refactor: generalize sidecar workflow runner

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

ARCHITECTURE.md

@@ -141,13 +141,15 @@ Workflows describe how agents collaborate. The architecture supports:
 
 Their runtime semantics follow the Agent Framework orchestration model: sequential and group chat preserve a visible shared conversation, concurrent aggregates multiple independent responses into one turn, and handoff turns can end once the active agent has responded and is waiting for the next user input.
 
-For Copilot-backed agents, Aryx uses a repo-local adapter around the Copilot SDK session layer so workflow agent routes still behave like Agent Framework handoffs. This is necessary because the upstream `GitHubCopilotAgent` does not currently project run-time handoff tool declarations into Copilot sessions or surface Copilot tool requests back as `FunctionCallContent` for the workflow runtime.
+For Copilot-backed agents, Aryx uses a repo-local provider module around the Copilot SDK session layer so workflow agent routes still behave like Agent Framework handoffs. This is necessary because the upstream `GitHubCopilotAgent` does not currently project run-time handoff tool declarations into Copilot sessions or surface Copilot tool requests back as `FunctionCallContent` for the workflow runtime.
+
+The sidecar now keeps that Copilot-specific behavior behind provider seams. Core execution uses shared `IAgentProvider`, `IProviderTurnSupport`, `ProviderSessionEvent`, `ProviderAgentBundle`, `TurnExecutionState`, and `AgentWorkflowTurnRunner` abstractions, while `Services/Providers/Copilot/` owns SDK-specific bundle creation, transcript projection, approvals, user input, MCP OAuth, exit-plan-mode handling, CLI/session management, and event adaptation.
 
 Workflows are shared application data, not renderer-only configuration. The same workflow definition now drives validation, persistence, session execution, and sidecar orchestration.
 
 Each workflow persists an explicit graph-backed topology. Agent nodes carry stable ids, ordering, and layout metadata, while start/end, fan-out/fan-in, sub-workflow, function, and request-port nodes make execution structure visible in the saved contract.
 
-That graph remains the execution contract for the sidecar, but orchestration mode is now a first-class backend concept. Graph-based modes (`single`, `sequential`, `concurrent`) still execute directly from saved edges. Builder-based modes (`handoff`, `group-chat`) additionally persist mode-specific `settings.modeSettings` data for handoff filtering, triage selection, return behavior, and group-chat round limits, and the sidecar translates those settings into specialized Agent Framework workflow builders at run time.
+That graph remains the execution contract for the sidecar, but orchestration mode is now a first-class backend concept. Graph-based modes (`single`, `sequential`, `concurrent`) still execute directly from saved edges. Builder-based modes (`handoff`, `group-chat`) additionally persist mode-specific `settings.modeSettings` data for handoff filtering, triage selection, return behavior, and group-chat round limits, and the sidecar translates those settings into specialized Agent Framework workflow builders at run time through shared orchestration helpers rather than Copilot-specific workflow code.
 
 Workflow templates remain a first-class shared-domain contract. The shared layer owns workflow definitions, workflow template definitions, and workflow import/export helpers (YAML import/export plus Mermaid and DOT export). Built-in workflows seed workspace state directly, while built-in and custom templates let the main process create additional saved workflows without expanding the sidecar protocol.
 
@@ -214,7 +216,7 @@ This is a structured stdio protocol used for:
 - streaming partial output
 - streaming agent activity
 
-This protocol boundary keeps the AI execution runtime replaceable and prevents the Electron main process from becoming overloaded with workflow-specific behavior.
+This protocol boundary keeps the AI execution runtime replaceable and prevents the Electron main process from becoming overloaded with workflow-specific behavior. On the sidecar side, raw provider events are first normalized into sidecar-owned provider event records before they become streamed run activity, so future providers can plug into the same transport without reshaping the main-process contract.
 
 The protocol also carries **turn-scoped lifecycle events** alongside output deltas. These events let the UI visualize execution internals without the main process having to interpret AI workflow semantics:
 

sidecar/src/Aryx.AgentHost/Services/AgentHostOptionsFactory.cs

@@ -0,0 +1,19 @@
+using Microsoft.Agents.AI.Workflows;
+
+namespace Aryx.AgentHost.Services;
+
+internal static class AgentHostOptionsFactory
+{
+    public static AIAgentHostOptions CreateDefault()
+    {
+        return new AIAgentHostOptions
+        {
+            EmitAgentUpdateEvents = null,
+            EmitAgentResponseEvents = false,
+            InterceptUserInputRequests = false,
+            InterceptUnterminatedFunctionCalls = false,
+            ReassignOtherAgentsAsUsers = true,
+            ForwardIncomingMessages = true,
+        };
+    }
+}

