.NET: BREAKING Update AIAgent.Run to take IEnumerable instead of IReadonlyCollection (#729)

* Update AIAgent,Run to take IEnumerable instead of IReadonlyCollection

* Address PR comment.

* Cast to IReadonlyCollection since this is typically all that is required to avoid unecessary allocation.

* Update OrchestratingAgent protected methods as well.

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

@@ -30,7 +30,7 @@ namespace SampleApp
     // Custom agent that parrot's the user input back in upper case.
     internal sealed class UpperCaseParrotAgent : AIAgent
     {
-        public override async Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+        public override async Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
         {
             // Create a thread if the user didn't supply one.
             thread ??= this.GetNewThread();
@@ -50,7 +50,7 @@ namespace SampleApp
             };
         }
 
-        public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+        public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
         {
             // Create a thread if the user didn't supply one.
             thread ??= this.GetNewThread();
@@ -76,7 +76,7 @@ namespace SampleApp
             }
         }
 
-        private static IEnumerable<ChatMessage> CloneAndToUpperCase(IReadOnlyCollection<ChatMessage> messages, string agentName) => messages.Select(x =>
+        private static IEnumerable<ChatMessage> CloneAndToUpperCase(IEnumerable<ChatMessage> messages, string agentName) => messages.Select(x =>
             {
                 // Clone the message and update its author to be the agent.
                 var messageClone = x.Clone();

dotnet/samples/GettingStarted/Agents/Agent_Step07_3rdPartyThreadStorage/Program.cs

@@ -82,7 +82,7 @@ namespace SampleApp
 
         public string? ThreadId => this._threadId;
 
-        public async Task AddMessagesAsync(IReadOnlyCollection<ChatMessage> messages, CancellationToken cancellationToken)
+        public async Task AddMessagesAsync(IEnumerable<ChatMessage> messages, CancellationToken cancellationToken)
         {
             this._threadId ??= Guid.NewGuid().ToString();
 

dotnet/src/Microsoft.Agents.Orchestration/ConcurrentOrchestration.cs

@@ -57,11 +57,11 @@ public partial class ConcurrentOrchestration : OrchestratingAgent
     }
 
     /// <inheritdoc />
-    protected override Task<AgentRunResponse> RunCoreAsync(IReadOnlyCollection<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken) =>
-        this.ResumeAsync(messages, new AgentRunResponse?[this.Agents.Count], context, cancellationToken);
+    protected override Task<AgentRunResponse> RunCoreAsync(IEnumerable<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken) =>
+        this.ResumeAsync(messages as IReadOnlyCollection<ChatMessage> ?? messages.ToList(), new AgentRunResponse?[this.Agents.Count], context, cancellationToken);
 
     /// <inheritdoc />
-    protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IReadOnlyCollection<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken)
+    protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IEnumerable<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken)
     {
         var state = checkpointState.Deserialize(OrchestrationJsonContext.Default.ConcurrentState) ?? throw new InvalidOperationException("The checkpoint state is invalid.");
 

dotnet/src/Microsoft.Agents.Orchestration/GroupChat/GroupChatOrchestration.cs

@@ -43,7 +43,7 @@ public sealed partial class GroupChatOrchestration : OrchestratingAgent
     public Func<ValueTask<ChatMessage>>? InteractiveCallback { get; set; }
 
     /// <inheritdoc />
-    protected override Task<AgentRunResponse> RunCoreAsync(IReadOnlyCollection<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken)
+    protected override Task<AgentRunResponse> RunCoreAsync(IEnumerable<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken)
     {
         List<ChatMessage> allMessages = [.. messages];
         int originalMessageCount = allMessages.Count;
@@ -51,7 +51,7 @@ public sealed partial class GroupChatOrchestration : OrchestratingAgent
     }
 
     /// <inheritdoc />
-    protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IReadOnlyCollection<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken)
+    protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IEnumerable<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken)
     {
         var state = checkpointState.Deserialize(OrchestrationJsonContext.Default.GroupChatState) ?? throw new InvalidOperationException("The checkpoint state is invalid.");
 

dotnet/src/Microsoft.Agents.Orchestration/Handoffs/HandoffOrchestration.cs

@@ -44,7 +44,7 @@ public sealed partial class HandoffOrchestration : OrchestratingAgent
     public Func<ValueTask<ChatMessage>>? InteractiveCallback { get; set; }
 
