fix(user-tasks): align query sort and cursor contract across providers (#8144)

* fix(user-tasks): align query sort and cursor contract across providers

Implement the REST updated sort on EF and VNext, drop the InMemory-only
completed sort, and use one always-ascending Id tiebreaker plus the
production JSON base64url cursor codec in every repository.

Closes #8110

Co-authored-by: Sipke Schoorstra <sipkeschoorstra@outlook.com>

* fix(user-tasks): keep title cursor ties comparison-consistent

Use the same string.Compare relation for title ordering and cursor
tie detection so culture-equal Unicode forms are not skipped. Assert
updated sort order directly so a created fallback cannot pass.

Co-authored-by: Sipke Schoorstra <sipkeschoorstra@outlook.com>

* fix(user-tasks): use one ordinal comparer for title sort and cursors

OrderBy, title-tie detection, and cursor filtering now share
StringComparer.Ordinal on the LINQ-to-objects providers so Unicode
variants cannot skip a page.

Co-authored-by: Sipke Schoorstra <sipkeschoorstra@outlook.com>

* fix(user-tasks): share default title comparison across providers

InMemory and VNext title sort/cursors now use the same OrderBy plus
string.Compare relation as EF (SQL collation / current culture) so a
title cursor stays portable. Ties still use Compare == 0, not ordinal ==.

Co-authored-by: Sipke Schoorstra <sipkeschoorstra@outlook.com>

* docs(user-tasks): title cursors are provider-scoped, not portable

Restore InMemory/VNext ordinal title OrderBy/tie/cursor (EF stays
column-collation). Document that title pages must be recreated after a
provider or collation change; other sorts plus Id stay portable.

Co-authored-by: Sipke Schoorstra <sipkeschoorstra@outlook.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

specs/013-user-tasks/contracts/rest-api.md

@@ -24,7 +24,7 @@ The descriptor is advisory: it decides what a client renders, never what the ser
 
 `GET /user-tasks?scope=assigned|available|history|all|needsAttention&cursor=&limit=&sort=&direction=&status=&priorityFrom=&priorityTo=&due=&from=&to=&workflowDefinitionId=&workflowInstanceId=&reference=&taskType=&search=&includeTotalCount=`
 
-Returns `{ items, nextCursor, totalCount? }`. Default/max limit: 50/200. Stable sorts: created, due, priority, title, updated, each with an ID tiebreaker.
+Returns `{ items, nextCursor, totalCount? }`. Default/max limit: 50/200. Stable sorts: created, due, priority, title, updated, each with an always-ascending ID tiebreaker. Title cursors are **not** portable across persistence providers or database collations (InMemory/VNext use ordinal title comparison; EF uses column collation) — recreate the list after a provider change. `created`, `updated`, `due`, `priority`, and the Id tiebreaker remain the portable page stream.
 
 - `scope` is part of the authorization predicate, not a display filter. `all` and `needsAttention` require manager scope and answer `403` — not an empty page — for anyone else.
 - `status` is repeatable. Unknown values are dropped rather than rejected, so a stale bookmark still loads.

src/modules/Elsa.UserTasks.Persistence.EFCore/Repositories/EFCoreUserTaskRepository.cs

@@ -349,14 +349,19 @@ public sealed class EFCoreUserTaskRepository(Store<UserTasksElsaDbContext, UserT
 
