Add regression tests for path casing normalization

PathUtilL0:
- Folder casing normalization (create MiXeDcAsE, query lowercase)
- Idempotency (calling twice returns same result)
- Input casing independence (upper and lower resolve to same canonical)

HostContextL0:
- Root directory returns cached value across calls
- Derived paths (Diag, Externals) share Root prefix casing

src/Runner.Common/HostContext.cs

@@ -64,6 +64,7 @@ namespace GitHub.Runner.Common
         private readonly List<ProductInfoHeaderValue> _userAgents = new() { new ProductInfoHeaderValue($"GitHubActionsRunner-{BuildConstants.RunnerPackage.PackageName}", BuildConstants.RunnerPackage.Version) };
         private CancellationTokenSource _runnerShutdownTokenSource = new();
         private object _perfLock = new();
+        private string _canonicalRootDirectory;
         private Tracing _trace;
         private Tracing _actionsHttpTrace;
         private Tracing _netcoreHttpTrace;
@@ -391,7 +392,12 @@ namespace GitHub.Runner.Common
                     break;
 
                 case WellKnownDirectory.Root:
-                    path = new DirectoryInfo(GetDirectory(WellKnownDirectory.Bin)).Parent.FullName;
+                    if (_canonicalRootDirectory == null)
+                    {
+                        _canonicalRootDirectory = PathUtil.GetCanonicalPath(
+                            new DirectoryInfo(GetDirectory(WellKnownDirectory.Bin)).Parent.FullName);
+                    }
+                    path = _canonicalRootDirectory;
                     break;
 
                 case WellKnownDirectory.Temp:

src/Runner.Sdk/Util/PathUtil.cs

@@ -1,4 +1,7 @@
 using System.IO;
+using System.Runtime.InteropServices;
+using System.Text;
+using Microsoft.Win32.SafeHandles;
 
 namespace GitHub.Runner.Sdk
 {
@@ -6,8 +9,98 @@ namespace GitHub.Runner.Sdk
     {
 #if OS_WINDOWS
         public static readonly string PathVariable = "Path";
+
+        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+        private static extern SafeFileHandle CreateFile(
+            string lpFileName,
+            uint dwDesiredAccess,
+            uint dwShareMode,
+            System.IntPtr lpSecurityAttributes,
+            uint dwCreationDisposition,
+            uint dwFlagsAndAttributes,
+            System.IntPtr hTemplateFile);
+
+        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
+        private static extern uint GetFinalPathNameByHandle(
+            SafeFileHandle hFile,
+            [Out] StringBuilder lpszFilePath,
+            uint cchFilePath,
+            uint dwFlags);
+
+        private const uint FILE_READ_ATTRIBUTES = 0x80;
+        private const uint FILE_SHARE_READ = 0x1;
+        private const uint FILE_SHARE_WRITE = 0x2;
+        private const uint FILE_SHARE_DELETE = 0x4;
+        private const uint OPEN_EXISTING = 3;
+        private const uint FILE_FLAG_BACKUP_SEMANTICS = 0x02000000;
+        private const uint VOLUME_NAME_DOS = 0x0;
+
+        /// <summary>
+        /// Returns the NTFS canonical path for a directory, resolving drive letter
+        /// and folder name casing to match what is stored on disk.
+        /// On non-Windows platforms, returns the path unchanged.
+        /// </summary>
+        public static string GetCanonicalPath(string path)
+        {
+            if (string.IsNullOrEmpty(path) || !Directory.Exists(path))
+            {
+                return path;
+            }
+
+            using var handle = CreateFile(
+                path,
+                FILE_READ_ATTRIBUTES,
+                FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+                System.IntPtr.Zero,
+                OPEN_EXISTING,
+                FILE_FLAG_BACKUP_SEMANTICS,
+                System.IntPtr.Zero);
+
+            if (handle.IsInvalid)
+            {
+                return path;
+            }
+
+            var buffer = new StringBuilder(1024);
+            var result = GetFinalPathNameByHandle(handle, buffer, (uint)buffer.Capacity, VOLUME_NAME_DOS);
+            if (result == 0)
+            {
+                return path;
+            }
+
+            // Retry with a larger buffer if the path was longer than expected
+            if (result >= buffer.Capacity)
+            {
+                buffer = new StringBuilder((int)result + 1);
+                result = GetFinalPathNameByHandle(handle, buffer, (uint)buffer.Capacity, VOLUME_NAME_DOS);
+                if (result == 0 || result >= buffer.Capacity)
+                {
+                    return path;
+                }
+            }
+
+            var canonicalPath = buffer.ToString();
+
+            // Strip the \\?\UNC\ prefix and convert to standard UNC path
+            if (canonicalPath.StartsWith(@"\\?\UNC\", System.StringComparison.Ordinal))
+            {
+                canonicalPath = @"\\" + canonicalPath.Substring(8);
+            }
+            // Strip the \\?\ prefix for local paths
+            else if (canonicalPath.StartsWith(@"\\?\", System.StringComparison.Ordinal))
+            {
+                canonicalPath = canonicalPath.Substring(4);
+            }
+
+            return canonicalPath;
+        }
 #else
         public static readonly string PathVariable = "PATH";
+
+        public static string GetCanonicalPath(string path)
+        {
+            return path;
+        }
 #endif
 