     /// <inheritdoc />
-    protected override Task<AgentRunResponse> RunCoreAsync(IReadOnlyCollection<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken)
+    protected override Task<AgentRunResponse> RunCoreAsync(IEnumerable<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken)
     {
         List<ChatMessage> allMessages = [.. messages];
         int originalMessageCount = allMessages.Count;
@@ -52,7 +52,7 @@ public sealed partial class HandoffOrchestration : OrchestratingAgent
     }
 
     /// <inheritdoc />
-    protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IReadOnlyCollection<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken)
+    protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IEnumerable<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken)
     {
         var state = checkpointState.Deserialize(OrchestrationJsonContext.Default.HandoffState) ?? throw new InvalidOperationException("The checkpoint state is invalid.");
 

dotnet/src/Microsoft.Agents.Orchestration/OrchestratingAgent.cs

@@ -65,7 +65,7 @@ public abstract partial class OrchestratingAgent : AIAgent
 
     /// <inheritdoc />
     public sealed override async Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+        IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
     {
         _ = Throw.IfNull(messages);
 
@@ -87,7 +87,7 @@ public abstract partial class OrchestratingAgent : AIAgent
 
     /// <inheritdoc />
     public sealed override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+        IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
         // TODO: There should be a RunAsync overload that returns an OrchestratingAgentStreamingResponse, which this then delegates to.
 
@@ -106,12 +106,12 @@ public abstract partial class OrchestratingAgent : AIAgent
     /// <param name="runtime">The runtime associated with the orchestration.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     public async ValueTask<OrchestratingAgentResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentRunOptions? options = null,
         IActorRuntimeContext? runtime = null,
         CancellationToken cancellationToken = default)
     {
-        Throw.IfNull(messages, nameof(messages));
+        var readonlyCollectionMessages = Throw.IfNull(messages) as IReadOnlyCollection<ChatMessage> ?? messages.ToList();
         cancellationToken.ThrowIfCancellationRequested();
 
         ILogger logger = this.LoggerFactory.CreateLogger(this.GetType().Name);
@@ -131,8 +131,8 @@ public abstract partial class OrchestratingAgent : AIAgent
 
         JsonElement? checkpoint = await this.ReadCheckpointAsync(context, cancellationToken).ConfigureAwait(false);
         Task<AgentRunResponse> completion = checkpoint is null ?
-            this.RunCoreAsync(messages, context, cancellationToken) :
-            this.ResumeCoreAsync(checkpoint.Value, messages, context, cancellationToken);
+            this.RunCoreAsync(readonlyCollectionMessages, context, cancellationToken) :
+            this.ResumeCoreAsync(checkpoint.Value, readonlyCollectionMessages, context, cancellationToken);
 
         if (logger.IsEnabled(LogLevel.Trace))
         {
@@ -148,7 +148,7 @@ public abstract partial class OrchestratingAgent : AIAgent
     /// <param name="messages">The input message.</param>
     /// <param name="context">The context for this operation.</param>
     /// <param name="cancellationToken">A cancellation token that can be used to cancel the operation.</param>
-    protected abstract Task<AgentRunResponse> RunCoreAsync(IReadOnlyCollection<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken);
+    protected abstract Task<AgentRunResponse> RunCoreAsync(IEnumerable<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken);
 
     /// <summary>
     /// Resumes processing of the orchestration.
@@ -157,7 +157,7 @@ public abstract partial class OrchestratingAgent : AIAgent
     /// <param name="newMessages">The new messages to be processed in addition to the checkpoint state.</param>
     /// <param name="context">The context for this operation.</param>
     /// <param name="cancellationToken">A cancellation token that can be used to cancel the operation.</param>
-    protected abstract Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IReadOnlyCollection<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken);
+    protected abstract Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IEnumerable<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken);
 
     /// <summary>
     /// Runs the agent with input messages and respond with both streamed and regular messages.
@@ -168,7 +168,7 @@ public abstract partial class OrchestratingAgent : AIAgent
     /// <param name="options">Options to use when invoking the agent.</param>
     /// <param name="cancellationToken">A cancellation token that can be used to cancel the operation.</param>
     /// <returns>A task that returns the response <see cref="ChatMessage"/>.</returns>
-    protected static async ValueTask<AgentRunResponse> RunAsync(AIAgent agent, OrchestratingAgentContext context, IReadOnlyCollection<ChatMessage> input, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+    protected static async ValueTask<AgentRunResponse> RunAsync(AIAgent agent, OrchestratingAgentContext context, IEnumerable<ChatMessage> input, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
     {
         // Utilize streaming iff a streaming callback is provided; otherwise, use the non-streaming API.
         AgentRunResponse response;

dotnet/src/Microsoft.Agents.Orchestration/SequentialOrchestration.cs

@@ -3,6 +3,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 using System.Text.Json;
 using System.Threading;
 using System.Threading.Tasks;
@@ -28,11 +29,11 @@ public sealed partial class SequentialOrchestration : OrchestratingAgent
     }
 
