diff --git a/mobile/lib/services/background_upload.service.dart b/mobile/lib/services/background_upload.service.dart
index ab091f3925..b76b9dcd61 100644
--- a/mobile/lib/services/background_upload.service.dart
+++ b/mobile/lib/services/background_upload.service.dart
@@ -394,9 +394,13 @@ class BackgroundUploadService {
     final serverEndpoint = Store.get(StoreKey.serverEndpoint);
     final url = Uri.parse('$serverEndpoint/assets').toString();
     final headers = ApiService.getRequestHeaders();
+    final deviceId = Store.get(StoreKey.deviceId);
     final (baseDirectory, directory, filename) = await Task.split(filePath: file.path);
     final fieldsMap = {
       'filename': originalFileName ?? filename,
+      // deviceAssetId/deviceId required by server v2.7.5 and below (drop in v4.0 per #27818).
+      'deviceAssetId': deviceAssetId ?? '',
+      'deviceId': deviceId,
       'fileCreatedAt': createdAt.toUtc().toIso8601String(),
       'fileModifiedAt': modifiedAt.toUtc().toIso8601String(),
       'isFavorite': isFavorite?.toString() ?? 'false',
diff --git a/mobile/lib/services/foreground_upload.service.dart b/mobile/lib/services/foreground_upload.service.dart
index 2a3ebcb62a..3f7277579f 100644
--- a/mobile/lib/services/foreground_upload.service.dart
+++ b/mobile/lib/services/foreground_upload.service.dart
@@ -5,6 +5,8 @@ import 'dart:io';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:immich_mobile/domain/models/asset/asset_metadata.model.dart';
 import 'package:immich_mobile/domain/models/asset/base_asset.model.dart';
+import 'package:immich_mobile/domain/models/store.model.dart';
+import 'package:immich_mobile/entities/store.entity.dart';
 import 'package:immich_mobile/extensions/platform_extensions.dart';
 import 'package:immich_mobile/extensions/network_capability_extensions.dart';
 import 'package:immich_mobile/extensions/translate_extensions.dart';
@@ -319,8 +321,12 @@ class ForegroundUploadService {
       }
 
       final originalFileName = entity.isLivePhoto ? p.setExtension(fileName, p.extension(file.path)) : fileName;
+      final deviceId = Store.get(StoreKey.deviceId);
 
       final fields = {
+        // deviceAssetId/deviceId required by server v2.7.5 and below (drop in v4.0 per #27818).
+        'deviceAssetId': asset.localId!,
+        'deviceId': deviceId,
         'fileCreatedAt': asset.createdAt.toUtc().toIso8601String(),
         'fileModifiedAt': asset.updatedAt.toUtc().toIso8601String(),
         'isFavorite': asset.isFavorite.toString(),
@@ -426,6 +432,9 @@ class ForegroundUploadService {
       final filename = p.basename(file.path);
 
       final fields = {
+        // deviceAssetId/deviceId required by server v2.7.5 and below (drop in v4.0 per #27818).
+        'deviceAssetId': deviceAssetId,
+        'deviceId': Store.get(StoreKey.deviceId),
         'fileCreatedAt': fileCreatedAt.toUtc().toIso8601String(),
         'fileModifiedAt': fileModifiedAt.toUtc().toIso8601String(),
         'isFavorite': 'false',