diff --git a/cbreader/settings/base.py b/cbreader/settings/base.py
index 3e7b018..4113a49 100644
--- a/cbreader/settings/base.py
+++ b/cbreader/settings/base.py
@@ -37,12 +37,10 @@ INSTALLED_APPS = [
     "django.contrib.staticfiles",
     'drf_yasg',
     'webpack_loader',
-    'bootstrap4',
     "comic",
     'django_extensions',
     'imagekit',
     'django_boost',
-    'sri',
     "corsheaders",
     'django_filters',
     'rest_framework',
@@ -264,6 +262,15 @@ SIMPLE_JWT = {
 # cbreader/urls.py matches the dot separately. See cbreader/urls.py.
 SWAGGER_USE_COMPAT_RENDERERS = False
 
+# Folder scans run through comic.tasks.scan_directory. The immediate backend runs the task
+# in the caller, which is enough today; swapping to a queue backend later changes only
+# this block, not the call sites.
+TASKS = {
+    'default': {
+        'BACKEND': os.getenv('TASK_BACKEND', 'django.tasks.backends.immediate.ImmediateBackend'),
+    },
+}
+
 FRONTEND_DIR = os.path.join(BASE_DIR, 'frontend')
 
 TEMPLATES = [
diff --git a/comic/management/commands/scan_comics.py b/comic/management/commands/scan_comics.py
index d926dd7..f9e433a 100644
--- a/comic/management/commands/scan_comics.py
+++ b/comic/management/commands/scan_comics.py
@@ -1,11 +1,11 @@
+from pathlib import Path
 
-from django.contrib.auth import get_user_model
-from django.contrib.auth.base_user import AbstractBaseUser
+from django.conf import settings
 from django.core.management.base import BaseCommand, CommandParser
 from loguru import logger
 
 from comic.models import Directory
-from comic.processing import generate_directory
+from comic.processing import reconcile
 
 
 class Command(BaseCommand):
@@ -26,14 +26,12 @@ class Command(BaseCommand):
         self.OUTPUT = options.get('out', False)
         self.scan_directory()
 
-    def scan_directory(self, user: AbstractBaseUser | None = None, directory: Directory | None = None) -> None:
-        if not user:
-            user_model = get_user_model()
-            user = user_model.objects.first()
-        if not user:
-            logger.error("No user found, cannot scan comics.")
-            return
-        for item in generate_directory(user, directory):
-            if isinstance(item, Directory):
-                logger.info(item)
-                self.scan_directory(user, item)
+    def scan_directory(self, directory: Directory | None = None) -> None:
+        reconcile(directory)
+        path = Path(settings.COMIC_BOOK_VOLUME, directory.path) if directory else settings.COMIC_BOOK_VOLUME
+        if self.OUTPUT:
+            self.stdout.write(str(path))
+        else:
+            logger.info(path)
+        for child in Directory.objects.filter(parent=directory):
+            self.scan_directory(child)
diff --git a/comic/migrations/0051_directory_one_directory_name_per_parent.py b/comic/migrations/0051_directory_one_directory_name_per_parent.py
new file mode 100644
index 0000000..b3608fa
--- /dev/null
+++ b/comic/migrations/0051_directory_one_directory_name_per_parent.py
@@ -0,0 +1,38 @@
+# Generated by Django 6.1.2 on 2026-10-13 12:51
+
+from collections import defaultdict
+
+from django.db import migrations, models
+
+
+def merge_duplicate_directories(apps, schema_editor) -> None:
+    """Scans could insert the same directory twice, so fold duplicates together
+    before the unique constraint is added, otherwise the migration fails on data
+    the bug has already created."""
+    Directory = apps.get_model('comic', 'Directory')
+    ComicBook = apps.get_model('comic', 'ComicBook')
+
+    groups = defaultdict(list)
+    for directory in Directory.objects.order_by('id'):
+        groups[(directory.parent_id, directory.name)].append(directory)
+
+    for group in groups.values():
+        keeper = group[0]
+        for duplicate in group[1:]:
+            ComicBook.objects.filter(directory=duplicate).update(directory=keeper)
+            duplicate.delete()
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('comic', '0050_delete_comicpage'),
+    ]
+
+    operations = [
+        migrations.RunPython(merge_duplicate_directories, migrations.RunPython.noop),
+        migrations.AddConstraint(
+            model_name='directory',
+            constraint=models.UniqueConstraint(fields=('parent', 'name'), name='one_directory_name_per_parent'),
+        ),
+    ]
diff --git a/comic/models.py b/comic/models.py
index 02d2b97..d085d86 100644
--- a/comic/models.py
+++ b/comic/models.py
@@ -50,6 +50,9 @@ class Directory(models.Model):
 
