diff --git a/src/ClaudeDo.Worker/Program.cs b/src/ClaudeDo.Worker/Program.cs
index fde7e44a..1268c3ad 100644
--- a/src/ClaudeDo.Worker/Program.cs
+++ b/src/ClaudeDo.Worker/Program.cs
@@ -125,7 +125,8 @@ builder.Services.AddSingleton<ITaskStateService>(sp => new TaskStateService(
     sp.GetRequiredService<RunCancellationRegistry>(),
     sp.GetRequiredService<Func<IActiveMergeState>>(),
     sp.GetRequiredService<BaseDirtyChecker>(),
-    sp.GetRequiredService<ILogger<TaskStateService>>()));
+    sp.GetRequiredService<ILogger<TaskStateService>>(),
+    sp.GetRequiredService<TicketStatusSync>()));
 
 // Agent file management.
 var agentsDir = Path.Combine(ClaudeDo.Data.Paths.AppDataRoot(), "agents");
@@ -219,6 +220,7 @@ builder.Services.AddSingleton(new TicketPatStore(DpapiTokenStore.InAppData("tick
 builder.Services.AddSingleton<TicketSystemConfig>();
 builder.Services.AddHttpClient("tickets");
 builder.Services.AddSingleton<TicketClientFactory>();
+builder.Services.AddSingleton<TicketStatusSync>();
 
 if (cfg.OnlineInbox.Enabled)
 {
diff --git a/src/ClaudeDo.Worker/State/TaskStateService.cs b/src/ClaudeDo.Worker/State/TaskStateService.cs
index 2a683bb8..b58e70be 100644
--- a/src/ClaudeDo.Worker/State/TaskStateService.cs
+++ b/src/ClaudeDo.Worker/State/TaskStateService.cs
@@ -5,6 +5,7 @@ using ClaudeDo.Worker.Git;
 using ClaudeDo.Worker.Hub;
 using ClaudeDo.Worker.Planning;
 using ClaudeDo.Worker.Queue;
+using ClaudeDo.Worker.Tickets;
 using Microsoft.EntityFrameworkCore;
 using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
 
@@ -20,6 +21,7 @@ public sealed class TaskStateService : ITaskStateService
     private readonly Func<IActiveMergeState> _mergeState;
     private readonly BaseDirtyChecker _baseDirtyChecker;
     private readonly ILogger<TaskStateService> _logger;
+    private readonly TicketStatusSync _ticketSync;
 
     public TaskStateService(
         IDbContextFactory<ClaudeDoDbContext> dbFactory,
@@ -29,7 +31,8 @@ public sealed class TaskStateService : ITaskStateService
         RunCancellationRegistry runCancels,
         Func<IActiveMergeState> mergeState,
         BaseDirtyChecker baseDirtyChecker,
-        ILogger<TaskStateService> logger)
+        ILogger<TaskStateService> logger,
+        TicketStatusSync ticketSync)
     {
         _dbFactory = dbFactory;
         _broadcaster = broadcaster;
@@ -39,6 +42,7 @@ public sealed class TaskStateService : ITaskStateService
         _mergeState = mergeState;
         _baseDirtyChecker = baseDirtyChecker;
         _logger = logger;
+        _ticketSync = ticketSync;
     }
 
     public async Task<TransitionResult> EnqueueAsync(string taskId, CancellationToken ct)
@@ -59,7 +63,7 @@ public sealed class TaskStateService : ITaskStateService
             return new TransitionResult(false, "Task not found or already running.");
 
