diff --git a/docs/spec/Код-стайл-Дейл.md b/docs/spec/Код-стайл-Дейл.md
index 2755cef..c0d6579 100644
--- a/docs/spec/Код-стайл-Дейл.md
+++ b/docs/spec/Код-стайл-Дейл.md
@@ -242,11 +242,23 @@
 
 - `try-catch` — только для непредвиденных ошибок, не для управления ходом программы.
 - При пробрасывании выше — `throw;`, а **не** `throw ex;`.
-- Свои исключения наследовать от `Exception`.
+- **Свои доменные исключения наследовать от `DealException`** (`Deal.SharedKernel.Errors`) — базовый тип
+  хранит код ошибки (`ErrorCode`) и умеет брать текст из ресурсов. Состав: `NotFoundException`,
+  `ValidationException`, `ConflictException`, `ServiceUnavailableException`; новые — по тому же образцу.
+- **Не возвращать `null` как штатный результат «не найдено»/ошибки.** Доменный сервис, у которого объект
+  не найден, бросает `NotFoundException` (эндпоинт отдаёт 404 через общий обработчик, а не проверкой
+  `is null` в каждом хендлере). `null` допустим только для **опциональных значений** — парсеры/извлечение
+  полей, выборки-запросы («нет строки» — нормальный результат), `Try*`-паттерн; такие методы должны быть
+  nullable-аннотированы и явно описаны в XML-doc.
 - Исключение создавать всегда, когда функция не может быть выполнена (неверные параметры, нет доступа к
   БД, неизвестные идентификаторы и т.п.).
-- Все исключения должны быть залогированы или показаны пользователю; пустые `catch` запрещены.
-- В лог об ошибке, как правило, писать `StackTrace`.
+- Все исключения должны быть залогированы или показаны пользователю; **пустые `catch` запрещены**.
+- **Единый формат лога ошибки:** понятный русский текст + структурированный контекст (операция, `tenantId`,
+  id сущности, `traceId`). Стектрейс пишется **только в лог**; в ответ/сообщение клиенту он не попадает —
+  наружу отдаётся обобщённый текст и код (обработчики на границах: `DealExceptionHandler`, gRPC-интерцептор).
+- **Тексты исключений/ошибок не хардкодить** — держать в ресурсах (`ErrorMessages.resx`, доступ через
+  `ErrorResources.Format(ErrorResourceKeys.*)` и шаблоны `DealException`), чтобы переводы добавлялись
+  отдельной культурой (`.resx`-спутник) без правок кода.
 
 ## 11. Интерфейсы
 
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.Api/Endpoints/DiscoveryEndpoints.cs b/src/core/Deal.Api/Endpoints/DiscoveryEndpoints.cs
index 25a9d39..f46981d 100644
--- a/src/core/Deal.Api/Endpoints/DiscoveryEndpoints.cs
+++ b/src/core/Deal.Api/Endpoints/DiscoveryEndpoints.cs
@@ -55,8 +55,7 @@ public static class DiscoveryEndpoints
     // Путь лога задачи (GET).
     private const string TaskLogPath = "/tasks/{task_id}/log";
 
-    private const string TaskNotFoundDetail = "Задача не найдена";
-
+    // 404: кандидат не найден.
     private const string CandidateNotFoundDetail = "Кандидат не найден";
 
     private const string AlreadyJoinedDetail = "Уже вступили в этот источник";
@@ -149,8 +148,8 @@ public static class DiscoveryEndpoints
         try
         {
             DiscoveryTasksService tasks = context.RequestServices.GetRequiredService<DiscoveryTasksService>();
-            DiscoveryTaskDto? task = await tasks.PatchAsync(task_id, ToPatch(body), ct);
-            return task is null ? EndpointResults.NotFound(TaskNotFoundDetail) : Results.Ok(task);
+            DiscoveryTaskDto task = await tasks.PatchAsync(task_id, ToPatch(body), ct);
+            return Results.Ok(task);
         }
         catch (DiscoveryValidationException exception)
         {
@@ -169,8 +168,8 @@ public static class DiscoveryEndpoints
         }
 
         DiscoveryTasksService tasks = context.RequestServices.GetRequiredService<DiscoveryTasksService>();
-        bool deleted = await tasks.DeleteAsync(task_id, ct);
-        return deleted ? Results.Ok(new { ok = true }) : EndpointResults.NotFound(TaskNotFoundDetail);
+        await tasks.DeleteAsync(task_id, ct);
+        return Results.Ok(new { ok = true });
     }
 
     private static async Task<IResult> StartTaskAsync(
@@ -186,8 +185,8 @@ public static class DiscoveryEndpoints
         try
         {
             DiscoveryTasksService tasks = context.RequestServices.GetRequiredService<DiscoveryTasksService>();
-            DiscoveryTaskDto? task = await tasks.StartAsync(task_id, ct);
-            return task is null ? EndpointResults.NotFound(TaskNotFoundDetail) : Results.Ok(task);
+            DiscoveryTaskDto task = await tasks.StartAsync(task_id, ct);
+            return Results.Ok(task);
         }
         catch (DiscoveryValidationException exception)
         {
@@ -206,8 +205,8 @@ public static class DiscoveryEndpoints
         }
 
         DiscoveryTasksService tasks = context.RequestServices.GetRequiredService<DiscoveryTasksService>();
-        DiscoveryTaskDto? task = await tasks.PauseAsync(task_id, ct);
-        return task is null ? EndpointResults.NotFound(TaskNotFoundDetail) : Results.Ok(task);
+        DiscoveryTaskDto task = await tasks.PauseAsync(task_id, ct);
+        return Results.Ok(task);
     }
 
     private static async Task<IResult> GenerateKeywordsAsync(
@@ -221,11 +220,7 @@ public static class DiscoveryEndpoints
         }
 
