diff --git a/backend/Controllers/DashboardController.cs b/backend/Controllers/DashboardController.cs
index 770ddf8..199c8c4 100644
--- a/backend/Controllers/DashboardController.cs
+++ b/backend/Controllers/DashboardController.cs
@@ -1,3 +1,5 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Mvc;
 using Nexus.Api.Data;
 using Nexus.Api.Models;
@@ -5,9 +7,13 @@ using Nexus.Api.Services;
 
 namespace Nexus.Api.Controllers;
 
+[Authorize]
 [ApiController]
 [Route("api/dashboard")]
-public class DashboardController(IDashboardService dashboardService, ITaskService taskService) : ControllerBase
+public class DashboardController(
+    IDashboardService dashboardService,
+    ITaskService taskService,
+    IHttpContextAccessor httpContextAccessor) : ControllerBase
 {
     [HttpGet("status")]
     public async Task<DashboardStatus> GetStatus()
@@ -115,9 +121,16 @@ public class DashboardController(IDashboardService dashboardService, ITaskServic
         if (string.IsNullOrWhiteSpace(request.Title))
             return BadRequest(new { error = "Title is required." });
 
-        var task = await taskService.CreateDashboardTaskAsync(
-            request.Title, request.Detail, request.Source, request.Priority, request.AssignedTo, ct);
-        return Created($"/api/dashboard/tasks/{task.Id}", MapToDto(task));
+        try
+        {
+            var task = await taskService.CreateDashboardTaskAsync(
+                request.Title, request.Detail, request.Source, request.Priority, request.AssignedTo, request.ParentTaskId, ct);
+            return Created($"/api/dashboard/tasks/{task.Id}", MapToDto(task));
+        }
+        catch (ArgumentException ex)
+        {
+            return BadRequest(new { error = ex.Message });
+        }
     }
 
     [HttpPut("tasks/{id:guid}")]
@@ -125,7 +138,7 @@ public class DashboardController(IDashboardService dashboardService, ITaskServic
         Guid id, [FromBody] UpdateDashboardTaskRequest request, CancellationToken ct)
     {
         var result = await taskService.UpdateDashboardTaskAsync(
-            id, request.Title, request.Detail, request.Source, request.Priority, request.AssignedTo, ct);
+            id, request.Title, request.Detail, request.Source, request.Priority, request.AssignedTo, request.DueDate, ct);
         return result.Outcome switch
         {
             TaskOperationOutcome.NotFound => NotFound(new { error = "Task not found." }),
@@ -149,6 +162,20 @@ public class DashboardController(IDashboardService dashboardService, ITaskServic
     public async Task<ActionResult<DashboardTaskDto>> UpdateTaskStatus(
         Guid id, [FromBody] UpdateDashboardTaskStatusRequest request, CancellationToken ct)
     {
+        // Bao review gate: Check if moving OUT of Review
+        var currentTask = await taskService.GetByIdAsync(id, ct);
+        if (currentTask is not null &&
+            string.Equals(currentTask.State, "Review", StringComparison.OrdinalIgnoreCase) &&
+            !string.Equals(request.Status, "Review", StringComparison.OrdinalIgnoreCase))
+        {
+            var user = httpContextAccessor.HttpContext?.User;
+            var isOwner = user?.IsInRole("Owner") == true ||
+                          user?.IsInRole("owner") == true ||
+                          user?.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value == "bao";
+            if (!isOwner)
+                return StatusCode(403, new { error = "Only the owner can move tasks out of Review." });
+        }
+
         var result = await taskService.UpdateStatusAsync(id, request.Status, ct);
         return result.Outcome switch
         {
@@ -171,6 +198,20 @@ public class DashboardController(IDashboardService dashboardService, ITaskServic
         if (string.IsNullOrWhiteSpace(request.State))
             return BadRequest(new { error = "State is required." });
 
+        // Bao review gate: Check if moving OUT of Review
+        var currentTask = await taskService.GetByIdAsync(id, ct);
+        if (currentTask is not null &&
+            string.Equals(currentTask.State, "Review", StringComparison.OrdinalIgnoreCase) &&
+            !string.Equals(request.State, "Review", StringComparison.OrdinalIgnoreCase))
+        {
+            var user = httpContextAccessor.HttpContext?.User;
+            var isOwner = user?.IsInRole("Owner") == true ||
+                          user?.IsInRole("owner") == true ||
+                          user?.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value == "bao";
+            if (!isOwner)
+                return StatusCode(403, new { error = "Only the owner can move tasks out of Review." });
+        }
+
         var result = await taskService.MoveTaskAsync(id, request.State, ct);
         return result.Outcome switch
         {
@@ -180,6 +221,33 @@ public class DashboardController(IDashboardService dashboardService, ITaskServic
         };
     }
 
+    // ── New Endpoints: Reset Stale, Children, Activity ──
+
+    [HttpPost("tasks/reset-stale")]
+    public async Task<ActionResult<ResetStaleResponse>> ResetStale(
+        [FromBody] ResetStaleRequest request, CancellationToken ct)
+    {
+        var threshold = TimeSpan.FromHours(Math.Max(1, request.StaleHours));
+        var count = await taskService.ResetStaleInProgressTasksAsync(threshold, ct);
+        return Ok(new ResetStaleResponse(count));
+    }
+
+    [HttpGet("tasks/{id:guid}/children")]
+    public async Task<ActionResult<List<DashboardTaskDto>>> GetChildren(Guid id, CancellationToken ct)
+    {
+        var children = await taskService.GetChildTasksAsync(id, ct);
+        return Ok(children.Select(MapToDto).ToList());
+    }
+
+    [HttpGet("tasks/{id:guid}/activity")]
+    public async Task<ActionResult<List<ActivityEvent>>> GetTaskActivity(Guid id, CancellationToken ct)
+    {
+        var events = await taskService.GetTaskActivityAsync(id, ct);
+        return Ok(events);
+    }
+
+    // ── Import ──
+
     [HttpPost("tasks/import-from-iris-todo")]
     public async Task<ActionResult<ImportResultDto>> ImportFromIrisTodo(
         [FromQuery] bool delete = false, CancellationToken ct = default)
@@ -189,5 +257,6 @@ public class DashboardController(IDashboardService dashboardService, ITaskServic
     }
 
     private static DashboardTaskDto MapToDto(WorkTask t) => new(
-        t.Id, t.Title, t.Detail, t.Source, t.State, t.Priority, t.AssignedTo, t.CreatedAt, t.UpdatedAt);
+        t.Id, t.Title, t.Detail, t.Source, t.State, t.Priority, t.AssignedTo,
+        t.ParentTaskId, t.DueDate, t.CreatedAt, t.UpdatedAt);
 }
diff --git a/backend/Controllers/HealthController.cs b/backend/Controllers/HealthController.cs
index 2575a06..1afcd4e 100644
--- a/backend/Controllers/HealthController.cs
+++ b/backend/Controllers/HealthController.cs
@@ -1,3 +1,4 @@
+using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.Extensions.Diagnostics.HealthChecks;
 using Nexus.Api.Integrations;
@@ -7,6 +8,7 @@ namespace Nexus.Api.Controllers;
 [ApiController]
 public class HealthController(IAgentRuntime runtime, HealthCheckService healthChecks) : ControllerBase
 {
+    [AllowAnonymous]
     [HttpGet("/health/live")]
     public IResult Live()
     {
diff --git a/backend/Controllers/NotificationsController.cs b/backend/Controllers/NotificationsController.cs
new file mode 100644
index 0000000..8ea9995
--- /dev/null
+++ b/backend/Controllers/NotificationsController.cs
@@ -0,0 +1,53 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Mvc;
+using Nexus.Api.Data;
+using Nexus.Api.Models;
+using Nexus.Api.Services;
+
+namespace Nexus.Api.Controllers;
+
+[Authorize]
+[ApiController]
+[Route("api/dashboard/notifications")]
+public class NotificationsController(INotificationService notificationService) : ControllerBase
+{
+    [HttpGet]
+    public async Task<ActionResult<List<NotificationDto>>> GetNotifications(
+        [FromQuery] string forUser = "bao",
+        [FromQuery] int limit = 50,
+        [FromQuery] bool unreadOnly = false,
+        CancellationToken ct = default)
+    {
+        var notifications = await notificationService.GetForUserAsync(forUser, limit, unreadOnly, ct);
+        return Ok(notifications.Select(MapToDto).ToList());
+    }
+
+    [HttpGet("unread-count")]
+    public async Task<ActionResult<UnreadCountDto>> GetUnreadCount(
+        [FromQuery] string forUser = "bao",
+        CancellationToken ct = default)
+    {
+        var count = await notificationService.GetUnreadCountAsync(forUser, ct);
+        return Ok(new UnreadCountDto(count));
+    }
+
+    [HttpPatch("{id:guid}/read")]
+    public async Task<ActionResult> MarkAsRead(Guid id, CancellationToken ct = default)
+    {
+        var ok = await notificationService.MarkAsReadAsync(id, ct);
+        return ok ? NoContent() : NotFound(new { error = "Notification not found." });
+    }
+
+    [HttpPatch("read-all")]
+    public async Task<ActionResult> MarkAllAsRead(
+        [FromQuery] string forUser = "bao",
+        CancellationToken ct = default)
+    {
+        var count = await notificationService.MarkAllAsReadAsync(forUser, ct);
+        return Ok(new { marked = count });
+    }
+
+    private static NotificationDto MapToDto(Notification n) => new(
+        n.Id, n.Type, n.Title, n.Message,
+        n.ForUser, n.TaskId, n.IsRead, n.CreatedAt);
+}
diff --git a/backend/Data/Entities.cs b/backend/Data/Entities.cs
index 1892dc1..e5c8941 100644
--- a/backend/Data/Entities.cs
+++ b/backend/Data/Entities.cs
@@ -18,6 +18,7 @@ public enum TaskState
 {
     Backlog,
     InProgress,
+    Delegated,
     Blocked,
     Done,
     Review
@@ -29,6 +30,7 @@ public static class TaskStateHelper
     {
         [TaskState.Backlog] = "Backlog",
         [TaskState.InProgress] = "In progress",
+        [TaskState.Delegated] = "Delegated",
         [TaskState.Blocked] = "Blocked",
         [TaskState.Done] = "Done",
         [TaskState.Review] = "Review"
@@ -38,6 +40,7 @@ public static class TaskStateHelper
     {
         ["Backlog"] = TaskState.Backlog,
         ["In progress"] = TaskState.InProgress,
+        ["Delegated"] = TaskState.Delegated,
         ["Blocked"] = TaskState.Blocked,
         ["Done"] = TaskState.Done,
         ["Review"] = TaskState.Review
@@ -48,13 +51,14 @@ public static class TaskStateHelper
     {
         ["Backlog"] = "Offen",
         ["In progress"] = "In Bearbeitung",
+        ["Delegated"] = "Delegiert",
         ["Review"] = "Review",
         ["Blocked"] = "Blockiert",
         ["Done"] = "Erledigt"
     };
 
