WPF Chat Orchestrator Generator

If `$0` is empty, use the AskUserQuestion tool to ask: "Enter the orchestrator class name (e.g., ChatOrchestrator)". Do NOT proceed until a valid name is provided. Use the response as the orchestrator name for all subsequent steps.

Generate $0: a streaming chat orchestrator that decomposes IChatClient.GetStreamingResponseAsync into a stream of UI-agnostic ChatEvents, plus the MCP tool acquisition (McpClient.CreateAsync + StdioClientTransport) that feeds ChatOptions.Tools.

• Replace {Namespace} with the project's root namespace.
• The IChatClient is produced by /wpf-dev-pack:make-wpf-chatclient-factory

(already wrapped with UseFunctionInvocation, so the tool loop runs automatically).

Full rationale in two knowledge topics (fetch via WpfDevPackMcp get_wpf_topic): hosting-extensions-ai-chatclient-in-wpf-mvvm (Dispatcher marshaling, the yield-illegal-in-catch (CS1631) restructuring, cancellation) and consuming-mcp-tools-in-extensions-ai (there is no McpClientFactory; McpClient is abstract — use the static CreateAsync; off-Dispatcher exit dispose).

⚠️ Verify signatures with HandMirror first

Microsoft.Extensions.AI and the MCP SDK evolve quickly. Before emitting, verify with HandMirror (inspect_nuget_package / inspect_nuget_package_type): Microsoft.Extensions.AI (IChatClient, ChatResponseUpdate, ChatOptions, FunctionCallContent, FunctionResultContent) and ModelContextProtocol (McpClient.CreateAsync, StdioClientTransport, McpClientTool).

Required Packages

<PackageReference Include="Microsoft.Extensions.AI" Version="10.*" />
<PackageReference Include="ModelContextProtocol" Version="1.*" />

ModelContextProtocol 1.x ships the client types (McpClient, StdioClientTransport, McpClientTool) in its ModelContextProtocol.Core dependency — the package reference above still works (Core flows transitively) and the ModelContextProtocol.Client namespace is unchanged.

Usings: the snippets assume these in the target project's GlobalUsings.cs: global using System.Runtime.CompilerServices; ([EnumeratorCancellation]), global using Microsoft.Extensions.AI;, global using ModelContextProtocol.Client;, and global using Microsoft.Extensions.Logging; (ILoggerFactory). ChatSettings is the supporting type emitted by /wpf-dev-pack:make-wpf-chatclient-factory.

Placement: standalone default is {Project}/Services below. In a make-wpf-project solution, prefer the *.ViewModels project (namespace {Namespace}.ViewModels) — every type here is WPF-free, and that placement lets ViewModels consume the orchestrator without referencing the app project (the layout used by the one-button /wpf-dev-pack:make-wpf-chatclient).

Generated Code

ChatEvent.cs (UI-agnostic stream events)

namespace {Namespace}.Services;

public abstract record ChatEvent;
public sealed record ChatText(string Text) : ChatEvent;
public sealed record ToolStarted(string Name, IDictionary<string, object?>? Arguments) : ChatEvent;
public sealed record ToolCompleted(string CallId, object? Result) : ChatEvent;
public sealed record ChatFailed(Exception Error) : ChatEvent;

$0.cs (stream decomposition)

C# forbids yield inside a catch (CS1631). So the loop catches a fault into a flag and yields the failure event after the try/catch closes. A OperationCanceledException is a normal stop (yield break), not a failure.

namespace {Namespace}.Services;

public sealed class $0(IChatClient client, IList<AITool> tools, ChatSettings settings)
{
    private readonly IChatClient _client = client;
    private readonly IList<AITool> _tools = tools;
    private readonly ChatSettings _settings = settings;

    public async IAsyncEnumerable<ChatEvent> SendAsync(
        IList<ChatMessage> history, [EnumeratorCancellation] CancellationToken ct)
    {
        var options = new ChatOptions { Tools = _tools, ModelId = _settings.ModelId };
        await using var e = _client.GetStreamingResponseAsync(history, options, ct).GetAsyncEnumerator(ct);

        while (true)
        {
            ChatResponseUpdate? update = null;
            bool faulted = false; Exception? error = null;
            try
            {
                if (!await e.MoveNextAsync()) { break; }
                update = e.Current;
            }
            catch (OperationCanceledException) { yield break; }
            catch (Exception ex) { faulted = true; error = ex; }   // CS1631: cannot yield here

            if (faulted) { yield return new ChatFailed(error!); yield break; }

            if (!string.IsNullOrEmpty(update!.Text)) { yield return new ChatText(update.Text); }
            foreach (AIContent c in update.Contents)
            {
                if (c is FunctionCallContent call)  { yield return new ToolStarted(call.Name, call.Arguments); }
                if (c is FunctionResultContent res) { yield return new ToolCompleted(res.CallId, res.Result); }
            }
        }
    }
}

Emit text via update.Text (robust across stream/SDK shapes) rather than walking TextContent.