     class Meta:
         ordering = ['name']
+        constraints = [
+            models.UniqueConstraint(fields=['parent', 'name'], name='one_directory_name_per_parent'),
+        ]
 
     def __str__(self) -> str:
 
diff --git a/comic/processing.py b/comic/processing.py
index 4581b36..9e848a5 100644
--- a/comic/processing.py
+++ b/comic/processing.py
@@ -1,9 +1,10 @@
-from itertools import chain
+from collections.abc import Iterable
 from pathlib import Path
 
 from django.conf import settings
 from django.contrib.auth.base_user import AbstractBaseUser
 from django.db.models import (
+    BooleanField,
     Case,
     Count,
     ExpressionWrapper,
@@ -12,44 +13,47 @@ from django.db.models import (
     PositiveSmallIntegerField,
     Q,
     QuerySet,
+    Value,
     When,
 )
+from django.db.models.functions import Coalesce
 
 from comic import models
 from comic.archives import get_archive_files
 from comic.errors import NotCompatibleArchive
 
 
-def generate_directory(user: AbstractBaseUser, directory: models.Directory | None = None) \
-        -> list[models.Directory | models.ComicBook]:
+def reconcile(directory: models.Directory | None = None) -> None:
+    """Bring the database in line with the filesystem for one directory.
+
+    This is the only place the scan writes, so it runs from the scan task and the
+    management command - never from a browse request.
+    """
     dir_path = Path(settings.COMIC_BOOK_VOLUME, directory.path) if directory else settings.COMIC_BOOK_VOLUME
-    files = []
 
-    dir_db_query = models.Directory.objects.filter(parent=directory)
-    clean_directories(dir_db_query, dir_path, directory)
+    clean_directories(models.Directory.objects.filter(parent=directory), dir_path, directory)
+    clean_files(models.ComicBook.objects.filter(directory=directory), dir_path, directory)
+    clean_thumbnails(models.Directory.objects.filter(parent=directory))
+    clean_thumbnails(models.ComicBook.objects.filter(directory=directory))
 
-    file_db_query = models.ComicBook.objects.filter(directory=directory)
-    clean_files(file_db_query, user, dir_path, directory)
 
-    dir_db_query = dir_db_query.annotate(
+def list_directory(user: AbstractBaseUser, directory: models.Directory | None = None) \
+        -> list[models.Directory | models.ComicBook]:
+    """Return the contents of one directory for one user, reading only."""
+    dir_db_query = models.Directory.objects.filter(parent=directory).annotate(
         total=Count('comicbook', distinct=True),
         progress=Count('comicbook__comicstatus', Q(comicbook__comicstatus__finished=True,
                                                    comicbook__comicstatus__user=user), distinct=True),
         finished=ExpressionWrapper(Q(total=F('progress')), output_field=IntegerField()),
         unread=ExpressionWrapper(Q(total__gt=F('progress')), output_field=IntegerField()),
     )
-    files.extend(dir_db_query)
 
-    # Create Missing Status
-    new_status = [models.ComicStatus(comic=file, user=user) for file in
-                  file_db_query.exclude(comicstatus__in=models.ComicStatus.objects.filter(
-                      comic__in=file_db_query, user=user))]
-    models.ComicStatus.objects.bulk_create(new_status)
-
-    file_db_query = file_db_query.annotate(
-        progress=F('comicstatus__last_read_page') + 1,
-        finished=F('comicstatus__finished'),
-        unread=F('comicstatus__unread'),
+    # A book with no status for this user is simply unread, so the annotations have to
+    # stand in for the missing row instead of assuming one exists.
+    file_db_query = models.ComicBook.objects.filter(directory=directory).annotate(
+        progress=Coalesce(F('comicstatus__last_read_page') + 1, Value(0, output_field=IntegerField())),
+        finished=Coalesce(F('comicstatus__finished'), Value(False, output_field=BooleanField())),
+        unread=Coalesce(F('comicstatus__unread'), Value(True, output_field=BooleanField())),
         user=F('comicstatus__user'),
         classification=Case(
             When(directory__isnull=True, then=models.Directory.Classification.C_G),
@@ -58,12 +62,7 @@ def generate_directory(user: AbstractBaseUser, directory: models.Directory | Non
         )
     ).filter(Q(user__isnull=True) | Q(user=user.id))
 
