diff --git a/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Core/DefinitionsBuilder.cs b/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Core/DefinitionsBuilder.cs
index 098e6be96..07ff5c155 100644
--- a/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Core/DefinitionsBuilder.cs
+++ b/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Core/DefinitionsBuilder.cs
@@ -27,6 +27,7 @@ public class DefinitionsBuilder
         {
             "reason",
             "reasonDesc",
+            "source",
             "errorCode",
             "causedBy",
             "httpStatusCode",
@@ -440,6 +441,11 @@ private CodeMemberMethod CreateRecordMetricMethodByDataClass(Metric metric)
             tryStatements.Add(new CodeExpressionStatement(new CodeMethodInvokeExpression(datumAddData,
                 new CodePrimitiveExpression("reasonDesc"), payloadReasonDescription)));
 
+            // Generate: datum.AddMetadata("source", payload.Source);
+            var payloadSource = new CodeFieldReferenceExpression(payload, "Source");
+            tryStatements.Add(new CodeExpressionStatement(new CodeMethodInvokeExpression(datumAddData,
+                new CodePrimitiveExpression("source"), payloadSource)));
+
             // Generate: datum.AddMetadata("errorCode", payload.ErrorCode);
             var payloadErrorCode = new CodeFieldReferenceExpression(payload, "ErrorCode");
             tryStatements.Add(new CodeExpressionStatement(new CodeMethodInvokeExpression(datumAddData,
diff --git a/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Tests/SampleData/Outcomes/sampleDefinitions-generated.txt b/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Tests/SampleData/Outcomes/sampleDefinitions-generated.txt
index 603935b10..4e2ee5726 100644
--- a/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Tests/SampleData/Outcomes/sampleDefinitions-generated.txt
+++ b/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Tests/SampleData/Outcomes/sampleDefinitions-generated.txt
@@ -58,6 +58,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -118,6 +119,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -178,6 +180,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -246,6 +249,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -314,6 +318,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -391,6 +396,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -451,6 +457,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
diff --git a/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Tests/SampleData/Outcomes/sampleDefinitions-supplemental.txt b/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Tests/SampleData/Outcomes/sampleDefinitions-supplemental.txt
index 43c76daa8..c5d70f95f 100644
--- a/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Tests/SampleData/Outcomes/sampleDefinitions-supplemental.txt
+++ b/telemetry/csharp/AwsToolkit.Telemetry.Events.Generator.Tests/SampleData/Outcomes/sampleDefinitions-supplemental.txt
@@ -58,6 +58,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -118,6 +119,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -178,6 +180,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -246,6 +249,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -314,6 +318,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -391,6 +396,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
@@ -451,6 +457,7 @@ namespace Test
                 datum.AddMetadata("awsRegion", payload.AwsRegion);
                 datum.AddMetadata("reason", payload.Reason);
                 datum.AddMetadata("reasonDesc", payload.ReasonDescription);
+                datum.AddMetadata("source", payload.Source);
                 datum.AddMetadata("errorCode", payload.ErrorCode);
                 datum.AddMetadata("causedBy", payload.CausedBy);
                 datum.AddMetadata("httpStatusCode", payload.HttpStatusCode);
diff --git a/telemetry/csharp/AwsToolkit.Telemetry.Events/Core/BaseTelemetryEvent.cs b/telemetry/csharp/AwsToolkit.Telemetry.Events/Core/BaseTelemetryEvent.cs
index ba109c479..71d2aa426 100644
--- a/telemetry/csharp/AwsToolkit.Telemetry.Events/Core/BaseTelemetryEvent.cs
+++ b/telemetry/csharp/AwsToolkit.Telemetry.Events/Core/BaseTelemetryEvent.cs
@@ -38,6 +38,13 @@ public abstract class BaseTelemetryEvent
         /// </summary>
         public string ReasonDescription;
 
+        /// <summary>
+        /// The source of the operation. This answers 'who' caused/triggered the operation.
+        /// Example: did an Auth signout happen because of some expiration or since the user
+        /// explicitly clicked the signout button.
+        /// </summary>
+        public string Source;
+
         /// <summary>
         /// Optional - User-friendly error codes describing a failed operation
         /// This is often used in failure scenarios to provide additional details about why something failed.