From 202bfdc376d4961b3eda3211a668b7fb54475215 Mon Sep 17 00:00:00 2001
From: SergeyMenshykh <68852919+SergeyMenshykh@users.noreply.github.com>
Date: Thu, 23 Oct 2025 15:37:14 +0100
Subject: [PATCH] allow a2a agent to accept non-user messages (#1661)

---
 .../src/Microsoft.Agents.AI.A2A/A2AAgent.cs   | 17 ++----------
 .../A2AAgentTests.cs                          | 26 ++++++++++++-------
 2 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/dotnet/src/Microsoft.Agents.AI.A2A/A2AAgent.cs b/dotnet/src/Microsoft.Agents.AI.A2A/A2AAgent.cs
index 966871b534..cafbf90b87 100644
--- a/dotnet/src/Microsoft.Agents.AI.A2A/A2AAgent.cs
+++ b/dotnet/src/Microsoft.Agents.AI.A2A/A2AAgent.cs
@@ -72,7 +72,7 @@ internal sealed class A2AAgent : AIAgent
     /// <inheritdoc/>
     public override async Task<AgentRunResponse> RunAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, CancellationToken cancellationToken = default)
     {
-        ValidateInputMessages(messages);
+        _ = Throw.IfNull(messages);
 
         var a2aMessage = messages.ToA2AMessage();
 
@@ -124,7 +124,7 @@ internal sealed class A2AAgent : AIAgent
     /// <inheritdoc/>
     public override async IAsyncEnumerable<AgentRunResponseUpdate> RunStreamingAsync(IEnumerable<ChatMessage> messages, AgentThread? thread = null, AgentRunOptions? options = null, [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
-        ValidateInputMessages(messages);
+        _ = Throw.IfNull(messages);
 
         var a2aMessage = messages.ToA2AMessage();
 
@@ -177,19 +177,6 @@ internal sealed class A2AAgent : AIAgent
     /// <inheritdoc/>
     public override string? Description => this._description ?? base.Description;
 
-    private static void ValidateInputMessages(IEnumerable<ChatMessage> messages)
-    {
-        _ = Throw.IfNull(messages);
-
-        foreach (var message in messages)
-        {
-            if (message.Role != ChatRole.User)
-            {
-                throw new ArgumentException($"All input messages for A2A agents must have the role '{ChatRole.User}'. Found '{message.Role}'.", nameof(messages));
-            }
-        }
-    }
-
     private static void UpdateThreadConversationId(A2AAgentThread? thread, string? contextId)
     {
         if (thread is null)
diff --git a/dotnet/tests/Microsoft.Agents.AI.A2A.UnitTests/A2AAgentTests.cs b/dotnet/tests/Microsoft.Agents.AI.A2A.UnitTests/A2AAgentTests.cs
index 39d486f114..9399d99528 100644
--- a/dotnet/tests/Microsoft.Agents.AI.A2A.UnitTests/A2AAgentTests.cs
+++ b/dotnet/tests/Microsoft.Agents.AI.A2A.UnitTests/A2AAgentTests.cs
@@ -74,17 +74,18 @@ public sealed class A2AAgentTests : IDisposable
     }
 
     [Fact]
-    public async Task RunAsync_NonUserRoleMessages_ThrowsArgumentExceptionAsync()
+    public async Task RunAsync_AllowsNonUserRoleMessagesAsync()
     {
         // Arrange
         var inputMessages = new List<ChatMessage>
         {
+            new(ChatRole.System, "I am a system message"),
             new(ChatRole.Assistant, "I am an assistant message"),
             new(ChatRole.User, "Valid user message")
         };
 
         // Act & Assert
-        await Assert.ThrowsAsync<ArgumentException>(() => this._agent.RunAsync(inputMessages));
+        await this._agent.RunAsync(inputMessages);
     }
 
     [Fact]
@@ -345,21 +346,28 @@ public sealed class A2AAgentTests : IDisposable
     }
 
     [Fact]
-    public async Task RunStreamingAsync_NonUserRoleMessages_ThrowsArgumentExceptionAsync()
+    public async Task RunStreamingAsync_AllowsNonUserRoleMessagesAsync()
     {
         // Arrange
+        this._handler.StreamingResponseToReturn = new AgentMessage()
+        {
+            MessageId = "stream-1",
+            Role = MessageRole.Agent,
+            Parts = [new TextPart { Text = "Response" }],
+            ContextId = "new-stream-context"
+        };
+
         var inputMessages = new List<ChatMessage>
         {
-            new(ChatRole.Assistant, "I am an assistant message")
+            new(ChatRole.System, "I am a system message"),
+            new(ChatRole.Assistant, "I am an assistant message"),
+            new(ChatRole.User, "Valid user message")
         };
 
         // Act & Assert
-        await Assert.ThrowsAsync<ArgumentException>(async () =>
+        await foreach (var _ in this._agent.RunStreamingAsync(inputMessages))
         {
-            await foreach (var update in this._agent.RunStreamingAsync(inputMessages))
-            {
-            }
-        });
+        }
     }
 
     [Fact]