         public static string PrependPath(string path, string currentPath)

src/Runner.Worker/Dap/DapDebugger.cs

@@ -243,6 +243,26 @@ namespace GitHub.Runner.Worker.Dap
         {
             if (_state != DapSessionState.NotStarted)
             {
+                // Pause so the user can inspect final job state before we tear down,
+                // but only if the user was stepping through (not if they hit continue).
+                if (IsActive && _pauseOnNextStep)
+                {
+                    try
+                    {
+                        if (_jobContext != null)
+                        {
+                            Trace.Info("Job completed — pausing for inspection");
+                            SendStoppedEvent("completed", "Job completed — inspect variables before the session ends.");
+
+                            await WaitForCommandAsync(_jobContext.CancellationToken);
+                        }
+                    }
+                    catch (Exception ex)
+                    {
+                        Trace.Warning($"DAP job-completed pause error: {ex.Message}");
+                    }
+                }
+
                 try
                 {
                     OnJobCompleted();
@@ -252,8 +272,6 @@ namespace GitHub.Runner.Worker.Dap
                     Trace.Warning($"DAP OnJobCompleted error: {ex.Message}");
                 }
             }
-
-            await StopAsync();
         }
 
         public async Task StopAsync()
@@ -1302,6 +1320,13 @@ namespace GitHub.Runner.Worker.Dap
                 _commandTcs = new TaskCompletionSource<DapCommand>(TaskCreationOptions.RunContinuationsAsynchronously);
             }
 
+            // If cancellation already fired before we created the new TCS,
+            // the registration callback targeted the old one. Unblock now.
+            if (cancellationToken.IsCancellationRequested)
+            {
+                _commandTcs.TrySetResult(DapCommand.Disconnect);
+            }
+
             Trace.Info("Waiting for debugger command...");
 
             var command = await _commandTcs.Task;

src/Runner.Worker/Dap/IDapDebugger.cs

@@ -22,5 +22,6 @@ namespace GitHub.Runner.Worker.Dap
         Task OnStepStartingAsync(IStep step);
         void OnStepCompleted(IStep step);
         Task OnJobCompletedAsync();
+        Task StopAsync();
     }
 }

src/Runner.Worker/JobExtension.cs

@@ -16,6 +16,7 @@ using GitHub.DistributedTask.WebApi;
 using GitHub.Runner.Common;
 using GitHub.Runner.Common.Util;
 using GitHub.Runner.Sdk;
+using GitHub.Runner.Worker.Dap;
 using GitHub.Services.Common;
 using Newtonsoft.Json;
 using Pipelines = GitHub.DistributedTask.Pipelines;
@@ -50,6 +51,7 @@ namespace GitHub.Runner.Worker
         private Task _diskSpaceCheckTask = null;
         private CancellationTokenSource _serviceConnectivityCheckToken = new();
         private Task _serviceConnectivityCheckTask = null;
+        private IDapDebugger _dapDebugger;
 
         // Download all required actions.
         // Make sure all condition inputs are valid.
@@ -67,6 +69,7 @@ namespace GitHub.Runner.Worker
 
             List<IStep> preJobSteps = new();
             List<IStep> jobSteps = new();
+            var initSucceeded = false;
             using (var register = jobContext.CancellationToken.Register(() => { context.CancelToken(); }))
             {
                 try
@@ -481,6 +484,41 @@ namespace GitHub.Runner.Worker
                     Trace.Info($"Start checking service connectivity in background.");
                     _serviceConnectivityCheckTask = CheckServiceConnectivityAsync(context, _serviceConnectivityCheckToken.Token);
 