sidecar/src/Aryx.AgentHost/Services/AgentWorkflowTurnRunner.cs

@@ -0,0 +1,763 @@
+using System.IO;
+using System.Linq;
+using System.Globalization;
+using System.Text.Json;
+using Aryx.AgentHost.Contracts;
+using GitHub.Copilot.SDK;
+using Microsoft.Agents.AI;
+using Microsoft.Agents.AI.Workflows;
+using Microsoft.Agents.AI.Workflows.Checkpointing;
+using Microsoft.Agents.AI.Workflows.InProc;
+using Microsoft.Extensions.AI;
+
+namespace Aryx.AgentHost.Services;
+
+public class AgentWorkflowTurnRunner : ITurnWorkflowRunner
+{
+    private const string HandoffFunctionPrefix = "handoff_to_";
+    private readonly WorkflowValidator _workflowValidator;
+    private readonly WorkflowRunner _workflowRunner = new();
+    private readonly IProviderTurnSupport _providerTurnSupport;
+
+    internal AgentWorkflowTurnRunner(
+        IProviderTurnSupport providerTurnSupport,
+        WorkflowValidator? workflowValidator = null)
+    {
+        _providerTurnSupport = providerTurnSupport ?? throw new ArgumentNullException(nameof(providerTurnSupport));
+        _workflowValidator = workflowValidator ?? new WorkflowValidator();
+    }
+
+    public async Task<IReadOnlyList<ChatMessageDto>> RunTurnAsync(
+        RunTurnCommandDto command,
+        Func<TurnDeltaEventDto, Task> onDelta,
+        Func<SidecarEventDto, Task> onEvent,
+        Func<ApprovalRequestedEventDto, Task> onApproval,
+        Func<UserInputRequestedEventDto, Task> onUserInput,
+        Func<McpOauthRequiredEventDto, Task> onMcpOAuthRequired,
+        Func<ExitPlanModeRequestedEventDto, Task> onExitPlanMode,
+        CancellationToken cancellationToken)
+    {
+        string? validationError = _workflowValidator.Validate(command.Workflow, command.WorkflowLibrary)
+            .FirstOrDefault()?.Message;
+        if (validationError is not null)
+        {
+            throw new InvalidOperationException(validationError);
+        }
+
+        TurnExecutionState state = new(command);
+        using CancellationTokenSource runCancellation =
+            CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
+        IProviderTranscriptProjector? transcriptProjector = null;
+
+        try
+        {
+            await using ProviderAgentBundle bundle = await _providerTurnSupport.CreateAgentBundleAsync(
+                    command,
+                    state,
+                    onEvent,
+                    onApproval,
+                    onUserInput,
+                    runCancellation,
+                    runCancellation.Token)
+                .ConfigureAwait(false);
+            transcriptProjector = bundle.TranscriptProjector;
+            ConfigureHookLifecycleEventSuppression(state, bundle);
+            Workflow workflow = BuildWorkflowForCommand(command, bundle.Agents, _workflowRunner);
+            List<ChatMessage> inputMessages = command.Messages.Select(transcriptProjector.ToChatMessage).ToList();
+            transcriptProjector.AttachMessageMode(inputMessages, command.MessageMode);
+
+            using FileSystemJsonCheckpointStore? checkpointStore = CreateCheckpointStore(command);
+            CheckpointManager? checkpointManager = checkpointStore is not null
+                ? CheckpointManager.CreateJson(checkpointStore)
+                : null;
+
+            await using StreamingRun run = await OpenWorkflowRunAsync(
+                command,
+                workflow,
+                inputMessages,
+                checkpointManager).ConfigureAwait(false);
+            await run.TrySendMessageAsync(new TurnToken(emitEvents: true)).ConfigureAwait(false);
+
+            await foreach (WorkflowEvent evt in run.WatchStreamAsync(runCancellation.Token).ConfigureAwait(false))
+            {
+                if (evt is RequestInfoEvent requestInfo
+                    && await TryHandleRequestPortRequestAsync(
+                        command,
+                        requestInfo,
+                        run,
+                        onUserInput,
+                        runCancellation.Token).ConfigureAwait(false))
+                {
+                    continue;
+                }
+
+                bool shouldEndTurn = await HandleWorkflowEventAsync(
+                        command,
+                        evt,
+                        inputMessages,
+                        state,
+                        transcriptProjector,
+                        onDelta,
+                        onEvent)
+                    .ConfigureAwait(false);
+                await EmitPendingEventsAsync(state, onEvent).ConfigureAwait(false);
+                await EmitPendingMcpOauthRequestsAsync(state, onMcpOAuthRequired).ConfigureAwait(false);
+                if (shouldEndTurn)
+                {
+                    break;
+                }
+            }
+
+            await EmitPendingEventsAsync(state, onEvent).ConfigureAwait(false);
+            await EmitPendingMcpOauthRequestsAsync(state, onMcpOAuthRequired).ConfigureAwait(false);
+            return state.FinalizeCompletedMessages(transcriptProjector);
+        }
+        catch (OperationCanceledException) when (runCancellation.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
+        {
+            await EmitPendingEventsAsync(state, onEvent).ConfigureAwait(false);
+            await EmitPendingMcpOauthRequestsAsync(state, onMcpOAuthRequired).ConfigureAwait(false);
+            ExitPlanModeRequestedEventDto? exitPlanModeEvent =
+                _providerTurnSupport.ConsumePendingExitPlanModeRequest(command.RequestId);
+            if (exitPlanModeEvent is null || !state.HasPendingExitPlanModeRequest)
+            {
+                throw;
+            }
+
+            await onExitPlanMode(exitPlanModeEvent).ConfigureAwait(false);
+            return state.FinalizeCompletedMessages(
+                transcriptProjector ?? throw new InvalidOperationException("Provider transcript projector was not initialized."));
+        }
+        finally
+        {
+            _providerTurnSupport.ClearRequestState(command.RequestId);
+        }
+    }
+
+    internal static Workflow BuildWorkflowForCommand(
+        RunTurnCommandDto command,
+        IReadOnlyList<AIAgent> agents,
+        WorkflowRunner? workflowRunner = null)
+    {
+        ArgumentNullException.ThrowIfNull(command);
+        ArgumentNullException.ThrowIfNull(agents);
+
+        return NormalizeOrchestrationMode(command.Workflow.Settings.OrchestrationMode) switch
+        {
+            "handoff" => WorkflowOrchestrationFactory.CreateHandoffWorkflow(command.Workflow, agents),
+            "group-chat" => WorkflowOrchestrationFactory.CreateGroupChatWorkflow(command.Workflow, agents),
+            _ => (workflowRunner ?? new WorkflowRunner()).BuildWorkflow(command.Workflow, agents, command.WorkflowLibrary),
+        };
+    }
+
+    internal static FileSystemJsonCheckpointStore? CreateCheckpointStore(RunTurnCommandDto command)
+    {
+        if (!ShouldEnableWorkflowCheckpointing(command))
+        {
+            return null;
+        }
+
+        DirectoryInfo checkpointDirectory = new(GetCheckpointStorePath(command));
+        return new FileSystemJsonCheckpointStore(checkpointDirectory);
+    }
+
+    internal static bool ShouldEnableWorkflowCheckpointing(RunTurnCommandDto command)
+    {
+        ArgumentNullException.ThrowIfNull(command);
+        return command.Workflow.Settings.Checkpointing.Enabled;
+    }
+
+    internal static string GetCheckpointStorePath(RunTurnCommandDto command)
+    {
+        ArgumentNullException.ThrowIfNull(command);
+
+        if (!string.IsNullOrWhiteSpace(command.ResumeFromCheckpoint?.StorePath))
+        {
+            return command.ResumeFromCheckpoint.StorePath;
+        }
+
+        string localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
+        return Path.Combine(localAppData, "Aryx", "workflow-checkpoints", command.SessionId, command.RequestId);
+    }
+
+    private static string? NormalizeOrchestrationMode(string? value)
+    {
+        return string.IsNullOrWhiteSpace(value) ? null : value.Trim().ToLowerInvariant();
+    }
+
+    private static ValueTask<StreamingRun> OpenWorkflowRunAsync(
+        RunTurnCommandDto command,
+        Workflow workflow,
+        IReadOnlyList<ChatMessage> inputMessages,
+        CheckpointManager? checkpointManager)
+    {
+        InProcessExecutionEnvironment environment = CreateExecutionEnvironment(command, checkpointManager);
+        if (checkpointManager is not null && command.ResumeFromCheckpoint is { } resumeFromCheckpoint)
+        {
+            return environment.ResumeStreamingAsync(
+                workflow,
+                new CheckpointInfo(resumeFromCheckpoint.WorkflowSessionId, resumeFromCheckpoint.CheckpointId));
+        }
+
+        return environment.RunStreamingAsync(workflow, inputMessages.ToList(), command.RequestId);
+    }
+
+    internal static InProcessExecutionEnvironment CreateExecutionEnvironment(
+        RunTurnCommandDto command,
+        CheckpointManager? checkpointManager)
+    {
+        ArgumentNullException.ThrowIfNull(command);
+
+        string executionMode = command.Workflow.Settings.ExecutionMode?.Trim() ?? "off-thread";
+        InProcessExecutionEnvironment environment = string.Equals(
+            executionMode,
+            "lockstep",
+            StringComparison.OrdinalIgnoreCase)
+            ? InProcessExecution.Lockstep
+            : InProcessExecution.OffThread;
+
+        return checkpointManager is null ? environment : environment.WithCheckpointing(checkpointManager);
+    }
+
+    internal static void ConfigureHookLifecycleEventSuppression(
+        TurnExecutionState state,
+        ProviderAgentBundle bundle)
+    {
+        ArgumentNullException.ThrowIfNull(state);
+        ArgumentNullException.ThrowIfNull(bundle);
+
+        state.SuppressHookLifecycleEvents = !bundle.HasConfiguredHooks;
+    }
+
+    private static async Task EmitPendingEventsAsync(
+        TurnExecutionState state,
+        Func<SidecarEventDto, Task> onEvent)
+    {
+        foreach (SidecarEventDto pendingEvent in state.DrainPendingEvents())
+        {
+            await onEvent(pendingEvent).ConfigureAwait(false);
+        }
+    }
+
+    private static async Task EmitPendingMcpOauthRequestsAsync(
+        TurnExecutionState state,
+        Func<McpOauthRequiredEventDto, Task> onMcpOAuthRequired)
+    {
+        foreach (McpOauthRequiredEventDto request in state.DrainPendingMcpOauthRequests())
+        {
+            await onMcpOAuthRequired(request).ConfigureAwait(false);
+        }
+    }
+
+    public Task ResolveApprovalAsync(
+        ResolveApprovalCommandDto command,
+        CancellationToken cancellationToken)
+    {
+        return _providerTurnSupport.ResolveApprovalAsync(command, cancellationToken);
+    }
+
+    public Task ResolveUserInputAsync(
+        ResolveUserInputCommandDto command,
+        CancellationToken cancellationToken)
+    {
+        return _providerTurnSupport.ResolveUserInputAsync(command, cancellationToken);
+    }
+
+    private async Task<bool> TryHandleRequestPortRequestAsync(
+        RunTurnCommandDto command,
+        RequestInfoEvent requestInfo,
+        StreamingRun run,
+        Func<UserInputRequestedEventDto, Task> onUserInput,
+        CancellationToken cancellationToken)
+    {
+        if (!TryResolveRequestPortMetadata(command.Workflow, requestInfo, out WorkflowRequestPortMetadata? metadata))
+        {
+            return false;
+        }
+
+        UserInputRequest userInputRequest = CreateRequestPortUserInputRequest(metadata!, requestInfo);
+        UserInputResponse response = await _providerTurnSupport.RequestRequestPortUserInputAsync(
+            command,
+            userInputRequest,
+            onUserInput,
+            cancellationToken).ConfigureAwait(false);
+
+        object coercedResponse = CoerceRequestPortResponse(metadata!.ResponseType, response.Answer);
+        await run.SendResponseAsync(requestInfo.Request.CreateResponse(coercedResponse)).ConfigureAwait(false);
+        return true;
+    }
+
+    internal static async Task<bool> HandleWorkflowEventAsync(
+        RunTurnCommandDto command,
+        WorkflowEvent evt,
+        IReadOnlyList<ChatMessage> inputMessages,
+        TurnExecutionState state,
+        IProviderTranscriptProjector transcriptProjector,
+        Func<TurnDeltaEventDto, Task> onDelta,
+        Func<SidecarEventDto, Task> onEvent)
+    {
+        if (evt is ExecutorInvokedEvent invoked)
+        {
+            if (AgentIdentityResolver.TryResolveKnownAgentIdentity(
+                command.Workflow,
+                invoked.ExecutorId,
+                out AgentIdentity invokedAgent))
+            {
+                TraceHandoff(command, $"Executor invoked: {invoked.ExecutorId} -> {invokedAgent.AgentName} ({invokedAgent.AgentId}).");
+                await state.EmitThinkingIfNeeded(invokedAgent, onEvent).ConfigureAwait(false);
+            }
+            else
+            {
+                TraceHandoff(command, $"Executor invoked without a known agent match: {invoked.ExecutorId}.");
+            }
+
+            return false;
+        }
+
+        if (evt is RequestInfoEvent requestInfo)
+        {
+            AgentActivityEventDto? activity = WorkflowRequestInfoInterpreter.TryCreateActivityFromRequest(
+                command,
+                requestInfo,
+                state.ActiveAgent,
+                state.ToolNamesByCallId);
+
+            if (activity is null)
+            {
+                bool requiresBoundary = WorkflowRequestInfoInterpreter.RequiresUserInputTurnBoundary(command, requestInfo);
+                TraceHandoff(
+                    command,
+                    $"Request info produced no activity for data type '{requestInfo.Request.Data.TypeId}'. Requires boundary: {requiresBoundary}.");
+                return requiresBoundary;
+            }
+
+            await EmitActivityAsync(command, state, activity, onEvent).ConfigureAwait(false);
+            return false;
+        }
+
+        if (TryCreateWorkflowCheckpointSavedEvent(command, evt, out WorkflowCheckpointSavedEventDto? checkpointSaved))
+        {
+            await onEvent(checkpointSaved).ConfigureAwait(false);
+            return false;
+        }
+
+        if (TryCreateWorkflowDiagnosticEvent(command, evt, state, out WorkflowDiagnosticEventDto? diagnostic))
+        {
+            await onEvent(diagnostic).ConfigureAwait(false);
+            return false;
+        }
+
+        if (evt is AgentResponseUpdateEvent update)
+        {
+            await HandleAgentResponseUpdateAsync(command, update, state, onDelta, onEvent).ConfigureAwait(false);
+            return false;
+        }
+
+        if (evt is ExecutorCompletedEvent completed)
+        {
+            if (AgentIdentityResolver.TryResolveObservedAgentIdentity(
+                command.Workflow,
+                completed.ExecutorId,
+                state.ActiveAgent,
+                out AgentIdentity completedAgent))
+            {
+                TraceHandoff(command, $"Executor completed: {completed.ExecutorId} -> {completedAgent.AgentName} ({completedAgent.AgentId}).");
+                state.QueueCompletedActivity(completedAgent);
+                state.ClearActiveAgentIfMatching(completedAgent);
+            }
+            else
+            {
+                TraceHandoff(command, $"Executor completed without a known agent match: {completed.ExecutorId}.");
+            }
+
+            return false;
+        }
+
+        if (evt is WorkflowOutputEvent outputEvent)
+        {
+            List<ChatMessage> allMessages = outputEvent.As<List<ChatMessage>>() ?? [];
+            state.UpdateCompletedMessages(allMessages, inputMessages, transcriptProjector);
+        }
+
+        return false;
+    }
+
+    internal static UserInputRequest CreateRequestPortUserInputRequest(
+        WorkflowRequestPortMetadata metadata,
+        RequestInfoEvent requestInfo)
+    {
+        ArgumentNullException.ThrowIfNull(metadata);
+        ArgumentNullException.ThrowIfNull(requestInfo);
+
+        string question = metadata.Prompt
+            ?? BuildRequestPortFallbackQuestion(metadata, requestInfo);
+
+        bool expectsBoolean = IsBooleanResponseType(metadata.ResponseType);
+        return new UserInputRequest
+        {
+            Question = question,
+            Choices = expectsBoolean ? ["true", "false"] : null,
+            AllowFreeform = true,
+        };
+    }
+
+    internal static object CoerceRequestPortResponse(string responseType, string? answer)
+    {
+        string normalizedResponseType = responseType.Trim();
+        string trimmedAnswer = answer?.Trim() ?? string.Empty;
+
+        if (IsStringResponseType(normalizedResponseType))
+        {
+            return trimmedAnswer;
+        }
+
+        if (IsBooleanResponseType(normalizedResponseType))
+        {
+            return trimmedAnswer.ToLowerInvariant() switch
+            {
+                "true" or "t" or "yes" or "y" or "1" => true,
+                "false" or "f" or "no" or "n" or "0" => false,
+                _ => throw new InvalidOperationException(
+                    $"Request port response type \"{responseType}\" requires a boolean answer."),
+            };
+        }
+
+        if (IsNumericResponseType(normalizedResponseType))
+        {
+            if (double.TryParse(trimmedAnswer, NumberStyles.Float, CultureInfo.InvariantCulture, out double numeric))
+            {
+                return numeric;
+            }
+
+            throw new InvalidOperationException(
+                $"Request port response type \"{responseType}\" requires a numeric answer.");
+        }
+
+        if (IsJsonResponseType(normalizedResponseType))
+        {
+            try
+            {
+                return JsonDocument.Parse(trimmedAnswer).RootElement.Clone();
+            }
+            catch (JsonException ex)
+            {
+                throw new InvalidOperationException(
+                    $"Request port response type \"{responseType}\" requires a valid JSON answer.",
+                    ex);
+            }
+        }
+
+        return trimmedAnswer;
+    }
+
+    private static async Task HandleAgentResponseUpdateAsync(
+        RunTurnCommandDto command,
+        AgentResponseUpdateEvent update,
+        TurnExecutionState state,
+        Func<TurnDeltaEventDto, Task> onDelta,
+        Func<SidecarEventDto, Task> onEvent)
+    {
+        AgentIdentity? updateAgent = null;
+        string authorName = update.ExecutorId;
+        string[] handoffFunctionCalls = update.Update.Contents
+            .OfType<FunctionCallContent>()
+            .Select(content => content.Name)
+            .Where(IsHandoffFunctionName)
+            .Distinct(StringComparer.Ordinal)
+            .ToArray();
+        if (state.TryResolveObservedAgentForMessage(update.Update.MessageId, out AgentIdentity observedMessageAgent))
+        {
+            updateAgent = observedMessageAgent;
+            authorName = observedMessageAgent.AgentName;
+        }
+        else if (AgentIdentityResolver.TryResolveObservedAgentIdentity(
+            command.Workflow,
+            update.ExecutorId,
+            state.ActiveAgent,
+            out AgentIdentity resolvedUpdateAgent))
+        {
+            updateAgent = resolvedUpdateAgent;
+            authorName = resolvedUpdateAgent.AgentName;
+        }
+        else if (state.ActiveAgent is AgentIdentity activeAgent)
+        {
+            updateAgent = activeAgent;
+            authorName = activeAgent.AgentName;
+            TraceHandoff(
+                command,
+                $"Agent response update fell back to active agent {activeAgent.AgentName} ({activeAgent.AgentId}) for executor '{update.ExecutorId}' and message '{update.Update.MessageId ?? "<none>"}'.");
+        }
+
+        if (updateAgent.HasValue)
+        {
+            if (handoffFunctionCalls.Length > 0)
+            {
+                TraceHandoff(
+                    command,
+                    $"Agent response update from {updateAgent.Value.AgentName} ({updateAgent.Value.AgentId}) requested handoff via {string.Join(", ", handoffFunctionCalls)}.");
+            }
+
+            await state.EmitThinkingIfNeeded(updateAgent.Value, onEvent).ConfigureAwait(false);
+        }
+        else if (!string.IsNullOrEmpty(update.Update.Text) || handoffFunctionCalls.Length > 0)
+        {
+            TraceHandoff(
+                command,
+                $"Agent response update could not resolve agent for executor '{update.ExecutorId}' and message '{update.Update.MessageId ?? "<none>"}'.");
+        }
+
+        if (string.IsNullOrEmpty(update.Update.Text))
+        {
+            return;
+        }
+
+        string messageId = state.CreateMessageId(update.Update.MessageId);
+        (string _, string currentAuthorName, string currentContent) = state.AppendDelta(
+            messageId,
+            authorName,
+            update.Update.Text);
+
+        await onDelta(new TurnDeltaEventDto
+        {
+            Type = "turn-delta",
+            RequestId = command.RequestId,
+            SessionId = command.SessionId,
+            MessageId = messageId,
+            AuthorName = currentAuthorName,
+            ContentDelta = update.Update.Text,
+            Content = currentContent,
+        }).ConfigureAwait(false);
+    }
+
+    internal static async Task EmitActivityAsync(
+        RunTurnCommandDto command,
+        TurnExecutionState state,
+        AgentActivityEventDto activity,
+        Func<SidecarEventDto, Task> onEvent)
+    {
+        state.ApplyEvent(activity);
+        TraceHandoff(
+            command,
+            $"Activity emitted: {activity.ActivityType} -> {activity.AgentName ?? activity.AgentId ?? "<unknown>"}.");
+        await onEvent(activity).ConfigureAwait(false);
+
+        if (string.Equals(activity.ActivityType, "handoff", StringComparison.Ordinal)
+            && !string.IsNullOrWhiteSpace(activity.AgentId)
+            && !string.IsNullOrWhiteSpace(activity.AgentName))
+        {
+            TraceHandoff(
+                command,
+                $"Promoting handoff target to thinking: {activity.AgentName} ({activity.AgentId}).");
+            await state.EmitThinkingIfNeeded(
+                new AgentIdentity(activity.AgentId, activity.AgentName),
+                onEvent).ConfigureAwait(false);
+        }
+    }
+
+    internal static bool TryCreateWorkflowCheckpointSavedEvent(
+        RunTurnCommandDto command,
+        WorkflowEvent evt,
+        out WorkflowCheckpointSavedEventDto checkpointSaved)
+    {
+        checkpointSaved = default!;
+
+        if (!ShouldEnableWorkflowCheckpointing(command)
+            || evt is not SuperStepCompletedEvent superStepCompleted
+            || superStepCompleted.CompletionInfo?.Checkpoint is not CheckpointInfo checkpoint)
+        {
+            return false;
+        }
+
+        checkpointSaved = new WorkflowCheckpointSavedEventDto
+        {
+            Type = "workflow-checkpoint-saved",
+            RequestId = command.RequestId,
+            SessionId = command.SessionId,
+            WorkflowSessionId = checkpoint.SessionId,
+            CheckpointId = checkpoint.CheckpointId,
+            StorePath = GetCheckpointStorePath(command),
+            StepNumber = superStepCompleted.StepNumber,
+        };
+        return true;
+    }
+
+    private static bool TryCreateWorkflowDiagnosticEvent(
+        RunTurnCommandDto command,
+        WorkflowEvent evt,
+        TurnExecutionState state,
+        out WorkflowDiagnosticEventDto diagnostic)
+    {
+        diagnostic = default!;
+
+        switch (evt)
+        {
+            case ExecutorFailedEvent executorFailed:
+            {
+                AgentIdentity? agent = AgentIdentityResolver.TryResolveObservedAgentIdentity(
+                    command.Workflow,
+                    executorFailed.ExecutorId,
+                    state.ActiveAgent,
+                    out AgentIdentity resolvedAgent)
+                    ? resolvedAgent
+                    : null;
+                Exception? exception = executorFailed.Data;
+                diagnostic = new WorkflowDiagnosticEventDto
+                {
+                    Type = "workflow-diagnostic",
+                    RequestId = command.RequestId,
+                    SessionId = command.SessionId,
+                    Severity = "error",
+                    DiagnosticKind = "executor-failed",
+                    Message = ResolveDiagnosticMessage(exception, "Executor failed."),
+                    AgentId = agent?.AgentId,
+                    AgentName = agent?.AgentName,
+                    ExecutorId = executorFailed.ExecutorId,
+                    ExceptionType = exception?.GetBaseException().GetType().Name,
+                };
+                return true;
+            }
+            case WorkflowWarningEvent workflowWarning:
+                diagnostic = new WorkflowDiagnosticEventDto
+                {
+                    Type = "workflow-diagnostic",
+                    RequestId = command.RequestId,
+                    SessionId = command.SessionId,
+                    Severity = "warning",
+                    DiagnosticKind = workflowWarning is SubworkflowWarningEvent
+                        ? "subworkflow-warning"
+                        : "workflow-warning",
+                    Message = ResolveDiagnosticMessage(workflowWarning.Data as string, "Workflow warning."),
+                    SubworkflowId = workflowWarning is SubworkflowWarningEvent subworkflowWarning
+                        ? subworkflowWarning.SubWorkflowId
+                        : null,
+                };
+                return true;
+            case WorkflowErrorEvent workflowError:
+            {
+                Exception? exception = workflowError.Exception;
+                diagnostic = new WorkflowDiagnosticEventDto
+                {
+                    Type = "workflow-diagnostic",
+                    RequestId = command.RequestId,
+                    SessionId = command.SessionId,
+                    Severity = "error",
+                    DiagnosticKind = workflowError is SubworkflowErrorEvent
+                        ? "subworkflow-error"
+                        : "workflow-error",
+                    Message = ResolveDiagnosticMessage(exception, "Workflow failed."),
+                    SubworkflowId = workflowError is SubworkflowErrorEvent subworkflowError
+                        ? subworkflowError.SubworkflowId
+                        : null,
+                    ExceptionType = exception?.GetBaseException().GetType().Name,
+                };
+                return true;
+            }
+            default:
+                return false;
+        }
+    }
+
+    private static bool TryResolveRequestPortMetadata(
+        WorkflowDefinitionDto? workflow,
+        RequestInfoEvent requestInfo,
+        out WorkflowRequestPortMetadata? metadata)
+    {
+        metadata = null;
+        if (workflow is null)
+        {
+            return false;
+        }
+
+        string portId = requestInfo.Request.PortInfo.PortId;
+        WorkflowNodeDto? node = workflow.Graph.Nodes.FirstOrDefault(candidate =>
+            string.Equals(candidate.Kind, "request-port", StringComparison.OrdinalIgnoreCase)
+            && string.Equals(candidate.Config.PortId, portId, StringComparison.OrdinalIgnoreCase));
+
+        if (node is null)
+        {
+            return false;
+        }
+
+        metadata = new WorkflowRequestPortMetadata(
+            node.Id,
+            string.IsNullOrWhiteSpace(node.Label) ? node.Id : node.Label,
+            node.Config.PortId ?? portId,
+            node.Config.RequestType ?? string.Empty,
+            node.Config.ResponseType ?? string.Empty,
+            string.IsNullOrWhiteSpace(node.Config.Prompt) ? null : node.Config.Prompt.Trim());
+        return true;
+    }
+
+    private static string BuildRequestPortFallbackQuestion(
+        WorkflowRequestPortMetadata metadata,
+        RequestInfoEvent requestInfo)
+    {
+        if (requestInfo.Request.Data.Is<WorkflowRequestPortPromptRequest>(out WorkflowRequestPortPromptRequest? promptRequest))
+        {
+            string baseQuestion = $"Provide a {metadata.ResponseType} response for \"{promptRequest.NodeLabel}\".";
+            if (!string.IsNullOrWhiteSpace(promptRequest.InputSummary))
+            {
+                return $"{baseQuestion} Current input: {promptRequest.InputSummary}";
+            }
+
+            return baseQuestion;
+        }
+
+        return $"Provide a {metadata.ResponseType} response for request port \"{metadata.NodeLabel}\" ({metadata.PortId}).";
+    }
+
+    private static bool IsStringResponseType(string responseType)
+        => string.Equals(responseType, "string", StringComparison.OrdinalIgnoreCase)
+           || string.Equals(responseType, "text", StringComparison.OrdinalIgnoreCase);
+
+    private static bool IsBooleanResponseType(string responseType)
+        => string.Equals(responseType, "bool", StringComparison.OrdinalIgnoreCase)
+           || string.Equals(responseType, "boolean", StringComparison.OrdinalIgnoreCase);
+
+    private static bool IsNumericResponseType(string responseType)
+        => string.Equals(responseType, "number", StringComparison.OrdinalIgnoreCase)
+           || string.Equals(responseType, "int", StringComparison.OrdinalIgnoreCase)
+           || string.Equals(responseType, "float", StringComparison.OrdinalIgnoreCase)
+           || string.Equals(responseType, "double", StringComparison.OrdinalIgnoreCase)
+           || string.Equals(responseType, "decimal", StringComparison.OrdinalIgnoreCase);
+
+    private static bool IsJsonResponseType(string responseType)
+        => string.Equals(responseType, "json", StringComparison.OrdinalIgnoreCase)
+           || string.Equals(responseType, "object", StringComparison.OrdinalIgnoreCase)
+           || string.Equals(responseType, "array", StringComparison.OrdinalIgnoreCase);
+
+    internal sealed record WorkflowRequestPortMetadata(
+        string NodeId,
+        string NodeLabel,
+        string PortId,
+        string RequestType,
+        string ResponseType,
+        string? Prompt);
+
+    private static string ResolveDiagnosticMessage(Exception? exception, string fallback)
+    {
+        return ResolveDiagnosticMessage(
+            exception?.GetBaseException().Message,
+            fallback);
+    }
+
+    private static string ResolveDiagnosticMessage(string? message, string fallback)
+    {
+        return string.IsNullOrWhiteSpace(message) ? fallback : message;
+    }
+
+    private static bool IsHandoffFunctionName(string? candidate)
+    {
+        return !string.IsNullOrWhiteSpace(candidate)
+            && candidate.StartsWith(HandoffFunctionPrefix, StringComparison.Ordinal);
+    }
+
+    private static void TraceHandoff(RunTurnCommandDto command, string message)
+    {
+        if (!command.Workflow.IsOrchestrationMode("handoff"))
+        {
+            return;
+        }
+
+        Console.Error.WriteLine($"[aryx handoff] {message}");
+    }
+}

sidecar/src/Aryx.AgentHost/Services/CopilotTurnExecutionState.cs

@@ -1,669 +1,24 @@
-using System.Collections.Concurrent;
 using Aryx.AgentHost.Contracts;
 using Microsoft.Extensions.AI;
 
 namespace Aryx.AgentHost.Services;
 
