diff --git a/backend/src/main/java/org/raddatz/familienarchiv/importing/MassImportService.java b/backend/src/main/java/org/raddatz/familienarchiv/importing/MassImportService.java
index 64b09294..ccd62649 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/importing/MassImportService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/importing/MassImportService.java
@@ -56,9 +56,17 @@ public class MassImportService {
 
     public enum State { IDLE, RUNNING, DONE, FAILED }
 
+    public enum SkipReason {
+        INVALID_FILENAME_PATH_TRAVERSAL,
+        INVALID_PDF_SIGNATURE,
+        FILE_READ_ERROR,
+        ALREADY_EXISTS,
+        S3_UPLOAD_FAILED
+    }
+
     public record SkippedFile(
             @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String filename,
-            @Schema(requiredMode = Schema.RequiredMode.REQUIRED) String reason
+            @Schema(requiredMode = Schema.RequiredMode.REQUIRED) SkipReason reason
     ) {}
 
     public record ImportStatus(
@@ -293,7 +301,7 @@ public class MassImportService {
             String filename = index.contains(".") ? index : index + ".pdf";
             if (!isValidImportFilename(filename)) {
                 log.warn("Skipping import row {}: filename rejected — {}", i, filename);
-                skippedFiles.add(new SkippedFile(filename, "INVALID_FILENAME_PATH_TRAVERSAL"));
+                skippedFiles.add(new SkippedFile(filename, SkipReason.INVALID_FILENAME_PATH_TRAVERSAL));
                 continue;
             }
             Optional<File> fileOnDisk = findFileRecursive(filename);
@@ -305,17 +313,17 @@ public class MassImportService {
                 try {
                     if (!isPdfMagicBytes(fileOnDisk.get())) {
                         log.warn("Überspringe {}: Datei beginnt nicht mit %PDF-Signatur", filename);
-                        skippedFiles.add(new SkippedFile(filename, "INVALID_PDF_SIGNATURE"));
+                        skippedFiles.add(new SkippedFile(filename, SkipReason.INVALID_PDF_SIGNATURE));
                         continue;
                     }
                 } catch (IOException e) {
                     log.error("Fehler beim Prüfen der Magic-Bytes für {}", filename, e);
-                    skippedFiles.add(new SkippedFile(filename, "FILE_READ_ERROR"));
+                    skippedFiles.add(new SkippedFile(filename, SkipReason.FILE_READ_ERROR));
                     continue;
                 }
             }
 
-            Optional<String> skipReason = importSingleDocument(cells, fileOnDisk, filename, index);
+            Optional<SkipReason> skipReason = importSingleDocument(cells, fileOnDisk, filename, index);
             if (skipReason.isPresent()) {
                 skippedFiles.add(new SkippedFile(filename, skipReason.get()));
             } else {
@@ -364,11 +372,11 @@ public class MassImportService {
      * @return empty Optional on success; an Optional containing the skip reason on failure/skip.
      */
     @Transactional
-    protected Optional<String> importSingleDocument(List<String> cells, Optional<File> file, String originalFilename, String index) {
+    protected Optional<SkipReason> importSingleDocument(List<String> cells, Optional<File> file, String originalFilename, String index) {
         Optional<Document> existing = documentService.findByOriginalFilename(originalFilename);
         if (existing.isPresent() && existing.get().getStatus() != DocumentStatus.PLACEHOLDER) {
             log.info("Dokument {} existiert bereits, überspringe.", originalFilename);
-            return Optional.of("ALREADY_EXISTS");
+            return Optional.of(SkipReason.ALREADY_EXISTS);
         }
 
         String archiveBox    = getCell(cells, colBox);
@@ -404,7 +412,7 @@ public class MassImportService {
                 status = DocumentStatus.UPLOADED;
             } catch (Exception e) {
                 log.error("S3 Upload Fehler für {}", file.get().getName(), e);
-                return Optional.of("S3_UPLOAD_FAILED");
+                return Optional.of(SkipReason.S3_UPLOAD_FAILED);
             }
         }
 
diff --git a/backend/src/test/java/org/raddatz/familienarchiv/importing/MassImportServiceTest.java b/backend/src/test/java/org/raddatz/familienarchiv/importing/MassImportServiceTest.java
index 0fb50a8e..575f568c 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/importing/MassImportServiceTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/importing/MassImportServiceTest.java
@@ -154,10 +154,10 @@ class MassImportServiceTest {
                 .build();
         when(documentService.findByOriginalFilename("doc001.pdf")).thenReturn(Optional.of(existing));
 