+                    // Start the DAP debugger and wait for a client connection inside
+                    // "Set up job" so the step stays in-progress while we wait.
+                    if (jobContext.Global.Debugger?.Enabled == true)
+                    {
+                        Trace.Info("Debugger enabled — starting inside Set up job");
+                        context.Output("Starting debugger…");
+
+                        try
+                        {
+                            _dapDebugger = HostContext.GetService<IDapDebugger>();
+                            await _dapDebugger.StartAsync(jobContext);
+
+                            context.Output("Waiting for debugger client to connect…");
+
+                            await _dapDebugger.WaitUntilReadyAsync();
+                            context.Output("Debugger connected.");
+                            AddDebuggerConnectionTelemetry(jobContext, "Connected");
+                        }
+                        catch (OperationCanceledException) when (jobContext.CancellationToken.IsCancellationRequested)
+                        {
+                            Trace.Info("Job was cancelled before debugger client connected.");
+                            AddDebuggerConnectionTelemetry(jobContext, "Canceled");
+                            context.Error("Job was cancelled before debugger client connected.");
+                            throw;
+                        }
+                        catch (Exception ex)
+                        {
+                            Trace.Error($"DAP debugger failed: {ex.Message}");
+                            AddDebuggerConnectionTelemetry(jobContext, $"Failed: {ex.GetType().Name}");
+                            context.Error("The debugger failed to start or no debugger client connected in time.");
+                            throw;
+                        }
+                    }
+
+                    initSucceeded = true;
                     return steps;
                 }
                 catch (OperationCanceledException ex) when (jobContext.CancellationToken.IsCancellationRequested)
@@ -501,12 +539,36 @@ namespace GitHub.Runner.Worker
                 }
                 finally
                 {
+                    // If InitializeJob failed after the debugger was started,
+                    // tear down the transport here since FinalizeJob won't run.
+                    if (!initSucceeded && _dapDebugger != null)
+                    {
+                        try
+                        {
+                            await _dapDebugger.StopAsync();
+                        }
+                        catch (Exception ex)
+                        {
+                            Trace.Warning($"DAP debugger cleanup during failed init: {ex.Message}");
+                        }
+                        _dapDebugger = null;
+                    }
+
                     context.Debug("Finishing: Set up job");
                     context.Complete();
                 }
             }
         }
 
+        private static void AddDebuggerConnectionTelemetry(IExecutionContext jobContext, string result)
+        {
+            jobContext.Global.JobTelemetry.Add(new JobTelemetry
+            {
+                Type = JobTelemetryType.General,
+                Message = $"DebuggerConnectionResult: {result}"
+            });
+        }
+
         private string GetWorkflowReference(IDictionary<string, VariableValue> variables)
         {
             var reference = "";
@@ -782,6 +844,34 @@ namespace GitHub.Runner.Worker
                 }
                 finally
                 {
+                    // Pause for debugger inspection, then tear down the DAP session.
+                    // OnJobCompletedAsync pauses first, then sends terminated/exited
+                    // events and stops the transport.
+                    if (_dapDebugger != null)
+                    {
+                        context.Output("Job completed — pausing for debugger inspection. Press continue to finish.");
+                        try
+                        {
+                            await _dapDebugger.OnJobCompletedAsync();
+                        }
+                        catch (Exception ex)
+                        {
+                            Trace.Warning($"DAP debugger completion error: {ex.Message}");
+                        }
+                        finally
+                        {
+                            try
+                            {
+                                await _dapDebugger.StopAsync();
+                            }
+                            catch (Exception ex)
+                            {
+                                Trace.Warning($"DAP debugger stop error: {ex.Message}");
+                            }
+                        }
+                        _dapDebugger = null;
+                    }
+
                     context.Debug("Finishing: Complete job");
                     context.Complete();
                 }

src/Runner.Worker/JobRunner.cs

@@ -13,7 +13,6 @@ using GitHub.DistributedTask.WebApi;
 using GitHub.Runner.Common;
 using GitHub.Runner.Common.Util;
 using GitHub.Runner.Sdk;
-using GitHub.Runner.Worker.Dap;
 using GitHub.Services.Common;
 using GitHub.Services.WebApi;
 using Sdk.RSWebApi.Contracts;
@@ -29,7 +28,6 @@ namespace GitHub.Runner.Worker
 
     public sealed class JobRunner : RunnerService, IJobRunner
     {
-        private const string DebuggerConnectionTelemetryPrefix = "DebuggerConnectionResult";
         private IJobServerQueue _jobServerQueue;
         private RunnerSettings _runnerSettings;
         private ITempDirectoryManager _tempDirectoryManager;
@@ -114,7 +112,6 @@ namespace GitHub.Runner.Worker
 
