diff --git a/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java b/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
index 3e3f1b4b..a69a77e0 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
@@ -29,7 +29,6 @@ import org.raddatz.familienarchiv.ocr.TrainingLabel;
 import org.raddatz.familienarchiv.person.Person;
 import org.raddatz.familienarchiv.tag.Tag;
 import org.raddatz.familienarchiv.document.DocumentRepository;
-import org.springframework.context.annotation.Lazy;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.PageRequest;
 import org.springframework.data.domain.Pageable;
@@ -77,10 +76,6 @@ public class DocumentService {
     private final AuditService auditService;
     private final TranscriptionBlockQueryService transcriptionBlockQueryService;
     private final AuditLogQueryService auditLogQueryService;
-    // @Lazy breaks the DocumentService ↔ ThumbnailAsyncRunner cycle: the runner
-    // now reaches Document data through DocumentService (per the layering rule),
-    // and Spring needs a proxy here to defer the back-edge until both beans exist.
-    @Lazy
     private final ThumbnailAsyncRunner thumbnailAsyncRunner;
 
     public record StoreResult(Document document, boolean isNew) {}
diff --git a/backend/src/main/java/org/raddatz/familienarchiv/document/ThumbnailAsyncRunner.java b/backend/src/main/java/org/raddatz/familienarchiv/document/ThumbnailAsyncRunner.java
index ed239ade..3b82aff1 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/document/ThumbnailAsyncRunner.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/document/ThumbnailAsyncRunner.java
@@ -28,7 +28,7 @@ import java.util.concurrent.TimeoutException;
 @Slf4j
 public class ThumbnailAsyncRunner {
 
-    private final DocumentService documentService;
+    private final DocumentRepository documentRepository;
     private final ThumbnailService thumbnailService;
 
     /** Per-document timeout for the whole generate() call — defense against corrupt PDFs. */
@@ -59,7 +59,7 @@ public class ThumbnailAsyncRunner {
      */
     @Async("thumbnailExecutor")
     public void generateAsync(UUID documentId) {
-        Optional<Document> docOpt = documentService.findById(documentId);
+        Optional<Document> docOpt = documentRepository.findById(documentId);
         if (docOpt.isEmpty()) {
             log.warn("Thumbnail generation skipped: document not found id={}", documentId);
             return;
diff --git a/backend/src/main/java/org/raddatz/familienarchiv/document/ThumbnailService.java b/backend/src/main/java/org/raddatz/familienarchiv/document/ThumbnailService.java
index b937a126..26b9e67e 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/document/ThumbnailService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/document/ThumbnailService.java
@@ -62,16 +62,16 @@ public class ThumbnailService {
 
     private final FileService fileService;
     private final S3Client s3Client;
-    private final DocumentService documentService;
+    private final DocumentRepository documentRepository;
 
     @Value("${app.s3.bucket}")
     private String bucketName;
 
     public ThumbnailService(FileService fileService, S3Client s3Client,
-                            DocumentService documentService) {
+                            DocumentRepository documentRepository) {
         this.fileService = fileService;
         this.s3Client = s3Client;
-        this.documentService = documentService;
+        this.documentRepository = documentRepository;
     }
 
     public Outcome generate(Document doc) {
@@ -167,7 +167,7 @@ public class ThumbnailService {
             doc.setThumbnailGeneratedAt(LocalDateTime.now());
             doc.setThumbnailAspect(result.aspect());
             doc.setPageCount(result.pageCount());
-            documentService.updateThumbnailMetadata(doc);
+            documentRepository.save(doc);
             return Outcome.SUCCESS;
         } catch (Exception e) {
             // Thumbnail is already in S3 but the entity update failed. Because the S3
diff --git a/backend/src/test/java/org/raddatz/familienarchiv/document/ThumbnailServiceTest.java b/backend/src/test/java/org/raddatz/familienarchiv/document/ThumbnailServiceTest.java
index 97611274..55f140bf 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/document/ThumbnailServiceTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/document/ThumbnailServiceTest.java
@@ -39,17 +39,17 @@ class ThumbnailServiceTest {
 
     private FileService fileService;
     private S3Client s3Client;
-    private DocumentService documentService;
+    private DocumentRepository documentRepository;
     private ThumbnailService thumbnailService;
 
     @BeforeEach
     void setUp() {
         fileService = mock(FileService.class);
         s3Client = mock(S3Client.class);
-        documentService = mock(DocumentService.class);
-        thumbnailService = new ThumbnailService(fileService, s3Client, documentService);
+        documentRepository = mock(DocumentRepository.class);
+        thumbnailService = new ThumbnailService(fileService, s3Client, documentRepository);
         ReflectionTestUtils.setField(thumbnailService, "bucketName", "test-bucket");
-        when(documentService.updateThumbnailMetadata(any(Document.class))).thenAnswer(i -> i.getArgument(0));
+        when(documentRepository.save(any(Document.class))).thenAnswer(i -> i.getArgument(0));
     }
 
     @Test
@@ -103,7 +103,7 @@ class ThumbnailServiceTest {
 
         assertThat(doc.getThumbnailKey()).isEqualTo("thumbnails/" + doc.getId() + ".jpg");
         assertThat(doc.getThumbnailGeneratedAt()).isNotNull();
-        verify(documentService).updateThumbnailMetadata(doc);
+        verify(documentRepository).save(doc);
     }
 
     @Test
@@ -152,7 +152,7 @@ class ThumbnailServiceTest {
 
         assertThat(outcome).isEqualTo(ThumbnailService.Outcome.FAILED);
         assertThat(doc.getThumbnailKey()).isNull();
-        verify(documentService, never()).updateThumbnailMetadata(any());
+        verify(documentRepository, never()).save(any());
     }
 
     @Test
@@ -165,7 +165,7 @@ class ThumbnailServiceTest {
 
         assertThat(outcome).isEqualTo(ThumbnailService.Outcome.FAILED);
         verifyNoInteractions(s3Client);
-        verify(documentService, never()).updateThumbnailMetadata(any());
+        verify(documentRepository, never()).save(any());
     }
 
     @Test
@@ -260,7 +260,7 @@ class ThumbnailServiceTest {
 
         assertThat(outcome).isEqualTo(ThumbnailService.Outcome.FAILED);
         verifyNoInteractions(s3Client);
-        verify(documentService, never()).updateThumbnailMetadata(any());
+        verify(documentRepository, never()).save(any());
     }
 
     @Test
@@ -275,7 +275,7 @@ class ThumbnailServiceTest {
 
         assertThat(outcome).isEqualTo(ThumbnailService.Outcome.FAILED);
         verifyNoInteractions(s3Client);
-        verify(documentService, never()).updateThumbnailMetadata(any());
+        verify(documentRepository, never()).save(any());
     }
 
     @Test
@@ -286,14 +286,14 @@ class ThumbnailServiceTest {
         Document doc = makeDoc("application/pdf", "documents/letter.pdf");
         when(fileService.downloadFileStream(anyString()))
                 .thenReturn(new ByteArrayInputStream(createSamplePdf()));
-        when(documentService.updateThumbnailMetadata(any()))
+        when(documentRepository.save(any()))
                 .thenThrow(new RuntimeException("constraint violation"));
 
         ThumbnailService.Outcome outcome = thumbnailService.generate(doc);
 
         assertThat(outcome).isEqualTo(ThumbnailService.Outcome.FAILED);
         verify(s3Client).putObject(any(PutObjectRequest.class), any(RequestBody.class));
-        verify(documentService).updateThumbnailMetadata(any());
+        verify(documentRepository).save(any());
     }
 
     // ─── helpers ──────────────────────────────────────────────────────────────