Give packs an identity so create can refuse missing deps and load in a stable order.

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

docs/design/foundation.md

@@ -9,12 +9,11 @@
 
 ## Почему сейчас
 
-**Моды существуют на бумаге.** В `mods/` лежит один `core`. Last-wins, патчи и порядок загрузки
-проверяются синтетическими документами в памяти, а путь «игрок выбрал мод» не проверяется вообще —
-подставить нечего. Пак не имеет удостоверения: `GET /api/mods` отдаёт `{id, required}`, и в диалоге
-создания игрок видит имя папки. Зависимостей между паками нет, поэтому мебельный набор, который
-патчит чужой def, может быть выбран без того, кого он патчит, — и школа не соберётся с невнятной
-ошибкой каталога.
+**Моды существуют на бумаге — остался проверяемый путь.** Удостоверение пака уже есть:
+`pack.jsonc` (версия и `requires`), название в локалях по id, `GET /api/mods?lang=` отдаёт
+подпись, создание отказывает во внятном коде, если зависимости нет или они замкнуты в цикл.
+Порядок загрузки сервер выстраивает сам и кладёт в сейв. В `mods/` по-прежнему лежит один
+`core`: last-wins, патчи и дорога «игрок выбрал мод» ждут настоящую папку — это фаза 23.
 
 **Числа поведения живут в коде вопреки [`ai.md`](ai.md).** Там записано: «Числа поведения —
 отдельный деф правил, как `StaffingDef` у штата». В `BehaviorDef` уехали порог нужды, скорость
@@ -100,9 +99,9 @@
 нанимает второго, ничего не меняется, и понять почему неоткуда. В строку непокрытого предмета
 добавляется, сколько человек его не вытягивают.
 
-**Def без подписи.** Загрузчик молча подставляет `defName`, когда ключа локали нет. Для `core` это
-ловит тест на полноту, для мода — ничего. Загрузчик начинает писать предупреждение в лог: мод-автор
-видит дыру сразу, а не по кривой подписи в дереве.
+**Def без подписи.** Загрузчик пишет предупреждение в лог, когда у конкретного неабстрактного def
+нет ключа ни в `ru`, ни в `en`. Для `core` это ловит тест на полноту; для мода автор видит дыру
+сразу, а не по кривой подписи в дереве. Каталог при этом собирается — подставляется `defName`.
 
 ## Сид школы — свой, а не производный
 

docs/phases/22-mod-identity.md

@@ -11,31 +11,31 @@
 
 ## Задачи
 
-- [ ] `pack.jsonc` в папке пака: `version` строкой, `requires` списком id. Файла нет — пак
+- [x] `pack.jsonc` в папке пака: `version` строкой, `requires` списком id. Файла нет — пак
       по-прежнему валиден: id вместо названия, версия пустая, зависимостей нет
-- [ ] Название пака — ключ по его id в его же `localizations/<lang>.jsonc`; второго способа
+- [x] Название пака — ключ по его id в его же `localizations/<lang>.jsonc`; второго способа
       называть вещи не заводить
-- [ ] `GET /api/mods` принимает `?lang=ru|en` и отдаёт `label`, `version` и `requires` рядом с
+- [x] `GET /api/mods` принимает `?lang=ru|en` и отдаёт `label`, `version` и `requires` рядом с
       `id` и `required`
-- [ ] У `core` такой же `pack.jsonc` и такое же название в локалях
-- [ ] Создание школы проверяет, что каждая зависимость выбрана; нет — `400` с кодом и id того,
+- [x] У `core` такой же `pack.jsonc` и такое же название в локалях
+- [x] Создание школы проверяет, что каждая зависимость выбрана; нет — `400` с кодом и id того,
       кого не хватает
-- [ ] Порядок загрузки выстраивает сервер: устойчивая топологическая сортировка поверх порядка
+- [x] Порядок загрузки выстраивает сервер: устойчивая топологическая сортировка поверх порядка
       игрока, `core` всегда первый. Цикл зависимостей — отказ
-- [ ] Разрешённый порядок виден: пишется в лог при старте школы и возвращается в ответе создания
-- [ ] Сейв хранит **разрешённый** порядок паков, чтобы школа поднималась тем же каталогом
-- [ ] Загрузчик пишет предупреждение, когда у конкретного def нет подписи в локали пака
-- [ ] `docs/protocol.md` и [`../design/foundation.md`](../design/foundation.md) правятся тем же
+- [x] Разрешённый порядок виден: пишется в лог при старте школы и возвращается в ответе создания
+- [x] Сейв хранит **разрешённый** порядок паков, чтобы школа поднималась тем же каталогом
+- [x] Загрузчик пишет предупреждение, когда у конкретного def нет подписи в локали пака
+- [x] `docs/protocol.md` и [`../design/foundation.md`](../design/foundation.md) правятся тем же
       коммитом, что и обработчики
 
 ## Тесты, без которых фаза не закрыта
 
-- [ ] Пак без `pack.jsonc` виден в списке, id стоит вместо названия
-- [ ] Название приходит на языке запроса, у `core` тоже
-- [ ] Пак с невыбранной зависимостью не создаёт школу; в ответе видно, кого не хватает
-- [ ] Зависимость, выбранная после зависимого, всё равно грузится раньше
-- [ ] Цикл зависимостей — отказ, а не зависание
-- [ ] Def без подписи даёт предупреждение, но не роняет каталог
+- [x] Пак без `pack.jsonc` виден в списке, id стоит вместо названия
+- [x] Название приходит на языке запроса, у `core` тоже
+- [x] Пак с невыбранной зависимостью не создаёт школу; в ответе видно, кого не хватает
+- [x] Зависимость, выбранная после зависимого, всё равно грузится раньше
+- [x] Цикл зависимостей — отказ, а не зависание
+- [x] Def без подписи даёт предупреждение, но не роняет каталог
 
 ## Критерий готовности
 

docs/protocol.md

@@ -40,7 +40,7 @@ from Monday (five is Mon–Fri; six adds Saturday). It is a school rule, not a c
   "gameMinutesPerRealSecond": 5,
   "schoolWeekDays": 5,
   "schools": [
-    { "id": 1, "name": "Гимназия №14", "gameTime": "2012-03-31T07:35:00Z", "running": false, "speedIndex": 1 }
+    { "id": 1, "name": "Гимназия №14", "gameTime": "2012-03-31T07:35:00Z", "running": false, "speedIndex": 1, "modIds": ["core"] }
   ]
 }
 ```
@@ -53,20 +53,27 @@ Optional `?lang=en` draws from the English word list (`Northern Academy`); any o
 none, stays Russian. The client sends the active UI language. Names the player types are not
 translated — they are saved as written.
 
-### `GET /api/mods`
+### `GET /api/mods?lang=ru|en`
 
 Folders under the server's `mods/` directory. `core` is always first and `required: true`; other
-packs can be switched off in the create dialog.
+packs can be switched off in the create dialog. `lang` is the same value Hello carries — not
+`Accept-Language`. Anything other than `en` is Russian.
+
+Each pack carries a human label, a version string and the ids it `requires`. The label is the pack
+id looked up in that pack's own `localizations/<lang>.jsonc`. A folder without `pack.jsonc` is
+still a pack: the id stands in for the name, `version` is empty, `requires` is empty.
 