-internal sealed class CopilotTurnExecutionState
+internal sealed class CopilotTurnExecutionState : TurnExecutionState
 {
-    private readonly RunTurnCommandDto _command;
-    private readonly HashSet<string> _startedAgents = new(StringComparer.OrdinalIgnoreCase);
-    private readonly HashSet<string> _reclassifiedMessageIds = new(StringComparer.Ordinal);
-    private readonly ConcurrentQueue<SidecarEventDto> _pendingEvents = new();
-    private readonly ConcurrentQueue<McpOauthRequiredEventDto> _pendingMcpOauthRequests = new();
-    private readonly ConcurrentDictionary<string, AgentIdentity> _observedAgentsByMessageId = new(StringComparer.Ordinal);
-    private readonly StreamingTranscriptBuffer _transcriptBuffer = new();
-    private int _fallbackMessageIndex;
-    private string? _lastObservedMessageId;
-
     public CopilotTurnExecutionState(RunTurnCommandDto command)
+        : base(command)
     {
-        _command = command;
-    }
-
-    public ConcurrentDictionary<string, string> ToolNamesByCallId { get; } = new(StringComparer.Ordinal);
-
-    public AgentIdentity? ActiveAgent { get; private set; }
-
-    public List<ChatMessageDto> CompletedMessages { get; private set; } = [];
-
-    public bool HasPendingExitPlanModeRequest { get; private set; }
-
-    public bool SuppressHookLifecycleEvents { get; set; }
-
-    public async Task EmitThinkingIfNeeded(
-        AgentIdentity agent,
-        Func<SidecarEventDto, Task> onEvent)
-    {
-        AgentActivityEventDto? thinkingActivity = CreateThinkingActivityIfNeeded(agent);
-        if (thinkingActivity is null)
-        {
-            return;
-        }
-
-        await onEvent(thinkingActivity).ConfigureAwait(false);
-    }
-
-    public void QueueThinkingIfNeeded(AgentIdentity agent)
-    {
-        AgentActivityEventDto? thinkingActivity = CreateThinkingActivityIfNeeded(agent);
-        if (thinkingActivity is not null)
-        {
-            _pendingEvents.Enqueue(thinkingActivity);
-        }
-    }
-
-    public void QueueCompletedActivity(AgentIdentity agent)
-    {
-        _pendingEvents.Enqueue(CreateCompletedActivity(agent));
-    }
-
-    public void ApplyEvent(SidecarEventDto evt)
-    {
-        if (evt is AgentActivityEventDto activity
-            && string.Equals(activity.ActivityType, "handoff", StringComparison.Ordinal)
-            && !string.IsNullOrWhiteSpace(activity.AgentId)
-            && !string.IsNullOrWhiteSpace(activity.AgentName))
-        {
-            ActiveAgent = new AgentIdentity(activity.AgentId, activity.AgentName);
-        }
-    }
-
-    public void ObserveSessionEvent(WorkflowNodeDto agentDefinition, ProviderSessionEvent sessionEvent)
-    {
-        AgentIdentity agent = AgentIdentityResolver.ResolveAgentIdentity(
-            _command.Workflow,
-            agentDefinition.GetAgentId(),
-            agentDefinition.GetAgentName());
-
-        switch (sessionEvent)
-        {
-            case ProviderAssistantMessageDeltaEvent messageDelta:
-                RecordObservedAgentForMessage(agent, messageDelta.MessageId);
-                QueueThinkingIfNeeded(agent);
-                break;
-            case ProviderAssistantMessageEvent assistantMessage:
-                RecordObservedAgentForMessage(agent, assistantMessage.MessageId);
-                QueueThinkingIfNeeded(agent);
-                if (assistantMessage.HasToolRequests)
-                {
-                    QueueMessageReclassifiedIfNeeded(assistantMessage.MessageId);
-                }
-                break;
-            case ProviderToolExecutionStartEvent toolExecutionStart:
-                string toolCallId = toolExecutionStart.ToolCallId;
-                string toolName = toolExecutionStart.ToolName;
-                ToolNamesByCallId[toolCallId] = toolName;
-                ActiveAgent = agent;
-                AgentActivityEventDto? toolActivity = CreateToolCallingActivity(
-                    agent, toolName, toolCallId, toolExecutionStart.ToolArguments);
-                if (toolActivity is not null)
-                {
-                    _pendingEvents.Enqueue(toolActivity);
-                }
-
-                QueueMessageReclassifiedIfNeeded(_lastObservedMessageId);
-                break;
-            case ProviderAssistantIntentEvent intentEvent:
-                ActiveAgent = agent;
-                QueueThinkingIfNeeded(agent);
-                AssistantIntentEventDto? assistantIntent = CreateAssistantIntentEvent(agent, intentEvent.Intent);
-                if (assistantIntent is not null)
-                {
-                    _pendingEvents.Enqueue(assistantIntent);
-                }
-                break;
-            case ProviderAssistantReasoningDeltaEvent reasoningDelta:
-                ActiveAgent = agent;
-                QueueThinkingIfNeeded(agent);
-                ReasoningDeltaEventDto? reasoningDeltaEvent = CreateReasoningDeltaEvent(
-                    agent,
-                    reasoningDelta.ReasoningId,
-                    reasoningDelta.DeltaContent);
-                if (reasoningDeltaEvent is not null)
-                {
-                    _pendingEvents.Enqueue(reasoningDeltaEvent);
-                }
-                break;
-            case ProviderSubagentStartedEvent started:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateSubagentStartedEvent(agent, started));
-                break;
-            case ProviderSubagentCompletedEvent completed:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateSubagentCompletedEvent(agent, completed));
-                break;
-            case ProviderSubagentFailedEvent failed:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateSubagentFailedEvent(agent, failed));
-                break;
-            case ProviderSubagentSelectedEvent selected:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateSubagentSelectedEvent(agent, selected));
-                break;
-            case ProviderSubagentDeselectedEvent:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateSubagentDeselectedEvent(agent));
-                break;
-            case ProviderSkillInvokedEvent skillInvoked:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateSkillInvokedEvent(agent, skillInvoked));
-                break;
-            case ProviderHookStartEvent hookStart:
-                ActiveAgent = agent;
-                if (!SuppressHookLifecycleEvents)
-                {
-                    _pendingEvents.Enqueue(CreateHookLifecycleEvent(
-                        agent,
-                        "start",
-                        hookStart.HookInvocationId,
-                        hookStart.HookType,
-                        input: hookStart.Input));
-                }
-                break;
-            case ProviderHookEndEvent hookEnd:
-                ActiveAgent = agent;
-                if (!SuppressHookLifecycleEvents)
-                {
-                    _pendingEvents.Enqueue(CreateHookLifecycleEvent(
-                        agent,
-                        "end",
-                        hookEnd.HookInvocationId,
-                        hookEnd.HookType,
-                        success: hookEnd.Success,
-                        output: hookEnd.Output,
-                        error: hookEnd.Error));
-                }
-                break;
-            case ProviderAssistantUsageEvent assistantUsage:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateAssistantUsageEvent(agent, assistantUsage));
-                break;
-            case ProviderSessionUsageEvent usageInfo:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateUsageEvent(agent, usageInfo));
-                break;
-            case ProviderSessionCompactionStartEvent compactionStart:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateCompactionStartEvent(agent, compactionStart));
-                break;
-            case ProviderSessionCompactionCompleteEvent compactionComplete:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreateCompactionCompleteEvent(agent, compactionComplete));
-                break;
-            case ProviderPendingMessagesModifiedEvent:
-                ActiveAgent = agent;
-                _pendingEvents.Enqueue(CreatePendingMessagesModifiedEvent(agent));
-                break;
-            case ProviderMcpOauthRequiredEvent:
-                ActiveAgent = agent;
-                break;
-            case ProviderExitPlanModeRequestedEvent:
-                HasPendingExitPlanModeRequest = true;
-                ActiveAgent = agent;
-                break;
-        }
-    }
-
-    public IReadOnlyList<SidecarEventDto> DrainPendingEvents()
-    {
-        List<SidecarEventDto> pending = [];
-        while (_pendingEvents.TryDequeue(out SidecarEventDto? pendingEvent))
-        {
-            pending.Add(pendingEvent);
-        }
-
-        return pending;
-    }
-
-    public void EnqueuePendingMcpOauthRequest(McpOauthRequiredEventDto request)
-    {
-        ArgumentNullException.ThrowIfNull(request);
-        _pendingMcpOauthRequests.Enqueue(request);
-    }
-
-    public IReadOnlyList<McpOauthRequiredEventDto> DrainPendingMcpOauthRequests()
-    {
-        List<McpOauthRequiredEventDto> pending = [];
-        while (_pendingMcpOauthRequests.TryDequeue(out McpOauthRequiredEventDto? request))
-        {
-            pending.Add(request);
-        }
-
-        return pending;
-    }
-
-    public bool TryResolveObservedAgentForMessage(string? messageId, out AgentIdentity agent)
-    {
-        agent = default;
-        return !string.IsNullOrWhiteSpace(messageId)
-            && _observedAgentsByMessageId.TryGetValue(messageId, out agent);
-    }
-
-    public string CreateMessageId(string? messageId)
-    {
-        return messageId ?? $"{_command.RequestId}-delta-{_fallbackMessageIndex++}";
-    }
-
-    public TranscriptSegment AppendDelta(
-        string messageId,
-        string authorName,
-        string delta)
-    {
-        return _transcriptBuffer.AppendDelta(messageId, authorName, delta);
-    }
-
-    public void ClearActiveAgentIfMatching(AgentIdentity completedAgent)
-    {
-        if (ActiveAgent.HasValue
-            && string.Equals(ActiveAgent.Value.AgentId, completedAgent.AgentId, StringComparison.Ordinal))
-        {
-            ActiveAgent = null;
-        }
-    }
-
-    private void RecordObservedAgentForMessage(AgentIdentity agent, string messageId)
-    {
-        ActiveAgent = agent;
-        _observedAgentsByMessageId[messageId] = agent;
-        _lastObservedMessageId = messageId;
-    }
-
-    private void QueueMessageReclassifiedIfNeeded(string? messageId)
-    {
-        if (string.IsNullOrWhiteSpace(messageId))
-        {
-            return;
-        }
-
-        string normalizedMessageId = messageId.Trim();
-        if (!_reclassifiedMessageIds.Add(normalizedMessageId))
-        {
-            return;
-        }
-
-        _pendingEvents.Enqueue(CreateMessageReclassifiedEvent(normalizedMessageId));
-    }
-
-    private AgentActivityEventDto? CreateThinkingActivityIfNeeded(AgentIdentity agent)
-    {
-        ActiveAgent = agent;
-
-        if (!_startedAgents.Add(agent.AgentId))
-        {
-            return null;
-        }
-
-        return new AgentActivityEventDto
-        {
-            Type = "agent-activity",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            ActivityType = "thinking",
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-        };
-    }
-
-    private AgentActivityEventDto? CreateToolCallingActivity(
-        AgentIdentity agent,
-        string toolName,
-        string toolCallId,
-        IReadOnlyDictionary<string, object?>? toolArguments = null)
-    {
-        if (toolName.StartsWith("handoff_to_", StringComparison.Ordinal))
-        {
-            return null;
-        }
-
-        return new AgentActivityEventDto
-        {
-            Type = "agent-activity",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            ActivityType = "tool-calling",
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            ToolName = toolName,
-            ToolCallId = toolCallId,
-            ToolArguments = toolArguments,
-        };
-    }
-
-    private AgentActivityEventDto CreateCompletedActivity(AgentIdentity agent)
-    {
-        return new AgentActivityEventDto
-        {
-            Type = "agent-activity",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            ActivityType = "completed",
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-        };
-    }
-
-    private MessageReclassifiedEventDto CreateMessageReclassifiedEvent(string messageId)
-    {
-        return new MessageReclassifiedEventDto
-        {
-            Type = "message-reclassified",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            MessageId = messageId,
-            NewKind = "thinking",
-        };
     }
 
     public void UpdateCompletedMessages(
         IReadOnlyList<ChatMessage> allMessages,
         IReadOnlyList<ChatMessage> inputMessages)
     {
-        List<ChatMessage> newMessages = WorkflowTranscriptProjector.SelectNewOutputMessages(allMessages, inputMessages);
+        base.UpdateCompletedMessages(allMessages, inputMessages, CopilotTranscriptProjector.Instance);
-        CompletedMessages = WorkflowTranscriptProjector.ProjectCompletedMessagesFromSegments(
-            _command,
-            newMessages,
-            _transcriptBuffer.Snapshot(),
-            ActiveAgent);
     }
 