     /// <inheritdoc />
-    protected override Task<AgentRunResponse> RunCoreAsync(IReadOnlyCollection<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken) =>
-        this.ResumeAsync(0, messages, context, cancellationToken);
+    protected override Task<AgentRunResponse> RunCoreAsync(IEnumerable<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken) =>
+        this.ResumeAsync(0, messages as IReadOnlyCollection<ChatMessage> ?? messages.ToList(), context, cancellationToken);
 
     /// <inheritdoc />
-    protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IReadOnlyCollection<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken)
+    protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IEnumerable<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken)
     {
         var state = checkpointState.Deserialize(OrchestrationJsonContext.Default.SequentialState) ?? throw new InvalidOperationException("The checkpoint state is invalid.");
 

dotnet/src/Microsoft.Agents.Workflows/WorkflowHostAgent.cs

@@ -96,7 +96,7 @@ internal class WorkflowHostAgent : AIAgent
         }
     }
 
-    private async ValueTask<WorkflowThread> UpdateThreadAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, CancellationToken cancellation = default)
+    private async ValueTask<WorkflowThread> UpdateThreadAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, CancellationToken cancellation = default)
     {
         if (thread is null)
         {
@@ -114,7 +114,7 @@ internal class WorkflowHostAgent : AIAgent
 
     public override async
     Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
@@ -134,7 +134,7 @@ internal class WorkflowHostAgent : AIAgent
 
     public override async
     IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         [EnumeratorCancellation] CancellationToken cancellationToken = default)

dotnet/src/Microsoft.Agents.Workflows/WorkflowMessageStore.cs

@@ -25,7 +25,7 @@ internal class WorkflowMessageStore : IChatMessageStore
         this._chatMessages.AddRange(messages);
     }
 
-    public Task AddMessagesAsync(IReadOnlyCollection<ChatMessage> messages, CancellationToken cancellationToken)
+    public Task AddMessagesAsync(IEnumerable<ChatMessage> messages, CancellationToken cancellationToken)
     {
         this._chatMessages.AddRange(messages);
 

dotnet/src/Microsoft.Extensions.AI.Agents.A2A/A2AAgent.cs

@@ -52,7 +52,7 @@ internal sealed class A2AAgent : AIAgent
     }
 
     /// <inheritdoc/>
-    public override async Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+    public override async Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
     {
         ValidateInputMessages(messages);
 
@@ -98,7 +98,7 @@ internal sealed class A2AAgent : AIAgent
     }
 
     /// <inheritdoc/>
-    public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
         ValidateInputMessages(messages);
 
@@ -147,7 +147,7 @@ internal sealed class A2AAgent : AIAgent
     /// <inheritdoc/>
     public override string? Description => this._description ?? base.Description;
 
-    private static void ValidateInputMessages(IReadOnlyCollection<ChatMessage> messages)
+    private static void ValidateInputMessages(IEnumerable<ChatMessage> messages)
     {
         _ = Throw.IfNull(messages);
 

dotnet/src/Microsoft.Extensions.AI.Agents.A2A/Extensions/ChatMessageExtensions.cs

@@ -11,7 +11,7 @@ namespace Microsoft.Extensions.AI.Agents.A2A;
 /// </summary>
 internal static class ChatMessageExtensions
 {
-    internal static Message ToA2AMessage(this IReadOnlyCollection<ChatMessage> messages)
+    internal static Message ToA2AMessage(this IEnumerable<ChatMessage> messages)
     {
         List<Part> allParts = [];
 

dotnet/src/Microsoft.Extensions.AI.Agents.Abstractions/AIAgent.cs

@@ -112,7 +112,7 @@ public abstract class AIAgent
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
     {
-        return this.RunAsync((IReadOnlyCollection<ChatMessage>)[], thread, options, cancellationToken);
+        return this.RunAsync((IEnumerable<ChatMessage>)[], thread, options, cancellationToken);
     }
 