 ```json
-{ "mods": [{ "id": "core", "required": true }] }
+{ "mods": [{ "id": "core", "required": true, "label": "Базовая игра", "version": "1.0", "requires": [] }] }
 ```
 
 ### `GET /api/catalog?lang=ru|en&mods=addon1,addon2`
 
 Placeable (non-abstract) types plus labels in `lang`, and the last-wins `maps/default.jsonc` for
-`core` plus the listed extras. The server always prepends `core`. `mods` is a comma-separated
-list of extra pack ids; omit it for vanilla. Unknown extras return `400` `unknown-mod`.
+`core` plus the listed extras. The server always prepends `core` and then reorders extras so
+`requires` load first, same as create. `mods` is a comma-separated list of extra pack ids; omit
+it for vanilla. Unknown extras return `400` `unknown-mod`. A selected pack whose dependency was
+not listed returns `400` `missing-mod`; a cycle returns `400` `mod-cycle`.
 
 Room defs that are homerooms carry `homeroom`, `seatThing` and `defaultSeats` instead of a
 slot table. A map classroom stores `seats` — how many of that thing occupy the room. Capacity is
@@ -114,8 +121,10 @@ Body:
 }
 ```
 
-`modIds` are extras; the server always prepends `core`. Omit `map` (or send `null`) to use that
-pack set's default layout. A supplied map is validated as a connected yard-and-rooms graph.
+`modIds` are extras; the server always prepends `core`, then **reorders** the selection so each
+pack's `requires` load first (stable topological sort over the player's order). The resolved
+order is returned as `modIds` on the created school and written to the save, so a restart loads
+the same catalog. Omit `map` (or send `null`) to use that pack set's default layout. A supplied map is validated as a connected yard-and-rooms graph.
 `nameSetId` is a `NameSetDef`; omit it to use the first placeable set in the catalog (vanilla:
 `Slavic`). Unknown ids return `400` `unknown-name-set`.
 `nativeLanguage` is a skill from that set's `nativeLanguages`. Omit it (or send `null`) to pick
@@ -128,6 +137,8 @@ one from the school seed. An id that is not in the set returns `400` `unknown-na
 | `400` `invalid-start-date` | Outside 1900–2999. |
 | `400` `invalid-map` | Missing yard, no rooms, unknown def, or a disconnected graph. |
 | `400` `unknown-mod` | An extra pack id is missing under `mods/`. |
+| `400` `missing-mod` | A selected pack `requires` an id that was not selected. `missing` is that id. |
+| `400` `mod-cycle` | Selected packs require each other in a cycle. |
 | `400` `invalid-catalog` | The selected packs could not be loaded. |
 | `400` `unknown-name-set` | `nameSetId` is not a placeable `NameSetDef` in those packs. |
 | `400` `unknown-native-language` | `nativeLanguage` is not in that name set's `nativeLanguages`. |

src/HSchool.Client/src/i18n/strings.ts

@@ -40,6 +40,8 @@ const ru = {
   errorInvalidStartDate: 'Дата начала вне допустимого диапазона.',
   errorInvalidMap: 'Карта должна быть связным графом: двор и хотя бы одна комната.',
   errorUnknownMod: 'Выбранный мод не найден.',
+  errorMissingMod: 'Не выбран обязательный мод «{id}».',
+  errorModCycle: 'Выбранные моды зависят друг от друга по кругу.',
   errorInvalidCatalog: 'Не удалось загрузить выбранные моды.',
   errorUnknownNameSet: 'Выбранный набор имён не найден.',
   errorUnknownNativeLanguage: 'Выбранный родной язык не входит в этот набор имён.',
@@ -251,6 +253,8 @@ const en: Messages = {
   errorInvalidStartDate: 'The start date is outside the allowed range.',
   errorInvalidMap: 'The map must be a connected graph: a yard and at least one room.',
   errorUnknownMod: 'A selected mod is missing.',
+  errorMissingMod: 'Required mod “{id}” is not selected.',
+  errorModCycle: 'The selected mods depend on each other in a cycle.',
   errorInvalidCatalog: 'The selected packs could not be loaded.',
   errorUnknownNameSet: 'The selected name set is not in the catalog.',
   errorUnknownNativeLanguage: 'The selected native language is not in that name set.',

src/HSchool.Client/src/net/api.ts

@@ -10,6 +10,7 @@ export interface School {
   readonly gameTime: string;
   readonly running: boolean;
   readonly speedIndex: number;
+  readonly modIds?: readonly string[];
 }
 
 export interface SchoolsResponse {
@@ -30,6 +31,7 @@ export class ApiError extends Error {
     readonly payroll?: number,
     readonly remaining?: number,
     readonly attempted?: number,
+    readonly missing?: string,
   ) {
     super(message);
   }
@@ -75,6 +77,9 @@ export async function createSchool(
 export interface ModInfo {
   readonly id: string;
   readonly required: boolean;
+  readonly label: string;
+  readonly version: string;
+  readonly requires: readonly string[];
 }
 
 export interface DefInfo {
@@ -167,8 +172,9 @@ export interface CatalogResponse {
   readonly holidays: readonly HolidayInfo[];
 }
 
-export async function fetchMods(): Promise<readonly ModInfo[]> {
-  const response = await request<{ mods: readonly ModInfo[] }>('/api/mods');
+export async function fetchMods(lang: string): Promise<readonly ModInfo[]> {
+  const query = new URLSearchParams({ lang });
+  const response = await request<{ mods: readonly ModInfo[] }>(`/api/mods?${query.toString()}`);
   return response.mods;
 }
 