         _waker.Wake();
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
 
         // Heads-up only: a worktree forks from the commit tip (WorktreeManager.ResolveBaseCommitAsync),
         // not the working tree, so uncommitted changes sitting in the list's repo right now are
@@ -92,7 +96,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task already running or not found.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -112,7 +116,7 @@ public sealed class TaskStateService : ITaskStateService
         }
 
         await OnChildTerminalAsync(taskId, TaskStatus.Done);
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -129,7 +133,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task not running; cannot submit for review.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -149,7 +153,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task is not Idle or Failed; cannot submit for review.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -166,7 +170,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task not running; cannot submit for children.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -186,7 +190,7 @@ public sealed class TaskStateService : ITaskStateService
         }
 
         await OnChildTerminalAsync(taskId, TaskStatus.Done);
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -208,7 +212,7 @@ public sealed class TaskStateService : ITaskStateService
             return new TransitionResult(false, "Task is not waiting for review; cannot reject.");
 
         _waker.Wake();
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -224,7 +228,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task is not waiting for review; cannot park.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -265,7 +269,7 @@ public sealed class TaskStateService : ITaskStateService
         }
 
         await OnChildTerminalAsync(taskId, TaskStatus.Failed);
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -329,9 +333,9 @@ public sealed class TaskStateService : ITaskStateService
             _runCancels.TryCancel(childId);
 
         await OnChildTerminalAsync(taskId, TaskStatus.Cancelled);
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         foreach (var childId in cancelledChildIds)
-            await _broadcaster.TaskUpdated(childId);
+            await NotifyAsync(childId);
         return new TransitionResult(true, null);
     }
 
@@ -349,7 +353,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task is running; cannot reset.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -375,7 +379,7 @@ public sealed class TaskStateService : ITaskStateService
             return new TransitionResult(false, "Task not found.");
 
         if (status == TaskStatus.Queued) _waker.Wake();
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -396,7 +400,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task is running or no longer exists; cannot mark done.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -410,7 +414,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task is not Done; cannot unmark.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -426,7 +430,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task is not queued; cannot remove from queue.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -443,7 +447,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task not in plannable state.");
 
-        await _broadcaster.TaskUpdated(parentId);
+        await NotifyAsync(parentId);
         return new TransitionResult(true, null);
     }
 
@@ -464,7 +468,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "No active planning session.");
 
-        await _broadcaster.TaskUpdated(parentId);
+        await NotifyAsync(parentId);
         return new TransitionResult(true, null);
     }
 
@@ -478,7 +482,7 @@ public sealed class TaskStateService : ITaskStateService
         if (affected == 0)
             return new TransitionResult(false, "Task not found.");
 
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -493,7 +497,7 @@ public sealed class TaskStateService : ITaskStateService
             return new TransitionResult(false, "Task not found.");
 
         _waker.Wake();
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -537,7 +541,7 @@ public sealed class TaskStateService : ITaskStateService
 
         // Clearing a dependency may free up a Queued task the picker was skipping.
         if (dependsOnTaskId is null) _waker.Wake();
-        await _broadcaster.TaskUpdated(taskId);
+        await NotifyAsync(taskId);
         return new TransitionResult(true, null);
     }
 
