.NET: [Breaking] Migrate A2A agent and hosting to A2A SDK v1 (#5423)

* update a2a agent to the latest a2a sdk (#5257) * Move A2A samples from 04-hosting to 02-agents (#5267) Move the A2A sample projects (A2AAgent_AsFunctionTools and A2AAgent_PollingForTaskCompletion) from samples/04-hosting/A2A/ to samples/02-agents/A2A/ to better align with the sample directory structure. Update solution file and samples README accordingly. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * .NET: Fix stream reconnection for A2AAgent (#5275) * Add SSE stream reconnection support to A2AAgent Implement automatic reconnection for SSE streams that disconnect mid-task, using the Last-Event-ID header to resume from where the stream left off. Changes: - Add InvokeStreamingWithReconnectAsync method to A2AAgent with configurable max retries and delay between attempts - Add new log messages for reconnection events - Add A2AAgent_StreamReconnection sample demonstrating the feature - Update existing polling sample to use simplified SendMessageAsync API - Add unit tests for stream reconnection logic Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * address comments * Address PR review feedback - Dispose SSE enumerator before GetTaskAsync fallback to release HTTP connection - Wrap StreamWriter in using blocks with leaveOpen:true and explicit UTF-8 encoding - Print update.Text instead of update object in stream reconnection sample Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * .NET: Use IA2AClientFactory to create A2AClient (#5277) * Refactor A2A extensions to use IA2AClientFactory and add ProtocolSelection sample - Update A2AAgentCardExtensions to accept IA2AClientFactory instead of A2AClientOptions - Update A2ACardResolverExtensions to accept IA2AClientFactory - Update A2AClientExtensions to accept IA2AClientFactory - Update A2AAgent to use IA2AClientFactory for client creation - Add A2AAgent_ProtocolSelection sample demonstrating protocol selection - Add comprehensive unit tests for all changes - Update README files with new sample reference Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * Reorder params: options before loggerFactory in A2A extensions Move A2AClientOptions parameter before ILoggerFactory in AsAIAgent and GetAIAgentAsync extension methods to follow the repo convention of keeping LoggerFactory and CancellationToken as the last parameters. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * .NET: Migrate A2A hosting to A2A SDK v1 (#5363) * .NET: Migrate A2A hosting to A2A SDK v1 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * remove unused agent card --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * .NET: Split A2A endpoint mapping into protocol-specific methods (#5413) * .NET: Refactor A2A hosting registration into A2AServerServiceCollectionExtensions - Rename A2AHostingOptions to A2AServerRegistrationOptions - Move server registration logic from A2AEndpointRouteBuilderExtensions and AIAgentExtensions into new A2AServerServiceCollectionExtensions - Remove A2AProtocolBinding and AIAgentExtensions (consolidated) - Update samples and tests to use the new registration API Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * address copilot comments --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * Remove unnecessary using directive in AgentWebChat.AgentHost Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> * restore AsyncEnumerable package version * address copilot initial feedback * address automated code review and formatting issues * fix formatting issues * Add DI wiring verification tests for AddA2AServer Add three tests to A2AServerServiceCollectionExtensionsTests that verify custom keyed services are actually wired through to the A2AServer, not just that the server resolves non-null: - Custom IAgentHandler: verifies the keyed handler is invoked when processing a SendMessageRequest instead of the default A2AAgentHandler. - Custom AgentSessionStore (no handler): verifies the keyed session store's GetSessionAsync is called during request processing when no custom handler is registered. - Default stores end-to-end: verifies the InMemoryAgentSessionStore and InMemoryTaskStore defaults successfully process a request. Uses a new CreateAgentMockForRequests helper that includes SerializeSessionCoreAsync setup needed by InMemoryAgentSessionStore. All tests call A2AServer.SendMessageAsync directly (no HTTP layer needed) and use CancellationToken timeouts to guard against hangs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2026-06-16 21:04:09 +08:00 · 2026-04-23 07:53:00 +00:00
parent acec9caa2f
commit 66e02c10e3
58 changed files with 4201 additions and 2594 deletions
@@ -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>
@@ -18,8 +18,12 @@ AIAgent agent = agentCard.AsAIAgent();