             IExecutionContext jobContext = null;
             CancellationTokenRegistration? runnerShutdownRegistration = null;
-            IDapDebugger dapDebugger = null;
             try
             {
                 // Create the job execution context.
@@ -181,25 +178,6 @@ namespace GitHub.Runner.Worker
                 _tempDirectoryManager = HostContext.GetService<ITempDirectoryManager>();
                 _tempDirectoryManager.InitializeTempDirectory(jobContext);
 
-                // Setup the debugger
-                if (jobContext.Global.Debugger?.Enabled == true)
-                {
-                    Trace.Info("Debugger enabled for this job run");
-
-                    try
-                    {
-                        dapDebugger = HostContext.GetService<IDapDebugger>();
-                        await dapDebugger.StartAsync(jobContext);
-                    }
-                    catch (Exception ex)
-                    {
-                        Trace.Error($"Failed to start DAP debugger: {ex.Message}");
-                        AddDebuggerConnectionTelemetry(jobContext, $"Failed: {ex.Message}");
-                        jobContext.Error("Failed to start debugger.");
-                        return await CompleteJobAsync(server, jobContext, message, TaskResult.Failed);
-                    }
-                }
-
 
                 // Get the job extension.
                 Trace.Info("Getting job extension.");
@@ -242,33 +220,6 @@ namespace GitHub.Runner.Worker
                     await Task.WhenAny(_jobServerQueue.JobRecordUpdated.Task, Task.Delay(1000));
                 }
 
-                // Wait for DAP debugger client connection and handshake after "Set up job"
-                // so the job page shows the setup step before we block on the debugger
-                if (dapDebugger != null)
-                {
-                    try
-                    {
-                        await dapDebugger.WaitUntilReadyAsync();
-                        AddDebuggerConnectionTelemetry(jobContext, "Connected");
-                    }
-                    catch (OperationCanceledException) when (jobRequestCancellationToken.IsCancellationRequested)
-                    {
-                        Trace.Info("Job was cancelled before debugger client connected.");
-                        AddDebuggerConnectionTelemetry(jobContext, "Canceled");
-                        jobContext.Error("Job was cancelled before debugger client connected.");
-                        return await CompleteJobAsync(server, jobContext, message, TaskResult.Canceled);
-                    }
-                    catch (Exception ex)
-                    {
-                        Trace.Error($"DAP debugger failed to become ready: {ex.Message}");
-                        AddDebuggerConnectionTelemetry(jobContext, $"Failed: {ex.Message}");
-
-                        // If debugging was requested but the debugger is not available, fail the job
-                        jobContext.Error("The debugger failed to start or no debugger client connected in time.");
-                        return await CompleteJobAsync(server, jobContext, message, TaskResult.Failed);
-                    }
-                }
-
                 // Run all job steps
                 Trace.Info("Run all job steps.");
                 var stepsRunner = HostContext.GetService<IStepsRunner>();
@@ -309,11 +260,6 @@ namespace GitHub.Runner.Worker
                     runnerShutdownRegistration = null;
                 }
 
-                if (dapDebugger != null)
-                {
-                    await dapDebugger.OnJobCompletedAsync();
-                }
-
                 await ShutdownQueue(throwOnFailure: false);
             }
         }
@@ -495,15 +441,6 @@ namespace GitHub.Runner.Worker
             throw new AggregateException(exceptions);
         }
 
-        private static void AddDebuggerConnectionTelemetry(IExecutionContext jobContext, string result)
-        {
-            jobContext.Global.JobTelemetry.Add(new JobTelemetry
-            {
-                Type = JobTelemetryType.General,
-                Message = $"{DebuggerConnectionTelemetryPrefix}: {result}"
-            });
-        }
-
         private void MaskTelemetrySecrets(List<JobTelemetry> jobTelemetry)
         {
             foreach (var telemetryItem in jobTelemetry)

src/Test/L0/HostContextL0.cs

@@ -299,6 +299,52 @@ namespace GitHub.Runner.Common.Tests
             }
         }
 
