.NET: [BREAKING] Update message source code to match python. (#3805)

* Update message source code to match python. * Apply suggestion from @Copilot Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Address PR comment * Move setting of source information to extension method * Add underscore for attribution key to indicate internal usage * Stick to version 102 of the SDK since 103 is causing issues. * Revert global.json change * Fix unit test --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
2026-06-16 21:04:09 +08:00 · 2026-02-10 19:21:18 +00:00
parent 7e7d72275d
commit 7dccf3a07b
19 changed files with 1084 additions and 276 deletions
@@ -19,7 +19,7 @@ public class AIContextProviderTests
    #region InvokingAsync Message Stamping Tests

    [Fact]
-    public async Task InvokingAsync_StampsMessagesWithSourceTypeAndSourceAsync()
+    public async Task InvokingAsync_StampsMessagesWithSourceTypeAndSourceIdAsync()
    {
        // Arrange
        var provider = new TestAIContextProviderWithMessages();
@@ -32,18 +32,18 @@ public class AIContextProviderTests
        Assert.NotNull(aiContext.Messages);
        ChatMessage message = aiContext.Messages.Single();
        Assert.NotNull(message.AdditionalProperties);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceType.AdditionalPropertiesKey, out object? sourceType));
-        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, sourceType);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSource.AdditionalPropertiesKey, out object? source));
-        Assert.Equal(typeof(TestAIContextProviderWithMessages).FullName, source);
+        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, out object? attribution));
+        var typedAttribution = Assert.IsType<AgentRequestMessageSourceAttribution>(attribution);
+        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, typedAttribution.SourceType);
+        Assert.Equal(typeof(TestAIContextProviderWithMessages).FullName, typedAttribution.SourceId);
    }

    [Fact]
-    public async Task InvokingAsync_WithCustomSourceName_StampsMessagesWithCustomSourceAsync()
+    public async Task InvokingAsync_WithCustomSourceId_StampsMessagesWithCustomSourceIdAsync()
    {
        // Arrange
-        const string CustomSourceName = "CustomContextSource";
-        var provider = new TestAIContextProviderWithCustomSource(CustomSourceName);
+        const string CustomSourceId = "CustomContextSource";
+        var provider = new TestAIContextProviderWithCustomSource(CustomSourceId);
        var context = new AIContextProvider.InvokingContext(s_mockAgent, s_mockSession, [new ChatMessage(ChatRole.User, "Request")]);

        // Act
@@ -53,10 +53,10 @@ public class AIContextProviderTests
        Assert.NotNull(aiContext.Messages);
        ChatMessage message = aiContext.Messages.Single();
        Assert.NotNull(message.AdditionalProperties);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceType.AdditionalPropertiesKey, out object? sourceType));
-        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, sourceType);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSource.AdditionalPropertiesKey, out object? source));
-        Assert.Equal(CustomSourceName, source);
+        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, out object? attribution));
+        var typedAttribution = Assert.IsType<AgentRequestMessageSourceAttribution>(attribution);
+        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, typedAttribution.SourceType);
+        Assert.Equal(CustomSourceId, typedAttribution.SourceId);
    }

    [Fact]
@@ -73,10 +73,10 @@ public class AIContextProviderTests
        Assert.NotNull(aiContext.Messages);
        ChatMessage message = aiContext.Messages.Single();
        Assert.NotNull(message.AdditionalProperties);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceType.AdditionalPropertiesKey, out object? sourceType));
-        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, sourceType);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSource.AdditionalPropertiesKey, out object? source));
-        Assert.Equal(typeof(TestAIContextProviderWithPreStampedMessages).FullName, source);
+        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, out object? attribution));
+        var typedAttribution = Assert.IsType<AgentRequestMessageSourceAttribution>(attribution);
+        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, typedAttribution.SourceType);
+        Assert.Equal(typeof(TestAIContextProviderWithPreStampedMessages).FullName, typedAttribution.SourceId);
    }

    [Fact]
@@ -97,10 +97,10 @@ public class AIContextProviderTests
        foreach (ChatMessage message in messageList)
        {
            Assert.NotNull(message.AdditionalProperties);
-            Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceType.AdditionalPropertiesKey, out object? sourceType));
-            Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, sourceType);
-            Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSource.AdditionalPropertiesKey, out object? source));
-            Assert.Equal(typeof(TestAIContextProviderWithMultipleMessages).FullName, source);
+            Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, out object? attribution));
+            var typedAttribution = Assert.IsType<AgentRequestMessageSourceAttribution>(attribution);
+            Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, typedAttribution.SourceType);
+            Assert.Equal(typeof(TestAIContextProviderWithMultipleMessages).FullName, typedAttribution.SourceId);
        }
    }

@@ -486,7 +486,7 @@ public class AIContextProviderTests

    private sealed class TestAIContextProviderWithCustomSource : AIContextProvider
    {
-        public TestAIContextProviderWithCustomSource(string sourceName) : base(sourceName)
+        public TestAIContextProviderWithCustomSource(string sourceId) : base(sourceId)
        {
        }