     /// <summary>Valid task-state string values for API validation.</summary>
-    public static readonly string[] AllStates = ["Backlog", "In progress", "Blocked", "Done", "Review"];
+    public static readonly string[] AllStates = ["Backlog", "In progress", "Delegated", "Blocked", "Done", "Review"];
 
     /// <summary>Convert a TaskState enum to its API string representation.</summary>
     public static string ToStateString(this TaskState state) => StateToString[state];
@@ -88,6 +92,7 @@ public static class TaskStateHelper
         {
             "backlog" => "offen",
             "in progress" => "inProgress",
+            "delegated" => "delegated",
             "review" => "review",
             "blocked" => "blocked",
             "done" => "done",
@@ -104,6 +109,7 @@ public static class TaskStateHelper
         {
             "offen" => "Backlog",
             "inprogress" => "In progress",
+            "delegated" => "Delegated",
             "review" => "Review",
             "blocked" => "Blocked",
             "done" => "Done",
@@ -131,15 +137,32 @@ public sealed class WorkTask
     public string Priority { get; set; } = "Normal";
     public string Source { get; set; } = "bao";
     public string? AssignedTo { get; set; }
+    public Guid? ParentTaskId { get; set; }
+    public WorkTask? ParentTask { get; set; }
+    public ICollection<WorkTask> ChildTasks { get; set; } = new List<WorkTask>();
     public Guid? ProjectId { get; set; }
+    public DateTimeOffset? DueDate { get; set; }
     public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
     public DateTimeOffset UpdatedAt { get; set; } = DateTimeOffset.UtcNow;
 }
 
+public sealed class Notification
+{
+    public Guid Id { get; init; } = Guid.NewGuid();
+    public required string Type { get; set; }        // "task_assigned", "task_review", "task_blocked"
+    public required string Title { get; set; }        // "Neue Aufgabe: Memory-Index reparieren"
+    public string? Message { get; set; }              // Detailtext
+    public required string ForUser { get; set; }      // "bao" oder "iris"
+    public Guid? TaskId { get; set; }                 // Verknüpfte Task
+    public bool IsRead { get; set; } = false;
+    public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
+}
+
 public sealed class ActivityEvent
 {
     public long Id { get; init; }
     public required string Type { get; set; }
     public required string Message { get; set; }
+    public Guid? TaskId { get; set; }
     public DateTimeOffset CreatedAt { get; set; } = DateTimeOffset.UtcNow;
 }
diff --git a/backend/Data/Migrations/20260618214335_AddNotifications.Designer.cs b/backend/Data/Migrations/20260618214335_AddNotifications.Designer.cs
new file mode 100644
index 0000000..63991df
--- /dev/null
+++ b/backend/Data/Migrations/20260618214335_AddNotifications.Designer.cs
@@ -0,0 +1,311 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Nexus.Api.Data;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    [DbContext(typeof(NexusDbContext))]
+    [Migration("20260618214335_AddNotifications")]
+    partial class AddNotifications
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.8")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("Nexus.Api.Data.ActivityEvent", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Message")
+                        .IsRequired()
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("CreatedAt");
+
+                    b.HasIndex("TaskId");
+
+                    b.ToTable("Activity");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("DisplayName")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<DateTimeOffset?>("LastLoginAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("NormalizedEmail")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Role")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("NormalizedEmail")
+                        .IsUnique();
+
+                    b.ToTable("Users");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.Notification", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("ForUser")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<bool>("IsRead")
+                        .HasColumnType("boolean");
+
+                    b.Property<string>("Message")
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(240)
+                        .HasColumnType("character varying(240)");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ForUser", "IsRead", "CreatedAt");
+
+                    b.ToTable("Notifications");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.Project", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(160)
+                        .HasColumnType("character varying(160)");
+
+                    b.Property<int>("Progress")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("Status")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Projects");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.RefreshToken", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("ConcurrencyStamp")
+                        .IsConcurrencyToken()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTimeOffset>("ExpiresAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid>("FamilyId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("ReplacedByTokenHash")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<DateTimeOffset?>("RevokedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("TokenHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("uuid");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TokenHash")
+                        .IsUnique();
+
+                    b.HasIndex("UserId", "FamilyId");
+
+                    b.ToTable("RefreshTokens");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("AssignedTo")
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Detail")
+                        .HasMaxLength(2000)
+                        .HasColumnType("character varying(2000)");
+
+                    b.Property<DateTimeOffset?>("DueDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid?>("ParentTaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Priority")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<Guid?>("ProjectId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Source")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<string>("State")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(240)
+                        .HasColumnType("character varying(240)");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AssignedTo");
+
+                    b.HasIndex("ParentTaskId");
+
+                    b.HasIndex("Source");
+
+                    b.ToTable("Tasks");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.RefreshToken", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.NexusUser", "User")
+                        .WithMany("RefreshTokens")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.WorkTask", "ParentTask")
+                        .WithMany("ChildTasks")
+                        .HasForeignKey("ParentTaskId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.Navigation("ParentTask");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
+                {
+                    b.Navigation("RefreshTokens");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Navigation("ChildTasks");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}
diff --git a/backend/Data/Migrations/20260618214335_AddNotifications.cs b/backend/Data/Migrations/20260618214335_AddNotifications.cs
new file mode 100644
index 0000000..b68f736
--- /dev/null
+++ b/backend/Data/Migrations/20260618214335_AddNotifications.cs
@@ -0,0 +1,45 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddNotifications : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "Notifications",
+                columns: table => new
+                {
+                    Id = table.Column<Guid>(type: "uuid", nullable: false),
+                    Type = table.Column<string>(type: "character varying(60)", maxLength: 60, nullable: false),
+                    Title = table.Column<string>(type: "character varying(240)", maxLength: 240, nullable: false),
+                    Message = table.Column<string>(type: "character varying(1000)", maxLength: 1000, nullable: true),
+                    ForUser = table.Column<string>(type: "character varying(60)", maxLength: 60, nullable: false),
+                    TaskId = table.Column<Guid>(type: "uuid", nullable: true),
+                    IsRead = table.Column<bool>(type: "boolean", nullable: false),
+                    CreatedAt = table.Column<DateTimeOffset>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_Notifications", x => x.Id);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Notifications_ForUser_IsRead_CreatedAt",
+                table: "Notifications",
+                columns: new[] { "ForUser", "IsRead", "CreatedAt" });
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "Notifications");
+        }
+    }
+}
diff --git a/backend/Data/Migrations/20260618233000_AddTaskParentChild.cs b/backend/Data/Migrations/20260618233000_AddTaskParentChild.cs
new file mode 100644
index 0000000..4c20f17
--- /dev/null
+++ b/backend/Data/Migrations/20260618233000_AddTaskParentChild.cs
@@ -0,0 +1,49 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddTaskParentChild : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<Guid>(
+                name: "ParentTaskId",
+                table: "Tasks",
+                type: "uuid",
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Tasks_ParentTaskId",
+                table: "Tasks",
+                column: "ParentTaskId");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Tasks_Tasks_ParentTaskId",
+                table: "Tasks",
+                column: "ParentTaskId",
+                principalTable: "Tasks",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.SetNull);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Tasks_Tasks_ParentTaskId",
+                table: "Tasks");
+
+            migrationBuilder.DropIndex(
+                name: "IX_Tasks_ParentTaskId",
+                table: "Tasks");
+
+            migrationBuilder.DropColumn(
+                name: "ParentTaskId",
+                table: "Tasks");
+        }
+    }
+}
diff --git a/backend/Data/Migrations/20260618233001_AddTaskDueDate.cs b/backend/Data/Migrations/20260618233001_AddTaskDueDate.cs
new file mode 100644
index 0000000..fe37f4f
--- /dev/null
+++ b/backend/Data/Migrations/20260618233001_AddTaskDueDate.cs
@@ -0,0 +1,28 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddTaskDueDate : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<DateTimeOffset>(
+                name: "DueDate",
+                table: "Tasks",
+                type: "timestamp with time zone",
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "DueDate",
+                table: "Tasks");
+        }
+    }
+}
diff --git a/backend/Data/Migrations/20260618233002_AddActivityTaskReference.cs b/backend/Data/Migrations/20260618233002_AddActivityTaskReference.cs
new file mode 100644
index 0000000..914cc68
--- /dev/null
+++ b/backend/Data/Migrations/20260618233002_AddActivityTaskReference.cs
@@ -0,0 +1,37 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddActivityTaskReference : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<Guid>(
+                name: "TaskId",
+                table: "Activity",
+                type: "uuid",
+                nullable: true);
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Activity_TaskId",
+                table: "Activity",
+                column: "TaskId");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_Activity_TaskId",
+                table: "Activity");
+
+            migrationBuilder.DropColumn(
+                name: "TaskId",
+                table: "Activity");
+        }
+    }
+}
diff --git a/backend/Data/Migrations/20260618233003_AddDelegatedState.Designer.cs b/backend/Data/Migrations/20260618233003_AddDelegatedState.Designer.cs
new file mode 100644
index 0000000..59ec633
--- /dev/null
+++ b/backend/Data/Migrations/20260618233003_AddDelegatedState.Designer.cs
@@ -0,0 +1,270 @@
+// <auto-generated />
+using System;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+using Nexus.Api.Data;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    [DbContext(typeof(NexusDbContext))]
+    [Migration("20260618233003_AddDelegatedState")]
+    partial class AddDelegatedState
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder
+                .HasAnnotation("ProductVersion", "10.0.8")
+                .HasAnnotation("Relational:MaxIdentifierLength", 63);
+
+            NpgsqlModelBuilderExtensions.UseIdentityByDefaultColumns(modelBuilder);
+
+            modelBuilder.Entity("Nexus.Api.Data.ActivityEvent", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Message")
+                        .IsRequired()
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("CreatedAt");
+
+                    b.HasIndex("TaskId");
+
+                    b.ToTable("Activity");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("DisplayName")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("character varying(100)");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<DateTimeOffset?>("LastLoginAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("NormalizedEmail")
+                        .IsRequired()
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Role")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("NormalizedEmail")
+                        .IsUnique();
+
+                    b.ToTable("Users");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.Project", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Description")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(160)
+                        .HasColumnType("character varying(160)");
+
+                    b.Property<int>("Progress")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("Status")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.ToTable("Projects");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.RefreshToken", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<Guid>("ConcurrencyStamp")
+                        .IsConcurrencyToken()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<DateTimeOffset>("ExpiresAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid>("FamilyId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("ReplacedByTokenHash")
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<DateTimeOffset?>("RevokedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("TokenHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("character varying(64)");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("uuid");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("TokenHash")
+                        .IsUnique();
+
+                    b.HasIndex("UserId", "FamilyId");
+
+                    b.ToTable("RefreshTokens");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("AssignedTo")
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("Detail")
+                        .HasMaxLength(2000)
+                        .HasColumnType("character varying(2000)");
+
+                    b.Property<DateTimeOffset?>("DueDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid?>("ParentTaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Priority")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<Guid?>("ProjectId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Source")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<string>("State")
+                        .IsRequired()
+                        .HasColumnType("text");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(240)
+                        .HasColumnType("character varying(240)");
+
+                    b.Property<DateTimeOffset>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AssignedTo");
+
+                    b.HasIndex("ParentTaskId");
+
+                    b.HasIndex("Source");
+
+                    b.ToTable("Tasks");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.RefreshToken", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.NexusUser", "User")
+                        .WithMany("RefreshTokens")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.WorkTask", "ParentTask")
+                        .WithMany("ChildTasks")
+                        .HasForeignKey("ParentTaskId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.Navigation("ParentTask");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
+                {
+                    b.Navigation("RefreshTokens");
+                });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Navigation("ChildTasks");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}
diff --git a/backend/Data/Migrations/20260618233003_AddDelegatedState.cs b/backend/Data/Migrations/20260618233003_AddDelegatedState.cs
new file mode 100644
index 0000000..1606356
--- /dev/null
+++ b/backend/Data/Migrations/20260618233003_AddDelegatedState.cs
@@ -0,0 +1,24 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Nexus.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddDelegatedState : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            // Delegated state is a pure code change to the TaskState enum and
+            // TaskStateHelper. No schema change required since the State column
+            // is already a free-form string column.
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            // No schema to revert.
+        }
+    }
+}
diff --git a/backend/Data/Migrations/NexusDbContextModelSnapshot.cs b/backend/Data/Migrations/NexusDbContextModelSnapshot.cs
index bbff781..c8379c8 100644
--- a/backend/Data/Migrations/NexusDbContextModelSnapshot.cs
+++ b/backend/Data/Migrations/NexusDbContextModelSnapshot.cs
@@ -38,12 +38,19 @@ namespace Nexus.Api.Migrations
                         .HasMaxLength(1000)
                         .HasColumnType("character varying(1000)");
 
