feat: support co-gm group delegation

.gitea/workflows/deploy.yml

@@ -6,7 +6,7 @@ on:
       - main 
 
 env:
-  VERSION: 1.5.0
+  VERSION: 1.6.0
 
 jobs:
   # ЧАСТЬ 1: Собираем образы и кладем в Gitea (чтобы делиться с ребятами)

Directory.Build.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <Version>1.5.0</Version>
+    <Version>1.6.0</Version>
     <TargetFramework>net10.0</TargetFramework>
     <LangVersion>preview</LangVersion>
     <Nullable>enable</Nullable>

README.md

@@ -4,7 +4,7 @@
 
 Проект разработан с упором на производительность, архитектуру Vertical Slice, Native AOT (для бота) и удобство развертывания с использованием .NET Aspire.
 
-**Текущая версия:** `v1.5.0`.
+**Текущая версия:** `v1.6.0`.
 
 ---
 
@@ -15,7 +15,7 @@
 - **✋ Интерактивная запись и выход**: Игроки записываются на конкретные даты и самостоятельно снимают запись нажатием одной кнопки.
 - **👥 Лимит мест и лист ожидания**: ГМ задаёт максимальный состав, бот не переполняет сессию, автоматически ведёт очередь ожидания и освобождённое место отдаёт первому ожидающему.
 - **📁 Поддержка Форумов (Telegram Topics)**: Бот автоматически создает тему во вложенных чатах Telegram под каждую новую пачку игр.
-- **❌ Управление сессиями**: Мастер может отменять отдельные игры прямо в общем сообщении расписания.
+- **❌ Управление сессиями**: Owner и назначенные co-GM могут создавать, отменять, удалять и переносить игры прямо из Telegram.
 - **🔔 Персональные уведомления**: Игроки получают DM о RSVP за 24 часа, напоминание за 1 час, ссылку перед игрой, отмены и переносы; групповые уведомления при этом остаются.
 - **🗓 Экспорт в Календарь**: Генерация файла `.ics` для добавления всех игр в Google, Apple или Яндекс Календарь одной командой.
 - **🚀 Native AOT**: Скомпилирован в нативный бинарный файл. Мгновенный запуск и минимальное потребление памяти. Идеально для **Raspberry Pi**.
@@ -23,6 +23,7 @@
 ### 🌐 Web Dashboard (Blazor Server)
 - **🔐 Авторизация через Telegram**: Безопасный вход с использованием Telegram Login Widget (HMAC-SHA256 валидация).
 - **📝 Удобное редактирование**: Веб-интерфейс для детального редактирования сессий, изменения дат, названий и статусов.
+- **🤝 Co-GM и делегирование**: Owner группы назначает помощников по Telegram ID, а co-GM получает доступ к управлению расписанием в Telegram и Web Dashboard.
 - **🧩 Bulk-операции для Batch Sessions**: ГМ может обновить общий title/link, перенести всю пачку на фиксированный шаг и клонировать batch на следующую неделю или месяц.
 - **🔕 Режим уведомлений batch**: Для каждой пачки можно выбрать `В группе и в личку` или `Только в группе`.
 - **⬆️ Управление очередью**: Веб-интерфейс показывает заполненность, лист ожидания и позволяет ГМу поднять первого игрока из очереди.
@@ -103,7 +104,7 @@ docker compose up -d
     * `Закрепление сообщений` — рекомендуется.
 
 > [!TIP]
-> Колонку "Мастер" (GM) бот определяет по первому человеку, который создал сессию в этой группе. Только этот пользователь сможет отменять игры через кнопки бота и редактировать их в веб-интерфейсе.
+> Owner группы определяется по первому человеку, который создал сессию в этой группе. Owner может назначать co-GM в Web Dashboard; owner и co-GM могут управлять сессиями через кнопки бота и веб-интерфейс.
 
 ---
 
@@ -125,8 +126,11 @@ docker compose up -d
 
 Игрок может самостоятельно снять запись кнопкой `🚪 Выйти` в сообщении расписания. Если он был в основном составе и в листе ожидания есть игроки, бот автоматически переводит первого ожидающего в основной состав и обновляет сообщение пачки.
 
+### Делегирование управления
+На странице группы Web Dashboard показывает owner и список co-GM. Owner может добавить помощника по Telegram ID, имени и username, а также снять роль co-GM. Назначенный co-GM видит группу в панели управления и может редактировать сессии, управлять batch-операциями, очередью, переносами и удалением игр, но не может назначать других co-GM.
+
 ### Bulk-операции в Web Dashboard
-На странице группы Web Dashboard показывает отдельный блок для каждой пачки игр. ГМ может:
+На странице группы Web Dashboard показывает отдельный блок для каждой пачки игр. Owner и co-GM могут:
 - обновить общий `title` и `link` сразу у всех сессий batch;
 - выбрать режим уведомлений: дублировать важные сообщения игрокам в личку или оставить только групповые уведомления;
 - перенести пачку, задав новую первую дату и фиксированный шаг между играми в днях;

compose.yaml

@@ -17,7 +17,7 @@ services:
       retries: 10
 
   bot:
-    image: git.codeanddice.ru/toutsu/gmrelay-bot:1.5.0
+    image: git.codeanddice.ru/toutsu/gmrelay-bot:1.6.0
     restart: always
     depends_on:
       db:
@@ -29,7 +29,7 @@ services:
       - gmrelay
 
   web:
-    image: git.codeanddice.ru/toutsu/gmrelay-web:1.5.0
+    image: git.codeanddice.ru/toutsu/gmrelay-web:1.6.0
     restart: always
     depends_on:
       db:

src/GmRelay.Bot/Features/Sessions/CreateSession/CancelSessionHandler.cs

@@ -16,7 +16,7 @@ public sealed record CancelSessionCommand(
     int MessageId);
 
 // DTOs for AOT compilation
-internal sealed record CancelSessionInfoDto(string Title, Guid BatchId, long GmId, string NotificationMode);
+internal sealed record CancelSessionInfoDto(string Title, Guid BatchId, bool CanManage, string NotificationMode);
 
 public sealed class CancelSessionHandler(
     NpgsqlDataSource dataSource,
@@ -29,13 +29,23 @@ public sealed class CancelSessionHandler(
         await using var connection = await dataSource.OpenConnectionAsync(ct);
         await using var transaction = await connection.BeginTransactionAsync(ct);
         
-        // 1. Проверяем, что запрос делает ГМ данной сессии
+        // 1. Проверяем, что запрос делает управляющий данной группы.
         var session = await connection.QuerySingleOrDefaultAsync<CancelSessionInfoDto>(
-            @"SELECT s.title as Title, s.batch_id as BatchId, g.gm_telegram_id as GmId, s.notification_mode as NotificationMode
+            """
-              FROM sessions s
+            SELECT s.title AS Title,
-              JOIN game_groups g ON s.group_id = g.id
+                   s.batch_id AS BatchId,
-              WHERE s.id = @SessionId",
+                   s.notification_mode AS NotificationMode,
-            new { command.SessionId }, transaction);
+                   EXISTS (
+                       SELECT 1
+                       FROM group_managers gm
+                       JOIN players p ON p.id = gm.player_id
+                       WHERE gm.group_id = s.group_id
+                         AND p.telegram_id = @TelegramUserId
+                   ) AS CanManage
+            FROM sessions s
+            WHERE s.id = @SessionId
+            """,
+            new { command.SessionId, command.TelegramUserId }, transaction);
 
         if (session == null)
         {
@@ -43,9 +53,9 @@ public sealed class CancelSessionHandler(
             return;
         }
 