@@ -504,8 +504,7 @@ public class AIContextProviderTests
            var message = new ChatMessage(ChatRole.System, "Pre-stamped Message");
            message.AdditionalProperties = new AdditionalPropertiesDictionary
            {
-                [AgentRequestMessageSourceType.AdditionalPropertiesKey] = AgentRequestMessageSourceType.AIContextProvider,
-                [AgentRequestMessageSource.AdditionalPropertiesKey] = this.GetType().FullName!
+                [AgentRequestMessageSourceAttribution.AdditionalPropertiesKey] = new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.AIContextProvider, this.GetType().FullName!)
            };
            return new(new AIContext
            {
@@ -0,0 +1,466 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+namespace Microsoft.Agents.AI.Abstractions.UnitTests;
+
+/// <summary>
+/// Contains tests for the <see cref="AgentRequestMessageSourceAttribution"/> struct.
+/// </summary>
+public sealed class AgentRequestMessageSourceAttributionTests
+{
+    #region Constructor Tests
+
+    [Fact]
+    public void Constructor_SetsSourceTypeAndSourceId()
+    {
+        // Arrange
+        AgentRequestMessageSourceType expectedType = AgentRequestMessageSourceType.AIContextProvider;
+        const string ExpectedId = "MyProvider";
+
+        // Act
+        AgentRequestMessageSourceAttribution attribution = new(expectedType, ExpectedId);
+
+        // Assert
+        Assert.Equal(expectedType, attribution.SourceType);
+        Assert.Equal(ExpectedId, attribution.SourceId);
+    }
+
+    [Fact]
+    public void Constructor_WithNullSourceId_SetsNullSourceId()
+    {
+        // Arrange
+        AgentRequestMessageSourceType sourceType = AgentRequestMessageSourceType.ChatHistory;
+
+        // Act
+        AgentRequestMessageSourceAttribution attribution = new(sourceType, null);
+
+        // Assert
+        Assert.Equal(sourceType, attribution.SourceType);
+        Assert.Null(attribution.SourceId);
+    }
+
+    #endregion
+
+    #region AdditionalPropertiesKey Tests
+
+    [Fact]
+    public void AdditionalPropertiesKey_IsAttribution()
+    {
+        // Assert
+        Assert.Equal("_attribution", AgentRequestMessageSourceAttribution.AdditionalPropertiesKey);
+    }
+
+    #endregion
+
+    #region Default Value Tests
+
+    [Fact]
+    public void Default_HasDefaultSourceTypeAndNullSourceId()
+    {
+        // Arrange & Act
+        AgentRequestMessageSourceAttribution attribution = default;
+
+        // Assert
+        Assert.Equal(default, attribution.SourceType);
+        Assert.Null(attribution.SourceId);
+    }
+
+    #endregion
+
+    #region Equals (IEquatable) Tests
+
+    [Fact]
+    public void Equals_WithSameSourceTypeAndSourceId_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void Equals_WithDifferentSourceType_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.ChatHistory, "Provider1");
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void Equals_WithDifferentSourceId_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider2");
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void Equals_WithDifferentSourceTypeAndSourceId_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.ChatHistory, "Provider2");
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void Equals_WithDifferentCaseSourceId_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "provider");
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void Equals_BothDefaultValues_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = default;
+        AgentRequestMessageSourceAttribution attribution2 = default;
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void Equals_WithBothNullSourceIds_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.External, null!);
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.External, null!);
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void Equals_WithOneNullSourceId_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.External, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.External, null!);
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.False(result);
+    }
+
+    #endregion
+
+    #region Object.Equals Tests
+
+    [Fact]
+    public void ObjectEquals_WithEqualAttribution_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.ChatHistory, "Provider");
+        object attribution2 = new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "Provider");
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void ObjectEquals_WithDifferentType_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution = new(AgentRequestMessageSourceType.ChatHistory, "Provider");
+        object other = "NotAnAttribution";
+
+        // Act
+        bool result = attribution.Equals(other);
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void ObjectEquals_WithNullObject_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution = new(AgentRequestMessageSourceType.ChatHistory, "Provider");
+        object? other = null;
+
+        // Act
+        bool result = attribution.Equals(other);
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void ObjectEquals_WithBoxedDifferentAttribution_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.ChatHistory, "Provider1");