@@ -672,6 +676,17 @@ public sealed class TaskStateService : ITaskStateService
             .ExecuteUpdateAsync(s => s
                 .SetProperty(t => t.Status, TaskStatus.WaitingForReview)
                 .SetProperty(t => t.Result, newResult), CancellationToken.None);
-        await _broadcaster.TaskUpdated(parentId);
+        await NotifyAsync(parentId);
+    }
+
+    /// <summary>
+    /// Der einzige Broadcast-Pfad dieser Klasse. Zusätzlich zum UI-Update meldet er den neuen
+    /// Status ans verknüpfte Ticket. Nie direkt _broadcaster.TaskUpdated aufrufen — sonst
+    /// fällt genau dieser Übergang aus dem Ticket-Sync heraus.
+    /// </summary>
+    private async Task NotifyAsync(string taskId)
+    {
+        await _broadcaster.TaskUpdated(taskId);
+        await _ticketSync.SyncAsync(taskId, CancellationToken.None);
     }
 }
diff --git a/src/ClaudeDo.Worker/Tickets/TicketStatusMap.cs b/src/ClaudeDo.Worker/Tickets/TicketStatusMap.cs
new file mode 100644
index 00000000..460b73f5
--- /dev/null
+++ b/src/ClaudeDo.Worker/Tickets/TicketStatusMap.cs
@@ -0,0 +1,36 @@
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Tickets;
+
+/// <summary>
+/// Reine Abbildung Task-Status → Ticket-Status. Ticket-Status im Bandel-System:
+/// 0 Keine, 1 Offen, 2 InBearbeitung, 3 Fertig, 4 Archiviert.
+/// </summary>
+public static class TicketStatusMap
+{
+    public const int InBearbeitung = 2;
+    public const int Fertig = 3;
+
+    private const string BandelPrefix = "bandel:";
+
+    /// <summary>
+    /// Zielstatus im Ticketsystem, oder null wenn dieser Task-Status nichts melden soll.
+    /// "Offen" (1) wird nie geschrieben: das ist der Eingangszustand. Failed/Cancelled lassen
+    /// das Ticket bewusst auf InBearbeitung stehen — die Arbeit ist angefangen, nicht zurückgegeben.
+    /// </summary>
+    public static int? ToTicketStatus(TaskStatus status) => status switch
+    {
+        TaskStatus.Running or TaskStatus.WaitingForReview => InBearbeitung,
+        TaskStatus.Done => Fertig,
+        _ => null,
+    };
+
+    /// <summary>Ticket-Id aus einem "bandel:&lt;id&gt;"-Ref, oder null bei jedem anderen Format.</summary>
+    public static int? ParseBandelTicketId(string? ticketRef)
+    {
+        if (string.IsNullOrWhiteSpace(ticketRef)) return null;
+        if (!ticketRef.StartsWith(BandelPrefix, StringComparison.OrdinalIgnoreCase)) return null;
+        var raw = ticketRef[BandelPrefix.Length..];
+        return int.TryParse(raw, out var id) && id > 0 ? id : null;
+    }
+}
diff --git a/src/ClaudeDo.Worker/Tickets/TicketStatusSync.cs b/src/ClaudeDo.Worker/Tickets/TicketStatusSync.cs
new file mode 100644
index 00000000..a1e69260
--- /dev/null
+++ b/src/ClaudeDo.Worker/Tickets/TicketStatusSync.cs
@@ -0,0 +1,79 @@
+using System.Collections.Concurrent;
+using ClaudeDo.Data;
+using Microsoft.EntityFrameworkCore;
+
+namespace ClaudeDo.Worker.Tickets;
+
+/// <summary>
+/// Meldet den Task-Status ans verknüpfte Ticket zurück. Hängt an genau einem Punkt im System:
+/// TaskStateService.NotifyAsync, dem einzigen Ort, an dem Statuswechsel zusammenlaufen.
+///
+/// Zwei Invarianten:
+///  * Wirft nie. Ein Ticketsystem-Ausfall darf keinen Statuswechsel und keine Queue anhalten.