 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)
@@ -0,0 +1,19 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="A2A" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.A2A\Microsoft.Agents.AI.A2A.csproj" />
+  </ItemGroup>
+
+</Project>
@@ -0,0 +1,36 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+// This sample demonstrates how to select the A2A protocol binding (HTTP+JSON vs JSON-RPC) when
+// creating an AIAgent from an A2A agent card using A2AClientOptions.PreferredBindings.
+
+using A2A;
+using Microsoft.Agents.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();
+
+// Use A2AClientOptions to explicitly select the HTTP+JSON protocol binding.
+// This tells the A2A client factory to prefer the HTTP+JSON interface when the agent card
+// advertises multiple supported interfaces.
+A2AClientOptions options = new()
+{
+    PreferredBindings = [ProtocolBindingNames.HttpJson]
+};
+
+// To prefer JSON-RPC instead, use:
+// A2AClientOptions options = new()
+// {
+//     PreferredBindings = [ProtocolBindingNames.JsonRpc]
+// };
+
+// Create an instance of the AIAgent for an existing A2A agent, using the specified protocol binding.
+AIAgent agent = agentCard.AsAIAgent(options: options);
+
+// Invoke the agent and output the text result.
+AgentResponse response = await agent.RunAsync("Tell me a joke about a pirate.");
+Console.WriteLine(response);
@@ -0,0 +1,27 @@
+# A2A Agent Protocol Selection
+
+This sample demonstrates how to select the A2A protocol binding when creating an `AIAgent` from an A2A agent card.
+
+A2A agents can expose multiple interfaces with different protocol bindings (e.g., HTTP+JSON, JSON-RPC). By default, `AsAIAgent()` prefers HTTP+JSON with JSON-RPC as a fallback. This sample shows how to use `A2AClientOptions.PreferredBindings` to explicitly control which protocol binding is used.
+
+The sample:
+
+- Connects to an A2A agent server specified in the `A2A_AGENT_HOST` environment variable
+- Configures `A2AClientOptions` to prefer the HTTP+JSON protocol binding
+- Creates an `AIAgent` from the resolved agent card using the specified binding
+- Sends a message to the agent and displays the response
+
+## 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
+
+**Note**: These samples need to be run against a valid A2A server. If no A2A server is available, they can be run against the echo-agent that can be spun up locally by following the guidelines at: https://github.com/a2aproject/a2a-dotnet/blob/main/samples/AgentServer/README.md
+
+Set the following environment variable:
+
+```powershell
+$env:A2A_AGENT_HOST="http://localhost:5000"  # Replace with your A2A agent server host
+```
@@ -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>
@@ -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 run.
+// 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.Text);
+        }
+    }
+}
@@ -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
+```
@@ -3,7 +3,7 @@
 These samples demonstrate how to work with Agent-to-Agent (A2A) specific features in the Agent Framework.

 For other samples that demonstrate how to use AIAgent instances,
-see the [Getting Started With Agents](../../02-agents/Agents/README.md) samples.
+see the [Getting Started With Agents](../Agents/README.md) samples.

 ## Prerequisites

@@ -15,6 +15,8 @@ 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.|
+|[A2A Agent Protocol Selection](./A2AAgent_ProtocolSelection/)|This sample demonstrates how to select the A2A protocol binding (HTTP+JSON vs JSON-RPC) when creating an AIAgent from an A2A agent card using A2AClientOptions.|

 ## Running the samples from the console

@@ -19,3 +19,4 @@ The getting started samples demonstrate the fundamental concepts and functionali
 | [Declarative Agents](./DeclarativeAgents) | Loading and executing AI agents from YAML configuration files |
 | [AG-UI](./AGUI/README.md) | Getting started with AG-UI (Agent UI Protocol) servers and clients |
 | [Dev UI](./DevUI/README.md) | Interactive web interface for testing and debugging AI agents during development |
+| [A2A Agents](./A2A/README.md) | Working with Agent-to-Agent (A2A) specific features |
@@ -62,12 +62,10 @@ public static class Program
                }

