.NET: expose OpenTelemetryAgent.DefaultSourceName

docs/decisions/0003-agent-opentelemetry-instrumentation.md

@@ -127,7 +127,7 @@ The implementation is validated through:
 ```csharp
 // Create TracerProvider
 using var tracerProvider = Sdk.CreateTracerProviderBuilder()
-    .AddSource(AgentOpenTelemetryConsts.DefaultSourceName)
+    .AddSource(OpenTelemetryAgent.DefaultSourceName)
     .AddConsoleExporter()
     .Build();
 

dotnet/src/Microsoft.Agents.AI/OpenTelemetryAgent.cs

@@ -41,6 +41,18 @@ public sealed class OpenTelemetryAgent : DelegatingAIAgent, IDisposable
     // inner agent not directly but rather via OpenTelemetryChatClient, which wraps a ForwardingChatClient that in turn
     // calls back into the inner agent.
 
+    /// <summary>
+    /// Gets the default <see cref="ActivitySource"/> name used by <see cref="OpenTelemetryAgent"/> when no source
+    /// name is supplied to the constructor.
+    /// </summary>
+    /// <remarks>
+    /// Pass this value to the tracing pipeline (for example, <c>TracerProviderBuilder.AddSource</c>) to subscribe to
+    /// the spans emitted by agents that use the default source name, instead of hardcoding the literal name. This is
+    /// a property rather than a constant so that the value is read at run time: a consumer that upgrades the package
+    /// picks up the current source name without recompiling.
+    /// </remarks>
+    public static string DefaultSourceName => OpenTelemetryConsts.DefaultSourceName;
+
     /// <summary>The <see cref="OpenTelemetryChatClient"/> providing the bulk of the telemetry.</summary>
     private readonly OpenTelemetryChatClient _otelClient;
     /// <summary>The provider name extracted from <see cref="AIAgentMetadata"/>.</summary>

dotnet/tests/Microsoft.Agents.AI.UnitTests/OpenTelemetryAgentTests.cs

@@ -873,6 +873,17 @@ public async Task AutoWireChatClient_UserFactoryAddsOwnOTel_CoexistsWithBelowFic
         Assert.Equal(2, activities.Count(a => string.Equals(a.GetTagItem("gen_ai.operation.name") as string, "chat", StringComparison.Ordinal)));
     }
 
+    [Fact]
+    public void DefaultSourceName_ReturnsDocumentedSourceName()
+    {
+        // Callers pass this to TracerProviderBuilder.AddSource, so it must stay in sync with the source name the
+        // agent emits spans under, which Ctor_NullOrWhitespaceSourceName_AutoWiredChatClientUsesDefaultSource_Async
+        // pins to the same literal. Comparing against the literal here guards a rename of the internal constant.
+
+        // Arrange & Act & Assert
+        Assert.Equal("Experimental.Microsoft.Agents.AI", OpenTelemetryAgent.DefaultSourceName);
+    }
+
     [Theory]
     [InlineData(null)]
     [InlineData("")]