McpToolService.cs (tool acquisition + stdio lifecycle)

There is no McpClientFactory. McpClient is abstract — use the static CreateAsync. Connect once and cache (re-connecting per send re-spawns the child process); dispose off the Dispatcher on app exit.

namespace {Namespace}.Services;

public sealed class McpToolService : IAsyncDisposable
{
    private McpClient? _mcp;
    public IList<McpClientTool> Tools { get; private set; } = [];

    // For a framework-dependent dll: Command="dotnet", Arguments=[dllPath].
    // For a self-contained exe: Command=exePath.
    public async Task ConnectAsync(string serverCommand, IList<string> serverArgs,
        ILoggerFactory? loggerFactory, CancellationToken ct)
    {
        var transport = new StdioClientTransport(new StdioClientTransportOptions
        {
            Name = "tools",
            Command = serverCommand,
            Arguments = serverArgs,
        }, loggerFactory);

        // NOTE: there is NO McpClientFactory. McpClient is abstract — use the static CreateAsync.
        _mcp = await McpClient.CreateAsync(transport, clientOptions: null, loggerFactory: null, ct);
        Tools = await _mcp.ListToolsAsync(cancellationToken: ct); // McpClientTool : AIFunction
    }

    public async ValueTask DisposeAsync()
    {
        if (_mcp is not null) { await _mcp.DisposeAsync(); }
    }
}

McpClientTool : AIFunction, so the acquired tools drop straight into the orchestrator's IList<AITool>:

var options = new ChatOptions { Tools = [.. mcpToolService.Tools], ModelId = modelId };

App exit — dispose the stdio client OFF the Dispatcher

Disposing the stdio client ends its child process. From App.OnExit (UI thread) you must not block sync-over-async, which deadlocks the Dispatcher:

// App.OnExit — bounded, OFF the Dispatcher; never .GetAwaiter().GetResult()/.Wait() on the UI thread.
Task.Run(async () => await _mcpService.DisposeAsync()).Wait(TimeSpan.FromSeconds(3));

How the ViewModel consumes it (Dispatcher marshaling + cancellation)

Async stream continuations are not Dispatcher-affine — marshal each event onto the UI Dispatcher before touching bound state, gate Send with a re-entrancy guard, and treat OperationCanceledException as a normal stop:

private CancellationTokenSource? _cts;
public bool IsStreaming { get; private set; }

private async Task SendAsync()
{
    if (IsStreaming || string.IsNullOrWhiteSpace(Input)) { return; } // re-entrancy + empty guard
    IsStreaming = true;
    _cts = new CancellationTokenSource();
    RaiseCommandStates(); // Send disabled, Stop enabled
    try
    {
        await foreach (ChatEvent ev in _orchestrator.SendAsync(_history, _cts.Token))
        {
            Application.Current.Dispatcher.Invoke(() => Apply(ev)); // marshal before touching bound state
        }
    }
    catch (OperationCanceledException) { /* user pressed Stop — normal, not an error */ }
    finally
    {
        IsStreaming = false;
        _cts.Dispose(); _cts = null;
        RaiseCommandStates();
    }
}

private void Stop() => _cts?.Cancel();
// SendCommand.CanExecute => !IsStreaming && !string.IsNullOrWhiteSpace(Input)
// StopCommand.CanExecute => IsStreaming

The full ViewModel (turns collection, IsWaiting, Apply(ev) switch) is emitted by the one-button /wpf-dev-pack:make-wpf-chatclient. If the ViewModel lives in a WPF-free *.ViewModels project, do NOT call Application.Current.Dispatcher there (P-002) — inject the one-method IUiDispatcher abstraction from make-wpf-chatclient instead.

File Location

{Project}/
└── Services/
    ├── ChatEvent.cs
    ├── $0.cs
    └── McpToolService.cs

Related

• Knowledge (fetch via WpfDevPackMcp get_wpf_topic): hosting-extensions-ai-chatclient-in-wpf-mvvm,

consuming-mcp-tools-in-extensions-ai, threading-wpf-dispatcher, preventing-dispatcher-deadlock.

• Sibling scaffolders: consumes the IChatClient from

/wpf-dev-pack:make-wpf-chatclient-factory. Emitted as part of the one-button /wpf-dev-pack:make-wpf-chatclient.