+        object attribution2 = new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "Provider2");
+
+        // Act
+        bool result = attribution1.Equals(attribution2);
+
+        // Assert
+        Assert.False(result);
+    }
+
+    #endregion
+
+    #region GetHashCode Tests
+
+    [Fact]
+    public void GetHashCode_WithSameValues_ReturnsSameHashCode()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+
+        // Act
+        int hashCode1 = attribution1.GetHashCode();
+        int hashCode2 = attribution2.GetHashCode();
+
+        // Assert
+        Assert.Equal(hashCode1, hashCode2);
+    }
+
+    [Fact]
+    public void GetHashCode_WithDifferentSourceType_ReturnsDifferentHashCode()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.ChatHistory, "Provider");
+
+        // Act
+        int hashCode1 = attribution1.GetHashCode();
+        int hashCode2 = attribution2.GetHashCode();
+
+        // Assert
+        Assert.NotEqual(hashCode1, hashCode2);
+    }
+
+    [Fact]
+    public void GetHashCode_WithDifferentSourceId_ReturnsDifferentHashCode()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider2");
+
+        // Act
+        int hashCode1 = attribution1.GetHashCode();
+        int hashCode2 = attribution2.GetHashCode();
+
+        // Assert
+        Assert.NotEqual(hashCode1, hashCode2);
+    }
+
+    [Fact]
+    public void GetHashCode_ConsistentWithEquals()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.External, "Provider");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.External, "Provider");
+
+        // Act & Assert
+        Assert.True(attribution1.Equals(attribution2));
+        Assert.Equal(attribution1.GetHashCode(), attribution2.GetHashCode());
+    }
+
+    [Fact]
+    public void GetHashCode_WithNullSourceId_DoesNotThrow()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution = new(AgentRequestMessageSourceType.External, null!);
+
+        // Act
+        int hashCode = attribution.GetHashCode();
+
+        // Assert
+        Assert.IsType<int>(hashCode);
+    }
+
+    #endregion
+
+    #region Equality Operator Tests
+
+    [Fact]
+    public void EqualityOperator_WithEqualValues_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+
+        // Act
+        bool result = attribution1 == attribution2;
+
+        // Assert
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void EqualityOperator_WithDifferentValues_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.ChatHistory, "Provider2");
+
+        // Act
+        bool result = attribution1 == attribution2;
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void EqualityOperator_WithBothDefault_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = default;
+        AgentRequestMessageSourceAttribution attribution2 = default;
+
+        // Act
+        bool result = attribution1 == attribution2;
+
+        // Assert
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void EqualityOperator_WithDifferentSourceTypeOnly_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.External, "Provider");
+
+        // Act
+        bool result = attribution1 == attribution2;
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void EqualityOperator_WithDifferentSourceIdOnly_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider2");
+
+        // Act
+        bool result = attribution1 == attribution2;
+
+        // Assert
+        Assert.False(result);
+    }
+
+    #endregion
+
+    #region Inequality Operator Tests
+
+    [Fact]
+    public void InequalityOperator_WithEqualValues_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+
+        // Act
+        bool result = attribution1 != attribution2;
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void InequalityOperator_WithDifferentValues_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.ChatHistory, "Provider2");
+
+        // Act
+        bool result = attribution1 != attribution2;
+
+        // Assert
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void InequalityOperator_WithBothDefault_ReturnsFalse()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = default;
+        AgentRequestMessageSourceAttribution attribution2 = default;
+
+        // Act
+        bool result = attribution1 != attribution2;
+
+        // Assert
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void InequalityOperator_WithDifferentSourceTypeOnly_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.External, "Provider");
+
+        // Act
+        bool result = attribution1 != attribution2;
+
+        // Assert
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void InequalityOperator_WithDifferentSourceIdOnly_ReturnsTrue()
+    {
+        // Arrange
+        AgentRequestMessageSourceAttribution attribution1 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider1");
+        AgentRequestMessageSourceAttribution attribution2 = new(AgentRequestMessageSourceType.AIContextProvider, "Provider2");
+
+        // Act
+        bool result = attribution1 != attribution2;
+
+        // Assert
+        Assert.True(result);
+    }
+
+    #endregion
+}
@@ -5,7 +5,7 @@ using System;
 namespace Microsoft.Agents.AI.Abstractions.UnitTests;