                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)
@@ -14,7 +14,7 @@ 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
@@ -26,16 +26,16 @@ 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)
@@ -43,9 +43,9 @@ 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}"),
        };

@@ -53,7 +53,7 @@ internal static class HostAgentFactory
    }

    #region private
-    private static AgentCard GetInvoiceAgentCard()
+    private static AgentCard GetInvoiceAgentCard(string[] agentUrls)
    {
        var capabilities = new AgentCapabilities()
        {
@@ -82,10 +82,11 @@ internal static class HostAgentFactory
            DefaultOutputModes = ["text"],
            Capabilities = capabilities,
            Skills = [invoiceQuery],
+            SupportedInterfaces = CreateAgentInterfaces(agentUrls)
        };
    }

-    private static AgentCard GetPolicyAgentCard()
+    private static AgentCard GetPolicyAgentCard(string[] agentUrls)
    {
        var capabilities = new AgentCapabilities()
        {
@@ -114,10 +115,11 @@ internal static class HostAgentFactory
            DefaultOutputModes = ["text"],
            Capabilities = capabilities,
            Skills = [policyQuery],
+            SupportedInterfaces = CreateAgentInterfaces(agentUrls)
        };
    }

-    private static AgentCard GetLogisticsAgentCard()
+    private static AgentCard GetLogisticsAgentCard(string[] agentUrls)
    {
        var capabilities = new AgentCapabilities()
        {
@@ -146,7 +148,29 @@ internal static class HostAgentFactory
            DefaultOutputModes = ["text"],
            Capabilities = capabilities,
            Skills = [logisticsQuery],
+            SupportedInterfaces = CreateAgentInterfaces(agentUrls)
        };
    }
+
+    private static List<AgentInterface> CreateAgentInterfaces(string[] agentUrls)
+    {
+        List<AgentInterface> agentInterfaces = [];
+
+        agentInterfaces.AddRange(agentUrls.Select(url => new AgentInterface
+        {
+            Url = url,
+            ProtocolBinding = ProtocolBindingNames.JsonRpc,
+            ProtocolVersion = "1.0",
+        }));
+
+        agentInterfaces.AddRange(agentUrls.Select(url => new AgentInterface
+        {
+            Url = url,
+            ProtocolBinding = ProtocolBindingNames.HttpJson,
+            ProtocolVersion = "1.0",
+        }));
+
+        return agentInterfaces;
+    }
    #endregion
 }
@@ -25,10 +25,6 @@ for (var i = 0; i < args.Length; i++)

 var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddHttpClient().AddLogging();
-var app = builder.Build();
-
-var httpClient = app.Services.GetRequiredService<IHttpClientFactory>().CreateClient();
-var logger = app.Logger;

 IConfigurationRoot configuration = new ConfigurationBuilder()
    .AddEnvironmentVariables()
@@ -38,14 +34,15 @@ IConfigurationRoot configuration = new ConfigurationBuilder()
 string? apiKey = configuration["OPENAI_API_KEY"];
 string model = configuration["OPENAI_CHAT_MODEL_NAME"] ?? "gpt-5.4-mini";
 string? endpoint = configuration["AZURE_AI_PROJECT_ENDPOINT"];
+string[] agentUrls = (builder.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 +51,9 @@ if (!string.IsNullOrEmpty(endpoint) && !string.IsNullOrEmpty(agentName))
 {
    (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($"Unsupported agent type: {agentType}"),
    };
 }
@@ -68,7 +65,7 @@ else if (!string.IsNullOrEmpty(apiKey))
            agentType, model, apiKey, "InvoiceAgent",
            """
            You specialize in handling queries related to invoices.
-            """, tools),
+            """, agentUrls, tools),
        "POLICY" => await HostAgentFactory.CreateChatCompletionHostAgentAsync(
            agentType, model, apiKey, "PolicyAgent",
            """
@@ -84,7 +81,7 @@ else if (!string.IsNullOrEmpty(apiKey))
            resolution in SAP CRM and notify the customer via email within 2 business days, referencing the
            original invoice and the credit memo number. Use the 'Formal Credit Notification' email
            template."
-            """),
+            """, agentUrls),
        "LOGISTICS" => await HostAgentFactory.CreateChatCompletionHostAgentAsync(
            agentType, model, apiKey, "LogisticsAgent",
            """
@@ -95,7 +92,7 @@ else if (!string.IsNullOrEmpty(apiKey))
            Shipment number: SHPMT-SAP-001
            Item: TSHIRT-RED-L
            Quantity: 900
-            """),
+            """, agentUrls),
        _ => throw new ArgumentException($"Unsupported agent type: {agentType}"),
    };
 }
@@ -104,10 +101,12 @@ else
    throw new ArgumentException("Either A2AServer:ApiKey or A2AServer:ConnectionString & agentName must be provided");
 }

