diff --git a/backend/app/utils/images.py b/backend/app/utils/images.py
index 0eafb5fdd..563bc6655 100644
--- a/backend/app/utils/images.py
+++ b/backend/app/utils/images.py
@@ -223,6 +223,13 @@ def image_util_classify_and_face_detect_images(
             # Step 1: Get classes
             classes = object_classifier.get_classes(image_path)
 
+            # None means OpenCV could not decode the file. Skip it: len(None)
+            # would raise and abort the pass, leaving every image after this
+            # one untagged and the folder stuck on "processing" forever.
+            if classes is None:
+                logger.warning(f"Skipping unreadable image: {image_path}")
+                continue
+
             # Step 2: Insert class-image pairs if classes were detected
             if len(classes) > 0:
                 # Create image-class pairs
diff --git a/backend/tests/test_tagging_pipeline.py b/backend/tests/test_tagging_pipeline.py
new file mode 100644
index 000000000..7881ed874
--- /dev/null
+++ b/backend/tests/test_tagging_pipeline.py
@@ -0,0 +1,80 @@
+"""
+One image OpenCV cannot decode used to abort the whole AI tagging pass, so
+every image queued behind it stayed untagged. These cover the skip.
+"""
+
+from unittest.mock import call, patch
+
+from app.utils.images import image_util_classify_and_face_detect_images
+
+
+def _image(image_id: str) -> dict:
+    return {"id": image_id, "path": f"/photos/{image_id}.jpg"}
+
+
+class TestClassifyAndFaceDetectImages:
+    @patch("app.utils.images.db_update_image_tagged_status")
+    @patch("app.utils.images.db_insert_image_classes_batch")
+    @patch("app.utils.images.FaceDetector")
+    @patch("app.utils.images.ObjectClassifier")
+    def test_unreadable_image_skipped_and_later_images_still_tagged(
+        self,
+        mock_classifier_cls,
+        mock_detector_cls,
+        mock_insert_classes,
+        mock_update_tagged,
+    ) -> None:
+        def get_classes(image_path):
+            # img1 is the unreadable one -- cv2.imread returns None for it, so
+            # the classifier returns None instead of a list of class ids.
+            if "img1" in image_path:
+                return None
+            # class 0 is "person", which is what sends img2 to face detection.
+            return [0, 17] if "img2" in image_path else [17]
+
+        mock_classifier_cls.return_value.get_classes.side_effect = get_classes
+        mock_detect_faces = mock_detector_cls.return_value.detect_faces
+        mock_detect_faces.return_value = {"faces_skipped": 0}
+
+        images = [_image("img0"), _image("img1"), _image("img2")]
+
+        image_util_classify_and_face_detect_images(images)
+
+        # Only the readable images are marked tagged, and the status argument
+        # matters: passing False here would leave them queued forever.
+        assert mock_update_tagged.call_args_list == [
+            call("img0", True),
+            call("img2", True),
+        ]
+
+        # Assert the pairs themselves, not just how many calls were made, so a
+        # class attached to the wrong image is caught.
+        assert mock_insert_classes.call_args_list == [
+            call([("img0", 17)]),
+            call([("img2", 0), ("img2", 17)]),
+        ]
+
+        # img1 never reaches face detection, and img2 does because it has a
+        # person in it.
+        assert mock_detect_faces.call_args_list == [
+            call("img2", "/photos/img2.jpg")
+        ]
+
+    @patch("app.utils.images.db_update_image_tagged_status")
+    @patch("app.utils.images.db_insert_image_classes_batch")
+    @patch("app.utils.images.FaceDetector")
+    @patch("app.utils.images.ObjectClassifier")
+    def test_unreadable_image_is_logged(
+        self,
+        mock_classifier_cls,
+        mock_detector_cls,
+        mock_insert_classes,
+        mock_update_tagged,
+        caplog,
+    ) -> None:
+        mock_classifier_cls.return_value.get_classes.return_value = None
+
+        image_util_classify_and_face_detect_images([_image("img1")])
+
+        assert "/photos/img1.jpg" in caplog.text
+        mock_update_tagged.assert_not_called()