Docs: remove stale drf-writable-nested references, DRY up audit-actor update()

Final-review cleanup on refactor/remove-drf-writable-nested: several
comments/docstrings still described drf-writable-nested's removed
NestedUpdateMixin behavior in the present tense. Rewrote them to explain
the shared context-cache and delete-query-count guarantees in terms of
the current code (bulk-edit's per-field CustomFieldInstanceSerializer
construction, and _sync_custom_fields' single hard-delete query).

Also collapsed the duplicated `if custom_fields_data is not None:
self._sync_custom_fields(...)` line in DocumentSerializer.update()'s
audit-log branches into a single code path using
contextlib.nullcontext(), removing the drift risk that caused the
earlier audit-actor bug.

No behavior change.

pyproject.toml

@@ -40,7 +40,6 @@ dependencies = [
   "djangorestframework~=3.16",
   "drf-spectacular~=0.30",
   "drf-spectacular-sidecar~=2026.7.1",
-  "drf-writable-nested~=0.7.1",
   "filelock~=3.32.0",
   "flower~=2.0.1",
   "gotenberg-client~=0.14.0",

src/documents/bulk_edit.py

@@ -27,7 +27,7 @@ from documents.models import DocumentType
 from documents.models import PaperlessTask
 from documents.models import StoragePath
 from documents.models import Tag
-from documents.permissions import set_permissions_for_object
+from documents.permissions import set_permissions_for_objects
 from documents.plugins.helpers import DocumentsStatusManager
 from documents.tasks import bulk_update_documents
 from documents.tasks import consume_file
@@ -305,33 +305,49 @@ def modify_custom_fields(
         else [(field, None) for field in add_custom_fields]
     )
 
-    custom_fields = CustomField.objects.filter(
+    custom_fields_by_id: dict[int, CustomField] = {
-        id__in=[int(field) for field, _ in add_custom_fields],
+        cf.id: cf
-    ).distinct()
+        for cf in CustomField.objects.filter(
+            id__in=[int(field) for field, _ in add_custom_fields],
+        )
+    }
+    # Deferred, not `.only()`: these objects get cached onto the FK
+    # descriptor of newly-created CustomFieldInstance rows below, and
+    # downstream post_save receivers (e.g. the filename-generation signal)
+    # touch other Document fields -- `.only("pk")` would just turn that into
+    # a deferred-field reload per document, trading one N+1 for another.
+    # `content` is the one field guaranteed to be both large (full OCR text)
+    # and unused by anything this function or its receivers touch.
+    docs_by_id: dict[int, Document] = {
+        doc.id: doc
+        for doc in Document.objects.filter(id__in=affected_docs).defer("content")
+    }
     for field_id, value in add_custom_fields:
+        custom_field = custom_fields_by_id[field_id]
+        value_field = CustomFieldInstance.TYPE_TO_DATA_STORE_NAME_MAP[
+            custom_field.data_type
+        ]
         for doc_id in affected_docs:
-            defaults = {}
+            defaults = {value_field: value}
-            custom_field = custom_fields.get(id=field_id)
+            if (
-            if custom_field:
+                custom_field.data_type == CustomField.FieldDataType.DOCUMENTLINK
-                value_field = CustomFieldInstance.TYPE_TO_DATA_STORE_NAME_MAP[
+                and value
-                    custom_field.data_type
+                and doc_id in value
-                ]
+            ):
-                defaults[value_field] = value
+                # Prevent self-linking
-                if (
+                continue
-                    custom_field.data_type == CustomField.FieldDataType.DOCUMENTLINK
+            # Pass the already-resolved objects, not bare ids: this caches
-                    and value
+            # them on the FK descriptor of any newly-created instance, so a
-                    and doc_id in value
+            # later `.field`/`.document` access (e.g. auditlog's post_save
-                ):
+            # receiver calling `str(instance)`, which touches `.field.name`)
-                    # Prevent self-linking
+            # doesn't trigger its own per-instance re-fetch.
-                    continue
             CustomFieldInstance.objects.update_or_create(
-                document_id=doc_id,
+                document=docs_by_id[doc_id],
-                field_id=field_id,
+                field=custom_field,
                 defaults=defaults,
             )
             if custom_field.data_type == CustomField.FieldDataType.DOCUMENTLINK:
-                doc = Document.objects.get(id=doc_id)
+                reflect_doclinks(docs_by_id[doc_id], custom_field, value)
-                reflect_doclinks(doc, custom_field, value)
 