     private static IQueryable<UserTaskRecord> ApplyOrdering(IQueryable<UserTaskRecord> records, UserTaskQuery query)
     {
+        // Id is always ThenBy ascending so a page of ties is the same in both directions and across providers.
         return query.Sort.ToLowerInvariant() switch
         {
             "due" when query.Descending => records.OrderBy(x => x.DueAt == null).ThenByDescending(x => x.DueAt).ThenBy(x => x.Id),
             "due" => records.OrderBy(x => x.DueAt == null).ThenBy(x => x.DueAt).ThenBy(x => x.Id),
             "priority" when query.Descending => records.OrderByDescending(x => x.Priority).ThenBy(x => x.Id),
             "priority" => records.OrderBy(x => x.Priority).ThenBy(x => x.Id),
+            // Title OrderBy and cursor use column collation (self-consistent). Title cursors are not
+            // portable to InMemory/VNext ordinal comparison; recreate the list after a provider change.
             "title" when query.Descending => records.OrderByDescending(x => x.Title).ThenBy(x => x.Id),
             "title" => records.OrderBy(x => x.Title).ThenBy(x => x.Id),
+            "updated" when query.Descending => records.OrderByDescending(x => x.UpdatedAt).ThenBy(x => x.Id),
+            "updated" => records.OrderBy(x => x.UpdatedAt).ThenBy(x => x.Id),
             _ when query.Descending => records.OrderByDescending(x => x.CreatedAt).ThenBy(x => x.Id),
             _ => records.OrderBy(x => x.CreatedAt).ThenBy(x => x.Id)
         };
@@ -373,12 +378,15 @@ public sealed class EFCoreUserTaskRepository(Store<UserTasksElsaDbContext, UserT
                 ? records.Where(x => x.Priority < priority || (x.Priority == priority && string.Compare(x.Id, cursorId) > 0))
                 : records.Where(x => x.Priority > priority || (x.Priority == priority && string.Compare(x.Id, cursorId) > 0)),
             "title" => query.Descending
-                ? records.Where(x => string.Compare(x.Title, cursorValue) < 0 || (x.Title == cursorValue && string.Compare(x.Id, cursorId) > 0))
+                ? records.Where(x => string.Compare(x.Title, cursorValue) < 0 || (string.Compare(x.Title, cursorValue) == 0 && string.Compare(x.Id, cursorId) > 0))
-                : records.Where(x => string.Compare(x.Title, cursorValue) > 0 || (x.Title == cursorValue && string.Compare(x.Id, cursorId) > 0)),
+                : records.Where(x => string.Compare(x.Title, cursorValue) > 0 || (string.Compare(x.Title, cursorValue) == 0 && string.Compare(x.Id, cursorId) > 0)),
             "due" when cursorValue == "~null" => records.Where(x => x.DueAt == null && string.Compare(x.Id, cursorId) > 0),
             "due" when DateTimeOffset.TryParse(cursorValue, out var dueAt) => query.Descending
                 ? records.Where(x => x.DueAt == null || x.DueAt < dueAt || (x.DueAt == dueAt && string.Compare(x.Id, cursorId) > 0))
                 : records.Where(x => x.DueAt == null || x.DueAt > dueAt || (x.DueAt == dueAt && string.Compare(x.Id, cursorId) > 0)),
+            "updated" when DateTimeOffset.TryParse(cursorValue, out var updatedAt) => query.Descending
+                ? records.Where(x => x.UpdatedAt < updatedAt || (x.UpdatedAt == updatedAt && string.Compare(x.Id, cursorId) > 0))
+                : records.Where(x => x.UpdatedAt > updatedAt || (x.UpdatedAt == updatedAt && string.Compare(x.Id, cursorId) > 0)),
             _ when DateTimeOffset.TryParse(cursorValue, out var createdAt) => query.Descending
                 ? records.Where(x => x.CreatedAt < createdAt || (x.CreatedAt == createdAt && string.Compare(x.Id, cursorId) > 0))
                 : records.Where(x => x.CreatedAt > createdAt || (x.CreatedAt == createdAt && string.Compare(x.Id, cursorId) > 0)),
@@ -393,6 +401,7 @@ public sealed class EFCoreUserTaskRepository(Store<UserTasksElsaDbContext, UserT
             "priority" => record.Priority.ToString(System.Globalization.CultureInfo.InvariantCulture),
             "title" => record.Title,
             "due" => record.DueAt?.ToString("O", System.Globalization.CultureInfo.InvariantCulture) ?? "~null",
+            "updated" => record.UpdatedAt.ToString("O", System.Globalization.CultureInfo.InvariantCulture),
             _ => record.CreatedAt.ToString("O", System.Globalization.CultureInfo.InvariantCulture)
         };
         return Convert.ToBase64String(JsonSerializer.SerializeToUtf8Bytes(new[] { value, record.Id }, JsonOptions))

src/modules/Elsa.UserTasks.Persistence.VNext/Repositories/VNextUserTaskRepository.cs

@@ -18,6 +18,12 @@ public sealed class VNextUserTaskRepository(IDocumentStore documentStore) : IUse
         Converters = { new JsonStringEnumConverter() }
     };
 
+    /// <summary>
+    /// Title OrderBy, ties, and cursors share this comparer. Title cursors are not portable to EF
+    /// (column collation) or across databases; recreate the list after a provider change.
+    /// </summary>
+    private static readonly StringComparer TitleComparer = StringComparer.Ordinal;
+
     public async Task<UserTask?> GetAsync(string tenantId, string taskId, CancellationToken cancellationToken = default)
     {
         var document = await documentStore.LoadAsync(StorageUnitName, DocumentId(tenantId, taskId), cancellationToken);
@@ -270,11 +276,13 @@ public sealed class VNextUserTaskRepository(IDocumentStore documentStore) : IUse
         || (task.IsOpen && task.Assignee is null)
         || task.Status is UserTaskStatus.Completing or UserTaskStatus.TimingOut or UserTaskStatus.Cancelling;
 