@@ -528,6 +534,7 @@ async function toApiError(response: Response): Promise<ApiError> {
       payroll?: number;
       remaining?: number;
       attempted?: number;
+      missing?: string;
     };
     return new ApiError(
       response.status,
@@ -537,6 +544,7 @@ async function toApiError(response: Response): Promise<ApiError> {
       problem.payroll,
       problem.remaining,
       problem.attempted,
+      problem.missing,
     );
   } catch {
     return new ApiError(response.status, 'unknown', response.statusText);

src/HSchool.Client/src/ui/createSchoolDialog.ts

@@ -194,7 +194,7 @@ export function createSchoolDialog(options: CreateSchoolOptions): Promise<School
   const paintMods = async (): Promise<void> => {
     let packs;
     try {
-      packs = await fetchMods();
+      packs = await fetchMods(getLocale());
     } catch {
       showError(t('catalogLoadFailed'));
       return;
@@ -223,7 +223,7 @@ export function createSchoolDialog(options: CreateSchoolOptions): Promise<School
         'label',
         { class: 'mod-list__item' },
         checkbox,
-        pack.required ? t('coreModLocked', { id: pack.id }) : pack.id,
+        pack.required ? t('coreModLocked', { id: pack.label }) : pack.label,
       );
       modsList.append(label);
     }
@@ -359,6 +359,10 @@ function describe(reason: unknown): string {
       return t('errorInvalidMap');
     case 'unknown-mod':
       return t('errorUnknownMod');
+    case 'missing-mod':
+      return t('errorMissingMod', { id: reason.missing ?? '' });
+    case 'mod-cycle':
+      return t('errorModCycle');
     case 'invalid-catalog':
       return t('errorInvalidCatalog');
     case 'unknown-name-set':

src/HSchool.Content/CatalogLoader.cs

@@ -35,6 +35,7 @@ public sealed class CatalogLoader
         ApplyPatches(resolved, patches);
         var catalog = Materialize(order, resolved, localesRu, localesEn);
         ResolveReferences(catalog);
+        WarnMissingLabels(catalog, log);
         return catalog;
     }
 
@@ -491,5 +492,40 @@ public sealed class CatalogLoader
         PeopleDefValidator.Validate(catalog);
     }
 
+    private static void WarnMissingLabels(DefCatalog catalog, IContentLog log)
+    {
+        foreach (var def in ConcreteDefs(catalog))
+        {
+            if (!catalog.HasText("ru", def.DefName) && !catalog.HasText("en", def.DefName))
+            {
+                log.Warning($"Def {DefCatalog.KindOf(def)}:{def.DefName} has no label in the pack locales.");
+            }
+        }
+    }
+
+    private static IEnumerable<Def> ConcreteDefs(DefCatalog catalog)
+    {
+        return Enumerate(catalog.Actions.Values)
+            .Concat(Enumerate(catalog.Things.Values))
+            .Concat(Enumerate(catalog.Positions.Values))
+            .Concat(Enumerate(catalog.Works.Values))
+            .Concat(Enumerate(catalog.Rooms.Values))
+            .Concat(Enumerate(catalog.Buildings.Values))
+            .Concat(Enumerate(catalog.Floors.Values))
+            .Concat(Enumerate(catalog.Territories.Values))
+            .Concat(Enumerate(catalog.Skills.Values))
+            .Concat(Enumerate(catalog.Traits.Values))
+            .Concat(Enumerate(catalog.BodyAttributes.Values))
+            .Concat(Enumerate(catalog.Needs.Values))
+            .Concat(Enumerate(catalog.NameSets.Values))
+            .Concat(Enumerate(catalog.Subjects.Values))
+            .Concat(Enumerate(catalog.Staffing.Values))
+            .Concat(Enumerate(catalog.DayFrames.Values))
+            .Concat(Enumerate(catalog.Holidays.Values))
+            .Concat(Enumerate(catalog.Behavior.Values));
+
+        static IEnumerable<Def> Enumerate(IEnumerable<Def> defs) => defs.Where(def => !def.Abstract);
+    }
+
     private sealed record RawDef(string PackId, DefKind Kind, string DefName, JsonObject Json, string Source);
 }

src/HSchool.Content/PackDependencyException.cs

@@ -0,0 +1,32 @@
+namespace HSchool.Content;
+
+/// <summary>
+/// Selected packs cannot be ordered: a required pack is missing, or they require each other.
+/// Distinct from <see cref="ContentLoadException"/> so the create dialog can name the pack.
+/// </summary>
+public sealed class PackDependencyException : Exception
+{
+    public const string MissingCode = "missing-mod";
+
+    public const string CycleCode = "mod-cycle";
+
+    private PackDependencyException(string message, string code, string? missingPackId)
+        : base(message)
+    {
+        Code = code;
+        MissingPackId = missingPackId;
+    }
+
+    public string Code { get; }
+
+    public string? MissingPackId { get; }
+
+    public static PackDependencyException Missing(string missingPackId, string requiredBy) =>
+        new(
+            $"Pack '{requiredBy}' requires '{missingPackId}', which was not selected.",
+            MissingCode,
+            missingPackId);
+
+    public static PackDependencyException Cycle() =>
+        new("Selected packs have a cyclic dependency.", CycleCode, missingPackId: null);
+}

src/HSchool.Content/PackLoadOrder.cs

@@ -0,0 +1,93 @@
+namespace HSchool.Content;
+
+/// <summary>
+/// Stable topological sort of selected packs. Player order is kept wherever it does not
+/// contradict <c>requires</c>. <c>core</c> is expected to already be first in
+/// <paramref name="selected"/>.
+/// </summary>
+public static class PackLoadOrder
+{
+    public static IReadOnlyList<string> Resolve(
+        IReadOnlyList<string> selected,
+        IReadOnlyDictionary<string, PackManifest> manifests)
+    {
+        var index = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+        for (var i = 0; i < selected.Count; i++)
+        {
+            index[selected[i]] = i;
+        }
+
+        var indegree = new Dictionary<string, int>(StringComparer.OrdinalIgnoreCase);
+        var outgoing = new Dictionary<string, List<string>>(StringComparer.OrdinalIgnoreCase);
+        foreach (var packId in selected)
+        {
+            indegree[packId] = 0;
+            outgoing[packId] = [];
+        }
+
+        foreach (var packId in selected)
+        {
+            var requires = manifests.TryGetValue(packId, out var manifest)
+                ? manifest.Requires
+                : PackManifest.Empty.Requires;
+
+            foreach (var dependency in requires)
+            {
+                if (!indegree.ContainsKey(dependency))
+                {
+                    throw PackDependencyException.Missing(dependency, packId);
+                }
+
+                outgoing[dependency].Add(packId);
+                indegree[packId]++;
+            }
+        }
+
+        var ready = new SortedSet<int>();
+        for (var i = 0; i < selected.Count; i++)
+        {
+            if (indegree[selected[i]] == 0)
+            {
+                ready.Add(i);
+            }
+        }
+
+        var ordered = new List<string>(selected.Count);
+        while (ready.Count > 0)
+        {
+            var next = ready.Min;
+            ready.Remove(next);
+            var packId = selected[next];
+            ordered.Add(packId);
+
+            foreach (var dependent in outgoing[packId].OrderBy(id => index[id]))
+            {
+                indegree[dependent]--;
+                if (indegree[dependent] == 0)
+                {
+                    ready.Add(index[dependent]);
+                }
+            }
+        }
+
+        if (ordered.Count != selected.Count)
+        {
+            throw PackDependencyException.Cycle();
+        }
+
+        return ordered;
+    }
+
+    public static IReadOnlyDictionary<string, PackManifest> ManifestsFrom(
+        IReadOnlyList<string> packIds,
+        IReadOnlyList<ContentDocument> documents)
+    {
+        var manifests = new Dictionary<string, PackManifest>(StringComparer.OrdinalIgnoreCase);
+        foreach (var packId in packIds)
+        {
+            manifests[packId] = PackManifest.FromDocuments(packId, documents);
+        }
+
+        return manifests;
+    }
+}