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetDirectoryRootReturnsCachedValue()
+        {
+            try
+            {
+                Setup();
+
+                // Call GetDirectory(Root) twice — should return the same reference
+                var root1 = _hc.GetDirectory(WellKnownDirectory.Root);
+                var root2 = _hc.GetDirectory(WellKnownDirectory.Root);
+
+                Assert.NotNull(root1);
+                Assert.Equal(root1, root2);
+                Assert.True(Directory.Exists(root1));
+            }
+            finally
+            {
+                Teardown();
+            }
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetDirectoryDerivedPathsUseRootCasing()
+        {
+            try
+            {
+                Setup();
+
+                var root = _hc.GetDirectory(WellKnownDirectory.Root);
+                var diag = _hc.GetDirectory(WellKnownDirectory.Diag);
+                var externals = _hc.GetDirectory(WellKnownDirectory.Externals);
+
+                // Diag and Externals should start with the same Root prefix
+                Assert.StartsWith(root, diag);
+                Assert.StartsWith(root, externals);
+            }
+            finally
+            {
+                Teardown();
+            }
+        }
+
         private void Setup([CallerMemberName] string testName = "")
         {
             _tokenSource = new CancellationTokenSource();

src/Test/L0/Util/PathUtilL0.cs

@@ -0,0 +1,151 @@
+using GitHub.Runner.Sdk;
+using System.IO;
+using System.Runtime.InteropServices;
+using Xunit;
+
+namespace GitHub.Runner.Common.Tests.Util
+{
+    public sealed class PathUtilL0
+    {
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetCanonicalPath_ReturnsPath_WhenDirectoryDoesNotExist()
+        {
+            var fakePath = Path.Combine(Path.GetTempPath(), "nonexistent_" + Path.GetRandomFileName());
+            var result = PathUtil.GetCanonicalPath(fakePath);
+            Assert.Equal(fakePath, result);
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetCanonicalPath_ReturnsPath_WhenNull()
+        {
+            Assert.Null(PathUtil.GetCanonicalPath(null));
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetCanonicalPath_ReturnsEmpty_WhenEmpty()
+        {
+            Assert.Equal(string.Empty, PathUtil.GetCanonicalPath(string.Empty));
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetCanonicalPath_ReturnsValidPath_ForExistingDirectory()
+        {
+            var tempDir = Path.Combine(Path.GetTempPath(), "pathutil_test_" + Path.GetRandomFileName());
+            try
+            {
+                Directory.CreateDirectory(tempDir);
+                var result = PathUtil.GetCanonicalPath(tempDir);
+                Assert.NotNull(result);
+                Assert.True(Directory.Exists(result));
+            }
+            finally
+            {
+                if (Directory.Exists(tempDir))
+                {
+                    Directory.Delete(tempDir);
+                }
+            }
+        }
+
+#if OS_WINDOWS
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetCanonicalPath_NormalizesDriveLetter_OnWindows()
+        {
+            var tempDir = Path.GetTempPath().TrimEnd(Path.DirectorySeparatorChar);
+
+            // Skip if temp is a UNC path (no drive letter to normalize)
+            if (tempDir.StartsWith(@"\\"))
+            {
+                return;
+            }
+
+            // Force lowercase drive letter
+            var lowerCased = char.ToLower(tempDir[0]) + tempDir.Substring(1);
+
+            var result = PathUtil.GetCanonicalPath(lowerCased);
+
+            // The canonical path should have an uppercase drive letter
+            Assert.True(char.IsUpper(result[0]),
+                $"Expected uppercase drive letter but got: {result}");
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetCanonicalPath_NormalizesFolderCasing_OnWindows()
+        {
+            // Create a directory with known casing, then query with wrong casing
+            var basePath = Path.GetTempPath();
+            if (basePath.StartsWith(@"\\"))
+            {
+                return; // Skip UNC
+            }
+
+            var realName = "PathUtilTest_MiXeDcAsE_" + Path.GetRandomFileName();
+            var realDir = Path.Combine(basePath, realName);
+            try
+            {
+                Directory.CreateDirectory(realDir);
+
+                // Query with all-lowercase version
+                var wrongCased = Path.Combine(basePath, realName.ToLowerInvariant());
+
+                var result = PathUtil.GetCanonicalPath(wrongCased);
+
+                // The canonical result should contain the original mixed-case name
+                Assert.Contains(realName, result);
+            }
+            finally
+            {
+                if (Directory.Exists(realDir))
+                {
+                    Directory.Delete(realDir);
+                }
+            }
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetCanonicalPath_IsIdempotent_OnWindows()
+        {
+            // Calling GetCanonicalPath twice should return the same result
+            var tempDir = Path.GetTempPath().TrimEnd(Path.DirectorySeparatorChar);
+            var first = PathUtil.GetCanonicalPath(tempDir);
+            var second = PathUtil.GetCanonicalPath(first);
+            Assert.Equal(first, second);
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Common")]
+        public void GetCanonicalPath_ReturnsSameResult_RegardlessOfInputCasing_OnWindows()
+        {
+            var tempDir = Path.GetTempPath().TrimEnd(Path.DirectorySeparatorChar);
+            if (tempDir.StartsWith(@"\\"))
+            {
+                return; // Skip UNC
+            }
+
+            var upper = tempDir.ToUpperInvariant();
+            var lower = tempDir.ToLowerInvariant();
+
+            var resultUpper = PathUtil.GetCanonicalPath(upper);
+            var resultLower = PathUtil.GetCanonicalPath(lower);
+
+            // Both should resolve to the same canonical path
+            Assert.Equal(resultUpper, resultLower);
+        }
+#endif
+    }
+}

