diff --git a/SeaHaven.Services/Helpers/WorkOrderAddonCutoff.cs b/SeaHaven.Services/Helpers/WorkOrderAddonCutoff.cs
index db81e62..886b095 100644
--- a/SeaHaven.Services/Helpers/WorkOrderAddonCutoff.cs
+++ b/SeaHaven.Services/Helpers/WorkOrderAddonCutoff.cs
@@ -3,6 +3,7 @@ namespace SeaHaven.Services.Helpers
     /// <summary>
     /// Server-side Add-On cutoff: Saturday 23:59:59 UTC of the week prior to the schedule week.
     /// SH-184: recalculated whenever scheduling is set, changed, or cleared; audited on change.
+    /// At creation the WO arrives when it is created; on a reschedule it arrives when it is moved.
     /// Create may accept a client hint when unscheduled; schedule present ignores override.
     /// </summary>
     public static class WorkOrderAddonCutoff
@@ -36,14 +37,40 @@ namespace SeaHaven.Services.Helpers
         }
 
         /// <summary>
-        /// SH-184 authoritative recalc after schedule set/change/clear. No manual override on patch.
-        /// Cleared schedule yields false.
+        /// SH-412: a reschedule into another week makes the WO arrive in that week at the moment
+        /// of the reschedule, so Add-On compares <paramref name="rescheduledAtUtc"/> (not the
+        /// creation time) with the new week's cutoff. A move within the same week keeps the
+        /// current value; a cleared schedule yields false. Matches the prototype's reschedule rule.
         /// </summary>
-        public static bool RecalculateIsAddOnFromSchedule(
-            DateTime createdAtUtc,
+        public static bool RecalculateIsAddOnOnReschedule(
+            bool currentIsAddOn,
+            DateTime? previousScheduledDate,
+            DateOnly? previousTargetWeek,
             DateTime? scheduledDate,
-            DateOnly? targetWeek)
-            => ComputeFromScheduleAnchor(createdAtUtc, scheduledDate, targetWeek, manualOverride: false);
+            DateOnly? targetWeek,
+            DateTime rescheduledAtUtc)
+        {
+            var anchor = ScheduleAnchor(scheduledDate, targetWeek);
+            if (!anchor.HasValue)
+                return false;
+
+            var previousAnchor = ScheduleAnchor(previousScheduledDate, previousTargetWeek);
+            if (previousAnchor.HasValue
+                && WorkOrderBoardMutationRules.GetWeekStartMonday(previousAnchor.Value)
+                    == WorkOrderBoardMutationRules.GetWeekStartMonday(anchor.Value))
+                return currentIsAddOn;
+
+            return NormalizeUtc(rescheduledAtUtc) > GetAddonCutoffUtc(anchor.Value);
+        }
+
+        private static DateTime? ScheduleAnchor(DateTime? scheduledDate, DateOnly? targetWeek)
+        {
+            if (scheduledDate.HasValue)
+                return scheduledDate.Value;
+            if (targetWeek.HasValue)
+                return targetWeek.Value.ToDateTime(TimeOnly.MinValue, DateTimeKind.Utc);
+            return null;
+        }
 
         private static bool ComputeFromScheduleAnchor(
             DateTime createdAtUtc,
@@ -51,12 +78,7 @@ namespace SeaHaven.Services.Helpers
             DateOnly? targetWeek,
             bool? manualOverride)
         {
-            DateTime? anchor = null;
-            if (scheduledDate.HasValue)
-                anchor = scheduledDate.Value;
-            else if (targetWeek.HasValue)
-                anchor = targetWeek.Value.ToDateTime(TimeOnly.MinValue, DateTimeKind.Utc);
-
+            var anchor = ScheduleAnchor(scheduledDate, targetWeek);
             if (!anchor.HasValue)
                 return manualOverride ?? false;
 
