diff --git a/src/core/Deal.Api/Endpoints/CardDetailsEndpoints.cs b/src/core/Deal.Api/Endpoints/CardDetailsEndpoints.cs
index 0e2054e..42894a2 100644
--- a/src/core/Deal.Api/Endpoints/CardDetailsEndpoints.cs
+++ b/src/core/Deal.Api/Endpoints/CardDetailsEndpoints.cs
@@ -136,10 +136,8 @@ public static class CardDetailsEndpoints
         }
 
         CardsService service = context.RequestServices.GetRequiredService<CardsService>();
-        CardDto? card = await service.TakeCardAsync(body.CardId ?? body.LeadId ?? string.Empty, ct);
-        return card is null
-            ? EndpointResults.NotFound(CardNotFoundDetail)
-            : await ReadCardAsync(context, card.Id, ct);
+        CardDto card = await service.TakeCardAsync(body.CardId ?? body.LeadId ?? string.Empty, ct);
+        return await ReadCardAsync(context, card.Id, ct);
     }
 
     // POST /api/cards/clear-rejected: полная очистка терминальной стадии «Отклонено».
@@ -261,11 +259,7 @@ public static class CardDetailsEndpoints
         foreach (IFormFile file in form.Files)
         {
             await using Stream content = file.OpenReadStream();
-            CardFileDto? entry = await cardsService.AddFileAsync(cardId, file.FileName, file.ContentType, content, file.Length, ct);
-            if (entry is null)
-            {
-                return EndpointResults.NotFound(CardNotFoundDetail);
-            }
+            await cardsService.AddFileAsync(cardId, file.FileName, file.ContentType, content, file.Length, ct);
         }
 
         return await ReadCardAsync(context, cardId, ct);
@@ -286,11 +280,7 @@ public static class CardDetailsEndpoints
         }
 
         CardsService cardsService = context.RequestServices.GetRequiredService<CardsService>();
-        CardFileDto? entry = await cardsService.GetFileEntryAsync(cardId, fileId, ct);
-        if (entry is null)
-        {
-            return EndpointResults.NotFound(CardNotFoundDetail);
-        }
+        CardFileDto entry = await cardsService.GetFileEntryAsync(cardId, fileId, ct);
 
         if (string.IsNullOrWhiteSpace(entry.ObjectKey))
         {
@@ -339,10 +329,8 @@ public static class CardDetailsEndpoints
         }
 
         CardsService cardsService = context.RequestServices.GetRequiredService<CardsService>();
-        CardDto? card = await cardsService.RemoveFileAsync(cardId, fileId, ct);
-        return card is null
-            ? EndpointResults.NotFound(CardNotFoundDetail)
-            : await ReadCardAsync(context, cardId, ct);
+        await cardsService.RemoveFileAsync(cardId, fileId, ct);
+        return await ReadCardAsync(context, cardId, ct);
     }
 
     // POST /api/cards/{cardId}/reminder {at: epoch-ms}: установить напоминание. Ответ — карточка.
diff --git a/src/core/Deal.Api/Endpoints/CardsEndpoints.cs b/src/core/Deal.Api/Endpoints/CardsEndpoints.cs
index c2f41e1..a000360 100644
--- a/src/core/Deal.Api/Endpoints/CardsEndpoints.cs
+++ b/src/core/Deal.Api/Endpoints/CardsEndpoints.cs
@@ -209,11 +209,7 @@ public static class CardsEndpoints
         }
 
         CardsService cardsService = context.RequestServices.GetRequiredService<CardsService>();
-        CardDto? card = await cardsService.TrashCardAsync(cardId, ct);
-        if (card is null)
-        {
-            return EndpointResults.NotFound(CardNotFoundDetail);
-        }
+        await cardsService.TrashCardAsync(cardId, ct);
 
         await AuditAppender.AppendTenantAsync(context, AuditEvents.CardTrashed, new { cardId }, ct);
         return Results.Ok(new { ok = true });
@@ -230,11 +226,7 @@ public static class CardsEndpoints
         }
 