+///  * Kostet nichts, wenn nichts eingerichtet ist — IsConfigured bricht vor jeder DB-Abfrage ab.
+/// </summary>
+public sealed class TicketStatusSync
+{
+    private readonly TicketSystemConfig _config;
+    private readonly TicketClientFactory _clients;
+    private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
+    private readonly ILogger<TicketStatusSync> _logger;
+
+    // taskId → zuletzt geschriebener Ticket-Status. Verhindert den redundanten PATCH bei
+    // Running → WaitingForReview (beide sind "InBearbeitung"). Bewusst nur im Prozessspeicher:
+    // nach einem Neustart ist ein überzähliger PATCH harmlos.
+    private readonly ConcurrentDictionary<string, int> _lastWritten = new();
+
+    public TicketStatusSync(
+        TicketSystemConfig config,
+        TicketClientFactory clients,
+        IDbContextFactory<ClaudeDoDbContext> dbFactory,
+        ILogger<TicketStatusSync> logger)
+    {
+        _config = config;
+        _clients = clients;
+        _dbFactory = dbFactory;
+        _logger = logger;
+    }
+
+    public async Task SyncAsync(string taskId, CancellationToken ct)
+    {
+        if (!_config.IsConfigured) return;
+
+        try
+        {
+            await using var ctx = await _dbFactory.CreateDbContextAsync(ct);
+            var row = await ctx.Tasks.AsNoTracking()
+                .Where(t => t.Id == taskId)
+                .Select(t => new { t.Status, t.TicketRef })
+                .FirstOrDefaultAsync(ct);
+
+            if (row?.TicketRef is null) return;
+
+            var ticketId = TicketStatusMap.ParseBandelTicketId(row.TicketRef);
+            if (ticketId is null) return;
+
+            var target = TicketStatusMap.ToTicketStatus(row.Status);
+            if (target is null) return;
+
+            if (_lastWritten.TryGetValue(taskId, out var previous) && previous == target.Value) return;
+
+            var client = _clients.Create();
+            if (client is null) return;
+
+            await client.SetStatusAsync(ticketId.Value, target.Value, ct);
+            _lastWritten[taskId] = target.Value;
+
+            _logger.LogInformation(
+                "Ticket {ticket_id} auf Status {ticket_status} gesetzt (Task {task_id})",
+                ticketId.Value, target.Value, taskId);
+        }
+        catch (Exception ex)
+        {
+            // Serilog Warn landet über BroadcastLogSink im Footer-Log-Strip.
+            _logger.LogWarning(ex,
+                "Ticket-Status für Task {task_id} konnte nicht geschrieben werden: {reason}",
+                taskId, ex.Message);
+        }
+    }
+}
diff --git a/tests/ClaudeDo.Worker.Tests/Infrastructure/TaskStateServiceBuilder.cs b/tests/ClaudeDo.Worker.Tests/Infrastructure/TaskStateServiceBuilder.cs
index d9595326..afcb75d7 100644
--- a/tests/ClaudeDo.Worker.Tests/Infrastructure/TaskStateServiceBuilder.cs
+++ b/tests/ClaudeDo.Worker.Tests/Infrastructure/TaskStateServiceBuilder.cs
@@ -1,9 +1,11 @@
 using ClaudeDo.Data;
+using ClaudeDo.Worker.Config;
 using ClaudeDo.Worker.Git;
 using ClaudeDo.Worker.Hub;
 using ClaudeDo.Worker.Planning;
 using ClaudeDo.Worker.Queue;
 using ClaudeDo.Worker.State;
+using ClaudeDo.Worker.Tickets;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.Logging.Abstractions;
 