diff --git a/SeaHaven.Services/Implementation/WorkOrderBoardUpdateService.cs b/SeaHaven.Services/Implementation/WorkOrderBoardUpdateService.cs
index 25e56de..72b26ed 100644
--- a/SeaHaven.Services/Implementation/WorkOrderBoardUpdateService.cs
+++ b/SeaHaven.Services/Implementation/WorkOrderBoardUpdateService.cs
@@ -19,6 +19,7 @@ namespace SeaHaven.Services.Implementation
         private readonly IWorkOrderUpliftService _upliftService;
         private readonly IUpliftDataService _upliftData;
         private readonly IServicesRegistryService? _servicesRegistryService;
+        private readonly TimeProvider _timeProvider;
 
         public WorkOrderBoardUpdateService(
             IWorkOrderBoardDataService boardDataService,
@@ -26,7 +27,8 @@ namespace SeaHaven.Services.Implementation
             IWorkOrderAuditService auditService,
             IWorkOrderUpliftService upliftService,
             IUpliftDataService upliftData,
-            IServicesRegistryService? servicesRegistryService = null)
+            IServicesRegistryService? servicesRegistryService = null,
+            TimeProvider? timeProvider = null)
         {
             _boardDataService = boardDataService;
             _mutationData = mutationData;
@@ -34,6 +36,7 @@ namespace SeaHaven.Services.Implementation
             _upliftService = upliftService;
             _upliftData = upliftData;
             _servicesRegistryService = servicesRegistryService;
+            _timeProvider = timeProvider ?? TimeProvider.System;
         }
 
         public async Task<WorkOrderBoardRowDto> PatchFieldAsync(
@@ -753,9 +756,10 @@ namespace SeaHaven.Services.Implementation
             return FieldChange.ForField(auditField, old, newVal);
         }
 
-        private static List<FieldChange> ApplyScheduledDate(WorkOrder workOrder, string? value, string auditField)
+        private List<FieldChange> ApplyScheduledDate(WorkOrder workOrder, string? value, string auditField)
         {
             var previousDate = workOrder.ScheduledDate;
+            var previousTargetWeek = workOrder.TargetWeek;
             DateTime? parsed = null;
             if (!string.IsNullOrWhiteSpace(value))
             {
@@ -790,12 +794,14 @@ namespace SeaHaven.Services.Implementation
             }
 
             changes.AddRange(ApplyAutoScheduleSideEffects(workOrder));
-            AppendIsAddOnRecalculation(workOrder, changes);
+            AppendIsAddOnRecalculation(workOrder, previousDate, previousTargetWeek, changes);
             return changes;
         }
 
-        private static List<FieldChange> ApplyTargetWeek(WorkOrder workOrder, string? value, string auditField)
+        private List<FieldChange> ApplyTargetWeek(WorkOrder workOrder, string? value, string auditField)
         {
+            var previousDate = workOrder.ScheduledDate;
+            var previousTargetWeek = workOrder.TargetWeek;
             DateOnly? parsed = null;
             if (!string.IsNullOrWhiteSpace(value))
             {
@@ -813,28 +819,33 @@ namespace SeaHaven.Services.Implementation
                 changes.Add(FieldChange.ForField(auditField, old, newVal));
             }
 
-            AppendIsAddOnRecalculation(workOrder, changes);
+            AppendIsAddOnRecalculation(workOrder, previousDate, previousTargetWeek, changes);
             return changes;
         }
 
+        // Toggling week-only mode keeps the scheduled week, so Add-On is unchanged (SH-412).
         private static List<FieldChange> ApplyScheduleWeekOnly(WorkOrder workOrder, string? value, string auditField)
         {
             var change = ApplyBoolField(value, auditField, v => workOrder.ScheduleWeekOnly = v, () => workOrder.ScheduleWeekOnly);
             var changes = new List<FieldChange> { change };
-            if (change.HasChanged)
-                AppendIsAddOnRecalculation(workOrder, changes);
             changes.AddRange(ApplyAutoScheduleSideEffects(workOrder));
             return changes;
         }
 