     # For doc link fields that are being removed, remove symmetrical links
     for doclink_being_removed_instance in CustomFieldInstance.objects.filter(
@@ -339,12 +355,10 @@ def modify_custom_fields(
         field__id__in=remove_custom_fields,
         field__data_type=CustomField.FieldDataType.DOCUMENTLINK,
         value_document_ids__isnull=False,
-    ):
+    ).select_related("field"):
         for target_doc_id in doclink_being_removed_instance.value:
             remove_doclink(
-                document=Document.objects.get(
+                document=docs_by_id[doclink_being_removed_instance.document_id],
-                    id=doclink_being_removed_instance.document.id,
-                ),
                 field=doclink_being_removed_instance.field,
                 target_doc_id=target_doc_id,
             )
@@ -430,10 +444,13 @@ def set_permissions(
     else:
         qs.update(owner=owner)
 
-    for doc in qs:
-        set_permissions_for_object(permissions=set_permissions, object=doc, merge=merge)
-
     affected_docs = list(qs.values_list("pk", flat=True))
+    set_permissions_for_objects(
+        permissions=set_permissions,
+        model=Document,
+        pks=affected_docs,
+        merge=merge,
+    )
 
     bulk_update_documents.apply_async(
         kwargs={"document_ids": affected_docs},

src/documents/data_models.py

@@ -129,7 +129,7 @@ class DocumentMetadataOverrides:
         )
         overrides.custom_fields = {
             custom_field.field.id: custom_field.value
-            for custom_field in doc.custom_fields.all()
+            for custom_field in doc.custom_fields.select_related("field").all()
         }
 
         groups_with_perms = get_groups_with_perms(

src/documents/permissions.py

@@ -173,6 +173,182 @@ def set_permissions_for_object(
                         )
 