 /// <summary>
-/// Contains tests for the <see cref="AgentRequestMessageSourceType"/> class.
+/// Contains tests for the <see cref="AgentRequestMessageSourceType"/> struct.
 /// </summary>
 public sealed class AgentRequestMessageSourceTypeTests
 {
@@ -38,6 +38,16 @@ public sealed class AgentRequestMessageSourceTypeTests
        Assert.Throws<ArgumentException>(() => new AgentRequestMessageSourceType(string.Empty));
    }

+    [Fact]
+    public void Default_DefaultsToExternal()
+    {
+        // Act
+        AgentRequestMessageSourceType defaultSource = default;
+
+        // Assert
+        Assert.Equal(AgentRequestMessageSourceType.External, defaultSource);
+    }
+
    #endregion

    #region Static Properties Tests
@@ -49,7 +59,6 @@ public sealed class AgentRequestMessageSourceTypeTests
        AgentRequestMessageSourceType source = AgentRequestMessageSourceType.External;

        // Assert
-        Assert.NotNull(source);
        Assert.Equal("External", source.Value);
    }

@@ -60,7 +69,6 @@ public sealed class AgentRequestMessageSourceTypeTests
        AgentRequestMessageSourceType source = AgentRequestMessageSourceType.AIContextProvider;

        // Assert
-        Assert.NotNull(source);
        Assert.Equal("AIContextProvider", source.Value);
    }

@@ -71,22 +79,11 @@ public sealed class AgentRequestMessageSourceTypeTests
        AgentRequestMessageSourceType source = AgentRequestMessageSourceType.ChatHistory;