         CardsService cardsService = context.RequestServices.GetRequiredService<CardsService>();
-        string? col = await cardsService.RestoreCardAsync(cardId, ct);
-        if (col is null)
-        {
-            return EndpointResults.NotFound(CardNotFoundDetail);
-        }
+        string col = await cardsService.RestoreCardAsync(cardId, ct);
 
         await AuditAppender.AppendTenantAsync(context, AuditEvents.CardRestored, new { cardId, col }, ct);
         return Results.Ok(new { ok = true, col });
diff --git a/src/core/Deal.Api/Endpoints/ContainersEndpoints.cs b/src/core/Deal.Api/Endpoints/ContainersEndpoints.cs
index bbab4aa..8e63672 100644
--- a/src/core/Deal.Api/Endpoints/ContainersEndpoints.cs
+++ b/src/core/Deal.Api/Endpoints/ContainersEndpoints.cs
@@ -19,9 +19,6 @@ public static class ContainersEndpoints
     // OpenAPI-тег группы.
     private const string OpenApiTag = "containers";
 
-    // 404 PATCH/accept: контейнер не найден.
-    private const string ContainerNotFoundDetail = "Контейнер не найден";
-
     // 400: отсутствующий/явный null name контейнера.
     private const string ContainerNameRequiredDetail = "Укажите название колонки";
 
@@ -143,7 +140,7 @@ public static class ContainersEndpoints
         }
 
         ContainersService containers = context.RequestServices.GetRequiredService<ContainersService>();
-        ContainerDto? updated = await containers.PatchAsync(
+        ContainerDto updated = await containers.PatchAsync(
             containerId,
             new ContainerPatchDto(
                 patchBody.Name,
@@ -155,10 +152,6 @@ public static class ContainersEndpoints
                 NormalizeWireRules(patchBody.Rules),
                 patchBody.Policy),
             ct);
-        if (updated is null)
-        {
-            return EndpointResults.NotFound(ContainerNotFoundDetail);
-        }
 
         await AuditAppender.AppendTenantAsync(context, AuditEvents.ContainerUpdated, new { id = updated.Id }, ct);
         return Results.Ok(new { id = updated.Id });
@@ -176,11 +169,7 @@ public static class ContainersEndpoints
         }
 
         ContainersService containers = context.RequestServices.GetRequiredService<ContainersService>();
-        ContainerDto? accepted = await containers.AcceptSuggestedAsync(containerId, ct);
-        if (accepted is null)
-        {
-            return EndpointResults.NotFound(ContainerNotFoundDetail);
-        }
+        ContainerDto accepted = await containers.AcceptSuggestedAsync(containerId, ct);
 
         await AuditAppender.AppendTenantAsync(context, AuditEvents.ContainerUpdated, new { id = accepted.Id }, ct);
         return Results.Ok(accepted);
diff --git a/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Files.cs b/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Files.cs
index 33e0ee1..f0bfc89 100644
--- a/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Files.cs
+++ b/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Files.cs
@@ -1,5 +1,6 @@
 using Deal.Contracts.Integrations.Abstractions;
 using Deal.Modules.Kanban.Application.Models;
+using Deal.SharedKernel.Errors;
 
 namespace Deal.Modules.Kanban.Application.Services;
 
@@ -18,6 +19,10 @@ public sealed partial class CardsService
 
     private const string DefaultAttachmentName = "file";
 
+    // Имена сущностей для текстов ошибок «не найдено».
+    private const string CardEntityName = "Карточка";
+    private const string CardFileEntityName = "Файл карточки";
+
     /// <summary>
     /// Добавляет файл карточке
     /// </summary>
@@ -26,8 +31,9 @@ public sealed partial class CardsService
     /// <param name="contentType">MIME-тип загрузки (может быть null/пустым — детект по расширению).</param>
     /// <param name="content">Поток содержимого файла (читается хранилищем с позиции 0).</param>
     /// <param name="size">Длина содержимого в байтах (пишется в метаданные записи).</param>
-    /// <returns>Метаданные добавленного файла или null — карточки нет (404).</returns>
-    public async Task<CardFileDto?> AddFileAsync(
+    /// <returns>Метаданные добавленного файла.</returns>
+    /// <exception cref="NotFoundException">Карточка не найдена.</exception>
+    public async Task<CardFileDto> AddFileAsync(
         string cardId,
         string fileName,
         string? contentType,
@@ -37,11 +43,8 @@ public sealed partial class CardsService
     {
         ArgumentNullException.ThrowIfNull(content);
 