         DiscoveryTasksService tasks = context.RequestServices.GetRequiredService<DiscoveryTasksService>();
-        DiscoveryTaskDto? task = await tasks.GetAsync(task_id, ct);
-        if (task is null)
-        {
-            return EndpointResults.NotFound(TaskNotFoundDetail);
-        }
+        DiscoveryTaskDto task = await tasks.GetAsync(task_id, ct);
 
         ISettingsStore settings = context.RequestServices.GetRequiredService<ISettingsStore>();
         if (!await ReadAiEnabledAsync(settings, ct))
@@ -268,11 +263,7 @@ public static class DiscoveryEndpoints
         }
 
         DiscoveryTasksService tasks = context.RequestServices.GetRequiredService<DiscoveryTasksService>();
-        DiscoveryTaskDto? task = await tasks.GetAsync(task_id, ct);
-        if (task is null)
-        {
-            return EndpointResults.NotFound(TaskNotFoundDetail);
-        }
+        DiscoveryTaskDto task = await tasks.GetAsync(task_id, ct);
 
         DiscoveryCandidatesService candidates = context.RequestServices.GetRequiredService<DiscoveryCandidatesService>();
         IReadOnlyList<DiscoveryCandidateDto> items = await candidates.ListAsync(task_id, status, ct);
@@ -403,11 +394,7 @@ public static class DiscoveryEndpoints
         }
 
         DiscoveryTasksService tasks = context.RequestServices.GetRequiredService<DiscoveryTasksService>();
-        DiscoveryTaskDto? task = await tasks.GetAsync(task_id, ct);
-        if (task is null)
-        {
-            return EndpointResults.NotFound(TaskNotFoundDetail);
-        }
+        DiscoveryTaskDto task = await tasks.GetAsync(task_id, ct);
 
         DiscoveryLogService log = context.RequestServices.GetRequiredService<DiscoveryLogService>();
         IReadOnlyList<DiscoveryLogDto> items = await log.TaskLogAsync(task_id, ct);
diff --git a/src/core/Deal.Api/Middleware/DealExceptionHandler.cs b/src/core/Deal.Api/Middleware/DealExceptionHandler.cs
new file mode 100644
index 0000000..d119b84
--- /dev/null
+++ b/src/core/Deal.Api/Middleware/DealExceptionHandler.cs
@@ -0,0 +1,83 @@
+using Deal.SharedKernel.Errors;
+using Deal.SharedKernel.Resources;
+using Deal.SharedKernel.Tenants.Abstractions;
+using Microsoft.AspNetCore.Diagnostics;
+
+namespace Deal.Api.Middleware;
+
+public sealed class DealExceptionHandler(ILogger<DealExceptionHandler> logger) : IExceptionHandler
+{
+    public async ValueTask<bool> TryHandleAsync(
+        HttpContext httpContext,
+        Exception exception,
+        CancellationToken cancellationToken)
+    {
+        (int statusCode, string errorCode, string detail) = Resolve(exception);
+        LogFailure(httpContext, exception, statusCode, errorCode);
+        httpContext.Response.StatusCode = statusCode;
+        await httpContext.Response.WriteAsJsonAsync(
+            new { detail, code = errorCode },
+            cancellationToken);
+        return true;
+    }
+
+    // Доменные ошибки отдаются по коду; прочие — обобщённый 500 без деталей и стектрейса.
+    private static (int StatusCode, string ErrorCode, string Detail) Resolve(Exception exception)
+        => exception is DealException dealException
+            ? (MapStatusCode(dealException.ErrorCode), dealException.ErrorCode, dealException.Message)
+            : (StatusCodes.Status500InternalServerError,
+               DealErrorCodes.Internal,
+               ErrorResources.Format(ErrorResourceKeys.UnexpectedError));
+
+    // Код ошибки Deal → статус HTTP.
+    private static int MapStatusCode(string errorCode) => errorCode switch
+    {
+        DealErrorCodes.NotFound => StatusCodes.Status404NotFound,
+        DealErrorCodes.Validation => StatusCodes.Status400BadRequest,
+        DealErrorCodes.Conflict => StatusCodes.Status409Conflict,
+        DealErrorCodes.Unavailable => StatusCodes.Status503ServiceUnavailable,
+        _ => StatusCodes.Status500InternalServerError,
+    };
+
+    // Доменные ошибки — Warning без стектрейса; непредвиденные — Error со стектрейсом (только в лог).
+    private void LogFailure(
+        HttpContext context,
+        Exception exception,
+        int statusCode,
+        string errorCode)
+    {
+        string method = context.Request.Method;
+        string path = context.Request.Path.Value ?? "/";
+        string tenantId = ResolveTenantId(context);
+        if (exception is DealException dealException)
+        {
+            logger.LogWarning(
+                "HTTP {Method} {Path} -> {StatusCode} {ErrorCode}; tenant={TenantId} trace={TraceId}: {Message}",
+                method,
+                path,
+                statusCode,
+                errorCode,
+                tenantId,
+                context.TraceIdentifier,
+                dealException.Message);
+            return;
+        }
+
+        logger.LogError(
+            exception,
+            "HTTP {Method} {Path} -> {StatusCode} {ErrorCode}; tenant={TenantId} trace={TraceId}",
+            method,
+            path,
+            statusCode,
+            errorCode,
+            tenantId,
+            context.TraceIdentifier);
+    }
+
+    // Идентификатор тенанта запроса; вне tenant-запроса — "-".
+    private static string ResolveTenantId(HttpContext context)
+    {
+        ITenantContext? tenantContext = context.RequestServices?.GetService<ITenantContext>();
+        return tenantContext?.TenantId?.Value ?? "-";
+    }
+}
diff --git a/src/core/Deal.Api/Program.cs b/src/core/Deal.Api/Program.cs
index 38dbbf3..a1eb42e 100644
--- a/src/core/Deal.Api/Program.cs
+++ b/src/core/Deal.Api/Program.cs
@@ -133,6 +133,8 @@ TokenLimitDefaults tenantLimitDefaults = new(
 builder.Services.AddDealPersistence(tenantLimitDefaults);
 