src/HSchool.Content/PackManifest.cs

@@ -0,0 +1,126 @@
+using System.Text.Json.Nodes;
+
+namespace HSchool.Content;
+
+/// <summary>
+/// Identity of one pack from <c>pack.jsonc</c>. A folder without that file is still a pack:
+/// empty version, no dependencies, id used as the label until a locale supplies one.
+/// </summary>
+public sealed record PackManifest(string Version, IReadOnlyList<string> Requires)
+{
+    public static PackManifest Empty { get; } = new(string.Empty, []);
+
+    public static PackManifest Parse(string packId, string text)
+    {
+        var source = $"{packId}:pack.jsonc";
+        var node = Jsonc.Parse(text, source);
+        if (node is not JsonObject obj)
+        {
+            throw new ContentLoadException($"{source} must be an object.");
+        }
+
+        var version = ReadVersion(obj, source);
+        var requires = ReadRequires(obj, source);
+        return new PackManifest(version, requires);
+    }
+
+    public static PackManifest FromDocuments(string packId, IReadOnlyList<ContentDocument> documents)
+    {
+        foreach (var document in documents)
+        {
+            if (document.PackId == packId && PackPaths.IsManifest(document.RelativePath))
+            {
+                return Parse(packId, document.Text);
+            }
+        }
+
+        return Empty;
+    }
+
+    /// <summary>
+    /// Pack title from that pack's own locale table, keyed by pack id. Missing key → the id.
+    /// </summary>
+    public static string Label(string packId, string locale, IReadOnlyList<ContentDocument> documents)
+    {
+        foreach (var document in documents)
+        {
+            if (document.PackId != packId
+                || !PackPaths.TryGetLocaleLanguage(document.RelativePath, out var language)
+                || !language.Equals(locale, StringComparison.OrdinalIgnoreCase))
+            {
+                continue;
+            }
+
+            var table = ReadLocaleTable(document.Text, $"{packId}:{document.RelativePath}");
+            return table.TryGetValue(packId, out var label) ? label : packId;
+        }
+
+        return packId;
+    }
+
+    public static IReadOnlyDictionary<string, string> ReadLocaleTable(string text, string source)
+    {
+        var node = Jsonc.Parse(text, source);
+        if (node is not JsonObject obj)
+        {
+            throw new ContentLoadException($"Localization in {source} must be an object of strings.");
+        }
+
+        var table = new Dictionary<string, string>(StringComparer.Ordinal);
+        foreach (var property in obj)
+        {
+            if (property.Value is not JsonValue value || !value.TryGetValue<string>(out var label))
+            {
+                throw new ContentLoadException($"Localization key '{property.Key}' in {source} is not a string.");
+            }
+
+            table[property.Key] = label;
+        }
+
+        return table;
+    }
+
+    private static string ReadVersion(JsonObject obj, string source)
+    {
+        if (obj["version"] is null)
+        {
+            return string.Empty;
+        }
+
+        if (obj["version"] is JsonValue value && value.TryGetValue<string>(out var version))
+        {
+            return version ?? string.Empty;
+        }
+
+        throw new ContentLoadException($"{source} version must be a string.");
+    }
+
+    private static IReadOnlyList<string> ReadRequires(JsonObject obj, string source)
+    {
+        if (obj["requires"] is null)
+        {
+            return [];
+        }
+
+        if (obj["requires"] is not JsonArray array)
+        {
+            throw new ContentLoadException($"{source} requires must be an array of pack ids.");
+        }
+
+        var requires = new List<string>();
+        foreach (var item in array)
+        {
+            if (item is not JsonValue value || !value.TryGetValue<string>(out var packId) || string.IsNullOrWhiteSpace(packId))
+            {
+                throw new ContentLoadException($"{source} requires entries must be non-empty strings.");
+            }
+
+            if (!requires.Contains(packId, StringComparer.OrdinalIgnoreCase))
+            {
+                requires.Add(packId);
+            }
+        }
+
+        return requires;
+    }
+}

src/HSchool.Content/PackPaths.cs

@@ -58,6 +58,13 @@ internal static class PackPaths
         Normalize(relativePath).Equals("maps/default.jsonc", StringComparison.OrdinalIgnoreCase)
         || Normalize(relativePath).Equals("maps/default.json", StringComparison.OrdinalIgnoreCase);
 
+    public static bool IsManifest(string relativePath)
+    {
+        var path = Normalize(relativePath);
+        return path.Equals("pack.jsonc", StringComparison.OrdinalIgnoreCase)
+            || path.Equals("pack.json", StringComparison.OrdinalIgnoreCase);
+    }
+
     private static bool TryMapFolder(string folder, out DefKind kind)
     {
         switch (folder.ToLowerInvariant())

src/HSchool.Server/Api/ModEndpoints.cs

@@ -11,8 +11,16 @@ internal static class ModEndpoints
 {
     public static void MapModEndpoints(this IEndpointRouteBuilder builder)
     {
-        builder.MapGet("/api/mods", (ModContent mods) =>
-            new ModsResponse(mods.ListPacks().Select(pack => new ModInfoResponse(pack.Id, pack.Required)).ToArray()))
+        builder.MapGet("/api/mods", (string? lang, ModContent mods) =>
+            {
+                var locale = string.Equals(lang, "en", StringComparison.OrdinalIgnoreCase) ? "en" : "ru";
+                return new ModsResponse(mods.ListPacks(locale).Select(pack => new ModInfoResponse(
+                    pack.Id,
+                    pack.Required,
+                    pack.Label,
+                    pack.Version,
+                    pack.Requires)).ToArray());
+            })
             .WithName("GetMods");
 
         builder.MapGet("/api/catalog", (string? lang, string? mods, ModContent content) =>
@@ -31,7 +39,19 @@ internal static class ModEndpoints
                 return Problem(StatusCodes.Status400BadRequest, "invalid-catalog", "The core pack is missing.");
             }
 
-            var packIds = content.NormalizePackIds(extras);
+            IReadOnlyList<string> packIds;
+            try
+            {
+                packIds = content.ResolveSelectedPacks(extras);
+            }
+            catch (PackDependencyException ex)
+            {
+                return PackProblem(ex);
+            }
+            catch (ContentLoadException ex)
+            {
+                return Problem(StatusCodes.Status400BadRequest, "invalid-catalog", ex.Message);
+            }
             DefCatalog catalog;
             MapLayout map;
             try
@@ -69,6 +89,17 @@ internal static class ModEndpoints
         return mods.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);
     }
 