-        private static void AppendIsAddOnRecalculation(WorkOrder workOrder, List<FieldChange> changes)
+        private void AppendIsAddOnRecalculation(
+            WorkOrder workOrder,
+            DateTime? previousScheduledDate,
+            DateOnly? previousTargetWeek,
+            List<FieldChange> changes)
         {
-            var createdAt = workOrder.CreatedDate ?? DateTime.UtcNow;
             var oldValue = workOrder.IsAddOn.ToString();
-            var newIsAddOn = WorkOrderAddonCutoff.RecalculateIsAddOnFromSchedule(
-                createdAt,
+            var newIsAddOn = WorkOrderAddonCutoff.RecalculateIsAddOnOnReschedule(
+                workOrder.IsAddOn,
+                previousScheduledDate,
+                previousTargetWeek,
                 workOrder.ScheduledDate,
-                workOrder.TargetWeek);
+                workOrder.TargetWeek,
+                _timeProvider.GetUtcNow().UtcDateTime);
 
             if (workOrder.IsAddOn == newIsAddOn)
                 return;
diff --git a/SeaHaven.Services/Implementation/WorkOrderService.cs b/SeaHaven.Services/Implementation/WorkOrderService.cs
index 132cbe5..3670ad2 100644
--- a/SeaHaven.Services/Implementation/WorkOrderService.cs
+++ b/SeaHaven.Services/Implementation/WorkOrderService.cs
@@ -22,6 +22,7 @@ namespace SeaHaven.Services.Implementation
         private readonly ICreateWorkOrderValidation _createValidator;
         private readonly IUpdateWorkOrderValidation _updateValidator;
         private readonly IWorkOrderAccountResolver _accountResolver;
+        private readonly TimeProvider _timeProvider;
 
         public WorkOrderService(
             IWorkOrderDataService workOrderDataService,
@@ -31,7 +32,8 @@ namespace SeaHaven.Services.Implementation
             IFileStoragePort fileStorage,
             ICreateWorkOrderValidation createValidator,
             IUpdateWorkOrderValidation updateValidator,
-            IWorkOrderAccountResolver accountResolver)
+            IWorkOrderAccountResolver accountResolver,
+            TimeProvider? timeProvider = null)
         {
             _workOrderDataService = workOrderDataService;
             _commentDataService = commentDataService;
@@ -41,6 +43,7 @@ namespace SeaHaven.Services.Implementation
             _createValidator = createValidator;
             _updateValidator = updateValidator;
             _accountResolver = accountResolver;
+            _timeProvider = timeProvider ?? TimeProvider.System;
         }
 
         public async Task<WorkOrderDTO?> GetWorkOrderByIdAsync(int id)
@@ -116,6 +119,8 @@ namespace SeaHaven.Services.Implementation
                     var scheduledDateChanged = dto.ScheduledDate.HasValue
                         && dto.ScheduledDate.Value.Date != existingWorkOrder.ScheduledDate?.Date;
                     var previousIsAddOn = existingWorkOrder.IsAddOn;
+                    var previousScheduledDate = existingWorkOrder.ScheduledDate;
+                    var previousTargetWeek = existingWorkOrder.TargetWeek;
                     UpdateWorkOrderDTO.UpdateEntity(dto, existingWorkOrder);
                     if (scheduledDateChanged)
                     {
@@ -126,10 +131,13 @@ namespace SeaHaven.Services.Implementation
                         changes.AddRange(scheduleChanges
                             .Where(c => c.HasChanged && c.FieldName != WorkOrderBoardFieldNames.ScheduledDate)
                             .Select(c => $"{c.FieldName}: {c.OldValue} → {c.NewValue}"));
-                        existingWorkOrder.IsAddOn = WorkOrderAddonCutoff.RecalculateIsAddOnFromSchedule(
-                            existingWorkOrder.CreatedDate ?? DateTime.UtcNow,
+                        existingWorkOrder.IsAddOn = WorkOrderAddonCutoff.RecalculateIsAddOnOnReschedule(
+                            previousIsAddOn,
+                            previousScheduledDate,
+                            previousTargetWeek,
                             existingWorkOrder.ScheduledDate,
-                            existingWorkOrder.TargetWeek);
+                            existingWorkOrder.TargetWeek,
+                            _timeProvider.GetUtcNow().UtcDateTime);
                         if (existingWorkOrder.IsAddOn != previousIsAddOn)
                             changes.Add($"IsAddOn: {previousIsAddOn} → {existingWorkOrder.IsAddOn}");
                     }
diff --git a/SeaHavenIndustries.Tests/WorkOrderAccountTestHelpers.cs b/SeaHavenIndustries.Tests/WorkOrderAccountTestHelpers.cs
index 040e235..9c33645 100644
--- a/SeaHavenIndustries.Tests/WorkOrderAccountTestHelpers.cs
+++ b/SeaHavenIndustries.Tests/WorkOrderAccountTestHelpers.cs
@@ -19,14 +19,16 @@ internal static class WorkOrderAccountTestHelpers
     public static WorkOrderBoardUpdateService BoardUpdateService(
         ApplicationDbContext context,
         IWorkOrderAuditService audit,
-        IServicesRegistryService? servicesRegistry = null)
+        IServicesRegistryService? servicesRegistry = null,
+        TimeProvider? timeProvider = null)
         => new(
             new WorkOrderBoardDataService(context),
             new WorkOrderBoardMutationDataService(context),
             audit,
             UpliftService(context),
             new UpliftDataService(context),
-            servicesRegistry);
+            servicesRegistry,
+            timeProvider);
 