-    files.extend(file_db_query)
-
-    for file in chain(file_db_query, dir_db_query):
-        if file.thumbnail and not Path(file.thumbnail.path).exists():
-            file.thumbnail.delete()
-            file.save()
+    files = list(dir_db_query) + list(file_db_query)
     files.sort(key=lambda x: x.title)
     files.sort(key=lambda x: x.type, reverse=True)
     return files
@@ -74,15 +73,16 @@ def clean_directories(directories: QuerySet, dir_path: Path, directory: models.D
     dir_list = {x for x in sorted(dir_path.glob('*')) if x.is_dir()}
     # Create new directories db instances
     for new_directory in dir_list - dir_db_set:
-        models.Directory(name=new_directory.name, parent=directory).save()
+        # get_or_create, not save(): another request may have inserted the same directory
+        # between the query above and this line, which would leave duplicate rows.
+        models.Directory.objects.get_or_create(name=new_directory.name, parent=directory)
 
     # Remove stale db instances
     for stale_directory in dir_db_set - dir_list:
-        models.Directory.objects.get(name=stale_directory.name, parent=directory).delete()
+        models.Directory.objects.filter(name=stale_directory.name, parent=directory).delete()
 
 
-def clean_files(files: QuerySet, user: AbstractBaseUser, dir_path: Path, directory: models.Directory | None = None) \
-        -> None:
+def clean_files(files: QuerySet, dir_path: Path, directory: models.Directory | None = None) -> None:
     file_list = {x for x in sorted(dir_path.glob('*')) if x.is_file()}
     files_db_set = {Path(dir_path, x.file_name) for x in files}
 
@@ -101,14 +101,18 @@ def clean_files(files: QuerySet, user: AbstractBaseUser, dir_path: Path, directo
                 # Unreadable/corrupt archive - index the file with no page count
                 pass
             books_to_add.append(new_book)
-    models.ComicBook.objects.bulk_create(books_to_add)
 
-    status_to_add = []
-    for book in books_to_add:
-        status_to_add.append(models.ComicStatus(user=user, comic=book))
-
-    models.ComicStatus.objects.bulk_create(status_to_add)
+    # ignore_conflicts: a concurrent scan may have indexed the same file, and
+    # (directory, file_name) is unique.
+    models.ComicBook.objects.bulk_create(books_to_add, ignore_conflicts=True)
 
     # Remove stale comic instances
     for stale_comic in files_db_set - file_list:
-        models.ComicBook.objects.get(file_name=stale_comic.name, directory=directory).delete()
+        models.ComicBook.objects.filter(file_name=stale_comic.name, directory=directory).delete()
+
+
+def clean_thumbnails(items: Iterable[models.Directory | models.ComicBook]) -> None:
+    for item in items:
+        if item.thumbnail and not Path(item.thumbnail.path).exists():
+            item.thumbnail.delete()
+            item.save()
diff --git a/comic/rest.py b/comic/rest.py
index 11d2283..428d9fe 100644
--- a/comic/rest.py
+++ b/comic/rest.py
@@ -19,8 +19,7 @@ from rest_framework.pagination import PageNumberPagination
 from rest_framework.request import Request
 from rest_framework.response import Response
 
-from comic import models
-from comic.processing import generate_directory
+from comic import models, processing, tasks
 from comic.util import generate_breadcrumbs_from_path
 
 
@@ -124,6 +123,10 @@ class BreadcrumbSerializer(serializers.Serializer):
     name = serializers.CharField()
 