 builder.Services.AddDealSecurity(builder.Environment.ContentRootPath);
+builder.Services.AddExceptionHandler<DealExceptionHandler>();
+builder.Services.AddProblemDetails();
 
 MlServiceOptions mlOptions = builder.Configuration.GetSection(servicesSectionName).Get<MlServiceOptions>() ?? new MlServiceOptions();
 builder.Services.AddSingleton(mlOptions);
@@ -326,6 +328,7 @@ if (forwardedHeadersConfig.Enabled)
     app.UseForwardedHeaders(BuildForwardedHeadersOptions(forwardedHeadersConfig));
 }
 
+app.UseExceptionHandler();
 app.UseMiddleware<HttpAccessLogMiddleware>();
 
 app.UseCors(corsPolicyName);
diff --git a/src/core/Deal.Modules.Discovery/Application/Services/DiscoveryTasksService.cs b/src/core/Deal.Modules.Discovery/Application/Services/DiscoveryTasksService.cs
index 3a6c515..831b150 100644
--- a/src/core/Deal.Modules.Discovery/Application/Services/DiscoveryTasksService.cs
+++ b/src/core/Deal.Modules.Discovery/Application/Services/DiscoveryTasksService.cs
@@ -4,6 +4,7 @@ using Deal.Modules.Discovery.Application.Extensions;
 using Deal.Modules.Discovery.Application.Models;
 using Deal.Modules.Settings.Application.Abstractions;
 using Deal.Modules.Settings.Application.Models;
+using Deal.SharedKernel.Errors;
 
 namespace Deal.Modules.Discovery.Application.Services;
 
@@ -12,6 +13,9 @@ namespace Deal.Modules.Discovery.Application.Services;
 /// </summary>
 public sealed class DiscoveryTasksService(IDiscoveryStore store, DiscoveryPlanGuard planGuard, ISettingsStore settings)
 {
+    // Имя сущности для текста ошибки «не найдено».
+    private const string TaskEntityName = "Задача поиска";
+
     /// <summary>
     /// 400 create: пустое название после Trim.
     /// </summary>
@@ -35,10 +39,12 @@ public sealed class DiscoveryTasksService(IDiscoveryStore store, DiscoveryPlanGu
     /// Одна задача по id.
     /// </summary>
     /// <param name="taskId">Id задачи (<c>dt_...</c>).</param>
-    /// <returns>Задача или null (404 «Задача не найдена» у эндпоинта).</returns>
-    public Task<DiscoveryTaskDto?> GetAsync(string taskId, CancellationToken ct)
+    /// <returns>Задача.</returns>
+    /// <exception cref="NotFoundException">Задача не найдена.</exception>
+    public async Task<DiscoveryTaskDto> GetAsync(string taskId, CancellationToken ct)
     {
-        return store.GetTaskAsync(taskId, ct);
+        return await store.GetTaskAsync(taskId, ct).ConfigureAwait(false)
+            ?? throw new NotFoundException(TaskEntityName, taskId);
     }
 
     /// <summary>
@@ -102,18 +108,16 @@ public sealed class DiscoveryTasksService(IDiscoveryStore store, DiscoveryPlanGu
     /// </summary>
     /// <param name="taskId">Id задачи (<c>dt_...</c>).</param>
     /// <param name="patch">Изменяемые поля (null — не меняется).</param>
-    /// <returns>Обновлённая задача либо null (404 «Задача не найдена»).</returns>
+    /// <returns>Обновлённая задача.</returns>
+    /// <exception cref="NotFoundException">Задача не найдена.</exception>
     /// <exception cref="DiscoveryValidationException">Новый план вне границ / бюджет исчерпан.</exception>
-    public async Task<DiscoveryTaskDto?> PatchAsync(
+    public async Task<DiscoveryTaskDto> PatchAsync(
         string taskId,
         DiscoveryTaskPatch patch,
         CancellationToken ct)
     {
-        DiscoveryTaskDto? current = await store.GetTaskAsync(taskId, ct).ConfigureAwait(false);
-        if (current is null)
-        {
-            return null;
-        }
+        DiscoveryTaskDto current = await store.GetTaskAsync(taskId, ct).ConfigureAwait(false)
+            ?? throw new NotFoundException(TaskEntityName, taskId);
 
         DiscoveryTaskPatch normalized = NormalizeTaskPatch(patch);
         if (normalized.PlanJoins is int newPlan)
@@ -131,38 +135,34 @@ public sealed class DiscoveryTasksService(IDiscoveryStore store, DiscoveryPlanGu
         }
 
         await store.PatchTaskAsync(taskId, normalized, ct).ConfigureAwait(false);
-        return await store.GetTaskAsync(taskId, ct).ConfigureAwait(false);
+        return await store.GetTaskAsync(taskId, ct).ConfigureAwait(false)
+            ?? throw new NotFoundException(TaskEntityName, taskId);
     }
 