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
                     b.Property<string>("Type")
                         .IsRequired()
                         .HasColumnType("text");
 
                     b.HasKey("Id");
 
+                    b.HasIndex("CreatedAt");
+
+                    b.HasIndex("TaskId");
+
                     b.ToTable("Activity");
                 });
 
@@ -93,6 +100,47 @@ namespace Nexus.Api.Migrations
                     b.ToTable("Users");
                 });
 
+            modelBuilder.Entity("Nexus.Api.Data.Notification", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("uuid");
+
+                    b.Property<DateTimeOffset>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<string>("ForUser")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.Property<bool>("IsRead")
+                        .HasColumnType("boolean");
+
+                    b.Property<string>("Message")
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<Guid?>("TaskId")
+                        .HasColumnType("uuid");
+
+                    b.Property<string>("Title")
+                        .IsRequired()
+                        .HasMaxLength(240)
+                        .HasColumnType("character varying(240)");
+
+                    b.Property<string>("Type")
+                        .IsRequired()
+                        .HasMaxLength(60)
+                        .HasColumnType("character varying(60)");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ForUser", "IsRead", "CreatedAt");
+
+                    b.ToTable("Notifications");
+                });
+
             modelBuilder.Entity("Nexus.Api.Data.Project", b =>
                 {
                     b.Property<Guid>("Id")
@@ -183,6 +231,12 @@ namespace Nexus.Api.Migrations
                         .HasMaxLength(2000)
                         .HasColumnType("character varying(2000)");
 
+                    b.Property<DateTimeOffset?>("DueDate")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<Guid?>("ParentTaskId")
+                        .HasColumnType("uuid");
+
                     b.Property<string>("Priority")
                         .IsRequired()
                         .HasColumnType("text");
@@ -211,6 +265,8 @@ namespace Nexus.Api.Migrations
 
                     b.HasIndex("AssignedTo");
 
+                    b.HasIndex("ParentTaskId");
+
                     b.HasIndex("Source");
 
                     b.ToTable("Tasks");
@@ -227,10 +283,25 @@ namespace Nexus.Api.Migrations
                     b.Navigation("User");
                 });
 