     public static WorkOrderUpliftService UpliftService(ApplicationDbContext context)
         => new(
diff --git a/SeaHavenIndustries.Tests/WorkOrderAddonCutoffTests.cs b/SeaHavenIndustries.Tests/WorkOrderAddonCutoffTests.cs
index d860482..91b4623 100644
--- a/SeaHavenIndustries.Tests/WorkOrderAddonCutoffTests.cs
+++ b/SeaHavenIndustries.Tests/WorkOrderAddonCutoffTests.cs
@@ -114,21 +114,78 @@ public class WorkOrderAddonCutoffTests
         Assert.True(result);
     }
 
+    // Rescheduled on Wed 2026-06-24: the week of 06-22 is past its cutoff (Sat 06-20 23:59:59),
+    // the week of 06-29 is not (cutoff Sat 06-27 23:59:59).
+    private static readonly DateTime RescheduledAt = new(2026, 6, 24, 10, 0, 0, DateTimeKind.Utc);
+
     [Fact]
-    public void RecalculateIsAddOnFromSchedule_NoSchedule_ReturnsFalse()
+    public void RecalculateOnReschedule_NoSchedule_ReturnsFalse()
     {
-        var created = new DateTime(2026, 6, 21, 0, 0, 0, DateTimeKind.Utc);
-        Assert.False(WorkOrderAddonCutoff.RecalculateIsAddOnFromSchedule(created, null, null));
+        Assert.False(WorkOrderAddonCutoff.RecalculateIsAddOnOnReschedule(
+            currentIsAddOn: true,
+            previousScheduledDate: new DateTime(2026, 6, 24),
+            previousTargetWeek: null,
+            scheduledDate: null,
+            targetWeek: null,
+            RescheduledAt));
     }
 