     /// <summary>
     /// Удаляет задачу вместе с кандидатами и логом.
     /// </summary>
     /// <param name="taskId">Id задачи (<c>dt_...</c>).</param>
-    /// <returns>True — задача удалена; false — строки нет (404 у эндпоинта).</returns>
-    public async Task<bool> DeleteAsync(string taskId, CancellationToken ct)
+    /// <exception cref="NotFoundException">Задача не найдена.</exception>
+    public async Task DeleteAsync(string taskId, CancellationToken ct)
     {
-        DiscoveryTaskDto? current = await store.GetTaskAsync(taskId, ct).ConfigureAwait(false);
-        if (current is null)
-        {
-            return false;
-        }
+        DiscoveryTaskDto current = await store.GetTaskAsync(taskId, ct).ConfigureAwait(false)
+            ?? throw new NotFoundException(TaskEntityName, taskId);
 
-        return await store.DeleteTaskAsync(taskId, ct).ConfigureAwait(false);
+        await store.DeleteTaskAsync(current.Id, ct).ConfigureAwait(false);
     }
 
     /// <summary>
     /// Запускает поиск
     /// </summary>
     /// <param name="taskId">Id задачи (<c>dt_...</c>).</param>
-    /// <returns>Задача в running либо null (404).</returns>
+    /// <returns>Задача в running.</returns>
+    /// <exception cref="NotFoundException">Задача не найдена.</exception>
     /// <exception cref="DiscoveryValidationException">Ключевых слов нет.</exception>
-    public async Task<DiscoveryTaskDto?> StartAsync(string taskId, CancellationToken ct)
+    public async Task<DiscoveryTaskDto> StartAsync(string taskId, CancellationToken ct)
     {
-        DiscoveryTaskDto? current = await store.GetTaskAsync(taskId, ct).ConfigureAwait(false);
-        if (current is null)
-        {
-            return null;
-        }
+        DiscoveryTaskDto current = await store.GetTaskAsync(taskId, ct).ConfigureAwait(false)
+            ?? throw new NotFoundException(TaskEntityName, taskId);
 
         if (current.Keywords.Count == 0)
         {
@@ -171,24 +171,24 @@ public sealed class DiscoveryTasksService(IDiscoveryStore store, DiscoveryPlanGu
 
         bool resetProgress = DiscoveryTaskStatuses.IsFinished(current.Status);
         await store.SetTaskRunningAsync(taskId, resetProgress, ct).ConfigureAwait(false);
-        return await store.GetTaskAsync(taskId, ct).ConfigureAwait(false);
+        return await store.GetTaskAsync(taskId, ct).ConfigureAwait(false)
+            ?? throw new NotFoundException(TaskEntityName, taskId);
     }
 
     /// <summary>
     /// Ставит задачу на паузу.
     /// </summary>
     /// <param name="taskId">Id задачи (<c>dt_...</c>).</param>
-    /// <returns>Задача в paused либо null (404).</returns>
-    public async Task<DiscoveryTaskDto?> PauseAsync(string taskId, CancellationToken ct)
+    /// <returns>Задача в paused.</returns>
+    /// <exception cref="NotFoundException">Задача не найдена.</exception>
+    public async Task<DiscoveryTaskDto> PauseAsync(string taskId, CancellationToken ct)
     {
-        DiscoveryTaskDto? current = await store.GetTaskAsync(taskId, ct).ConfigureAwait(false);
-        if (current is null)
-        {
-            return null;
-        }
+        DiscoveryTaskDto current = await store.GetTaskAsync(taskId, ct).ConfigureAwait(false)
+            ?? throw new NotFoundException(TaskEntityName, taskId);
 
-        await store.SetTaskPausedAsync(taskId, ct).ConfigureAwait(false);
-        return await store.GetTaskAsync(taskId, ct).ConfigureAwait(false);
+        await store.SetTaskPausedAsync(current.Id, ct).ConfigureAwait(false);
+        return await store.GetTaskAsync(taskId, ct).ConfigureAwait(false)
+            ?? throw new NotFoundException(TaskEntityName, taskId);
     }
 