 
+class ScanSerializer(serializers.Serializer):
+    selector = serializers.UUIDField(required=False, allow_null=True)
+
+
 class BrowseViewSet(viewsets.GenericViewSet):
     serializer_class = BrowseSerializer
     permission_classes = [permissions.IsAuthenticated]
@@ -133,15 +136,28 @@ class BrowseViewSet(viewsets.GenericViewSet):
         return
 
     def list(self, request: Request) -> Response:
-        serializer = self.get_serializer(generate_directory(request.user), many=True)
+        serializer = self.get_serializer(processing.list_directory(request.user), many=True)
         return Response(serializer.data)
 
     @swagger_auto_schema(responses={status.HTTP_200_OK: BrowseSerializer(many=True)})
     def retrieve(self, request: Request, selector: UUID) -> Response:
         directory = get_object_or_404(models.Directory, selector=selector)
-        serializer = self.get_serializer(generate_directory(request.user, directory), many=True)
+        serializer = self.get_serializer(processing.list_directory(request.user, directory), many=True)
         return Response(serializer.data)
 
+    @swagger_auto_schema(request_body=ScanSerializer, responses={status.HTTP_200_OK: BrowseSerializer(many=True)})
+    @action(methods=['post'], detail=False, serializer_class=ScanSerializer)
+    def scan(self, request: Request) -> Response:
+        """Read one directory from disk, then return it. Null selector means the root."""
+        serializer = self.get_serializer(data=request.data)
+        if not serializer.is_valid():
+            return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)
+        selector = serializer.validated_data.get('selector')
+        tasks.scan_directory.enqueue(str(selector) if selector else None)
+        directory = models.Directory.objects.filter(selector=selector).first() if selector else None
+        data = processing.list_directory(request.user, directory)
+        return Response(BrowseSerializer(data, many=True).data)
+
     @swagger_auto_schema(responses={status.HTTP_200_OK: BreadcrumbSerializer(many=True)})
     @action(methods=['get'], detail=True, serializer_class=BreadcrumbSerializer)
     def breadcrumbs(self, _request: Request, selector: UUID) -> Response:
@@ -264,7 +280,7 @@ class ReadViewSet(viewsets.GenericViewSet):
     @swagger_auto_schema(responses={status.HTTP_200_OK: TypeSerializer()})
     @action(methods=['get'], detail=True)
     def type(self, _request: Request, selector: UUID) -> Response:
-        book = models.ComicBook.objects.get(selector=selector)
+        book = get_object_or_404(models.ComicBook, selector=selector)
         return Response({'type': book.file_name.split('.')[-1].lower()})
 
     @swagger_auto_schema(responses={status.HTTP_200_OK: ReadPageSerializer()}, request_body=ReadPageSerializer)
diff --git a/comic/tasks.py b/comic/tasks.py
new file mode 100644
index 0000000..a2f3814
--- /dev/null
+++ b/comic/tasks.py
@@ -0,0 +1,18 @@
+"""The folder scan as a task.
+
+The default backend runs tasks immediately, so this behaves like a function call today.
+Writing it as a task is what lets the scan move to a worker later without changing any
+of the call sites in comic/rest.py or the management command.
+"""
+
+from django.tasks import task
+
+from comic import models
+from comic.processing import reconcile
+
+
+@task
+def scan_directory(selector: str | None = None) -> None:
+    """Reconcile one directory, or the root of the comic volume when no selector is given."""
+    directory = models.Directory.objects.filter(selector=selector).first() if selector else None
+    reconcile(directory)
diff --git a/comic/tests/test_api.py b/comic/tests/test_api.py
index 37606ea..e066391 100644
--- a/comic/tests/test_api.py
+++ b/comic/tests/test_api.py
@@ -1,8 +1,11 @@
 """Tests for the API behaviour of the comic viewsets."""
 