     /// <summary>
@@ -174,7 +174,7 @@ public abstract class AIAgent
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>A <see cref="AgentRunResponse"/> containing the list of <see cref="ChatMessage"/> items.</returns>
     public abstract Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default);
@@ -194,7 +194,7 @@ public abstract class AIAgent
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
     {
-        return this.RunStreamingAsync((IReadOnlyCollection<ChatMessage>)[], thread, options, cancellationToken);
+        return this.RunStreamingAsync((IEnumerable<ChatMessage>)[], thread, options, cancellationToken);
     }
 
     /// <summary>
@@ -256,7 +256,7 @@ public abstract class AIAgent
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>An async list of response items that each contain a <see cref="AgentRunResponseUpdate"/>.</returns>
     public abstract IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default);
@@ -285,14 +285,11 @@ public abstract class AIAgent
     /// <param name="messages">The messages to pass to the thread.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>An async task that completes once the notification is complete.</returns>
-    protected static async Task NotifyThreadOfNewMessagesAsync(AgentThread thread, IReadOnlyCollection<ChatMessage> messages, CancellationToken cancellationToken)
+    protected static async Task NotifyThreadOfNewMessagesAsync(AgentThread thread, IEnumerable<ChatMessage> messages, CancellationToken cancellationToken)
     {
         _ = Throw.IfNull(thread);
         _ = Throw.IfNull(messages);
 
-        if (messages.Count > 0)
-        {
-            await thread.OnNewMessagesAsync(messages, cancellationToken).ConfigureAwait(false);
-        }
+        await thread.OnNewMessagesAsync(messages, cancellationToken).ConfigureAwait(false);
     }
 }

dotnet/src/Microsoft.Extensions.AI.Agents.Abstractions/AgentThread.cs

@@ -139,7 +139,7 @@ public class AgentThread
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>A task that completes when the context has been updated.</returns>
     /// <exception cref="InvalidOperationException">The thread has been deleted.</exception>
-    protected internal virtual async Task OnNewMessagesAsync(IReadOnlyCollection<ChatMessage> newMessages, CancellationToken cancellationToken = default)
+    protected internal virtual async Task OnNewMessagesAsync(IEnumerable<ChatMessage> newMessages, CancellationToken cancellationToken = default)
     {
         switch (this)
         {

dotnet/src/Microsoft.Extensions.AI.Agents.Abstractions/DelegatingAIAgent.cs

@@ -54,7 +54,7 @@ public class DelegatingAIAgent : AIAgent
 
     /// <inheritdoc />
     public override Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
@@ -62,7 +62,7 @@ public class DelegatingAIAgent : AIAgent
 
     /// <inheritdoc />
     public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)

dotnet/src/Microsoft.Extensions.AI.Agents.Abstractions/IChatMessageStore.cs

@@ -42,7 +42,7 @@ public interface IChatMessageStore
     /// <param name="messages">The messages to add.</param>
     /// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
     /// <returns>An async task.</returns>
-    Task AddMessagesAsync(IReadOnlyCollection<ChatMessage> messages, CancellationToken cancellationToken = default);
+    Task AddMessagesAsync(IEnumerable<ChatMessage> messages, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Deserializes the state contained in the provided <see cref="JsonElement"/> into the properties on this store.

dotnet/src/Microsoft.Extensions.AI.Agents.Abstractions/InMemoryChatMessageStore.cs

@@ -61,15 +61,10 @@ public sealed class InMemoryChatMessageStore : IList<ChatMessage>, IChatMessageS
     }
 
     /// <inheritdoc />
-    public async Task AddMessagesAsync(IReadOnlyCollection<ChatMessage> messages, CancellationToken cancellationToken)
+    public async Task AddMessagesAsync(IEnumerable<ChatMessage> messages, CancellationToken cancellationToken)
     {
         _ = Throw.IfNull(messages);
 
-        if (messages.Count == 0)
-        {
-            return;
-        }
-
         this._messages.AddRange(messages);
 
         if (this._reducerTriggerEvent == ChatReducerTriggerEvent.AfterMessageAdded && this._chatReducer is not null)
@@ -172,7 +167,7 @@ public sealed class InMemoryChatMessageStore : IList<ChatMessage>, IChatMessageS
     {
         /// <summary>
         /// Trigger the reducer when a new message is added.
-        /// <see cref="AddMessagesAsync(IReadOnlyCollection{ChatMessage}, CancellationToken)"/> will only complete when reducer processing is done.
+        /// <see cref="AddMessagesAsync(IEnumerable{ChatMessage}, CancellationToken)"/> will only complete when reducer processing is done.
         /// </summary>
         AfterMessageAdded,
 

dotnet/src/Microsoft.Extensions.AI.Agents.CopilotStudio/CopilotStudioAgent.cs

@@ -41,7 +41,7 @@ public class CopilotStudioAgent : AIAgent
 
     /// <inheritdoc/>
     public override async Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
@@ -74,7 +74,7 @@ public class CopilotStudioAgent : AIAgent
 
