.NET: Migrate A2A agent to A2A SDK v1

dotnet/Directory.Packages.props

@@ -101,8 +101,8 @@
     <PackageVersion Include="Microsoft.Agents.Authentication.Msal" Version="1.3.171-beta" />
     <PackageVersion Include="Microsoft.Agents.Hosting.AspNetCore" Version="1.3.171-beta" />
     <!-- A2A -->
-    <PackageVersion Include="A2A" Version="0.3.4-preview" />
-    <PackageVersion Include="A2A.AspNetCore" Version="0.3.4-preview" />
+    <PackageVersion Include="A2A" Version="1.0.0-preview" />
+    <PackageVersion Include="A2A.AspNetCore" Version="1.0.0-preview" />
     <!-- MCP -->
     <PackageVersion Include="ModelContextProtocol" Version="1.1.0" />
     <!-- Inference SDKs -->

dotnet/agent-framework-dotnet.slnx

@@ -281,6 +281,7 @@
     <File Path="samples/04-hosting/A2A/README.md" />
     <Project Path="samples/04-hosting/A2A/A2AAgent_AsFunctionTools/A2AAgent_AsFunctionTools.csproj" />
     <Project Path="samples/04-hosting/A2A/A2AAgent_PollingForTaskCompletion/A2AAgent_PollingForTaskCompletion.csproj" />
+    <Project Path="samples/04-hosting/A2A/A2AAgent_StreamReconnection/A2AAgent_StreamReconnection.csproj" />
   </Folder>  
   <Folder Name="/Samples/05-end-to-end/">
     <Project Path="samples/05-end-to-end/AgentWithPurview/AgentWithPurview.csproj" />

dotnet/samples/04-hosting/A2A/A2AAgent_PollingForTaskCompletion/A2AAgent_PollingForTaskCompletion.csproj

@@ -2,7 +2,7 @@
 
   <PropertyGroup>
     <OutputType>Exe</OutputType>
-    <TargetFramework>net10.0</TargetFramework>
+    <TargetFrameworks>net10.0</TargetFrameworks>
 
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
@@ -13,7 +13,6 @@
     <PackageReference Include="Azure.AI.OpenAI" />
     <PackageReference Include="Azure.Identity" />
     <PackageReference Include="Microsoft.Extensions.Hosting" />
-    <PackageReference Include="System.Net.ServerSentEvents" />
   </ItemGroup>
 
   <ItemGroup>

dotnet/samples/04-hosting/A2A/A2AAgent_PollingForTaskCompletion/Program.cs

@@ -18,8 +18,12 @@
 
 AgentSession session = await agent.CreateSessionAsync();
 
+// AllowBackgroundResponses must be true so the server returns immediately with a continuation token
+// instead of blocking until the task is complete.
+AgentRunOptions options = new() { AllowBackgroundResponses = true };
+
 // Start the initial run with a long-running task.
-AgentResponse response = await agent.RunAsync("Conduct a comprehensive analysis of quantum computing applications in cryptography, including recent breakthroughs, implementation challenges, and future roadmap. Please include diagrams and visual representations to illustrate complex concepts.", session);
+AgentResponse response = await agent.RunAsync("Conduct a comprehensive analysis of quantum computing applications in cryptography, including recent breakthroughs, implementation challenges, and future roadmap. Please include diagrams and visual representations to illustrate complex concepts.", session, options: options);
 
 // Poll until the response is complete.
 while (response.ContinuationToken is { } token)

dotnet/samples/04-hosting/A2A/A2AAgent_StreamReconnection/A2AAgent_StreamReconnection.csproj

