feat: surface workflow diagnostics

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

ARCHITECTURE.md

@@ -224,6 +224,7 @@ The protocol also carries **turn-scoped lifecycle events** alongside output delt
 - **Session compaction events**: start and complete, with token-reduction metrics when infinite sessions trigger context trimming
 - **Session usage events**: current token count and context-window limit from `session.usage_info` for context-bar rendering
 - **Pending-messages-modified events**: emitted when mid-turn steering changes the pending message queue
+- **Workflow diagnostic events**: normalized warnings and errors from Agent Framework (`WorkflowWarningEvent`, `WorkflowErrorEvent`, `ExecutorFailedEvent`) with optional executor or subworkflow metadata for richer debugging surfaces
 
 These events flow through a single `onTurnScopedEvent` callback on the `runTurn` command, avoiding per-event-type callback proliferation. The main process maps each event to a `SessionEventRecord` and pushes it to the renderer, where lightweight state maps (activity, usage, turn-event log) consume them without touching the persisted workspace.
 

sidecar/src/Aryx.AgentHost/Contracts/ProtocolModels.cs

@@ -488,6 +488,19 @@ public sealed class PendingMessagesModifiedEventDto : SidecarEventDto
     public string? AgentName { get; init; }
 }
 
+public sealed class WorkflowDiagnosticEventDto : SidecarEventDto
+{
+    public string SessionId { get; init; } = string.Empty;
+    public string Severity { get; init; } = string.Empty;
+    public string DiagnosticKind { get; init; } = string.Empty;
+    public string Message { get; init; } = string.Empty;
+    public string? AgentId { get; init; }
+    public string? AgentName { get; init; }
+    public string? ExecutorId { get; init; }
+    public string? SubworkflowId { get; init; }
+    public string? ExceptionType { get; init; }
+}
+
 public sealed class SessionsListedEventDto : SidecarEventDto
 {
     public IReadOnlyList<CopilotSessionInfoDto> Sessions { get; init; } = [];

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

@@ -211,6 +211,12 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
             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);
@@ -341,6 +347,94 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
         }
     }
 
+    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.Pattern,
+                    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 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)

sidecar/tests/Aryx.AgentHost.Tests/CopilotWorkflowRunnerTests.cs

@@ -798,6 +798,117 @@ public sealed class CopilotWorkflowRunnerTests
             });
     }
 