     /// <summary>
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/Deal.SharedKernel/Errors/DealErrorCodes.cs b/src/core/Deal.SharedKernel/Errors/DealErrorCodes.cs
new file mode 100644
index 0000000..85b73ba
--- /dev/null
+++ b/src/core/Deal.SharedKernel/Errors/DealErrorCodes.cs
@@ -0,0 +1,32 @@
+namespace Deal.SharedKernel.Errors;
+
+/// <summary>
+/// Коды ошибок Deal для логов и ответов клиенту.
+/// </summary>
+public static class DealErrorCodes
+{
+    /// <summary>
+    /// Запрошенный объект не найден.
+    /// </summary>
+    public const string NotFound = "not_found";
+
+    /// <summary>
+    /// Некорректные данные запроса.
+    /// </summary>
+    public const string Validation = "validation_error";
+
+    /// <summary>
+    /// Конфликт состояния.
+    /// </summary>
+    public const string Conflict = "conflict";
+
+    /// <summary>
+    /// Внешний сервис недоступен.
+    /// </summary>
+    public const string Unavailable = "unavailable";
+
+    /// <summary>
+    /// Непредвиденная внутренняя ошибка.
+    /// </summary>
+    public const string Internal = "internal_error";
+}
diff --git a/src/core/Deal.SharedKernel/Errors/DealException.cs b/src/core/Deal.SharedKernel/Errors/DealException.cs
new file mode 100644
index 0000000..3716abf
--- /dev/null
+++ b/src/core/Deal.SharedKernel/Errors/DealException.cs
@@ -0,0 +1,35 @@
+using Deal.SharedKernel.Resources;
+
+namespace Deal.SharedKernel.Errors;
+
+/// <summary>
+/// База доменных исключений Deal: код ошибки и текст из ресурсов.
+/// </summary>
+public abstract class DealException : Exception
+{
+    protected DealException(
+        string errorCode,
+        string messageKey,
+        params object?[] messageArgs)
+        : base(ErrorResources.Format(messageKey, messageArgs))
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(errorCode);
+        ErrorCode = errorCode;
+    }
+
+    protected DealException(
+        string errorCode,
+        Exception innerException,
+        string messageKey,
+        params object?[] messageArgs)
+        : base(ErrorResources.Format(messageKey, messageArgs), innerException)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(errorCode);
+        ErrorCode = errorCode;
+    }
+
+    /// <summary>
+    /// Код ошибки для логов и ответов клиенту.
+    /// </summary>
+    public string ErrorCode { get; }
+}
diff --git a/src/core/Deal.SharedKernel/Errors/NotFoundException.cs b/src/core/Deal.SharedKernel/Errors/NotFoundException.cs
new file mode 100644
index 0000000..d784335
--- /dev/null
+++ b/src/core/Deal.SharedKernel/Errors/NotFoundException.cs
@@ -0,0 +1,19 @@
+using Deal.SharedKernel.Resources;
+
+namespace Deal.SharedKernel.Errors;
+
+/// <summary>
+/// Запрошенный объект не найден.
+/// </summary>
+public sealed class NotFoundException : DealException
+{
+    public NotFoundException(string entityName)
+        : base(DealErrorCodes.NotFound, ErrorResourceKeys.NotFoundEntity, entityName)
+    {
+    }
+
+    public NotFoundException(string entityName, string entityId)
+        : base(DealErrorCodes.NotFound, ErrorResourceKeys.NotFoundEntityWithId, entityName, entityId)
+    {
+    }
+}
diff --git a/src/core/Deal.SharedKernel/Errors/ServiceUnavailableException.cs b/src/core/Deal.SharedKernel/Errors/ServiceUnavailableException.cs
new file mode 100644
index 0000000..97b3284
--- /dev/null
+++ b/src/core/Deal.SharedKernel/Errors/ServiceUnavailableException.cs
@@ -0,0 +1,19 @@
+using Deal.SharedKernel.Resources;
+
+namespace Deal.SharedKernel.Errors;
+
+/// <summary>
+/// Внешний сервис недоступен.
+/// </summary>
+public sealed class ServiceUnavailableException : DealException
+{
+    public ServiceUnavailableException(string serviceName)
+        : base(DealErrorCodes.Unavailable, ErrorResourceKeys.ServiceUnavailable, serviceName)
+    {
+    }
+
+    public ServiceUnavailableException(string serviceName, Exception innerException)
+        : base(DealErrorCodes.Unavailable, innerException, ErrorResourceKeys.ServiceUnavailable, serviceName)
+    {
+    }
+}
diff --git a/src/core/Deal.SharedKernel/Errors/ValidationException.cs b/src/core/Deal.SharedKernel/Errors/ValidationException.cs
new file mode 100644
index 0000000..375677b
--- /dev/null
+++ b/src/core/Deal.SharedKernel/Errors/ValidationException.cs
@@ -0,0 +1,14 @@
+using Deal.SharedKernel.Resources;
+
+namespace Deal.SharedKernel.Errors;
+
+/// <summary>
+/// Некорректные данные запроса.
+/// </summary>
+public sealed class ValidationException : DealException
+{
+    public ValidationException(string messageKey, params object?[] messageArgs)
+        : base(DealErrorCodes.Validation, messageKey, messageArgs)
+    {
+    }
+}
diff --git a/src/core/Deal.SharedKernel/Resources/ErrorMessages.resx b/src/core/Deal.SharedKernel/Resources/ErrorMessages.resx
new file mode 100644
index 0000000..225eed2
--- /dev/null
+++ b/src/core/Deal.SharedKernel/Resources/ErrorMessages.resx
@@ -0,0 +1,33 @@
+<?xml version="1.0" encoding="utf-8"?>
+<root>
+  <resheader name="resmimetype">
+    <value>text/microsoft-resx</value>
+  </resheader>
+  <resheader name="version">
+    <value>2.0</value>
+  </resheader>
+  <resheader name="reader">
+    <value>System.Resources.ResXResourceReader, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <resheader name="writer">
+    <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
+  </resheader>
+  <data name="UnexpectedError" xml:space="preserve">
+    <value>Внутренняя ошибка сервиса. Обратитесь в поддержку.</value>
+  </data>
+  <data name="NotFoundEntity" xml:space="preserve">
+    <value>Объект не найден: {0}.</value>
+  </data>
+  <data name="NotFoundEntityWithId" xml:space="preserve">
+    <value>Объект не найден: {0} (id: {1}).</value>
+  </data>
+  <data name="ValidationFailed" xml:space="preserve">
+    <value>Некорректные данные запроса: {0}.</value>
+  </data>
+  <data name="ConflictState" xml:space="preserve">
+    <value>Конфликт состояния: {0}.</value>
+  </data>
+  <data name="ServiceUnavailable" xml:space="preserve">
+    <value>Сервис «{0}» временно недоступен.</value>
+  </data>
+</root>
diff --git a/src/core/Deal.SharedKernel/Resources/ErrorResourceKeys.cs b/src/core/Deal.SharedKernel/Resources/ErrorResourceKeys.cs
new file mode 100644
index 0000000..258c3fa
--- /dev/null
+++ b/src/core/Deal.SharedKernel/Resources/ErrorResourceKeys.cs
@@ -0,0 +1,37 @@
+namespace Deal.SharedKernel.Resources;
+
+/// <summary>
+/// Ключи текстов ошибок Deal в ресурсах ErrorMessages.resx.