        // Assert
-        Assert.NotNull(source);
        Assert.Equal("ChatHistory", source.Value);
    }

    [Fact]
-    public void AdditionalPropertiesKey_ReturnsExpectedValue()
-    {
-        // Arrange & Act
-        string key = AgentRequestMessageSourceType.AdditionalPropertiesKey;
-
-        // Assert
-        Assert.Equal("Agent.RequestMessageSourceType", key);
-    }
-
-    [Fact]
-    public void StaticProperties_ReturnSameInstanceOnMultipleCalls()
+    public void StaticProperties_ReturnEqualValuesOnMultipleCalls()
    {
        // Arrange & Act
        AgentRequestMessageSourceType external1 = AgentRequestMessageSourceType.External;
@@ -97,9 +94,9 @@ public sealed class AgentRequestMessageSourceTypeTests
        AgentRequestMessageSourceType chatHistory2 = AgentRequestMessageSourceType.ChatHistory;

        // Assert
-        Assert.Same(external1, external2);
-        Assert.Same(aiContextProvider1, aiContextProvider2);
-        Assert.Same(chatHistory1, chatHistory2);
+        Assert.Equal(external1, external2);
+        Assert.Equal(aiContextProvider1, aiContextProvider2);
+        Assert.Equal(chatHistory1, chatHistory2);
    }

    #endregion
@@ -148,7 +145,7 @@ public sealed class AgentRequestMessageSourceTypeTests
    }

    [Fact]
-    public void Equals_WithNull_ReturnsFalse()
+    public void Equals_WithNullObject_ReturnsFalse()
    {
        // Arrange
        AgentRequestMessageSourceType source = new("Test");
@@ -314,11 +311,11 @@ public sealed class AgentRequestMessageSourceTypeTests
    }

    [Fact]
-    public void EqualityOperator_WithBothNull_ReturnsTrue()
+    public void EqualityOperator_WithDefaultValues_ReturnsTrue()
    {
        // Arrange
-        AgentRequestMessageSourceType? source1 = null;
-        AgentRequestMessageSourceType? source2 = null;
+        AgentRequestMessageSourceType source1 = default;
+        AgentRequestMessageSourceType source2 = default;

        // Act
        bool result = source1 == source2;
@@ -327,34 +324,6 @@ public sealed class AgentRequestMessageSourceTypeTests
        Assert.True(result);
    }

-    [Fact]
-    public void EqualityOperator_WithLeftNull_ReturnsFalse()
-    {
-        // Arrange
-        AgentRequestMessageSourceType? source1 = null;
-        AgentRequestMessageSourceType source2 = new("Test");
-
-        // Act
-        bool result = source1 == source2;
-
-        // Assert
-        Assert.False(result);
-    }
-
-    [Fact]
-    public void EqualityOperator_WithRightNull_ReturnsFalse()
-    {
-        // Arrange
-        AgentRequestMessageSourceType source1 = new("Test");
-        AgentRequestMessageSourceType? source2 = null;
-
-        // Act
-        bool result = source1 == source2;
-
-        // Assert
-        Assert.False(result);
-    }
-
    [Fact]
    public void EqualityOperator_WithStaticInstances_ReturnsTrue()
    {
@@ -416,11 +385,11 @@ public sealed class AgentRequestMessageSourceTypeTests
    }

    [Fact]
-    public void InequalityOperator_WithBothNull_ReturnsFalse()
+    public void InequalityOperator_WithBothDefault_ReturnsFalse()
    {
        // Arrange
-        AgentRequestMessageSourceType? source1 = null;
-        AgentRequestMessageSourceType? source2 = null;
+        AgentRequestMessageSourceType source1 = default;
+        AgentRequestMessageSourceType source2 = default;

        // Act
        bool result = source1 != source2;
@@ -429,34 +398,6 @@ public sealed class AgentRequestMessageSourceTypeTests
        Assert.False(result);
    }

-    [Fact]
-    public void InequalityOperator_WithLeftNull_ReturnsTrue()
-    {
-        // Arrange
-        AgentRequestMessageSourceType? source1 = null;
-        AgentRequestMessageSourceType source2 = new("Test");
-
-        // Act
-        bool result = source1 != source2;
-
-        // Assert
-        Assert.True(result);
-    }
-
-    [Fact]
-    public void InequalityOperator_WithRightNull_ReturnsTrue()
-    {
-        // Arrange
-        AgentRequestMessageSourceType source1 = new("Test");
-        AgentRequestMessageSourceType? source2 = null;
-
-        // Act
-        bool result = source1 != source2;
-
-        // Assert
-        Assert.True(result);
-    }
-
    [Fact]
    public void InequalityOperator_DifferentStaticInstances_ReturnsTrue()
    {
@@ -64,7 +64,7 @@ public sealed class ChatHistoryProviderExtensionsTests
        Mock<ChatHistoryProvider> providerMock = new();
        List<ChatMessage> requestMessages =
        [
-            new(ChatRole.System, "System") { AdditionalProperties = new() { { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.ChatHistory } } },
+            new(ChatRole.System, "System") { AdditionalProperties = new() { { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "TestSource") } } },
            new(ChatRole.User, "Hello")
        ];
        ChatHistoryProvider.InvokedContext context = new(s_mockAgent, s_mockSession, requestMessages)
@@ -114,9 +114,9 @@ public sealed class ChatHistoryProviderExtensionsTests
        Mock<ChatHistoryProvider> providerMock = new();
        List<ChatMessage> requestMessages =
        [
-            new(ChatRole.System, "System") { AdditionalProperties = new() { { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.ChatHistory } } },
+            new(ChatRole.System, "System") { AdditionalProperties = new() { { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "TestSource") } } },
            new(ChatRole.User, "Hello"),
-            new(ChatRole.System, "Context") { AdditionalProperties = new() { { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.AIContextProvider } } }
+            new(ChatRole.System, "Context") { AdditionalProperties = new() { { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.AIContextProvider, "TestContextSource") } } }
        ];
        ChatHistoryProvider.InvokedContext context = new(s_mockAgent, s_mockSession, requestMessages);