-        if (session.GmId != command.TelegramUserId)
+        if (!session.CanManage)
         {
-            await bot.AnswerCallbackQuery(command.CallbackQueryId, "Только Мастер Игры (GM) может отменять сессию.", showAlert: true, cancellationToken: ct);
+            await bot.AnswerCallbackQuery(command.CallbackQueryId, "Только owner или co-GM может отменять сессию.", showAlert: true, cancellationToken: ct);
             return;
         }
 

src/GmRelay.Bot/Features/Sessions/CreateSession/CreateSessionHandler.cs

@@ -7,6 +7,8 @@ using Telegram.Bot.Types;
 
 namespace GmRelay.Bot.Features.Sessions.CreateSession;
 
+internal sealed record SessionCreationGroupAccessDto(Guid GroupId, bool CanManage);
+
 public sealed class CreateSessionHandler(
     NpgsqlDataSource dataSource,
     ITelegramBotClient botClient,
@@ -74,16 +76,64 @@ public sealed class CreateSessionHandler(
                 new { TgId = gmId, Name = gmName, Username = gmUsername },
                 transaction);
 
-            var groupId = await connection.ExecuteScalarAsync<Guid>(
+            var existingGroup = await connection.QuerySingleOrDefaultAsync<SessionCreationGroupAccessDto>(
                 """
-                INSERT INTO game_groups (telegram_chat_id, name, gm_telegram_id)
+                SELECT g.id AS GroupId,
-                VALUES (@ChatId, @ChatName, @GmId)
+                       EXISTS (
-                ON CONFLICT (telegram_chat_id) DO UPDATE SET name = EXCLUDED.name
+                           SELECT 1
-                RETURNING id;
+                           FROM group_managers gm
+                           JOIN players p ON p.id = gm.player_id
+                           WHERE gm.group_id = g.id
+                             AND p.telegram_id = @GmId
+                       ) AS CanManage
+                FROM game_groups g
+                WHERE g.telegram_chat_id = @ChatId
                 """,
-                new { ChatId = chatId, ChatName = chatTitle, GmId = gmId },
+                new { ChatId = chatId, GmId = gmId },
                 transaction);
 
+            Guid groupId;
+            if (existingGroup is null)
+            {
+                groupId = await connection.ExecuteScalarAsync<Guid>(
+                    """
+                    INSERT INTO game_groups (telegram_chat_id, name, gm_telegram_id)
+                    VALUES (@ChatId, @ChatName, @GmId)
+                    RETURNING id;
+                    """,
+                    new { ChatId = chatId, ChatName = chatTitle, GmId = gmId },
+                    transaction);
+
+                await connection.ExecuteAsync(
+                    """
+                    INSERT INTO group_managers (group_id, player_id, role)
+                    SELECT @GroupId, p.id, @OwnerRole
+                    FROM players p
+                    WHERE p.telegram_id = @GmId
+                    ON CONFLICT (group_id, player_id) DO NOTHING
+                    """,
+                    new { GroupId = groupId, GmId = gmId, OwnerRole = GroupManagerRoleExtensions.OwnerValue },
+                    transaction);
+            }
+            else
+            {
+                if (!existingGroup.CanManage)
+                {
+                    await transaction.RollbackAsync(cancellationToken);
+                    await botClient.SendMessage(
+                        chatId,
+                        "⛔ Только owner или co-GM этой группы может создавать игровые сессии.",
+                        cancellationToken: cancellationToken);
+                    return;
+                }
+
+                groupId = existingGroup.GroupId;
+                await connection.ExecuteAsync(
+                    "UPDATE game_groups SET name = @ChatName WHERE id = @GroupId",
+                    new { ChatName = chatTitle, GroupId = groupId },
+                    transaction);
+            }
+
             int? messageThreadId = null;
             if (message.Chat.IsForum)
             {

src/GmRelay.Bot/Features/Sessions/CreateSession/PromoteWaitlistedPlayerHandler.cs

@@ -13,7 +13,7 @@ public sealed record PromoteWaitlistedPlayerCommand(
     long ChatId,
     int MessageId);
 
-internal sealed record PromoteWaitlistSessionDto(string Title, Guid BatchId, long GmId, int? MaxPlayers);
+internal sealed record PromoteWaitlistSessionDto(string Title, Guid BatchId, bool CanManage, int? MaxPlayers);
 internal sealed record WaitlistedParticipantDto(Guid ParticipantRowId, string DisplayName);
 
 public sealed class PromoteWaitlistedPlayerHandler(
@@ -34,13 +34,18 @@ public sealed class PromoteWaitlistedPlayerHandler(
                 SELECT s.title AS Title,
                        s.batch_id AS BatchId,
                        s.max_players AS MaxPlayers,
-                       g.gm_telegram_id AS GmId
+                       EXISTS (
+                           SELECT 1
+                           FROM group_managers gm
+                           JOIN players p ON p.id = gm.player_id
+                           WHERE gm.group_id = s.group_id
+                             AND p.telegram_id = @TelegramUserId
+                       ) AS CanManage
                 FROM sessions s
-                JOIN game_groups g ON s.group_id = g.id
                 WHERE s.id = @SessionId
                 FOR UPDATE
                 """,
-                new { command.SessionId },
+                new { command.SessionId, command.TelegramUserId },
                 transaction);
 
             if (session is null)
@@ -50,10 +55,10 @@ public sealed class PromoteWaitlistedPlayerHandler(
                 return;
             }
 
-            if (session.GmId != command.TelegramUserId)
+            if (!session.CanManage)
             {
                 await transaction.RollbackAsync(ct);
-                await bot.AnswerCallbackQuery(command.CallbackQueryId, "Только Мастер Игры (GM) может поднимать игроков из листа ожидания.", showAlert: true, cancellationToken: ct);
+                await bot.AnswerCallbackQuery(command.CallbackQueryId, "Только owner или co-GM может поднимать игроков из листа ожидания.", showAlert: true, cancellationToken: ct);
                 return;
             }
 

src/GmRelay.Bot/Features/Sessions/ListSessions/DeleteSessionHandler.cs

@@ -12,7 +12,7 @@ public sealed record DeleteSessionCommand(
     long ChatId,
     int MessageId);
 
-internal sealed record DeleteSessionInfoDto(string Title, Guid BatchId, long GmId, int? ThreadId);
+internal sealed record DeleteSessionInfoDto(string Title, Guid BatchId, bool CanManage, int? ThreadId);
 
 public sealed class DeleteSessionHandler(
     NpgsqlDataSource dataSource,
@@ -24,13 +24,23 @@ public sealed class DeleteSessionHandler(
         await using var connection = await dataSource.OpenConnectionAsync(ct);
         await using var transaction = await connection.BeginTransactionAsync(ct);
 