     [Fact]
-    public void RecalculateIsAddOnFromSchedule_AfterCutoff_ReturnsTrue()
+    public void RecalculateOnReschedule_IntoWeekPastCutoff_TurnsOnForWorkOrderCreatedLongBefore()
     {
-        var created = new DateTime(2026, 6, 21, 0, 0, 0, DateTimeKind.Utc);
-        var result = WorkOrderAddonCutoff.RecalculateIsAddOnFromSchedule(
-            created,
-            scheduledDate: new DateTime(2026, 6, 24),
-            targetWeek: null);
+        // SH-412: the WO was created weeks earlier; it arrives in the current week at the
+        // moment of the reschedule, which is already past that week's cutoff.
+        var result = WorkOrderAddonCutoff.RecalculateIsAddOnOnReschedule(
+            currentIsAddOn: false,
+            previousScheduledDate: new DateTime(2026, 7, 8),
+            previousTargetWeek: null,
+            scheduledDate: new DateTime(2026, 6, 25),
+            targetWeek: null,
+            RescheduledAt);
+
+        Assert.True(result);
+    }
+
+    [Fact]
+    public void RecalculateOnReschedule_IntoWeekBeforeCutoff_TurnsOff()
+    {
+        var result = WorkOrderAddonCutoff.RecalculateIsAddOnOnReschedule(
+            currentIsAddOn: true,
+            previousScheduledDate: new DateTime(2026, 6, 24),
+            previousTargetWeek: null,
+            scheduledDate: new DateTime(2026, 7, 1),
+            targetWeek: null,
+            RescheduledAt);
+
+        Assert.False(result);
+    }
+
+    [Theory]
+    [InlineData(true)]
+    [InlineData(false)]
+    public void RecalculateOnReschedule_WithinSameWeek_KeepsCurrentValue(bool currentIsAddOn)
+    {
+        var result = WorkOrderAddonCutoff.RecalculateIsAddOnOnReschedule(
+            currentIsAddOn,
+            previousScheduledDate: new DateTime(2026, 6, 22),
+            previousTargetWeek: null,
+            scheduledDate: new DateTime(2026, 6, 26),
+            targetWeek: null,
+            RescheduledAt);
+
+        Assert.Equal(currentIsAddOn, result);
+    }
+
+    [Fact]
+    public void RecalculateOnReschedule_FirstScheduleIntoWeekPastCutoff_TurnsOn()
+    {
+        var result = WorkOrderAddonCutoff.RecalculateIsAddOnOnReschedule(
+            currentIsAddOn: false,
+            previousScheduledDate: null,
+            previousTargetWeek: null,
+            scheduledDate: new DateTime(2026, 6, 26),
+            targetWeek: null,
+            RescheduledAt);
 
         Assert.True(result);
     }
diff --git a/SeaHavenIndustries.Tests/WorkOrderBoardUpdateServiceTests.cs b/SeaHavenIndustries.Tests/WorkOrderBoardUpdateServiceTests.cs
index 9901e3a..0cf861b 100644
--- a/SeaHavenIndustries.Tests/WorkOrderBoardUpdateServiceTests.cs
+++ b/SeaHavenIndustries.Tests/WorkOrderBoardUpdateServiceTests.cs
@@ -13,7 +13,8 @@ namespace SeaHavenIndustries.Tests;
 
 public class WorkOrderBoardUpdateServiceTests
 {
-    private static (ApplicationDbContext Context, WorkOrderBoardUpdateService Service) CreateSut()
+    private static (ApplicationDbContext Context, WorkOrderBoardUpdateService Service) CreateSut(
+        TimeProvider? timeProvider = null)
     {
         var options = new DbContextOptionsBuilder<ApplicationDbContext>()
             .UseInMemoryDatabase(Guid.NewGuid().ToString())
@@ -23,10 +24,16 @@ public class WorkOrderBoardUpdateServiceTests
         var mutationData = new WorkOrderBoardMutationDataService(context);
         var fieldLocks = new WorkOrderFieldLockService(new WorkOrderFieldLockDataService(context));
         var audit = new WorkOrderAuditService(new WorkOrderAuditDataService(context), fieldLocks);
-        var service = WorkOrderAccountTestHelpers.BoardUpdateService(context, audit);
+        var service = WorkOrderAccountTestHelpers.BoardUpdateService(context, audit, timeProvider: timeProvider);
         return (context, service);
     }
 
+    // Wed 2026-06-24: the week of 06-22 is past its cutoff, the week of 06-29 is not.
+    private sealed class FixedTimeProvider : TimeProvider
+    {
+        public override DateTimeOffset GetUtcNow() => new(2026, 6, 24, 10, 0, 0, TimeSpan.Zero);
+    }
+
     private static string ToVersion(WorkOrder workOrder)
         => Convert.ToBase64String(workOrder.RowVersion ?? new byte[] { 1, 0, 0, 0, 0, 0, 0, 1 });
 