+import json
+
 import pytest
 
 from comic import models
+from comic.tests.factories import make_cbz
 
 UNKNOWN = '00000000-0000-0000-0000-000000000000'
 
@@ -25,6 +28,12 @@ def test_unknown_book_returns_404_for_an_image(client, reader_user) -> None:
     assert client.get(f'/api/read/{UNKNOWN}/image/1/').status_code == 404
 
 
+@pytest.mark.django_db
+def test_unknown_book_returns_404_for_the_type_action(client, reader_user) -> None:
+    client.force_login(reader_user)
+    assert client.get(f'/api/read/{UNKNOWN}/type/').status_code == 404
+
+
 @pytest.mark.django_db
 def test_image_requires_authentication(client, book) -> None:
     assert client.get(f'/api/read/{book.selector}/image/1/').status_code == 401
@@ -148,3 +157,47 @@ def test_directory_partial_update_rejects_an_unknown_classification(client, admi
         content_type='application/json',
     )
     assert response.status_code == 400
+
+
+@pytest.mark.django_db
+def test_browse_listing_does_not_write_to_the_database(client, reader_user, comic_volume) -> None:
+    """Listing is read only, so a browse request cannot race with the scan."""
+    client.force_login(reader_user)
+    target = comic_volume / 'Series'
+    target.mkdir()
+    make_cbz(target / 'issue.cbz', pages=2)
+
+    assert client.get('/api/browse/').status_code == 200
+    assert models.ComicBook.objects.count() == 0
+    assert models.ComicStatus.objects.count() == 0
+
+
+@pytest.mark.django_db
+def test_scan_endpoint_indexes_files_that_are_only_on_disk(client, reader_user, comic_volume) -> None:
+    client.force_login(reader_user)
+    target = comic_volume / 'Series'
+    target.mkdir()
+    make_cbz(target / 'issue.cbz', pages=2)
+
+    assert [entry['title'] for entry in client.get('/api/browse/').json()] == []
+
+    response = client.post('/api/browse/scan/', data='{}', content_type='application/json')
+    assert response.status_code == 200
+    assert [entry['title'] for entry in response.json()] == ['Series']
+
+    directory = models.Directory.objects.get(name='Series')
+    response = client.post('/api/browse/scan/',
+                           data=json.dumps({'selector': str(directory.selector)}),
+                           content_type='application/json')
+    assert response.status_code == 200
+    entries = response.json()
+    assert [entry['title'] for entry in entries] == ['issue.cbz']
+    assert entries[0]['type'] == 'ComicBook'
+    assert entries[0]['total'] == 2
+    assert entries[0]['progress'] == 0
+    assert entries[0]['unread'] is True
+
+
+@pytest.mark.django_db
+def test_scan_endpoint_requires_authentication(client) -> None:
+    assert client.post('/api/browse/scan/', data='{}', content_type='application/json').status_code == 401
diff --git a/comic/tests/test_models.py b/comic/tests/test_models.py
index 1bba3ee..3e933e9 100644
--- a/comic/tests/test_models.py
+++ b/comic/tests/test_models.py
@@ -3,6 +3,7 @@
 from pathlib import Path
 
 import pytest
+from django.db import IntegrityError
 
 from comic import models
 from comic.tests.factories import make_cbz, make_pdf
@@ -69,3 +70,13 @@ def test_classification_comparison() -> None:
         allowed_to_read=models.Directory.Classification.C_PG,
     )
     assert directory.classification > misc.allowed_to_read
+
+
+@pytest.mark.django_db
+def test_duplicate_directory_names_are_rejected() -> None:
+    """The scan depends on this constraint: without it two concurrent requests can create
+    the same directory twice and the browse listing shows it twice."""
+    parent = models.Directory.objects.create(name='Series')
+    models.Directory.objects.create(name='Volume 1', parent=parent)
+    with pytest.raises(IntegrityError):
+        models.Directory.objects.create(name='Volume 1', parent=parent)
diff --git a/comic/tests/test_processing.py b/comic/tests/test_processing.py
index 8729bc9..12a0859 100644
--- a/comic/tests/test_processing.py
+++ b/comic/tests/test_processing.py
@@ -3,7 +3,7 @@
 import pytest
 
 from comic import models
-from comic.processing import clean_directories, clean_files, generate_directory
+from comic.processing import clean_directories, clean_files, list_directory, reconcile
 from comic.tests.factories import make_cbz
 
 
@@ -27,22 +27,109 @@ def test_clean_files_ignores_unsupported_extensions(comic_volume, reader_user) -
     make_cbz(target / 'issue.cbz', pages=2)
     (target / 'notes.txt').write_text('not a comic')
 
