new Dictionary<string, string>
         {
@@ -82,7 +83,7 @@ public Dictionary<string, string> GetTelemetryCommonProperties()
             {ProductType, ExternalTelemetryProperties.GetProductType()},
             {LibcRelease, ExternalTelemetryProperties.GetLibcRelease()},
             {LibcVersion, ExternalTelemetryProperties.GetLibcVersion()}
-        };
+        }.ToFrozenDictionary(StringComparer.OrdinalIgnoreCase);
     }
 
     private string GetMachineId()