     /// <inheritdoc/>
     public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         [EnumeratorCancellation] CancellationToken cancellationToken = default)

dotnet/src/Microsoft.Extensions.AI.Agents.Hosting/AgentProxy.cs

@@ -45,7 +45,7 @@ public sealed class AgentProxy : AIAgent
 
     /// <inheritdoc/>
     public override async Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
@@ -57,7 +57,7 @@ public sealed class AgentProxy : AIAgent
 
     /// <inheritdoc/>
     public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         [EnumeratorCancellation] CancellationToken cancellationToken = default)
@@ -70,7 +70,7 @@ public sealed class AgentProxy : AIAgent
         }
     }
 
-    private async Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, string threadId, CancellationToken cancellationToken)
+    private async Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, string threadId, CancellationToken cancellationToken)
     {
         var handle = await this.RunCoreAsync(messages, threadId, cancellationToken).ConfigureAwait(false);
         var response = await handle.GetResponseAsync(cancellationToken).ConfigureAwait(false);
@@ -85,7 +85,7 @@ public sealed class AgentProxy : AIAgent
     }
 
     private async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         string threadId,
         [EnumeratorCancellation] CancellationToken cancellationToken)
     {
@@ -123,7 +123,7 @@ public sealed class AgentProxy : AIAgent
         return agentProxyThread.ConversationId!;
     }
 
-    private async Task<ActorResponseHandle> RunCoreAsync(IReadOnlyCollection<ChatMessage> messages, string threadId, CancellationToken cancellationToken)
+    private async Task<ActorResponseHandle> RunCoreAsync(IEnumerable<ChatMessage> messages, string threadId, CancellationToken cancellationToken)
     {
         List<ChatMessage> newMessages = [.. messages];
 

dotnet/src/Microsoft.Extensions.AI.Agents.OpenAI/OpenAIChatClientAgent.cs

@@ -85,7 +85,7 @@ public class OpenAIChatClientAgent : AIAgent
 
     /// <inheritdoc/>
     public sealed override Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<Microsoft.Extensions.AI.ChatMessage> messages,
+        IEnumerable<Microsoft.Extensions.AI.ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
@@ -93,7 +93,7 @@ public class OpenAIChatClientAgent : AIAgent
 
     /// <inheritdoc/>
     public sealed override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<Microsoft.Extensions.AI.ChatMessage> messages,
+        IEnumerable<Microsoft.Extensions.AI.ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)

dotnet/src/Microsoft.Extensions.AI.Agents/ChatCompletion/ChatClientAgent.cs

@@ -2,6 +2,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
@@ -99,15 +100,15 @@ public sealed class ChatClientAgent : AIAgent
 
     /// <inheritdoc/>
     public override async Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
     {
-        _ = Throw.IfNull(messages);
+        var inputMessages = Throw.IfNull(messages) as IReadOnlyCollection<ChatMessage> ?? messages.ToList();
 
         (AgentThread safeThread, ChatOptions? chatOptions, List<ChatMessage> threadMessages) =
-            await this.PrepareThreadAndMessagesAsync(thread, messages, options, cancellationToken).ConfigureAwait(false);
+            await this.PrepareThreadAndMessagesAsync(thread, inputMessages, options, cancellationToken).ConfigureAwait(false);
 
         var agentName = this.GetLoggingAgentName();
 
@@ -115,14 +116,14 @@ public sealed class ChatClientAgent : AIAgent
 
         ChatResponse chatResponse = await this.ChatClient.GetResponseAsync(threadMessages, chatOptions, cancellationToken).ConfigureAwait(false);
 
-        this._logger.LogAgentChatClientInvokedAgent(nameof(RunAsync), this.Id, agentName, this._chatClientType, messages.Count);
+        this._logger.LogAgentChatClientInvokedAgent(nameof(RunAsync), this.Id, agentName, this._chatClientType, inputMessages.Count);
 