 
+def _resolve_permissions(codenames: set[str], ctype: ContentType) -> list[Permission]:
+    """
+    Resolves `codenames` to Permission rows, raising like the single-object
+    assign_perm() this bulk path replaces does (via a `.get()` internally)
+    if any codename doesn't exist -- e.g. a client-supplied action name that
+    was never validated (BulkEditObjectsSerializer._validate_permissions
+    calls validate_set_permissions() only for its side-effecting id checks
+    and discards the filtered dict it returns, so an unrecognized action key
+    reaches this function as-is). A plain `.filter()` with no existence
+    check would otherwise silently build zero rows and no-op instead of
+    reporting the bad input.
+    """
+    permission_objs = list(
+        Permission.objects.filter(content_type=ctype, codename__in=codenames),
+    )
+    missing = codenames - {p.codename for p in permission_objs}
+    if missing:
+        raise Permission.DoesNotExist(
+            f"Permission matching query does not exist for codename(s): "
+            f"{', '.join(sorted(missing))}",
+        )
+    return permission_objs
+
+
+# Target number of permission rows to build in Python before handing them to
+# bulk_create -- keeps peak memory bounded for a large "apply to all" call,
+# independent of bulk_create's own batch_size (which only caps the size of
+# each INSERT statement, not how many row objects exist in memory at once).
+_PERMISSION_ROW_CHUNK_SIZE = 5000
+
+
+def _apply_bulk_permission_entry(
+    *,
+    perm_model: type[UserObjectPermission] | type[GroupObjectPermission],
+    identity_model: type[User] | type[Group],
+    identity_field: str,
+    ids: list[int],
+    codename: str,
+    permission_objs: list[Permission],
+    ctype: ContentType,
+    object_pks: list[str],
+    merge: bool,
+) -> None:
+    # Only the ids are needed to build permission rows (via `<field>_id=`),
+    # so avoid fetching full User/Group rows for identities that may not
+    # even end up being granted anything new.
+    add_ids = set(
+        identity_model.objects.filter(id__in=ids).values_list("id", flat=True),
+    )
+
+    if not merge:
+        existing_ids = set(
+            perm_model.objects.filter(
+                content_type=ctype,
+                object_pk__in=object_pks,
+                permission__codename=codename,
+            ).values_list(f"{identity_field}_id", flat=True),
+        )
+        remove_ids = existing_ids - add_ids
+        if remove_ids:
+            perm_model.objects.filter(
+                content_type=ctype,
+                object_pk__in=object_pks,
+                permission__codename=codename,
+                **{f"{identity_field}_id__in": remove_ids},
+            ).delete()
+
+    if not add_ids:
+        return
+
+    rows_per_pk = len(permission_objs) * len(add_ids)
+    pks_per_chunk = max(1, _PERMISSION_ROW_CHUNK_SIZE // rows_per_pk)
+    for start in range(0, len(object_pks), pks_per_chunk):
+        pk_chunk = object_pks[start : start + pks_per_chunk]
+        rows = [
+            perm_model(
+                content_type=ctype,
+                object_pk=pk,
+                permission=permission_obj,
+                **{f"{identity_field}_id": identity_id},
+            )
+            for permission_obj in permission_objs
+            for pk in pk_chunk
+            for identity_id in add_ids
+        ]
+        # ignore_conflicts skips only rows that already exist as an exact
+        # (identity, permission, object) match -- the same de-dup the
+        # underlying (user|group, permission, object_pk) unique constraint
+        # already enforces for the single-object assign_perm() this
+        # replaces, so it doesn't change what counts as "already granted".
+        # batch_size caps how many rows go into a single INSERT so a huge
+        # chunk doesn't build one enormous statement.
+        perm_model.objects.bulk_create(rows, ignore_conflicts=True, batch_size=1000)
+
+
+def set_permissions_for_objects(
+    permissions: dict,
+    model: type[Model],
+    pks: QuerySet | list,
+    *,
+    merge: bool = False,
+) -> None:
+    """
+    Bulk equivalent of set_permissions_for_object: applies the same
+    permission changes to every object identified by `pks` at once.
+
+    Takes a model + pks (rather than model instances) deliberately -- the
+    permission rows built below only ever need `pk`, `content_type`, and
+    identity ids, so callers shouldn't have to fetch full rows (with every
+    other field) just to hand them to this function.
+
+    Deliberately does not use guardian's queryset/list-aware assign_perm:
+    passing a list as the object routes to bulk_assign_perm, which skips
+    creating a direct permission row for anyone who already has the
+    permission via ANY group membership (it checks
+    ObjectPermissionChecker.has_perm, which is group-inheritance-aware) --
+    unlike the single-object assign_perm this replaces, which always
+    ensures a direct row via get_or_create regardless of group-derived
+    access. Losing that guarantee would mean a later revocation of the
+    group's grant silently strips access an admin explicitly asked to be
+    direct. Bulk-creating rows straight against the permission models
+    instead (see _apply_bulk_permission_entry) preserves the original
+    always-create-a-direct-row semantics while still batching every object
+    and every identity into one query per action, rather than one query per
+    (object, user) pair.
+    """
+    object_pks = [str(pk) for pk in pks]
+    if not object_pks:
+        return
+
+    model_name = model.__name__.lower()
+    ctype = ContentType.objects.get_for_model(model)
+
+    for action, entry in permissions.items():
+        codename = f"{action}_{model_name}"
+        implied_codenames = {codename}
+        if action == "change":
+            # change gives view too
+            implied_codenames.add(f"view_{model_name}")
+
+        # Resolved once per action (not once per users/groups branch) and
+        # shared between both below -- also where an unrecognized action
+        # name (see _resolve_permissions) is caught.
+        permission_objs = (
+            _resolve_permissions(implied_codenames, ctype)
+            if "users" in entry or "groups" in entry
+            else []
+        )
+
+        if "users" in entry:
+            _apply_bulk_permission_entry(
+                perm_model=UserObjectPermission,
+                identity_model=User,
+                identity_field="user",
+                ids=entry["users"],
+                codename=codename,
+                permission_objs=permission_objs,
+                ctype=ctype,
+                object_pks=object_pks,
+                merge=merge,
+            )
+
+        if "groups" in entry:
+            _apply_bulk_permission_entry(
+                perm_model=GroupObjectPermission,
+                identity_model=Group,
+                identity_field="group",
+                ids=entry["groups"],
+                codename=codename,
+                permission_objs=permission_objs,
+                ctype=ctype,
+                object_pks=object_pks,
+                merge=merge,
+            )
+
+
 def permitted_object_ids(
     user: User | None,
     model: type[Model],