+    private static IResult PackProblem(PackDependencyException ex) =>
+        Results.Problem(
+            detail: ex.Message,
+            statusCode: StatusCodes.Status400BadRequest,
+            title: ex.Code,
+            extensions: new Dictionary<string, object?>
+            {
+                ["code"] = ex.Code,
+                ["missing"] = ex.MissingPackId,
+            });
+
     private static IResult Problem(int statusCode, string code, string detail) =>
         Results.Problem(detail: detail, statusCode: statusCode, title: code, extensions: new Dictionary<string, object?>
         {
@@ -78,7 +109,12 @@ internal static class ModEndpoints
 
 internal sealed record ModsResponse(IReadOnlyList<ModInfoResponse> Mods);
 
-internal sealed record ModInfoResponse(string Id, bool Required);
+internal sealed record ModInfoResponse(
+    string Id,
+    bool Required,
+    string Label,
+    string Version,
+    IReadOnlyList<string> Requires);
 
 internal sealed record CatalogResponse(
     IReadOnlyList<DefInfoResponse> Territories,

src/HSchool.Server/Api/SchoolEndpoints.cs

@@ -80,6 +80,14 @@ internal static class SchoolEndpoints
                     Problem(StatusCodes.Status400BadRequest, "unknown-name-set", "The selected name set is not in the catalog."),
                 SchoolCreationError.UnknownNativeLanguage =>
                     Problem(StatusCodes.Status400BadRequest, "unknown-native-language", "The selected native language is not in that name set."),
+                SchoolCreationError.MissingMod =>
+                    Problem(
+                        StatusCodes.Status400BadRequest,
+                        "missing-mod",
+                        $"Mod '{outcome.MissingPackId}' is required but was not selected.",
+                        missing: outcome.MissingPackId),
+                SchoolCreationError.ModCycle =>
+                    Problem(StatusCodes.Status400BadRequest, "mod-cycle", "Selected mods have a cyclic dependency."),
                 _ => Results.Problem("Unknown error."),
             };
         })
@@ -468,7 +476,12 @@ internal static class SchoolEndpoints
         return true;
     }
 
-    private static IResult Problem(int statusCode, string code, string detail, StaffingOutcome? staffing = null)
+    private static IResult Problem(
+        int statusCode,
+        string code,
+        string detail,
+        StaffingOutcome? staffing = null,
+        string? missing = null)
     {
         var extensions = new Dictionary<string, object?> { ["code"] = code };
         if (staffing is not null)
@@ -479,6 +492,11 @@ internal static class SchoolEndpoints
             extensions["attempted"] = staffing.Attempted;
         }
 
+        if (missing is not null)
+        {
+            extensions["missing"] = missing;
+        }
+
         return Results.Problem(detail: detail, statusCode: statusCode, title: code, extensions: extensions);
     }
 }
@@ -492,10 +510,16 @@ internal sealed record CreateSchoolRequest(
     string? NameSetId,
     string? NativeLanguage);
 
-internal sealed record SchoolResponse(int Id, string Name, DateTime GameTime, bool Running, byte SpeedIndex)
+internal sealed record SchoolResponse(
+    int Id,
+    string Name,
+    DateTime GameTime,
+    bool Running,
+    byte SpeedIndex,
+    IReadOnlyList<string> ModIds)
 {
     public static SchoolResponse From(SchoolState school) =>
-        new(school.Id, school.Name, school.GameTime, school.Running, school.SpeedIndex);
+        new(school.Id, school.Name, school.GameTime, school.Running, school.SpeedIndex, school.ModIds);
 }
 
 /// <summary>Everything the main menu needs in one request.</summary>

src/HSchool.Server/Game/GameLoopService.cs

@@ -303,7 +303,30 @@ internal sealed class GameLoopService(
                 }
             }
 
-            var packIds = mods.NormalizePackIds(extras);
+            IReadOnlyList<string> packIds;
+            try
+            {
+                packIds = mods.ResolveSelectedPacks(extras);
+            }
+            catch (PackDependencyException ex) when (ex.Code == PackDependencyException.MissingCode)
+            {
+                command.Result.TrySetResult(new SchoolCreationOutcome(
+                    null,
+                    SchoolCreationError.MissingMod,
+                    ex.MissingPackId));
+                return;
+            }
+            catch (PackDependencyException)
+            {
+                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.ModCycle));
+                return;
+            }
+            catch (ContentLoadException)
+            {
+                command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidCatalog));
+                return;
+            }
+
             if (!mods.PackExists(CatalogLoader.CorePackId))
             {
                 command.Result.TrySetResult(new SchoolCreationOutcome(null, SchoolCreationError.InvalidCatalog));

src/HSchool.Server/Game/ModContent.cs

@@ -51,9 +51,9 @@ internal sealed class ModContent
         return true;
     }
 
-    public IReadOnlyList<ModPackInfo> ListPacks()
+    public IReadOnlyList<ModPackInfo> ListPacks(string locale)
     {
-        var packs = new List<ModPackInfo> { new(CatalogLoader.CorePackId, Required: true) };
+        var packs = new List<ModPackInfo> { Describe(CatalogLoader.CorePackId, required: true, locale) };
         if (!Directory.Exists(Root))
         {
             return packs;
@@ -67,7 +67,7 @@ internal sealed class ModContent
                 continue;
             }
 
-            packs.Add(new ModPackInfo(id, Required: false));
+            packs.Add(Describe(id, required: false, locale));
         }
 
         return packs;
@@ -76,6 +76,30 @@ internal sealed class ModContent
     public IReadOnlyList<string> NormalizePackIds(IReadOnlyList<string>? extraModIds) =>
         CatalogLoader.NormalizePackOrder(extraModIds ?? []);
 
+    /// <summary>
+    /// Player extras plus <c>core</c>, reordered so each pack's <c>requires</c> load first.
+    /// Missing dependencies and cycles throw <see cref="PackDependencyException"/>.
+    /// </summary>
+    public IReadOnlyList<string> ResolveSelectedPacks(IReadOnlyList<string>? extraModIds)
+    {
+        var selected = NormalizePackIds(extraModIds);
+        var manifests = new Dictionary<string, PackManifest>(StringComparer.OrdinalIgnoreCase);
+        foreach (var packId in selected)
+        {
+            manifests[packId] = ReadManifest(packId);
+        }
+
+        return PackLoadOrder.Resolve(selected, manifests);
+    }
+
+    public PackManifest ReadManifest(string packId)
+    {
+        var jsonc = Path.Combine(PackPath(packId), "pack.jsonc");
+        var json = Path.Combine(PackPath(packId), "pack.json");
+        var path = File.Exists(jsonc) ? jsonc : File.Exists(json) ? json : null;
+        return path is null ? PackManifest.Empty : PackManifest.Parse(packId, File.ReadAllText(path));
+    }
+
     public IReadOnlyList<ContentDocument> ReadDocuments(IReadOnlyList<string> packIds)
     {
         var documents = new List<ContentDocument>();
@@ -136,7 +160,50 @@ internal sealed class ModContent
 
     public DefCatalog LoadCatalog(IReadOnlyList<string> packIds) => LoadCatalog(packIds, _logger);
 