@@ -157,7 +157,7 @@ public sealed class ChatHistoryProviderMessageFilterTests
        var innerProviderMock = new Mock<ChatHistoryProvider>();
        List<ChatMessage> requestMessages =
        [
-            new(ChatRole.System, "System") { AdditionalProperties = new() { { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.ChatHistory } } },
+            new(ChatRole.System, "System") { AdditionalProperties = new() { { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "TestSource") } } },
            new(ChatRole.User, "Hello"),
        ];
        var responseMessages = new List<ChatMessage> { new(ChatRole.Assistant, "Response") };
@@ -176,7 +176,7 @@ public sealed class ChatHistoryProviderMessageFilterTests
        // Filter that modifies the context
        ChatHistoryProvider.InvokedContext InvokedFilter(ChatHistoryProvider.InvokedContext ctx)
        {
-            var modifiedRequestMessages = ctx.RequestMessages.Where(x => x.GetAgentRequestMessageSource() == AgentRequestMessageSourceType.External).Select(m => new ChatMessage(m.Role, $"[FILTERED] {m.Text}")).ToList();
+            var modifiedRequestMessages = ctx.RequestMessages.Where(x => x.GetAgentRequestMessageSourceType() == AgentRequestMessageSourceType.External).Select(m => new ChatMessage(m.Role, $"[FILTERED] {m.Text}")).ToList();
            return new ChatHistoryProvider.InvokedContext(s_mockAgent, s_mockSession, modifiedRequestMessages)
            {
                ResponseMessages = ctx.ResponseMessages,
@@ -22,7 +22,7 @@ public class ChatHistoryProviderTests
    #region InvokingAsync Message Stamping Tests

    [Fact]
-    public async Task InvokingAsync_StampsMessagesWithSourceTypeAndSourceAsync()
+    public async Task InvokingAsync_StampsMessagesWithSourceTypeAndSourceIdAsync()
    {
        // Arrange
        var provider = new TestChatHistoryProvider();
@@ -34,18 +34,18 @@ public class ChatHistoryProviderTests
        // Assert
        ChatMessage message = messages.Single();
        Assert.NotNull(message.AdditionalProperties);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceType.AdditionalPropertiesKey, out object? sourceType));
-        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, sourceType);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSource.AdditionalPropertiesKey, out object? source));
-        Assert.Equal(typeof(TestChatHistoryProvider).FullName, source);
+        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, out object? attribution));
+        var typedAttribution = Assert.IsType<AgentRequestMessageSourceAttribution>(attribution);
+        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, typedAttribution.SourceType);
+        Assert.Equal(typeof(TestChatHistoryProvider).FullName, typedAttribution.SourceId);
    }

    [Fact]
-    public async Task InvokingAsync_WithCustomSourceName_StampsMessagesWithCustomSourceAsync()
+    public async Task InvokingAsync_WithCustomSourceId_StampsMessagesWithCustomSourceIdAsync()
    {
        // Arrange
-        const string CustomSourceName = "CustomHistorySource";
-        var provider = new TestChatHistoryProviderWithCustomSource(CustomSourceName);
+        const string CustomSourceId = "CustomHistorySource";
+        var provider = new TestChatHistoryProviderWithCustomSource(CustomSourceId);
        var context = new ChatHistoryProvider.InvokingContext(s_mockAgent, s_mockSession, [new ChatMessage(ChatRole.User, "Request")]);

        // Act
@@ -54,10 +54,10 @@ public class ChatHistoryProviderTests
        // Assert
        ChatMessage message = messages.Single();
        Assert.NotNull(message.AdditionalProperties);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceType.AdditionalPropertiesKey, out object? sourceType));
-        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, sourceType);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSource.AdditionalPropertiesKey, out object? source));
-        Assert.Equal(CustomSourceName, source);
+        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, out object? attribution));
+        var typedAttribution = Assert.IsType<AgentRequestMessageSourceAttribution>(attribution);
+        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, typedAttribution.SourceType);
+        Assert.Equal(CustomSourceId, typedAttribution.SourceId);
    }