+    // Id is always ThenBy ascending so a page of ties is the same in both directions and across providers.
     private static IEnumerable<UserTask> ApplyOrdering(IEnumerable<UserTask> tasks, UserTaskQuery query) => query.Sort.ToLowerInvariant() switch
     {
         "priority" => query.Descending ? tasks.OrderByDescending(x => x.Priority).ThenBy(x => x.Id) : tasks.OrderBy(x => x.Priority).ThenBy(x => x.Id),
-        "title" => query.Descending ? tasks.OrderByDescending(x => x.Title).ThenBy(x => x.Id) : tasks.OrderBy(x => x.Title).ThenBy(x => x.Id),
+        "title" => query.Descending ? tasks.OrderByDescending(x => x.Title, TitleComparer).ThenBy(x => x.Id) : tasks.OrderBy(x => x.Title, TitleComparer).ThenBy(x => x.Id),
         "due" => query.Descending ? tasks.OrderBy(x => x.DueAt == null).ThenByDescending(x => x.DueAt).ThenBy(x => x.Id) : tasks.OrderBy(x => x.DueAt == null).ThenBy(x => x.DueAt).ThenBy(x => x.Id),
+        "updated" => query.Descending ? tasks.OrderByDescending(x => x.UpdatedAt).ThenBy(x => x.Id) : tasks.OrderBy(x => x.UpdatedAt).ThenBy(x => x.Id),
         _ => query.Descending ? tasks.OrderByDescending(x => x.CreatedAt).ThenBy(x => x.Id) : tasks.OrderBy(x => x.CreatedAt).ThenBy(x => x.Id)
     };
 
@@ -285,14 +293,23 @@ public sealed class VNextUserTaskRepository(IDocumentStore documentStore) : IUse
         return query.Sort.ToLowerInvariant() switch
         {
             "priority" when int.TryParse(value, out var priority) => tasks.Where(x => query.Descending ? x.Priority < priority || x.Priority == priority && string.Compare(x.Id, id) > 0 : x.Priority > priority || x.Priority == priority && string.Compare(x.Id, id) > 0),
-            "title" => tasks.Where(x => query.Descending ? string.Compare(x.Title, value) < 0 || x.Title == value && string.Compare(x.Id, id) > 0 : string.Compare(x.Title, value) > 0 || x.Title == value && string.Compare(x.Id, id) > 0),
+            "title" => tasks.Where(x => TitleIsAfterCursor(x.Title, value, x.Id, id, query.Descending)),
             "due" when value == "~null" => tasks.Where(x => x.DueAt == null && string.Compare(x.Id, id) > 0),
             "due" when DateTimeOffset.TryParse(value, out var due) => tasks.Where(x => x.DueAt == null || query.Descending && x.DueAt < due || !query.Descending && x.DueAt > due || x.DueAt == due && string.Compare(x.Id, id) > 0),
+            "updated" when DateTimeOffset.TryParse(value, out var updated) => tasks.Where(x => query.Descending ? x.UpdatedAt < updated || x.UpdatedAt == updated && string.Compare(x.Id, id) > 0 : x.UpdatedAt > updated || x.UpdatedAt == updated && string.Compare(x.Id, id) > 0),
             _ when DateTimeOffset.TryParse(value, out var created) => tasks.Where(x => query.Descending ? x.CreatedAt < created || x.CreatedAt == created && string.Compare(x.Id, id) > 0 : x.CreatedAt > created || x.CreatedAt == created && string.Compare(x.Id, id) > 0),
             _ => tasks
         };
     }
 
+    private static bool TitleIsAfterCursor(string title, string cursorTitle, string id, string cursorId, bool descending)
+    {
+        var comparison = TitleComparer.Compare(title, cursorTitle);
+        return descending
+            ? comparison < 0 || comparison == 0 && string.Compare(id, cursorId) > 0
+            : comparison > 0 || comparison == 0 && string.Compare(id, cursorId) > 0;
+    }
+
     private static string CreateCursor(UserTask task, string sort)
     {
         var value = sort.ToLowerInvariant() switch
@@ -300,6 +317,7 @@ public sealed class VNextUserTaskRepository(IDocumentStore documentStore) : IUse
             "priority" => task.Priority.ToString(System.Globalization.CultureInfo.InvariantCulture),
             "title" => task.Title,
             "due" => task.DueAt?.ToString("O", System.Globalization.CultureInfo.InvariantCulture) ?? "~null",
+            "updated" => task.UpdatedAt.ToString("O", System.Globalization.CultureInfo.InvariantCulture),
             _ => task.CreatedAt.ToString("O", System.Globalization.CultureInfo.InvariantCulture)
         };
         return Convert.ToBase64String(JsonSerializer.SerializeToUtf8Bytes(new[] { value, task.Id }, JsonOptions)).TrimEnd('=').Replace('+', '-').Replace('/', '_');

src/modules/Elsa.UserTasks/Repositories/InMemoryUserTaskRepository.cs

@@ -1,5 +1,5 @@
-using System.Text;
 using System.Text.Json;
+using System.Text.Json.Serialization;
 using Elsa.UserTasks.Contracts;
 using Elsa.UserTasks.Models;
 