-    clean_files(models.ComicBook.objects.filter(directory=directory), reader_user, target, directory)
+    clean_files(models.ComicBook.objects.filter(directory=directory), target, directory)
 
     books = list(models.ComicBook.objects.filter(directory=directory))
     assert [book.file_name for book in books] == ['issue.cbz']
     assert books[0].page_count == 2
-    assert models.ComicStatus.objects.filter(user=reader_user).count() == 1
 
 
 @pytest.mark.django_db
-def test_generate_directory_creates_missing_statuses(comic_volume, reader_user) -> None:
+def test_reconcile_indexes_the_directory_without_touching_the_database_on_a_second_run(
+        comic_volume, reader_user) -> None:
     directory = models.Directory.objects.create(name='Series')
     target = comic_volume / 'Series'
     target.mkdir(parents=True)
-    make_cbz(target / 'issue.cbz', pages=1)
+    make_cbz(target / 'issue.cbz', pages=2)
 
-    entries = generate_directory(reader_user, directory)
+    reconcile(directory)
+    first = list(models.ComicBook.objects.filter(directory=directory))
+    assert [book.file_name for book in first] == ['issue.cbz']
+
+    reconcile(directory)
+    assert list(models.ComicBook.objects.filter(directory=directory)) == first
+
+
+@pytest.mark.django_db
+def test_list_directory_reports_an_unread_book_without_creating_a_status(comic_volume,
+                                                                         reader_user) -> None:
+    """Listing is read only: a book nobody has opened has no ComicStatus row at all."""
+    directory = models.Directory.objects.create(name='Series')
+    target = comic_volume / 'Series'
+    target.mkdir(parents=True)
+    make_cbz(target / 'issue.cbz', pages=3)
+    reconcile(directory)
+
+    entries = list_directory(reader_user, directory)
 
     assert [entry.title for entry in entries] == ['issue.cbz']
-    assert models.ComicStatus.objects.filter(user=reader_user, comic=entries[0]).exists()
+    assert entries[0].progress == 0
+    assert entries[0].unread is True
+    assert entries[0].finished is False
+    assert models.ComicStatus.objects.count() == 0
+
+
+@pytest.mark.django_db
+def test_list_directory_shows_progress_for_a_book_that_has_been_read(comic_volume,
+                                                                     reader_user) -> None:
+    directory = models.Directory.objects.create(name='Series')
+    target = comic_volume / 'Series'
+    target.mkdir(parents=True)
+    make_cbz(target / 'issue.cbz', pages=3)
+    reconcile(directory)
+    book = models.ComicBook.objects.get(directory=directory)
+    models.ComicStatus.objects.create(user=reader_user, comic=book, last_read_page=1, unread=False)
+
+    entries = list_directory(reader_user, directory)
+
+    assert entries[0].progress == 2
+    assert entries[0].unread is False
+    assert entries[0].finished is False
+
+
+@pytest.mark.django_db
+def test_clean_files_survives_a_concurrent_scan_of_the_same_directory(comic_volume, reader_user,
+                                                                      rated_directory) -> None:
+    """Two requests can build the same 'new file' list; the second insert must not clash."""
+    target = comic_volume / rated_directory.name
+    target.mkdir(parents=True, exist_ok=True)
+    make_cbz(target / 'issue.cbz', pages=2)
+
+    stale = models.ComicBook.objects.filter(directory=rated_directory)
+    list(stale)  # force evaluation so the cached snapshot is empty
+    models.ComicBook.objects.create(file_name='issue.cbz', directory=rated_directory, page_count=2)
+
+    clean_files(stale, target, rated_directory)
+
+    assert models.ComicBook.objects.filter(directory=rated_directory).count() == 1
+
+
+@pytest.mark.django_db
+def test_clean_files_ignores_rows_another_request_already_removed(comic_volume, reader_user,
+                                                                  rated_directory) -> None:
+    target = comic_volume / rated_directory.name
+    target.mkdir(parents=True, exist_ok=True)
+    stale_book = models.ComicBook.objects.create(file_name='gone.cbz', directory=rated_directory)
+
+    stale = models.ComicBook.objects.filter(directory=rated_directory)
+    list(stale)  # cache the row, then let another request delete it
+    stale_book.delete()
+
+    clean_files(stale, target, rated_directory)
+
+    assert models.ComicBook.objects.filter(directory=rated_directory).count() == 0
+
+
+@pytest.mark.django_db
+def test_clean_directories_does_not_duplicate_rows_when_another_request_inserts_first(comic_volume,
+                                                                                     reader_user) -> None:
+    parent = models.Directory.objects.create(name='Series')
+    (comic_volume / 'Series' / 'New').mkdir(parents=True)
+
+    stale = models.Directory.objects.filter(parent=parent)
+    list(stale)  # cached snapshot is empty
+    models.Directory.objects.create(name='New', parent=parent)
+
+    clean_directories(stale, comic_volume / 'Series', parent)
+
+    assert models.Directory.objects.filter(parent=parent).count() == 1
diff --git a/comic/tests/test_scan_command.py b/comic/tests/test_scan_command.py
index d1742f1..58709ee 100644
--- a/comic/tests/test_scan_command.py
+++ b/comic/tests/test_scan_command.py
@@ -23,9 +23,11 @@ def test_scan_indexes_nested_directories(comic_volume: Path, reader_user) -> Non
 