-        CardDto? card = await _store.GetCardAsync(cardId, ct);
-        if (card is null)
-        {
-            return null;
-        }
+        CardDto card = await _store.GetCardAsync(cardId, ct)
+            ?? throw new NotFoundException(CardEntityName, cardId);
 
         string name = string.IsNullOrWhiteSpace(fileName) ? DefaultAttachmentName : fileName;
         CardFileKind kind = FileKindDetector.Detect(name, contentType);
@@ -62,7 +65,7 @@ public sealed partial class CardsService
             // Карточка исчезла между чтением и записью (гонка): объект-сирота в хранилище не нужен —
             // удаляем и отвечаем 404-семантикой (DeleteAsync сбои не бросает).
             await _storage.DeleteAsync(objectKey, ct);
-            return null;
+            throw new NotFoundException(CardEntityName, cardId);
         }
 
         return entry;
@@ -73,19 +76,18 @@ public sealed partial class CardsService
     /// </summary>
     /// <param name="cardId">Id карточки (<c>c_...</c>).</param>
     /// <param name="fileId">Id записи файла (<c>pf_...</c>).</param>
-    /// <returns>Метаданные записи файла либо null (карточка/запись не найдены).</returns>
-    public async Task<CardFileDto?> GetFileEntryAsync(
+    /// <returns>Метаданные записи файла.</returns>
+    /// <exception cref="NotFoundException">Карточка или запись файла не найдены.</exception>
+    public async Task<CardFileDto> GetFileEntryAsync(
         string cardId,
         string fileId,
         CancellationToken ct)
     {
-        CardDto? card = await _store.GetCardAsync(cardId, ct);
-        if (card is null)
-        {
-            return null;
-        }
+        CardDto card = await _store.GetCardAsync(cardId, ct)
+            ?? throw new NotFoundException(CardEntityName, cardId);
 
-        return card.Files.FirstOrDefault(file => file.Id == fileId);
+        return card.Files.FirstOrDefault(file => file.Id == fileId)
+            ?? throw new NotFoundException(CardFileEntityName, fileId);
     }
 
     /// <summary>
@@ -93,17 +95,15 @@ public sealed partial class CardsService
     /// </summary>
     /// <param name="cardId">Id карточки (<c>c_...</c>).</param>
     /// <param name="fileId">Id удаляемой записи файла (<c>pf_...</c>).</param>
-    /// <returns>Карточка после удаления (без записи) либо null — карточки нет (404-семантика).</returns>
-    public async Task<CardDto?> RemoveFileAsync(
+    /// <returns>Карточка после удаления (без записи).</returns>
+    /// <exception cref="NotFoundException">Карточка или запись файла не найдены.</exception>
+    public async Task<CardDto> RemoveFileAsync(
         string cardId,
         string fileId,
         CancellationToken ct)
     {
-        CardDto? card = await _store.GetCardAsync(cardId, ct);
-        if (card is null)
-        {
-            return null;
-        }
+        CardDto card = await _store.GetCardAsync(cardId, ct)
+            ?? throw new NotFoundException(CardEntityName, cardId);
 
         CardFileDto? entry = card.Files.FirstOrDefault(file => file.Id == fileId);
         if (entry is not null && !string.IsNullOrWhiteSpace(entry.ObjectKey))
@@ -113,11 +113,11 @@ public sealed partial class CardsService
 
         if (!await _store.RemoveFileAsync(cardId, fileId, ct))
         {
-            return null;
+            throw new NotFoundException(CardFileEntityName, fileId);
         }
 
         return await _store.GetCardAsync(cardId, ct)
-            ?? throw new InvalidOperationException("Карточка не прочиталась после удаления файла: " + cardId);
+            ?? throw new NotFoundException(CardEntityName, cardId);
     }
 
     private static string BuildObjectKey(
diff --git a/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Operations.cs b/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Operations.cs
index df3471a..1378c99 100644
--- a/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Operations.cs
+++ b/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Operations.cs
@@ -2,6 +2,7 @@ using Deal.Contracts.Integrations.Models;
 using Deal.Modules.Cards.Application.Models;
 using Deal.Modules.Kanban.Application.Abstractions;
 using Deal.Modules.Kanban.Application.Models;
+using Deal.SharedKernel.Errors;
 
 namespace Deal.Modules.Kanban.Application.Services;
 