+    [Fact]
+    public async Task HandleWorkflowEventAsync_EmitsExecutorFailedDiagnostic()
+    {
+        RunTurnCommandDto command = CreateApprovalCommand();
+        CopilotTurnExecutionState state = new(command);
+        List<WorkflowDiagnosticEventDto> diagnostics = [];
+
+        MethodInfo handleWorkflowEvent = typeof(CopilotWorkflowRunner).GetMethod(
+            "HandleWorkflowEventAsync",
+            BindingFlags.NonPublic | BindingFlags.Static)!;
+        Task<bool> handleTask = (Task<bool>)handleWorkflowEvent.Invoke(
+            null,
+            [
+                command,
+                new ExecutorFailedEvent("agent-1", new InvalidOperationException("Tool crashed.")),
+                Array.Empty<ChatMessage>(),
+                state,
+                (Func<TurnDeltaEventDto, Task>)(_ => Task.CompletedTask),
+                (Func<SidecarEventDto, Task>)(sidecarEvent =>
+                {
+                    diagnostics.Add(Assert.IsType<WorkflowDiagnosticEventDto>(sidecarEvent));
+                    return Task.CompletedTask;
+                }),
+            ])!;
+
+        bool shouldEndTurn = await handleTask;
+
+        Assert.False(shouldEndTurn);
+        WorkflowDiagnosticEventDto diagnostic = Assert.Single(diagnostics);
+        Assert.Equal("workflow-diagnostic", diagnostic.Type);
+        Assert.Equal("error", diagnostic.Severity);
+        Assert.Equal("executor-failed", diagnostic.DiagnosticKind);
+        Assert.Equal("Tool crashed.", diagnostic.Message);
+        Assert.Equal("agent-1", diagnostic.AgentId);
+        Assert.Equal("Primary", diagnostic.AgentName);
+        Assert.Equal("agent-1", diagnostic.ExecutorId);
+        Assert.Equal("InvalidOperationException", diagnostic.ExceptionType);
+    }
+
+    [Fact]
+    public async Task HandleWorkflowEventAsync_EmitsWorkflowWarningDiagnostic()
+    {
+        RunTurnCommandDto command = CreateApprovalCommand();
+        CopilotTurnExecutionState state = new(command);
+        List<WorkflowDiagnosticEventDto> diagnostics = [];
+
+        MethodInfo handleWorkflowEvent = typeof(CopilotWorkflowRunner).GetMethod(
+            "HandleWorkflowEventAsync",
+            BindingFlags.NonPublic | BindingFlags.Static)!;
+        Task<bool> handleTask = (Task<bool>)handleWorkflowEvent.Invoke(
+            null,
+            [
+                command,
+                new WorkflowWarningEvent("Token budget is nearly exhausted."),
+                Array.Empty<ChatMessage>(),
+                state,
+                (Func<TurnDeltaEventDto, Task>)(_ => Task.CompletedTask),
+                (Func<SidecarEventDto, Task>)(sidecarEvent =>
+                {
+                    diagnostics.Add(Assert.IsType<WorkflowDiagnosticEventDto>(sidecarEvent));
+                    return Task.CompletedTask;
+                }),
+            ])!;
+
+        bool shouldEndTurn = await handleTask;
+
+        Assert.False(shouldEndTurn);
+        WorkflowDiagnosticEventDto diagnostic = Assert.Single(diagnostics);
+        Assert.Equal("warning", diagnostic.Severity);
+        Assert.Equal("workflow-warning", diagnostic.DiagnosticKind);
+        Assert.Equal("Token budget is nearly exhausted.", diagnostic.Message);
+        Assert.Null(diagnostic.SubworkflowId);
+        Assert.Null(diagnostic.ExceptionType);
+    }
+
+    [Fact]
+    public async Task HandleWorkflowEventAsync_EmitsSubworkflowErrorDiagnostic()
+    {
+        RunTurnCommandDto command = CreateApprovalCommand();
+        CopilotTurnExecutionState state = new(command);
+        List<WorkflowDiagnosticEventDto> diagnostics = [];
+
+        MethodInfo handleWorkflowEvent = typeof(CopilotWorkflowRunner).GetMethod(
+            "HandleWorkflowEventAsync",
+            BindingFlags.NonPublic | BindingFlags.Static)!;
+        Task<bool> handleTask = (Task<bool>)handleWorkflowEvent.Invoke(
+            null,
+            [
+                command,
+                new SubworkflowErrorEvent("subworkflow-review", new InvalidOperationException("Reviewer agent failed.")),
+                Array.Empty<ChatMessage>(),
+                state,
+                (Func<TurnDeltaEventDto, Task>)(_ => Task.CompletedTask),
+                (Func<SidecarEventDto, Task>)(sidecarEvent =>
+                {
+                    diagnostics.Add(Assert.IsType<WorkflowDiagnosticEventDto>(sidecarEvent));
+                    return Task.CompletedTask;
+                }),
+            ])!;
+
+        bool shouldEndTurn = await handleTask;
+
+        Assert.False(shouldEndTurn);
+        WorkflowDiagnosticEventDto diagnostic = Assert.Single(diagnostics);
+        Assert.Equal("error", diagnostic.Severity);
+        Assert.Equal("subworkflow-error", diagnostic.DiagnosticKind);
+        Assert.Equal("Reviewer agent failed.", diagnostic.Message);
+        Assert.Equal("subworkflow-review", diagnostic.SubworkflowId);
+        Assert.Equal("InvalidOperationException", diagnostic.ExceptionType);
+    }
+
     [Fact]
     public void RequiresToolCallApproval_HonorsAutoApprovedToolNames()
     {

sidecar/tests/Aryx.AgentHost.Tests/SidecarProtocolHostTests.cs

@@ -232,6 +232,77 @@ public sealed class SidecarProtocolHostTests
             });
     }
 
