diff --git a/services/domain/Big.Tests/Fakes.cs b/services/domain/Big.Tests/Fakes.cs
index cf0a37d..bfd0a54 100644
--- a/services/domain/Big.Tests/Fakes.cs
+++ b/services/domain/Big.Tests/Fakes.cs
@@ -41,6 +41,29 @@ internal sealed class FakeWorkflowClient(string processInstanceId = "proc-1", Ac
     }
 }
 
+/// <summary>A fake user-task client for the werkbak/decision use cases: returns a scripted set of
+/// open beoordeling tasks and records claim/complete calls.</summary>
+internal sealed class FakeUserTaskClient(IReadOnlyList<BeoordelingTask> open) : IUserTaskClient
+{
+    public (string TaskId, string Behandelaar)? Claimed { get; private set; }
+    public (string TaskId, BeoordelingsBesluit Besluit)? Completed { get; private set; }
+
+    public Task<IReadOnlyList<BeoordelingTask>> GetOpenBeoordelingenAsync(CancellationToken ct = default)
+        => Task.FromResult(open);
+
+    public Task ClaimAsync(string taskId, string behandelaar, CancellationToken ct = default)
+    {
+        Claimed = (taskId, behandelaar);
+        return Task.CompletedTask;
+    }
+
+    public Task CompleteBeoordelingAsync(string taskId, BeoordelingsBesluit besluit, CancellationToken ct = default)
+    {
+        Completed = (taskId, besluit);
+        return Task.CompletedTask;
+    }
+}
+
 /// <summary>A fake ACL client that records the bsn it was asked to open a zaak for and returns a
 /// fixed zaak URL.</summary>
 internal sealed class FakeAclClient(Uri? zaakUrl = null) : IAclClient
diff --git a/services/domain/Big.Tests/WerkbakTests.cs b/services/domain/Big.Tests/WerkbakTests.cs
new file mode 100644
index 0000000..bfbf182
--- /dev/null
+++ b/services/domain/Big.Tests/WerkbakTests.cs
@@ -0,0 +1,49 @@
+using Big.Application;
+using Big.Domain;
+
+namespace Big.Tests;
+
+/// <summary>
+/// The werkbak query (S-12c): the behandelaar's list of registrations awaiting beoordeling. It reads
+/// the open Beoordelen tasks from the workflow engine (§8.2) and enriches each with its registration
+/// (bsn + status) from the store. A task whose registration is unknown is skipped defensively.
+/// </summary>
+public class WerkbakTests
+{
+    [Fact]
+    public async Task Lists_an_item_per_open_beoordeling_enriched_from_the_registration()
+    {
+        var store = new FakeRegistrationStore();
+        var registration = Registration.Submit("123456782");
+        registration.AttachZaak(FakeAclClient.DefaultZaakUrl);
+        registration.TakeIntoBehandeling();
+        store.Seed(registration);
+        var tasks = new FakeUserTaskClient([new BeoordelingTask("task-1", registration.Id)]);
+        var werkbak = new Werkbak(tasks, store);
+
+        var items = await werkbak.GetAsync();
+
+        var item = Assert.Single(items);
+        Assert.Equal(registration.Id.ToString(), item.RegistrationId);
+        Assert.Equal("123456782", item.Bsn);
+        Assert.Equal("InBehandeling", item.Status);
+    }
+
+    [Fact]
+    public async Task Is_empty_when_no_beoordelingen_are_open()
+    {
+        var werkbak = new Werkbak(new FakeUserTaskClient([]), new FakeRegistrationStore());
+
+        Assert.Empty(await werkbak.GetAsync());
+    }
+
+    [Fact]
+    public async Task Skips_a_task_whose_registration_is_unknown()
+    {
+        // Defensive: the werkbak never invents an item for a task the domain has no aggregate for.
+        var tasks = new FakeUserTaskClient([new BeoordelingTask("task-1", RegistrationId.New())]);
+        var werkbak = new Werkbak(tasks, new FakeRegistrationStore());
+
+        Assert.Empty(await werkbak.GetAsync());
+    }
+}