@@ -2260,6 +2267,46 @@ public class WorkOrderBoardUpdateServiceTests
         Assert.True(persisted.IsAddOn);
     }
 
+    [Theory]
+    [InlineData("2026-07-08", false, "2026-06-25", true)]  // into the current week, past its cutoff
+    [InlineData("2026-06-24", true, "2026-07-01", false)]  // into next week, before its cutoff
+    [InlineData("2026-07-06", false, "2026-07-09", false)] // same week: unchanged
+    [InlineData("2026-06-22", true, "2026-06-26", true)]   // same week: unchanged
+    public async Task PatchField_ScheduledDate_RecalculatesIsAddOnAtRescheduleTime(
+        string from,
+        bool isAddOn,
+        string to,
+        bool expectedIsAddOn)
+    {
+        var (context, service) = CreateSut(new FixedTimeProvider());
+        var wo = new WorkOrder
+        {
+            Id = 1,
+            LifecycleStatus = LifecycleStatus.Scheduled,
+            WorkOrderType = WorkOrderType.PM,
+            ScheduledDate = DateTime.Parse(from),
+            // Created weeks before any of these cutoffs: creation time must not decide (SH-412).
+            CreatedDate = new DateTime(2026, 6, 1, 0, 0, 0, DateTimeKind.Utc),
+            IsAddOn = isAddOn,
+            RowVersion = new byte[] { 1, 0, 0, 0, 0, 0, 0, 1 }
+        };
+        context.workOrders.Add(wo);
+        await context.SaveChangesAsync();
+
+        var result = await service.PatchFieldAsync(1, new WorkOrderBoardPatchRequestDto
+        {
+            Field = WorkOrderBoardFieldNames.ScheduledDate,
+            Value = to,
+            WorkOrderVersion = ToVersion(wo)
+        }, "actor-1");
+
+        Assert.Equal(expectedIsAddOn, result.IsAddOn);
+        var persisted = await context.workOrders.SingleAsync(w => w.Id == 1);
+        Assert.Equal(expectedIsAddOn, persisted.IsAddOn);
+        var addOnAudits = await context.WorkOrderAuditLogs.Where(a => a.FieldName == "IsAddOn").ToListAsync();
+        Assert.Equal(isAddOn == expectedIsAddOn ? 0 : 1, addOnAudits.Count);
+    }
+
     [Fact]
     public async Task PatchField_WorkOrderType_DoesNotRecalculateIsAddOn()
     {
diff --git a/SeaHavenIndustries.Tests/WorkOrderEditAddonRescheduleTests.cs b/SeaHavenIndustries.Tests/WorkOrderEditAddonRescheduleTests.cs
index 328e4f2..0748c9f 100644
--- a/SeaHavenIndustries.Tests/WorkOrderEditAddonRescheduleTests.cs
+++ b/SeaHavenIndustries.Tests/WorkOrderEditAddonRescheduleTests.cs
@@ -49,6 +49,86 @@ public sealed class WorkOrderEditAddonRescheduleTests
         Assert.Contains(audit, x => x.FieldName?.Contains("RescheduleCount: 0 → 1", StringComparison.Ordinal) == true);
     }
 