+    [Fact]
+    public async Task RunTurnCommand_ReturnsWorkflowDiagnosticEventsAndCompletion()
+    {
+        SidecarProtocolHost host = new(
+            new PatternValidator(),
+            new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
+            {
+                await onActivity(new WorkflowDiagnosticEventDto
+                {
+                    Type = "workflow-diagnostic",
+                    RequestId = command.RequestId,
+                    SessionId = command.SessionId,
+                    Severity = "error",
+                    DiagnosticKind = "executor-failed",
+                    Message = "Tool crashed.",
+                    AgentId = "agent-1",
+                    AgentName = "Primary",
+                    ExecutorId = "agent-1",
+                    ExceptionType = "InvalidOperationException",
+                });
+
+                return [];
+            }));
+
+        IReadOnlyList<JsonElement> events = await RunHostAsync(
+            new RunTurnCommandDto
+            {
+                Type = "run-turn",
+                RequestId = "turn-diagnostic",
+                SessionId = "session-1",
+                ProjectPath = "C:\\workspace\\project",
+                Pattern = new PatternDefinitionDto
+                {
+                    Id = "pattern-1",
+                    Name = "Single Agent",
+                    Mode = "single",
+                    Availability = "available",
+                    Agents =
+                    [
+                        CreateAgent(name: "Primary"),
+                    ],
+                },
+                Messages = [],
+            },
+            host);
+
+        Assert.Collection(
+            events,
+            diagnosticEvent =>
+            {
+                Assert.Equal("workflow-diagnostic", diagnosticEvent.GetProperty("type").GetString());
+                Assert.Equal("turn-diagnostic", diagnosticEvent.GetProperty("requestId").GetString());
+                Assert.Equal("session-1", diagnosticEvent.GetProperty("sessionId").GetString());
+                Assert.Equal("error", diagnosticEvent.GetProperty("severity").GetString());
+                Assert.Equal("executor-failed", diagnosticEvent.GetProperty("diagnosticKind").GetString());
+                Assert.Equal("Tool crashed.", diagnosticEvent.GetProperty("message").GetString());
+                Assert.Equal("agent-1", diagnosticEvent.GetProperty("executorId").GetString());
+            },
+            completionEvent =>
+            {
+                Assert.Equal("turn-complete", completionEvent.GetProperty("type").GetString());
+                Assert.Equal("session-1", completionEvent.GetProperty("sessionId").GetString());
+                Assert.False(completionEvent.GetProperty("cancelled").GetBoolean());
+            },
+            commandCompleteEvent =>
+            {
+                Assert.Equal("command-complete", commandCompleteEvent.GetProperty("type").GetString());
+                Assert.Equal("turn-diagnostic", commandCompleteEvent.GetProperty("requestId").GetString());
+            });
+    }
+
     [Fact]
     public async Task RunTurnCommand_DeserializesInteractionMode()
     {

src/main/AryxAppService.ts

@@ -2504,6 +2504,21 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
           agentName: event.agentName,
         });
         return;
+      case 'workflow-diagnostic':
+        this.emitSessionEvent({
+          sessionId,
+          kind: 'workflow-diagnostic',
+          occurredAt,
+          agentId: event.agentId,
+          agentName: event.agentName,
+          diagnosticSeverity: event.severity,
+          diagnosticKind: event.diagnosticKind,
+          diagnosticMessage: event.message,
+          executorId: event.executorId,
+          subworkflowId: event.subworkflowId,
+          exceptionType: event.exceptionType,
+        });
+        return;
       case 'assistant-usage':
         this.emitSessionEvent({
           sessionId,

src/main/sidecar/runTurnPending.ts

@@ -15,6 +15,7 @@ import type {
   AssistantUsageEvent,
   AssistantIntentEvent,
   ReasoningDeltaEvent,
+  WorkflowDiagnosticEvent,
 } from '@shared/contracts/sidecar';
 import type { ChatMessageRecord } from '@shared/domain/session';
 
@@ -27,7 +28,8 @@ export type TurnScopedEvent =
   | PendingMessagesModifiedEvent
   | AssistantUsageEvent
   | AssistantIntentEvent
-  | ReasoningDeltaEvent;
+  | ReasoningDeltaEvent
+  | WorkflowDiagnosticEvent;
 
 export interface RunTurnPendingCommand {
   kind: 'run-turn';

src/main/sidecar/sidecarProcess.ts

@@ -454,6 +454,7 @@ export class SidecarClient {
       case 'session-usage':
       case 'session-compaction':
       case 'pending-messages-modified':
+      case 'workflow-diagnostic':
       case 'assistant-usage':
       case 'assistant-intent':
       case 'reasoning-delta':

src/shared/contracts/sidecar.ts

@@ -384,6 +384,28 @@ export interface PendingMessagesModifiedEvent {
   agentName?: string;
 }
 