+/// </summary>
+public static class ErrorResourceKeys
+{
+    /// <summary>
+    /// Общая непредвиденная внутренняя ошибка.
+    /// </summary>
+    public const string UnexpectedError = "UnexpectedError";
+
+    /// <summary>
+    /// Объект не найден (без идентификатора).
+    /// </summary>
+    public const string NotFoundEntity = "NotFoundEntity";
+
+    /// <summary>
+    /// Объект не найден (с идентификатором).
+    /// </summary>
+    public const string NotFoundEntityWithId = "NotFoundEntityWithId";
+
+    /// <summary>
+    /// Некорректные данные запроса.
+    /// </summary>
+    public const string ValidationFailed = "ValidationFailed";
+
+    /// <summary>
+    /// Конфликт состояния.
+    /// </summary>
+    public const string ConflictState = "ConflictState";
+
+    /// <summary>
+    /// Внешний сервис недоступен.
+    /// </summary>
+    public const string ServiceUnavailable = "ServiceUnavailable";
+}
diff --git a/src/core/Deal.SharedKernel/Resources/ErrorResources.cs b/src/core/Deal.SharedKernel/Resources/ErrorResources.cs
new file mode 100644
index 0000000..0713550
--- /dev/null
+++ b/src/core/Deal.SharedKernel/Resources/ErrorResources.cs
@@ -0,0 +1,34 @@
+using System.Globalization;
+using System.Resources;
+
+namespace Deal.SharedKernel.Resources;
+
+/// <summary>
+/// Тексты ошибок Deal из ресурсов ErrorMessages.resx.
+/// </summary>
+public static class ErrorResources
+{
+    private const string ResourceBaseName = "Deal.SharedKernel.Resources.ErrorMessages";
+
+    private static readonly ResourceManager Manager = new(ResourceBaseName, typeof(ErrorResources).Assembly);
+
+    /// <summary>
+    /// Форматированный текст по ключу ресурса с подстановкой аргументов.
+    /// </summary>
+    /// <param name="key">Ключ ресурса (см. <see cref="ErrorResourceKeys"/>).</param>
+    /// <param name="args">Аргументы шаблона.</param>
+    /// <returns>Текст ресурса; неизвестный ключ возвращается как есть.</returns>
+    public static string Format(string key, params object?[] args)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(key);
+        string? template = Manager.GetString(key, CultureInfo.CurrentUICulture);
+        if (string.IsNullOrEmpty(template))
+        {
+            return key;
+        }
+
+        return args.Length == 0
+            ? template
+            : string.Format(CultureInfo.CurrentUICulture, template, args);
+    }
+}
diff --git a/src/core/tests/Deal.Tests.Unit/Api/DealExceptionHandlerTests.cs b/src/core/tests/Deal.Tests.Unit/Api/DealExceptionHandlerTests.cs
new file mode 100644
index 0000000..48ec43a
--- /dev/null
+++ b/src/core/tests/Deal.Tests.Unit/Api/DealExceptionHandlerTests.cs
@@ -0,0 +1,83 @@
+using System.Text.Json;
+using Deal.Api.Middleware;
+using Deal.SharedKernel.Errors;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Logging;
+using NSubstitute;
+
+namespace Deal.Tests.Unit.Api;
+
+/// <summary>
+/// Тесты обработчика необработанных исключений HTTP.
+/// </summary>
+public sealed class DealExceptionHandlerTests
+{
+    [Fact]
+    public async Task NotFound_MapsTo404WithCodeAndRussianDetail()
+    {
+        DefaultHttpContext context = CreateContext();
+        DealExceptionHandler handler = new(Substitute.For<ILogger<DealExceptionHandler>>());
+
+        bool handled = await handler.TryHandleAsync(
+            context,
+            new NotFoundException("Карточка", "c_1"),
+            CancellationToken.None);
+
+        Assert.True(handled);
+        Assert.Equal(StatusCodes.Status404NotFound, context.Response.StatusCode);
+        (string detail, string code) = await ReadBodyAsync(context);
+        Assert.Equal(DealErrorCodes.NotFound, code);
+        Assert.Contains("Карточка", detail);
+    }
+
+    [Fact]
+    public async Task Unavailable_MapsTo503()
+    {
+        DefaultHttpContext context = CreateContext();
+        DealExceptionHandler handler = new(Substitute.For<ILogger<DealExceptionHandler>>());
+
+        await handler.TryHandleAsync(
+            context,
+            new ServiceUnavailableException("ИИ"),
+            CancellationToken.None);
+
+        Assert.Equal(StatusCodes.Status503ServiceUnavailable, context.Response.StatusCode);
+    }
+
+    [Fact]
+    public async Task UnexpectedException_MapsToGeneric500WithoutStackOrDetails()
+    {
+        DefaultHttpContext context = CreateContext();
+        DealExceptionHandler handler = new(Substitute.For<ILogger<DealExceptionHandler>>());
+
+        bool handled = await handler.TryHandleAsync(
+            context,
+            new InvalidOperationException("секретная внутренняя деталь"),
+            CancellationToken.None);
+
+        Assert.True(handled);
+        Assert.Equal(StatusCodes.Status500InternalServerError, context.Response.StatusCode);
+        (string detail, string code) = await ReadBodyAsync(context);
+        Assert.Equal(DealErrorCodes.Internal, code);
+        Assert.DoesNotContain("секретная внутренняя деталь", detail);
+        Assert.DoesNotContain("at ", detail);
+    }
+
+    private static DefaultHttpContext CreateContext()
+    {
+        var context = new DefaultHttpContext();
+        context.Response.Body = new MemoryStream();
+        return context;
+    }
+
+    private static async Task<(string Detail, string Code)> ReadBodyAsync(HttpContext context)
+    {
+        context.Response.Body.Seek(0, SeekOrigin.Begin);
+        using var reader = new StreamReader(context.Response.Body);
+        string json = await reader.ReadToEndAsync();
+        using JsonDocument document = JsonDocument.Parse(json);
+        return (
+            document.RootElement.GetProperty("detail").GetString() ?? string.Empty,
+            document.RootElement.GetProperty("code").GetString() ?? string.Empty);
+    }
+}
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/Modules/Discovery/DiscoveryTasksServiceTests.cs b/src/core/tests/Deal.Tests.Unit/Modules/Discovery/DiscoveryTasksServiceTests.cs
index d00bd44..d6ff143 100644
--- a/src/core/tests/Deal.Tests.Unit/Modules/Discovery/DiscoveryTasksServiceTests.cs
+++ b/src/core/tests/Deal.Tests.Unit/Modules/Discovery/DiscoveryTasksServiceTests.cs
@@ -1,8 +1,9 @@
 using Deal.Modules.Discovery.Application.Exceptions;
 using Deal.Modules.Discovery.Application.Models;
-using Deal.Tests.Unit.Support;
 using Deal.Modules.Discovery.Application.Services;
+using Deal.SharedKernel.Errors;
 using Deal.Tests.Unit.Modules.Settings;
+using Deal.Tests.Unit.Support;
 