@@ -0,0 +1,23 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="A2A" />
+    <PackageReference Include="Azure.AI.OpenAI" />
+    <PackageReference Include="Azure.Identity" />
+    <PackageReference Include="Microsoft.Extensions.Hosting" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.A2A\Microsoft.Agents.AI.A2A.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.OpenAI\Microsoft.Agents.AI.OpenAI.csproj" />
+  </ItemGroup>
+
+</Project>

dotnet/samples/04-hosting/A2A/A2AAgent_StreamReconnection/Program.cs

@@ -0,0 +1,55 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+// This sample demonstrates how to reconnect to an A2A agent's streaming response using continuation tokens,
+// allowing recovery from stream interruptions without losing progress.
+
+using A2A;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+
+var a2aAgentHost = Environment.GetEnvironmentVariable("A2A_AGENT_HOST") ?? throw new InvalidOperationException("A2A_AGENT_HOST is not set.");
+
+// Initialize an A2ACardResolver to get an A2A agent card.
+A2ACardResolver agentCardResolver = new(new Uri(a2aAgentHost));
+
+// Get the agent card
+AgentCard agentCard = await agentCardResolver.GetAgentCardAsync();
+
+// Create an instance of the AIAgent for an existing A2A agent specified by the agent card.
+AIAgent agent = agentCard.AsAIAgent();
+
+AgentSession session = await agent.CreateSessionAsync();
+
+ResponseContinuationToken? continuationToken = null;
+
+await foreach (var update in agent.RunStreamingAsync("Conduct a comprehensive analysis of quantum computing applications in cryptography, including recent breakthroughs, implementation challenges, and future roadmap. Please include diagrams and visual representations to illustrate complex concepts.", session))
+{
+    // Saving the continuation token to be able to reconnect to the same response stream later.
+    // Note: Continuation tokens are only returned for long-running tasks. If the underlying A2A agent
+    // returns a message instead of a task, the continuation token will not be initialized.
+    // A2A agents do not support stream resumption from a specific point in the stream,
+    // but only reconnection to obtain the same response stream from the beginning.
+    // So, A2A agents will return an initialized continuation token in the first update
+    // representing the beginning of the stream, and it will be null in all subsequent updates.
+    if (update.ContinuationToken is { } token)
+    {
+        continuationToken = token;
+    }
+
+    // Imitating stream interruption
+    break;
+}
+
+// Reconnect to the same response stream using the continuation token obtained from the previous stream.
+// As a first update, the agent will return an update representing the current state of the response at the moment of calling
+// RunStreamingAsync with the same continuation token, followed by other updates until the end of the stream is reached.
+if (continuationToken is not null)
+{
+    await foreach (var update in agent.RunStreamingAsync(session, options: new() { ContinuationToken = continuationToken }))
+    {
+        if (!string.IsNullOrEmpty(update.Text))
+        {
+            Console.WriteLine(update);
+        }
+    }
+}

dotnet/samples/04-hosting/A2A/A2AAgent_StreamReconnection/README.md

@@ -0,0 +1,29 @@
+# A2A Agent Stream Reconnection
+
+This sample demonstrates how to reconnect to an A2A agent's streaming response using continuation tokens, allowing recovery from stream interruptions without losing progress.
+
+The sample:
+
+- Connects to an A2A agent server specified in the `A2A_AGENT_HOST` environment variable
+- Sends a request to the agent and begins streaming the response
+- Captures a continuation token from the stream for later reconnection
+- Simulates a stream interruption by breaking out of the streaming loop
+- Reconnects to the same response stream using the captured continuation token
+- Displays the response received after reconnection
+
+This pattern is useful when network interruptions or other failures may disrupt an ongoing streaming response, and you need to recover and continue processing.
+
+> **Note:** Continuation tokens are only available when the underlying A2A agent returns a task. If the agent returns a message instead, the continuation token will not be initialized and stream reconnection is not applicable.
+
+# Prerequisites
+
+Before you begin, ensure you have the following prerequisites:
+
+- .NET 10.0 SDK or later
+- An A2A agent server running and accessible via HTTP
+
+Set the following environment variable:
+
+```powershell
+$env:A2A_AGENT_HOST="http://localhost:5000"  # Replace with your A2A agent server host
+```