@@ -11,6 +11,17 @@ namespace Elsa.UserTasks.Repositories;
 /// </summary>
 public sealed class InMemoryUserTaskRepository : IUserTaskRepository
 {
+    private static readonly JsonSerializerOptions JsonOptions = new(JsonSerializerDefaults.Web)
+    {
+        Converters = { new JsonStringEnumConverter() }
+    };
+
+    /// <summary>
+    /// Title OrderBy, ties, and cursors share this comparer. Title cursors are not portable to EF
+    /// (column collation) or across databases; recreate the list after a provider change.
+    /// </summary>
+    private static readonly StringComparer TitleComparer = StringComparer.Ordinal;
+
     private readonly object _sync = new();
     private readonly Dictionary<string, UserTask> _tasks = new(StringComparer.Ordinal);
 
@@ -44,14 +55,13 @@ public sealed class InMemoryUserTaskRepository : IUserTaskRepository
                 .Where(x => MatchesSearch(x, query.Search));
 
             var filteredCount = query.IncludeTotalCount ? items.Count() : 0;
-            var materialized = Sort(items, query.Sort, query.Descending).ToList();
+            var materialized = ApplyOrdering(items, query).ToList();
-            if (!string.IsNullOrWhiteSpace(query.Cursor) && DecodeCursor(query.Cursor!) is { } cursor)
+            materialized = ApplyCursor(materialized, query).ToList();
-                materialized = materialized.Where(x => IsAfterCursor(x, cursor, query.Descending, query.Sort)).ToList();
 
             int? total = query.IncludeTotalCount ? filteredCount : null;
             var limit = Math.Clamp(query.Limit, 1, 200);
             var page = materialized.Take(limit).Select(Clone).ToArray();
-            var next = materialized.Count > limit ? EncodeCursor(page[^1], query.Sort) : null;
+            var next = materialized.Count > limit ? CreateCursor(page[^1], query.Sort) : null;
             return Task.FromResult(new UserTaskQueryResult(page, next, total));
         }
     }
@@ -191,120 +201,76 @@ public sealed class InMemoryUserTaskRepository : IUserTaskRepository
                || task.Tags.Any(x => x.Contains(value, StringComparison.OrdinalIgnoreCase));
     }
 
-    private static IEnumerable<UserTask> Sort(IEnumerable<UserTask> items, string sort, bool descending)
+    // Same contract as EF/VNext: REST sorts only, Id always ThenBy ascending, JSON base64url cursors.
+    private static IEnumerable<UserTask> ApplyOrdering(IEnumerable<UserTask> tasks, UserTaskQuery query) => query.Sort.ToLowerInvariant() switch
     {
-        var normalized = NormalizeSort(sort);
+        "priority" => query.Descending ? tasks.OrderByDescending(x => x.Priority).ThenBy(x => x.Id) : tasks.OrderBy(x => x.Priority).ThenBy(x => x.Id),
-        return normalized switch
+        "title" => query.Descending ? tasks.OrderByDescending(x => x.Title, TitleComparer).ThenBy(x => x.Id) : tasks.OrderBy(x => x.Title, TitleComparer).ThenBy(x => x.Id),
+        "due" => query.Descending ? tasks.OrderBy(x => x.DueAt == null).ThenByDescending(x => x.DueAt).ThenBy(x => x.Id) : tasks.OrderBy(x => x.DueAt == null).ThenBy(x => x.DueAt).ThenBy(x => x.Id),
+        "updated" => query.Descending ? tasks.OrderByDescending(x => x.UpdatedAt).ThenBy(x => x.Id) : tasks.OrderBy(x => x.UpdatedAt).ThenBy(x => x.Id),
+        _ => query.Descending ? tasks.OrderByDescending(x => x.CreatedAt).ThenBy(x => x.Id) : tasks.OrderBy(x => x.CreatedAt).ThenBy(x => x.Id)
+    };
+
+    private static IEnumerable<UserTask> ApplyCursor(IEnumerable<UserTask> tasks, UserTaskQuery query)
+    {
+        if (string.IsNullOrWhiteSpace(query.Cursor) || !TryReadCursor(query.Cursor, out var value, out var id))
+            return tasks;
+        return query.Sort.ToLowerInvariant() switch
         {
-            "due" => descending
+            "priority" when int.TryParse(value, out var priority) => tasks.Where(x => query.Descending ? x.Priority < priority || x.Priority == priority && string.Compare(x.Id, id) > 0 : x.Priority > priority || x.Priority == priority && string.Compare(x.Id, id) > 0),
-                ? items.OrderByDescending(x => x.DueAt.HasValue).ThenByDescending(x => x.DueAt).ThenByDescending(x => x.Id, StringComparer.Ordinal)
+            "title" => tasks.Where(x => TitleIsAfterCursor(x.Title, value, x.Id, id, query.Descending)),
-                : items.OrderBy(x => x.DueAt.HasValue ? 0 : 1).ThenBy(x => x.DueAt).ThenBy(x => x.Id, StringComparer.Ordinal),
+            "due" when value == "~null" => tasks.Where(x => x.DueAt == null && string.Compare(x.Id, id) > 0),
-            "priority" => descending
+            "due" when DateTimeOffset.TryParse(value, out var due) => tasks.Where(x => x.DueAt == null || query.Descending && x.DueAt < due || !query.Descending && x.DueAt > due || x.DueAt == due && string.Compare(x.Id, id) > 0),
-                ? items.OrderByDescending(x => x.Priority).ThenByDescending(x => x.Id, StringComparer.Ordinal)
+            "updated" when DateTimeOffset.TryParse(value, out var updated) => tasks.Where(x => query.Descending ? x.UpdatedAt < updated || x.UpdatedAt == updated && string.Compare(x.Id, id) > 0 : x.UpdatedAt > updated || x.UpdatedAt == updated && string.Compare(x.Id, id) > 0),
-                : items.OrderBy(x => x.Priority).ThenBy(x => x.Id, StringComparer.Ordinal),
+            _ when DateTimeOffset.TryParse(value, out var created) => tasks.Where(x => query.Descending ? x.CreatedAt < created || x.CreatedAt == created && string.Compare(x.Id, id) > 0 : x.CreatedAt > created || x.CreatedAt == created && string.Compare(x.Id, id) > 0),
-            "updated" => descending
+            _ => tasks
-                ? items.OrderByDescending(x => x.UpdatedAt).ThenByDescending(x => x.Id, StringComparer.Ordinal)
-                : items.OrderBy(x => x.UpdatedAt).ThenBy(x => x.Id, StringComparer.Ordinal),
-            "completed" => descending
-                ? items.OrderByDescending(x => x.CompletedAt.HasValue).ThenByDescending(x => x.CompletedAt).ThenByDescending(x => x.Id, StringComparer.Ordinal)
-                : items.OrderBy(x => x.CompletedAt.HasValue ? 0 : 1).ThenBy(x => x.CompletedAt).ThenBy(x => x.Id, StringComparer.Ordinal),
-            "title" => descending
-                ? items.OrderByDescending(x => x.Title, StringComparer.OrdinalIgnoreCase).ThenByDescending(x => x.Id, StringComparer.Ordinal)
-                : items.OrderBy(x => x.Title, StringComparer.OrdinalIgnoreCase).ThenBy(x => x.Id, StringComparer.Ordinal),
-            _ => descending
-                ? items.OrderByDescending(x => x.CreatedAt).ThenByDescending(x => x.Id, StringComparer.Ordinal)
-                : items.OrderBy(x => x.CreatedAt).ThenBy(x => x.Id, StringComparer.Ordinal)
         };
     }
 
