.NET: Address Feedback on StateBag feature branch PR (#3910)

* Address Feedback on statebag feature branch PR

* Update dotnet/src/Microsoft.Agents.AI.DurableTask/CHANGELOG.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Address PR comments

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

dotnet/samples/GettingStarted/AgentProviders/Agent_With_CustomImplementation/Program.cs

@@ -59,13 +59,13 @@ namespace SampleApp
 
             // Get existing messages from the store
             var invokingContext = new ChatHistoryProvider.InvokingContext(this, session, messages);
-            var storeMessages = await this.ChatHistoryProvider.InvokingAsync(invokingContext, cancellationToken);
+            var userAndChatHistoryMessages = await this.ChatHistoryProvider.InvokingAsync(invokingContext, cancellationToken);
 
             // Clone the input messages and turn them into response messages with upper case text.
             List<ChatMessage> responseMessages = CloneAndToUpperCase(messages, this.Name).ToList();
 
             // Notify the session of the input and output messages.
-            var invokedContext = new ChatHistoryProvider.InvokedContext(this, session, messages, responseMessages);
+            var invokedContext = new ChatHistoryProvider.InvokedContext(this, session, userAndChatHistoryMessages, responseMessages);
             await this.ChatHistoryProvider.InvokedAsync(invokedContext, cancellationToken);
 
             return new AgentResponse
@@ -88,13 +88,13 @@ namespace SampleApp
 
             // Get existing messages from the store
             var invokingContext = new ChatHistoryProvider.InvokingContext(this, session, messages);
-            var storeMessages = await this.ChatHistoryProvider.InvokingAsync(invokingContext, cancellationToken);
+            var userAndChatHistoryMessages = await this.ChatHistoryProvider.InvokingAsync(invokingContext, cancellationToken);
 
             // Clone the input messages and turn them into response messages with upper case text.
             List<ChatMessage> responseMessages = CloneAndToUpperCase(messages, this.Name).ToList();
 
             // Notify the session of the input and output messages.
-            var invokedContext = new ChatHistoryProvider.InvokedContext(this, session, messages, responseMessages);
+            var invokedContext = new ChatHistoryProvider.InvokedContext(this, session, userAndChatHistoryMessages, responseMessages);
             await this.ChatHistoryProvider.InvokedAsync(invokedContext, cancellationToken);
 
             foreach (var message in responseMessages)

dotnet/src/Microsoft.Agents.AI.Abstractions/AIContextProvider.cs

@@ -223,9 +223,9 @@ public abstract class AIContextProvider
     /// Contains the context information provided to <see cref="InvokedCoreAsync(InvokedContext, CancellationToken)"/>.
     /// </summary>
     /// <remarks>
-    /// This class provides context about a completed agent invocation, including both the
-    /// request messages that were used and the response messages that were generated. It also indicates
-    /// whether the invocation succeeded or failed.
+    /// This class provides context about a completed agent invocation, including the accumulated
+    /// request messages (user input, chat history and any others provided by AI context providers) that were used
+    /// and the response messages that were generated. It also indicates whether the invocation succeeded or failed.
     /// </remarks>
     public sealed class InvokedContext
     {
@@ -234,7 +234,8 @@ public abstract class AIContextProvider
         /// </summary>
         /// <param name="agent">The agent that was invoked.</param>
         /// <param name="session">The session associated with the agent invocation.</param>
-        /// <param name="requestMessages">The messages that were used by the agent for this invocation.</param>
+        /// <param name="requestMessages">The accumulated request messages (user input, chat history and any others provided by AI context providers)
+        /// that were used by the agent for this invocation.</param>
         /// <param name="responseMessages">The response messages generated during this invocation.</param>
         /// <exception cref="ArgumentNullException"><paramref name="agent"/>, <paramref name="requestMessages"/>, or <paramref name="responseMessages"/> is <see langword="null"/>.</exception>
         public InvokedContext(
@@ -254,7 +255,8 @@ public abstract class AIContextProvider
         /// </summary>
         /// <param name="agent">The agent that was invoked.</param>
         /// <param name="session">The session associated with the agent invocation.</param>
-        /// <param name="requestMessages">The messages that were used by the agent for this invocation.</param>
+        /// <param name="requestMessages">The accumulated request messages (user input, chat history and any others provided by AI context providers)
+        /// that were used by the agent for this invocation.</param>
         /// <param name="invokeException">The exception that caused the invocation to fail.</param>
         /// <exception cref="ArgumentNullException"><paramref name="agent"/>, <paramref name="requestMessages"/>, or <paramref name="invokeException"/> is <see langword="null"/>.</exception>
         public InvokedContext(
@@ -280,7 +282,8 @@ public abstract class AIContextProvider
         public AgentSession? Session { get; }
 
         /// <summary>
-        /// Gets the messages that were used by the agent for this invocation.
+        /// Gets the accumulated request messages (user input, chat history and any others provided by AI context providers)
+        /// that were used by the agent for this invocation.
         /// </summary>
         /// <value>
         /// A collection of <see cref="ChatMessage"/> instances representing all messages that were used by the agent for this invocation.