dotnet/samples/04-hosting/A2A/README.md

@@ -15,6 +15,7 @@ See the README.md for each sample for the prerequisites for that sample.
 |---|---|
 |[A2A Agent As Function Tools](./A2AAgent_AsFunctionTools/)|This sample demonstrates how to represent an A2A agent as a set of function tools, where each function tool corresponds to a skill of the A2A agent, and register these function tools with another AI agent so it can leverage the A2A agent's skills.|
 |[A2A Agent Polling For Task Completion](./A2AAgent_PollingForTaskCompletion/)|This sample demonstrates how to poll for long-running task completion using continuation tokens with an A2A agent.|
+|[A2A Agent Stream Reconnection](./A2AAgent_StreamReconnection/)|This sample demonstrates how to reconnect to an A2A agent's streaming response using continuation tokens, allowing recovery from stream interruptions.|
 
 ## Running the samples from the console
 

dotnet/samples/05-end-to-end/A2AClientServer/A2AClient/Program.cs

@@ -62,12 +62,10 @@ private static async Task HandleCommandsAsync(CancellationToken cancellationToke
                 }
 
                 var agentResponse = await hostAgent.Agent!.RunAsync(message, session, cancellationToken: cancellationToken);
-                foreach (var chatMessage in agentResponse.Messages)
-                {
-                    Console.ForegroundColor = ConsoleColor.Cyan;
-                    Console.WriteLine($"\nAgent: {chatMessage.Text}");
-                    Console.ResetColor();
-                }
+
+                Console.ForegroundColor = ConsoleColor.Cyan;
+                Console.WriteLine($"\nAgent: {agentResponse.Text}");
+                Console.ResetColor();
             }
         }
         catch (Exception ex)

dotnet/samples/05-end-to-end/A2AClientServer/A2AServer/HostAgentFactory.cs

@@ -12,7 +12,7 @@ namespace A2AServer;
 
 internal static class HostAgentFactory
 {
-    internal static async Task<(AIAgent, AgentCard)> CreateFoundryHostAgentAsync(string agentType, string model, string endpoint, string agentName, IList<AITool>? tools = null)
+    internal static async Task<(AIAgent, AgentCard)> CreateFoundryHostAgentAsync(string agentType, string model, string endpoint, string agentName, string[] agentUrls, IList<AITool>? tools = null)
     {
         // WARNING: DefaultAzureCredential is convenient for development but requires careful consideration in production.
         // In production, consider using a specific credential (e.g., ManagedIdentityCredential) to avoid
@@ -24,34 +24,34 @@ internal static class HostAgentFactory
 
         AgentCard agentCard = agentType.ToUpperInvariant() switch
         {
-            "INVOICE" => GetInvoiceAgentCard(),
-            "POLICY" => GetPolicyAgentCard(),
-            "LOGISTICS" => GetLogisticsAgentCard(),
+            "INVOICE" => GetInvoiceAgentCard(agentUrls),
+            "POLICY" => GetPolicyAgentCard(agentUrls),
+            "LOGISTICS" => GetLogisticsAgentCard(agentUrls),
             _ => throw new ArgumentException($"Unsupported agent type: {agentType}"),
         };
 
         return new(agent, agentCard);
     }
 
-    internal static async Task<(AIAgent, AgentCard)> CreateChatCompletionHostAgentAsync(string agentType, string model, string apiKey, string name, string instructions, IList<AITool>? tools = null)
+    internal static async Task<(AIAgent, AgentCard)> CreateChatCompletionHostAgentAsync(string agentType, string model, string apiKey, string name, string instructions, string[] agentUrls, IList<AITool>? tools = null)
     {
         AIAgent agent = new OpenAIClient(apiKey)
              .GetChatClient(model)
              .AsAIAgent(instructions, name, tools: tools);
 