-        // 1. Fetch session and verify GM
+        // 1. Fetch session and verify group manager.
         var session = await connection.QuerySingleOrDefaultAsync<DeleteSessionInfoDto>(
-            @"SELECT s.title as Title, s.batch_id as BatchId, s.thread_id as ThreadId, g.gm_telegram_id as GmId
+            """
-              FROM sessions s
+            SELECT s.title AS Title,
-              JOIN game_groups g ON s.group_id = g.id
+                   s.batch_id AS BatchId,
-              WHERE s.id = @SessionId",
+                   s.thread_id AS ThreadId,
-            new { command.SessionId }, transaction);
+                   EXISTS (
+                       SELECT 1
+                       FROM group_managers gm
+                       JOIN players p ON p.id = gm.player_id
+                       WHERE gm.group_id = s.group_id
+                         AND p.telegram_id = @TelegramUserId
+                   ) AS CanManage
+            FROM sessions s
+            WHERE s.id = @SessionId
+            """,
+            new { command.SessionId, command.TelegramUserId }, transaction);
 
         if (session == null)
         {
@@ -38,9 +48,9 @@ public sealed class DeleteSessionHandler(
             return;
         }
 
-        if (session.GmId != command.TelegramUserId)
+        if (!session.CanManage)
         {
-            await bot.AnswerCallbackQuery(command.CallbackQueryId, "Только Мастер Игры (GM) может удалять сессию.", showAlert: true, cancellationToken: ct);
+            await bot.AnswerCallbackQuery(command.CallbackQueryId, "Только owner или co-GM может удалять сессию.", showAlert: true, cancellationToken: ct);
             return;
         }
 
@@ -77,16 +87,23 @@ public sealed class DeleteSessionHandler(
             @"SELECT s.id as Id, s.title as Title, s.scheduled_at as ScheduledAt, s.status as Status, s.max_players as MaxPlayers,
                      COUNT(sp.id) FILTER (WHERE sp.is_gm = false AND sp.registration_status = @Active) as PlayerCount,
                      COUNT(sp.id) FILTER (WHERE sp.is_gm = false AND sp.registration_status = @Waitlisted) as WaitlistCount,
-                     g.gm_telegram_id as GmId
+                     EXISTS (
+                         SELECT 1
+                         FROM group_managers gm
+                         JOIN players manager_player ON manager_player.id = gm.player_id
+                         WHERE gm.group_id = s.group_id
+                           AND manager_player.telegram_id = @TelegramUserId
+                     ) AS CanManage
               FROM sessions s
               JOIN game_groups g ON s.group_id = g.id
               LEFT JOIN session_participants sp ON s.id = sp.session_id
               WHERE g.telegram_chat_id = @ChatId AND s.status != @Cancelled AND s.scheduled_at > NOW()
-              GROUP BY s.id, s.title, s.scheduled_at, s.status, s.max_players, g.gm_telegram_id
+              GROUP BY s.id, s.title, s.scheduled_at, s.status, s.max_players, s.group_id
               ORDER BY s.scheduled_at ASC",
             new
             {
                 ChatId = command.ChatId,
+                command.TelegramUserId,
                 Cancelled = SessionStatus.Cancelled,
                 Active = ParticipantRegistrationStatus.Active,
                 Waitlisted = ParticipantRegistrationStatus.Waitlisted
@@ -110,8 +127,8 @@ public sealed class DeleteSessionHandler(
             text += $"🔹 <b>{s.ScheduledAt.FormatMoscow()}</b> — {System.Net.WebUtility.HtmlEncode(s.Title)} (Места: {seats}{waitlist})\n";
         }
 
-        var isGm = command.TelegramUserId == sessionsList.First().GmId;
+        var canManage = sessionsList.First().CanManage;
-        var keyboard = isGm 
+        var keyboard = canManage
             ? new Telegram.Bot.Types.ReplyMarkups.InlineKeyboardMarkup(
                 sessionsList.Select(s => new[] { Telegram.Bot.Types.ReplyMarkups.InlineKeyboardButton.WithCallbackData($"🗑 Удалить {s.ScheduledAt.FormatMoscowShort()}", $"delete_session:{s.Id}") }))
             : null;

src/GmRelay.Bot/Features/Sessions/ListSessions/ListSessionsHandler.cs

@@ -6,7 +6,7 @@ using Telegram.Bot.Types;
 
 namespace GmRelay.Bot.Features.Sessions.ListSessions;
 
-internal sealed record SessionListItemDto(Guid Id, string Title, DateTime ScheduledAt, string Status, int? MaxPlayers, int PlayerCount, int WaitlistCount, long GmId);
+internal sealed record SessionListItemDto(Guid Id, string Title, DateTime ScheduledAt, string Status, int? MaxPlayers, int PlayerCount, int WaitlistCount, bool CanManage);
 
 public sealed class ListSessionsHandler(
     NpgsqlDataSource dataSource,
@@ -20,16 +20,23 @@ public sealed class ListSessionsHandler(
             @"SELECT s.id as Id, s.title as Title, s.scheduled_at as ScheduledAt, s.status as Status, s.max_players as MaxPlayers,
                      COUNT(sp.id) FILTER (WHERE sp.is_gm = false AND sp.registration_status = @Active) as PlayerCount,
                      COUNT(sp.id) FILTER (WHERE sp.is_gm = false AND sp.registration_status = @Waitlisted) as WaitlistCount,
-                     g.gm_telegram_id as GmId
+                     EXISTS (
+                         SELECT 1
+                         FROM group_managers gm
+                         JOIN players manager_player ON manager_player.id = gm.player_id
+                         WHERE gm.group_id = s.group_id
+                           AND manager_player.telegram_id = @TelegramUserId
+                     ) AS CanManage
               FROM sessions s
               JOIN game_groups g ON s.group_id = g.id
               LEFT JOIN session_participants sp ON s.id = sp.session_id
               WHERE g.telegram_chat_id = @ChatId AND s.status != @Cancelled AND s.scheduled_at > NOW()
-              GROUP BY s.id, s.title, s.scheduled_at, s.status, s.max_players, g.gm_telegram_id
+              GROUP BY s.id, s.title, s.scheduled_at, s.status, s.max_players, s.group_id
               ORDER BY s.scheduled_at ASC",
             new
             {
                 ChatId = message.Chat.Id,
+                TelegramUserId = message.From?.Id,
                 Cancelled = SessionStatus.Cancelled,
                 Active = ParticipantRegistrationStatus.Active,
                 Waitlisted = ParticipantRegistrationStatus.Waitlisted
@@ -56,8 +63,8 @@ public sealed class ListSessionsHandler(
             text += $"🔹 <b>{s.ScheduledAt.FormatMoscow()}</b> — {System.Net.WebUtility.HtmlEncode(s.Title)} (Места: {seats}{waitlist})\n";
         }
 
-        var isGm = message.From?.Id == sessionsList.First().GmId;
+        var canManage = sessionsList.First().CanManage;
-        var keyboard = isGm 
+        var keyboard = canManage
             ? new Telegram.Bot.Types.ReplyMarkups.InlineKeyboardMarkup(
                 sessionsList.Select(s => new[] { Telegram.Bot.Types.ReplyMarkups.InlineKeyboardButton.WithCallbackData($"🗑 Удалить {s.ScheduledAt.FormatMoscowShort()}", $"delete_session:{s.Id}") }))
             : null;

src/GmRelay.Bot/Features/Sessions/RescheduleSession/HandleRescheduleTimeInputHandler.cs

@@ -62,6 +62,13 @@ public sealed class HandleRescheduleTimeInputHandler(
             WHERE rp.proposed_by = @GmId
               AND rp.status = 'AwaitingTime'
               AND g.telegram_chat_id = @ChatId
+              AND EXISTS (
+                  SELECT 1
+                  FROM group_managers gm
+                  JOIN players manager_player ON manager_player.id = gm.player_id
+                  WHERE gm.group_id = s.group_id
+                    AND manager_player.telegram_id = @GmId
+              )
             ORDER BY rp.created_at DESC
             LIMIT 1
             """,

src/GmRelay.Bot/Features/Sessions/RescheduleSession/InitiateRescheduleHandler.cs

@@ -16,7 +16,7 @@ public sealed record InitiateRescheduleCommand(
 
 // ── DTOs ─────────────────────────────────────────────────────────────
 
-internal sealed record RescheduleSessionInfoDto(string Title, long GmId);
+internal sealed record RescheduleSessionInfoDto(string Title, bool CanManage);
 