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.HasOne("Nexus.Api.Data.WorkTask", "ParentTask")
+                        .WithMany("ChildTasks")
+                        .HasForeignKey("ParentTaskId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.Navigation("ParentTask");
+                });
+
             modelBuilder.Entity("Nexus.Api.Data.NexusUser", b =>
                 {
                     b.Navigation("RefreshTokens");
                 });
+
+            modelBuilder.Entity("Nexus.Api.Data.WorkTask", b =>
+                {
+                    b.Navigation("ChildTasks");
+                });
 #pragma warning restore 612, 618
         }
     }
diff --git a/backend/Data/NexusDbContext.cs b/backend/Data/NexusDbContext.cs
index e4e7a32..6f6aab0 100644
--- a/backend/Data/NexusDbContext.cs
+++ b/backend/Data/NexusDbContext.cs
@@ -6,6 +6,7 @@ public sealed class NexusDbContext(DbContextOptions<NexusDbContext> options) : D
 {
     public DbSet<Project> Projects => Set<Project>();
     public DbSet<WorkTask> Tasks => Set<WorkTask>();
+    public DbSet<Notification> Notifications => Set<Notification>();
     public DbSet<ActivityEvent> Activity => Set<ActivityEvent>();
     public DbSet<NexusUser> Users => Set<NexusUser>();
     public DbSet<RefreshToken> RefreshTokens => Set<RefreshToken>();
@@ -21,8 +22,25 @@ public sealed class NexusDbContext(DbContextOptions<NexusDbContext> options) : D
             entity.Property(x => x.AssignedTo).HasMaxLength(60);
             entity.HasIndex(x => x.Source);
             entity.HasIndex(x => x.AssignedTo);
+            entity.HasOne(x => x.ParentTask)
+                  .WithMany(x => x.ChildTasks)
+                  .HasForeignKey(x => x.ParentTaskId)
+                  .OnDelete(DeleteBehavior.SetNull);
+        });
+        modelBuilder.Entity<Notification>(entity =>
+        {
+            entity.Property(x => x.Title).HasMaxLength(240);
+            entity.Property(x => x.Message).HasMaxLength(1000);
+            entity.Property(x => x.Type).HasMaxLength(60);
+            entity.Property(x => x.ForUser).HasMaxLength(60);
+            entity.HasIndex(x => new { x.ForUser, x.IsRead, x.CreatedAt });
+        });
+
+        modelBuilder.Entity<ActivityEvent>(entity =>
+        {
+            entity.Property(x => x.Message).HasMaxLength(1000);
+            entity.HasIndex(x => x.TaskId);
         });
-        modelBuilder.Entity<ActivityEvent>().Property(x => x.Message).HasMaxLength(1000);
         modelBuilder.Entity<NexusUser>().HasIndex(u => u.NormalizedEmail).IsUnique();
         modelBuilder.Entity<RefreshToken>().HasIndex(r => r.TokenHash).IsUnique();
         modelBuilder.Entity<RefreshToken>().HasIndex(r => new { r.UserId, r.FamilyId });
diff --git a/backend/Extensions/ApplicationBuilderExtensions.cs b/backend/Extensions/ApplicationBuilderExtensions.cs
index 5139dee..7e370a4 100644
--- a/backend/Extensions/ApplicationBuilderExtensions.cs
+++ b/backend/Extensions/ApplicationBuilderExtensions.cs
@@ -68,6 +68,7 @@ public static class ApplicationBuilderExtensions
     {
         app.UseForwardedHeaders();
         app.UseRateLimiter();
+        app.UseApiKeyAuthentication();
         app.UseAuthentication();
         app.UseAuthorization();
         app.UseSecurityHeaders();
diff --git a/backend/Extensions/ServiceCollectionExtensions.cs b/backend/Extensions/ServiceCollectionExtensions.cs
index 4b7d0d9..ecdde80 100644
--- a/backend/Extensions/ServiceCollectionExtensions.cs
+++ b/backend/Extensions/ServiceCollectionExtensions.cs
@@ -170,6 +170,7 @@ public static class ServiceCollectionExtensions
     /// </summary>
     public static IServiceCollection AddNexusApplicationServices(this IServiceCollection services)
     {
+        services.AddHttpContextAccessor();
         services.AddTransient<ModelRoutingService>();
         services.AddScoped<IAuthService, AuthService>();
         services.AddScoped<IAgentService, AgentService>();
@@ -182,6 +183,7 @@ public static class ServiceCollectionExtensions
         services.AddSingleton<IMemoryService, MemoryService>();
         services.AddSingleton<IIncidentService, IncidentService>();
         services.AddSingleton<IDocService, DocService>();
+        services.AddScoped<INotificationService, NotificationService>();
         services.AddScoped<ICalendarService, CalendarService>();
 
         return services;
diff --git a/backend/Middleware/ApiKeyMiddleware.cs b/backend/Middleware/ApiKeyMiddleware.cs
new file mode 100644
index 0000000..5ab1c6f
--- /dev/null
+++ b/backend/Middleware/ApiKeyMiddleware.cs
@@ -0,0 +1,39 @@
+using System.Security.Claims;
+
+namespace Nexus.Api.Middleware;
+
+/// <summary>
+/// Middleware that authenticates requests via the X-Nexus-Api-Key header.
+/// On match, sets a ClaimsPrincipal with role "Service".
+/// On mismatch or absent header, passes through to next middleware (JWT auth).
+/// </summary>
+public sealed class ApiKeyMiddleware(RequestDelegate next)
+{
+    public async Task InvokeAsync(HttpContext context)
+    {
+        var configuration = context.RequestServices.GetRequiredService<IConfiguration>();
+        var apiKey = configuration["NexusApiKey"];
+
+        if (!string.IsNullOrWhiteSpace(apiKey) &&
+            context.Request.Headers.TryGetValue("X-Nexus-Api-Key", out var providedKey) &&
+            string.Equals(apiKey, providedKey, StringComparison.Ordinal))
+        {
+            var claims = new[]
+            {
+                new Claim(ClaimTypes.NameIdentifier, "service"),
+                new Claim(ClaimTypes.Name, "ApiService"),
+                new Claim(ClaimTypes.Role, "Service")
+            };
+            var identity = new ClaimsIdentity(claims, "ApiKey");
+            context.User = new ClaimsPrincipal(identity);
+        }
+
+        await next(context);
+    }
+}
+
+public static class ApiKeyMiddlewareExtensions
+{
+    public static IApplicationBuilder UseApiKeyAuthentication(this IApplicationBuilder builder)
+        => builder.UseMiddleware<ApiKeyMiddleware>();
+}
diff --git a/backend/Models/Dashboard.cs b/backend/Models/Dashboard.cs
index 7025071..03654ae 100644
--- a/backend/Models/Dashboard.cs
+++ b/backend/Models/Dashboard.cs
@@ -86,6 +86,8 @@ public sealed record DashboardTaskDto(
     string State,
     string Priority,
     string? AssignedTo,
+    Guid? ParentTaskId,
+    DateTimeOffset? DueDate,
     DateTimeOffset CreatedAt,
     DateTimeOffset UpdatedAt
 );
@@ -95,7 +97,8 @@ public sealed record CreateDashboardTaskRequest(
     string? Detail,
     string? Source,
     string? Priority,
-    string? AssignedTo
+    string? AssignedTo,
+    Guid? ParentTaskId = null
 );
 
 public sealed record UpdateDashboardTaskRequest(
@@ -103,7 +106,8 @@ public sealed record UpdateDashboardTaskRequest(
     string? Detail,
     string? Source,
     string? Priority,
-    string? AssignedTo
+    string? AssignedTo,
+    DateTimeOffset? DueDate = null
 );
 
 public sealed record UpdateDashboardTaskStatusRequest(
@@ -120,6 +124,7 @@ public sealed record AgentActivityEntry(
 public sealed record TaskBoardResponse(
     List<DashboardTaskDto> Offen,
     List<DashboardTaskDto> InProgress,
+    List<DashboardTaskDto> Delegated,
     List<DashboardTaskDto> Review,
     List<DashboardTaskDto> Blocked,
     List<DashboardTaskDto> Done
@@ -132,3 +137,20 @@ public sealed record MoveTaskRequest(
 public sealed record ImportResultDto(
     int Imported
 );
+
+public sealed record ResetStaleRequest(
+    int StaleHours = 2
+);
+
+public sealed record ResetStaleResponse(
+    int ResetCount
+);
+
+// ── Notification DTOs ──
+
+public sealed record NotificationDto(
+    Guid Id, string Type, string Title, string? Message,
+    string ForUser, Guid? TaskId, bool IsRead, DateTimeOffset CreatedAt
+);
+
+public sealed record UnreadCountDto(int Count);
diff --git a/backend/NexusDbContextFactory.cs b/backend/NexusDbContextFactory.cs
new file mode 100644
index 0000000..21cb1b5
--- /dev/null
+++ b/backend/NexusDbContextFactory.cs
@@ -0,0 +1,20 @@
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Design;
+using Nexus.Api.Data;
+
+namespace Nexus.Api;
+
+public class NexusDbContextFactory : IDesignTimeDbContextFactory<NexusDbContext>
+{
+    public NexusDbContext CreateDbContext(string[] args)
+    {
+        var optionsBuilder = new DbContextOptionsBuilder<NexusDbContext>();
+        var connectionString = args.Length > 0
+            ? args[0]
+            : Environment.GetEnvironmentVariable("ConnectionStrings__Nexus")
+              ?? "Host=localhost;Port=5432;Database=nexus;Username=nexus;Password=nexus";
+
+        optionsBuilder.UseNpgsql(connectionString);
+        return new NexusDbContext(optionsBuilder.Options);
+    }
+}
diff --git a/backend/Repositories/TaskRepository.cs b/backend/Repositories/TaskRepository.cs
index c086d5c..9641530 100644
--- a/backend/Repositories/TaskRepository.cs
+++ b/backend/Repositories/TaskRepository.cs
@@ -30,6 +30,7 @@ public sealed class TaskRepository(NexusDbContext db) : ITaskRepository
     public async Task UpdateAsync(WorkTask task, CancellationToken ct = default)
     {
         task.UpdatedAt = DateTimeOffset.UtcNow;
+        db.Tasks.Update(task);
         await db.SaveChangesAsync(ct);
     }
 
diff --git a/backend/Services/INotificationService.cs b/backend/Services/INotificationService.cs
new file mode 100644
index 0000000..71157a1
--- /dev/null
+++ b/backend/Services/INotificationService.cs
@@ -0,0 +1,13 @@
+using Nexus.Api.Data;
+using Nexus.Api.Models;
+
+namespace Nexus.Api.Services;
+
+public interface INotificationService
+{
+    Task<Notification> CreateAsync(string type, string title, string? message, string forUser, Guid? taskId = null, CancellationToken ct = default);
+    Task<IReadOnlyList<Notification>> GetForUserAsync(string forUser, int limit = 50, bool unreadOnly = false, CancellationToken ct = default);
+    Task<bool> MarkAsReadAsync(Guid id, CancellationToken ct = default);
+    Task<int> MarkAllAsReadAsync(string forUser, CancellationToken ct = default);
+    Task<int> GetUnreadCountAsync(string forUser, CancellationToken ct = default);
+}
diff --git a/backend/Services/ITaskService.cs b/backend/Services/ITaskService.cs
index 7768f66..c6c46fd 100644
--- a/backend/Services/ITaskService.cs
+++ b/backend/Services/ITaskService.cs
@@ -22,8 +22,8 @@ public interface ITaskService
 