         // We can derive the type of supported thread from whether we have a conversation id,
         // so let's update it and set the conversation id for the service thread case.
         this.UpdateThreadWithTypeAndConversationId(safeThread, chatResponse.ConversationId);
 
         // Only notify the thread of new messages if the chatResponse was successful to avoid inconsistent messages state in the thread.
-        await NotifyThreadOfNewMessagesAsync(safeThread, messages, cancellationToken).ConfigureAwait(false);
+        await NotifyThreadOfNewMessagesAsync(safeThread, inputMessages, cancellationToken).ConfigureAwait(false);
 
         // Ensure that the author name is set for each message in the response.
         foreach (ChatMessage chatResponseMessage in chatResponse.Messages)
@@ -140,12 +141,12 @@ public sealed class ChatClientAgent : AIAgent
 
     /// <inheritdoc/>
     public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
-        var inputMessages = Throw.IfNull(messages);
+        var inputMessages = Throw.IfNull(messages) as IReadOnlyCollection<ChatMessage> ?? messages.ToList();
 
         (AgentThread safeThread, ChatOptions? chatOptions, List<ChatMessage> threadMessages) =
             await this.PrepareThreadAndMessagesAsync(thread, inputMessages, options, cancellationToken).ConfigureAwait(false);
@@ -334,7 +335,7 @@ public sealed class ChatClientAgent : AIAgent
     /// <returns>A tuple containing the thread, chat options, and thread messages.</returns>
     private async Task<(AgentThread AgentThread, ChatOptions? ChatOptions, List<ChatMessage> ThreadMessages)> PrepareThreadAndMessagesAsync(
         AgentThread? thread,
-        IReadOnlyCollection<ChatMessage> inputMessages,
+        IEnumerable<ChatMessage> inputMessages,
         AgentRunOptions? runOptions,
         CancellationToken cancellationToken)
     {

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

@@ -123,23 +123,23 @@ public sealed partial class OpenTelemetryAgent : DelegatingAIAgent, IDisposable
 
     /// <inheritdoc/>
     public override async Task<AgentRunResponse> RunAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         CancellationToken cancellationToken = default)
     {
-        _ = Throw.IfNull(messages);
+        var inputMessages = Throw.IfNull(messages) as IReadOnlyCollection<ChatMessage> ?? messages.ToList();
 
-        using Activity? activity = this.CreateAndConfigureActivity(OpenTelemetryConsts.GenAI.Operation.NameValues.InvokeAgent, messages, thread);
+        using Activity? activity = this.CreateAndConfigureActivity(OpenTelemetryConsts.GenAI.Operation.NameValues.InvokeAgent, inputMessages, thread);
         Stopwatch? stopwatch = this._operationDurationHistogram.Enabled ? Stopwatch.StartNew() : null;
 
-        this.LogChatMessages(messages);
+        this.LogChatMessages(inputMessages);
 
         AgentRunResponse? response = null;
         Exception? error = null;
         try
         {
-            response = await base.RunAsync(messages, thread, options, cancellationToken).ConfigureAwait(false);
+            response = await base.RunAsync(inputMessages, thread, options, cancellationToken).ConfigureAwait(false);
             return response;
         }
         catch (Exception ex)
@@ -149,30 +149,30 @@ public sealed partial class OpenTelemetryAgent : DelegatingAIAgent, IDisposable
         }
         finally
         {
-            this.TraceResponse(activity, response, error, stopwatch, messages.Count, isStreaming: false);
+            this.TraceResponse(activity, response, error, stopwatch, inputMessages.Count, isStreaming: false);
         }
     }
 
     /// <inheritdoc/>
     public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-        IReadOnlyCollection<ChatMessage> messages,
+        IEnumerable<ChatMessage> messages,
         AgentThread? thread = null,
         AgentRunOptions? options = null,
         [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
-        _ = Throw.IfNull(messages);
+        var inputMessages = Throw.IfNull(messages) as IReadOnlyCollection<ChatMessage> ?? messages.ToList();
 
-        using Activity? activity = this.CreateAndConfigureActivity(OpenTelemetryConsts.GenAI.Operation.NameValues.InvokeAgent, messages, thread);
+        using Activity? activity = this.CreateAndConfigureActivity(OpenTelemetryConsts.GenAI.Operation.NameValues.InvokeAgent, inputMessages, thread);
         Stopwatch? stopwatch = this._operationDurationHistogram.Enabled ? Stopwatch.StartNew() : null;
 