    [Fact]
@@ -73,10 +73,10 @@ public class ChatHistoryProviderTests
        // Assert
        ChatMessage message = messages.Single();
        Assert.NotNull(message.AdditionalProperties);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceType.AdditionalPropertiesKey, out object? sourceType));
-        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, sourceType);
-        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSource.AdditionalPropertiesKey, out object? source));
-        Assert.Equal(typeof(TestChatHistoryProviderWithPreStampedMessages).FullName, source);
+        Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, out object? attribution));
+        var typedAttribution = Assert.IsType<AgentRequestMessageSourceAttribution>(attribution);
+        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, typedAttribution.SourceType);
+        Assert.Equal(typeof(TestChatHistoryProviderWithPreStampedMessages).FullName, typedAttribution.SourceId);
    }

    [Fact]
@@ -96,10 +96,10 @@ public class ChatHistoryProviderTests
        foreach (ChatMessage message in messageList)
        {
            Assert.NotNull(message.AdditionalProperties);
-            Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceType.AdditionalPropertiesKey, out object? sourceType));
-            Assert.Equal(AgentRequestMessageSourceType.ChatHistory, sourceType);
-            Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSource.AdditionalPropertiesKey, out object? source));
-            Assert.Equal(typeof(TestChatHistoryProviderWithMultipleMessages).FullName, source);
+            Assert.True(message.AdditionalProperties.TryGetValue(AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, out object? attribution));
+            var typedAttribution = Assert.IsType<AgentRequestMessageSourceAttribution>(attribution);
+            Assert.Equal(AgentRequestMessageSourceType.ChatHistory, typedAttribution.SourceType);
+            Assert.Equal(typeof(TestChatHistoryProviderWithMultipleMessages).FullName, typedAttribution.SourceId);
        }
    }

@@ -383,7 +383,7 @@ public class ChatHistoryProviderTests

    private sealed class TestChatHistoryProviderWithCustomSource : ChatHistoryProvider
    {
-        public TestChatHistoryProviderWithCustomSource(string sourceName) : base(sourceName)
+        public TestChatHistoryProviderWithCustomSource(string sourceId) : base(sourceId)
        {
        }

@@ -404,8 +404,7 @@ public class ChatHistoryProviderTests
            var message = new ChatMessage(ChatRole.User, "Pre-stamped Message");
            message.AdditionalProperties = new AdditionalPropertiesDictionary
            {
-                [AgentRequestMessageSourceType.AdditionalPropertiesKey] = AgentRequestMessageSourceType.ChatHistory,
-                [AgentRequestMessageSource.AdditionalPropertiesKey] = this.GetType().FullName!
+                [AgentRequestMessageSourceAttribution.AdditionalPropertiesKey] = new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, this.GetType().FullName!)
            };
            return new([message]);
        }
@@ -9,23 +9,23 @@ namespace Microsoft.Agents.AI.Abstractions.UnitTests;
 /// </summary>
 public sealed class ChatMessageExtensionsTests
 {
-    #region GetAgentRequestMessageSource Tests
+    #region GetAgentRequestMessageSourceType Tests

    [Fact]
-    public void GetAgentRequestMessageSource_WithNoAdditionalProperties_ReturnsExternal()
+    public void GetAgentRequestMessageSourceType_WithNoAdditionalProperties_ReturnsExternal()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello");

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.External, result);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithNullAdditionalProperties_ReturnsExternal()
+    public void GetAgentRequestMessageSourceType_WithNullAdditionalProperties_ReturnsExternal()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello")
@@ -34,14 +34,14 @@ public sealed class ChatMessageExtensionsTests
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.External, result);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithEmptyAdditionalProperties_ReturnsExternal()
+    public void GetAgentRequestMessageSourceType_WithEmptyAdditionalProperties_ReturnsExternal()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello")
@@ -50,130 +50,130 @@ public sealed class ChatMessageExtensionsTests
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.External, result);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithExternalSource_ReturnsExternal()
+    public void GetAgentRequestMessageSourceType_WithExternalSourceType_ReturnsExternal()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello")
        {
            AdditionalProperties = new AdditionalPropertiesDictionary
            {
-                { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.External }
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.External, "TestSourceId") }
            }
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.External, result);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithAIContextProviderSource_ReturnsAIContextProvider()
+    public void GetAgentRequestMessageSourceType_WithAIContextProviderSourceType_ReturnsAIContextProvider()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello")
        {
            AdditionalProperties = new AdditionalPropertiesDictionary
            {
-                { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.AIContextProvider }
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.AIContextProvider, "TestSourceId") }
            }
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, result);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithChatHistorySource_ReturnsChatHistory()
+    public void GetAgentRequestMessageSourceType_WithChatHistorySourceType_ReturnsChatHistory()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello")
        {
            AdditionalProperties = new AdditionalPropertiesDictionary
            {
-                { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.ChatHistory }
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "TestSourceId") }
            }
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, result);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithCustomSource_ReturnsCustomSource()
+    public void GetAgentRequestMessageSourceType_WithCustomSourceType_ReturnsCustomSourceType()
    {
        // Arrange
-        AgentRequestMessageSourceType customSource = new("CustomSource");
+        AgentRequestMessageSourceType customSourceType = new("CustomSourceType");
        ChatMessage message = new(ChatRole.User, "Hello")
        {
            AdditionalProperties = new AdditionalPropertiesDictionary
            {
-                { AgentRequestMessageSourceType.AdditionalPropertiesKey, customSource }
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(customSourceType, "TestSourceId") }
            }
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
-        Assert.Equal(customSource, result);
-        Assert.Equal("CustomSource", result.Value);
+        Assert.Equal(customSourceType, result);
+        Assert.Equal("CustomSourceType", result.Value);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithWrongKeyType_ReturnsExternal()
+    public void GetAgentRequestMessageSourceType_WithWrongAttributionType_ReturnsExternal()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello")
        {
            AdditionalProperties = new AdditionalPropertiesDictionary
            {
-                { AgentRequestMessageSourceType.AdditionalPropertiesKey, "NotAnAgentRequestMessageSource" }
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, "NotAnAgentRequestMessageSourceAttribution" }
            }
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.External, result);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithNullValue_ReturnsExternal()
+    public void GetAgentRequestMessageSourceType_WithNullAttributionValue_ReturnsExternal()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello")
        {
            AdditionalProperties = new AdditionalPropertiesDictionary
            {
-                { AgentRequestMessageSourceType.AdditionalPropertiesKey, null! }
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, null! }
            }
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.External, result);
    }