     // Dashboard-facing task operations
     Task<IReadOnlyList<WorkTask>> GetOpenAsync(CancellationToken ct = default);
-    Task<WorkTask> CreateDashboardTaskAsync(string title, string? detail, string? source, string? priority, string? assignedTo, CancellationToken ct = default);
-    Task<TaskOperationResult> UpdateDashboardTaskAsync(Guid id, string? title, string? detail, string? source, string? priority, string? assignedTo, CancellationToken ct = default);
+    Task<WorkTask> CreateDashboardTaskAsync(string title, string? detail, string? source, string? priority, string? assignedTo, Guid? parentTaskId = null, CancellationToken ct = default);
+    Task<TaskOperationResult> UpdateDashboardTaskAsync(Guid id, string? title, string? detail, string? source, string? priority, string? assignedTo, DateTimeOffset? dueDate = null, CancellationToken ct = default);
     Task<TaskOperationResult> UpdateStatusAsync(Guid id, string status, CancellationToken ct = default);
     Task<TaskOperationResult> CompleteViaQueueAsync(Guid id, CancellationToken ct = default);
     Task<TaskOperationResult> CyclePriorityAsync(Guid id, CancellationToken ct = default);
@@ -31,5 +31,8 @@ public interface ITaskService
     // Task Board
     Task<TaskBoardResponse> GetBoardAsync(CancellationToken ct = default);
     Task<TaskOperationResult> MoveTaskAsync(Guid id, string newState, CancellationToken ct = default);
+    Task<int> ResetStaleInProgressTasksAsync(TimeSpan staleThreshold, CancellationToken ct = default);
+    Task<IReadOnlyList<WorkTask>> GetChildTasksAsync(Guid parentId, CancellationToken ct = default);
+    Task<List<ActivityEvent>> GetTaskActivityAsync(Guid taskId, CancellationToken ct = default);
     Task<int> ImportFromIrisTodoAsync(bool deleteAfterImport = false, CancellationToken ct = default);
 }
diff --git a/backend/Services/NotificationService.cs b/backend/Services/NotificationService.cs
new file mode 100644
index 0000000..14652bf
--- /dev/null
+++ b/backend/Services/NotificationService.cs
@@ -0,0 +1,61 @@
+using Microsoft.EntityFrameworkCore;
+using Nexus.Api.Data;
+using Nexus.Api.Models;
+
+namespace Nexus.Api.Services;
+
+public sealed class NotificationService(NexusDbContext db) : INotificationService
+{
+    public async Task<Notification> CreateAsync(string type, string title, string? message, string forUser, Guid? taskId = null, CancellationToken ct = default)
+    {
+        var notification = new Notification
+        {
+            Type = type,
+            Title = title,
+            Message = message,
+            ForUser = forUser.ToLowerInvariant(),
+            TaskId = taskId
+        };
+        db.Notifications.Add(notification);
+        await db.SaveChangesAsync(ct);
+        return notification;
+    }
+
+    public async Task<IReadOnlyList<Notification>> GetForUserAsync(string forUser, int limit = 50, bool unreadOnly = false, CancellationToken ct = default)
+    {
+        var query = db.Notifications
+            .Where(n => n.ForUser == forUser.ToLowerInvariant());
+
+        if (unreadOnly)
+            query = query.Where(n => !n.IsRead);
+
+        return await query
+            .OrderByDescending(n => n.CreatedAt)
+            .Take(limit)
+            .ToListAsync(ct);
+    }
+
+    public async Task<bool> MarkAsReadAsync(Guid id, CancellationToken ct = default)
+    {
+        var notification = await db.Notifications.FindAsync([id], ct);
+        if (notification is null) return false;
+
+        notification.IsRead = true;
+        await db.SaveChangesAsync(ct);
+        return true;
+    }
+
+    public async Task<int> MarkAllAsReadAsync(string forUser, CancellationToken ct = default)
+    {
+        var count = await db.Notifications
+            .Where(n => n.ForUser == forUser.ToLowerInvariant() && !n.IsRead)
+            .ExecuteUpdateAsync(s => s.SetProperty(n => n.IsRead, true), ct);
+        return count;
+    }
+
+    public async Task<int> GetUnreadCountAsync(string forUser, CancellationToken ct = default)
+    {
+        return await db.Notifications
+            .CountAsync(n => n.ForUser == forUser.ToLowerInvariant() && !n.IsRead, ct);
+    }
+}
diff --git a/backend/Services/TaskService.cs b/backend/Services/TaskService.cs
index 2056caf..376a9cd 100644
--- a/backend/Services/TaskService.cs
+++ b/backend/Services/TaskService.cs
@@ -8,8 +8,12 @@ namespace Nexus.Api.Services;
 
 public sealed class TaskService(
     ITaskRepository taskRepo,
-    IActivityRepository activityRepo) : ITaskService
+    IActivityRepository activityRepo,
+    INotificationService notificationService) : ITaskService
 {
+    private static readonly HashSet<string> ValidAssignees =
+        ["bao", "iris", "programmer", "reviewer", "architekt"];
+
     public async Task<IReadOnlyList<WorkTask>> GetAllAsync(CancellationToken ct = default)
         => await taskRepo.GetAllAsync(ct);
 
@@ -28,7 +32,7 @@ public sealed class TaskService(
             ProjectId = request.ProjectId
         };
         await taskRepo.AddAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} created" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} created", TaskId = task.Id }, ct);
         return task;
     }
 
@@ -42,7 +46,7 @@ public sealed class TaskService(
 
         task.State = TaskStateHelper.ToStateString(TaskState.Done);
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} approved" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} approved", TaskId = task.Id }, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
@@ -56,7 +60,7 @@ public sealed class TaskService(
 
         task.State = TaskStateHelper.ToStateString(TaskState.Backlog);
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} rejected, returned to backlog" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} rejected, returned to backlog", TaskId = task.Id }, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
@@ -70,7 +74,8 @@ public sealed class TaskService(
 
         task.State = canonical;
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} moved to {task.State}" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} moved to {task.State}", TaskId = task.Id }, ct);
+        await CreateStatusChangeNotificationsAsync(task, canonical, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
@@ -87,7 +92,7 @@ public sealed class TaskService(
             task.ProjectId = request.ProjectId.Value == Guid.Empty ? null : request.ProjectId;
 
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} updated" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} updated", TaskId = task.Id }, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
@@ -99,7 +104,7 @@ public sealed class TaskService(
         if (!TaskStateHelper.IsDoneOrBacklog(task.State))
             return new TaskOperationResult(TaskOperationOutcome.InvalidState, task);
 
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} deleted" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task {task.Title} deleted", TaskId = task.Id }, ct);
         await taskRepo.DeleteAsync(task, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success);
     }
@@ -115,23 +120,51 @@ public sealed class TaskService(
     }
 
     public async Task<WorkTask> CreateDashboardTaskAsync(
-        string title, string? detail, string? source, string? priority, string? assignedTo, CancellationToken ct = default)
+        string title, string? detail, string? source, string? priority,
+        string? assignedTo, Guid? parentTaskId = null, CancellationToken ct = default)
     {
+        // Validate parent task exists if specified
+        if (parentTaskId.HasValue)
+        {
+            var parent = await taskRepo.GetByIdAsync(parentTaskId.Value, ct);
+            if (parent is null)
+                throw new ArgumentException($"Parent task {parentTaskId} not found.", nameof(parentTaskId));
+        }
+
         var task = new WorkTask
         {
             Title = title.Trim(),
             Detail = detail?.Trim(),
             Source = string.IsNullOrWhiteSpace(source) ? "bao" : source.Trim(),
             Priority = string.IsNullOrWhiteSpace(priority) ? "Normal" : priority.Trim(),
-            AssignedTo = ValidateAssignedTo(assignedTo)
+            AssignedTo = ValidateAssignedTo(assignedTo),
+            ParentTaskId = parentTaskId
         };
         await taskRepo.AddAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" created ({task.Source})" }, ct);
+
+        var message = $"Task \"{task.Title}\" created ({task.Source})";
+        if (parentTaskId.HasValue)
+            message += $" [child of {parentTaskId.Value}]";
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = message, TaskId = task.Id }, ct);
+
+        // Auto-notify: if assigned to bao, create a task_assigned notification
+        if (string.Equals(assignedTo, "bao", StringComparison.OrdinalIgnoreCase))
+        {
+            await notificationService.CreateAsync(
+                "task_assigned",
+                $"Neue Aufgabe: {task.Title}",
+                detail,
+                "bao",
+                task.Id,
+                ct);
+        }
+
         return task;
     }
 
     public async Task<TaskOperationResult> UpdateDashboardTaskAsync(
-        Guid id, string? title, string? detail, string? source, string? priority, string? assignedTo, CancellationToken ct = default)
+        Guid id, string? title, string? detail, string? source,
+        string? priority, string? assignedTo, DateTimeOffset? dueDate = null, CancellationToken ct = default)
     {
         var task = await taskRepo.GetByIdAsync(id, ct);
         if (task is null) return new TaskOperationResult(TaskOperationOutcome.NotFound);
@@ -141,9 +174,10 @@ public sealed class TaskService(
         if (!string.IsNullOrWhiteSpace(source)) task.Source = source.Trim();
         if (!string.IsNullOrWhiteSpace(priority)) task.Priority = priority.Trim();
         if (assignedTo is not null) task.AssignedTo = ValidateAssignedTo(assignedTo);
+        if (dueDate.HasValue) task.DueDate = dueDate;
 