@@ -87,8 +88,9 @@ public sealed partial class CardsService
     /// Перенос карточки в корзину
     /// </summary>
     /// <param name="cardId">Id карточки (<c>c_...</c>).</param>
-    /// <returns>Карточка после переноса (при no-op — как была) либо null — карточки нет (404).</returns>
-    public Task<CardDto?> TrashCardAsync(string cardId, CancellationToken ct)
+    /// <returns>Карточка после переноса (при no-op — как была).</returns>
+    /// <exception cref="NotFoundException">Карточка не найдена.</exception>
+    public Task<CardDto> TrashCardAsync(string cardId, CancellationToken ct)
     {
         return TrashCardAsync(cardId, teach: true, ct);
     }
@@ -98,17 +100,15 @@ public sealed partial class CardsService
     /// </summary>
     /// <param name="cardId">Id карточки (<c>c_...</c>).</param>
     /// <param name="teach">True — писать сигнал «спам» (действие пользователя); false — не писать.</param>
-    /// <returns>Карточка после переноса (при no-op — как была) либо null — карточки нет (404).</returns>
-    public async Task<CardDto?> TrashCardAsync(
+    /// <returns>Карточка после переноса (при no-op — как была).</returns>
+    /// <exception cref="NotFoundException">Карточка не найдена.</exception>
+    public async Task<CardDto> TrashCardAsync(
         string cardId,
         bool teach,
         CancellationToken ct)
     {
-        CardDto? card = await _store.GetCardAsync(cardId, ct);
-        if (card is null)
-        {
-            return null;
-        }
+        CardDto card = await _store.GetCardAsync(cardId, ct)
+            ?? throw new NotFoundException(CardEntityName, cardId);
 
         if (card.Col == CardIds.Trash)
         {
@@ -122,21 +122,20 @@ public sealed partial class CardsService
             await _mlClient.PushAsync(text, MlLearningLabels.Spam, PushWeightUser, ct);
         }
 
-        return await _store.GetCardAsync(cardId, ct);
+        return await _store.GetCardAsync(cardId, ct)
+            ?? throw new NotFoundException(CardEntityName, cardId);
     }
 
     /// <summary>
     /// Возврат карточки из архива/корзины на канбан.
     /// </summary>
     /// <param name="cardId">Id карточки (<c>c_...</c>).</param>
-    /// <returns>Колонка возврата (inbox/доска) либо null — карточки нет (404).</returns>
-    public async Task<string?> RestoreCardAsync(string cardId, CancellationToken ct)
+    /// <returns>Колонка возврата (inbox/доска).</returns>
+    /// <exception cref="NotFoundException">Карточка не найдена.</exception>
+    public async Task<string> RestoreCardAsync(string cardId, CancellationToken ct)
     {
-        CardDto? card = await _store.GetCardAsync(cardId, ct);
-        if (card is null)
-        {
-            return null;
-        }
+        CardDto card = await _store.GetCardAsync(cardId, ct)
+            ?? throw new NotFoundException(CardEntityName, cardId);
 
         string back = await ResolveReturnColAsync(card.PrevCol, ct);
         string text = LearningText(card);
diff --git a/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Selected.cs b/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Selected.cs
index bce0780..69899fd 100644
--- a/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Selected.cs
+++ b/src/core/Deal.Modules.Kanban/Application/Services/CardsService.Selected.cs
@@ -3,6 +3,7 @@ using Deal.Modules.Cards.Application.Models;
 using Deal.Modules.Cards.Application.Sources;
 using Deal.Modules.Kanban.Application.Abstractions;
 using Deal.Modules.Kanban.Application.Models;
+using Deal.SharedKernel.Errors;
 
 namespace Deal.Modules.Kanban.Application.Services;
 
@@ -101,14 +102,12 @@ public sealed partial class CardsService
     /// «Взять в работу»
     /// </summary>
     /// <param name="cardId">Id карточки (<c>c_...</c>).</param>
-    /// <returns>Карточка в стадии planned; null — карточки нет (404).</returns>
-    public async Task<CardDto?> TakeCardAsync(string cardId, CancellationToken ct)
+    /// <returns>Карточка в стадии planned.</returns>
+    /// <exception cref="NotFoundException">Карточка не найдена.</exception>
+    public async Task<CardDto> TakeCardAsync(string cardId, CancellationToken ct)
     {
-        CardDto? card = await _store.GetCardAsync(cardId, ct);
-        if (card is null)
-        {
-            return null;
-        }
+        CardDto card = await _store.GetCardAsync(cardId, ct)
+            ?? throw new NotFoundException(CardEntityName, cardId);
 
