diff --git a/src/core/Deal.Api/Endpoints/MlEndpoints.cs b/src/core/Deal.Api/Endpoints/MlEndpoints.cs
index 64a4a4d..b7d816a 100644
--- a/src/core/Deal.Api/Endpoints/MlEndpoints.cs
+++ b/src/core/Deal.Api/Endpoints/MlEndpoints.cs
@@ -37,8 +37,6 @@ public static class MlEndpoints
 
     private const string EnterTextDetail = "Введите текст";
 
-    private const string MessageNotFoundDetail = "Исходное сообщение не найдено";
-
     /// <summary>
     /// Регистрирует группу /api/ml
     /// </summary>
@@ -141,12 +139,7 @@ public static class MlEndpoints
         }
 
         MlReviewService review = context.RequestServices.GetRequiredService<MlReviewService>();
-        MlApplyResult? result = await review.ApplyAsync(body.DialogId, body.MsgId, body.Action, ct);
-        if (result is null)
-        {
-            return EndpointResults.NotFound(MessageNotFoundDetail);
-        }
-
+        MlApplyResult result = await review.ApplyAsync(body.DialogId, body.MsgId, body.Action, ct);
         if (result.Error is not null)
         {
             return EndpointResults.BadRequest(result.Error);
diff --git a/src/core/Deal.Api/Endpoints/PipelineEndpoints.cs b/src/core/Deal.Api/Endpoints/PipelineEndpoints.cs
index f7ea7cb..24166af 100644
--- a/src/core/Deal.Api/Endpoints/PipelineEndpoints.cs
+++ b/src/core/Deal.Api/Endpoints/PipelineEndpoints.cs
@@ -33,8 +33,6 @@ public static class PipelineEndpoints
     // Путь возврата записи отсева в обработку (POST).
     private const string RejectedReturnPath = "/rejected/{rejId}/return";
 
-    private const string RejectedNotFoundDetail = "Запись не найдена";
-
     private const int DefaultPageSize = 100;
 
     /// <summary>
@@ -140,11 +138,7 @@ public static class PipelineEndpoints
         }
 
         PipelineProcessingService processing = context.RequestServices.GetRequiredService<PipelineProcessingService>();
-        RejectReturnResultDto? result = await processing.ReturnAsync(rejId, body.Reason ?? string.Empty, ct);
-        if (result is null)
-        {
-            return EndpointResults.NotFound(RejectedNotFoundDetail);
-        }
+        RejectReturnResultDto result = await processing.ReturnAsync(rejId, body.Reason ?? string.Empty, ct);
 
         return result.Error is not null
             ? EndpointResults.BadRequest(result.Error)
diff --git a/src/core/Deal.Modules.Pipeline/Application/Services/MlReviewService.cs b/src/core/Deal.Modules.Pipeline/Application/Services/MlReviewService.cs
index 2fabdbf..14c2426 100644
--- a/src/core/Deal.Modules.Pipeline/Application/Services/MlReviewService.cs
+++ b/src/core/Deal.Modules.Pipeline/Application/Services/MlReviewService.cs
@@ -8,6 +8,7 @@ using Deal.Modules.Kanban.Application.Models;
 using Deal.Modules.Kanban.Application.Services;
 using Deal.Modules.Pipeline.Application.Abstractions;
 using Deal.Modules.Pipeline.Application.Models;
+using Deal.SharedKernel.Errors;
 
 namespace Deal.Modules.Pipeline.Application.Services;
 
@@ -34,6 +35,9 @@ public sealed class MlReviewService(
     // Размер одного чтения из очереди/отсева при объединении кандидатов.
     private const int MaxScan = 500;
 
+    // Имя сущности для текста ошибки «не найдено».
+    private const string MessageEntityName = "Исходное сообщение";
+
     private const int TextPreviewLength = 600;
 
     /// <summary>
@@ -157,8 +161,9 @@ public sealed class MlReviewService(
     /// <param name="dialogId">Оригинал источника (OriginRef) записи.</param>
     /// <param name="msgId">Внешний id записи в источнике.</param>
     /// <param name="action">Действие: <c>skip</c> | <c>spam</c> | <c>board:&lt;id&gt;</c>.</param>
-    /// <returns>Результат решения; null — исходная запись не найдена (404-семантика эндпоинта).</returns>
-    public async Task<MlApplyResult?> ApplyAsync(
+    /// <returns>Результат решения.</returns>
+    /// <exception cref="NotFoundException">Исходная запись не найдена.</exception>
+    public async Task<MlApplyResult> ApplyAsync(
         string dialogId,
         long msgId,
         string? action,
@@ -168,17 +173,14 @@ public sealed class MlReviewService(
         string dialog = (dialogId ?? string.Empty).Trim();
         string externalId = msgId.ToString(CultureInfo.InvariantCulture);
 
-        SourceRef? source = await ResolveSourceAsync(dialog, externalId, ct);
-        if (source is null)
-        {
-            return null; // 404: исходная запись не найдена
-        }
+        SourceRef source = await ResolveSourceAsync(dialog, externalId, ct)
+            ?? throw new NotFoundException(MessageEntityName, externalId);
 