+    private ModPackInfo Describe(string packId, bool required, string locale)
+    {
+        PackManifest manifest;
+        try
+        {
+            manifest = PackExists(packId) ? ReadManifest(packId) : PackManifest.Empty;
+        }
+        catch (ContentLoadException ex)
+        {
+            _logger.LogWarning(ex, "Could not read pack.jsonc for {PackId}.", packId);
+            manifest = PackManifest.Empty;
+        }
+
+        return new ModPackInfo(packId, required, ReadPackLabel(packId, locale), manifest.Version, manifest.Requires);
+    }
+
+    private string ReadPackLabel(string packId, string locale)
+    {
+        var jsonc = Path.Combine(PackPath(packId), "localizations", $"{locale}.jsonc");
+        var json = Path.Combine(PackPath(packId), "localizations", $"{locale}.json");
+        var path = File.Exists(jsonc) ? jsonc : File.Exists(json) ? json : null;
+        if (path is null)
+        {
+            return packId;
+        }
+
+        try
+        {
+            var table = PackManifest.ReadLocaleTable(File.ReadAllText(path), $"{packId}:localizations/{locale}");
+            return table.TryGetValue(packId, out var label) ? label : packId;
+        }
+        catch (ContentLoadException ex)
+        {
+            _logger.LogWarning(ex, "Could not read pack label for {PackId}.", packId);
+            return packId;
+        }
+    }
+
     private string PackPath(string packId) => Path.Combine(Root, packId);
 }
 
-internal sealed record ModPackInfo(string Id, bool Required);
+internal sealed record ModPackInfo(
+    string Id,
+    bool Required,
+    string Label,
+    string Version,
+    IReadOnlyList<string> Requires);

src/HSchool.Server/Game/SchoolCreationOutcome.cs

@@ -3,7 +3,10 @@ using HSchool.Simulation;
 namespace HSchool.Server.Game;
 
 /// <summary>What the supervisor reports back after trying to create a school.</summary>
-internal readonly record struct SchoolCreationOutcome(SchoolState? School, SchoolCreationError Error)
+internal readonly record struct SchoolCreationOutcome(
+    SchoolState? School,
+    SchoolCreationError Error,
+    string? MissingPackId = null)
 {
     public bool Succeeded => Error == SchoolCreationError.None && School is not null;
 }

src/HSchool.Server/Game/SchoolState.cs

@@ -4,7 +4,13 @@ namespace HSchool.Server.Game;
 /// Immutable copy of a school, safe to hand to request threads. The live <c>School</c> object
 /// never leaves its worker thread.
 /// </summary>
-internal sealed record SchoolState(int Id, string Name, DateTime GameTime, bool Running, byte SpeedIndex);
+internal sealed record SchoolState(
+    int Id,
+    string Name,
+    DateTime GameTime,
+    bool Running,
+    byte SpeedIndex,
+    IReadOnlyList<string> ModIds);
 
 /// <summary>Everything the main menu needs in one read.</summary>
 internal sealed record SchoolsState(int MaxSchools, IReadOnlyList<SchoolState> Schools);

src/HSchool.Server/Game/SchoolWorker.cs

@@ -94,7 +94,7 @@ internal sealed class SchoolWorker
         _mods = mods;
         _onFailed = onFailed;
         _logger = logger;
-        _snapshot = new SchoolState(id, name, time, running, (byte)speedIndex);
+        _snapshot = new SchoolState(id, name, time, running, (byte)speedIndex, modIds ?? []);
     }
 
     public int Id => _id;
@@ -203,6 +203,7 @@ internal sealed class SchoolWorker
     private void RunLoop(CancellationToken cancellationToken)
     {
         var packIds = _mods.NormalizePackIds(_modIds);
+        _logger.LogInformation("School {SchoolId} loading packs [{Packs}].", _id, string.Join(", ", packIds));
         foreach (var packId in packIds)
         {
             if (!_mods.PackExists(packId))
@@ -577,7 +578,8 @@ internal sealed class SchoolWorker
                 school.Name,
                 school.Clock.Time,
                 school.Clock.IsRunning,
-                (byte)school.Clock.SpeedIndex));
+                (byte)school.Clock.SpeedIndex,
+                school.Catalog?.PackIds ?? _modIds ?? []));
         Volatile.Write(ref _rosterSnapshot, school.Roster);
         Volatile.Write(ref _applicantSnapshot, school.Applicants);
         Volatile.Write(ref _timetableSnapshot, school.Timetable);

src/HSchool.Server/Program.cs

@@ -73,6 +73,9 @@ if (app.Configuration.GetValue("HSchool:AllowSaveReload", false))
 
     app.MapGet("/api/dev/saves-directory", (SchoolStore store) => Results.Json(new { path = store.DirectoryPath }))
         .WithName("GetSavesDirectory");
+
+    app.MapGet("/api/dev/mods-directory", (ModContent mods) => Results.Json(new { path = mods.Root }))
+        .WithName("GetModsDirectory");
 }
 
 // The realtime channel: one binary frame per protocol message, see docs/protocol.md.

src/HSchool.Server/mods/core/localizations/en.jsonc

@@ -116,4 +116,5 @@
   "WinterBreak": "Winter break",
   "SpringBreak": "Spring break",
   "SummerBreak": "Summer break",
+  "core": "Core",
 }

src/HSchool.Server/mods/core/localizations/ru.jsonc

@@ -116,4 +116,5 @@
   "WinterBreak": "Зимние каникулы",
   "SpringBreak": "Весенние каникулы",
   "SummerBreak": "Летние каникулы",
+  "core": "Базовая игра",
 }

src/HSchool.Server/mods/core/pack.jsonc

@@ -0,0 +1,4 @@
+{
+  "version": "1.0",
+  "requires": [],
+}

src/HSchool.Simulation/SchoolCreationError.cs

@@ -15,4 +15,6 @@ public enum SchoolCreationError
     InvalidCatalog,
     UnknownNameSet,
     UnknownNativeLanguage,
+    MissingMod,
+    ModCycle,
 }