         if (CardsDefaultContainers.Contains(card.Col))
         {
@@ -120,14 +119,14 @@ public sealed partial class CardsService
         if (!await _store.MoveCardStageAsync(cardId, PlannedStage, entry, nowMs, ct))
         {
             // Карточка исчезла между чтением и переносом (гонка с удалением).
-            return null;
+            throw new NotFoundException(CardEntityName, cardId);
         }
 
         await _store.AddCommentAsync(
             PrefixId.New(KanbanIdPrefixes.Comment), cardId, CommentAuthor, TakenCommentText, ct);
 
         return await _store.GetCardAsync(cardId, ct)
-            ?? throw new InvalidOperationException("Карточка не прочиталась после take: " + cardId);
+            ?? throw new NotFoundException(CardEntityName, cardId);
     }
 
     /// <summary>
@@ -135,8 +134,9 @@ public sealed partial class CardsService
     /// </summary>
     /// <param name="cardId">Id карточки (<c>c_...</c>).</param>
     /// <param name="body">Тело PATCH: ключ → JSON-значение (наличие ключа = поле меняется).</param>
-    /// <returns>Обновлённая карточка или null — карточки нет (404).</returns>
-    public async Task<CardDto?> PatchCardAsync(
+    /// <returns>Обновлённая карточка.</returns>
+    /// <exception cref="NotFoundException">Карточка не найдена.</exception>
+    public async Task<CardDto> PatchCardAsync(
         string cardId,
         IReadOnlyDictionary<string, JsonElement> body,
         CancellationToken ct)
@@ -144,7 +144,13 @@ public sealed partial class CardsService
         ArgumentNullException.ThrowIfNull(body);
 
         bool updated = await _store.PatchCardAsync(cardId, ResolvePatch(body), ct);
-        return updated ? await _store.GetCardAsync(cardId, ct) : null;
+        if (!updated)
+        {
+            throw new NotFoundException(CardEntityName, cardId);
+        }
+
+        return await _store.GetCardAsync(cardId, ct)
+            ?? throw new NotFoundException(CardEntityName, cardId);
     }
 
     /// <summary>
diff --git a/src/core/Deal.Modules.Kanban/Application/Services/ContainersService.cs b/src/core/Deal.Modules.Kanban/Application/Services/ContainersService.cs
index a1168a8..6d75d61 100644
--- a/src/core/Deal.Modules.Kanban/Application/Services/ContainersService.cs
+++ b/src/core/Deal.Modules.Kanban/Application/Services/ContainersService.cs
@@ -4,6 +4,7 @@ using Deal.Modules.Kanban.Application.Abstractions;
 using Deal.Modules.Kanban.Application.Models;
 using Deal.Modules.Settings.Application.Abstractions;
 using Deal.Modules.Settings.Application.Models;
+using Deal.SharedKernel.Errors;
 
 namespace Deal.Modules.Kanban.Application.Services;
 
@@ -19,6 +20,9 @@ public sealed class ContainersService(ICardStore store, ISettingsStore settings)
     /// </summary>
     public const string DefaultContainerName = "Новая колонка";
 
+    // Имя сущности для текста ошибки «не найдено».
+    private const string ContainerEntityName = "Контейнер";
+
     // Палитра колонок по умолчанию: цвет = Palette[order % 8], если цвет не задан.
     private static readonly string[] Palette =
         ["#818cf8", "#fbbf24", "#22d3ee", "#e879f9", "#34d399", "#fb7185", "#a78bfa", "#f97316"];
@@ -53,17 +57,15 @@ public sealed class ContainersService(ICardStore store, ISettingsStore settings)
     }
 
     /// <summary>
-    /// Один контейнер со счётчиками; null — контейнера нет.
+    /// Один контейнер со счётчиками
     /// </summary>
     /// <param name="containerId">Id контейнера.</param>
-    /// <returns>Контейнер со счётчиками либо null.</returns>
-    public async Task<ContainerDto?> GetAsync(string containerId, CancellationToken ct)
+    /// <returns>Контейнер со счётчиками.</returns>
+    /// <exception cref="NotFoundException">Контейнер не найден.</exception>
+    public async Task<ContainerDto> GetAsync(string containerId, CancellationToken ct)
     {
-        ContainerDto? container = await store.GetContainerAsync(containerId, ct);
-        if (container is null)
-        {
-            return null;
-        }
+        ContainerDto container = await store.GetContainerAsync(containerId, ct)
+            ?? throw new NotFoundException(ContainerEntityName, containerId);
 