         IAsyncEnumerable<AgentRunResponseUpdate> updates;
         try
         {
-            updates = base.RunStreamingAsync(messages, thread, options, cancellationToken);
+            updates = base.RunStreamingAsync(inputMessages, thread, options, cancellationToken);
         }
         catch (Exception ex)
         {
-            this.TraceResponse(activity, response: null, ex, stopwatch, messages.Count, isStreaming: true);
+            this.TraceResponse(activity, response: null, ex, stopwatch, inputMessages.Count, isStreaming: true);
             throw;
         }
 
@@ -206,7 +206,7 @@ public sealed partial class OpenTelemetryAgent : DelegatingAIAgent, IDisposable
         }
         finally
         {
-            this.TraceResponse(activity, trackedUpdates.ToAgentRunResponse(), error, stopwatch, messages.Count, isStreaming: true);
+            this.TraceResponse(activity, trackedUpdates.ToAgentRunResponse(), error, stopwatch, inputMessages.Count, isStreaming: true);
             await responseEnumerator.DisposeAsync().ConfigureAwait(false);
         }
     }

dotnet/tests/Microsoft.Agents.Orchestration.UnitTests/MockAgent.cs

@@ -36,7 +36,7 @@ internal sealed class MockAgent(int index) : AIAgent
         return new AgentThread() { ConversationId = Guid.NewGuid().ToString() };
     }
 
-    public override Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+    public override Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
     {
         this.InvokeCount++;
         if (thread == null)
@@ -48,7 +48,7 @@ internal sealed class MockAgent(int index) : AIAgent
         return Task.FromResult(new AgentRunResponse(messages: [.. this.Response]));
     }
 
-    public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+    public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
     {
         this.InvokeCount++;
 

dotnet/tests/Microsoft.Agents.Orchestration.UnitTests/OrchestrationResultTests.cs

@@ -80,18 +80,18 @@ public class OrchestrationResultTests
 
     private sealed class MockOrchestratingAgent() : OrchestratingAgent([new MockAgent()])
     {
-        protected override Task<AgentRunResponse> RunCoreAsync(IReadOnlyCollection<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken) =>
+        protected override Task<AgentRunResponse> RunCoreAsync(IEnumerable<ChatMessage> messages, OrchestratingAgentContext context, CancellationToken cancellationToken) =>
             throw new NotSupportedException();
 
-        protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IReadOnlyCollection<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken) =>
+        protected override Task<AgentRunResponse> ResumeCoreAsync(JsonElement checkpointState, IEnumerable<ChatMessage> newMessages, OrchestratingAgentContext context, CancellationToken cancellationToken) =>
             throw new NotSupportedException();
     }
 
     private sealed class MockAgent : AIAgent
     {
-        public override Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default) =>
+        public override Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default) =>
             throw new NotSupportedException();
-        public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default) =>
+        public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default) =>
             throw new NotSupportedException();
     }
 }

dotnet/tests/Microsoft.Agents.Workflows.UnitTests/RepresentationTests.cs

@@ -22,12 +22,12 @@ public class RepresentationTests
 
     private sealed class TestAgent : AIAgent
     {
-        public override Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+        public override Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
         {
             throw new NotImplementedException();
         }
 
-        public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+        public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
         {
             throw new NotImplementedException();
         }

dotnet/tests/Microsoft.Agents.Workflows.UnitTests/Sample/06_GroupChat_Workflow.cs

@@ -95,7 +95,7 @@ internal sealed class HelloAgent(string id = nameof(HelloAgent)) : AIAgent
     public override string Id => id;
     public override string? Name => id;
 
-    public override async Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+    public override async Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
     {
         IEnumerable<AgentRunResponseUpdate> update = [
             await this.RunStreamingAsync(messages, thread, options, cancellationToken)
@@ -105,7 +105,7 @@ internal sealed class HelloAgent(string id = nameof(HelloAgent)) : AIAgent
         return update.ToAgentRunResponse();
     }
 
-    public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
         AgentRunResponseUpdate response = new(ChatRole.Assistant, "Hello World!")
         {
@@ -126,7 +126,7 @@ internal sealed class EchoAgent(string id = nameof(EchoAgent)) : AIAgent
     public override string Id => id;
     public override string? Name => id;
 
-    public override async Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+    public override async Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
     {
         IEnumerable<AgentRunResponseUpdate> update = [
             await this.RunStreamingAsync(messages, thread, options, cancellationToken)
@@ -136,15 +136,17 @@ internal sealed class EchoAgent(string id = nameof(EchoAgent)) : AIAgent
         return update.ToAgentRunResponse();
     }
 