         AgentCard agentCard = agentType.ToUpperInvariant() switch
         {
-            "INVOICE" => GetInvoiceAgentCard(),
-            "POLICY" => GetPolicyAgentCard(),
-            "LOGISTICS" => GetLogisticsAgentCard(),
+            "INVOICE" => GetInvoiceAgentCard(agentUrls),
+            "POLICY" => GetPolicyAgentCard(agentUrls),
+            "LOGISTICS" => GetLogisticsAgentCard(agentUrls),
             _ => throw new ArgumentException($"Unsupported agent type: {agentType}"),
         };
 
         return new(agent, agentCard);
     }
 
     #region private
-    private static AgentCard GetInvoiceAgentCard()
+    private static AgentCard GetInvoiceAgentCard(string[] agentUrls)
     {
         var capabilities = new AgentCapabilities()
         {
@@ -80,10 +80,11 @@ private static AgentCard GetInvoiceAgentCard()
             DefaultOutputModes = ["text"],
             Capabilities = capabilities,
             Skills = [invoiceQuery],
+            SupportedInterfaces = CreateAgentInterfaces(agentUrls)
         };
     }
 
-    private static AgentCard GetPolicyAgentCard()
+    private static AgentCard GetPolicyAgentCard(string[] agentUrls)
     {
         var capabilities = new AgentCapabilities()
         {
@@ -112,10 +113,11 @@ private static AgentCard GetPolicyAgentCard()
             DefaultOutputModes = ["text"],
             Capabilities = capabilities,
             Skills = [policyQuery],
+            SupportedInterfaces = CreateAgentInterfaces(agentUrls)
         };
     }
 
-    private static AgentCard GetLogisticsAgentCard()
+    private static AgentCard GetLogisticsAgentCard(string[] agentUrls)
     {
         var capabilities = new AgentCapabilities()
         {
@@ -144,7 +146,18 @@ private static AgentCard GetLogisticsAgentCard()
             DefaultOutputModes = ["text"],
             Capabilities = capabilities,
             Skills = [logisticsQuery],
+            SupportedInterfaces = CreateAgentInterfaces(agentUrls)
         };
     }
+
+    private static List<AgentInterface> CreateAgentInterfaces(string[] agentUrls)
+    {
+        return agentUrls.Select(url => new AgentInterface
+        {
+            Url = url,
+            ProtocolBinding = "JSONRPC",
+            ProtocolVersion = "1.0",
+        }).ToList();
+    }
     #endregion
 }

dotnet/samples/05-end-to-end/A2AClientServer/A2AServer/Program.cs

@@ -38,14 +38,15 @@
 string? apiKey = configuration["OPENAI_API_KEY"];
 string model = configuration["OPENAI_CHAT_MODEL_NAME"] ?? "gpt-4o-mini";
 string? endpoint = configuration["AZURE_AI_PROJECT_ENDPOINT"];
+string[] agentUrls = (app.Configuration["urls"] ?? "http://localhost:5000").Split(';');
 
 var invoiceQueryPlugin = new InvoiceQuery();
 IList<AITool> tools =
-    [
+[
     AIFunctionFactory.Create(invoiceQueryPlugin.QueryInvoices),
     AIFunctionFactory.Create(invoiceQueryPlugin.QueryByTransactionId),
     AIFunctionFactory.Create(invoiceQueryPlugin.QueryByInvoiceId)
-    ];
+];
 