@@ -31,6 +33,18 @@ public static class TaskStateServiceBuilder
         var waker = new CountingQueueWaker();
         var runCancels = new RunCancellationRegistry(NullLogger<RunCancellationRegistry>.Instance);
 
+        // Unconfigured on purpose: no base URL, no PAT file at this (unused) path — IsConfigured
+        // is false, so TicketStatusSync.SyncAsync short-circuits before touching the DB or the
+        // network. Tests that care about ticket sync build TicketStatusSync themselves.
+        var ticketConfig = new TicketSystemConfig(
+            new WorkerConfig(),
+            new TicketPatStore(new DpapiTokenStore(Path.Combine(Path.GetTempPath(), $"cdo-unused-pat-{Guid.NewGuid():N}"))));
+        var ticketSync = new TicketStatusSync(
+            ticketConfig,
+            new TicketClientFactory(ticketConfig, new NoopHttpClientFactory(), NullLogger<BandelTicketClient>.Instance),
+            dbFactory,
+            NullLogger<TicketStatusSync>.Instance);
+
         TaskStateService? state = null;
         var chain = new PlanningChainCoordinator(dbFactory, () => state!);
         state = new TaskStateService(
@@ -41,7 +55,8 @@ public static class TaskStateServiceBuilder
             runCancels,
             mergeState ?? (() => NoActiveMergeState.Instance),
             baseDirtyChecker ?? new BaseDirtyChecker(new ClaudeDo.Data.Git.GitService(), NullLogger<BaseDirtyChecker>.Instance),
-            NullLogger<TaskStateService>.Instance);
+            NullLogger<TaskStateService>.Instance,
+            ticketSync);
 