-        Optional<String> result = service.importSingleDocument(minimalCells("doc001.pdf"), Optional.empty(), "doc001.pdf", "doc001");
+        Optional<MassImportService.SkipReason> result = service.importSingleDocument(minimalCells("doc001.pdf"), Optional.empty(), "doc001.pdf", "doc001");
 
         verify(documentService, never()).save(any());
-        assertThat(result).isPresent().contains("ALREADY_EXISTS");
+        assertThat(result).isPresent().contains(MassImportService.SkipReason.ALREADY_EXISTS);
     }
 
     // ─── importSingleDocument — already-exists guard fires before file I/O ─────
@@ -179,10 +179,10 @@ class MassImportServiceTest {
         byte[] pdfHeader = {0x25, 0x50, 0x44, 0x46, 0x2D}; // %PDF-
         Files.write(physicalFile, pdfHeader);
 
-        Optional<String> result = service.importSingleDocument(
+        Optional<MassImportService.SkipReason> result = service.importSingleDocument(
                 minimalCells("present.pdf"), Optional.of(physicalFile.toFile()), "present.pdf", "present");
 
-        assertThat(result).isPresent().contains("ALREADY_EXISTS");
+        assertThat(result).isPresent().contains(MassImportService.SkipReason.ALREADY_EXISTS);
         verify(s3Client, never()).putObject(any(PutObjectRequest.class), any(RequestBody.class));
         verify(documentService, never()).save(any());
     }
@@ -204,7 +204,7 @@ class MassImportServiceTest {
         assertThat(service.getStatus().skipped()).isEqualTo(1);
         assertThat(service.getStatus().skippedFiles())
                 .extracting(MassImportService.SkippedFile::filename, MassImportService.SkippedFile::reason)
-                .containsExactly(org.assertj.core.groups.Tuple.tuple("upload_fail.pdf", "S3_UPLOAD_FAILED"));
+                .containsExactly(org.assertj.core.groups.Tuple.tuple("upload_fail.pdf", MassImportService.SkipReason.S3_UPLOAD_FAILED));
     }
 
     @Test
@@ -223,7 +223,7 @@ class MassImportServiceTest {
         assertThat(service.getStatus().skipped()).isEqualTo(1);
         assertThat(service.getStatus().skippedFiles())
                 .extracting(MassImportService.SkippedFile::reason)
-                .containsExactly("ALREADY_EXISTS");
+                .containsExactly(MassImportService.SkipReason.ALREADY_EXISTS);
     }
 
     // ─── importSingleDocument — create new document (metadata only) ───────────
@@ -283,11 +283,11 @@ class MassImportServiceTest {
         doThrow(new RuntimeException("S3 error"))
                 .when(s3Client).putObject(any(PutObjectRequest.class), any(RequestBody.class));
 
-        Optional<String> result = service.importSingleDocument(
+        Optional<MassImportService.SkipReason> result = service.importSingleDocument(
                 minimalCells("fail.pdf"), Optional.of(tempFile.toFile()), "fail.pdf", "fail");
 
         verify(documentService, never()).save(any());
-        assertThat(result).isPresent().contains("S3_UPLOAD_FAILED");
+        assertThat(result).isPresent().contains(MassImportService.SkipReason.S3_UPLOAD_FAILED);
     }
 
     // ─── importSingleDocument — sender handling ───────────────────────────────
@@ -539,7 +539,7 @@ class MassImportServiceTest {
         assertThat(result.processed()).isEqualTo(1);
         assertThat(result.skippedFiles())
                 .extracting(MassImportService.SkippedFile::reason)
-                .containsExactly("INVALID_FILENAME_PATH_TRAVERSAL");
+                .containsExactly(MassImportService.SkipReason.INVALID_FILENAME_PATH_TRAVERSAL);
     }
 
     // ─── importSingleDocument — non-blank optional fields ────────────────────
@@ -755,7 +755,7 @@ class MassImportServiceTest {
         assertThat(spyService.getStatus().skipped()).isEqualTo(1);
         assertThat(spyService.getStatus().skippedFiles())
                 .extracting(MassImportService.SkippedFile::reason)
-                .containsExactly("FILE_READ_ERROR");
+                .containsExactly(MassImportService.SkipReason.FILE_READ_ERROR);
     }
 
     // ─── readOds — XXE security regression ───────────────────────────────────