dotnet/src/Microsoft.Agents.AI.Abstractions/AgentSessionStateBagValue.cs

@@ -78,10 +78,17 @@ internal class AgentSessionStateBagValue
 
         lock (this._lock)
         {
-            if (this._cache is { } cache)
+            switch (this._cache)
             {
-                value = cache.Value as T;
-                return true;
+                case DeserializedCache { Value: null, ValueType: Type cacheValueType } when cacheValueType == typeof(T):
+                    value = null;
+                    return true;
+                case DeserializedCache { Value: T cacheValue, ValueType: Type cacheValueType } when cacheValueType == typeof(T):
+                    value = cacheValue;
+                    return true;
+                case DeserializedCache { ValueType: Type cacheValueType } when cacheValueType != typeof(T):
+                    value = null;
+                    return false;
             }
 
             switch (this._jsonValue)
@@ -118,9 +125,14 @@ internal class AgentSessionStateBagValue
 
         lock (this._lock)
         {
-            if (this._cache is { } cache)
+            switch (this._cache)
             {
-                return cache.Value as T;
+                case DeserializedCache { Value: null, ValueType: Type cacheValueType } when cacheValueType == typeof(T):
+                    return null;
+                case DeserializedCache { Value: T cacheValue, ValueType: Type cacheValueType } when cacheValueType == typeof(T):
+                    return cacheValue;
+                case DeserializedCache { ValueType: Type cacheValueType } when cacheValueType != typeof(T):
+                    throw new InvalidOperationException($"The type of the cached value is {cacheValueType.FullName}, but the requested type is {typeof(T).FullName}.");
             }
 
             switch (this._jsonValue)
@@ -144,7 +156,7 @@ internal class AgentSessionStateBagValue
     /// Sets the deserialized value of this session state value, updating the cache accordingly.
     /// This does not update the JsonValue directly; the JsonValue will be updated on the next read or when the object is serialized.
     /// </summary>
-    public void SetDeserialized(object? deserializedValue, Type valueType, JsonSerializerOptions jsonSerializerOptions)
+    public void SetDeserialized<T>(T? deserializedValue, Type valueType, JsonSerializerOptions jsonSerializerOptions)
     {
         lock (this._lock)
         {

dotnet/src/Microsoft.Agents.AI.Abstractions/ChatHistoryProvider.cs

@@ -253,9 +253,9 @@ public abstract class ChatHistoryProvider
     /// Contains the context information provided to <see cref="InvokedCoreAsync(InvokedContext, CancellationToken)"/>.
     /// </summary>
     /// <remarks>
-    /// This class provides context about a completed agent invocation, including both the
-    /// request messages that were used and the response messages that were generated. It also indicates
-    /// whether the invocation succeeded or failed.
+    /// This class provides context about a completed agent invocation, including the accumulated
+    /// request messages (user input, chat history and any others provided by AI context providers) that were used
+    /// and the response messages that were generated. It also indicates whether the invocation succeeded or failed.
     /// </remarks>
     public sealed class InvokedContext
     {
@@ -264,7 +264,8 @@ public abstract class ChatHistoryProvider
         /// </summary>
         /// <param name="agent">The agent that was invoked.</param>
         /// <param name="session">The session associated with the agent invocation.</param>
-        /// <param name="requestMessages">The caller provided messages that were used by the agent for this invocation.</param>
+        /// <param name="requestMessages">The accumulated request messages (user input, chat history and any others provided by AI context providers)
+        /// that were used by the agent for this invocation.</param>
         /// <param name="responseMessages">The response messages generated during this invocation.</param>
         /// <exception cref="ArgumentNullException"><paramref name="agent"/>, <paramref name="requestMessages"/>, or <paramref name="responseMessages"/> is <see langword="null"/>.</exception>
         public InvokedContext(
@@ -284,7 +285,8 @@ public abstract class ChatHistoryProvider
         /// </summary>
         /// <param name="agent">The agent that was invoked.</param>
         /// <param name="session">The session associated with the agent invocation.</param>
-        /// <param name="requestMessages">The caller provided messages that were used by the agent for this invocation.</param>
+        /// <param name="requestMessages">The accumulated request messages (user input, chat history and any others provided by AI context providers)
+        /// that were used by the agent for this invocation.</param>
         /// <param name="invokeException">The exception that caused the invocation to fail.</param>
         /// <exception cref="ArgumentNullException"><paramref name="agent"/>, <paramref name="requestMessages"/>, or <paramref name="invokeException"/> is <see langword="null"/>.</exception>
         public InvokedContext(
@@ -310,7 +312,8 @@ public abstract class ChatHistoryProvider
         public AgentSession? Session { get; }
 
         /// <summary>
-        /// Gets the caller provided messages that were used by the agent for this invocation.
+        /// Gets the accumulated request messages (user input, chat history and any others provided by AI context providers)
+        /// that were used by the agent for this invocation.
         /// </summary>
         /// <value>
         /// A collection of <see cref="ChatMessage"/> instances representing new messages that were provided by the caller.