 // ── Handler ──────────────────────────────────────────────────────────
 
@@ -34,15 +34,21 @@ public sealed class InitiateRescheduleHandler(
     {
         await using var connection = await dataSource.OpenConnectionAsync(ct);
 
-        // 1. Verify GM ownership
+        // 1. Verify group management access.
         var session = await connection.QuerySingleOrDefaultAsync<RescheduleSessionInfoDto>(
             """
-            SELECT s.title AS Title, g.gm_telegram_id AS GmId
+            SELECT s.title AS Title,
+                   EXISTS (
+                       SELECT 1
+                       FROM group_managers gm
+                       JOIN players p ON p.id = gm.player_id
+                       WHERE gm.group_id = s.group_id
+                         AND p.telegram_id = @TelegramUserId
+                   ) AS CanManage
             FROM sessions s
-            JOIN game_groups g ON s.group_id = g.id
             WHERE s.id = @SessionId AND s.status != @Cancelled
             """,
-            new { command.SessionId, Cancelled = SessionStatus.Cancelled });
+            new { command.SessionId, command.TelegramUserId, Cancelled = SessionStatus.Cancelled });
 
         if (session is null)
         {
@@ -50,10 +56,10 @@ public sealed class InitiateRescheduleHandler(
             return;
         }
 
-        if (session.GmId != command.TelegramUserId)
+        if (!session.CanManage)
         {
             await bot.AnswerCallbackQuery(command.CallbackQueryId,
-                "Только Мастер Игры (GM) может переносить сессию.", showAlert: true, cancellationToken: ct);
+                "Только owner или co-GM может переносить сессию.", showAlert: true, cancellationToken: ct);
             return;
         }
 

src/GmRelay.Bot/Migrations/V008__add_group_managers.sql

@@ -0,0 +1,26 @@
+-- Add explicit owner/co-GM management roles for each Telegram group.
+
+INSERT INTO players (telegram_id, display_name)
+SELECT DISTINCT gg.gm_telegram_id,
+       'GM ' || gg.gm_telegram_id::text
+FROM game_groups gg
+ON CONFLICT (telegram_id) DO NOTHING;
+
+CREATE TABLE group_managers (
+    id                  UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    group_id            UUID NOT NULL REFERENCES game_groups(id) ON DELETE CASCADE,
+    player_id           UUID NOT NULL REFERENCES players(id) ON DELETE CASCADE,
+    role                VARCHAR(50) NOT NULL CHECK (role IN ('Owner', 'CoGm')),
+    added_by_player_id  UUID REFERENCES players(id) ON DELETE SET NULL,
+    created_at          TIMESTAMPTZ NOT NULL DEFAULT now(),
+    UNIQUE (group_id, player_id)
+);
+
+INSERT INTO group_managers (group_id, player_id, role)
+SELECT gg.id, p.id, 'Owner'
+FROM game_groups gg
+JOIN players p ON p.telegram_id = gg.gm_telegram_id
+ON CONFLICT (group_id, player_id) DO NOTHING;
+
+CREATE INDEX ix_group_managers_group_role ON group_managers (group_id, role);
+CREATE INDEX ix_group_managers_player ON group_managers (player_id);

src/GmRelay.Shared/Domain/GroupManagerRole.cs

@@ -0,0 +1,34 @@
+namespace GmRelay.Shared.Domain;
+
+public enum GroupManagerRole
+{
+    Owner,
+    CoGm
+}
+
+public static class GroupManagerRoleExtensions
+{
+    public const string OwnerValue = "Owner";
+    public const string CoGmValue = "CoGm";
+
+    public static string ToDatabaseValue(this GroupManagerRole role) => role switch
+    {
+        GroupManagerRole.Owner => OwnerValue,
+        GroupManagerRole.CoGm => CoGmValue,
+        _ => throw new ArgumentOutOfRangeException(nameof(role), role, "Unknown group manager role.")
+    };
+
+    public static GroupManagerRole FromDatabaseValue(string value) => value switch
+    {
+        OwnerValue => GroupManagerRole.Owner,
+        CoGmValue => GroupManagerRole.CoGm,
+        _ => throw new ArgumentOutOfRangeException(nameof(value), value, "Unknown group manager role.")
+    };
+
+    public static string ToDisplayName(this GroupManagerRole role) => role switch
+    {
+        GroupManagerRole.Owner => "Owner",
+        GroupManagerRole.CoGm => "Co-GM",
+        _ => throw new ArgumentOutOfRangeException(nameof(role), role, "Unknown group manager role.")
+    };
+}

src/GmRelay.Web/Components/Pages/GroupDetails.razor

@@ -20,6 +20,57 @@
         <h2>📅 Предстоящие игры</h2>
     </div>
 
+    @if (groupManagement is not null)
+    {
+        <div class="glass-card animate-slide-up" style="margin-bottom: 1rem;">
+            <div class="batch-bulk-header">
+                <div>
+                    <h3>Управление группой</h3>
+                    <p>@groupManagement.Group.Name · @FormatRole(CurrentUserRole)</p>
+                </div>
+                <span class="status-badge status-info">@FormatRole(CurrentUserRole)</span>
+            </div>
+
+            <div style="display: flex; gap: 0.5rem; flex-wrap: wrap; margin-bottom: 1rem;">
+                @foreach (var manager in groupManagement.Managers)
+                {
+                    <span class="status-badge @(manager.Role == GroupManagerRoleExtensions.OwnerValue ? "status-success" : "status-info")">
+                        @FormatManager(manager)
+                    </span>
+                    @if (groupManagement.CurrentUserIsOwner && manager.Role == GroupManagerRoleExtensions.CoGmValue)
+                    {
+                        <button type="button" class="btn-gm btn-gm-outline" style="font-size: 0.75rem; padding: 0.25rem 0.5rem;" disabled="@(removingCoGmId == manager.TelegramId)" @onclick="() => RemoveCoGm(manager.TelegramId)">
+                            @(removingCoGmId == manager.TelegramId ? "⏳ Удаляем..." : "Убрать")
+                        </button>
+                    }
+                }
+            </div>
+
+            @if (groupManagement.CurrentUserIsOwner)
+            {
+                <EditForm Model="@coGmModel" OnValidSubmit="AddCoGm">
+                    <div class="batch-bulk-fields">
+                        <div class="gm-form-group">
+                            <label class="gm-form-label">Telegram ID co-GM</label>
+                            <InputNumber @bind-Value="coGmModel.TelegramId" class="gm-form-control" min="1" />
+                        </div>
+                        <div class="gm-form-group">
+                            <label class="gm-form-label">Имя</label>
+                            <InputText @bind-Value="coGmModel.DisplayName" class="gm-form-control" />
+                        </div>
+                        <div class="gm-form-group">
+                            <label class="gm-form-label">Username</label>
+                            <InputText @bind-Value="coGmModel.TelegramUsername" class="gm-form-control" />
+                        </div>
+                    </div>
+                    <button type="submit" class="btn-gm btn-gm-primary" disabled="@isAddingCoGm">
+                        @(isAddingCoGm ? "⏳ Добавляем..." : "➕ Добавить co-GM")
+                    </button>
+                </EditForm>
+            }
+        </div>
+    }
+
     @if (!string.IsNullOrEmpty(errorMessage))
     {
         <div class="gm-alert gm-alert-danger" style="margin-bottom: 1rem;">
@@ -212,12 +263,16 @@
 @code {
     [Parameter] public Guid GroupId { get; set; }
     private List<WebSession>? sessions;
+    private WebGroupManagement? groupManagement;
     private List<BatchBulkEditModel> batchModels = [];
     private Guid? promotingSessionId;
     private Guid? processingBatchId;
+    private long? removingCoGmId;
+    private bool isAddingCoGm;
     private long telegramId;
     private string? errorMessage;
     private string? successMessage;
+    private CoGmEditModel coGmModel = new();
 
