chore: import upstream snapshot with attribution

dotnet/samples/05-end-to-end/A2AClientServer/A2AClient/A2AClient.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFrameworks>net10.0</TargetFrameworks>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <UserSecretsId>5ee045b0-aea3-4f08-8d31-32d1a6f8fed0</UserSecretsId>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="A2A" />
+    <PackageReference Include="System.CommandLine" />
+    <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.Abstractions\Microsoft.Agents.AI.Abstractions.csproj" />
+    <ProjectReference Include="..\..\..\..\src\Microsoft.Agents.AI.OpenAI\Microsoft.Agents.AI.OpenAI.csproj" />
+  </ItemGroup>
+
+</Project>

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

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+// Copyright (c) Microsoft. All rights reserved.
+using System.ClientModel;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.AI;
+using Microsoft.Extensions.Logging;
+using OpenAI;
+using OpenAI.Chat;
+
+namespace A2A;
+
+internal sealed class HostClientAgent
+{
+    internal HostClientAgent(ILoggerFactory loggerFactory)
+    {
+        this._logger = loggerFactory.CreateLogger("HostClientAgent");
+    }
+
+    internal async Task InitializeAgentAsync(string modelId, string apiKey, string[] agentUrls)
+    {
+        try
+        {
+            this._logger.LogInformation("Initializing Agent Framework agent with model: {ModelId}", modelId);
+
+            // Connect to the remote agents via A2A
+            var createAgentTasks = agentUrls.Select(CreateAgentAsync);
+            var agents = await Task.WhenAll(createAgentTasks);
+            var tools = agents.Select(agent => (AITool)agent.AsAIFunction()).ToList();
+
+            // Create the agent that uses the remote agents as tools
+            this.Agent = new OpenAIClient(new ApiKeyCredential(apiKey))
+             .GetChatClient(modelId)
+             .AsAIAgent(instructions: "You specialize in handling queries for users and using your tools to provide answers.", name: "HostClient", tools: tools);
+        }
+        catch (Exception ex)
+        {
+            this._logger.LogError(ex, "Failed to initialize HostClientAgent");
+            throw;
+        }
+    }
+
+    /// <summary>
+    /// The associated <see cref="Agent"/>
+    /// </summary>
+    public AIAgent? Agent { get; private set; }
+
+    #region private
+    private readonly ILogger _logger;
+
+    private static async Task<AIAgent> CreateAgentAsync(string agentUri)
+    {
+        var url = new Uri(agentUri);
+        var httpClient = new HttpClient
+        {
+            Timeout = TimeSpan.FromSeconds(60)
+        };
+
+        var agentCardResolver = new A2ACardResolver(url, httpClient);
+
+        return await agentCardResolver.GetAIAgentAsync();
+    }
+    #endregion
+}

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

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+// Copyright (c) Microsoft. All rights reserved.
+
+using System.CommandLine;
+using System.Reflection;
+using Microsoft.Agents.AI;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.Logging;
+
+namespace A2A;
+
+public static class Program
+{
+    public static async Task<int> Main(string[] args)
+    {
+        // Create root command with options
+        var rootCommand = new RootCommand("A2AClient");
+        rootCommand.SetAction((_, ct) => HandleCommandsAsync(ct));
+
+        // Run the command
+        return await rootCommand.Parse(args).InvokeAsync();
+    }
+
+    private static async Task HandleCommandsAsync(CancellationToken cancellationToken)
+    {
+        // Set up the logging
+        using var loggerFactory = LoggerFactory.Create(builder =>
+        {
+            builder.AddConsole();
+            builder.SetMinimumLevel(LogLevel.Information);
+        });
+        var logger = loggerFactory.CreateLogger("A2AClient");
+
+        // Retrieve configuration settings
+        IConfigurationRoot configRoot = new ConfigurationBuilder()
+            .AddEnvironmentVariables()
+            .AddUserSecrets(Assembly.GetExecutingAssembly())
+            .Build();
+        var apiKey = configRoot["A2AClient:ApiKey"] ?? throw new ArgumentException("A2AClient:ApiKey must be provided");
+        var modelId = configRoot["A2AClient:ModelId"] ?? "gpt-5.4-mini";
+        var agentUrls = configRoot["A2AClient:AgentUrls"] ?? "http://localhost:5000/;http://localhost:5001/;http://localhost:5002/";
+
+        // Create the Host agent
+        var hostAgent = new HostClientAgent(loggerFactory);
+        await hostAgent.InitializeAgentAsync(modelId, apiKey, agentUrls!.Split(";"));
+        AgentSession session = await hostAgent.Agent!.CreateSessionAsync(cancellationToken);
+        try
+        {
+            while (true)
+            {
+                // Get user message
+                Console.Write("\nUser (:q or quit to exit): ");
+                string? message = Console.ReadLine();
+                if (string.IsNullOrWhiteSpace(message))
+                {
+                    Console.WriteLine("Request cannot be empty.");
+                    continue;
+                }
+
+                if (message is ":q" or "quit")
+                {
+                    break;
+                }
+
+                var agentResponse = await hostAgent.Agent!.RunAsync(message, session, cancellationToken: cancellationToken);
+
+                Console.ForegroundColor = ConsoleColor.Cyan;
+                Console.WriteLine($"\nAgent: {agentResponse.Text}");
+                Console.ResetColor();
+            }
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "An error occurred while running the A2AClient");
+            return;
+        }
+    }
+}

dotnet/samples/05-end-to-end/A2AClientServer/A2AClient/README.md

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+
+# A2A Client Sample
+Show how to create an A2A Client with a command line interface which invokes agents using the A2A protocol.
+
+## Run the Sample
+
+To run the sample, follow these steps:
+
+1. Run the A2A client:
+    ```bash
+    cd A2AClient
+    dotnet run
+    ```  
+2. Enter your request e.g. "Show me all invoices for Contoso?"
+
+## Set Environment Variables
+
+The agent urls are provided as a ` ` delimited list of strings
+
+```powershell
+cd dotnet/samples/05-end-to-end/A2AClientServer/A2AClient
+
+$env:OPENAI_CHAT_MODEL_NAME="gpt-5.4-mini"
+$env:OPENAI_API_KEY="<Your OPENAI api key>"
+$env:AGENT_URLS="http://localhost:5000/policy;http://localhost:5000/invoice;http://localhost:5000/logistics"
+```