 
 @pytest.mark.django_db
-def test_scan_without_a_user_stops_before_reading_the_volume(comic_volume: Path) -> None:
+def test_scan_runs_without_any_user(comic_volume: Path) -> None:
+    """The command no longer needs a user, because statuses are created when a book is read."""
     make_cbz(comic_volume / 'issue.cbz', pages=1)
 
     call_command('scan_comics')
 
-    assert models.ComicBook.objects.count() == 0
+    assert models.ComicBook.objects.count() == 1
+    assert models.ComicStatus.objects.count() == 0
diff --git a/comic/tests/test_tasks.py b/comic/tests/test_tasks.py
new file mode 100644
index 0000000..1a96383
--- /dev/null
+++ b/comic/tests/test_tasks.py
@@ -0,0 +1,17 @@
+"""Tests for the scan task."""
+
+import pytest
+
+from comic import models, tasks
+from comic.tests.factories import make_cbz
+
+
+@pytest.mark.django_db
+def test_scan_task_runs_through_the_task_backend(comic_volume) -> None:
+    """The immediate backend executes the task in the caller, so this is the whole path."""
+    make_cbz(comic_volume / 'issue.cbz', pages=2)
+
+    tasks.scan_directory.enqueue()
+
+    assert models.ComicBook.objects.count() == 1
+    assert models.ComicBook.objects.get().page_count == 2
diff --git a/frontend/src/components/HistoryTable.vue b/frontend/src/components/HistoryTable.vue
index a1afded..c38f810 100644
--- a/frontend/src/components/HistoryTable.vue
+++ b/frontend/src/components/HistoryTable.vue
@@ -136,6 +136,9 @@ export default {
   mounted() {
     this.updateComicList()
   },
+  beforeUnmount() {
+    clearTimeout(this.timeout)
+  },
 }
 </script>
 
diff --git a/frontend/src/components/TheComicList.vue b/frontend/src/components/TheComicList.vue
index 433e992..b7eeec8 100644
--- a/frontend/src/components/TheComicList.vue
+++ b/frontend/src/components/TheComicList.vue
@@ -11,6 +11,9 @@
           <li><a class="dropdown-item" @click="markAll('mark_unread')"><font-awesome-icon icon='book' />Mark Un-read</a></li>
           <li><a class="dropdown-item" @click="markAll('mark_read')"><font-awesome-icon icon='book-open' />Mark read</a></li>
         </ul>
+        <button type="button" class="btn btn-outline-secondary" :disabled="scanning" title="Read this folder from disk again" @click="scanFolder">
+          <font-awesome-icon icon='refresh' />{{ scanning ? 'Scanning…' : 'Scan' }}
+        </button>
       </div>
     </div>
     <div class="row row-cols-2 row-cols-sm-3 row-cols-md-4 row-cols-lg-6 row-cols-xl-auto mt-1" >
@@ -49,7 +52,8 @@ export default {
         filter_read: false,
         filter_unread: false
       },
-      loading: true
+      loading: true,
+      scanning: false
   }},
   props: {
     selector: String
@@ -68,6 +72,18 @@ export default {
       })
       .catch((error) => {console.log(error)})
     },
+    scanFolder () {
+      this.scanning = true
+      api.post('/api/browse/scan/', { selector: this.selector || null })
+        .then(response => {
+          this.comics = response.data
+          this.scanning = false
+        })
+        .catch((error) => {
+          console.log(error)
+          this.scanning = false
+        })
+    },
     markPreviousRead (selector) {
       let selectors = []
       this.comics.every((item) => {
diff --git a/frontend/src/components/TheComicReader.vue b/frontend/src/components/TheComicReader.vue
index 841d04f..226e22f 100644
--- a/frontend/src/components/TheComicReader.vue
+++ b/frontend/src/components/TheComicReader.vue
@@ -131,10 +131,11 @@ export default {
       }).then(() => {
         this.deck.slide(this.current_page)
         api.put(set_read_url, {page: this.current_page})
-        this.deck.on( 'slidechanged', (event) => {
+        this.slideChanged = (event) => {
           this.$refs.comic_box.scrollIntoView({behavior: 'smooth'})
           api.put(set_read_url, {page: event.indexh})
-        });
+        }
+        this.deck.on('slidechanged', this.slideChanged);
       })
 