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" updated" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" updated", TaskId = task.Id }, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
@@ -158,7 +192,8 @@ public sealed class TaskService(
         var canonical = TaskStateHelper.AllStates.First(s => s.Equals(status, StringComparison.OrdinalIgnoreCase));
         task.State = canonical;
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" → {canonical}" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" → {canonical}", TaskId = task.Id }, ct);
+        await CreateStatusChangeNotificationsAsync(task, canonical, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
@@ -169,7 +204,7 @@ public sealed class TaskService(
 
         task.State = "Done";
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" completed via queue" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" completed via queue", TaskId = task.Id }, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
@@ -187,7 +222,7 @@ public sealed class TaskService(
         };
 
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" priority → {task.Priority}" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" priority → {task.Priority}", TaskId = task.Id }, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
@@ -198,6 +233,7 @@ public sealed class TaskService(
         var all = await taskRepo.GetAllAsync(ct);
         var offen = new List<DashboardTaskDto>();
         var inProgress = new List<DashboardTaskDto>();
+        var delegated = new List<DashboardTaskDto>();
         var review = new List<DashboardTaskDto>();
         var blocked = new List<DashboardTaskDto>();
         var done = new List<DashboardTaskDto>();
@@ -211,6 +247,8 @@ public sealed class TaskService(
                     offen.Add(dto); break;
                 case "in progress":
                     inProgress.Add(dto); break;
+                case "delegated":
+                    delegated.Add(dto); break;
                 case "review":
                     review.Add(dto); break;
                 case "blocked":
@@ -222,9 +260,32 @@ public sealed class TaskService(
             }
         }
 
-        return new TaskBoardResponse(offen, inProgress, review, blocked, done);
+        // Priority sort within each group: High > Medium > Low, then by CreatedAt ascending
+        offen.Sort(SortByPriorityThenCreatedAt);
+        inProgress.Sort(SortByPriorityThenCreatedAt);
+        delegated.Sort(SortByPriorityThenCreatedAt);
+        review.Sort(SortByPriorityThenCreatedAt);
+        blocked.Sort(SortByPriorityThenCreatedAt);
+        done.Sort(SortByPriorityThenCreatedAt);
+
+        return new TaskBoardResponse(offen, inProgress, delegated, review, blocked, done);
     }
 
+    private static int SortByPriorityThenCreatedAt(DashboardTaskDto a, DashboardTaskDto b)
+    {
+        var priorityCompare = PriorityScore(b.Priority).CompareTo(PriorityScore(a.Priority));
+        return priorityCompare != 0 ? priorityCompare : a.CreatedAt.CompareTo(b.CreatedAt);
+    }
+
+    private static int PriorityScore(string priority) => priority.ToLowerInvariant() switch
+    {
+        "high" => 3,
+        "medium" => 2,
+        "normal" => 2,
+        "low" => 1,
+        _ => 2
+    };
+
     public async Task<TaskOperationResult> MoveTaskAsync(Guid id, string newState, CancellationToken ct = default)
     {
         // Resolve canonical state: accept board group keys or canonical strings
@@ -245,10 +306,50 @@ public sealed class TaskService(
 
         task.State = canonical;
         await taskRepo.UpdateAsync(task, ct);
-        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" moved to {canonical}" }, ct);
+        await activityRepo.AddAsync(new ActivityEvent { Type = "task", Message = $"Task \"{task.Title}\" moved to {canonical}", TaskId = task.Id }, ct);
+        await CreateStatusChangeNotificationsAsync(task, canonical, ct);
         return new TaskOperationResult(TaskOperationOutcome.Success, task);
     }
 
+    public async Task<int> ResetStaleInProgressTasksAsync(TimeSpan staleThreshold, CancellationToken ct = default)
+    {
+        var all = await taskRepo.GetAllAsync(ct);
+        var threshold = DateTimeOffset.UtcNow - staleThreshold;
+        var staleTasks = all.Where(t =>
+            (string.Equals(t.State, "In progress", StringComparison.OrdinalIgnoreCase) ||
+             string.Equals(t.State, "Delegated", StringComparison.OrdinalIgnoreCase)) &&
+            t.UpdatedAt < threshold).ToList();
+
+        foreach (var task in staleTasks)
+        {
+            var prevState = task.State;
+            task.State = "Backlog";
+            await taskRepo.UpdateAsync(task, ct);
+            await activityRepo.AddAsync(new ActivityEvent
+            {
+                Type = "task",
+                Message = $"Task \"{task.Title}\" reset from {prevState} to Backlog (stale)",
+                TaskId = task.Id
+            }, ct);
+        }
+
+        return staleTasks.Count;
+    }
+
+    public async Task<IReadOnlyList<WorkTask>> GetChildTasksAsync(Guid parentId, CancellationToken ct = default)
+    {
+        var all = await taskRepo.GetAllAsync(ct);
+        return all.Where(t => t.ParentTaskId == parentId)
+                  .OrderByDescending(t => t.CreatedAt)
+                  .ToList();
+    }
+
+    public async Task<List<ActivityEvent>> GetTaskActivityAsync(Guid taskId, CancellationToken ct = default)
+    {
+        var all = await activityRepo.GetRecentAsync(100, ct);
+        return all.Where(e => e.TaskId == taskId).ToList();
+    }
+
     public async Task<int> ImportFromIrisTodoAsync(bool deleteAfterImport = false, CancellationToken ct = default)
     {
         var todoPath = "/mnt/workspace-iris/TODO.md";
@@ -318,17 +419,44 @@ public sealed class TaskService(
     }
 
     private static DashboardTaskDto MapToDto(WorkTask t) => new(
-        t.Id, t.Title, t.Detail, t.Source, t.State, t.Priority, t.AssignedTo, t.CreatedAt, t.UpdatedAt);
+        t.Id, t.Title, t.Detail, t.Source, t.State, t.Priority, t.AssignedTo,
+        t.ParentTaskId, t.DueDate, t.CreatedAt, t.UpdatedAt);
 
     /// <summary>
-    /// Validates AssignedTo — only "bao", "iris", or null are accepted.
+    /// Validates AssignedTo — only recognized agent values are accepted.
     /// Returns null for invalid values.
     /// </summary>
     private static string? ValidateAssignedTo(string? assignedTo)
     {
         if (string.IsNullOrWhiteSpace(assignedTo)) return null;
         var lower = assignedTo.Trim().ToLowerInvariant();
-        if (lower is "bao" or "iris") return lower;
-        return null;
+        return ValidAssignees.Contains(lower) ? lower : null;
     }
-} 
+
+    /// <summary>
+    /// Creates status-change notifications when a task moves to Review or Blocked.
+    /// </summary>
+    private async Task CreateStatusChangeNotificationsAsync(WorkTask task, string canonical, CancellationToken ct)
+    {
+        if (string.Equals(canonical, "Review", StringComparison.OrdinalIgnoreCase))
+        {
+            await notificationService.CreateAsync(
+                "task_review",
+                $"Task zur Überprüfung: {task.Title}",
+                $"Status auf Review geändert von {task.AssignedTo ?? "unbekannt"}",
+                "bao",
+                task.Id,
+                ct);
+        }
+        else if (string.Equals(canonical, "Blocked", StringComparison.OrdinalIgnoreCase))
+        {
+            await notificationService.CreateAsync(
+                "task_blocked",
+                $"Aufgabe blockiert: {task.Title}",
+                "Die Task konnte nicht abgeschlossen werden und wurde blockiert.",
+                "iris",
+                task.Id,
+                ct);
+        }
+    }
+}
diff --git a/backend/core.3048 b/backend/core.3048
new file mode 100644
index 0000000..ddb4405
Binary files /dev/null and b/backend/core.3048 differ
diff --git a/compose.yaml b/compose.yaml
index 8410b70..7cb5f1a 100644
--- a/compose.yaml
+++ b/compose.yaml
@@ -58,6 +58,7 @@ services:
       Integrations__OpenClaw__Token: ${OPENCLAW_GATEWAY_TOKEN:-}
       Integrations__OpenClaw__Password: ${OPENCLAW_GATEWAY_PASSWORD:-}
       Admin__ResetToken: ${Admin__ResetToken:-}
+      NexusApiKey: ${NEXUS_API_KEY:-}
     extra_hosts:
       - host.docker.internal:host-gateway
     depends_on:
diff --git a/frontend/src/App.vue b/frontend/src/App.vue
index ab651f5..68e14e6 100644
--- a/frontend/src/App.vue
+++ b/frontend/src/App.vue
@@ -23,7 +23,7 @@ const activeView = computed(() => {
 const routePaths: Record<string, string> = {
   Dashboard: '/dashboard', Memory: '/memory', Docs: '/docs', Security: '/security',
   Projects: '/projects', 'Task Board': '/tasks', Incidents: '/incidents', Calendar: '/calendar',
-  Agents: '/agents', Models: '/models', Activity: '/activity', 'Mobile Chat': '/chat', Settings: '/settings',
+  Agents: '/agents', Models: '/models', Activity: '/activity', 'Mobile Chat': '/chat', Notifications: '/notifications', Settings: '/settings',
 }
 
 const navigate = (label: string) => {
@@ -32,7 +32,7 @@ const navigate = (label: string) => {
 }
 const mobileNavOpen = ref(false)
 