 namespace Deal.Tests.Unit.Modules.Discovery;
 
@@ -131,14 +132,13 @@ public sealed class DiscoveryTasksServiceTests
     }
 
     [Fact]
-    public async Task Patch_MissingTask_ReturnsNull()
+    public async Task Patch_MissingTask_ThrowsNotFound()
     {
         (DiscoveryTasksService service, _, _) = Create();
 
-        DiscoveryTaskDto? patched = await service.PatchAsync(
-            "dt_missing", new DiscoveryTaskPatch { Name = "Новое" }, CancellationToken.None);
-
-        Assert.Null(patched);
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.PatchAsync(
+                "dt_missing", new DiscoveryTaskPatch { Name = "Новое" }, CancellationToken.None));
     }
 
     [Fact]
@@ -201,13 +201,12 @@ public sealed class DiscoveryTasksServiceTests
     }
 
     [Fact]
-    public async Task Start_MissingTask_ReturnsNull()
+    public async Task Start_MissingTask_ThrowsNotFound()
     {
         (DiscoveryTasksService service, _, _) = Create();
 
-        DiscoveryTaskDto? task = await service.StartAsync("dt_missing", CancellationToken.None);
-
-        Assert.Null(task);
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.StartAsync("dt_missing", CancellationToken.None));
     }
 
     [Fact]
@@ -281,9 +280,8 @@ public sealed class DiscoveryTasksServiceTests
         store.SeedCandidate(Candidate("c_2", "dt_2"));
         await store.Store.UpsertBlacklistAsync("c_1", "Источник", "причина", CancellationToken.None);
 
-        bool deleted = await service.DeleteAsync("dt_1", CancellationToken.None);
+        await service.DeleteAsync("dt_1", CancellationToken.None);
 
-        Assert.True(deleted);
         Assert.Single(store.Tasks); // dt_2 осталась
         Assert.Equal("dt_2", Assert.Single(store.Tasks).Id);
         Assert.Single(store.Candidates); // кандидат dt_2 остался
@@ -292,13 +290,12 @@ public sealed class DiscoveryTasksServiceTests
     }
 
     [Fact]
-    public async Task Delete_MissingTask_ReturnsFalse()
+    public async Task Delete_MissingTask_ThrowsNotFound()
     {
         (DiscoveryTasksService service, _, _) = Create();
 
-        bool deleted = await service.DeleteAsync("dt_missing", CancellationToken.None);
-
-        Assert.False(deleted);
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.DeleteAsync("dt_missing", CancellationToken.None));
     }
 
     [Fact]
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]
diff --git a/src/core/tests/Deal.Tests.Unit/Support/ErrorResourcesTests.cs b/src/core/tests/Deal.Tests.Unit/Support/ErrorResourcesTests.cs
new file mode 100644
index 0000000..afeb132
--- /dev/null
+++ b/src/core/tests/Deal.Tests.Unit/Support/ErrorResourcesTests.cs
@@ -0,0 +1,34 @@
+using Deal.SharedKernel.Resources;
+
+namespace Deal.Tests.Unit.Support;
+
+/// <summary>
+/// Тесты ресурсов текстов ошибок (ErrorMessages.resx).
+/// </summary>
+public sealed class ErrorResourcesTests
+{
+    [Fact]
+    public void Format_KnownKey_ReturnsRussianText()
+    {
+        string text = ErrorResources.Format(ErrorResourceKeys.UnexpectedError);
+
+        Assert.Contains("Внутренняя ошибка", text);
+    }
+
+    [Fact]
+    public void Format_TemplateWithArgs_SubstitutesPlaceholders()
+    {
+        string text = ErrorResources.Format(ErrorResourceKeys.NotFoundEntityWithId, "Карточка", "c_1");
+
+        Assert.Contains("Карточка", text);
+        Assert.Contains("c_1", text);
+    }
+
+    [Fact]
+    public void Format_UnknownKey_ReturnsKey()
+    {
+        string text = ErrorResources.Format("NoSuchKey");
+
+        Assert.Equal("NoSuchKey", text);
+    }
+}
diff --git a/src/grpc-hosting/Deal.Grpc.Hosting/Deal.Grpc.Hosting.csproj b/src/grpc-hosting/Deal.Grpc.Hosting/Deal.Grpc.Hosting.csproj
index 2bf63ff..eb8e068 100644
--- a/src/grpc-hosting/Deal.Grpc.Hosting/Deal.Grpc.Hosting.csproj
+++ b/src/grpc-hosting/Deal.Grpc.Hosting/Deal.Grpc.Hosting.csproj
@@ -30,6 +30,11 @@
     <FrameworkReference Include="Microsoft.AspNetCore.App" />
   </ItemGroup>
 