     public IReadOnlyList<ChatMessageDto> FinalizeCompletedMessages()
     {
-        if (CompletedMessages.Count == 0 && _transcriptBuffer.Count > 0)
+        return base.FinalizeCompletedMessages(CopilotTranscriptProjector.Instance);
-        {
-            CompletedMessages = WorkflowTranscriptProjector.ProjectCompletedMessagesFromSegments(
-                _command,
-                [],
-                _transcriptBuffer.Snapshot(),
-                ActiveAgent);
-        }
-
-        foreach (ChatMessageDto message in CompletedMessages)
-        {
-            if (_reclassifiedMessageIds.Contains(message.Id))
-            {
-                message.MessageKind = "thinking";
-            }
-        }
-
-        return CompletedMessages;
-    }
-
-    private SubagentEventDto CreateSubagentStartedEvent(
-        AgentIdentity agent,
-        ProviderSubagentStartedEvent data)
-    {
-        return new SubagentEventDto
-        {
-            Type = "subagent-event",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            EventKind = "started",
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            ToolCallId = data.ToolCallId,
-            CustomAgentName = data.AgentName,
-            CustomAgentDisplayName = data.AgentDisplayName,
-            CustomAgentDescription = data.AgentDescription,
-        };
-    }
-
-    private SubagentEventDto CreateSubagentCompletedEvent(
-        AgentIdentity agent,
-        ProviderSubagentCompletedEvent data)
-    {
-        return new SubagentEventDto
-        {
-            Type = "subagent-event",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            EventKind = "completed",
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            ToolCallId = data.ToolCallId,
-            CustomAgentName = data.AgentName,
-            CustomAgentDisplayName = data.AgentDisplayName,
-        };
-    }
-
-    private SubagentEventDto CreateSubagentFailedEvent(
-        AgentIdentity agent,
-        ProviderSubagentFailedEvent data)
-    {
-        return new SubagentEventDto
-        {
-            Type = "subagent-event",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            EventKind = "failed",
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            ToolCallId = data.ToolCallId,
-            CustomAgentName = data.AgentName,
-            CustomAgentDisplayName = data.AgentDisplayName,
-            Error = data.Error,
-        };
-    }
-
-    private SubagentEventDto CreateSubagentSelectedEvent(
-        AgentIdentity agent,
-        ProviderSubagentSelectedEvent data)
-    {
-        return new SubagentEventDto
-        {
-            Type = "subagent-event",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            EventKind = "selected",
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            CustomAgentName = data.AgentName,
-            CustomAgentDisplayName = data.AgentDisplayName,
-            Tools = data.Tools,
-        };
-    }
-
-    private SubagentEventDto CreateSubagentDeselectedEvent(AgentIdentity agent)
-    {
-        return new SubagentEventDto
-        {
-            Type = "subagent-event",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            EventKind = "deselected",
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-        };
-    }
-
-    private AssistantIntentEventDto? CreateAssistantIntentEvent(
-        AgentIdentity agent,
-        string? intent)
-    {
-        string? normalizedIntent = intent?.Trim();
-        if (string.IsNullOrWhiteSpace(normalizedIntent))
-        {
-            return null;
-        }
-
-        return new AssistantIntentEventDto
-        {
-            Type = "assistant-intent",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            Intent = normalizedIntent,
-        };
-    }
-
-    private ReasoningDeltaEventDto? CreateReasoningDeltaEvent(
-        AgentIdentity agent,
-        string? reasoningId,
-        string? deltaContent)
-    {
-        if (string.IsNullOrWhiteSpace(reasoningId)
-            || string.IsNullOrEmpty(deltaContent))
-        {
-            return null;
-        }
-
-        return new ReasoningDeltaEventDto
-        {
-            Type = "reasoning-delta",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            ReasoningId = reasoningId,
-            ContentDelta = deltaContent,
-        };
-    }
-
-    private SkillInvokedEventDto CreateSkillInvokedEvent(
-        AgentIdentity agent,
-        ProviderSkillInvokedEvent data)
-    {
-        return new SkillInvokedEventDto
-        {
-            Type = "skill-invoked",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            SkillName = data.SkillName,
-            Path = data.Path,
-            Content = data.Content,
-            AllowedTools = data.AllowedTools,
-            PluginName = data.PluginName,
-            PluginVersion = data.PluginVersion,
-        };
-    }
-
-    private HookLifecycleEventDto CreateHookLifecycleEvent(
-        AgentIdentity agent,
-        string phase,
-        string hookInvocationId,
-        string hookType,
-        object? input = null,
-        bool? success = null,
-        object? output = null,
-        string? error = null)
-    {
-        return new HookLifecycleEventDto
-        {
-            Type = "hook-lifecycle",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            HookInvocationId = hookInvocationId,
-            HookType = hookType,
-            Phase = phase,
-            Input = input,
-            Success = success,
-            Output = output,
-            Error = error,
-        };
-    }
-
-    private AssistantUsageEventDto CreateAssistantUsageEvent(
-        AgentIdentity agent,
-        ProviderAssistantUsageEvent data)
-    {
-        return new AssistantUsageEventDto
-        {
-            Type = "assistant-usage",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            Model = data.Model,
-            InputTokens = data.InputTokens,
-            OutputTokens = data.OutputTokens,
-            CacheReadTokens = data.CacheReadTokens,
-            CacheWriteTokens = data.CacheWriteTokens,
-            Cost = data.Cost,
-            Duration = data.Duration,
-            TotalNanoAiu = data.TotalNanoAiu,
-            QuotaSnapshots = data.QuotaSnapshots,
-        };
-    }
-
-    private SessionUsageEventDto CreateUsageEvent(AgentIdentity agent, ProviderSessionUsageEvent data)
-    {
-        return new SessionUsageEventDto
-        {
-            Type = "session-usage",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            TokenLimit = data.TokenLimit,
-            CurrentTokens = data.CurrentTokens,
-            MessagesLength = data.MessagesLength,
-            SystemTokens = data.SystemTokens,
-            ConversationTokens = data.ConversationTokens,
-            ToolDefinitionsTokens = data.ToolDefinitionsTokens,
-            IsInitial = data.IsInitial,
-        };
-    }
-
-    private SessionCompactionEventDto CreateCompactionStartEvent(
-        AgentIdentity agent,
-        ProviderSessionCompactionStartEvent data)
-    {
-        return new SessionCompactionEventDto
-        {
-            Type = "session-compaction",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            Phase = "start",
-            SystemTokens = data.SystemTokens,
-            ConversationTokens = data.ConversationTokens,
-            ToolDefinitionsTokens = data.ToolDefinitionsTokens,
-        };
-    }
-
-    private SessionCompactionEventDto CreateCompactionCompleteEvent(
-        AgentIdentity agent,
-        ProviderSessionCompactionCompleteEvent data)
-    {
-        return new SessionCompactionEventDto
-        {
-            Type = "session-compaction",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-            Phase = "complete",
-            Success = data.Success,
-            Error = data.Error,
-            SystemTokens = data.SystemTokens,
-            ConversationTokens = data.ConversationTokens,
-            ToolDefinitionsTokens = data.ToolDefinitionsTokens,
-            PreCompactionTokens = data.PreCompactionTokens,
-            PostCompactionTokens = data.PostCompactionTokens,
-            PreCompactionMessagesLength = data.PreCompactionMessagesLength,
-            MessagesRemoved = data.MessagesRemoved,
-            TokensRemoved = data.TokensRemoved,
-            SummaryContent = data.SummaryContent,
-            CheckpointNumber = data.CheckpointNumber,
-            CheckpointPath = data.CheckpointPath,
-        };
-    }
-
-    private PendingMessagesModifiedEventDto CreatePendingMessagesModifiedEvent(AgentIdentity agent)
-    {
-        return new PendingMessagesModifiedEventDto
-        {
-            Type = "pending-messages-modified",
-            RequestId = _command.RequestId,
-            SessionId = _command.SessionId,
-            AgentId = agent.AgentId,
-            AgentName = agent.AgentName,
-        };
     }
 }

sidecar/src/Aryx.AgentHost/Services/IProviderTranscriptProjector.cs

@@ -0,0 +1,21 @@
+using Aryx.AgentHost.Contracts;
+using Microsoft.Extensions.AI;
+
+namespace Aryx.AgentHost.Services;
+
+internal interface IProviderTranscriptProjector
+{
+    ChatMessage ToChatMessage(ChatMessageDto message);
+
+    void AttachMessageMode(IList<ChatMessage> messages, string? messageMode);
+
+    List<ChatMessage> SelectNewOutputMessages(
+        IReadOnlyList<ChatMessage> outputMessages,
+        IReadOnlyList<ChatMessage> inputMessages);
+
+    List<ChatMessageDto> ProjectCompletedMessagesFromSegments(
+        RunTurnCommandDto command,
+        IReadOnlyList<ChatMessage> newMessages,
+        IReadOnlyList<TranscriptSegment> segments,
+        AgentIdentity? fallbackAgent = null);
+}

sidecar/src/Aryx.AgentHost/Services/IProviderTurnSupport.cs

@@ -0,0 +1,34 @@
+using Aryx.AgentHost.Contracts;
+using GitHub.Copilot.SDK;
+
+namespace Aryx.AgentHost.Services;
+
+internal interface IProviderTurnSupport
+{
+    Task<ProviderAgentBundle> CreateAgentBundleAsync(
+        RunTurnCommandDto command,
+        TurnExecutionState state,
+        Func<SidecarEventDto, Task> onEvent,
+        Func<ApprovalRequestedEventDto, Task> onApproval,
+        Func<UserInputRequestedEventDto, Task> onUserInput,
+        CancellationTokenSource runCancellation,
+        CancellationToken cancellationToken);
+
+    Task ResolveApprovalAsync(
+        ResolveApprovalCommandDto command,
+        CancellationToken cancellationToken);
+
+    Task ResolveUserInputAsync(
+        ResolveUserInputCommandDto command,
+        CancellationToken cancellationToken);
+
+    Task<UserInputResponse> RequestRequestPortUserInputAsync(
+        RunTurnCommandDto command,
+        UserInputRequest request,
+        Func<UserInputRequestedEventDto, Task> onUserInput,
+        CancellationToken cancellationToken);
+
+    ExitPlanModeRequestedEventDto? ConsumePendingExitPlanModeRequest(string requestId);
+
+    void ClearRequestState(string requestId);
+}

sidecar/src/Aryx.AgentHost/Services/ProviderAgentBundle.cs

@@ -0,0 +1,14 @@
+using Microsoft.Agents.AI;
+
+namespace Aryx.AgentHost.Services;
+
+internal abstract class ProviderAgentBundle : IAsyncDisposable
+{
+    public abstract IReadOnlyList<AIAgent> Agents { get; }
+
+    public abstract bool HasConfiguredHooks { get; }
+
+    public abstract IProviderTranscriptProjector TranscriptProjector { get; }
+
+    public abstract ValueTask DisposeAsync();
+}

sidecar/src/Aryx.AgentHost/Services/Providers/Copilot/CopilotAgentBundle.cs

@@ -8,7 +8,7 @@ using Microsoft.Extensions.AI;
 
 namespace Aryx.AgentHost.Services;
 
-internal sealed class CopilotAgentBundle : IAsyncDisposable
+internal sealed class CopilotAgentBundle : ProviderAgentBundle
 {
     private static readonly string[] RequiredPromptTools =
     [
@@ -25,9 +25,11 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
         HasConfiguredHooks = hasConfiguredHooks;
     }
 
-    public IReadOnlyList<AIAgent> Agents { get; }
+    public override IReadOnlyList<AIAgent> Agents { get; }
 
-    public bool HasConfiguredHooks { get; }
+    public override bool HasConfiguredHooks { get; }
+
+    public override IProviderTranscriptProjector TranscriptProjector { get; } = CopilotTranscriptProjector.Instance;
 
     public static async Task<CopilotAgentBundle> CreateAsync(
         RunTurnCommandDto command,
@@ -215,116 +217,38 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
 
     internal static AIAgentHostOptions CreateAgentHostOptions()
     {
-        return new AIAgentHostOptions
+        return AgentHostOptionsFactory.CreateDefault();
-        {
-            EmitAgentUpdateEvents = null,
-            EmitAgentResponseEvents = false,
-            InterceptUserInputRequests = false,
-            InterceptUnterminatedFunctionCalls = false,
-            ReassignOtherAgentsAsUsers = true,
-            ForwardIncomingMessages = true,
-        };
     }
 
     internal static HandoffWorkflowBuilder CreateHandoffWorkflowBuilder(
         AIAgent entryAgent,
         HandoffModeSettingsDto? settings = null)
     {
-        HandoffModeSettingsDto effectiveSettings = settings ?? new HandoffModeSettingsDto();
+        return WorkflowOrchestrationFactory.CreateHandoffWorkflowBuilder(entryAgent, settings);
-        HandoffWorkflowBuilder builder = AgentWorkflowBuilder.CreateHandoffBuilderWith(entryAgent)
-            .WithToolCallFilteringBehavior(MapHandoffToolCallFiltering(effectiveSettings.ToolCallFiltering))
-            .WithHandoffInstructions(NormalizeOptionalString(effectiveSettings.HandoffInstructions)
-                ?? HandoffWorkflowGuidance.CreateWorkflowInstructions());
-
-        if (effectiveSettings.ReturnToPrevious)
-        {
-            builder = builder.EnableReturnToPrevious();
-        }
-
-        return builder;
     }
 
     internal static Workflow CreateHandoffWorkflow(
         WorkflowDefinitionDto workflowDefinition,
         IReadOnlyList<AIAgent> agents)
     {
-        ArgumentNullException.ThrowIfNull(workflowDefinition);
+        return WorkflowOrchestrationFactory.CreateHandoffWorkflow(workflowDefinition, agents);
-        ArgumentNullException.ThrowIfNull(agents);
-
-        IReadOnlyList<WorkflowNodeDto> agentNodes = workflowDefinition.GetAgentNodes();
-        Dictionary<string, AIAgent> agentsById = CreateAgentMap(agents);
-        WorkflowNodeDto triageNode = ResolveTriageAgentNode(workflowDefinition, agentNodes);
-        AIAgent triageAgent = ResolveAgentForNode(triageNode, agentsById);
-        HandoffModeSettingsDto? settings = workflowDefinition.Settings.ModeSettings?.Handoff;
-        HandoffWorkflowBuilder builder = CreateHandoffWorkflowBuilder(triageAgent, settings);
-
-        List<WorkflowNodeDto> specialistNodes = agentNodes
-            .Where(node => !string.Equals(node.Id, triageNode.Id, StringComparison.Ordinal))
-            .ToList();
-
-        if (specialistNodes.Count == 0)
-        {
-            throw new InvalidOperationException("Handoff workflows require at least one specialist agent in addition to the triage agent.");
-        }
-
-        foreach (WorkflowNodeDto specialistNode in specialistNodes)
-        {
-            AIAgent specialistAgent = ResolveAgentForNode(specialistNode, agentsById);
-            builder.WithHandoff(
-                triageAgent,
-                specialistAgent,
-                HandoffWorkflowGuidance.CreateForwardReason(specialistNode));
-
-            if (settings?.ReturnToPrevious != true)
-            {
-                builder.WithHandoff(
-                    specialistAgent,
-                    triageAgent,
-                    HandoffWorkflowGuidance.CreateReturnReason(triageNode));
-            }
-        }
-
-        return builder.Build();
     }
 
     internal static GroupChatWorkflowBuilder CreateGroupChatWorkflowBuilder(
         WorkflowDefinitionDto workflowDefinition,
         IReadOnlyList<AIAgent> agents)
     {
-        ArgumentNullException.ThrowIfNull(workflowDefinition);
+        return WorkflowOrchestrationFactory.CreateGroupChatWorkflowBuilder(workflowDefinition, agents);
-        ArgumentNullException.ThrowIfNull(agents);
-
-        int maxRounds = ResolveGroupChatMaxRounds(workflowDefinition);
-        GroupChatWorkflowBuilder builder = AgentWorkflowBuilder.CreateGroupChatBuilderWith(
-            participants => new RoundRobinGroupChatManager(participants)
-            {
-                MaximumIterationCount = maxRounds,
-            })
-            .AddParticipants(agents);
-
-        string? name = NormalizeOptionalString(workflowDefinition.Name);
-        if (name is not null)
-        {
-            builder.WithName(name);
-        }
-
-        string? description = NormalizeOptionalString(workflowDefinition.Description);
-        if (description is not null)
-        {
-            builder.WithDescription(description);
-        }
-
-        return builder;
     }
 
     internal static Workflow CreateGroupChatWorkflow(
         WorkflowDefinitionDto workflowDefinition,
         IReadOnlyList<AIAgent> agents)
     {
-        return CreateGroupChatWorkflowBuilder(workflowDefinition, agents).Build();
+        return WorkflowOrchestrationFactory.CreateGroupChatWorkflow(workflowDefinition, agents);
     }
 
-    public async ValueTask DisposeAsync()
+    public override async ValueTask DisposeAsync()
     {
         foreach (IAsyncDisposable disposable in _disposables)
         {
@@ -380,90 +304,6 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
             .ToList();
     }
 
-    private static Dictionary<string, AIAgent> CreateAgentMap(IReadOnlyList<AIAgent> agents)
-    {
-        Dictionary<string, AIAgent> agentMap = new(StringComparer.OrdinalIgnoreCase);
-        foreach (AIAgent agent in agents)
-        {
-            if (!string.IsNullOrWhiteSpace(agent.Id))
-            {
-                agentMap[agent.Id] = agent;
-            }
-
-            if (!string.IsNullOrWhiteSpace(agent.Name))
-            {
-                agentMap[agent.Name] = agent;
-            }
-        }
-
-        return agentMap;
-    }
-
-    private static AIAgent ResolveAgentForNode(
-        WorkflowNodeDto node,
-        IReadOnlyDictionary<string, AIAgent> agentsById)
-    {
-        string agentId = node.GetAgentId();
-        if (agentsById.TryGetValue(agentId, out AIAgent? agent))
-        {
-            return agent;
-        }
-
-        string agentName = node.GetAgentName();
-        if (agentsById.TryGetValue(agentName, out agent))
-        {
-            return agent;
-        }
-
-        throw new InvalidOperationException($"Workflow agent \"{agentId}\" could not be resolved from the constructed Copilot agents.");
-    }
-
-    private static WorkflowNodeDto ResolveTriageAgentNode(
-        WorkflowDefinitionDto workflowDefinition,
-        IReadOnlyList<WorkflowNodeDto> agentNodes)
-    {
-        if (agentNodes.Count == 0)
-        {
-            throw new InvalidOperationException("Handoff workflows require at least one agent node.");
-        }
-
-        string? triageAgentNodeId = NormalizeOptionalString(workflowDefinition.Settings.ModeSettings?.Handoff?.TriageAgentNodeId);
-        if (triageAgentNodeId is null)
-        {
-            return agentNodes[0];
-        }
-
-        WorkflowNodeDto? triageNode = agentNodes.FirstOrDefault(node => string.Equals(node.Id, triageAgentNodeId, StringComparison.Ordinal));
-        return triageNode ?? throw new InvalidOperationException(
-            $"Handoff workflow triage agent node \"{triageAgentNodeId}\" was not found in the workflow graph.");
-    }
-
-    private static HandoffToolCallFilteringBehavior MapHandoffToolCallFiltering(string? value)
-    {
-        return value?.Trim().ToLowerInvariant() switch
-        {
-            "none" => HandoffToolCallFilteringBehavior.None,
-            "all" => HandoffToolCallFilteringBehavior.All,
-            _ => HandoffToolCallFilteringBehavior.HandoffOnly,
-        };
-    }
-
-    private static int ResolveGroupChatMaxRounds(WorkflowDefinitionDto workflowDefinition)
-    {
-        int? configuredMaxRounds = workflowDefinition.Settings.ModeSettings?.GroupChat?.MaxRounds;
-        if (configuredMaxRounds is > 0)
-        {
-            return configuredMaxRounds.Value;
-        }
-
-        if (workflowDefinition.Settings.MaxIterations is > 0)
-        {
-            return workflowDefinition.Settings.MaxIterations.Value;
-        }
-
-        return 5;
-    }
-
     private static string? ResolveEffectiveAgent(
         string? defaultAgent,
         RunTurnPromptInvocationDto? promptInvocation)

sidecar/src/Aryx.AgentHost/Services/Providers/Copilot/CopilotAgentProvider.cs

@@ -30,7 +30,7 @@ internal sealed class CopilotAgentProvider : IAgentProvider
     public ITurnWorkflowRunner CreateWorkflowRunner(WorkflowValidator workflowValidator)
     {
         ArgumentNullException.ThrowIfNull(workflowValidator);
-        return new CopilotWorkflowRunner(workflowValidator);
+        return new AgentWorkflowTurnRunner(new CopilotTurnRunnerSupport(), workflowValidator);
     }
 
     public Task<SidecarCapabilitiesDto> GetCapabilitiesAsync(CancellationToken cancellationToken)

sidecar/src/Aryx.AgentHost/Services/Providers/Copilot/CopilotTranscriptProjector.cs