-const standaloneViews = computed(() => ['Dashboard', 'Settings', 'ProjectDetail', 'Memory', 'Docs', 'Security', 'Incidents', 'Calendar', 'AgentDetail', 'Agents', 'Task Board'].includes(activeView.value))
+const standaloneViews = computed(() => ['Dashboard', 'Settings', 'ProjectDetail', 'Memory', 'Docs', 'Security', 'Incidents', 'Calendar', 'AgentDetail', 'Agents', 'Task Board', 'Notifications'].includes(activeView.value))
 
 onMounted(() => {
   if (auth.isAuthenticated) store.refresh()
diff --git a/frontend/src/components/layout/AppSidebar.vue b/frontend/src/components/layout/AppSidebar.vue
index 09fee6d..60e97ab 100644
--- a/frontend/src/components/layout/AppSidebar.vue
+++ b/frontend/src/components/layout/AppSidebar.vue
@@ -1,13 +1,14 @@
 <script setup lang="ts">
-import { computed } from 'vue'
+import { computed, onMounted } from 'vue'
 import {
-  Activity, Bot, Boxes, Command, FileText,
+  Activity, Bell, Bot, Boxes, Command, FileText,
   LayoutDashboard, ListTodo, LogOut, MessageSquareText, Settings,
   Shield, SlidersHorizontal, Sparkles, BookOpen,
   AlertTriangle, Calendar,
 } from '@lucide/vue'
 import { useRouter } from 'vue-router'
 import { useAuthStore } from '../../stores/auth'
+import { useNotificationStore } from '../../stores/notifications'
 import { initials } from '../../utils/format'
 
 const props = defineProps<{
@@ -23,6 +24,11 @@ const emit = defineEmits<{
 
 const auth = useAuthStore()
 const router = useRouter()
+const notificationStore = useNotificationStore()
+
+onMounted(() => {
+  notificationStore.startPolling()
+})
 
 const ownerInitials = computed(() =>
   auth.user?.displayName ? initials(auth.user.displayName) : 'OW'
@@ -37,6 +43,7 @@ const navigation = [
   { label: 'Task Board', icon: ListTodo },
   { label: 'Incidents', icon: AlertTriangle },
   { separator: true },
+  { label: 'Notifications', icon: Bell },
   { label: 'Calendar', icon: Calendar },
   { label: 'Agents', icon: Bot },
   { label: 'Models', icon: SlidersHorizontal },
@@ -76,6 +83,7 @@ async function logout() {
           <span>{{ item.label }}</span>
           <i v-if="item.label === 'Task Board'">{{ queuedTasks }}</i>
           <i v-if="item.label === 'Incidents'">{{ incidents }}</i>
+          <i v-if="item.label === 'Notifications' && notificationStore.unreadCount > 0" class="badge-red">{{ notificationStore.unreadCount }}</i>
         </button>
       </template>
     </nav>
@@ -154,6 +162,9 @@ async function logout() {
   border-radius: 5px;
   line-height: 1.4;
 }
+.nav button i.badge-red {
+  background: #e16e75;
+}
 .nav-separator {
   height: 1px;
   margin: 6px 10px;
diff --git a/frontend/src/router.ts b/frontend/src/router.ts
index 16fdecc..ef628e1 100644
--- a/frontend/src/router.ts
+++ b/frontend/src/router.ts
@@ -12,6 +12,7 @@ import CalendarView from './views/CalendarView.vue'
 import NexusLayout from './layouts/NexusLayout.vue'
 import FlowBoard from './views/Dashboard/FlowBoard.vue'
 import TaskBoardView from './views/TaskBoardView.vue'
+import NotificationsView from './views/NotificationsView.vue'
 