-    private static bool IsAfterCursor(UserTask task, (string Kind, string Value, string Id) cursor, bool descending, string sort)
+    private static bool TitleIsAfterCursor(string title, string cursorTitle, string id, string cursorId, bool descending)
     {
-        var normalized = NormalizeSort(sort);
+        var comparison = TitleComparer.Compare(title, cursorTitle);
-        // Due/completed ordering keeps null values at the end in both directions. A generic numeric
+        return descending
-        // comparison would incorrectly drop nulls after a descending non-null page (or reintroduce
+            ? comparison < 0 || comparison == 0 && string.Compare(id, cursorId) > 0
-        // non-null values after a descending null page).
+            : comparison > 0 || comparison == 0 && string.Compare(id, cursorId) > 0;
-        if (descending && (normalized is "due" or "completed"))
+    }
+
+    private static string CreateCursor(UserTask task, string sort)
+    {
+        var value = sort.ToLowerInvariant() switch
         {
-            var valueIsNull = SortValue(task, normalized) == null;
+            "priority" => task.Priority.ToString(System.Globalization.CultureInfo.InvariantCulture),
-            var cursorIsNull = cursor.Value == "~";
+            "title" => task.Title,
-            if (valueIsNull != cursorIsNull)
+            "due" => task.DueAt?.ToString("O", System.Globalization.CultureInfo.InvariantCulture) ?? "~null",
-                return valueIsNull;
+            "updated" => task.UpdatedAt.ToString("O", System.Globalization.CultureInfo.InvariantCulture),
-        }
+            _ => task.CreatedAt.ToString("O", System.Globalization.CultureInfo.InvariantCulture)
-
+        };
-        var comparison = CompareSortValue(SortKind(sort), SortValue(task, sort), cursor.Kind, cursor.Value);
+        return Convert.ToBase64String(JsonSerializer.SerializeToUtf8Bytes(new[] { value, task.Id }, JsonOptions)).TrimEnd('=').Replace('+', '-').Replace('/', '_');
-        if (comparison == 0)
-            comparison = StringComparer.Ordinal.Compare(task.Id, cursor.Id);
-        return descending ? comparison < 0 : comparison > 0;
     }
 