     protected override async Task OnInitializedAsync()
     {
@@ -233,6 +288,13 @@
 
     private async Task LoadSessions()
     {
+        groupManagement = await SessionService.GetGroupManagementForGmAsync(GroupId, telegramId);
+        if (groupManagement is null)
+        {
+            Navigation.NavigateTo("/access-denied");
+            return;
+        }
+
         sessions = await SessionService.GetUpcomingSessionsForGmAsync(GroupId, telegramId);
         if (sessions is null)
         {
@@ -243,6 +305,72 @@
         RebuildBatchModels();
     }
 
+    private async Task AddCoGm()
+    {
+        errorMessage = null;
+        successMessage = null;
+
+        if (!coGmModel.TelegramId.HasValue || coGmModel.TelegramId.Value <= 0)
+        {
+            errorMessage = "Telegram ID co-GM должен быть положительным числом.";
+            return;
+        }
+
+        isAddingCoGm = true;
+
+        try
+        {
+            await SessionService.AddCoGmForOwnerAsync(
+                GroupId,
+                telegramId,
+                coGmModel.TelegramId.Value,
+                coGmModel.DisplayName,
+                coGmModel.TelegramUsername);
+
+            coGmModel = new();
+            successMessage = "Co-GM добавлен.";
+            await LoadSessions();
+        }
+        catch (SessionAccessDeniedException)
+        {
+            Navigation.NavigateTo("/access-denied");
+        }
+        catch (Exception ex)
+        {
+            errorMessage = "Не удалось добавить co-GM: " + ex.Message;
+        }
+        finally
+        {
+            isAddingCoGm = false;
+        }
+    }
+
+    private async Task RemoveCoGm(long coGmTelegramId)
+    {
+        errorMessage = null;
+        successMessage = null;
+        removingCoGmId = coGmTelegramId;
+
+        try
+        {
+            await SessionService.RemoveCoGmForOwnerAsync(GroupId, telegramId, coGmTelegramId);
+            successMessage = "Co-GM удалён.";
+            await LoadSessions();
+        }
+        catch (SessionAccessDeniedException)
+        {
+            Navigation.NavigateTo("/access-denied");
+        }
+        catch (Exception ex)
+        {
+            errorMessage = "Не удалось удалить co-GM: " + ex.Message;
+        }
+        finally
+        {
+            removingCoGmId = null;
+        }
+    }
+
     private async Task PromoteWaitlisted(Guid sessionId)
     {
         errorMessage = null;
@@ -404,6 +532,22 @@
 
     private bool IsBatchBusy(BatchBulkEditModel batch) => processingBatchId == batch.BatchId;
 
+    private string CurrentUserRole =>
+        groupManagement?.Managers.FirstOrDefault(manager => manager.TelegramId == telegramId)?.Role
+        ?? GroupManagerRoleExtensions.CoGmValue;
+
+    private static string FormatRole(string role) =>
+        GroupManagerRoleExtensions.FromDatabaseValue(role).ToDisplayName();
+
+    private static string FormatManager(WebGroupManager manager)
+    {
+        var username = string.IsNullOrWhiteSpace(manager.TelegramUsername)
+            ? manager.TelegramId.ToString(System.Globalization.CultureInfo.InvariantCulture)
+            : "@" + manager.TelegramUsername;
+
+        return $"{FormatRole(manager.Role)} · {manager.DisplayName} · {username}";
+    }
+
     private static int InferIntervalDays(IReadOnlyList<WebSession> orderedSessions)
     {
         if (orderedSessions.Count < 2)
@@ -466,4 +610,11 @@
         public int SessionCount { get; init; }
         public string CloneInterval { get; set; } = "week";
     }
+
+    private sealed class CoGmEditModel
+    {
+        public long? TelegramId { get; set; }
+        public string DisplayName { get; set; } = "";
+        public string? TelegramUsername { get; set; }
+    }
 }

src/GmRelay.Web/Components/Pages/Home.razor

@@ -1,6 +1,7 @@
 @page "/"
 @using Microsoft.AspNetCore.Authorization
 @using Microsoft.AspNetCore.Components.Authorization
+@using GmRelay.Shared.Domain
 @using GmRelay.Web.Services
 @attribute [Authorize]
 @inject AuthorizedSessionService SessionService
@@ -43,6 +44,9 @@
                     <div class="group-card-icon">🎮</div>
                     <h3 class="group-card-title">@group.Name</h3>
                     <p class="group-card-id">ID: @group.TelegramChatId</p>
+                    <span class="status-badge @(group.ManagerRole == GroupManagerRoleExtensions.OwnerValue ? "status-success" : "status-info")" style="align-self: flex-start; margin-bottom: 1rem;">
+                        @FormatRole(group.ManagerRole)
+                    </span>
                     <a href="/group/@group.Id" class="btn-gm btn-gm-primary" style="width: 100%; justify-content: center; margin-top: auto;">
                         Посмотреть игры →
                     </a>
@@ -97,4 +101,7 @@
 
         groups = await SessionService.GetGroupsForGmAsync(telegramId);
     }
+
+    private static string FormatRole(string role) =>
+        GroupManagerRoleExtensions.FromDatabaseValue(role).ToDisplayName();
 }

src/GmRelay.Web/Services/AuthorizedSessionService.cs

@@ -7,6 +7,24 @@ public sealed class AuthorizedSessionService(ISessionStore sessionStore)
     public Task<List<WebGameGroup>> GetGroupsForGmAsync(long gmId) =>
         sessionStore.GetGroupsForGmAsync(gmId);
 
+    public async Task<WebGroupManagement?> GetGroupManagementForGmAsync(Guid groupId, long gmId)
+    {
+        if (!await GroupBelongsToGmAsync(groupId, gmId))
+        {
+            return null;
+        }
+
+        var group = await sessionStore.GetGroupAsync(groupId);
+        if (group is null)
+        {
+            return null;
+        }
+
+        var managers = await sessionStore.GetGroupManagersAsync(groupId);
+        var isOwner = await sessionStore.IsGroupOwnerAsync(groupId, gmId);
+        return new WebGroupManagement(group, managers, isOwner);
+    }
+
     public async Task<List<WebSession>?> GetUpcomingSessionsForGmAsync(Guid groupId, long gmId)
     {
         if (!await GroupBelongsToGmAsync(groupId, gmId))
@@ -110,9 +128,45 @@ public sealed class AuthorizedSessionService(ISessionStore sessionStore)
         return await sessionStore.CloneBatchAsync(batchId, batch.GroupId, interval);
     }
 