    [Fact]
-    public void GetAgentRequestMessageSource_WithMultipleProperties_ReturnsCorrectSource()
+    public void GetAgentRequestMessageSourceType_WithMultipleProperties_ReturnsCorrectSourceType()
    {
        // Arrange
        ChatMessage message = new(ChatRole.User, "Hello")
@@ -181,17 +181,345 @@ public sealed class ChatMessageExtensionsTests
            AdditionalProperties = new AdditionalPropertiesDictionary
            {
                { "OtherProperty", "SomeValue" },
-                { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.ChatHistory },
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "TestSourceId") },
                { "AnotherProperty", 123 }
            }
        };

        // Act
-        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSource();
+        AgentRequestMessageSourceType result = message.GetAgentRequestMessageSourceType();

        // Assert
        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, result);
    }

    #endregion
+
+    #region GetAgentRequestMessageSourceId Tests
+
+    [Fact]
+    public void GetAgentRequestMessageSourceId_WithNoAdditionalProperties_ReturnsNull()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello");
+
+        // Act
+        string? result = message.GetAgentRequestMessageSourceId();
+
+        // Assert
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GetAgentRequestMessageSourceId_WithNullAdditionalProperties_ReturnsNull()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = null
+        };
+
+        // Act
+        string? result = message.GetAgentRequestMessageSourceId();
+
+        // Assert
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GetAgentRequestMessageSourceId_WithEmptyAdditionalProperties_ReturnsNull()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary()
+        };
+
+        // Act
+        string? result = message.GetAgentRequestMessageSourceId();
+
+        // Assert
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GetAgentRequestMessageSourceId_WithAttribution_ReturnsSourceId()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.AIContextProvider, "MyProvider.FullName") }
+            }
+        };
+
+        // Act
+        string? result = message.GetAgentRequestMessageSourceId();
+
+        // Assert
+        Assert.Equal("MyProvider.FullName", result);
+    }
+
+    [Fact]
+    public void GetAgentRequestMessageSourceId_WithDifferentSourceIds_ReturnsCorrectSourceId()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "CustomHistorySourceId") }
+            }
+        };
+
+        // Act
+        string? result = message.GetAgentRequestMessageSourceId();
+
+        // Assert
+        Assert.Equal("CustomHistorySourceId", result);
+    }
+
+    [Fact]
+    public void GetAgentRequestMessageSourceId_WithWrongAttributionType_ReturnsNull()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, "NotAnAgentRequestMessageSourceAttribution" }
+            }
+        };
+
+        // Act
+        string? result = message.GetAgentRequestMessageSourceId();
+
+        // Assert
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GetAgentRequestMessageSourceId_WithNullAttributionValue_ReturnsNull()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, null! }
+            }
+        };
+
+        // Act
+        string? result = message.GetAgentRequestMessageSourceId();
+
+        // Assert
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GetAgentRequestMessageSourceId_WithMultipleProperties_ReturnsCorrectSourceId()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { "OtherProperty", "SomeValue" },
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.External, "ExpectedSourceId") },
+                { "AnotherProperty", 123 }
+            }
+        };
+
+        // Act
+        string? result = message.GetAgentRequestMessageSourceId();
+
+        // Assert
+        Assert.Equal("ExpectedSourceId", result);
+    }
+
+    #endregion
+
+    #region AsAgentRequestMessageSourcedMessage Tests
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_WithNoAdditionalProperties_ReturnsClonesMessageWithAttribution()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello");
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.External, "TestSourceId");
+
+        // Assert
+        Assert.NotSame(message, result);
+        Assert.Equal(AgentRequestMessageSourceType.External, result.GetAgentRequestMessageSourceType());
+        Assert.Equal("TestSourceId", result.GetAgentRequestMessageSourceId());
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_WithNullAdditionalProperties_ReturnsClonesMessageWithAttribution()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = null
+        };
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.AIContextProvider, "ProviderSourceId");
+
+        // Assert
+        Assert.NotSame(message, result);
+        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, result.GetAgentRequestMessageSourceType());
+        Assert.Equal("ProviderSourceId", result.GetAgentRequestMessageSourceId());
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_WithMatchingSourceTypeAndSourceId_ReturnsSameInstance()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "HistoryId") }
+            }
+        };
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.ChatHistory, "HistoryId");
+
+        // Assert
+        Assert.Same(message, result);
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_WithDifferentSourceType_ReturnsClonesMessageWithNewAttribution()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.External, "SourceId") }
+            }
+        };
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.AIContextProvider, "SourceId");
+
+        // Assert
+        Assert.NotSame(message, result);
+        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, result.GetAgentRequestMessageSourceType());
+        Assert.Equal("SourceId", result.GetAgentRequestMessageSourceId());
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_WithDifferentSourceId_ReturnsClonesMessageWithNewAttribution()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.External, "OriginalId") }
+            }
+        };
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.External, "NewId");
+
+        // Assert
+        Assert.NotSame(message, result);
+        Assert.Equal(AgentRequestMessageSourceType.External, result.GetAgentRequestMessageSourceType());
+        Assert.Equal("NewId", result.GetAgentRequestMessageSourceId());
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_WithDefaultNullSourceId_ReturnsClonesMessageWithNullSourceId()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello");
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.ChatHistory);
+
+        // Assert
+        Assert.NotSame(message, result);
+        Assert.Equal(AgentRequestMessageSourceType.ChatHistory, result.GetAgentRequestMessageSourceType());
+        Assert.Null(result.GetAgentRequestMessageSourceId());
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_WithMatchingSourceTypeAndNullSourceId_ReturnsSameInstance()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.External, null) }
+            }
+        };
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.External);
+
+        // Assert
+        Assert.Same(message, result);
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_DoesNotModifyOriginalMessage()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello");
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.AIContextProvider, "ProviderId");
+
+        // Assert
+        Assert.Null(message.AdditionalProperties);
+        Assert.NotNull(result.AdditionalProperties);
+        Assert.Equal(AgentRequestMessageSourceType.AIContextProvider, result.GetAgentRequestMessageSourceType());
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_WithWrongAttributionType_ReturnsClonesMessageWithNewAttribution()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.User, "Hello")
+        {
+            AdditionalProperties = new AdditionalPropertiesDictionary
+            {
+                { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, "NotAnAttribution" }
+            }
+        };
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.External, "SourceId");
+
+        // Assert
+        Assert.NotSame(message, result);
+        Assert.Equal(AgentRequestMessageSourceType.External, result.GetAgentRequestMessageSourceType());
+        Assert.Equal("SourceId", result.GetAgentRequestMessageSourceId());
+    }
+
+    [Fact]
+    public void AsAgentRequestMessageSourcedMessage_PreservesMessageContent()
+    {
+        // Arrange
+        ChatMessage message = new(ChatRole.Assistant, "Test content");
+
+        // Act
+        ChatMessage result = message.AsAgentRequestMessageSourcedMessage(AgentRequestMessageSourceType.ChatHistory, "HistoryId");
+
+        // Assert
+        Assert.Equal(ChatRole.Assistant, result.Role);
+        Assert.Equal("Test content", result.Text);
+    }
+
+    #endregion
 }
@@ -55,7 +55,7 @@ public class InMemoryChatHistoryProviderTests
        var requestMessages = new List<ChatMessage>
        {
            new(ChatRole.User, "Hello"),
-            new(ChatRole.System, "additional context") { AdditionalProperties = new() { { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.ChatHistory } } },
+            new(ChatRole.System, "additional context") { AdditionalProperties = new() { { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.ChatHistory, "TestSource") } } },
        };
        var responseMessages = new List<ChatMessage>
        {
@@ -286,7 +286,7 @@ public sealed class CosmosChatHistoryProviderTests : IAsyncLifetime, IDisposable
            new ChatMessage(ChatRole.User, "First message"),
            new ChatMessage(ChatRole.Assistant, "Second message"),
            new ChatMessage(ChatRole.User, "Third message"),
-            new ChatMessage(ChatRole.System, "System context message") { AdditionalProperties = new() { { AgentRequestMessageSourceType.AdditionalPropertiesKey, AgentRequestMessageSourceType.AIContextProvider } } }
+            new ChatMessage(ChatRole.System, "System context message") { AdditionalProperties = new() { { AgentRequestMessageSourceAttribution.AdditionalPropertiesKey, new AgentRequestMessageSourceAttribution(AgentRequestMessageSourceType.AIContextProvider, "TestSource") } } }
        };
        var responseMessages = new[]
        {