+export type WorkflowDiagnosticSeverity = 'warning' | 'error';
+export type WorkflowDiagnosticKind =
+  | 'workflow-warning'
+  | 'workflow-error'
+  | 'executor-failed'
+  | 'subworkflow-warning'
+  | 'subworkflow-error';
+
+export interface WorkflowDiagnosticEvent {
+  type: 'workflow-diagnostic';
+  requestId: string;
+  sessionId: string;
+  severity: WorkflowDiagnosticSeverity;
+  diagnosticKind: WorkflowDiagnosticKind;
+  message: string;
+  agentId?: string;
+  agentName?: string;
+  executorId?: string;
+  subworkflowId?: string;
+  exceptionType?: string;
+}
+
 export interface CopilotSessionInfo {
   copilotSessionId: string;
   managedByAryx: boolean;
@@ -563,6 +585,7 @@ export type SidecarEvent =
   | SessionUsageEvent
   | SessionCompactionEvent
   | PendingMessagesModifiedEvent
+  | WorkflowDiagnosticEvent
   | ApprovalRequestedEvent
   | UserInputRequestedEvent
   | McpOauthRequiredEvent

src/shared/domain/event.ts

@@ -1,7 +1,12 @@
 import type { SessionRunRecord } from '@shared/domain/runTimeline';
 import type { ChatMessageKind } from '@shared/domain/session';
 
-import type { QuotaSnapshot, ToolCallFileChangePreview } from '@shared/contracts/sidecar';
+import type {
+  QuotaSnapshot,
+  ToolCallFileChangePreview,
+  WorkflowDiagnosticKind,
+  WorkflowDiagnosticSeverity,
+} from '@shared/contracts/sidecar';
 
 export type SessionActivityType = 'thinking' | 'tool-calling' | 'handoff' | 'completed';
 
@@ -19,7 +24,8 @@ export type SessionEventKind =
   | 'session-usage'
   | 'session-compaction'
   | 'pending-messages-modified'
-  | 'assistant-usage';
+  | 'assistant-usage'
+  | 'workflow-diagnostic';
 
 export type SubagentEventKind = 'started' | 'completed' | 'failed' | 'selected' | 'deselected';
 
@@ -86,4 +92,12 @@ export interface SessionEventRecord {
   usageDuration?: number;
   usageTotalNanoAiu?: number;
   usageQuotaSnapshots?: Record<string, QuotaSnapshot>;
+
+  // Workflow diagnostic fields
+  diagnosticSeverity?: WorkflowDiagnosticSeverity;
+  diagnosticKind?: WorkflowDiagnosticKind;
+  diagnosticMessage?: string;
+  executorId?: string;
+  subworkflowId?: string;
+  exceptionType?: string;
 }

tests/main/appServiceWorkflowDiagnostics.test.ts

@@ -0,0 +1,82 @@
+import { describe, expect, mock, test } from 'bun:test';
+
+import type { SessionEventRecord } from '@shared/domain/event';
+import type { WorkflowDiagnosticEvent } from '@shared/contracts/sidecar';
+
+mock.module('electron', () => {
+  const electronMock = {
+    app: {
+      isPackaged: false,
+      getAppPath: () => 'C:\\workspace\\personal\\repositories\\aryx',
+      getPath: () => 'C:\\workspace\\personal\\repositories\\aryx\\tests\\fixtures',
+    },
+    dialog: {
+      showOpenDialog: async () => ({ canceled: true, filePaths: [] }),
+    },
+    shell: {
+      openPath: async () => '',
+    },
+  };
+
+  return {
+    ...electronMock,
+    default: electronMock,
+  };
+});
+
+mock.module('keytar', () => ({
+  default: {
+    getPassword: async () => null,
+    setPassword: async () => undefined,
+    deletePassword: async () => false,
+  },
+}));
+
+const { AryxAppService } = await import('@main/AryxAppService');
+
+describe('AryxAppService workflow diagnostics', () => {
+  test('maps turn-scoped workflow diagnostics to session events', async () => {
+    const service = new AryxAppService();
+    const captured: SessionEventRecord[] = [];
+    const workflowDiagnostic: WorkflowDiagnosticEvent = {
+      type: 'workflow-diagnostic',
+      requestId: 'turn-1',
+      sessionId: 'session-1',
+      severity: 'error',
+      diagnosticKind: 'executor-failed',
+      message: 'Tool crashed.',
+      agentId: 'agent-1',
+      agentName: 'Primary',
+      executorId: 'agent-1',
+      exceptionType: 'InvalidOperationException',
+    };
+
+    const internals = service as unknown as {
+      emitSessionEvent: (event: SessionEventRecord) => void;
+      handleTurnScopedEvent: (
+        workspace: unknown,
+        sessionId: string,
+        event: WorkflowDiagnosticEvent,
+      ) => void | Promise<void>;
+    };
+    internals.emitSessionEvent = (event) => {
+      captured.push(event);
+    };
+
+    await internals.handleTurnScopedEvent({}, 'session-1', workflowDiagnostic);
+
+    expect(captured).toHaveLength(1);
+    expect(captured[0]).toMatchObject({
+      sessionId: 'session-1',
+      kind: 'workflow-diagnostic',
+      agentId: 'agent-1',
+      agentName: 'Primary',
+      diagnosticSeverity: 'error',
+      diagnosticKind: 'executor-failed',
+      diagnosticMessage: 'Tool crashed.',
+      executorId: 'agent-1',
+      exceptionType: 'InvalidOperationException',
+    });
+    expect(captured[0]?.occurredAt).toEqual(expect.any(String));
+  });
+});