+    public async Task AddCoGmForOwnerAsync(Guid groupId, long ownerTelegramId, long coGmTelegramId, string displayName, string? telegramUsername)
+    {
+        if (coGmTelegramId <= 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(coGmTelegramId), coGmTelegramId, "Telegram id must be greater than zero.");
+        }
+
+        if (ownerTelegramId == coGmTelegramId)
+        {
+            throw new InvalidOperationException("Owner is already a group manager.");
+        }
+
+        if (!await sessionStore.IsGroupOwnerAsync(groupId, ownerTelegramId))
+        {
+            throw new SessionAccessDeniedException(groupId, ownerTelegramId);
+        }
+
+        var normalizedName = string.IsNullOrWhiteSpace(displayName)
+            ? $"Telegram {coGmTelegramId.ToString(System.Globalization.CultureInfo.InvariantCulture)}"
+            : displayName.Trim();
+        var normalizedUsername = string.IsNullOrWhiteSpace(telegramUsername)
+            ? null
+            : telegramUsername.Trim().TrimStart('@');
+
+        await sessionStore.AddGroupCoGmAsync(groupId, ownerTelegramId, coGmTelegramId, normalizedName, normalizedUsername);
+    }
+
+    public async Task RemoveCoGmForOwnerAsync(Guid groupId, long ownerTelegramId, long coGmTelegramId)
+    {
+        if (!await sessionStore.IsGroupOwnerAsync(groupId, ownerTelegramId))
+        {
+            throw new SessionAccessDeniedException(groupId, ownerTelegramId);
+        }
+
+        await sessionStore.RemoveGroupCoGmAsync(groupId, coGmTelegramId);
+    }
+
     private async Task<bool> GroupBelongsToGmAsync(Guid groupId, long gmId)
     {
-        var group = await sessionStore.GetGroupAsync(groupId);
+        return await sessionStore.IsGroupManagerAsync(groupId, gmId);
-        return group?.GmTelegramId == gmId;
     }
 }

src/GmRelay.Web/Services/ISessionStore.cs

@@ -6,6 +6,9 @@ public interface ISessionStore
 {
     Task<List<WebGameGroup>> GetGroupsForGmAsync(long gmId);
     Task<WebGameGroup?> GetGroupAsync(Guid groupId);
+    Task<bool> IsGroupManagerAsync(Guid groupId, long telegramId);
+    Task<bool> IsGroupOwnerAsync(Guid groupId, long telegramId);
+    Task<List<WebGroupManager>> GetGroupManagersAsync(Guid groupId);
     Task<List<WebSession>> GetUpcomingSessionsAsync(Guid groupId);
     Task<WebSession?> GetSessionAsync(Guid sessionId);
     Task<WebSessionBatch?> GetBatchAsync(Guid batchId);
@@ -15,4 +18,6 @@ public interface ISessionStore
     Task UpdateBatchNotificationModeAsync(Guid batchId, Guid groupId, SessionNotificationMode notificationMode);
     Task RescheduleBatchAsync(Guid batchId, Guid groupId, DateTime firstScheduledAt, int intervalDays);
     Task<WebSessionBatch> CloneBatchAsync(Guid batchId, Guid groupId, BatchCloneInterval interval);
+    Task AddGroupCoGmAsync(Guid groupId, long ownerTelegramId, long coGmTelegramId, string displayName, string? telegramUsername);
+    Task RemoveGroupCoGmAsync(Guid groupId, long coGmTelegramId);
 }

src/GmRelay.Web/Services/SessionService.cs

@@ -6,7 +6,24 @@ using Telegram.Bot;
 
 namespace GmRelay.Web.Services;
 
-public sealed record WebGameGroup(Guid Id, long TelegramChatId, string Name, long GmTelegramId);
+public sealed record WebGameGroup(
+    Guid Id,
+    long TelegramChatId,
+    string Name,
+    long GmTelegramId,
+    string ManagerRole = GroupManagerRoleExtensions.OwnerValue);
+
+public sealed record WebGroupManager(
+    long TelegramId,
+    string DisplayName,
+    string? TelegramUsername,
+    string Role,
+    DateTime AddedAt);
+
+public sealed record WebGroupManagement(
+    WebGameGroup Group,
+    IReadOnlyList<WebGroupManager> Managers,
+    bool CurrentUserIsOwner);
 public sealed record WebSession(
     Guid Id,
     Guid GroupId,
@@ -56,7 +73,18 @@ public sealed class SessionService(
     {
         await using var conn = await dataSource.OpenConnectionAsync();
         return (await conn.QueryAsync<WebGameGroup>(
-            "SELECT id, telegram_chat_id AS TelegramChatId, name, gm_telegram_id AS GmTelegramId FROM game_groups WHERE gm_telegram_id = @GmId",
+            """
+            SELECT g.id,
+                   g.telegram_chat_id AS TelegramChatId,
+                   g.name,
+                   g.gm_telegram_id AS GmTelegramId,
+                   gm.role AS ManagerRole
+            FROM group_managers gm
+            JOIN players p ON p.id = gm.player_id
+            JOIN game_groups g ON g.id = gm.group_id
+            WHERE p.telegram_id = @GmId
+            ORDER BY g.name
+            """,
             new { GmId = gmId })).ToList();
     }
 