-    public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+    public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
-        if (messages.Count == 0)
+        var messagesList = messages as IReadOnlyCollection<ChatMessage> ?? messages.ToList();
+
+        if (messagesList.Count == 0)
         {
             throw new ArgumentException("No messages provided to echo.", nameof(messages));
         }
 
         StringBuilder collectedText = new(Prefix);
-        foreach (string messageText in messages.Select(message => message.Text)
+        foreach (string messageText in messagesList.Select(message => message.Text)
                                                .Where(text => !string.IsNullOrEmpty(text)))
         {
             collectedText.AppendLine(messageText);

dotnet/tests/Microsoft.Agents.Workflows.UnitTests/SpecializedExecutorSmokeTests.cs

@@ -56,7 +56,7 @@ public class SpecializedExecutorSmokeTests
 
         public List<ChatMessage> Messages { get; } = Validate(messages) ?? [];
 
-        public override Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+        public override Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
         {
             return Task.FromResult(new AgentRunResponse(this.Messages)
             {
@@ -65,7 +65,7 @@ public class SpecializedExecutorSmokeTests
             });
         }
 
-        public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
+        public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
         {
             string responseId = Guid.NewGuid().ToString("N");
             foreach (ChatMessage message in this.Messages)

dotnet/tests/Microsoft.Extensions.AI.Agents.Abstractions.UnitTests/AIAgentTests.cs

@@ -361,13 +361,13 @@ public class AIAgentTests
 
     private sealed class MockAgent : AIAgent
     {
-        public static new Task NotifyThreadOfNewMessagesAsync(AgentThread thread, IReadOnlyCollection<ChatMessage> messages, CancellationToken cancellationToken)
+        public static new Task NotifyThreadOfNewMessagesAsync(AgentThread thread, IEnumerable<ChatMessage> messages, CancellationToken cancellationToken)
         {
             return AIAgent.NotifyThreadOfNewMessagesAsync(thread, messages, cancellationToken);
         }
 
         public override Task<AgentRunResponse> RunAsync(
-            IReadOnlyCollection<ChatMessage> messages,
+            IEnumerable<ChatMessage> messages,
             AgentThread? thread = null,
             AgentRunOptions? options = null,
             CancellationToken cancellationToken = default)
@@ -376,7 +376,7 @@ public class AIAgentTests
         }
 
         public override IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-            IReadOnlyCollection<ChatMessage> messages,
+            IEnumerable<ChatMessage> messages,
             AgentThread? thread = null,
             AgentRunOptions? options = null,
             CancellationToken cancellationToken = default)

dotnet/tests/Microsoft.Extensions.AI.Agents.Hosting.UnitTests/AgentActorTests.cs

@@ -175,7 +175,7 @@ public class AgentActorTests
         public bool RunStreamingAsyncCalled { get; private set; }
         public AgentThread? ThreadUsedInRunStreamingAsync { get; private set; }
 
-        public override Task<AgentRunResponse> RunAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
+        public override Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
         {
             this.ThreadUsedInRunStreamingAsync = thread;
             return Task.FromResult(new AgentRunResponse
@@ -184,7 +184,7 @@ public class AgentActorTests
             });
         }
 
-        public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IReadOnlyCollection<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken = default)
+        public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [System.Runtime.CompilerServices.EnumeratorCancellation] CancellationToken cancellationToken = default)
         {
             this.RunStreamingAsyncCalled = true;
             this.ThreadUsedInRunStreamingAsync = thread;

dotnet/tests/Microsoft.Extensions.AI.Agents.UnitTests/AgentAIFunctionFactoryTests.cs

@@ -306,7 +306,7 @@ public class AgentAIFunctionFactoryTests
         public int RunAsyncCallCount { get; private set; }
 
         public override Task<AgentRunResponse> RunAsync(
-            IReadOnlyCollection<ChatMessage> messages,
+            IEnumerable<ChatMessage> messages,
             AgentThread? thread = null,
             AgentRunOptions? options = null,
             CancellationToken cancellationToken = default)
@@ -324,7 +324,7 @@ public class AgentAIFunctionFactoryTests
         }
 
         public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(
-            IReadOnlyCollection<ChatMessage> messages,
+            IEnumerable<ChatMessage> messages,
             AgentThread? thread = null,
             AgentRunOptions? options = null,
             [EnumeratorCancellation] CancellationToken cancellationToken = default)