tests/HSchool.AppHost.Tests/SchoolApiTests.cs

@@ -143,6 +143,126 @@ public class SchoolApiTests(AppHostFixture fixture)
         Assert.NotNull(response);
         var core = Assert.Single(response.Mods, pack => pack.Id == "core");
         Assert.True(core.Required);
+        Assert.Equal("Базовая игра", core.Label);
+        Assert.False(string.IsNullOrWhiteSpace(core.Version));
+        Assert.Empty(core.Requires);
+    }
+
+    [Fact]
+    public async Task Mods_LabelsCoreInTheRequestedLanguage()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+
+        var ru = await client.GetFromJsonAsync<ModsResponse>("/api/mods?lang=ru", TestContext.Current.CancellationToken);
+        var en = await client.GetFromJsonAsync<ModsResponse>("/api/mods?lang=en", TestContext.Current.CancellationToken);
+
+        Assert.NotNull(ru);
+        Assert.NotNull(en);
+        Assert.Equal("Базовая игра", Assert.Single(ru.Mods, pack => pack.Id == "core").Label);
+        Assert.Equal("Core", Assert.Single(en.Mods, pack => pack.Id == "core").Label);
+    }
+
+    [Fact]
+    public async Task Mods_PackWithoutManifest_UsesIdAsLabel()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        var root = await ModsDirectoryAsync(client);
+        using (new TempPack(root, "t22plain"))
+        {
+            var response = await client.GetFromJsonAsync<ModsResponse>("/api/mods?lang=en", TestContext.Current.CancellationToken);
+
+            Assert.NotNull(response);
+            var pack = Assert.Single(response.Mods, candidate => candidate.Id == "t22plain");
+            Assert.False(pack.Required);
+            Assert.Equal("t22plain", pack.Label);
+            Assert.Equal(string.Empty, pack.Version);
+            Assert.Empty(pack.Requires);
+        }
+    }
+
+    [Fact]
+    public async Task CreateSchool_ReturnsResolvedPackOrder()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        await ResetAsync(client);
+
+        var created = await CreateAsync(client, "С ванилью", ExpectedDefaultStart);
+
+        Assert.Equal(["core"], created.ModIds);
+    }
+
+    [Fact]
+    public async Task CreateSchool_WithUnselectedDependency_NamesTheMissingPack()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        await ResetAsync(client);
+        var root = await ModsDirectoryAsync(client);
+        using (new TempPack(root, "t22need", """{ "version": "1", "requires": ["t22ghost"] }"""))
+        {
+            using var response = await client.PostAsJsonAsync(
+                "/api/schools",
+                new
+                {
+                    name = "Без базы",
+                    startDate = ExpectedDefaultStart,
+                    modIds = new[] { "t22need" },
+                },
+                TestContext.Current.CancellationToken);
+
+            Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+            var problem = await response.Content.ReadFromJsonAsync<ProblemResponse>(TestContext.Current.CancellationToken);
+            Assert.Equal("missing-mod", problem?.Code);
+            Assert.Equal("t22ghost", problem?.Missing);
+        }
+    }
+
+    [Fact]
+    public async Task CreateSchool_LoadsRequiredPackBeforeDependentEvenIfListedAfter()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        await ResetAsync(client);
+        var root = await ModsDirectoryAsync(client);
+        using (new TempPack(root, "t22base", """{ "version": "1", "requires": [] }"""))
+        using (new TempPack(root, "t22addon", """{ "version": "1", "requires": ["t22base"] }"""))
+        {
+            using var response = await client.PostAsJsonAsync(
+                "/api/schools",
+                new
+                {
+                    name = "Сначала зависимость",
+                    startDate = ExpectedDefaultStart,
+                    modIds = new[] { "t22addon", "t22base" },
+                },
+                TestContext.Current.CancellationToken);
+
+            response.EnsureSuccessStatusCode();
+            var created = await response.Content.ReadFromJsonAsync<SchoolResponse>(TestContext.Current.CancellationToken);
+            Assert.Equal(["core", "t22base", "t22addon"], created?.ModIds);
+        }
+    }
+
+    [Fact]
+    public async Task CreateSchool_WithCyclicMods_IsRejected()
+    {
+        using var client = fixture.App.CreateHttpClient("server");
+        await ResetAsync(client);
+        var root = await ModsDirectoryAsync(client);
+        using (new TempPack(root, "t22left", """{ "requires": ["t22right"] }"""))
+        using (new TempPack(root, "t22right", """{ "requires": ["t22left"] }"""))
+        {
+            using var response = await client.PostAsJsonAsync(
+                "/api/schools",
+                new
+                {
+                    name = "Цикл",
+                    startDate = ExpectedDefaultStart,
+                    modIds = new[] { "t22left", "t22right" },
+                },
+                TestContext.Current.CancellationToken);
+
+            Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
+            Assert.Equal("mod-cycle", await ProblemCodeAsync(response));
+        }
     }
 
     [Fact]
@@ -418,7 +538,13 @@ public class SchoolApiTests(AppHostFixture fixture)
         return problem?.Code;
     }
 
-    internal sealed record SchoolResponse(int Id, string Name, DateTime GameTime, bool Running, byte SpeedIndex);
+    internal sealed record SchoolResponse(
+        int Id,
+        string Name,
+        DateTime GameTime,
+        bool Running,
+        byte SpeedIndex,
+        IReadOnlyList<string>? ModIds = null);
 
     internal sealed record SchoolsResponse(
         int MaxSchools,
@@ -429,13 +555,58 @@ public class SchoolApiTests(AppHostFixture fixture)
 
     private sealed record RandomNameResponse(string Name);
 
-    private sealed record ProblemResponse(string? Code);
+    private sealed record ProblemResponse(string? Code, string? Missing = null);
 
     private sealed record StatusResponse(uint Tick, int TickRate, int Schools, int MaxSchools, int Connections);
 
     private sealed record ModsResponse(IReadOnlyList<ModInfoResponse> Mods);
 
-    private sealed record ModInfoResponse(string Id, bool Required);
+    private sealed record ModInfoResponse(
+        string Id,
+        bool Required,
+        string Label,
+        string Version,
+        IReadOnlyList<string> Requires);
+
+    private sealed record PathResponse(string Path);
+
+    private static async Task<string> ModsDirectoryAsync(HttpClient client)
+    {
+        var payload = await client.GetFromJsonAsync<PathResponse>(
+            "/api/dev/mods-directory",
+            TestContext.Current.CancellationToken);
+        Assert.NotNull(payload);
+        Assert.False(string.IsNullOrWhiteSpace(payload.Path));
+        return payload.Path;
+    }
+
+    private sealed class TempPack : IDisposable
+    {
+        public TempPack(string modsRoot, string id, string? packJsonc = null)
+        {
+            Path = System.IO.Path.Combine(modsRoot, id);
+            if (Directory.Exists(Path))
+            {
+                Directory.Delete(Path, recursive: true);
+            }
+
+            Directory.CreateDirectory(Path);
+            if (packJsonc is not null)
+            {
+                File.WriteAllText(System.IO.Path.Combine(Path, "pack.jsonc"), packJsonc);
+            }
+        }
+
+        public string Path { get; }
+
+        public void Dispose()
+        {
+            if (Directory.Exists(Path))
+            {
+                Directory.Delete(Path, recursive: true);
+            }
+        }
+    }
 
     private sealed record CatalogResponse(
         IReadOnlyList<DefInfoResponse> Territories,

tests/HSchool.Content.Tests/CatalogLoaderTests.cs

@@ -57,6 +57,20 @@ public class CatalogLoaderTests
         Assert.Contains(log.Warnings, warning => warning.Contains("Sit") && warning.Contains("addon"));
     }
 