         return new Built(state, chain, hub, () => waker.Count, waker, runCancels);
     }
@@ -53,6 +68,14 @@ file sealed class NoActiveMergeState : IActiveMergeState
     public bool HasActiveMerge(string taskId) => false;
 }
 
+// Never actually invoked: TicketSystemConfig.IsConfigured is false in every TaskStateServiceBuilder
+// test, so TicketClientFactory.Create() returns null before this factory would be called.
+file sealed class NoopHttpClientFactory : IHttpClientFactory
+{
+    public HttpClient CreateClient(string name) => throw new InvalidOperationException(
+        "Unexpected: ticket sync is not configured in tests built via TaskStateServiceBuilder.");
+}
+
 public sealed class CountingQueueWaker : IQueueWaker
 {
     private int _count;
diff --git a/tests/ClaudeDo.Worker.Tests/Tickets/TicketStatusMapTests.cs b/tests/ClaudeDo.Worker.Tests/Tickets/TicketStatusMapTests.cs
new file mode 100644
index 00000000..762b18bd
--- /dev/null
+++ b/tests/ClaudeDo.Worker.Tests/Tickets/TicketStatusMapTests.cs
@@ -0,0 +1,46 @@
+using ClaudeDo.Worker.Tickets;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Tests.Tickets;
+
+public sealed class TicketStatusMapTests
+{
+    [Theory]
+    [InlineData(TaskStatus.Running, 2)]
+    [InlineData(TaskStatus.WaitingForReview, 2)]
+    [InlineData(TaskStatus.Done, 3)]
+    public void Maps_the_three_states_we_report(TaskStatus status, int expected)
+        => Assert.Equal(expected, TicketStatusMap.ToTicketStatus(status));
+
+    [Theory]
+    [InlineData(TaskStatus.Idle)]
+    [InlineData(TaskStatus.Queued)]
+    [InlineData(TaskStatus.WaitingForChildren)]
+    [InlineData(TaskStatus.Failed)]
+    [InlineData(TaskStatus.Cancelled)]
+    public void Everything_else_writes_nothing(TaskStatus status)
+        => Assert.Null(TicketStatusMap.ToTicketStatus(status));
+
+    [Fact]
+    public void Never_writes_Offen()
+    {
+        foreach (var status in Enum.GetValues<TaskStatus>())
+            Assert.NotEqual(1, TicketStatusMap.ToTicketStatus(status));
+    }
+
+    [Theory]
+    [InlineData("bandel:1234", 1234)]
+    [InlineData("BANDEL:7", 7)]
+    public void Parses_a_bandel_ref(string reference, int expected)
+        => Assert.Equal(expected, TicketStatusMap.ParseBandelTicketId(reference));
+
+    [Theory]
+    [InlineData(null)]
+    [InlineData("")]
+    [InlineData("1234")]
+    [InlineData("jira:ABC-1")]
+    [InlineData("bandel:")]
+    [InlineData("bandel:abc")]
+    public void Rejects_anything_else(string? reference)
+        => Assert.Null(TicketStatusMap.ParseBandelTicketId(reference));
+}
diff --git a/tests/ClaudeDo.Worker.Tests/Tickets/TicketStatusSyncTests.cs b/tests/ClaudeDo.Worker.Tests/Tickets/TicketStatusSyncTests.cs
new file mode 100644
index 00000000..56b4b891
--- /dev/null
+++ b/tests/ClaudeDo.Worker.Tests/Tickets/TicketStatusSyncTests.cs
@@ -0,0 +1,191 @@
+using System.Net;
+using System.Text.RegularExpressions;
+using ClaudeDo.Data;
+using ClaudeDo.Data.Models;
+using ClaudeDo.Worker;
+using ClaudeDo.Worker.Config;
+using ClaudeDo.Worker.Tests.Infrastructure;
+using ClaudeDo.Worker.Tickets;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Logging.Abstractions;
+using TaskStatus = ClaudeDo.Data.Models.TaskStatus;
+
+namespace ClaudeDo.Worker.Tests.Tickets;
+
+public sealed class TicketStatusSyncTests : IDisposable
+{
+    private readonly DbFixture _db = new();
+    private readonly TestDbContextFactory _factory;
+    private readonly string _listId = Guid.NewGuid().ToString();
+    private readonly List<string> _patDirs = new();
+    private int _numberSeed;
+
+    public TicketStatusSyncTests()
+    {
+        _factory = _db.CreateFactory();
+        using var ctx = _factory.CreateDbContext();
+        ctx.Lists.Add(new ListEntity
+        {
+            Id = _listId,
+            Name = "Test",
+            CreatedAt = DateTime.UtcNow,
+            DefaultCommitType = "chore",
+        });
+        ctx.SaveChanges();
+    }
+
+    public void Dispose()
+    {
+        _db.Dispose();
+        foreach (var dir in _patDirs)
+        {
+            try { Directory.Delete(dir, recursive: true); } catch { /* best effort */ }
+        }
+    }
+
+    [Fact]
+    public async Task Writes_InBearbeitung_when_the_task_starts_running()
+    {
+        var (sync, calls) = Harness(configured: true);
+        var taskId = await SeedTaskAsync(TaskStatus.Running, ticketRef: "bandel:12");
+
+        await sync.SyncAsync(taskId, CancellationToken.None);
+
+        Assert.Equal((12, 2), Assert.Single(calls));
+    }
+
+    [Fact]
+    public async Task Writes_Fertig_when_the_task_is_done()
+    {
+        var (sync, calls) = Harness(configured: true);
+        var taskId = await SeedTaskAsync(TaskStatus.Done, ticketRef: "bandel:12");
+
+        await sync.SyncAsync(taskId, CancellationToken.None);