 const routes = [
   { path: '/login', name: 'Login', component: LoginView, meta: { public: true } },
@@ -39,6 +40,7 @@ const routes = [
   { path: '/models', name: 'Models', component: { template: '' } },
   { path: '/activity', name: 'Activity', component: { template: '' } },
   { path: '/chat', name: 'Mobile Chat', component: { template: '' } },
+  { path: '/notifications', name: 'Notifications', component: NotificationsView },
   { path: '/settings', name: 'Settings', component: SettingsView },
   { path: '/:pathMatch(.*)*', redirect: '/dashboard' },
 ]
diff --git a/frontend/src/stores/notifications.ts b/frontend/src/stores/notifications.ts
new file mode 100644
index 0000000..dc1e81c
--- /dev/null
+++ b/frontend/src/stores/notifications.ts
@@ -0,0 +1,123 @@
+/**
+ * Notification Store – Polls unread count and notifications from the API.
+ */
+import { defineStore } from 'pinia'
+import { apiFetch } from '../services/api'
+
+export interface NotificationItem {
+  id: string
+  type: string       // "task_assigned", "task_review", "task_blocked"
+  title: string
+  message: string | null
+  forUser: string
+  taskId: string | null
+  isRead: boolean
+  createdAt: string
+}
+
+export interface UnreadCount {
+  count: number
+}
+
+export const useNotificationStore = defineStore('notifications', {
+  state: () => ({
+    notifications: [] as NotificationItem[],
+    unreadCount: 0,
+    loading: false,
+    error: null as string | null,
+    countRefreshInterval: null as ReturnType<typeof setInterval> | null,
+    listRefreshInterval: null as ReturnType<typeof setInterval> | null,
+  }),
+
+  actions: {
+    async fetchNotifications(forUser = 'bao', limit = 50, unreadOnly = false) {
+      this.loading = true
+      try {
+        const params = new URLSearchParams({ forUser, limit: String(limit), unreadOnly: String(unreadOnly) })
+        const res = await apiFetch(`/api/dashboard/notifications?${params}`)
+        if (!res.ok) throw new Error(`HTTP ${res.status}`)
+        this.notifications = await res.json()
+        this.error = null
+      } catch (err) {
+        console.warn('[NotificationStore] fetchNotifications failed', err)
+        this.error = 'Notifications could not be loaded'
+      } finally {
+        this.loading = false
+      }
+    },
+
+    async fetchUnreadCount(forUser = 'bao') {
+      try {
+        const params = new URLSearchParams({ forUser })
+        const res = await apiFetch(`/api/dashboard/notifications/unread-count?${params}`)
+        if (!res.ok) throw new Error(`HTTP ${res.status}`)
+        const data: UnreadCount = await res.json()
+        this.unreadCount = data.count
+      } catch (err) {
+        console.warn('[NotificationStore] fetchUnreadCount failed', err)
+      }
+    },
+
+    async markAsRead(id: string) {
+      try {
+        const res = await apiFetch(`/api/dashboard/notifications/${id}/read`, { method: 'PATCH' })
+        if (!res.ok) throw new Error(`HTTP ${res.status}`)
+        // Update local state
+        const n = this.notifications.find(n => n.id === id)
+        if (n) n.isRead = true
+        this.unreadCount = Math.max(0, this.unreadCount - 1)
+      } catch (err) {
+        console.warn('[NotificationStore] markAsRead failed', err)
+      }
+    },
+
+    async markAllAsRead(forUser = 'bao') {
+      try {
+        const params = new URLSearchParams({ forUser })
+        const res = await apiFetch(`/api/dashboard/notifications/read-all?${params}`, { method: 'PATCH' })
+        if (!res.ok) throw new Error(`HTTP ${res.status}`)
+        this.notifications.forEach(n => { n.isRead = true })
+        this.unreadCount = 0
+      } catch (err) {
+        console.warn('[NotificationStore] markAllAsRead failed', err)
+      }
+    },
+
+    startPolling(forUser = 'bao') {
+      // Unread count polling every 30s (for sidebar badge)
+      if (!this.countRefreshInterval) {
+        this.fetchUnreadCount(forUser)
+        this.countRefreshInterval = setInterval(() => {
+          this.fetchUnreadCount(forUser)
+        }, 30000)
+      }
+    },
+
+    stopPolling() {
+      if (this.countRefreshInterval) {
+        clearInterval(this.countRefreshInterval)
+        this.countRefreshInterval = null
+      }
+      if (this.listRefreshInterval) {
+        clearInterval(this.listRefreshInterval)
+        this.listRefreshInterval = null
+      }
+    },
+
+    startListPolling(forUser = 'bao') {
+      if (!this.listRefreshInterval) {
+        this.fetchNotifications(forUser)
+        this.listRefreshInterval = setInterval(() => {
+          this.fetchNotifications(forUser)
+        }, 30000)
+      }
+    },
+
+    stopListPolling() {
+      if (this.listRefreshInterval) {
+        clearInterval(this.listRefreshInterval)
+        this.listRefreshInterval = null
+      }
+    },
+  },
+})
diff --git a/frontend/src/stores/tasks.ts b/frontend/src/stores/tasks.ts
index b0ff9fc..ddb1bad 100644
--- a/frontend/src/stores/tasks.ts
+++ b/frontend/src/stores/tasks.ts
@@ -28,6 +28,7 @@ interface DashboardTaskDto {
 export interface BoardGroup {
   offen: DashboardTaskDto[]
   inProgress: DashboardTaskDto[]
+  delegated: DashboardTaskDto[]
   review: DashboardTaskDto[]
   done: DashboardTaskDto[]
   blocked: DashboardTaskDto[]
@@ -82,6 +83,7 @@ export const useTaskStore = defineStore('tasks', {
     board: {
       offen: [] as DashboardTaskDto[],
       inProgress: [] as DashboardTaskDto[],
+      delegated: [] as DashboardTaskDto[],
       review: [] as DashboardTaskDto[],
       done: [] as DashboardTaskDto[],
       blocked: [] as DashboardTaskDto[],
@@ -135,6 +137,7 @@ export const useTaskStore = defineStore('tasks', {
       const canonicalMap: Record<string, string> = {
         offen: 'Backlog',
         inProgress: 'In progress',
+        delegated: 'Delegated',
         review: 'Review',
         done: 'Done',
         blocked: 'Blocked',
@@ -153,6 +156,7 @@ export const useTaskStore = defineStore('tasks', {
       const task =
         findAndRemove(this.board.offen) ??
         findAndRemove(this.board.inProgress) ??
+        findAndRemove(this.board.delegated) ??
         findAndRemove(this.board.review) ??
         findAndRemove(this.board.blocked) ??
         findAndRemove(this.board.done)
diff --git a/frontend/src/views/NotificationsView.vue b/frontend/src/views/NotificationsView.vue
new file mode 100644
index 0000000..96ab968
--- /dev/null
+++ b/frontend/src/views/NotificationsView.vue
@@ -0,0 +1,249 @@
+<script setup lang="ts">
+import { onMounted, onUnmounted, computed } from 'vue'
+import { useRouter } from 'vue-router'
+import { useNotificationStore } from '../stores/notifications'
+import { Bell, BellOff, CheckCheck, ChevronRight } from '@lucide/vue'
+
+const store = useNotificationStore()
+const router = useRouter()
+
+const sortedNotifications = computed(() => {
+  return [...store.notifications].sort(
+    (a, b) => new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime()
+  )
+})
+
+function typeIcon(type: string): string {
+  switch (type) {
+    case 'task_assigned': return '👤'
+    case 'task_review': return '✅'
+    case 'task_blocked': return '🚫'
+    default: return '🔔'
+  }
+}
+
+function typeColor(type: string): string {
+  switch (type) {
+    case 'task_assigned': return '#4d8cf6'
+    case 'task_review': return '#f6a84d'
+    case 'task_blocked': return '#e16e75'
+    default: return '#7b6ef2'
+  }
+}
+
+function timeAgo(dateStr: string): string {
+  const now = Date.now()
+  const then = new Date(dateStr).getTime()
+  const diffSec = Math.floor((now - then) / 1000)
+  if (diffSec < 60) return 'vor ' + diffSec + ' Sek'
+  const diffMin = Math.floor(diffSec / 60)
+  if (diffMin < 60) return 'vor ' + diffMin + ' Min'
+  const diffHr = Math.floor(diffMin / 60)
+  if (diffHr < 24) return 'vor ' + diffHr + ' Std'
+  const diffDay = Math.floor(diffHr / 24)
+  return 'vor ' + diffDay + ' Tag' + (diffDay > 1 ? 'en' : '')
+}
+
+function onNotificationClick(n: { id: string, taskId: string | null }) {
+  if (n.taskId) {
+    router.push('/tasks')
+  }
+  store.markAsRead(n.id)
+}
+
+onMounted(() => {
+  store.startListPolling()
+})
+
+onUnmounted(() => {
+  store.stopListPolling()
+})
+</script>
+
+<template>
+  <div class="notifications-page">
+    <div class="page-header">
+      <h1>
+        <Bell :size="22" />
+        Benachrichtigungen
+      </h1>
+      <button
+        v-if="store.unreadCount > 0"
+        class="mark-all-btn"
+        @click="store.markAllAsRead()"
+      >
+        <CheckCheck :size="15" />
+        Alle als gelesen markieren
+      </button>
+    </div>
+
+    <div v-if="sortedNotifications.length === 0" class="empty-state">
+      <BellOff :size="48" />
+      <p>Keine Benachrichtigungen</p>
+    </div>
+
+    <div v-else class="notification-list">
+      <div
+        v-for="n in sortedNotifications"
+        :key="n.id"
+        :class="['notification-card', { unread: !n.isRead }]"
+        @click="onNotificationClick(n)"
+      >
+        <div class="icon-wrapper" :style="{ background: typeColor(n.type) + '20' }">
+          <span class="type-icon">{{ typeIcon(n.type) }}</span>
+        </div>
+        <div class="card-body">
+          <div :class="['card-title', { bold: !n.isRead }]">{{ n.title }}</div>
+          <div v-if="n.message" class="card-message">{{ n.message }}</div>
+        </div>
+        <div class="card-meta">
+          <span class="timestamp">{{ timeAgo(n.createdAt) }}</span>
+          <ChevronRight v-if="n.taskId" :size="14" class="arrow" />
+        </div>
+      </div>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.notifications-page {
+  max-width: 720px;
+  margin: 0 auto;
+  padding: 24px;
+}
+
+.page-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 24px;
+  gap: 12px;
+}
+
+.page-header h1 {
+  margin: 0;
+  font-size: 20px;
+  display: flex;
+  align-items: center;
+  gap: 10px;
+}
+
+.mark-all-btn {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  padding: 6px 12px;
+  border: 1px solid var(--nx-line, #1f2330);
+  border-radius: 6px;
+  background: transparent;
+  color: var(--nx-text-dim, #6f7889);
+  font-size: 10.5px;
+  cursor: pointer;
+  transition: background .15s, color .15s;
+}
+
+.mark-all-btn:hover {
+  background: var(--nx-accent-soft, rgba(123, 110, 242, .08));
+  color: #d8dbe3;
+}
+
+/* ── Empty State ── */
+.empty-state {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  padding: 80px 0;
+  color: var(--nx-text-dim, #6f7889);
+  gap: 16px;
+}
+
+.empty-state p {
+  font-size: 14px;
+  margin: 0;
+}
+
+/* ── Notification List ── */
+.notification-list {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+}
+
+.notification-card {
+  display: flex;
+  align-items: flex-start;
+  gap: 12px;
+  padding: 12px 14px;
+  border-radius: 8px;
+  cursor: pointer;
+  transition: background .15s;
+  border: 1px solid transparent;
+}
+
+.notification-card:hover {
+  background: var(--nx-accent-soft, rgba(123, 110, 242, .06));
+}
+
+.notification-card.unread {
+  background: rgba(77, 140, 246, .06);
+  border-color: rgba(77, 140, 246, .12);
+}
+
+.icon-wrapper {
+  width: 36px;
+  height: 36px;
+  border-radius: 8px;
+  display: grid;
+  place-items: center;
+  flex-shrink: 0;
+}
+
+.type-icon {
+  font-size: 16px;
+  line-height: 1;
+}
+
+.card-body {
+  flex: 1;
+  min-width: 0;
+}
+
+.card-title {
+  font-size: 12.5px;
+  color: #d8dbe3;
+  line-height: 1.4;
+}
+
+.card-title.bold {
+  font-weight: 700;
+  color: #fff;
+}
+
+.card-message {
+  font-size: 10.5px;
+  color: var(--nx-text-dim, #6f7889);
+  margin-top: 3px;
+  line-height: 1.3;
+}
+
+.card-meta {
+  display: flex;
+  flex-direction: column;
+  align-items: flex-end;
+  gap: 4px;
+  flex-shrink: 0;
+  min-width: 60px;
+}
+
+.timestamp {
+  font-size: 9px;
+  color: var(--nx-text-dim, #6f7889);
+  white-space: nowrap;
+}
+
+.arrow {
+  color: var(--nx-text-dim, #6f7889);
+  opacity: .5;
+}
+</style>
diff --git a/frontend/src/views/TaskBoardView.vue b/frontend/src/views/TaskBoardView.vue
index 5d1a803..8e4e236 100644
--- a/frontend/src/views/TaskBoardView.vue
+++ b/frontend/src/views/TaskBoardView.vue
@@ -218,6 +218,46 @@ onUnmounted(() => {
         </div>
       </div>
 
+      <!-- Delegiert / Delegated -->
+      <div
+        class="col"
+        :class="{ 'drag-over': dragOverColumn === 'delegated' }"
+        @dragover="onDragOver($event, 'delegated')"
+        @dragleave="onDragLeave"
+        @drop="onDrop($event, 'delegated')"
+      >
+        <div class="col-header" style="--col-accent: #a78bfa">
+          <span class="col-name">Delegiert</span>
+          <span class="col-count">{{ taskStore.board.delegated.length }}</span>
+        </div>
+        <div class="col-cards">
+          <div
+            v-for="task in taskStore.board.delegated"
+            :key="task.id"
+            class="card"
+            draggable="true"
+            @dragstart="onDragStart($event, task.id)"
+            @dragend="onDragEnd"
+          >
+            <div class="card-top">
+              <span class="prio-badge" :style="{ color: priorityColor(task.priority) }">
+                {{ priorityLabel(task.priority) }}
+              </span>
+              <span
+                v-if="task.assignedTo"
+                class="assignee"
+                :class="task.assignedTo === 'iris' ? 'assignee-iris' : 'assignee-bao'"
+              >
+                {{ task.assignedTo === 'iris' ? '🤖 Iris' : '👤 Bao' }}
+              </span>
+            </div>
+            <div class="card-title">{{ task.title }}</div>
+            <div class="card-meta">{{ new Date(task.createdAt).toLocaleDateString('de-DE') }}</div>
+          </div>
+          <div v-if="!taskStore.board.delegated.length" class="empty-col">Keine delegierten Aufgaben</div>
+        </div>
+      </div>
+
       <!-- Review -->
       <div
         class="col"