dotnet/src/Microsoft.Agents.AI.DurableTask/CHANGELOG.md

@@ -12,6 +12,7 @@
 - Renamed serializedSession parameter to serializedState on DeserializeSessionAsync for consistency ([#3681](https://github.com/microsoft/agent-framework/pull/3681))
 - Introduce Core method pattern for Session management methods on AIAgent ([#3699](https://github.com/microsoft/agent-framework/pull/3699))
 - Changed AIAgent.SerializeSession to AIAgent.SerializeSessionAsync ([#3879](https://github.com/microsoft/agent-framework/pull/3879))
+- Changed ChatHistory and AIContext Providers to have pipeline semantics ([#3806](https://github.com/microsoft/agent-framework/pull/3806))
 
 ## v1.0.0-preview.251204.1
 

dotnet/tests/Microsoft.Agents.AI.Abstractions.UnitTests/AgentSessionStateBagTests.cs

@@ -534,14 +534,9 @@ public sealed class AgentSessionStateBagTests
         for (int i = 0; i < 200; i++)
         {
             int index = i;
-            if (index % 2 == 0)
-            {
-                tasks[i] = System.Threading.Tasks.Task.Run(() => stateBag.GetValue<string>("key"));
-            }
-            else
-            {
-                tasks[i] = System.Threading.Tasks.Task.Run(() => stateBag.SetValue("key", $"value{index}"));
-            }
+            tasks[i] = (index % 2 == 0)
+                ? System.Threading.Tasks.Task.Run(() => stateBag.GetValue<string>("key"))
+                : System.Threading.Tasks.Task.Run(() => stateBag.SetValue("key", $"value{index}"));
         }
 
         await System.Threading.Tasks.Task.WhenAll(tasks);
@@ -650,6 +645,104 @@ public sealed class AgentSessionStateBagTests
 
     #endregion
 
+    #region Type Mismatch Tests
+
+    [Fact]
+    public void TryGetValue_WithDifferentTypeAfterSet_ReturnsFalse()
+    {
+        // Arrange
+        var stateBag = new AgentSessionStateBag();
+        stateBag.SetValue("key1", "hello");
+
+        // Act
+        var found = stateBag.TryGetValue<Animal>("key1", out var result, TestJsonSerializerContext.Default.Options);
+
+        // Assert
+        Assert.False(found);
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GetValue_WithDifferentTypeAfterSet_ThrowsInvalidOperationException()
+    {
+        // Arrange
+        var stateBag = new AgentSessionStateBag();
+        stateBag.SetValue("key1", "hello");
+
+        // Act & Assert
+        Assert.Throws<InvalidOperationException>(() => stateBag.GetValue<Animal>("key1", TestJsonSerializerContext.Default.Options));
+    }
+
+    [Fact]
+    public void TryGetValue_WithDifferentTypeAfterDeserializedRead_ReturnsFalse()
+    {
+        // Arrange
+        var stateBag = new AgentSessionStateBag();
+        stateBag.SetValue("key1", "hello");
+
+        // First read caches the value as string
+        var cachedValue = stateBag.GetValue<string>("key1");
+        Assert.Equal("hello", cachedValue);
+
+        // Act - request as a different type
+        var found = stateBag.TryGetValue<Animal>("key1", out var result, TestJsonSerializerContext.Default.Options);
+
+        // Assert
+        Assert.False(found);
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GetValue_WithDifferentTypeAfterDeserializedRoundtrip_ThrowsInvalidOperationException()
+    {
+        // Arrange
+        var originalStateBag = new AgentSessionStateBag();
+        originalStateBag.SetValue("key1", "hello");
+
+        // Round-trip through serialization
+        var json = originalStateBag.Serialize();
+        var restoredStateBag = AgentSessionStateBag.Deserialize(json);
+
+        // First read caches the value as string
+        var cachedValue = restoredStateBag.GetValue<string>("key1");
+        Assert.Equal("hello", cachedValue);
+
+        // Act & Assert - request as a different type
+        Assert.Throws<InvalidOperationException>(() => restoredStateBag.GetValue<Animal>("key1", TestJsonSerializerContext.Default.Options));
+    }
+
+    [Fact]
+    public void TryGetValue_ComplexTypeAfterSetString_ReturnsFalse()
+    {
+        // Arrange
+        var stateBag = new AgentSessionStateBag();
+        stateBag.SetValue("animal", "not an animal");
+
+        // Act
+        var found = stateBag.TryGetValue<Animal>("animal", out var result, TestJsonSerializerContext.Default.Options);
+
+        // Assert
+        Assert.False(found);
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void GetValue_TypeMismatch_ExceptionMessageContainsBothTypeNames()
+    {
+        // Arrange
+        var stateBag = new AgentSessionStateBag();
+        stateBag.SetValue("key1", "hello");
+
+        // Act
+        var exception = Assert.Throws<InvalidOperationException>(() => stateBag.GetValue<Animal>("key1", TestJsonSerializerContext.Default.Options));
+
+        // Assert
+        Assert.Contains(typeof(string).FullName!, exception.Message);
+        Assert.Contains(typeof(Animal).FullName!, exception.Message);
+    }
+
+    #endregion
+
     #region JsonSerializer Integration Tests
 
     [Fact]