+  <ItemGroup>
+    <!-- Общие доменные исключения и тексты ошибок (Deal.SharedKernel.Errors/Resources). -->
+    <ProjectReference Include="..\..\core\Deal.SharedKernel\Deal.SharedKernel.csproj" />
+  </ItemGroup>
+
   <ItemGroup>
     <!-- gRPC-сервер ASP.NET Core (Interceptor/AddGrpc) и стандартный gRPC-health (Ruling 12). -->
     <PackageReference Include="Grpc.AspNetCore" Version="2.83.0" />
diff --git a/src/grpc-hosting/Deal.Grpc.Hosting/Interceptors/RpcCallLoggingInterceptor.cs b/src/grpc-hosting/Deal.Grpc.Hosting/Interceptors/RpcCallLoggingInterceptor.cs
index a7902a5..ed0804e 100644
--- a/src/grpc-hosting/Deal.Grpc.Hosting/Interceptors/RpcCallLoggingInterceptor.cs
+++ b/src/grpc-hosting/Deal.Grpc.Hosting/Interceptors/RpcCallLoggingInterceptor.cs
@@ -2,6 +2,8 @@ using System.Diagnostics;
 using Deal.Grpc.Hosting.Models;
 using Deal.Grpc.Hosting.Options;
 using Deal.Grpc.Hosting.Services;
+using Deal.SharedKernel.Errors;
+using Deal.SharedKernel.Resources;
 using Grpc.Core;
 using Grpc.Core.Interceptors;
 using Microsoft.Extensions.Logging;
@@ -16,9 +18,6 @@ public sealed class RpcCallLoggingInterceptor : Interceptor
     // Префикс методов стандартного gRPC-health — не логируется (инфраструктурный liveness).
     private const string HealthMethodPrefix = "/grpc.health.v1.Health/";
 
-    // Деталь RpcException для сбоя реализации (фиксированный текст; детали ошибки не наружу).
-    private const string UnknownFailureDetail = "Внутренняя ошибка сервиса";
-
     private readonly ILogger<RpcCallLoggingInterceptor> _logger;
 
     /// <summary>
@@ -101,14 +100,46 @@ public sealed class RpcCallLoggingInterceptor : Interceptor
         }
         catch (Exception exception)
         {
-            // «Прочие» сбои реализации gRPC показал бы клиенту как UNKNOWN мимо access-лога: логируем
-            // строку со статусом Unknown, пишем детали сбоя и переводим в RpcException (текст фиксирован).
-            _logger.LogError(exception, "gRPC {RpcMethod}: необработанный сбой реализации", context.Method);
-            LogCall(context, startedAt, StatusCode.Unknown);
-            throw new RpcException(new Status(StatusCode.Unknown, UnknownFailureDetail));
+            RpcException mapped = MapFailure(exception, context.Method);
+            LogCall(context, startedAt, mapped.Status.StatusCode);
+            throw mapped;
         }
     }
 
+    // Переводит сбой реализации в RpcException: доменные ошибки — по коду, прочие — Unknown
+    // с фиксированным текстом (детали и стектрейс остаются только в логе).
+    // exception: Сбой обработчика.
+    // rpcMethod: Полное имя RPC-метода (для лога).
+    // Возвращает: RpcException для клиента.
+    private RpcException MapFailure(Exception exception, string rpcMethod)
+    {
+        if (exception is DealException dealException)
+        {
+            _logger.LogWarning(
+                "gRPC {RpcMethod}: доменная ошибка {ErrorCode}: {Message}",
+                rpcMethod,
+                dealException.ErrorCode,
+                dealException.Message);
+            return new RpcException(new Status(MapErrorCode(dealException.ErrorCode), dealException.Message));
+        }
+
+        _logger.LogError(exception, "gRPC {RpcMethod}: необработанный сбой реализации", rpcMethod);
+        return new RpcException(
+            new Status(StatusCode.Unknown, ErrorResources.Format(ErrorResourceKeys.UnexpectedError)));
+    }
+
+    // Код ошибки Deal → статус gRPC.
+    // errorCode: Код из DealException.ErrorCode.
+    // Возвращает: Статус gRPC для клиента.
+    private static StatusCode MapErrorCode(string errorCode) => errorCode switch
+    {
+        DealErrorCodes.NotFound => StatusCode.NotFound,
+        DealErrorCodes.Validation => StatusCode.InvalidArgument,
+        DealErrorCodes.Conflict => StatusCode.FailedPrecondition,
+        DealErrorCodes.Unavailable => StatusCode.Unavailable,
+        _ => StatusCode.Internal,
+    };
+
     // Обёртка для handler-ов, возвращающих Task (server-streaming/дуплексный).
     // context: Контекст вызова (метод — context.Method).
     // invoke: Вызов нижестоящего обработчика.