         IReadOnlyDictionary<string, CardColumnCountDto> counts = await store.CountCardsByColAsync(ct);
         ContainerCountsDto containerCounts = counts.TryGetValue(container.Id, out CardColumnCountDto? count)
@@ -107,17 +109,15 @@ public sealed class ContainersService(ICardStore store, ISettingsStore settings)
     /// </summary>
     /// <param name="containerId">Id контейнера.</param>
     /// <param name="patch">Изменения; null-поле означает «не менять».</param>
-    /// <returns>Контейнер после патча; null — контейнера нет (404 «Контейнер не найден»).</returns>
-    public async Task<ContainerDto?> PatchAsync(
+    /// <returns>Контейнер после патча.</returns>
+    /// <exception cref="NotFoundException">Контейнер не найден.</exception>
+    public async Task<ContainerDto> PatchAsync(
         string containerId,
         ContainerPatchDto patch,
         CancellationToken ct)
     {
-        ContainerDto? current = await store.GetContainerAsync(containerId, ct);
-        if (current is null)
-        {
-            return null;
-        }
+        ContainerDto current = await store.GetContainerAsync(containerId, ct)
+            ?? throw new NotFoundException(ContainerEntityName, containerId);
 
         ContainerDto updated = ApplyPatch(current, patch);
         await store.UpdateContainerAsync(updated, ct);
@@ -128,8 +128,9 @@ public sealed class ContainersService(ICardStore store, ISettingsStore settings)
     /// Принимает ИИ-предложение
     /// </summary>
     /// <param name="containerId">Id контейнера-предложения.</param>
-    /// <returns>Контейнер после принятия; null — контейнера нет (404).</returns>
-    public Task<ContainerDto?> AcceptSuggestedAsync(string containerId, CancellationToken ct)
+    /// <returns>Контейнер после принятия.</returns>
+    /// <exception cref="NotFoundException">Контейнер не найден.</exception>
+    public Task<ContainerDto> AcceptSuggestedAsync(string containerId, CancellationToken ct)
     {
         return PatchAsync(containerId, new ContainerPatchDto(
             Name: null,
diff --git a/src/core/tests/Deal.Tests.Unit/Contracts/CardsServiceTests.cs b/src/core/tests/Deal.Tests.Unit/Contracts/CardsServiceTests.cs
index 717e77e..d6ec709 100644
--- a/src/core/tests/Deal.Tests.Unit/Contracts/CardsServiceTests.cs
+++ b/src/core/tests/Deal.Tests.Unit/Contracts/CardsServiceTests.cs
@@ -1,9 +1,10 @@
 using Deal.Contracts.Integrations.Models;
-using Deal.Tests.Unit.Support;
 using Deal.Modules.Cards.Application.Sources;
 using Deal.Modules.Kanban.Application.Models;
 using Deal.Modules.Kanban.Application.Services;
+using Deal.SharedKernel.Errors;
 using Deal.Tests.Unit.Modules.Settings;
+using Deal.Tests.Unit.Support;
 
 namespace Deal.Tests.Unit.Contracts;
 
@@ -343,13 +344,13 @@ public sealed class CardsServiceTests
     }
 
     [Fact]
-    public async Task Trash_CardMissing_ReturnsNull()
+    public async Task Trash_CardMissing_ThrowsNotFound()
     {
         (CardsService service, _, _, TestMlClient ml) = Create();
 
-        CardDto? result = await service.TrashCardAsync("l_ghost", CancellationToken.None);
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.TrashCardAsync("l_ghost", CancellationToken.None));
 
-        Assert.Null(result); // эндпоинт отвечает 404 «Карточка не найдена»
         Assert.Empty(ml.Pushed);
     }
 
@@ -425,13 +426,12 @@ public sealed class CardsServiceTests
     }
 
     [Fact]
-    public async Task Restore_CardMissing_ReturnsNull()
+    public async Task Restore_CardMissing_ThrowsNotFound()
     {
         (CardsService service, _, _, _) = Create();
 