+    [Fact]
+    public void UnlabelledDef_WarnsButLoads()
+    {
+        var log = new RecordingLog();
+        var catalog = _loader.Load(
+            [CatalogLoader.CorePackId],
+            [PackDocuments.Def(CatalogLoader.CorePackId, "things", "lamp", """{ "defName": "Lamp", "actions": [] }""")],
+            log);
+
+        Assert.True(catalog.Things.ContainsKey("Lamp"));
+        Assert.Equal("Lamp", catalog.Label("ru", catalog.Things["Lamp"]));
+        Assert.Contains(log.Warnings, warning => warning.Contains("Lamp", StringComparison.Ordinal));
+    }
+
     [Fact]
     public void Text_FallsBackToTheKeyWhenMissing()
     {

tests/HSchool.Content.Tests/PackDocuments.cs

@@ -21,6 +21,9 @@ internal static class PackDocuments
     public static ContentDocument Map(string packId, string jsonc) =>
         new(packId, "maps/default.jsonc", jsonc);
 
+    public static ContentDocument Manifest(string packId, string jsonc) =>
+        new(packId, "pack.jsonc", jsonc);
+
     public static IReadOnlyList<ContentDocument> FromDirectory(string packId, string packRoot)
     {
         var documents = new List<ContentDocument>();

tests/HSchool.Content.Tests/PackIdentityTests.cs

@@ -0,0 +1,114 @@
+namespace HSchool.Content.Tests;
+
+public class PackIdentityTests
+{
+    [Fact]
+    public void PackWithoutManifest_UsesIdAsLabelAndHasNoRequires()
+    {
+        var documents = new[]
+        {
+            PackDocuments.Def("addon", "traits", "shy", """{ "defName": "Shy", "abstract": true }"""),
+        };
+
+        var manifest = PackManifest.FromDocuments("addon", documents);
+
+        Assert.Equal(string.Empty, manifest.Version);
+        Assert.Empty(manifest.Requires);
+        Assert.Equal("addon", PackManifest.Label("addon", "ru", documents));
+        Assert.Equal("addon", PackManifest.Label("addon", "en", documents));
+    }
+
+    [Fact]
+    public void PackLabel_ComesFromTheRequestedLocale()
+    {
+        var documents = new[]
+        {
+            PackDocuments.Manifest(CatalogLoader.CorePackId, """{ "version": "1.0", "requires": [] }"""),
+            PackDocuments.Locale(CatalogLoader.CorePackId, "ru", """{ "core": "Базовая игра" }"""),
+            PackDocuments.Locale(CatalogLoader.CorePackId, "en", """{ "core": "Core" }"""),
+        };
+
+        Assert.Equal("Базовая игра", PackManifest.Label(CatalogLoader.CorePackId, "ru", documents));
+        Assert.Equal("Core", PackManifest.Label(CatalogLoader.CorePackId, "en", documents));
+        Assert.Equal("1.0", PackManifest.FromDocuments(CatalogLoader.CorePackId, documents).Version);
+    }
+
+    [Fact]
+    public void VanillaCore_HasManifestAndLocalizedName()
+    {
+        var root = Path.Combine(AppContext.BaseDirectory, "vanilla");
+        var documents = PackDocuments.FromDirectory(CatalogLoader.CorePackId, root);
+        var manifest = PackManifest.FromDocuments(CatalogLoader.CorePackId, documents);
+
+        Assert.False(string.IsNullOrWhiteSpace(manifest.Version));
+        Assert.Empty(manifest.Requires);
+        Assert.Equal("Базовая игра", PackManifest.Label(CatalogLoader.CorePackId, "ru", documents));
+        Assert.Equal("Core", PackManifest.Label(CatalogLoader.CorePackId, "en", documents));
+    }
+}
+
+public class PackLoadOrderTests
+{
+    [Fact]
+    public void MissingRequirement_NamesTheMissingPack()
+    {
+        var selected = CatalogLoader.NormalizePackOrder(["furniture"]);
+        var manifests = new Dictionary<string, PackManifest>(StringComparer.OrdinalIgnoreCase)
+        {
+            [CatalogLoader.CorePackId] = PackManifest.Empty,
+            ["furniture"] = PackManifest.Parse("furniture", """{ "version": "1", "requires": ["base"] }"""),
+        };
+
+        var ex = Assert.Throws<PackDependencyException>(() => PackLoadOrder.Resolve(selected, manifests));
+
+        Assert.Equal(PackDependencyException.MissingCode, ex.Code);
+        Assert.Equal("base", ex.MissingPackId);
+        Assert.Contains("base", ex.Message, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void DependencyListedAfterDependent_StillLoadsFirst()
+    {
+        var selected = CatalogLoader.NormalizePackOrder(["furniture", "base"]);
+        Assert.Equal([CatalogLoader.CorePackId, "furniture", "base"], selected);
+
+        var manifests = new Dictionary<string, PackManifest>(StringComparer.OrdinalIgnoreCase)
+        {
+            [CatalogLoader.CorePackId] = PackManifest.Empty,
+            ["furniture"] = PackManifest.Parse("furniture", """{ "requires": ["base"] }"""),
+            ["base"] = PackManifest.Empty,
+        };
+
+        var order = PackLoadOrder.Resolve(selected, manifests);
+
+        Assert.Equal([CatalogLoader.CorePackId, "base", "furniture"], order);
+    }
+
+    [Fact]
+    public void Cycle_IsRejected()
+    {
+        var selected = CatalogLoader.NormalizePackOrder(["left", "right"]);
+        var manifests = new Dictionary<string, PackManifest>(StringComparer.OrdinalIgnoreCase)
+        {
+            [CatalogLoader.CorePackId] = PackManifest.Empty,
+            ["left"] = PackManifest.Parse("left", """{ "requires": ["right"] }"""),
+            ["right"] = PackManifest.Parse("right", """{ "requires": ["left"] }"""),
+        };
+
+        var ex = Assert.Throws<PackDependencyException>(() => PackLoadOrder.Resolve(selected, manifests));
+
+        Assert.Equal(PackDependencyException.CycleCode, ex.Code);
+        Assert.Null(ex.MissingPackId);
+    }
+
+    [Fact]
+    public void PlayerOrder_IsKeptWhenRequiresDoNotConstrainIt()
+    {
+        var selected = CatalogLoader.NormalizePackOrder(["zebra", "apple"]);
+        var manifests = PackLoadOrder.ManifestsFrom(selected, []);
+
+        var order = PackLoadOrder.Resolve(selected, manifests);
+
+        Assert.Equal([CatalogLoader.CorePackId, "zebra", "apple"], order);
+    }
+}

tests/HSchool.Content.Tests/VanillaCoreTests.cs

@@ -115,6 +115,7 @@ public class VanillaCoreTests
         keys.AddRange(Names(catalog.DayFrames.Values));
         keys.AddRange(Names(catalog.Holidays.Values));
         keys.AddRange(Names(catalog.Behavior.Values));
+        keys.AddRange(catalog.PackIds);
 
         // Derived in code, so no def carries them.
         keys.Add(BodyBuilds.Attribute);