@@ -0,0 +1,35 @@
+using Aryx.AgentHost.Contracts;
+using Microsoft.Extensions.AI;
+
+namespace Aryx.AgentHost.Services;
+
+internal sealed class CopilotTranscriptProjector : IProviderTranscriptProjector
+{
+    public static CopilotTranscriptProjector Instance { get; } = new();
+
+    private CopilotTranscriptProjector()
+    {
+    }
+
+    public ChatMessage ToChatMessage(ChatMessageDto message)
+        => WorkflowTranscriptProjector.ToChatMessage(message);
+
+    public void AttachMessageMode(IList<ChatMessage> messages, string? messageMode)
+        => WorkflowTranscriptProjector.AttachMessageMode(messages, messageMode);
+
+    public List<ChatMessage> SelectNewOutputMessages(
+        IReadOnlyList<ChatMessage> outputMessages,
+        IReadOnlyList<ChatMessage> inputMessages)
+        => WorkflowTranscriptProjector.SelectNewOutputMessages(outputMessages, inputMessages);
+
+    public List<ChatMessageDto> ProjectCompletedMessagesFromSegments(
+        RunTurnCommandDto command,
+        IReadOnlyList<ChatMessage> newMessages,
+        IReadOnlyList<TranscriptSegment> segments,
+        AgentIdentity? fallbackAgent = null)
+        => WorkflowTranscriptProjector.ProjectCompletedMessagesFromSegments(
+            command,
+            newMessages,
+            segments,
+            fallbackAgent);
+}

sidecar/src/Aryx.AgentHost/Services/Providers/Copilot/CopilotTurnRunnerSupport.cs

@@ -0,0 +1,107 @@
+using Aryx.AgentHost.Contracts;
+using GitHub.Copilot.SDK;
+
+namespace Aryx.AgentHost.Services;
+
+internal sealed class CopilotTurnRunnerSupport : IProviderTurnSupport
+{
+    private readonly CopilotApprovalCoordinator _approvalCoordinator = new();
+    private readonly CopilotUserInputCoordinator _userInputCoordinator = new();
+    private readonly CopilotMcpOAuthCoordinator _mcpOAuthCoordinator = new();
+    private readonly CopilotExitPlanModeCoordinator _exitPlanModeCoordinator = new();
+    private readonly IProviderEventAdapter _providerEventAdapter = new CopilotEventAdapter();
+
+    public async Task<ProviderAgentBundle> CreateAgentBundleAsync(
+        RunTurnCommandDto command,
+        TurnExecutionState state,
+        Func<SidecarEventDto, Task> onEvent,
+        Func<ApprovalRequestedEventDto, Task> onApproval,
+        Func<UserInputRequestedEventDto, Task> onUserInput,
+        CancellationTokenSource runCancellation,
+        CancellationToken cancellationToken)
+    {
+        return await CopilotAgentBundle.CreateAsync(
+                command,
+                (agent, request, invocation) => _approvalCoordinator.RequestApprovalAsync(
+                    command,
+                    agent,
+                    request,
+                    invocation,
+                    state.ToolNamesByCallId,
+                    activity => AgentWorkflowTurnRunner.EmitActivityAsync(command, state, activity, onEvent),
+                    onApproval,
+                    runCancellation.Token),
+                (agent, request, invocation) => _userInputCoordinator.RequestUserInputAsync(
+                    command,
+                    agent,
+                    request,
+                    invocation,
+                    onUserInput,
+                    runCancellation.Token),
+                (agent, sessionEvent) => ObserveSessionEvent(command, state, runCancellation, agent, sessionEvent),
+                cancellationToken)
+            .ConfigureAwait(false);
+    }
+
+    public Task ResolveApprovalAsync(
+        ResolveApprovalCommandDto command,
+        CancellationToken cancellationToken)
+    {
+        return _approvalCoordinator.ResolveApprovalAsync(command, cancellationToken);
+    }
+
+    public Task ResolveUserInputAsync(
+        ResolveUserInputCommandDto command,
+        CancellationToken cancellationToken)
+    {
+        return _userInputCoordinator.ResolveUserInputAsync(command, cancellationToken);
+    }
+
+    public Task<UserInputResponse> RequestRequestPortUserInputAsync(
+        RunTurnCommandDto command,
+        UserInputRequest request,
+        Func<UserInputRequestedEventDto, Task> onUserInput,
+        CancellationToken cancellationToken)
+    {
+        return _userInputCoordinator.RequestUserInputAsync(
+            command,
+            request,
+            onUserInput,
+            cancellationToken);
+    }
+
+    public ExitPlanModeRequestedEventDto? ConsumePendingExitPlanModeRequest(string requestId)
+    {
+        return _exitPlanModeCoordinator.ConsumePendingRequest(requestId);
+    }
+
+    public void ClearRequestState(string requestId)
+    {
+        _approvalCoordinator.ClearRequestApprovals(requestId);
+    }
+
+    private void ObserveSessionEvent(
+        RunTurnCommandDto command,
+        TurnExecutionState state,
+        CancellationTokenSource runCancellation,
+        WorkflowNodeDto agent,
+        SessionEvent sessionEvent)
+    {
+        if (_providerEventAdapter.TryAdapt(sessionEvent) is { } providerEvent)
+        {
+            state.ObserveSessionEvent(agent, providerEvent);
+        }
+
+        if (sessionEvent is McpOauthRequiredEvent mcpOauthRequired)
+        {
+            state.EnqueuePendingMcpOauthRequest(
+                _mcpOAuthCoordinator.BuildMcpOauthRequiredEvent(command, agent, mcpOauthRequired));
+        }
+
+        if (sessionEvent is ExitPlanModeRequestedEvent exitPlanModeRequested)
+        {
+            _exitPlanModeCoordinator.RecordExitPlanModeRequest(command, agent, exitPlanModeRequested);
+            runCancellation.Cancel();
+        }
+    }
+}

sidecar/src/Aryx.AgentHost/Services/Providers/Copilot/CopilotWorkflowRunner.cs

@@ -1,6 +1,4 @@
 using System.IO;
-using System.Linq;
-using System.Globalization;
 using System.Text.Json;
 using Aryx.AgentHost.Contracts;
 using GitHub.Copilot.SDK;
@@ -12,301 +10,63 @@ using Microsoft.Extensions.AI;
 
 namespace Aryx.AgentHost.Services;
 
-public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
+public sealed class CopilotWorkflowRunner : AgentWorkflowTurnRunner
 {
-    private const string HandoffFunctionPrefix = "handoff_to_";
-    private readonly WorkflowValidator _workflowValidator;
-    private readonly WorkflowRunner _workflowRunner = new();
-    private readonly CopilotApprovalCoordinator _approvalCoordinator = new();
-    private readonly CopilotUserInputCoordinator _userInputCoordinator = new();
-    private readonly CopilotMcpOAuthCoordinator _mcpOAuthCoordinator = new();
-    private readonly CopilotExitPlanModeCoordinator _exitPlanModeCoordinator = new();
-
     public CopilotWorkflowRunner(WorkflowValidator? workflowValidator = null)
+        : base(new CopilotTurnRunnerSupport(), workflowValidator)
     {
-        _workflowValidator = workflowValidator ?? new WorkflowValidator();
     }
 
-    public async Task<IReadOnlyList<ChatMessageDto>> RunTurnAsync(
+    internal new static Workflow BuildWorkflowForCommand(
-        RunTurnCommandDto command,
-        Func<TurnDeltaEventDto, Task> onDelta,
-        Func<SidecarEventDto, Task> onEvent,
-        Func<ApprovalRequestedEventDto, Task> onApproval,
-        Func<UserInputRequestedEventDto, Task> onUserInput,
-        Func<McpOauthRequiredEventDto, Task> onMcpOAuthRequired,
-        Func<ExitPlanModeRequestedEventDto, Task> onExitPlanMode,
-        CancellationToken cancellationToken)
-    {
-        string? validationError = _workflowValidator.Validate(command.Workflow, command.WorkflowLibrary)
-            .FirstOrDefault()?.Message;
-        if (validationError is not null)
-        {
-            throw new InvalidOperationException(validationError);
-        }
-
-        IProviderEventAdapter providerEventAdapter = new CopilotEventAdapter();
-        CopilotTurnExecutionState state = new(command);
-        using CancellationTokenSource runCancellation =
-            CancellationTokenSource.CreateLinkedTokenSource(cancellationToken);
-
-        try
-        {
-            await using CopilotAgentBundle bundle = await CopilotAgentBundle.CreateAsync(
-                command,
-                (agent, request, invocation) => _approvalCoordinator.RequestApprovalAsync(
-                    command,
-                    agent,
-                    request,
-                    invocation,
-                    state.ToolNamesByCallId,
-                    activity => EmitActivityAsync(command, state, activity, onEvent),
-                    onApproval,
-                    runCancellation.Token),
-                (agent, request, invocation) => _userInputCoordinator.RequestUserInputAsync(
-                    command,
-                    agent,
-                    request,
-                    invocation,
-                    onUserInput,
-                    runCancellation.Token),
-                (agent, sessionEvent) =>
-                {
-                    if (providerEventAdapter.TryAdapt(sessionEvent) is { } providerEvent)
-                    {
-                        state.ObserveSessionEvent(agent, providerEvent);
-                    }
-
-                    if (sessionEvent is McpOauthRequiredEvent mcpOauthRequired)
-                    {
-                        state.EnqueuePendingMcpOauthRequest(
-                            _mcpOAuthCoordinator.BuildMcpOauthRequiredEvent(command, agent, mcpOauthRequired));
-                    }
-
-                    if (sessionEvent is ExitPlanModeRequestedEvent exitPlanModeRequested)
-                    {
-                        _exitPlanModeCoordinator.RecordExitPlanModeRequest(command, agent, exitPlanModeRequested);
-                        runCancellation.Cancel();
-                    }
-                },
-                runCancellation.Token);
-            ConfigureHookLifecycleEventSuppression(state, bundle);
-            Workflow workflow = BuildWorkflowForCommand(command, bundle.Agents, _workflowRunner);
-            List<ChatMessage> inputMessages = command.Messages.Select(WorkflowTranscriptProjector.ToChatMessage).ToList();
-            WorkflowTranscriptProjector.AttachMessageMode(inputMessages, command.MessageMode);
-
-            using FileSystemJsonCheckpointStore? checkpointStore = CreateCheckpointStore(command);
-            CheckpointManager? checkpointManager = checkpointStore is not null
-                ? CheckpointManager.CreateJson(checkpointStore)
-                : null;
-
-            await using StreamingRun run = await OpenWorkflowRunAsync(
-                command,
-                workflow,
-                inputMessages,
-                checkpointManager).ConfigureAwait(false);
-            await run.TrySendMessageAsync(new TurnToken(emitEvents: true)).ConfigureAwait(false);
-
-            await foreach (WorkflowEvent evt in run.WatchStreamAsync(runCancellation.Token).ConfigureAwait(false))
-            {
-                if (evt is RequestInfoEvent requestInfo
-                    && await TryHandleRequestPortRequestAsync(
-                        command,
-                        requestInfo,
-                        run,
-                        onUserInput,
-                        runCancellation.Token).ConfigureAwait(false))
-                {
-                    continue;
-                }
-
-                bool shouldEndTurn = await HandleWorkflowEventAsync(command, evt, inputMessages, state, onDelta, onEvent)
-                    .ConfigureAwait(false);
-                await EmitPendingEventsAsync(state, onEvent).ConfigureAwait(false);
-                await EmitPendingMcpOauthRequestsAsync(state, onMcpOAuthRequired).ConfigureAwait(false);
-                if (shouldEndTurn)
-                {
-                    break;
-                }
-            }
-
-            await EmitPendingEventsAsync(state, onEvent).ConfigureAwait(false);
-            await EmitPendingMcpOauthRequestsAsync(state, onMcpOAuthRequired).ConfigureAwait(false);
-            return state.FinalizeCompletedMessages();
-        }
-        catch (OperationCanceledException) when (runCancellation.IsCancellationRequested && !cancellationToken.IsCancellationRequested)
-        {
-            await EmitPendingEventsAsync(state, onEvent).ConfigureAwait(false);
-            await EmitPendingMcpOauthRequestsAsync(state, onMcpOAuthRequired).ConfigureAwait(false);
-            ExitPlanModeRequestedEventDto? exitPlanModeEvent =
-                _exitPlanModeCoordinator.ConsumePendingRequest(command.RequestId);
-            if (exitPlanModeEvent is null || !state.HasPendingExitPlanModeRequest)
-            {
-                throw;
-            }
-
-            await onExitPlanMode(exitPlanModeEvent).ConfigureAwait(false);
-            return state.FinalizeCompletedMessages();
-        }
-        finally
-        {
-            _approvalCoordinator.ClearRequestApprovals(command.RequestId);
-        }
-    }
-
-    internal static Workflow BuildWorkflowForCommand(
         RunTurnCommandDto command,
         IReadOnlyList<AIAgent> agents,
         WorkflowRunner? workflowRunner = null)
     {
-        ArgumentNullException.ThrowIfNull(command);
+        return AgentWorkflowTurnRunner.BuildWorkflowForCommand(command, agents, workflowRunner);
-        ArgumentNullException.ThrowIfNull(agents);
-
-        return NormalizeOrchestrationMode(command.Workflow.Settings.OrchestrationMode) switch
-        {
-            "handoff" => CopilotAgentBundle.CreateHandoffWorkflow(command.Workflow, agents),
-            "group-chat" => CopilotAgentBundle.CreateGroupChatWorkflow(command.Workflow, agents),
-            _ => (workflowRunner ?? new WorkflowRunner()).BuildWorkflow(command.Workflow, agents, command.WorkflowLibrary),
-        };
     }
 
-    internal static FileSystemJsonCheckpointStore? CreateCheckpointStore(RunTurnCommandDto command)
+    internal new static FileSystemJsonCheckpointStore? CreateCheckpointStore(RunTurnCommandDto command)
     {
-        if (!ShouldEnableWorkflowCheckpointing(command))
+        return AgentWorkflowTurnRunner.CreateCheckpointStore(command);
-        {
-            return null;
-        }
-
-        DirectoryInfo checkpointDirectory = new(GetCheckpointStorePath(command));
-        return new FileSystemJsonCheckpointStore(checkpointDirectory);
     }
 
-    internal static bool ShouldEnableWorkflowCheckpointing(RunTurnCommandDto command)
+    internal new static bool ShouldEnableWorkflowCheckpointing(RunTurnCommandDto command)
     {
-        ArgumentNullException.ThrowIfNull(command);
+        return AgentWorkflowTurnRunner.ShouldEnableWorkflowCheckpointing(command);
-        return command.Workflow.Settings.Checkpointing.Enabled;
     }
 
-    internal static string GetCheckpointStorePath(RunTurnCommandDto command)
+    internal new static string GetCheckpointStorePath(RunTurnCommandDto command)
     {
-        ArgumentNullException.ThrowIfNull(command);
+        return AgentWorkflowTurnRunner.GetCheckpointStorePath(command);
-
-        if (!string.IsNullOrWhiteSpace(command.ResumeFromCheckpoint?.StorePath))
-        {
-            return command.ResumeFromCheckpoint.StorePath;
-        }
-
-        string localAppData = Environment.GetFolderPath(Environment.SpecialFolder.LocalApplicationData);
-        return Path.Combine(localAppData, "Aryx", "workflow-checkpoints", command.SessionId, command.RequestId);
     }
 
-    private static string? NormalizeOrchestrationMode(string? value)
+    internal new static InProcessExecutionEnvironment CreateExecutionEnvironment(
-    {
-        return string.IsNullOrWhiteSpace(value) ? null : value.Trim().ToLowerInvariant();
-    }
-
-    private static ValueTask<StreamingRun> OpenWorkflowRunAsync(
-        RunTurnCommandDto command,
-        Workflow workflow,
-        IReadOnlyList<ChatMessage> inputMessages,
-        CheckpointManager? checkpointManager)
-    {
-        InProcessExecutionEnvironment environment = CreateExecutionEnvironment(command, checkpointManager);
-        if (checkpointManager is not null && command.ResumeFromCheckpoint is { } resumeFromCheckpoint)
-        {
-            return environment.ResumeStreamingAsync(
-                workflow,
-                new CheckpointInfo(resumeFromCheckpoint.WorkflowSessionId, resumeFromCheckpoint.CheckpointId));
-        }
-
-        return environment.RunStreamingAsync(workflow, inputMessages.ToList(), command.RequestId);
-    }
-
-    internal static InProcessExecutionEnvironment CreateExecutionEnvironment(
         RunTurnCommandDto command,
         CheckpointManager? checkpointManager)
     {
-        ArgumentNullException.ThrowIfNull(command);
+        return AgentWorkflowTurnRunner.CreateExecutionEnvironment(command, checkpointManager);
-
-        string executionMode = command.Workflow.Settings.ExecutionMode?.Trim() ?? "off-thread";
-        InProcessExecutionEnvironment environment = string.Equals(
-            executionMode,
-            "lockstep",
-            StringComparison.OrdinalIgnoreCase)
-            ? InProcessExecution.Lockstep
-            : InProcessExecution.OffThread;
-
-        return checkpointManager is null ? environment : environment.WithCheckpointing(checkpointManager);
     }
 
     internal static void ConfigureHookLifecycleEventSuppression(
         CopilotTurnExecutionState state,
         CopilotAgentBundle bundle)
     {
-        ArgumentNullException.ThrowIfNull(state);
+        AgentWorkflowTurnRunner.ConfigureHookLifecycleEventSuppression(state, bundle);
-        ArgumentNullException.ThrowIfNull(bundle);
-
-        state.SuppressHookLifecycleEvents = !bundle.HasConfiguredHooks;
     }
 