-        string? back = await service.RestoreCardAsync("l_ghost", CancellationToken.None);
-
-        Assert.Null(back); // эндпоинт отвечает 404 «Карточка не найдена»
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.RestoreCardAsync("l_ghost", CancellationToken.None));
     }
 
 
diff --git a/src/core/tests/Deal.Tests.Unit/Support/CardsServiceFilesTests.cs b/src/core/tests/Deal.Tests.Unit/Support/CardsServiceFilesTests.cs
index cecfa82..d78ade6 100644
--- a/src/core/tests/Deal.Tests.Unit/Support/CardsServiceFilesTests.cs
+++ b/src/core/tests/Deal.Tests.Unit/Support/CardsServiceFilesTests.cs
@@ -1,6 +1,7 @@
 using System.Text;
 using Deal.Modules.Kanban.Application.Models;
 using Deal.Modules.Kanban.Application.Services;
+using Deal.SharedKernel.Errors;
 using Deal.Tests.Unit.Contracts;
 using Deal.Tests.Unit.Modules.Settings;
 
@@ -73,14 +74,13 @@ public sealed class CardsServiceFilesTests
     }
 
     [Fact]
-    public async Task Add_CardMissing_ReturnsNullAndDoesNotWriteObject()
+    public async Task Add_CardMissing_ThrowsAndDoesNotWriteObject()
     {
         (CardsService service, TestKanjStore store, TestFileStorage storage) = Create();
 
-        CardFileDto? entry = await service.AddFileAsync(
-            "c_missing", "photo.png", "image/png", new MemoryStream("x"u8.ToArray()), 1, CancellationToken.None);
+        await Assert.ThrowsAsync<NotFoundException>(() => service.AddFileAsync(
+            "c_missing", "photo.png", "image/png", new MemoryStream("x"u8.ToArray()), 1, CancellationToken.None));
 
-        Assert.Null(entry); // эндпоинт отвечает 404 «Карточка не найдена»
         Assert.Empty(storage.StoredObjectKeys); // «add на несуществующей карточке не пишет объект»
         Assert.Empty(store.CardDtos);
     }
@@ -151,25 +151,23 @@ public sealed class CardsServiceFilesTests
     }
 
     [Fact]
-    public async Task GetEntry_CardMissing_ReturnsNull()
+    public async Task GetEntry_CardMissing_ThrowsNotFound()
     {
         (CardsService service, _, _) = Create();
 
-        CardFileDto? entry = await service.GetFileEntryAsync("c_missing", "pf_1", CancellationToken.None);
-
-        Assert.Null(entry); // 404 «Карточка не найдена» у эндпоинта
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.GetFileEntryAsync("c_missing", "pf_1", CancellationToken.None));
     }
 
     [Fact]
-    public async Task GetEntry_FileNotInMetadata_ReturnsNull()
+    public async Task GetEntry_FileNotInMetadata_ThrowsNotFound()
     {
         (CardsService service, TestKanjStore store, _) = Create();
         store.SeedCard(Card("c_1")
             with { Files = new[] { new CardFileDto("pf_1", "tz.pdf", 100, "document", "Документ", "k") } });
 
-        CardFileDto? entry = await service.GetFileEntryAsync("c_1", "pf_ghost", CancellationToken.None);
-
-        Assert.Null(entry); // файла нет в метаданных карточки — 404-семантика
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.GetFileEntryAsync("c_1", "pf_ghost", CancellationToken.None));
     }
 
 
@@ -225,13 +223,13 @@ public sealed class CardsServiceFilesTests
     }
 
     [Fact]
-    public async Task Remove_CardMissing_ReturnsNullWithoutStorageDelete()
+    public async Task Remove_CardMissing_ThrowsWithoutStorageDelete()
     {
         (CardsService service, _, TestFileStorage storage) = Create();
 
-        CardDto? card = await service.RemoveFileAsync("c_missing", "pf_1", CancellationToken.None);
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.RemoveFileAsync("c_missing", "pf_1", CancellationToken.None));
 