-var a2aTaskManager = app.MapA2A(
-    hostA2AAgent,
-    path: "/",
-    agentCard: hostA2AAgentCard,
-    taskManager => app.MapWellKnownAgentCard(taskManager, "/"));
+builder.AddA2AServer(hostA2AAgent);
+
+var app = builder.Build();
+app.MapA2AHttpJson(hostA2AAgent, "/");
+app.MapA2AJsonRpc(hostA2AAgent, "/");
+
+app.MapWellKnownAgentCard(hostA2AAgentCard);

 await app.RunAsync();
@@ -1,6 +1,5 @@
 // Copyright (c) Microsoft. All rights reserved.

-using A2A.AspNetCore;
 using AgentWebChat.AgentHost;
 using AgentWebChat.AgentHost.Custom;
 using AgentWebChat.AgentHost.Utilities;
@@ -146,6 +145,9 @@ builder.Services.AddKeyedSingleton<AIAgent>("my-di-matchingname-agent", (sp, nam
        instructions: "you are a dependency inject agent. Tell me all about dependency injection.");
 });

+pirateAgentBuilder.AddA2AServer();
+knightsKnavesAgentBuilder.AddA2AServer();
+
 var app = builder.Build();

 app.MapOpenApi();
@@ -154,17 +156,9 @@ app.UseSwaggerUI(options => options.SwaggerEndpoint("/openapi/v1.json", "Agents
 // Configure the HTTP request pipeline.
 app.UseExceptionHandler();

-// attach a2a with simple message communication
-app.MapA2A(pirateAgentBuilder, path: "/a2a/pirate");
-app.MapA2A(knightsKnavesAgentBuilder, path: "/a2a/knights-and-knaves", agentCard: new()
-{
-    Name = "Knights and Knaves",
-    Description = "An agent that helps you solve the knights and knaves puzzle.",
-    Version = "1.0",
-
-    // Url can be not set, and SDK will help assign it.
-    // Url = "http://localhost:5390/a2a/knights-and-knaves"
-});
+// Expose A2A servers over HTTP with JSON payloads
+app.MapA2AHttpJson(pirateAgentBuilder, path: "/a2a/pirate");
+app.MapA2AHttpJson(knightsKnavesAgentBuilder, path: "/a2a/knights-and-knaves");

 app.MapDevUI();

@@ -43,20 +43,21 @@ internal sealed class A2AAgentClient : AgentClientBase
        {
            // 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 @@ internal sealed class A2AAgentClient : AgentClientBase
                    });
                }
            }
-            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)
@@ -16,7 +16,7 @@ were local agents. These are supported using various `AIAgent` subclasses.
 | [`01-get-started/`](./01-get-started/) | Progressive tutorial: hello agent → hosting |
 | [`02-agents/`](./02-agents/) | Deep-dive by concept: tools, middleware, providers, orchestrations |
 | [`03-workflows/`](./03-workflows/) | Workflow patterns: sequential, concurrent, state, declarative |
-| [`04-hosting/`](./04-hosting/) | Deployment: Azure Functions, Durable Tasks, A2A |
+| [`04-hosting/`](./04-hosting/) | Deployment: Azure Functions, Durable Tasks |
 | [`05-end-to-end/`](./05-end-to-end/) | Full applications, evaluation, demos |

 ## Getting Started