-    private static string EncodeCursor(UserTask task, string sort)
+    private static bool TryReadCursor(string? cursor, out string value, out string id)
-    {
-        var kind = SortKind(sort);
-        var value = EncodeSortValue(SortValue(task, sort), kind);
-        return Convert.ToBase64String(Encoding.UTF8.GetBytes(kind + "|" + value + "|" + task.Id));
-    }
-
-    private static (string Kind, string Value, string Id)? DecodeCursor(string cursor)
     {
+        value = id = "";
+        if (string.IsNullOrWhiteSpace(cursor))
+            return false;
         try
         {
-            var value = Encoding.UTF8.GetString(Convert.FromBase64String(cursor));
+            var padded = cursor.Replace('-', '+').Replace('_', '/') + new string('=', (4 - cursor.Length % 4) % 4);
-            var first = value.IndexOf('|');
+            var values = JsonSerializer.Deserialize<string[]>(Convert.FromBase64String(padded), JsonOptions);
-            var last = value.LastIndexOf('|');
+            if (values is not [var parsedValue, var parsedId] || string.IsNullOrWhiteSpace(parsedId))
-            return first <= 0 || last <= first ? null : (value[..first], value[(first + 1)..last], value[(last + 1)..]);
+                return false;
+            value = parsedValue;
+            id = parsedId;
+            return true;
         }
         catch (FormatException)
         {
-            return null;
+            return false;
+        }
+        catch (JsonException)
+        {
+            return false;
         }
-    }
-
-    private static string NormalizeSort(string sort) => sort.ToLowerInvariant() switch
-    {
-        "dueat" => "due",
-        "completedat" => "completed",
-        _ => sort.ToLowerInvariant() is "due" or "priority" or "updated" or "completed" or "title" ? sort.ToLowerInvariant() : "created"
-    };
-
-    private static string SortKind(string sort) => NormalizeSort(sort) switch
-    {
-        "priority" => "i",
-        "title" => "s",
-        "due" or "completed" => "n",
-        _ => "n"
-    };
-
-    private static object? SortValue(UserTask task, string sort) => NormalizeSort(sort) switch
-    {
-        "due" => task.DueAt,
-        "priority" => task.Priority,
-        "updated" => task.UpdatedAt,
-        "completed" => task.CompletedAt,
-        "title" => task.Title,
-        _ => task.CreatedAt
-    };
-
-    private static string EncodeSortValue(object? value, string kind) => value switch
-    {
-        null => "~",
-        DateTimeOffset date => date.UtcTicks.ToString(System.Globalization.CultureInfo.InvariantCulture),
-        int number => number.ToString(System.Globalization.CultureInfo.InvariantCulture),
-        _ => Convert.ToBase64String(Encoding.UTF8.GetBytes(value.ToString() ?? ""))
-    };
-
-    private static int CompareSortValue(string kind, object? value, string cursorKind, string cursorValue)
-    {
-        if (!string.Equals(kind, cursorKind, StringComparison.Ordinal))
-            return 0;
-        if (value == null || cursorValue == "~")
-            return value == null && cursorValue == "~" ? 0 : value == null ? 1 : -1;
-        if (kind == "i")
-            return int.Parse(value.ToString()!, System.Globalization.CultureInfo.InvariantCulture).CompareTo(int.Parse(cursorValue, System.Globalization.CultureInfo.InvariantCulture));
-        if (kind == "n")
-            return long.Parse(value switch { DateTimeOffset d => d.UtcTicks.ToString(System.Globalization.CultureInfo.InvariantCulture), _ => value.ToString()! }, System.Globalization.CultureInfo.InvariantCulture)
-                .CompareTo(long.Parse(cursorValue, System.Globalization.CultureInfo.InvariantCulture));
-        var decoded = Encoding.UTF8.GetString(Convert.FromBase64String(cursorValue));
-        return StringComparer.OrdinalIgnoreCase.Compare(value.ToString(), decoded);
     }
 
     private static string Key(string tenantId, string taskId) => tenantId + "\0" + taskId;

test/unit/Elsa.UserTasks.Persistence.ConformanceTests/UserTaskConformanceTestBase.cs

@@ -34,7 +34,8 @@ public abstract class UserTaskConformanceTestBase(UserTaskStoreFixture fixture)
         string title = "Approve request",
         int priority = 50,
         DateTimeOffset? dueAt = null,
-        DateTimeOffset? createdAt = null)
+        DateTimeOffset? createdAt = null,
+        DateTimeOffset? updatedAt = null)
     {
         var ordinal = ++_sequence;
         var created = createdAt ?? Clock.UtcNow.AddMinutes(ordinal);
@@ -56,7 +57,7 @@ public abstract class UserTaskConformanceTestBase(UserTaskStoreFixture fixture)
             CandidateUsers = candidate is null ? [] : [candidate],
             InvitationDefinitions = [new UserTaskInvitationDefinition("bearer", ["Complete"], BearerOnly: true)],
             CreatedAt = created,
-            UpdatedAt = created
+            UpdatedAt = updatedAt ?? created
         };
     }
 

test/unit/Elsa.UserTasks.Persistence.ConformanceTests/UserTaskRepositoryConformanceTests.cs