         CardDto? card = await cardStore.GetCardBySourceAsync(source, ct);
         string? text = await FindTextAsync(dialog, externalId, card, ct);
         if (string.IsNullOrWhiteSpace(text))
         {
-            return null; // 404: исходная запись не найдена
+            throw new NotFoundException(MessageEntityName, externalId);
         }
 
         if (normalized == ActionSkip)
diff --git a/src/core/Deal.Modules.Pipeline/Application/Services/PipelineProcessingService.cs b/src/core/Deal.Modules.Pipeline/Application/Services/PipelineProcessingService.cs
index d845dd0..2a79770 100644
--- a/src/core/Deal.Modules.Pipeline/Application/Services/PipelineProcessingService.cs
+++ b/src/core/Deal.Modules.Pipeline/Application/Services/PipelineProcessingService.cs
@@ -4,6 +4,7 @@ using Deal.Modules.Cards.Application.Sources;
 using Deal.Modules.Pipeline.Application.Abstractions;
 using Deal.Modules.Pipeline.Application.Models;
 using Deal.Modules.Pipeline.Application.Parse;
+using Deal.SharedKernel.Errors;
 
 namespace Deal.Modules.Pipeline.Application.Services;
 
@@ -48,6 +49,9 @@ public sealed class PipelineProcessingService(
 
     private const string DuplicateSource = "dup";
 
+    // Имя сущности для текста ошибки «не найдено».
+    private const string RejectedEntityName = "Запись отсева";
+
     private static readonly HashSet<string> SpamStages = new(StringComparer.Ordinal)
     {
         "spam_ml",
@@ -154,17 +158,15 @@ public sealed class PipelineProcessingService(
     /// </summary>
     /// <param name="rejectedId">Id записи отсева (<c>r_...</c>).</param>
     /// <param name="reason">Причина возврата (trim, ≤500; пишется на запись для аудита).</param>
-    /// <returns>null — записи нет (404); иначе результат: Error (400) либо {id, returned:true, returnedAt}.</returns>
-    public async Task<RejectReturnResultDto?> ReturnAsync(
+    /// <returns>Результат: Error (400) либо {id, returned:true, returnedAt}.</returns>
+    /// <exception cref="NotFoundException">Запись отсева не найдена.</exception>
+    public async Task<RejectReturnResultDto> ReturnAsync(
         string rejectedId,
         string reason,
         CancellationToken ct)
     {
-        RejectedItemDto? row = await store.GetAsync(rejectedId, ct);
-        if (row is null)
-        {
-            return null;
-        }
+        RejectedItemDto row = await store.GetAsync(rejectedId, ct)
+            ?? throw new NotFoundException(RejectedEntityName, rejectedId);
 
         if (row.Returned)
         {
diff --git a/src/core/tests/Deal.Tests.Unit/Modules/Kanban/MlReviewServiceTests.cs b/src/core/tests/Deal.Tests.Unit/Modules/Kanban/MlReviewServiceTests.cs
index 9a2e827..9551349 100644
--- a/src/core/tests/Deal.Tests.Unit/Modules/Kanban/MlReviewServiceTests.cs
+++ b/src/core/tests/Deal.Tests.Unit/Modules/Kanban/MlReviewServiceTests.cs
@@ -4,6 +4,7 @@ using Deal.Modules.Kanban.Application.Models;
 using Deal.Modules.Kanban.Application.Services;
 using Deal.Modules.Pipeline.Application.Models;
 using Deal.Modules.Pipeline.Application.Services;
+using Deal.SharedKernel.Errors;
 using Deal.Tests.Unit.Contracts;
 using Deal.Tests.Unit.Modules.Settings;
 using Deal.Tests.Unit.Support;
@@ -241,12 +242,11 @@ public sealed class MlReviewServiceTests
     }
 
     [Fact]
-    public async Task Apply_MessageNotFound_ReturnsNull()
+    public async Task Apply_MessageNotFound_ThrowsNotFound()
     {
         MlReviewService service = Create(new TestPipelineStore(), new TestKanjStore(), new TestMlClient(), out _);
 
-        MlApplyResult? result = await service.ApplyAsync(Dialog, 999, MlReviewService.ActionSpam, CancellationToken.None);
-
-        Assert.Null(result);
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.ApplyAsync(Dialog, 999, MlReviewService.ActionSpam, CancellationToken.None));
     }
 }
diff --git a/src/core/tests/Deal.Tests.Unit/Modules/Pipeline/PipelineProcessingServiceTests.cs b/src/core/tests/Deal.Tests.Unit/Modules/Pipeline/PipelineProcessingServiceTests.cs
index 6ea34d0..6b31631 100644
--- a/src/core/tests/Deal.Tests.Unit/Modules/Pipeline/PipelineProcessingServiceTests.cs
+++ b/src/core/tests/Deal.Tests.Unit/Modules/Pipeline/PipelineProcessingServiceTests.cs
@@ -2,6 +2,7 @@ using System.Globalization;
 using Deal.Modules.Cards.Application.Sources;
 using Deal.Modules.Pipeline.Application.Models;
 using Deal.Modules.Pipeline.Application.Services;
+using Deal.SharedKernel.Errors;
 using Deal.Tests.Unit.Contracts;
 using Deal.Tests.Unit.Support;
 
@@ -165,13 +166,13 @@ public sealed class PipelineProcessingServiceTests
 
 
     [Fact]
-    public async Task ReturnAsync_RecordNotFound_ReturnsNull()
+    public async Task ReturnAsync_RecordNotFound_ThrowsNotFound()
     {
         (PipelineProcessingService service, TestPipelineStore store, TestMlClient ml) = Create();
 
-        RejectReturnResultDto? result = await service.ReturnAsync("r_missing", string.Empty, CancellationToken.None);
+        await Assert.ThrowsAsync<NotFoundException>(
+            () => service.ReturnAsync("r_missing", string.Empty, CancellationToken.None));
 
-        Assert.Null(result); // эндпоинт ответит 404 «Запись не найдена» (Ruling 10)
         Assert.Empty(store.Queue);
         Assert.Empty(ml.Pushed);
     }