src/Test/L0/Worker/DapDebuggerL0.cs

@@ -744,14 +744,32 @@ namespace GitHub.Runner.Common.Tests.Worker
                 await ReadDapMessageAsync(stream, TimeSpan.FromSeconds(5));
                 await waitTask;
 
-                // Complete the job — events are sent via OnJobCompletedAsync
-                await _debugger.OnJobCompletedAsync();
+                // Complete the job — OnJobCompletedAsync pauses when stepping,
+                // so run it in the background and send continue to unblock.
+                var completedTask = _debugger.OnJobCompletedAsync();
 
-                var msg1 = await ReadDapMessageAsync(stream, TimeSpan.FromSeconds(5));
-                var msg2 = await ReadDapMessageAsync(stream, TimeSpan.FromSeconds(5));
+                // Read the stopped event from the pause
+                var stoppedMsg = await ReadDapMessageAsync(stream, TimeSpan.FromSeconds(5));
+                Assert.Contains("\"event\":\"stopped\"", stoppedMsg);
 
-                // Both events should arrive (order may vary)
-                var combined = msg1 + msg2;
+                // Send continue to unblock the pause
+                await SendRequestAsync(stream, new Request
+                {
+                    Seq = 2,
+                    Type = "request",
+                    Command = "continue"
+                });
+
+                await completedTask;
+
+                // Read remaining messages — continue response + continued event + terminated + exited
+                var allMessages = new System.Text.StringBuilder();
+                for (int i = 0; i < 4; i++)
+                {
+                    allMessages.Append(await ReadDapMessageAsync(stream, TimeSpan.FromSeconds(5)));
+                }
+
+                var combined = allMessages.ToString();
                 Assert.Contains("\"event\":\"terminated\"", combined);
                 Assert.Contains("\"event\":\"exited\"", combined);
             }
@@ -809,5 +827,45 @@ namespace GitHub.Runner.Common.Tests.Worker
                 });
             }
         }
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async Task WaitForCommandAsyncUnblocksOnCancellationDuringWait()
+        {
+            using (CreateTestContext())
+            {
+                var port = GetFreePort();
+                using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(10));
+                var jobContext = CreateJobContextWithTunnel(cts.Token, port);
+                await _debugger.StartAsync(jobContext.Object);
+
+                var waitTask = _debugger.WaitUntilReadyAsync();
+                using var client = await ConnectClientAsync(port);
+                var stream = client.GetStream();
+                await SendRequestAsync(stream, new Request
+                {
+                    Seq = 1,
+                    Type = "request",
+                    Command = "configurationDone"
+                });
+
+                await ReadDapMessageAsync(stream, TimeSpan.FromSeconds(5));
+                await waitTask;
+
+                // Start OnJobCompletedAsync — it will pause because _pauseOnNextStep is true
+                var completedTask = _debugger.OnJobCompletedAsync();
+
+                // Read the stopped event
+                var stoppedMsg = await ReadDapMessageAsync(stream, TimeSpan.FromSeconds(5));
+                Assert.Contains("\"event\":\"stopped\"", stoppedMsg);
+
+                // Cancel the job while waiting — should unblock the pause
+                cts.Cancel();
+
+                // OnJobCompletedAsync should complete without hanging
+                var finished = await Task.WhenAny(completedTask, Task.Delay(TimeSpan.FromSeconds(5)));
+                Assert.Equal(completedTask, finished);
+            }
+        }
     }
 }