@@ -327,6 +327,8 @@ public abstract class UserTaskRepositoryConformanceTests(UserTaskStoreFixture fi
     [InlineData("priority", true)]
     [InlineData("title", false)]
     [InlineData("title", true)]
+    [InlineData("updated", false)]
+    [InlineData("updated", true)]
     public async Task CursorsAreStableAcrossEverySupportedSortAndDirection(string sort, bool descending)
     {
         await ActivateAsync();
@@ -342,6 +344,21 @@ public abstract class UserTaskRepositoryConformanceTests(UserTaskStoreFixture fi
             Assert.Equal(expected, await PageThroughAsync(query, pageSize));
     }
 
+    [ConformanceFact]
+    public async Task UpdatedSortUsesUpdatedAtThenAscendingId()
+    {
+        await ActivateAsync();
+        await SeedSortableTasksAsync();
+
+        // Seed UpdatedAt order is Bravo, Foxtrot, Charlie+Delta (shared, Id tie), Echo, Alpha —
+        // not the created/title order — so a provider that still maps updated to created fails.
+        var ascending = await Repository.QueryAsync(Query(sort: "updated", limit: 200));
+        Assert.Equal(["Bravo", "Foxtrot", "Charlie", "Delta", "Echo", "Alpha"], ascending.Items.Select(x => x.Title));
+
+        var descending = await Repository.QueryAsync(Query(sort: "updated", descending: true, limit: 200));
+        Assert.Equal(["Alpha", "Echo", "Charlie", "Delta", "Foxtrot", "Bravo"], descending.Items.Select(x => x.Title));
+    }
+
     [ConformanceFact]
     public async Task TasksWithoutADueDateOrderLastInBothDirections()
     {
@@ -392,21 +409,23 @@ public abstract class UserTaskRepositoryConformanceTests(UserTaskStoreFixture fi
 
     /// <summary>
     /// Seeds a set that exercises every sort key at once: distinct titles, distinct priorities, a mix of
-    /// present and absent due dates, and two rows sharing a due date so the identity tiebreaker is used.
+    /// present and absent due dates, updated times that are not the created order, and two rows sharing a
+    /// due date and two sharing an updated time so the identity tiebreaker is used.
     /// </summary>
     private async Task SeedSortableTasksAsync()
     {
         var subject = Subject();
         var baseline = Clock.UtcNow;
         var shared = baseline.AddDays(3);
+        var sharedUpdated = baseline.AddHours(3);
         UserTask[] tasks =
         [
-            CreateTask(subject, "Alpha", priority: 10, dueAt: baseline.AddDays(1)),
+            CreateTask(subject, "Alpha", priority: 10, dueAt: baseline.AddDays(1), updatedAt: baseline.AddHours(6)),
-            CreateTask(subject, "Bravo", priority: 90, dueAt: shared),
+            CreateTask(subject, "Bravo", priority: 90, dueAt: shared, updatedAt: baseline.AddHours(1)),
-            CreateTask(subject, "Charlie", priority: 50, dueAt: shared),
+            CreateTask(subject, "Charlie", priority: 50, dueAt: shared, updatedAt: sharedUpdated),
-            CreateTask(subject, "Delta", priority: 30, dueAt: baseline.AddDays(5)),
+            CreateTask(subject, "Delta", priority: 30, dueAt: baseline.AddDays(5), updatedAt: sharedUpdated),
-            CreateTask(subject, "Echo", priority: 70, dueAt: null),
+            CreateTask(subject, "Echo", priority: 70, dueAt: null, updatedAt: baseline.AddHours(5)),
-            CreateTask(subject, "Foxtrot", priority: 20, dueAt: null)
+            CreateTask(subject, "Foxtrot", priority: 20, dueAt: null, updatedAt: baseline.AddHours(2))
         ];
 
         foreach (var task in tasks)

test/unit/Elsa.UserTasks.UnitTests/UserTaskTests.cs

@@ -59,13 +59,15 @@ public class UserTaskTests
     [InlineData("priority", true)]
     [InlineData("title", false)]
     [InlineData("title", true)]
+    [InlineData("updated", false)]
+    [InlineData("updated", true)]
     public async Task Repository_CursorCoversSupportedSortsAndDirections(string sort, bool descending)
     {
         var repository = new InMemoryUserTaskRepository();
         var now = DateTimeOffset.UtcNow;
-        await repository.AddProjectionAsync(new() { Id = "task-a", TenantId = "tenant", Title = "Alpha", Priority = 10, DueAt = now.AddHours(1), CreatedAt = now.AddMinutes(1) });
+        await repository.AddProjectionAsync(new() { Id = "task-a", TenantId = "tenant", Title = "Alpha", Priority = 10, DueAt = now.AddHours(1), CreatedAt = now.AddMinutes(1), UpdatedAt = now.AddHours(3) });
-        await repository.AddProjectionAsync(new() { Id = "task-b", TenantId = "tenant", Title = "Beta", Priority = 50, DueAt = null, CreatedAt = now.AddMinutes(2) });
+        await repository.AddProjectionAsync(new() { Id = "task-b", TenantId = "tenant", Title = "Beta", Priority = 50, DueAt = null, CreatedAt = now.AddMinutes(2), UpdatedAt = now.AddHours(1) });
-        await repository.AddProjectionAsync(new() { Id = "task-c", TenantId = "tenant", Title = "Gamma", Priority = 90, DueAt = now.AddHours(2), CreatedAt = now.AddMinutes(3) });
+        await repository.AddProjectionAsync(new() { Id = "task-c", TenantId = "tenant", Title = "Gamma", Priority = 90, DueAt = now.AddHours(2), CreatedAt = now.AddMinutes(3), UpdatedAt = now.AddHours(2) });
 