tests/main/sidecarProcess.test.ts

@@ -2,7 +2,7 @@ import { EventEmitter } from 'node:events';
 
 import { describe, expect, mock, test } from 'bun:test';
 
-import type { SidecarCapabilities } from '@shared/contracts/sidecar';
+import type { RunTurnCommand, SidecarCapabilities, WorkflowDiagnosticEvent } from '@shared/contracts/sidecar';
 
 class FakeReadableStream extends EventEmitter {
   setEncoding(_encoding: BufferEncoding): void {}
@@ -142,4 +142,100 @@ describe('SidecarClient', () => {
     spawnedProcesses[1]!.completeExit();
     await finalDispose;
   });
+
+  test('routes workflow diagnostic events through the turn-scoped callback', async () => {
+    spawnedProcesses.length = 0;
+    const client = new SidecarClient();
+    const diagnostics: WorkflowDiagnosticEvent[] = [];
+    const command: RunTurnCommand = {
+      type: 'run-turn',
+      requestId: 'turn-1',
+      sessionId: 'session-1',
+      projectPath: 'C:\\workspace\\project',
+      pattern: {
+        id: 'pattern-1',
+        name: 'Single Agent',
+        description: '',
+        mode: 'single',
+        availability: 'available',
+        maxIterations: 1,
+        agents: [
+          {
+            id: 'agent-1',
+            name: 'Primary',
+            description: '',
+            instructions: 'Help with the request.',
+            model: 'gpt-5.4',
+          },
+        ],
+        createdAt: '2026-04-01T00:00:00.000Z',
+        updatedAt: '2026-04-01T00:00:00.000Z',
+      },
+      messages: [],
+    };
+
+    const turn = client.runTurn(
+      command,
+      async () => undefined,
+      async () => undefined,
+      async () => undefined,
+      async () => undefined,
+      async () => undefined,
+      async () => undefined,
+      async () => undefined,
+      async (event) => {
+        if (event.type === 'workflow-diagnostic') {
+          diagnostics.push(event);
+        }
+      },
+    );
+
+    await Promise.resolve();
+    expect(spawnedProcesses).toHaveLength(1);
+
+    spawnedProcesses[0]!.emitStdout(
+      `${JSON.stringify({
+        type: 'workflow-diagnostic',
+        requestId: command.requestId,
+        sessionId: command.sessionId,
+        severity: 'error',
+        diagnosticKind: 'executor-failed',
+        message: 'Tool crashed.',
+        agentId: 'agent-1',
+        agentName: 'Primary',
+        executorId: 'agent-1',
+        exceptionType: 'InvalidOperationException',
+      } satisfies WorkflowDiagnosticEvent)}\n`,
+    );
+    spawnedProcesses[0]!.emitStdout(
+      `${JSON.stringify({
+        type: 'turn-complete',
+        requestId: command.requestId,
+        sessionId: command.sessionId,
+        messages: [],
+        cancelled: false,
+      })}\n`,
+    );
+    spawnedProcesses[0]!.emitStdout(
+      `${JSON.stringify({
+        type: 'command-complete',
+        requestId: command.requestId,
+      })}\n`,
+    );
+
+    await expect(turn).resolves.toEqual([]);
+    expect(diagnostics).toEqual([
+      expect.objectContaining({
+        type: 'workflow-diagnostic',
+        severity: 'error',
+        diagnosticKind: 'executor-failed',
+        message: 'Tool crashed.',
+        executorId: 'agent-1',
+      }),
+    ]);
+
+    const dispose = client.dispose();
+    spawnedProcesses[0]!.completeExit();
+    await dispose;
+  });
 });