+
+        Assert.Equal((12, 3), Assert.Single(calls));
+    }
+
+    [Fact]
+    public async Task Does_nothing_without_a_ticket_ref()
+    {
+        var (sync, calls) = Harness(configured: true);
+        var taskId = await SeedTaskAsync(TaskStatus.Running, ticketRef: null);
+
+        await sync.SyncAsync(taskId, CancellationToken.None);
+
+        Assert.Empty(calls);
+    }
+
+    [Fact]
+    public async Task Does_nothing_when_not_configured()
+    {
+        var (sync, calls) = Harness(configured: false);
+        var taskId = await SeedTaskAsync(TaskStatus.Running, ticketRef: "bandel:12");
+
+        await sync.SyncAsync(taskId, CancellationToken.None);
+
+        Assert.Empty(calls);
+    }
+
+    [Fact]
+    public async Task Does_nothing_for_an_unmapped_status()
+    {
+        var (sync, calls) = Harness(configured: true);
+        var taskId = await SeedTaskAsync(TaskStatus.Queued, ticketRef: "bandel:12");
+
+        await sync.SyncAsync(taskId, CancellationToken.None);
+
+        Assert.Empty(calls);
+    }
+
+    [Fact]
+    public async Task Skips_the_redundant_patch_from_Running_to_WaitingForReview()
+    {
+        var (sync, calls) = Harness(configured: true);
+        var taskId = await SeedTaskAsync(TaskStatus.Running, ticketRef: "bandel:12");
+
+        await sync.SyncAsync(taskId, CancellationToken.None);
+        await SetStatusAsync(taskId, TaskStatus.WaitingForReview);
+        await sync.SyncAsync(taskId, CancellationToken.None);
+
+        Assert.Single(calls);   // beide mappen auf 2 — nur ein PATCH
+    }
+
+    [Fact]
+    public async Task Api_failure_does_not_propagate()
+    {
+        var (sync, _) = Harness(configured: true, throwOnPatch: true);
+        var taskId = await SeedTaskAsync(TaskStatus.Done, ticketRef: "bandel:12");
+
+        // Darf NICHT werfen: ein Ticketsystem-Ausfall hält die Queue nicht an.
+        await sync.SyncAsync(taskId, CancellationToken.None);
+    }
+
+    // ── Helfer ──────────────────────────────────────────────────────────────
+
+    private sealed class StubHttpClientFactory : IHttpClientFactory
+    {
+        private readonly StubHandler _handler;
+        public StubHttpClientFactory(StubHandler handler) => _handler = handler;
+        public HttpClient CreateClient(string name) => new(_handler);
+    }
+
+    private (TicketStatusSync Sync, List<(int TicketId, int StatusId)> Calls) Harness(
+        bool configured, bool throwOnPatch = false)
+    {
+        var calls = new List<(int TicketId, int StatusId)>();
+        StubHandler handler = null!;
+        handler = new StubHandler(request =>
+        {
+            if (throwOnPatch)
+                return (HttpStatusCode.InternalServerError, """{"success":false,"data":null,"message":"boom"}""");
+
+            var urlMatch = Regex.Match(request.RequestUri!.AbsolutePath, @"/api/Ticket/(\d+)/status");
+            var ticketId = int.Parse(urlMatch.Groups[1].Value);
+            var bodyMatch = Regex.Match(handler.Bodies[^1], "\"statusId\":(\\d+)");
+            var statusId = int.Parse(bodyMatch.Groups[1].Value);
+            calls.Add((ticketId, statusId));
+
+            return (HttpStatusCode.OK, """{"success":true,"data":{},"message":"ok"}""");
+        });
+
+        var patDir = Path.Combine(Path.GetTempPath(), "cdo-ticketsync-" + Guid.NewGuid().ToString("N"));
+        _patDirs.Add(patDir);
+        var patStore = new TicketPatStore(new DpapiTokenStore(Path.Combine(patDir, "ticket.pat")));
+        var worker = new WorkerConfig();
+        if (configured)
+        {
+            worker.TicketApiBaseUrl = "http://api.local";
+            patStore.Store.Save("tsp_x");
+        }
+
+        var config = new TicketSystemConfig(worker, patStore);
+        var clients = new TicketClientFactory(config, new StubHttpClientFactory(handler), NullLogger<BandelTicketClient>.Instance);
+        var sync = new TicketStatusSync(config, clients, _factory, NullLogger<TicketStatusSync>.Instance);
+        return (sync, calls);
+    }
+
+    private async Task<string> SeedTaskAsync(TaskStatus status, string? ticketRef)
+    {
+        var id = Guid.NewGuid().ToString();
+        await using var ctx = _factory.CreateDbContext();
+        ctx.Tasks.Add(new TaskEntity
+        {
+            Id = id,
+            ListId = _listId,
+            Title = "task",
+            Number = ++_numberSeed,
+            Status = status,
+            CreatedAt = DateTime.UtcNow,
+            TicketRef = ticketRef,
+        });
+        await ctx.SaveChangesAsync();
+        return id;
+    }
+
+    private async Task SetStatusAsync(string taskId, TaskStatus status)
+    {
+        await using var ctx = _factory.CreateDbContext();
+        await ctx.Tasks.Where(t => t.Id == taskId).ExecuteUpdateAsync(s => s.SetProperty(t => t.Status, status));
+    }
+}