 AIAgent hostA2AAgent;
 AgentCard hostA2AAgentCard;
@@ -54,9 +55,9 @@
 {
     (hostA2AAgent, hostA2AAgentCard) = agentType.ToUpperInvariant() switch
     {
-        "INVOICE" => await HostAgentFactory.CreateFoundryHostAgentAsync(agentType, model, endpoint, agentName, tools),
-        "POLICY" => await HostAgentFactory.CreateFoundryHostAgentAsync(agentType, model, endpoint, agentName),
-        "LOGISTICS" => await HostAgentFactory.CreateFoundryHostAgentAsync(agentType, model, endpoint, agentName),
+        "INVOICE" => await HostAgentFactory.CreateFoundryHostAgentAsync(agentType, model, endpoint, agentName, agentUrls, tools),
+        "POLICY" => await HostAgentFactory.CreateFoundryHostAgentAsync(agentType, model, endpoint, agentName, agentUrls),
+        "LOGISTICS" => await HostAgentFactory.CreateFoundryHostAgentAsync(agentType, model, endpoint, agentName, agentUrls),
         _ => throw new ArgumentException($"Unsupported agent type: {agentType}"),
     };
 }
@@ -68,7 +69,7 @@
             agentType, model, apiKey, "InvoiceAgent",
             """
             You specialize in handling queries related to invoices.
-            """, tools),
+            """, agentUrls, tools),
         "POLICY" => await HostAgentFactory.CreateChatCompletionHostAgentAsync(
             agentType, model, apiKey, "PolicyAgent",
             """
@@ -84,7 +85,7 @@ You specialize in handling queries related to policies and customer communicatio
             resolution in SAP CRM and notify the customer via email within 2 business days, referencing the
             original invoice and the credit memo number. Use the 'Formal Credit Notification' email
             template."
-            """),
+            """, agentUrls),
         "LOGISTICS" => await HostAgentFactory.CreateChatCompletionHostAgentAsync(
             agentType, model, apiKey, "LogisticsAgent",
             """
@@ -95,7 +96,7 @@ You specialize in handling queries related to logistics.
             Shipment number: SHPMT-SAP-001
             Item: TSHIRT-RED-L
             Quantity: 900
-            """),
+            """, agentUrls),
         _ => throw new ArgumentException($"Unsupported agent type: {agentType}"),
     };
 }
@@ -104,10 +105,9 @@ You specialize in handling queries related to logistics.
     throw new ArgumentException("Either A2AServer:ApiKey or A2AServer:ConnectionString & agentName must be provided");
 }
 
-var a2aTaskManager = app.MapA2A(
+app.MapA2A(
     hostA2AAgent,
     path: "/",
-    agentCard: hostA2AAgentCard,
-    taskManager => app.MapWellKnownAgentCard(taskManager, "/"));
+    agentCard: hostA2AAgentCard);
 
 await app.RunAsync();

dotnet/samples/05-end-to-end/AgentWebChat/AgentWebChat.Web/A2AAgentClient.cs

@@ -43,20 +43,21 @@ public override async IAsyncEnumerable<AgentResponseUpdate> RunStreamingAsync(
         {
             // Convert all messages to A2A parts and create a single message
             var parts = messages.ToParts();
-            var a2aMessage = new AgentMessage
+            var a2aMessage = new Message
             {
                 MessageId = Guid.NewGuid().ToString("N"),
                 ContextId = contextId,
-                Role = MessageRole.User,
+                Role = Role.User,
                 Parts = parts
             };
 
-            var messageSendParams = new MessageSendParams { Message = a2aMessage };
+            var messageSendParams = new SendMessageRequest { Message = a2aMessage };
             var a2aResponse = await a2aClient.SendMessageAsync(messageSendParams, cancellationToken);
 
             // Handle different response types
-            if (a2aResponse is AgentMessage message)
+            if (a2aResponse.PayloadCase == SendMessageResponseCase.Message)
             {
+                var message = a2aResponse.Message!;
                 var responseMessage = message.ToChatMessage();
                 if (responseMessage is { Contents.Count: > 0 })
                 {
@@ -67,9 +68,10 @@ public override async IAsyncEnumerable<AgentResponseUpdate> RunStreamingAsync(
                     });
                 }
             }
-            else if (a2aResponse is AgentTask agentTask)
+            else if (a2aResponse.PayloadCase == SendMessageResponseCase.Task)
             {
                 // Manually convert AgentTask artifacts to ChatMessages since the extension method is internal
+                var agentTask = a2aResponse.Task!;
                 if (agentTask.Artifacts is not null)
                 {
                     foreach (var artifact in agentTask.Artifacts)