-    private static async Task EmitPendingEventsAsync(
+    internal new static UserInputRequest CreateRequestPortUserInputRequest(
-        CopilotTurnExecutionState state,
+        AgentWorkflowTurnRunner.WorkflowRequestPortMetadata metadata,
-        Func<SidecarEventDto, Task> onEvent)
+        RequestInfoEvent requestInfo)
     {
-        foreach (SidecarEventDto pendingEvent in state.DrainPendingEvents())
+        return AgentWorkflowTurnRunner.CreateRequestPortUserInputRequest(metadata, requestInfo);
-        {
-            await onEvent(pendingEvent).ConfigureAwait(false);
-        }
     }
 
-    private static async Task EmitPendingMcpOauthRequestsAsync(
+    internal new static object CoerceRequestPortResponse(string responseType, string? answer)
-        CopilotTurnExecutionState state,
-        Func<McpOauthRequiredEventDto, Task> onMcpOAuthRequired)
     {
-        foreach (McpOauthRequiredEventDto request in state.DrainPendingMcpOauthRequests())
+        return AgentWorkflowTurnRunner.CoerceRequestPortResponse(responseType, answer);
-        {
-            await onMcpOAuthRequired(request).ConfigureAwait(false);
-        }
     }
 
-    public Task ResolveApprovalAsync(
+    private static Task<bool> HandleWorkflowEventAsync(
-        ResolveApprovalCommandDto command,
-        CancellationToken cancellationToken)
-    {
-        return _approvalCoordinator.ResolveApprovalAsync(command, cancellationToken);
-    }
-
-    public Task ResolveUserInputAsync(
-        ResolveUserInputCommandDto command,
-        CancellationToken cancellationToken)
-    {
-        return _userInputCoordinator.ResolveUserInputAsync(command, cancellationToken);
-    }
-
-    private async Task<bool> TryHandleRequestPortRequestAsync(
-        RunTurnCommandDto command,
-        RequestInfoEvent requestInfo,
-        StreamingRun run,
-        Func<UserInputRequestedEventDto, Task> onUserInput,
-        CancellationToken cancellationToken)
-    {
-        if (!TryResolveRequestPortMetadata(command.Workflow, requestInfo, out WorkflowRequestPortMetadata? metadata))
-        {
-            return false;
-        }
-
-        UserInputRequest userInputRequest = CreateRequestPortUserInputRequest(metadata!, requestInfo);
-        UserInputResponse response = await _userInputCoordinator.RequestUserInputAsync(
-            command,
-            userInputRequest,
-            onUserInput,
-            cancellationToken).ConfigureAwait(false);
-
-        object coercedResponse = CoerceRequestPortResponse(metadata!.ResponseType, response.Answer);
-        await run.SendResponseAsync(requestInfo.Request.CreateResponse(coercedResponse)).ConfigureAwait(false);
-        return true;
-    }
-
-    private static async Task<bool> HandleWorkflowEventAsync(
         RunTurnCommandDto command,
         WorkflowEvent evt,
         IReadOnlyList<ChatMessage> inputMessages,
@@ -314,469 +74,13 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
         Func<TurnDeltaEventDto, Task> onDelta,
         Func<SidecarEventDto, Task> onEvent)
     {
-        if (evt is ExecutorInvokedEvent invoked)
+        return AgentWorkflowTurnRunner.HandleWorkflowEventAsync(
-        {
-            if (AgentIdentityResolver.TryResolveKnownAgentIdentity(
-                command.Workflow,
-                invoked.ExecutorId,
-                out AgentIdentity invokedAgent))
-            {
-                TraceHandoff(command, $"Executor invoked: {invoked.ExecutorId} -> {invokedAgent.AgentName} ({invokedAgent.AgentId}).");
-                await state.EmitThinkingIfNeeded(invokedAgent, onEvent).ConfigureAwait(false);
-            }
-            else
-            {
-                TraceHandoff(command, $"Executor invoked without a known agent match: {invoked.ExecutorId}.");
-            }
-
-            return false;
-        }
-
-        if (evt is RequestInfoEvent requestInfo)
-        {
-            AgentActivityEventDto? activity = WorkflowRequestInfoInterpreter.TryCreateActivityFromRequest(
-                command,
-                requestInfo,
-                state.ActiveAgent,
-                state.ToolNamesByCallId);
-
-            if (activity is null)
-            {
-                bool requiresBoundary = WorkflowRequestInfoInterpreter.RequiresUserInputTurnBoundary(command, requestInfo);
-                TraceHandoff(
-                    command,
-                    $"Request info produced no activity for data type '{requestInfo.Request.Data.TypeId}'. Requires boundary: {requiresBoundary}.");
-                return requiresBoundary;
-            }
-
-            await EmitActivityAsync(command, state, activity, onEvent).ConfigureAwait(false);
-            return false;
-        }
-
-        if (TryCreateWorkflowCheckpointSavedEvent(command, evt, out WorkflowCheckpointSavedEventDto? checkpointSaved))
-        {
-            await onEvent(checkpointSaved).ConfigureAwait(false);
-            return false;
-        }
-
-        if (TryCreateWorkflowDiagnosticEvent(command, evt, state, out WorkflowDiagnosticEventDto? diagnostic))
-        {
-            await onEvent(diagnostic).ConfigureAwait(false);
-            return false;
-        }
-
-        if (evt is AgentResponseUpdateEvent update)
-        {
-            await HandleAgentResponseUpdateAsync(command, update, state, onDelta, onEvent).ConfigureAwait(false);
-            return false;
-        }
-
-        if (evt is ExecutorCompletedEvent completed)
-        {
-            if (AgentIdentityResolver.TryResolveObservedAgentIdentity(
-                command.Workflow,
-                completed.ExecutorId,
-                state.ActiveAgent,
-                out AgentIdentity completedAgent))
-            {
-                TraceHandoff(command, $"Executor completed: {completed.ExecutorId} -> {completedAgent.AgentName} ({completedAgent.AgentId}).");
-                state.QueueCompletedActivity(completedAgent);
-                state.ClearActiveAgentIfMatching(completedAgent);
-            }
-            else
-            {
-                TraceHandoff(command, $"Executor completed without a known agent match: {completed.ExecutorId}.");
-            }
-
-            return false;
-        }
-
-        if (evt is WorkflowOutputEvent outputEvent)
-        {
-            List<ChatMessage> allMessages = outputEvent.As<List<ChatMessage>>() ?? [];
-            state.UpdateCompletedMessages(allMessages, inputMessages);
-        }
-
-        return false;
-    }
-
-    internal static UserInputRequest CreateRequestPortUserInputRequest(
-        WorkflowRequestPortMetadata metadata,
-        RequestInfoEvent requestInfo)
-    {
-        ArgumentNullException.ThrowIfNull(metadata);
-        ArgumentNullException.ThrowIfNull(requestInfo);
-
-        string question = metadata.Prompt
-            ?? BuildRequestPortFallbackQuestion(metadata, requestInfo);
-
-        bool expectsBoolean = IsBooleanResponseType(metadata.ResponseType);
-        return new UserInputRequest
-        {
-            Question = question,
-            Choices = expectsBoolean ? ["true", "false"] : null,
-            AllowFreeform = true,
-        };
-    }
-
-    internal static object CoerceRequestPortResponse(string responseType, string? answer)
-    {
-        string normalizedResponseType = responseType.Trim();
-        string trimmedAnswer = answer?.Trim() ?? string.Empty;
-
-        if (IsStringResponseType(normalizedResponseType))
-        {
-            return trimmedAnswer;
-        }
-
-        if (IsBooleanResponseType(normalizedResponseType))
-        {
-            return trimmedAnswer.ToLowerInvariant() switch
-            {
-                "true" or "t" or "yes" or "y" or "1" => true,
-                "false" or "f" or "no" or "n" or "0" => false,
-                _ => throw new InvalidOperationException(
-                    $"Request port response type \"{responseType}\" requires a boolean answer."),
-            };
-        }
-
-        if (IsNumericResponseType(normalizedResponseType))
-        {
-            if (double.TryParse(trimmedAnswer, NumberStyles.Float, CultureInfo.InvariantCulture, out double numeric))
-            {
-                return numeric;
-            }
-
-            throw new InvalidOperationException(
-                $"Request port response type \"{responseType}\" requires a numeric answer.");
-        }
-
-        if (IsJsonResponseType(normalizedResponseType))
-        {
-            try
-            {
-                return JsonDocument.Parse(trimmedAnswer).RootElement.Clone();
-            }
-            catch (JsonException ex)
-            {
-                throw new InvalidOperationException(
-                    $"Request port response type \"{responseType}\" requires a valid JSON answer.",
-                    ex);
-            }
-        }
-
-        return trimmedAnswer;
-    }
-
-    private static async Task HandleAgentResponseUpdateAsync(
-        RunTurnCommandDto command,
-        AgentResponseUpdateEvent update,
-        CopilotTurnExecutionState state,
-        Func<TurnDeltaEventDto, Task> onDelta,
-        Func<SidecarEventDto, Task> onEvent)
-    {
-        AgentIdentity? updateAgent = null;
-        string authorName = update.ExecutorId;
-        string[] handoffFunctionCalls = update.Update.Contents
-            .OfType<FunctionCallContent>()
-            .Select(content => content.Name)
-            .Where(IsHandoffFunctionName)
-            .Distinct(StringComparer.Ordinal)
-            .ToArray();
-        if (state.TryResolveObservedAgentForMessage(update.Update.MessageId, out AgentIdentity observedMessageAgent))
-        {
-            updateAgent = observedMessageAgent;
-            authorName = observedMessageAgent.AgentName;
-        }
-        else if (AgentIdentityResolver.TryResolveObservedAgentIdentity(
-            command.Workflow,
-            update.ExecutorId,
-            state.ActiveAgent,
-            out AgentIdentity resolvedUpdateAgent))
-        {
-            updateAgent = resolvedUpdateAgent;
-            authorName = resolvedUpdateAgent.AgentName;
-        }
-        else if (state.ActiveAgent is AgentIdentity activeAgent)
-        {
-            updateAgent = activeAgent;
-            authorName = activeAgent.AgentName;
-            TraceHandoff(
-                command,
-                $"Agent response update fell back to active agent {activeAgent.AgentName} ({activeAgent.AgentId}) for executor '{update.ExecutorId}' and message '{update.Update.MessageId ?? "<none>"}'.");
-        }
-
-        if (updateAgent.HasValue)
-        {
-            if (handoffFunctionCalls.Length > 0)
-            {
-                TraceHandoff(
-                    command,
-                    $"Agent response update from {updateAgent.Value.AgentName} ({updateAgent.Value.AgentId}) requested handoff via {string.Join(", ", handoffFunctionCalls)}.");
-            }
-
-            await state.EmitThinkingIfNeeded(updateAgent.Value, onEvent).ConfigureAwait(false);
-        }
-        else if (!string.IsNullOrEmpty(update.Update.Text) || handoffFunctionCalls.Length > 0)
-        {
-            TraceHandoff(
-                command,
-                $"Agent response update could not resolve agent for executor '{update.ExecutorId}' and message '{update.Update.MessageId ?? "<none>"}'.");
-        }
-
-        if (string.IsNullOrEmpty(update.Update.Text))
-        {
-            return;
-        }
-
-        string messageId = state.CreateMessageId(update.Update.MessageId);
-        (string _, string currentAuthorName, string currentContent) = state.AppendDelta(
-            messageId,
-            authorName,
-            update.Update.Text);
-
-        await onDelta(new TurnDeltaEventDto
-        {
-            Type = "turn-delta",
-            RequestId = command.RequestId,
-            SessionId = command.SessionId,
-            MessageId = messageId,
-            AuthorName = currentAuthorName,
-            ContentDelta = update.Update.Text,
-            Content = currentContent,
-        }).ConfigureAwait(false);
-    }
-
-    private static async Task EmitActivityAsync(
-        RunTurnCommandDto command,
-        CopilotTurnExecutionState state,
-        AgentActivityEventDto activity,
-        Func<SidecarEventDto, Task> onEvent)
-    {
-        state.ApplyEvent(activity);
-        TraceHandoff(
             command,
-            $"Activity emitted: {activity.ActivityType} -> {activity.AgentName ?? activity.AgentId ?? "<unknown>"}.");
+            evt,
-        await onEvent(activity).ConfigureAwait(false);
+            inputMessages,
-
+            state,
-        if (string.Equals(activity.ActivityType, "handoff", StringComparison.Ordinal)
+            CopilotTranscriptProjector.Instance,
-            && !string.IsNullOrWhiteSpace(activity.AgentId)
+            onDelta,
-            && !string.IsNullOrWhiteSpace(activity.AgentName))
+            onEvent);
-        {
-            TraceHandoff(
-                command,
-                $"Promoting handoff target to thinking: {activity.AgentName} ({activity.AgentId}).");
-            await state.EmitThinkingIfNeeded(
-                new AgentIdentity(activity.AgentId, activity.AgentName),
-                onEvent).ConfigureAwait(false);
-        }
-    }
-
-    internal static bool TryCreateWorkflowCheckpointSavedEvent(
-        RunTurnCommandDto command,
-        WorkflowEvent evt,
-        out WorkflowCheckpointSavedEventDto checkpointSaved)
-    {
-        checkpointSaved = default!;
-
-        if (!ShouldEnableWorkflowCheckpointing(command)
-            || evt is not SuperStepCompletedEvent superStepCompleted
-            || superStepCompleted.CompletionInfo?.Checkpoint is not CheckpointInfo checkpoint)
-        {
-            return false;
-        }
-
-        checkpointSaved = new WorkflowCheckpointSavedEventDto
-        {
-            Type = "workflow-checkpoint-saved",
-            RequestId = command.RequestId,
-            SessionId = command.SessionId,
-            WorkflowSessionId = checkpoint.SessionId,
-            CheckpointId = checkpoint.CheckpointId,
-            StorePath = GetCheckpointStorePath(command),
-            StepNumber = superStepCompleted.StepNumber,
-        };
-        return true;
-    }
-
-    private static bool TryCreateWorkflowDiagnosticEvent(
-        RunTurnCommandDto command,
-        WorkflowEvent evt,
-        CopilotTurnExecutionState state,
-        out WorkflowDiagnosticEventDto diagnostic)
-    {
-        diagnostic = default!;
-
-        switch (evt)
-        {
-            case ExecutorFailedEvent executorFailed:
-            {
-                AgentIdentity? agent = AgentIdentityResolver.TryResolveObservedAgentIdentity(
-                    command.Workflow,
-                    executorFailed.ExecutorId,
-                    state.ActiveAgent,
-                    out AgentIdentity resolvedAgent)
-                    ? resolvedAgent
-                    : null;
-                Exception? exception = executorFailed.Data;
-                diagnostic = new WorkflowDiagnosticEventDto
-                {
-                    Type = "workflow-diagnostic",
-                    RequestId = command.RequestId,
-                    SessionId = command.SessionId,
-                    Severity = "error",
-                    DiagnosticKind = "executor-failed",
-                    Message = ResolveDiagnosticMessage(exception, "Executor failed."),
-                    AgentId = agent?.AgentId,
-                    AgentName = agent?.AgentName,
-                    ExecutorId = executorFailed.ExecutorId,
-                    ExceptionType = exception?.GetBaseException().GetType().Name,
-                };
-                return true;
-            }
-            case WorkflowWarningEvent workflowWarning:
-                diagnostic = new WorkflowDiagnosticEventDto
-                {
-                    Type = "workflow-diagnostic",
-                    RequestId = command.RequestId,
-                    SessionId = command.SessionId,
-                    Severity = "warning",
-                    DiagnosticKind = workflowWarning is SubworkflowWarningEvent
-                        ? "subworkflow-warning"
-                        : "workflow-warning",
-                    Message = ResolveDiagnosticMessage(workflowWarning.Data as string, "Workflow warning."),
-                    SubworkflowId = workflowWarning is SubworkflowWarningEvent subworkflowWarning
-                        ? subworkflowWarning.SubWorkflowId
-                        : null,
-                };
-                return true;
-            case WorkflowErrorEvent workflowError:
-            {
-                Exception? exception = workflowError.Exception;
-                diagnostic = new WorkflowDiagnosticEventDto
-                {
-                    Type = "workflow-diagnostic",
-                    RequestId = command.RequestId,
-                    SessionId = command.SessionId,
-                    Severity = "error",
-                    DiagnosticKind = workflowError is SubworkflowErrorEvent
-                        ? "subworkflow-error"
-                        : "workflow-error",
-                    Message = ResolveDiagnosticMessage(exception, "Workflow failed."),
-                    SubworkflowId = workflowError is SubworkflowErrorEvent subworkflowError
-                        ? subworkflowError.SubworkflowId
-                        : null,
-                    ExceptionType = exception?.GetBaseException().GetType().Name,
-                };
-                return true;
-            }
-            default:
-                return false;
-        }
-    }
-
-    private static bool TryResolveRequestPortMetadata(
-        WorkflowDefinitionDto? workflow,
-        RequestInfoEvent requestInfo,
-        out WorkflowRequestPortMetadata? metadata)
-    {
-        metadata = null;
-        if (workflow is null)
-        {
-            return false;
-        }
-
-        string portId = requestInfo.Request.PortInfo.PortId;
-        WorkflowNodeDto? node = workflow.Graph.Nodes.FirstOrDefault(candidate =>
-            string.Equals(candidate.Kind, "request-port", StringComparison.OrdinalIgnoreCase)
-            && string.Equals(candidate.Config.PortId, portId, StringComparison.OrdinalIgnoreCase));
-
-        if (node is null)
-        {
-            return false;
-        }
-
-        metadata = new WorkflowRequestPortMetadata(
-            node.Id,
-            string.IsNullOrWhiteSpace(node.Label) ? node.Id : node.Label,
-            node.Config.PortId ?? portId,
-            node.Config.RequestType ?? string.Empty,
-            node.Config.ResponseType ?? string.Empty,
-            string.IsNullOrWhiteSpace(node.Config.Prompt) ? null : node.Config.Prompt.Trim());
-        return true;
-    }
-
-    private static string BuildRequestPortFallbackQuestion(
-        WorkflowRequestPortMetadata metadata,
-        RequestInfoEvent requestInfo)
-    {
-        if (requestInfo.Request.Data.Is<WorkflowRequestPortPromptRequest>(out WorkflowRequestPortPromptRequest? promptRequest))
-        {
-            string baseQuestion = $"Provide a {metadata.ResponseType} response for \"{promptRequest.NodeLabel}\".";
-            if (!string.IsNullOrWhiteSpace(promptRequest.InputSummary))
-            {
-                return $"{baseQuestion} Current input: {promptRequest.InputSummary}";
-            }
-
-            return baseQuestion;
-        }
-
-        return $"Provide a {metadata.ResponseType} response for request port \"{metadata.NodeLabel}\" ({metadata.PortId}).";
-    }
-
-    private static bool IsStringResponseType(string responseType)
-        => string.Equals(responseType, "string", StringComparison.OrdinalIgnoreCase)
-           || string.Equals(responseType, "text", StringComparison.OrdinalIgnoreCase);
-
-    private static bool IsBooleanResponseType(string responseType)
-        => string.Equals(responseType, "bool", StringComparison.OrdinalIgnoreCase)
-           || string.Equals(responseType, "boolean", StringComparison.OrdinalIgnoreCase);
-
-    private static bool IsNumericResponseType(string responseType)
-        => string.Equals(responseType, "number", StringComparison.OrdinalIgnoreCase)
-           || string.Equals(responseType, "int", StringComparison.OrdinalIgnoreCase)
-           || string.Equals(responseType, "float", StringComparison.OrdinalIgnoreCase)
-           || string.Equals(responseType, "double", StringComparison.OrdinalIgnoreCase)
-           || string.Equals(responseType, "decimal", StringComparison.OrdinalIgnoreCase);
-
-    private static bool IsJsonResponseType(string responseType)
-        => string.Equals(responseType, "json", StringComparison.OrdinalIgnoreCase)
-           || string.Equals(responseType, "object", StringComparison.OrdinalIgnoreCase)
-           || string.Equals(responseType, "array", StringComparison.OrdinalIgnoreCase);
-
-    internal sealed record WorkflowRequestPortMetadata(
-        string NodeId,
-        string NodeLabel,
-        string PortId,
-        string RequestType,
-        string ResponseType,
-        string? Prompt);
-
-    private static string ResolveDiagnosticMessage(Exception? exception, string fallback)
-    {
-        return ResolveDiagnosticMessage(
-            exception?.GetBaseException().Message,
-            fallback);
-    }
-
-    private static string ResolveDiagnosticMessage(string? message, string fallback)
-    {
-        return string.IsNullOrWhiteSpace(message) ? fallback : message;
-    }
-
-    private static bool IsHandoffFunctionName(string? candidate)
-    {
-        return !string.IsNullOrWhiteSpace(candidate)
-            && candidate.StartsWith(HandoffFunctionPrefix, StringComparison.Ordinal);
-    }
-
-    private static void TraceHandoff(RunTurnCommandDto command, string message)
-    {
-        if (!command.Workflow.IsOrchestrationMode("handoff"))
-        {
-            return;
-        }
-
-        Console.Error.WriteLine($"[aryx handoff] {message}");
     }
 }