@@ -64,8 +92,145 @@ public sealed class SessionService(
     {
         await using var conn = await dataSource.OpenConnectionAsync();
         return await conn.QuerySingleOrDefaultAsync<WebGameGroup>(
-            "SELECT id, telegram_chat_id AS TelegramChatId, name, gm_telegram_id AS GmTelegramId FROM game_groups WHERE id = @GroupId",
+            """
-            new { GroupId = groupId });
+            SELECT g.id,
+                   g.telegram_chat_id AS TelegramChatId,
+                   g.name,
+                   g.gm_telegram_id AS GmTelegramId,
+                   @OwnerRole AS ManagerRole
+            FROM game_groups g
+            WHERE g.id = @GroupId
+            """,
+            new { GroupId = groupId, OwnerRole = GroupManagerRoleExtensions.OwnerValue });
+    }
+
+    public async Task<bool> IsGroupManagerAsync(Guid groupId, long telegramId)
+    {
+        await using var conn = await dataSource.OpenConnectionAsync();
+        return await conn.ExecuteScalarAsync<bool>(
+            """
+            SELECT EXISTS (
+                SELECT 1
+                FROM group_managers gm
+                JOIN players p ON p.id = gm.player_id
+                WHERE gm.group_id = @GroupId
+                  AND p.telegram_id = @TelegramId
+            )
+            """,
+            new { GroupId = groupId, TelegramId = telegramId });
+    }
+
+    public async Task<bool> IsGroupOwnerAsync(Guid groupId, long telegramId)
+    {
+        await using var conn = await dataSource.OpenConnectionAsync();
+        return await conn.ExecuteScalarAsync<bool>(
+            """
+            SELECT EXISTS (
+                SELECT 1
+                FROM group_managers gm
+                JOIN players p ON p.id = gm.player_id
+                WHERE gm.group_id = @GroupId
+                  AND p.telegram_id = @TelegramId
+                  AND gm.role = @OwnerRole
+            )
+            """,
+            new { GroupId = groupId, TelegramId = telegramId, OwnerRole = GroupManagerRoleExtensions.OwnerValue });
+    }
+
+    public async Task<List<WebGroupManager>> GetGroupManagersAsync(Guid groupId)
+    {
+        await using var conn = await dataSource.OpenConnectionAsync();
+        return (await conn.QueryAsync<WebGroupManager>(
+            """
+            SELECT p.telegram_id AS TelegramId,
+                   p.display_name AS DisplayName,
+                   p.telegram_username AS TelegramUsername,
+                   gm.role AS Role,
+                   gm.created_at AS AddedAt
+            FROM group_managers gm
+            JOIN players p ON p.id = gm.player_id
+            WHERE gm.group_id = @GroupId
+            ORDER BY CASE gm.role WHEN @OwnerRole THEN 0 ELSE 1 END,
+                     gm.created_at,
+                     p.display_name
+            """,
+            new { GroupId = groupId, OwnerRole = GroupManagerRoleExtensions.OwnerValue })).ToList();
+    }
+
+    public async Task AddGroupCoGmAsync(
+        Guid groupId,
+        long ownerTelegramId,
+        long coGmTelegramId,
+        string displayName,
+        string? telegramUsername)
+    {
+        await using var conn = await dataSource.OpenConnectionAsync();
+        await using var transaction = await conn.BeginTransactionAsync();
+
+        await conn.ExecuteAsync(
+            """
+            INSERT INTO players (telegram_id, display_name, telegram_username)
+            VALUES (@TelegramId, @DisplayName, @TelegramUsername)
+            ON CONFLICT (telegram_id) DO UPDATE
+            SET display_name = EXCLUDED.display_name,
+                telegram_username = EXCLUDED.telegram_username
+            """,
+            new
+            {
+                TelegramId = coGmTelegramId,
+                DisplayName = displayName,
+                TelegramUsername = telegramUsername
+            },
+            transaction);
+
+        await conn.ExecuteAsync(
+            """
+            INSERT INTO group_managers (group_id, player_id, role, added_by_player_id)
+            SELECT @GroupId,
+                   co_gm.id,
+                   @CoGmRole,
+                   owner_player.id
+            FROM players co_gm
+            LEFT JOIN players owner_player ON owner_player.telegram_id = @OwnerTelegramId
+            WHERE co_gm.telegram_id = @CoGmTelegramId
+            ON CONFLICT (group_id, player_id) DO UPDATE
+            SET role = CASE
+                    WHEN group_managers.role = @OwnerRole THEN group_managers.role
+                    ELSE EXCLUDED.role
+                END,
+                added_by_player_id = EXCLUDED.added_by_player_id
+            """,
+            new
+            {
+                GroupId = groupId,
+                OwnerTelegramId = ownerTelegramId,
+                CoGmTelegramId = coGmTelegramId,
+                OwnerRole = GroupManagerRoleExtensions.OwnerValue,
+                CoGmRole = GroupManagerRoleExtensions.CoGmValue
+            },
+            transaction);
+
+        await transaction.CommitAsync();
+    }
+
+    public async Task RemoveGroupCoGmAsync(Guid groupId, long coGmTelegramId)
+    {
+        await using var conn = await dataSource.OpenConnectionAsync();
+        await conn.ExecuteAsync(
+            """
+            DELETE FROM group_managers gm
+            USING players p
+            WHERE gm.player_id = p.id
+              AND gm.group_id = @GroupId
+              AND p.telegram_id = @CoGmTelegramId
+              AND gm.role = @CoGmRole
+            """,
+            new
+            {
+                GroupId = groupId,
+                CoGmTelegramId = coGmTelegramId,
+                CoGmRole = GroupManagerRoleExtensions.CoGmValue
+            });
     }
 
     public async Task<List<WebSession>> GetUpcomingSessionsAsync(Guid groupId)

src/GmRelay.Web/wwwroot/app.css

@@ -1,5 +1,5 @@
 /* ============================================
-   GM-Relay Design System v1.5.0
+   GM-Relay Design System v1.6.0
    Dark RPG Dashboard Theme
    ============================================ */
 

tests/GmRelay.Bot.Tests/Web/AuthorizedSessionServiceTests.cs

@@ -28,6 +28,34 @@ public sealed class AuthorizedSessionServiceTests
         Assert.Equal("Session A", sessions[0].Title);
     }
 
+    [Fact]
+    public async Task GetUpcomingSessionsForGmAsync_ReturnsSessions_WhenUserIsCoGm()
+    {
+        var ownerId = 1001L;
+        var coGmId = 2002L;
+        var groupId = Guid.NewGuid();
+        var store = new FakeSessionStore(
+            groups:
+            [
+                new(groupId, 42, "Alpha", ownerId)
+            ],
+            sessions:
+            [
+                new(Guid.NewGuid(), groupId, "Session A", DateTime.UtcNow, "Planned", "https://example.test/a", Guid.NewGuid(), 10, 42, 4, 1, 0)
+            ],
+            managers:
+            [
+                new(groupId, coGmId, GroupManagerRole.CoGm)
+            ]);
+        var service = new AuthorizedSessionService(store);
+
+        var sessions = await service.GetUpcomingSessionsForGmAsync(groupId, coGmId);
+
+        Assert.NotNull(sessions);
+        Assert.Single(sessions);
+        Assert.Equal("Session A", sessions[0].Title);
+    }
+
     [Fact]
     public async Task GetUpcomingSessionsForGmAsync_ReturnsNull_WhenGroupBelongsToAnotherGm()
     {
@@ -211,6 +239,105 @@ public sealed class AuthorizedSessionServiceTests
         Assert.Equal("https://example.test/b", store.LastUpdatedBatchJoinLink);
     }
 