       this.hammertime = new Hammer(this.$refs.comic_box, {})
@@ -153,6 +154,17 @@ export default {
   },
   beforeUnmount() {
     window.removeEventListener('keyup', this.keyPressDebounce)
+    clearTimeout(this.key_timeout)
+    if (this.deck) {
+      if (this.slideChanged) {
+        this.deck.off('slidechanged', this.slideChanged)
+      }
+      try {
+        this.deck.destroy()
+      } catch (e) {
+        console.log(e)
+      }
+    }
     try {
       this.hammertime.off('swipeleft')
       this.hammertime.off('swiperight')
diff --git a/frontend/src/components/TheRecentTable.vue b/frontend/src/components/TheRecentTable.vue
index 75de16d..e65f038 100644
--- a/frontend/src/components/TheRecentTable.vue
+++ b/frontend/src/components/TheRecentTable.vue
@@ -175,6 +175,9 @@ export default {
       this.feed_id = response.data.feed_id
     })
   },
+  beforeUnmount() {
+    clearTimeout(this.timeout)
+  },
 }
 </script>
 
diff --git a/frontend/src/main.js b/frontend/src/main.js
index b18b6a0..bd829d6 100644
--- a/frontend/src/main.js
+++ b/frontend/src/main.js
@@ -15,8 +15,8 @@ import { library } from '@fortawesome/fontawesome-svg-core'
 import { FontAwesomeIcon } from '@fortawesome/vue-fontawesome'
 
 /* import specific icons */
-import {faBook, faBookOpen, faEdit, faTurnUp, faTimes, faCheck} from '@fortawesome/free-solid-svg-icons'
-library.add(faBook, faBookOpen, faEdit, faTurnUp, faTimes, faCheck)
+import {faBook, faBookOpen, faEdit, faTurnUp, faTimes, faCheck, faRefresh} from '@fortawesome/free-solid-svg-icons'
+library.add(faBook, faBookOpen, faEdit, faTurnUp, faTimes, faCheck, faRefresh)
 
 import router from './router'
 import store from './store'
diff --git a/frontend/src/views/ReadView.vue b/frontend/src/views/ReadView.vue
index dcfd7dd..47fcb6b 100644
--- a/frontend/src/views/ReadView.vue
+++ b/frontend/src/views/ReadView.vue
@@ -15,25 +15,20 @@ export default {
   },
   data () {
     return {
-      comic_data: {},
       comic_loaded: false,
     }
   },
   methods: {
-    updateType() {
-      let comic_data_url = '/api/read/' + this.selector + '/type/'
-      api.get(comic_data_url)
-          .then(response => {
+    checkComicExists() {
+      api.get('/api/read/' + this.selector + '/type/')
+          .then(() => {
               this.comic_loaded = true
           })
           .catch((error) => {console.log(error)})
       }
   },
   mounted () {
-    this.updateType()
-  },
-  beforeUpdate() {
-    this.updateType()
+    this.checkComicExists()
   }
 }
 </script>