sidecar/src/Aryx.AgentHost/Services/TurnExecutionState.cs

@@ -0,0 +1,674 @@
+using System.Collections.Concurrent;
+using Aryx.AgentHost.Contracts;
+using Microsoft.Extensions.AI;
+
+namespace Aryx.AgentHost.Services;
+
+internal class TurnExecutionState
+{
+    private readonly RunTurnCommandDto _command;
+    private readonly HashSet<string> _startedAgents = new(StringComparer.OrdinalIgnoreCase);
+    private readonly HashSet<string> _reclassifiedMessageIds = new(StringComparer.Ordinal);
+    private readonly ConcurrentQueue<SidecarEventDto> _pendingEvents = new();
+    private readonly ConcurrentQueue<McpOauthRequiredEventDto> _pendingMcpOauthRequests = new();
+    private readonly ConcurrentDictionary<string, AgentIdentity> _observedAgentsByMessageId = new(StringComparer.Ordinal);
+    private readonly StreamingTranscriptBuffer _transcriptBuffer = new();
+    private int _fallbackMessageIndex;
+    private string? _lastObservedMessageId;
+
+    public TurnExecutionState(RunTurnCommandDto command)
+    {
+        _command = command;
+    }
+
+    public ConcurrentDictionary<string, string> ToolNamesByCallId { get; } = new(StringComparer.Ordinal);
+
+    public AgentIdentity? ActiveAgent { get; private set; }
+
+    public List<ChatMessageDto> CompletedMessages { get; private set; } = [];
+
+    public bool HasPendingExitPlanModeRequest { get; private set; }
+
+    public bool SuppressHookLifecycleEvents { get; set; }
+
+    public async Task EmitThinkingIfNeeded(
+        AgentIdentity agent,
+        Func<SidecarEventDto, Task> onEvent)
+    {
+        AgentActivityEventDto? thinkingActivity = CreateThinkingActivityIfNeeded(agent);
+        if (thinkingActivity is null)
+        {
+            return;
+        }
+
+        await onEvent(thinkingActivity).ConfigureAwait(false);
+    }
+
+    public void QueueThinkingIfNeeded(AgentIdentity agent)
+    {
+        AgentActivityEventDto? thinkingActivity = CreateThinkingActivityIfNeeded(agent);
+        if (thinkingActivity is not null)
+        {
+            _pendingEvents.Enqueue(thinkingActivity);
+        }
+    }
+
+    public void QueueCompletedActivity(AgentIdentity agent)
+    {
+        _pendingEvents.Enqueue(CreateCompletedActivity(agent));
+    }
+
+    public void ApplyEvent(SidecarEventDto evt)
+    {
+        if (evt is AgentActivityEventDto activity
+            && string.Equals(activity.ActivityType, "handoff", StringComparison.Ordinal)
+            && !string.IsNullOrWhiteSpace(activity.AgentId)
+            && !string.IsNullOrWhiteSpace(activity.AgentName))
+        {
+            ActiveAgent = new AgentIdentity(activity.AgentId, activity.AgentName);
+        }
+    }
+
+    public void ObserveSessionEvent(WorkflowNodeDto agentDefinition, ProviderSessionEvent sessionEvent)
+    {
+        AgentIdentity agent = AgentIdentityResolver.ResolveAgentIdentity(
+            _command.Workflow,
+            agentDefinition.GetAgentId(),
+            agentDefinition.GetAgentName());
+
+        switch (sessionEvent)
+        {
+            case ProviderAssistantMessageDeltaEvent messageDelta:
+                RecordObservedAgentForMessage(agent, messageDelta.MessageId);
+                QueueThinkingIfNeeded(agent);
+                break;
+            case ProviderAssistantMessageEvent assistantMessage:
+                RecordObservedAgentForMessage(agent, assistantMessage.MessageId);
+                QueueThinkingIfNeeded(agent);
+                if (assistantMessage.HasToolRequests)
+                {
+                    QueueMessageReclassifiedIfNeeded(assistantMessage.MessageId);
+                }
+                break;
+            case ProviderToolExecutionStartEvent toolExecutionStart:
+                string toolCallId = toolExecutionStart.ToolCallId;
+                string toolName = toolExecutionStart.ToolName;
+                ToolNamesByCallId[toolCallId] = toolName;
+                ActiveAgent = agent;
+                AgentActivityEventDto? toolActivity = CreateToolCallingActivity(
+                    agent, toolName, toolCallId, toolExecutionStart.ToolArguments);
+                if (toolActivity is not null)
+                {
+                    _pendingEvents.Enqueue(toolActivity);
+                }
+
+                QueueMessageReclassifiedIfNeeded(_lastObservedMessageId);
+                break;
+            case ProviderAssistantIntentEvent intentEvent:
+                ActiveAgent = agent;
+                QueueThinkingIfNeeded(agent);
+                AssistantIntentEventDto? assistantIntent = CreateAssistantIntentEvent(agent, intentEvent.Intent);
+                if (assistantIntent is not null)
+                {
+                    _pendingEvents.Enqueue(assistantIntent);
+                }
+                break;
+            case ProviderAssistantReasoningDeltaEvent reasoningDelta:
+                ActiveAgent = agent;
+                QueueThinkingIfNeeded(agent);
+                ReasoningDeltaEventDto? reasoningDeltaEvent = CreateReasoningDeltaEvent(
+                    agent,
+                    reasoningDelta.ReasoningId,
+                    reasoningDelta.DeltaContent);
+                if (reasoningDeltaEvent is not null)
+                {
+                    _pendingEvents.Enqueue(reasoningDeltaEvent);
+                }
+                break;
+            case ProviderSubagentStartedEvent started:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateSubagentStartedEvent(agent, started));
+                break;
+            case ProviderSubagentCompletedEvent completed:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateSubagentCompletedEvent(agent, completed));
+                break;
+            case ProviderSubagentFailedEvent failed:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateSubagentFailedEvent(agent, failed));
+                break;
+            case ProviderSubagentSelectedEvent selected:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateSubagentSelectedEvent(agent, selected));
+                break;
+            case ProviderSubagentDeselectedEvent:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateSubagentDeselectedEvent(agent));
+                break;
+            case ProviderSkillInvokedEvent skillInvoked:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateSkillInvokedEvent(agent, skillInvoked));
+                break;
+            case ProviderHookStartEvent hookStart:
+                ActiveAgent = agent;
+                if (!SuppressHookLifecycleEvents)
+                {
+                    _pendingEvents.Enqueue(CreateHookLifecycleEvent(
+                        agent,
+                        "start",
+                        hookStart.HookInvocationId,
+                        hookStart.HookType,
+                        input: hookStart.Input));
+                }
+                break;
+            case ProviderHookEndEvent hookEnd:
+                ActiveAgent = agent;
+                if (!SuppressHookLifecycleEvents)
+                {
+                    _pendingEvents.Enqueue(CreateHookLifecycleEvent(
+                        agent,
+                        "end",
+                        hookEnd.HookInvocationId,
+                        hookEnd.HookType,
+                        success: hookEnd.Success,
+                        output: hookEnd.Output,
+                        error: hookEnd.Error));
+                }
+                break;
+            case ProviderAssistantUsageEvent assistantUsage:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateAssistantUsageEvent(agent, assistantUsage));
+                break;
+            case ProviderSessionUsageEvent usageInfo:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateUsageEvent(agent, usageInfo));
+                break;
+            case ProviderSessionCompactionStartEvent compactionStart:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateCompactionStartEvent(agent, compactionStart));
+                break;
+            case ProviderSessionCompactionCompleteEvent compactionComplete:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreateCompactionCompleteEvent(agent, compactionComplete));
+                break;
+            case ProviderPendingMessagesModifiedEvent:
+                ActiveAgent = agent;
+                _pendingEvents.Enqueue(CreatePendingMessagesModifiedEvent(agent));
+                break;
+            case ProviderMcpOauthRequiredEvent:
+                ActiveAgent = agent;
+                break;
+            case ProviderExitPlanModeRequestedEvent:
+                HasPendingExitPlanModeRequest = true;
+                ActiveAgent = agent;
+                break;
+        }
+    }
+
+    public IReadOnlyList<SidecarEventDto> DrainPendingEvents()
+    {
+        List<SidecarEventDto> pending = [];
+        while (_pendingEvents.TryDequeue(out SidecarEventDto? pendingEvent))
+        {
+            pending.Add(pendingEvent);
+        }
+
+        return pending;
+    }
+
+    public void EnqueuePendingMcpOauthRequest(McpOauthRequiredEventDto request)
+    {
+        ArgumentNullException.ThrowIfNull(request);
+        _pendingMcpOauthRequests.Enqueue(request);
+    }
+
+    public IReadOnlyList<McpOauthRequiredEventDto> DrainPendingMcpOauthRequests()
+    {
+        List<McpOauthRequiredEventDto> pending = [];
+        while (_pendingMcpOauthRequests.TryDequeue(out McpOauthRequiredEventDto? request))
+        {
+            pending.Add(request);
+        }
+
+        return pending;
+    }
+
+    public bool TryResolveObservedAgentForMessage(string? messageId, out AgentIdentity agent)
+    {
+        agent = default;
+        return !string.IsNullOrWhiteSpace(messageId)
+            && _observedAgentsByMessageId.TryGetValue(messageId, out agent);
+    }
+
+    public string CreateMessageId(string? messageId)
+    {
+        return messageId ?? $"{_command.RequestId}-delta-{_fallbackMessageIndex++}";
+    }
+
+    public TranscriptSegment AppendDelta(
+        string messageId,
+        string authorName,
+        string delta)
+    {
+        return _transcriptBuffer.AppendDelta(messageId, authorName, delta);
+    }
+
+    public void ClearActiveAgentIfMatching(AgentIdentity completedAgent)
+    {
+        if (ActiveAgent.HasValue
+            && string.Equals(ActiveAgent.Value.AgentId, completedAgent.AgentId, StringComparison.Ordinal))
+        {
+            ActiveAgent = null;
+        }
+    }
+
+    private void RecordObservedAgentForMessage(AgentIdentity agent, string messageId)
+    {
+        ActiveAgent = agent;
+        _observedAgentsByMessageId[messageId] = agent;
+        _lastObservedMessageId = messageId;
+    }
+
+    private void QueueMessageReclassifiedIfNeeded(string? messageId)
+    {
+        if (string.IsNullOrWhiteSpace(messageId))
+        {
+            return;
+        }
+
+        string normalizedMessageId = messageId.Trim();
+        if (!_reclassifiedMessageIds.Add(normalizedMessageId))
+        {
+            return;
+        }
+
+        _pendingEvents.Enqueue(CreateMessageReclassifiedEvent(normalizedMessageId));
+    }
+
+    private AgentActivityEventDto? CreateThinkingActivityIfNeeded(AgentIdentity agent)
+    {
+        ActiveAgent = agent;
+
+        if (!_startedAgents.Add(agent.AgentId))
+        {
+            return null;
+        }
+
+        return new AgentActivityEventDto
+        {
+            Type = "agent-activity",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            ActivityType = "thinking",
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+        };
+    }
+
+    private AgentActivityEventDto? CreateToolCallingActivity(
+        AgentIdentity agent,
+        string toolName,
+        string toolCallId,
+        IReadOnlyDictionary<string, object?>? toolArguments = null)
+    {
+        if (toolName.StartsWith("handoff_to_", StringComparison.Ordinal))
+        {
+            return null;
+        }
+
+        return new AgentActivityEventDto
+        {
+            Type = "agent-activity",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            ActivityType = "tool-calling",
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            ToolName = toolName,
+            ToolCallId = toolCallId,
+            ToolArguments = toolArguments,
+        };
+    }
+
+    private AgentActivityEventDto CreateCompletedActivity(AgentIdentity agent)
+    {
+        return new AgentActivityEventDto
+        {
+            Type = "agent-activity",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            ActivityType = "completed",
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+        };
+    }
+
+    private MessageReclassifiedEventDto CreateMessageReclassifiedEvent(string messageId)
+    {
+        return new MessageReclassifiedEventDto
+        {
+            Type = "message-reclassified",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            MessageId = messageId,
+            NewKind = "thinking",
+        };
+    }
+
+    public void UpdateCompletedMessages(
+        IReadOnlyList<ChatMessage> allMessages,
+        IReadOnlyList<ChatMessage> inputMessages,
+        IProviderTranscriptProjector transcriptProjector)
+    {
+        ArgumentNullException.ThrowIfNull(transcriptProjector);
+
+        List<ChatMessage> newMessages = transcriptProjector.SelectNewOutputMessages(allMessages, inputMessages);
+        CompletedMessages = transcriptProjector.ProjectCompletedMessagesFromSegments(
+            _command,
+            newMessages,
+            _transcriptBuffer.Snapshot(),
+            ActiveAgent);
+    }
+
+    public IReadOnlyList<ChatMessageDto> FinalizeCompletedMessages(IProviderTranscriptProjector transcriptProjector)
+    {
+        ArgumentNullException.ThrowIfNull(transcriptProjector);
+
+        if (CompletedMessages.Count == 0 && _transcriptBuffer.Count > 0)
+        {
+            CompletedMessages = transcriptProjector.ProjectCompletedMessagesFromSegments(
+                _command,
+                [],
+                _transcriptBuffer.Snapshot(),
+                ActiveAgent);
+        }
+
+        foreach (ChatMessageDto message in CompletedMessages)
+        {
+            if (_reclassifiedMessageIds.Contains(message.Id))
+            {
+                message.MessageKind = "thinking";
+            }
+        }
+
+        return CompletedMessages;
+    }
+
+    private SubagentEventDto CreateSubagentStartedEvent(
+        AgentIdentity agent,
+        ProviderSubagentStartedEvent data)
+    {
+        return new SubagentEventDto
+        {
+            Type = "subagent-event",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            EventKind = "started",
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            ToolCallId = data.ToolCallId,
+            CustomAgentName = data.AgentName,
+            CustomAgentDisplayName = data.AgentDisplayName,
+            CustomAgentDescription = data.AgentDescription,
+        };
+    }
+
+    private SubagentEventDto CreateSubagentCompletedEvent(
+        AgentIdentity agent,
+        ProviderSubagentCompletedEvent data)
+    {
+        return new SubagentEventDto
+        {
+            Type = "subagent-event",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            EventKind = "completed",
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            ToolCallId = data.ToolCallId,
+            CustomAgentName = data.AgentName,
+            CustomAgentDisplayName = data.AgentDisplayName,
+        };
+    }
+
+    private SubagentEventDto CreateSubagentFailedEvent(
+        AgentIdentity agent,
+        ProviderSubagentFailedEvent data)
+    {
+        return new SubagentEventDto
+        {
+            Type = "subagent-event",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            EventKind = "failed",
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            ToolCallId = data.ToolCallId,
+            CustomAgentName = data.AgentName,
+            CustomAgentDisplayName = data.AgentDisplayName,
+            Error = data.Error,
+        };
+    }
+
+    private SubagentEventDto CreateSubagentSelectedEvent(
+        AgentIdentity agent,
+        ProviderSubagentSelectedEvent data)
+    {
+        return new SubagentEventDto
+        {
+            Type = "subagent-event",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            EventKind = "selected",
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            CustomAgentName = data.AgentName,
+            CustomAgentDisplayName = data.AgentDisplayName,
+            Tools = data.Tools,
+        };
+    }
+
+    private SubagentEventDto CreateSubagentDeselectedEvent(AgentIdentity agent)
+    {
+        return new SubagentEventDto
+        {
+            Type = "subagent-event",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            EventKind = "deselected",
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+        };
+    }
+
+    private AssistantIntentEventDto? CreateAssistantIntentEvent(
+        AgentIdentity agent,
+        string? intent)
+    {
+        string? normalizedIntent = intent?.Trim();
+        if (string.IsNullOrWhiteSpace(normalizedIntent))
+        {
+            return null;
+        }
+
+        return new AssistantIntentEventDto
+        {
+            Type = "assistant-intent",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            Intent = normalizedIntent,
+        };
+    }
+
+    private ReasoningDeltaEventDto? CreateReasoningDeltaEvent(
+        AgentIdentity agent,
+        string? reasoningId,
+        string? deltaContent)
+    {
+        if (string.IsNullOrWhiteSpace(reasoningId)
+            || string.IsNullOrEmpty(deltaContent))
+        {
+            return null;
+        }
+
+        return new ReasoningDeltaEventDto
+        {
+            Type = "reasoning-delta",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            ReasoningId = reasoningId,
+            ContentDelta = deltaContent,
+        };
+    }
+
+    private SkillInvokedEventDto CreateSkillInvokedEvent(
+        AgentIdentity agent,
+        ProviderSkillInvokedEvent data)
+    {
+        return new SkillInvokedEventDto
+        {
+            Type = "skill-invoked",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            SkillName = data.SkillName,
+            Path = data.Path,
+            Content = data.Content,
+            AllowedTools = data.AllowedTools,
+            PluginName = data.PluginName,
+            PluginVersion = data.PluginVersion,
+        };
+    }
+
+    private HookLifecycleEventDto CreateHookLifecycleEvent(
+        AgentIdentity agent,
+        string phase,
+        string hookInvocationId,
+        string hookType,
+        object? input = null,
+        bool? success = null,
+        object? output = null,
+        string? error = null)
+    {
+        return new HookLifecycleEventDto
+        {
+            Type = "hook-lifecycle",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            HookInvocationId = hookInvocationId,
+            HookType = hookType,
+            Phase = phase,
+            Input = input,
+            Success = success,
+            Output = output,
+            Error = error,
+        };
+    }
+
+    private AssistantUsageEventDto CreateAssistantUsageEvent(
+        AgentIdentity agent,
+        ProviderAssistantUsageEvent data)
+    {
+        return new AssistantUsageEventDto
+        {
+            Type = "assistant-usage",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            Model = data.Model,
+            InputTokens = data.InputTokens,
+            OutputTokens = data.OutputTokens,
+            CacheReadTokens = data.CacheReadTokens,
+            CacheWriteTokens = data.CacheWriteTokens,
+            Cost = data.Cost,
+            Duration = data.Duration,
+            TotalNanoAiu = data.TotalNanoAiu,
+            QuotaSnapshots = data.QuotaSnapshots,
+        };
+    }
+
+    private SessionUsageEventDto CreateUsageEvent(AgentIdentity agent, ProviderSessionUsageEvent data)
+    {
+        return new SessionUsageEventDto
+        {
+            Type = "session-usage",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            TokenLimit = data.TokenLimit,
+            CurrentTokens = data.CurrentTokens,
+            MessagesLength = data.MessagesLength,
+            SystemTokens = data.SystemTokens,
+            ConversationTokens = data.ConversationTokens,
+            ToolDefinitionsTokens = data.ToolDefinitionsTokens,
+            IsInitial = data.IsInitial,
+        };
+    }
+
+    private SessionCompactionEventDto CreateCompactionStartEvent(
+        AgentIdentity agent,
+        ProviderSessionCompactionStartEvent data)
+    {
+        return new SessionCompactionEventDto
+        {
+            Type = "session-compaction",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            Phase = "start",
+            SystemTokens = data.SystemTokens,
+            ConversationTokens = data.ConversationTokens,
+            ToolDefinitionsTokens = data.ToolDefinitionsTokens,
+        };
+    }
+
+    private SessionCompactionEventDto CreateCompactionCompleteEvent(
+        AgentIdentity agent,
+        ProviderSessionCompactionCompleteEvent data)
+    {
+        return new SessionCompactionEventDto
+        {
+            Type = "session-compaction",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+            Phase = "complete",
+            Success = data.Success,
+            Error = data.Error,
+            SystemTokens = data.SystemTokens,
+            ConversationTokens = data.ConversationTokens,
+            ToolDefinitionsTokens = data.ToolDefinitionsTokens,
+            PreCompactionTokens = data.PreCompactionTokens,
+            PostCompactionTokens = data.PostCompactionTokens,
+            PreCompactionMessagesLength = data.PreCompactionMessagesLength,
+            MessagesRemoved = data.MessagesRemoved,
+            TokensRemoved = data.TokensRemoved,
+            SummaryContent = data.SummaryContent,
+            CheckpointNumber = data.CheckpointNumber,
+            CheckpointPath = data.CheckpointPath,
+        };
+    }
+
+    private PendingMessagesModifiedEventDto CreatePendingMessagesModifiedEvent(AgentIdentity agent)
+    {
+        return new PendingMessagesModifiedEventDto
+        {
+            Type = "pending-messages-modified",
+            RequestId = _command.RequestId,
+            SessionId = _command.SessionId,
+            AgentId = agent.AgentId,
+            AgentName = agent.AgentName,
+        };
+    }
+}