         var first = await repository.QueryAsync(new() { TenantId = "tenant", Limit = 2, Sort = sort, Descending = descending, IncludeTotalCount = true });
         var second = await repository.QueryAsync(new() { TenantId = "tenant", Limit = 2, Sort = sort, Descending = descending, Cursor = first.NextCursor, IncludeTotalCount = true });
@@ -76,6 +78,63 @@ public class UserTaskTests
         Assert.Equal(3, ids.Distinct().Count());
     }
 
+    [Fact]
+    public async Task Repository_DescendingSortUsesAscendingIdTiebreaker()
+    {
+        var repository = new InMemoryUserTaskRepository();
+        var now = DateTimeOffset.UtcNow;
+        await repository.AddProjectionAsync(new() { Id = "task-b", TenantId = "tenant", Priority = 50, CreatedAt = now });
+        await repository.AddProjectionAsync(new() { Id = "task-a", TenantId = "tenant", Priority = 50, CreatedAt = now });
+
+        var page = await repository.QueryAsync(new() { TenantId = "tenant", Sort = "priority", Descending = true, Limit = 10 });
+
+        Assert.Equal(["task-a", "task-b"], page.Items.Select(x => x.Id));
+    }
+
+    [Fact]
+    public async Task Repository_TitleCursorUsesTheSameComparisonForTies()
+    {
+        var repository = new InMemoryUserTaskRepository();
+        await repository.AddProjectionAsync(new() { Id = "task-b", TenantId = "tenant", Title = "Same" });
+        await repository.AddProjectionAsync(new() { Id = "task-a", TenantId = "tenant", Title = "Same" });
+
+        var first = await repository.QueryAsync(new() { TenantId = "tenant", Sort = "title", Limit = 1 });
+        var second = await repository.QueryAsync(new() { TenantId = "tenant", Sort = "title", Limit = 1, Cursor = first.NextCursor });
+
+        Assert.Equal("task-a", Assert.Single(first.Items).Id);
+        Assert.Equal("task-b", Assert.Single(second.Items).Id);
+    }
+
+    [Fact]
+    public async Task Repository_TitleCursorDoesNotDropUnicodeVariantTitles()
+    {
+        var repository = new InMemoryUserTaskRepository();
+        await repository.AddProjectionAsync(new() { Id = "task-a", TenantId = "tenant", Title = "caf\u00E9" });
+        await repository.AddProjectionAsync(new() { Id = "task-b", TenantId = "tenant", Title = "cafe\u0301" });
+
+        // InMemory title sort is ordinal: NFC/NFD café are distinct keys and must both
+        // appear. Recreate the list after switching to an EF collation host.
+        var first = await repository.QueryAsync(new() { TenantId = "tenant", Sort = "title", Limit = 1 });
+        var second = await repository.QueryAsync(new() { TenantId = "tenant", Sort = "title", Limit = 1, Cursor = first.NextCursor });
+
+        Assert.Equal(2, first.Items.Concat(second.Items).Select(x => x.Id).Distinct().Count());
+        Assert.Null(second.NextCursor);
+    }
+
+    [Fact]
+    public async Task Repository_UnknownSortCompletedUsesCreatedOrder()
+    {
+        var repository = new InMemoryUserTaskRepository();
+        var now = DateTimeOffset.UtcNow;
+        await repository.AddProjectionAsync(new() { Id = "task-a", TenantId = "tenant", CreatedAt = now.AddMinutes(1), CompletedAt = now.AddHours(3) });
+        await repository.AddProjectionAsync(new() { Id = "task-b", TenantId = "tenant", CreatedAt = now.AddMinutes(2), CompletedAt = now.AddHours(1) });
+
+        var created = await repository.QueryAsync(new() { TenantId = "tenant", Sort = "created", Limit = 10 });
+        var completed = await repository.QueryAsync(new() { TenantId = "tenant", Sort = "completed", Limit = 10 });
+
+        Assert.Equal(created.Items.Select(x => x.Id), completed.Items.Select(x => x.Id));
+    }
+
     [Fact]
     public async Task Manager_HidesProtectedFieldsUntilClaimAndCompletesAfterBookmarkFinalization()
     {