+    [Fact]
+    public async Task EditWorkorder_RescheduleOlderWorkOrderIntoWeekPastCutoff_EnablesAndAuditsAddOn()
+    {
+        // SH-412 retest: the WO was created weeks before the target week's cutoff, so the
+        // creation-time rule kept Add-On off. It arrives in the week when it is rescheduled.
+        await using var context = CreateContext();
+        context.workOrders.Add(new WorkOrder
+        {
+            Id = 1,
+            CreatedDate = new DateTime(2026, 6, 1, 0, 0, 0, DateTimeKind.Utc),
+            ScheduledDate = new DateTime(2026, 7, 8),
+            IsAddOn = false
+        });
+        await context.SaveChangesAsync();
+
+        var result = await CreateController(context, new FixedTimeProvider()).Editworkorder(new EditWorkorder_DTO
+        {
+            Id = 1,
+            ScheduledDate = new DateTime(2026, 6, 25)
+        });
+
+        Assert.IsType<OkObjectResult>(result);
+        var persisted = await context.workOrders.SingleAsync(x => x.Id == 1);
+        Assert.True(persisted.IsAddOn);
+        var audit = await context.WorkOrderAuditLogs.SingleAsync(x => x.WorkOrderId == 1);
+        Assert.Contains("IsAddOn: False → True", audit.FieldName);
+    }
+
+    [Fact]
+    public async Task EditWorkorder_RescheduleIntoWeekBeforeCutoff_ClearsAndAuditsAddOn()
+    {
+        await using var context = CreateContext();
+        context.workOrders.Add(new WorkOrder
+        {
+            Id = 1,
+            CreatedDate = new DateTime(2026, 6, 23, 0, 0, 0, DateTimeKind.Utc),
+            ScheduledDate = new DateTime(2026, 6, 24),
+            IsAddOn = true
+        });
+        await context.SaveChangesAsync();
+
+        var result = await CreateController(context, new FixedTimeProvider()).Editworkorder(new EditWorkorder_DTO
+        {
+            Id = 1,
+            ScheduledDate = new DateTime(2026, 7, 1)
+        });
+
+        Assert.IsType<OkObjectResult>(result);
+        var persisted = await context.workOrders.SingleAsync(x => x.Id == 1);
+        Assert.False(persisted.IsAddOn);
+        var audit = await context.WorkOrderAuditLogs.SingleAsync(x => x.WorkOrderId == 1);
+        Assert.Contains("IsAddOn: True → False", audit.FieldName);
+    }
+
+    [Fact]
+    public async Task EditWorkorder_RescheduleWithinSameWeek_KeepsAddOn()
+    {
+        await using var context = CreateContext();
+        context.workOrders.Add(new WorkOrder
+        {
+            Id = 1,
+            CreatedDate = new DateTime(2026, 6, 1, 0, 0, 0, DateTimeKind.Utc),
+            ScheduledDate = new DateTime(2026, 7, 6),
+            IsAddOn = false
+        });
+        await context.SaveChangesAsync();
+
+        var result = await CreateController(context, new FixedTimeProvider()).Editworkorder(new EditWorkorder_DTO
+        {
+            Id = 1,
+            ScheduledDate = new DateTime(2026, 7, 9)
+        });
+
+        Assert.IsType<OkObjectResult>(result);
+        var persisted = await context.workOrders.SingleAsync(x => x.Id == 1);
+        Assert.False(persisted.IsAddOn);
+        var audit = await context.WorkOrderAuditLogs.SingleAsync(x => x.WorkOrderId == 1);
+        Assert.DoesNotContain("IsAddOn", audit.FieldName);
+    }
+
     [Fact]
     public async Task EditWorkorder_FirstSchedule_SetsOriginalWeekAndPromotesIncomplete()
     {
@@ -145,7 +225,15 @@ public sealed class WorkOrderEditAddonRescheduleTests
         return new ApplicationDbContext(options);
     }
 
-    private static WorkOrderController CreateController(ApplicationDbContext context)
+    // Wed 2026-06-24: the week of 06-22 is past its cutoff, the week of 06-29 is not.
+    private sealed class FixedTimeProvider : TimeProvider
+    {
+        public override DateTimeOffset GetUtcNow() => new(2026, 6, 24, 10, 0, 0, TimeSpan.Zero);
+    }
+
+    private static WorkOrderController CreateController(
+        ApplicationDbContext context,
+        TimeProvider? timeProvider = null)
     {
         var accountResolver = WorkOrderAccountTestHelpers.Resolver(context);
         var workOrderService = new WorkOrderService(
@@ -156,7 +244,8 @@ public sealed class WorkOrderEditAddonRescheduleTests
             fileStorage: null!,
             new CreateWorkOrderValidation(),
             new UpdateWorkOrderValidation(),
-            accountResolver);
+            accountResolver,
+            timeProvider);
         return new WorkOrderController(
             workOrderService,
             accountResolver,