sidecar/src/Aryx.AgentHost/Services/WorkflowOrchestrationFactory.cs

@@ -0,0 +1,196 @@
+using System.Linq;
+using Aryx.AgentHost.Contracts;
+using Microsoft.Agents.AI;
+using Microsoft.Agents.AI.Workflows;
+
+namespace Aryx.AgentHost.Services;
+
+internal static class WorkflowOrchestrationFactory
+{
+    public static HandoffWorkflowBuilder CreateHandoffWorkflowBuilder(
+        AIAgent entryAgent,
+        HandoffModeSettingsDto? settings = null)
+    {
+        HandoffModeSettingsDto effectiveSettings = settings ?? new HandoffModeSettingsDto();
+        HandoffWorkflowBuilder builder = AgentWorkflowBuilder.CreateHandoffBuilderWith(entryAgent)
+            .WithToolCallFilteringBehavior(MapHandoffToolCallFiltering(effectiveSettings.ToolCallFiltering))
+            .WithHandoffInstructions(NormalizeOptionalString(effectiveSettings.HandoffInstructions)
+                ?? HandoffWorkflowGuidance.CreateWorkflowInstructions());
+
+        if (effectiveSettings.ReturnToPrevious)
+        {
+            builder = builder.EnableReturnToPrevious();
+        }
+
+        return builder;
+    }
+
+    public static Workflow CreateHandoffWorkflow(
+        WorkflowDefinitionDto workflowDefinition,
+        IReadOnlyList<AIAgent> agents)
+    {
+        ArgumentNullException.ThrowIfNull(workflowDefinition);
+        ArgumentNullException.ThrowIfNull(agents);
+
+        IReadOnlyList<WorkflowNodeDto> agentNodes = workflowDefinition.GetAgentNodes();
+        Dictionary<string, AIAgent> agentsById = CreateAgentMap(agents);
+        WorkflowNodeDto triageNode = ResolveTriageAgentNode(workflowDefinition, agentNodes);
+        AIAgent triageAgent = ResolveAgentForNode(triageNode, agentsById);
+        HandoffModeSettingsDto? settings = workflowDefinition.Settings.ModeSettings?.Handoff;
+        HandoffWorkflowBuilder builder = CreateHandoffWorkflowBuilder(triageAgent, settings);
+
+        List<WorkflowNodeDto> specialistNodes = agentNodes
+            .Where(node => !string.Equals(node.Id, triageNode.Id, StringComparison.Ordinal))
+            .ToList();
+
+        if (specialistNodes.Count == 0)
+        {
+            throw new InvalidOperationException("Handoff workflows require at least one specialist agent in addition to the triage agent.");
+        }
+
+        foreach (WorkflowNodeDto specialistNode in specialistNodes)
+        {
+            AIAgent specialistAgent = ResolveAgentForNode(specialistNode, agentsById);
+            builder.WithHandoff(
+                triageAgent,
+                specialistAgent,
+                HandoffWorkflowGuidance.CreateForwardReason(specialistNode));
+
+            if (settings?.ReturnToPrevious != true)
+            {
+                builder.WithHandoff(
+                    specialistAgent,
+                    triageAgent,
+                    HandoffWorkflowGuidance.CreateReturnReason(triageNode));
+            }
+        }
+
+        return builder.Build();
+    }
+
+    public static GroupChatWorkflowBuilder CreateGroupChatWorkflowBuilder(
+        WorkflowDefinitionDto workflowDefinition,
+        IReadOnlyList<AIAgent> agents)
+    {
+        ArgumentNullException.ThrowIfNull(workflowDefinition);
+        ArgumentNullException.ThrowIfNull(agents);
+
+        int maxRounds = ResolveGroupChatMaxRounds(workflowDefinition);
+        GroupChatWorkflowBuilder builder = AgentWorkflowBuilder.CreateGroupChatBuilderWith(
+            participants => new RoundRobinGroupChatManager(participants)
+            {
+                MaximumIterationCount = maxRounds,
+            })
+            .AddParticipants(agents);
+
+        string? name = NormalizeOptionalString(workflowDefinition.Name);
+        if (name is not null)
+        {
+            builder.WithName(name);
+        }
+
+        string? description = NormalizeOptionalString(workflowDefinition.Description);
+        if (description is not null)
+        {
+            builder.WithDescription(description);
+        }
+
+        return builder;
+    }
+
+    public static Workflow CreateGroupChatWorkflow(
+        WorkflowDefinitionDto workflowDefinition,
+        IReadOnlyList<AIAgent> agents)
+    {
+        return CreateGroupChatWorkflowBuilder(workflowDefinition, agents).Build();
+    }
+
+    private static Dictionary<string, AIAgent> CreateAgentMap(IReadOnlyList<AIAgent> agents)
+    {
+        Dictionary<string, AIAgent> agentMap = new(StringComparer.OrdinalIgnoreCase);
+        foreach (AIAgent agent in agents)
+        {
+            if (!string.IsNullOrWhiteSpace(agent.Id))
+            {
+                agentMap[agent.Id] = agent;
+            }
+
+            if (!string.IsNullOrWhiteSpace(agent.Name))
+            {
+                agentMap[agent.Name] = agent;
+            }
+        }
+
+        return agentMap;
+    }
+
+    private static AIAgent ResolveAgentForNode(
+        WorkflowNodeDto node,
+        IReadOnlyDictionary<string, AIAgent> agentsById)
+    {
+        string agentId = node.GetAgentId();
+        if (agentsById.TryGetValue(agentId, out AIAgent? agent))
+        {
+            return agent;
+        }
+
+        string agentName = node.GetAgentName();
+        if (agentsById.TryGetValue(agentName, out agent))
+        {
+            return agent;
+        }
+
+        throw new InvalidOperationException($"Workflow agent \"{agentId}\" could not be resolved from the constructed agents.");
+    }
+
+    private static WorkflowNodeDto ResolveTriageAgentNode(
+        WorkflowDefinitionDto workflowDefinition,
+        IReadOnlyList<WorkflowNodeDto> agentNodes)
+    {
+        if (agentNodes.Count == 0)
+        {
+            throw new InvalidOperationException("Handoff workflows require at least one agent node.");
+        }
+
+        string? triageAgentNodeId = NormalizeOptionalString(workflowDefinition.Settings.ModeSettings?.Handoff?.TriageAgentNodeId);
+        if (triageAgentNodeId is null)
+        {
+            return agentNodes[0];
+        }
+
+        WorkflowNodeDto? triageNode = agentNodes.FirstOrDefault(node => string.Equals(node.Id, triageAgentNodeId, StringComparison.Ordinal));
+        return triageNode ?? throw new InvalidOperationException(
+            $"Handoff workflow triage agent node \"{triageAgentNodeId}\" was not found in the workflow graph.");
+    }
+
+    private static HandoffToolCallFilteringBehavior MapHandoffToolCallFiltering(string? value)
+    {
+        return value?.Trim().ToLowerInvariant() switch
+        {
+            "none" => HandoffToolCallFilteringBehavior.None,
+            "all" => HandoffToolCallFilteringBehavior.All,
+            _ => HandoffToolCallFilteringBehavior.HandoffOnly,
+        };
+    }
+
+    private static int ResolveGroupChatMaxRounds(WorkflowDefinitionDto workflowDefinition)
+    {
+        int? configuredMaxRounds = workflowDefinition.Settings.ModeSettings?.GroupChat?.MaxRounds;
+        if (configuredMaxRounds is > 0)
+        {
+            return configuredMaxRounds.Value;
+        }
+
+        if (workflowDefinition.Settings.MaxIterations is > 0)
+        {
+            return workflowDefinition.Settings.MaxIterations.Value;
+        }
+
+        return 5;
+    }
+
+    private static string? NormalizeOptionalString(string? value)
+    {
+        return string.IsNullOrWhiteSpace(value) ? null : value.Trim();
+    }
+}

sidecar/src/Aryx.AgentHost/Services/WorkflowRunner.cs

@@ -141,7 +141,7 @@ internal sealed class WorkflowRunner
                 throw new InvalidOperationException($"Workflow node \"{node.Id}\" references unknown agent \"{agentId}\".");
             }
 
-            return new WorkflowNodeRoute(agent.BindAsExecutor(CopilotAgentBundle.CreateAgentHostOptions()));
+            return new WorkflowNodeRoute(agent.BindAsExecutor(AgentHostOptionsFactory.CreateDefault()));
         }
 
         if (string.Equals(node.Kind, "code-executor", StringComparison.OrdinalIgnoreCase))