src/Test/L0/Worker/JobExtensionL0.cs

@@ -760,5 +760,171 @@ namespace GitHub.Runner.Common.Tests.Worker
             Environment.SetEnvironmentVariable("RUNNER_ENVIRONMENT", null);
             Environment.SetEnvironmentVariable("GITHUB_ACTIONS_IMAGE_GEN_ENABLED", null);
         }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async Task DebuggerStartedInSetupJobWhenEnabled()
+        {
+            using (TestHostContext hc = CreateTestContext())
+            {
+                var jobExtension = new JobExtension();
+                jobExtension.Initialize(hc);
+
+                // Enable debugger on the message
+                _message.EnableDebugger = true;
+                _message.DebuggerTunnel = new Pipelines.DebuggerTunnelInfo
+                {
+                    TunnelId = "test-tunnel",
+                    ClusterId = "test-cluster",
+                    HostToken = "test-token",
+                    Port = 9229
+                };
+
+                // Re-initialize the execution context so it picks up debugger config
+                _jobEc = new Runner.Worker.ExecutionContext();
+                _jobEc.Initialize(hc);
+                _jobEc.InitializeJob(_message, _tokenSource.Token);
+
+                // Set up mock debugger
+                var mockDebugger = new Mock<IDapDebugger>();
+                mockDebugger.Setup(x => x.StartAsync(It.IsAny<IExecutionContext>())).Returns(Task.CompletedTask);
+                mockDebugger.Setup(x => x.WaitUntilReadyAsync()).Returns(Task.CompletedTask);
+                hc.SetSingleton(mockDebugger.Object);
+
+                _actionManager.Setup(x => x.PrepareActionsAsync(It.IsAny<IExecutionContext>(), It.IsAny<IEnumerable<Pipelines.JobStep>>(), It.IsAny<Guid>()))
+                              .Returns(Task.FromResult(new PrepareResult(new List<JobExtensionRunner>(), new Dictionary<Guid, IActionRunner>())));
+
+                List<IStep> result = await jobExtension.InitializeJob(_jobEc, _message);
+
+                // Verify DAP debugger was started and waited on
+                mockDebugger.Verify(x => x.StartAsync(It.IsAny<IExecutionContext>()), Times.Once);
+                mockDebugger.Verify(x => x.WaitUntilReadyAsync(), Times.Once);
+
+                // Verify steps are still returned correctly
+                Assert.Equal(5, result.Count);
+            }
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async Task DebuggerNotStartedInSetupJobWhenDisabled()
+        {
+            using (TestHostContext hc = CreateTestContext())
+            {
+                var jobExtension = new JobExtension();
+                jobExtension.Initialize(hc);
+
+                // Debugger NOT enabled on the message — should not be started
+
+                // Set up mock debugger (should NOT be called)
+                var mockDebugger = new Mock<IDapDebugger>();
+                hc.SetSingleton(mockDebugger.Object);
+
+                _actionManager.Setup(x => x.PrepareActionsAsync(It.IsAny<IExecutionContext>(), It.IsAny<IEnumerable<Pipelines.JobStep>>(), It.IsAny<Guid>()))
+                              .Returns(Task.FromResult(new PrepareResult(new List<JobExtensionRunner>(), new Dictionary<Guid, IActionRunner>())));
+
+                List<IStep> result = await jobExtension.InitializeJob(_jobEc, _message);
+
+                // Verify DAP debugger was NOT started during setup job
+                mockDebugger.Verify(x => x.StartAsync(It.IsAny<IExecutionContext>()), Times.Never);
+                mockDebugger.Verify(x => x.WaitUntilReadyAsync(), Times.Never);
+
+                Assert.Equal(5, result.Count);
+            }
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async Task DebuggerCleanedUpInFinalizeJob()
+        {
+            using (TestHostContext hc = CreateTestContext())
+            {
+                var jobExtension = new JobExtension();
+                jobExtension.Initialize(hc);
+
+                // Enable debugger on the message
+                _message.EnableDebugger = true;
+                _message.DebuggerTunnel = new Pipelines.DebuggerTunnelInfo