-        Assert.Null(card); // эндпоинт отвечает 404 «Карточка не найдена»
         Assert.Empty(storage.DeletedKeys);
     }
 
diff --git a/src/core/tests/Deal.Tests.Unit/Support/CardsServiceSelectedTests.cs b/src/core/tests/Deal.Tests.Unit/Support/CardsServiceSelectedTests.cs
index e2317c2..871d678 100644
--- a/src/core/tests/Deal.Tests.Unit/Support/CardsServiceSelectedTests.cs
+++ b/src/core/tests/Deal.Tests.Unit/Support/CardsServiceSelectedTests.cs
@@ -1,6 +1,7 @@
 using System.Text.Json;
 using Deal.Modules.Kanban.Application.Models;
 using Deal.Modules.Kanban.Application.Services;
+using Deal.SharedKernel.Errors;
 using Deal.Tests.Unit.Contracts;
 using Deal.Tests.Unit.Modules.Settings;
 
@@ -99,13 +100,13 @@ public sealed class CardsServiceSelectedTests
 
 
     [Fact]
-    public async Task TakeCard_CardMissing_ReturnsNullAndCreatesNothing()
+    public async Task TakeCard_CardMissing_ThrowsAndCreatesNothing()
     {
         (CardsService service, TestKanjStore store, _, _) = Create();
 
-        CardDto? card = await service.TakeCardAsync("c_missing", CancellationToken.None);
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.TakeCardAsync("c_missing", CancellationToken.None));
 
-        Assert.Null(card);
         Assert.Empty(store.CardDtos);
     }
 
@@ -122,8 +123,7 @@ public sealed class CardsServiceSelectedTests
             stack: new[] { "Python", "aiogram" },
             budget: new CardBudgetDto(From: 1600, To: 2200, Cur: "USD")));
 
-        CardDto card = await service.TakeCardAsync("c_1", CancellationToken.None)
-            ?? throw new InvalidOperationException("take вернул null при существующей карточке");
+        CardDto card = await service.TakeCardAsync("c_1", CancellationToken.None);
 
         Assert.Equal("c_1", card.Id);
         Assert.Equal("planned", card.Col);
@@ -182,8 +182,7 @@ public sealed class CardsServiceSelectedTests
                 ("tzText", "ТЗ"),
                 ("stack", new[] { "C#", ".NET" }), // стек — полная замена массива
                 ("budget", new { from = 500, cur = "EUR" })),
-            CancellationToken.None)
-            ?? throw new InvalidOperationException("patch вернул null при существующей карточке");
+            CancellationToken.None);
 
         Assert.Equal("Новый заголовок", card.Title);
         Assert.Equal(string.Empty, card.Summary); // summary очищена пустой строкой
@@ -255,16 +254,14 @@ public sealed class CardsServiceSelectedTests
     }
 
     [Fact]
-    public async Task Patch_CardMissing_ReturnsNull()
+    public async Task Patch_CardMissing_ThrowsNotFound()
     {
         (CardsService service, _, _, _) = Create();
 
-        CardDto? card = await service.PatchCardAsync(
+        await Assert.ThrowsAsync<NotFoundException>(() => service.PatchCardAsync(
             "c_missing",
             PatchBody(("title", "Т")),
-            CancellationToken.None);
-
-        Assert.Null(card);
+            CancellationToken.None));
     }
 
 
diff --git a/src/core/tests/Deal.Tests.Unit/Support/ContainersServiceTests.cs b/src/core/tests/Deal.Tests.Unit/Support/ContainersServiceTests.cs
index a329ea2..5084724 100644
--- a/src/core/tests/Deal.Tests.Unit/Support/ContainersServiceTests.cs
+++ b/src/core/tests/Deal.Tests.Unit/Support/ContainersServiceTests.cs
@@ -1,6 +1,7 @@
 using System.Text.Json;
 using Deal.Modules.Kanban.Application.Models;
 using Deal.Modules.Kanban.Application.Services;
+using Deal.SharedKernel.Errors;
 using Deal.Tests.Unit.Modules.Settings;
 
 namespace Deal.Tests.Unit.Support;
@@ -237,14 +238,12 @@ public sealed class ContainersServiceTests
     }
 
     [Fact]
-    public async Task Patch_UnknownContainer_ReturnsNull()
+    public async Task Patch_UnknownContainer_ThrowsNotFound()
     {
         (ContainersService service, _, _) = Create();
 
-        ContainerDto? result = await service.PatchAsync(
-            "b_missing", Patch(name: "X"), CancellationToken.None);
-
-        Assert.Null(result); // эндпоинт отвечает 404 «Контейнер не найден»
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.PatchAsync("b_missing", Patch(name: "X"), CancellationToken.None));
     }
 
     [Fact]