+    [Fact]
+    public async Task UpdateBatchDetailsForGmAsync_UpdatesBatch_WhenUserIsCoGm()
+    {
+        var ownerId = 1001L;
+        var coGmId = 2002L;
+        var groupId = Guid.NewGuid();
+        var batchId = Guid.NewGuid();
+        var store = new FakeSessionStore(
+            groups:
+            [
+                new(groupId, 42, "Alpha", ownerId)
+            ],
+            sessions:
+            [
+                new(Guid.NewGuid(), groupId, "Session A", DateTime.UtcNow, "Planned", "https://example.test/a", batchId, 10, 42, 4, 1, 0)
+            ],
+            managers:
+            [
+                new(groupId, coGmId, GroupManagerRole.CoGm)
+            ]);
+        var service = new AuthorizedSessionService(store);
+
+        await service.UpdateBatchDetailsForGmAsync(batchId, coGmId, "Updated", "https://example.test/b");
+
+        Assert.True(store.UpdateBatchDetailsCalled);
+        Assert.Equal(batchId, store.LastUpdatedBatchId);
+        Assert.Equal(groupId, store.LastUpdatedBatchGroupId);
+    }
+
+    [Fact]
+    public async Task AddCoGmForOwnerAsync_AddsCoGm_WhenUserIsOwner()
+    {
+        var ownerId = 1001L;
+        var coGmId = 2002L;
+        var groupId = Guid.NewGuid();
+        var store = new FakeSessionStore(
+            groups:
+            [
+                new(groupId, 42, "Alpha", ownerId)
+            ]);
+        var service = new AuthorizedSessionService(store);
+
+        await service.AddCoGmForOwnerAsync(groupId, ownerId, coGmId, "Assistant GM", "assistant");
+
+        Assert.True(store.AddCoGmCalled);
+        Assert.Equal(groupId, store.LastAddedCoGmGroupId);
+        Assert.Equal(coGmId, store.LastAddedCoGmTelegramId);
+        Assert.Equal("Assistant GM", store.LastAddedCoGmDisplayName);
+        Assert.Equal("assistant", store.LastAddedCoGmUsername);
+    }
+
+    [Fact]
+    public async Task AddCoGmForOwnerAsync_Throws_WhenUserIsCoGm()
+    {
+        var ownerId = 1001L;
+        var coGmId = 2002L;
+        var newCoGmId = 3003L;
+        var groupId = Guid.NewGuid();
+        var store = new FakeSessionStore(
+            groups:
+            [
+                new(groupId, 42, "Alpha", ownerId)
+            ],
+            managers:
+            [
+                new(groupId, coGmId, GroupManagerRole.CoGm)
+            ]);
+        var service = new AuthorizedSessionService(store);
+
+        var action = () => service.AddCoGmForOwnerAsync(groupId, coGmId, newCoGmId, "Second Assistant", null);
+
+        await Assert.ThrowsAsync<SessionAccessDeniedException>(action);
+        Assert.False(store.AddCoGmCalled);
+    }
+
+    [Fact]
+    public async Task RemoveCoGmForOwnerAsync_RemovesCoGm_WhenUserIsOwner()
+    {
+        var ownerId = 1001L;
+        var coGmId = 2002L;
+        var groupId = Guid.NewGuid();
+        var store = new FakeSessionStore(
+            groups:
+            [
+                new(groupId, 42, "Alpha", ownerId)
+            ],
+            managers:
+            [
+                new(groupId, coGmId, GroupManagerRole.CoGm)
+            ]);
+        var service = new AuthorizedSessionService(store);
+
+        await service.RemoveCoGmForOwnerAsync(groupId, ownerId, coGmId);
+
+        Assert.True(store.RemoveCoGmCalled);
+        Assert.Equal(groupId, store.LastRemovedCoGmGroupId);
+        Assert.Equal(coGmId, store.LastRemovedCoGmTelegramId);
+    }
+
     [Fact]
     public async Task UpdateBatchNotificationModeForGmAsync_Throws_WhenBatchBelongsToAnotherGm()
     {
@@ -335,10 +462,12 @@ public sealed class AuthorizedSessionServiceTests
 
     private sealed class FakeSessionStore(
         IEnumerable<WebGameGroup>? groups = null,
-        IEnumerable<WebSession>? sessions = null) : ISessionStore
+        IEnumerable<WebSession>? sessions = null,
+        IEnumerable<FakeGroupManager>? managers = null) : ISessionStore
     {
         private readonly Dictionary<Guid, WebGameGroup> groupsById = groups?.ToDictionary(group => group.Id) ?? [];
         private readonly Dictionary<Guid, WebSession> sessionsById = sessions?.ToDictionary(session => session.Id) ?? [];
+        private readonly List<FakeGroupManager> managers = managers?.ToList() ?? [];
 
         public bool UpdateCalled { get; private set; }
         public bool PromoteCalled { get; private set; }
@@ -346,6 +475,8 @@ public sealed class AuthorizedSessionServiceTests
         public bool UpdateBatchNotificationModeCalled { get; private set; }
         public bool RescheduleBatchCalled { get; private set; }
         public bool CloneBatchCalled { get; private set; }
+        public bool AddCoGmCalled { get; private set; }
+        public bool RemoveCoGmCalled { get; private set; }
         public Guid? LastUpdatedSessionId { get; private set; }
         public Guid? LastUpdatedGroupId { get; private set; }
         public string? LastUpdatedTitle { get; private set; }
@@ -368,9 +499,15 @@ public sealed class AuthorizedSessionServiceTests
         public Guid? LastClonedBatchId { get; private set; }
         public Guid? LastClonedBatchGroupId { get; private set; }
         public BatchCloneInterval? LastCloneInterval { get; private set; }
+        public Guid? LastAddedCoGmGroupId { get; private set; }
+        public long? LastAddedCoGmTelegramId { get; private set; }
+        public string? LastAddedCoGmDisplayName { get; private set; }
+        public string? LastAddedCoGmUsername { get; private set; }
+        public Guid? LastRemovedCoGmGroupId { get; private set; }
+        public long? LastRemovedCoGmTelegramId { get; private set; }
 
         public Task<List<WebGameGroup>> GetGroupsForGmAsync(long gmId) =>
-            Task.FromResult(groupsById.Values.Where(group => group.GmTelegramId == gmId).ToList());
+            Task.FromResult(groupsById.Values.Where(group => IsManager(group.Id, gmId)).ToList());
 
         public Task<WebGameGroup?> GetGroupAsync(Guid groupId)
         {
@@ -378,6 +515,36 @@ public sealed class AuthorizedSessionServiceTests
             return Task.FromResult(group);
         }
 
+        public Task<bool> IsGroupManagerAsync(Guid groupId, long telegramId) =>
+            Task.FromResult(IsManager(groupId, telegramId));
+
+        public Task<bool> IsGroupOwnerAsync(Guid groupId, long telegramId) =>
+            Task.FromResult(IsOwner(groupId, telegramId));
+
+        public Task<List<WebGroupManager>> GetGroupManagersAsync(Guid groupId)
+        {
+            if (!groupsById.TryGetValue(groupId, out var group))
+            {
+                return Task.FromResult(new List<WebGroupManager>());
+            }
+
+            var result = new List<WebGroupManager>
+            {
+                new(group.GmTelegramId, "Owner GM", null, GroupManagerRoleExtensions.OwnerValue, DateTime.UtcNow)
+            };
+
+            result.AddRange(managers
+                .Where(manager => manager.GroupId == groupId)
+                .Select(manager => new WebGroupManager(
+                    manager.TelegramId,
+                    $"Co-GM {manager.TelegramId}",
+                    null,
+                    manager.Role.ToDatabaseValue(),
+                    DateTime.UtcNow)));
+
+            return Task.FromResult(result);
+        }
+
         public Task<List<WebSession>> GetUpcomingSessionsAsync(Guid groupId) =>
             Task.FromResult(sessionsById.Values.Where(session => session.GroupId == groupId).ToList());
 
@@ -474,5 +641,32 @@ public sealed class AuthorizedSessionServiceTests
                 DateTime.UtcNow.AddDays(7),
                 1));
         }
+
+        public Task AddGroupCoGmAsync(Guid groupId, long ownerTelegramId, long coGmTelegramId, string displayName, string? telegramUsername)
+        {
+            AddCoGmCalled = true;
+            LastAddedCoGmGroupId = groupId;
+            LastAddedCoGmTelegramId = coGmTelegramId;
+            LastAddedCoGmDisplayName = displayName;
+            LastAddedCoGmUsername = telegramUsername;
+            return Task.CompletedTask;
+        }
+
+        public Task RemoveGroupCoGmAsync(Guid groupId, long coGmTelegramId)
+        {
+            RemoveCoGmCalled = true;
+            LastRemovedCoGmGroupId = groupId;
+            LastRemovedCoGmTelegramId = coGmTelegramId;
+            return Task.CompletedTask;
+        }
+
+        private bool IsManager(Guid groupId, long telegramId) =>
+            IsOwner(groupId, telegramId) ||
+            managers.Any(manager => manager.GroupId == groupId && manager.TelegramId == telegramId);
+
+        private bool IsOwner(Guid groupId, long telegramId) =>
+            groupsById.TryGetValue(groupId, out var group) && group.GmTelegramId == telegramId;
     }
+
+    private sealed record FakeGroupManager(Guid GroupId, long TelegramId, GroupManagerRole Role);
 }