+                {
+                    TunnelId = "test-tunnel",
+                    ClusterId = "test-cluster",
+                    HostToken = "test-token",
+                    Port = 9229
+                };
+
+                // Re-initialize the execution context so it picks up debugger config
+                _jobEc = new Runner.Worker.ExecutionContext();
+                _jobEc.Initialize(hc);
+                _jobEc.InitializeJob(_message, _tokenSource.Token);
+
+                // Set up mock debugger
+                var mockDebugger = new Mock<IDapDebugger>();
+                mockDebugger.Setup(x => x.StartAsync(It.IsAny<IExecutionContext>())).Returns(Task.CompletedTask);
+                mockDebugger.Setup(x => x.WaitUntilReadyAsync()).Returns(Task.CompletedTask);
+                mockDebugger.Setup(x => x.OnJobCompletedAsync()).Returns(Task.CompletedTask);
+                hc.SetSingleton(mockDebugger.Object);
+
+                _actionManager.Setup(x => x.PrepareActionsAsync(It.IsAny<IExecutionContext>(), It.IsAny<IEnumerable<Pipelines.JobStep>>(), It.IsAny<Guid>()))
+                              .Returns(Task.FromResult(new PrepareResult(new List<JobExtensionRunner>(), new Dictionary<Guid, IActionRunner>())));
+
+                // Run InitializeJob to start the debugger
+                await jobExtension.InitializeJob(_jobEc, _message);
+
+                // Run FinalizeJob — should pause (inside OnJobCompletedAsync) then clean up
+                await jobExtension.FinalizeJob(_jobEc, _message, DateTime.UtcNow);
+
+                // Verify OnJobCompletedAsync was called (it handles pause + cleanup)
+                mockDebugger.Verify(x => x.OnJobCompletedAsync(), Times.Once);
+            }
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async Task FinalizeJobHandlesDebuggerCleanupException()
+        {
+            using (TestHostContext hc = CreateTestContext())
+            {
+                var jobExtension = new JobExtension();
+                jobExtension.Initialize(hc);
+
+                // Enable debugger on the message
+                _message.EnableDebugger = true;
+                _message.DebuggerTunnel = new Pipelines.DebuggerTunnelInfo
+                {
+                    TunnelId = "test-tunnel",
+                    ClusterId = "test-cluster",
+                    HostToken = "test-token",
+                    Port = 9229
+                };
+
+                // Re-initialize the execution context so it picks up debugger config
+                _jobEc = new Runner.Worker.ExecutionContext();
+                _jobEc.Initialize(hc);
+                _jobEc.InitializeJob(_message, _tokenSource.Token);
+
+                // Set up mock debugger — OnJobCompletedAsync throws
+                var mockDebugger = new Mock<IDapDebugger>();
+                mockDebugger.Setup(x => x.StartAsync(It.IsAny<IExecutionContext>())).Returns(Task.CompletedTask);
+                mockDebugger.Setup(x => x.WaitUntilReadyAsync()).Returns(Task.CompletedTask);
+                mockDebugger.Setup(x => x.OnJobCompletedAsync()).ThrowsAsync(new InvalidOperationException("tunnel disposed"));
+                mockDebugger.Setup(x => x.StopAsync()).Returns(Task.CompletedTask);
+                hc.SetSingleton(mockDebugger.Object);
+
+                _actionManager.Setup(x => x.PrepareActionsAsync(It.IsAny<IExecutionContext>(), It.IsAny<IEnumerable<Pipelines.JobStep>>(), It.IsAny<Guid>()))
+                              .Returns(Task.FromResult(new PrepareResult(new List<JobExtensionRunner>(), new Dictionary<Guid, IActionRunner>())));
+
+                await jobExtension.InitializeJob(_jobEc, _message);
+
+                // FinalizeJob should not throw even when OnJobCompletedAsync throws
+                await jobExtension.FinalizeJob(_jobEc, _message, DateTime.UtcNow);
+
+                mockDebugger.Verify(x => x.OnJobCompletedAsync(), Times.Once);
+                mockDebugger.Verify(x => x.StopAsync(), Times.Once);
+            }
+        }
     }
 }