src/documents/serialisers.py

@@ -1,8 +1,10 @@
 from __future__ import annotations
 
+import contextlib
 import logging
 import math
 import re
+from collections.abc import Iterable
 from datetime import datetime
 from datetime import timedelta
 from decimal import Decimal
@@ -24,6 +26,7 @@ from django.core.validators import MaxValueValidator
 from django.core.validators import MinValueValidator
 from django.core.validators import RegexValidator
 from django.core.validators import integer_validator
+from django.db import DataError
 from django.db.models import Count
 from django.db.models import Q
 from django.db.models.functions import Lower
@@ -37,12 +40,12 @@ from django.utils.timezone import make_aware
 from django.utils.translation import gettext as _
 from drf_spectacular.utils import extend_schema_field
 from drf_spectacular.utils import extend_schema_serializer
-from drf_writable_nested.serializers import NestedUpdateMixin
 from guardian.core import ObjectPermissionChecker
 from guardian.shortcuts import get_users_with_perms
 from guardian.utils import get_group_obj_perms_model
 from guardian.utils import get_user_obj_perms_model
 from rest_framework import fields
+from rest_framework import relations
 from rest_framework import serializers
 from rest_framework.exceptions import PermissionDenied
 from rest_framework.fields import SerializerMethodField
@@ -742,22 +745,100 @@ class TagSerializer(MatchingModelSerializer, OwnedObjectSerializer):
         return super().validate(attrs)
 
 
-class CorrespondentField(serializers.PrimaryKeyRelatedField[Correspondent]):
+class _BatchingManyRelatedField(serializers.ManyRelatedField):
+    """
+    `ManyRelatedField.to_internal_value` resolves each id in the submitted
+    list with its own `child_relation.to_internal_value()` call -- one query
+    per item on every PATCH/PUT that sets a `many=True` relation field.
+    Batch-resolve them instead, falling back to the child relation's normal
+    (query-per-item) validation for anything that isn't a plausible int pk,
+    so bad input still gets the usual DRF validation error rather than being
+    silently dropped.
+    """
+
+    @staticmethod
+    def _normalize_pk(item) -> int | None:
+        # Excludes bool: DRF's own PrimaryKeyRelatedField rejects it too
+        # (True == 1 would otherwise silently match pk 1).
+        if isinstance(item, bool):
+            return None
+        try:
+            return int(item)
+        except (TypeError, ValueError):
+            return None
+
+    def to_internal_value(self, data):
+        if isinstance(data, str) or not hasattr(data, "__iter__"):
+            self.fail("not_a_list", input_type=type(data).__name__)
+        if not self.allow_empty and len(data) == 0:
+            self.fail("empty")
+
+        item_pks = [(item, self._normalize_pk(item)) for item in data]
+        candidate_pks = {pk for _, pk in item_pks if pk is not None}
+
+        # Django's IntegerFieldOverflow guard (-> EmptyResultSet, i.e. no
+        # match) only covers exact/gt/gte/lt/lte lookups, not `in` -- an
+        # out-of-range int in `pk__in=` reaches the DB driver as-is and
+        # raises OverflowError (SQLite) / DataError (Postgres) instead of
+        # cleanly matching nothing. The per-item `exact`-lookup fallback
+        # below IS covered, so on that failure just skip the batch and let
+        # every item resolve individually -- each still costs one query,
+        # but reports the normal validation error instead of a raw 500.
+        try:
+            resolved_by_pk = {
+                obj.pk: obj
+                for obj in self.child_relation.get_queryset().filter(
+                    pk__in=candidate_pks,
+                )
+            }
+        except (OverflowError, DataError):
+            resolved_by_pk = {}
+
+        result = []
+        for item, pk in item_pks:
+            obj = resolved_by_pk.get(pk) if pk is not None else None
+            result.append(
+                obj if obj is not None else self.child_relation.to_internal_value(item),
+            )
+        return result
+
+
+class BatchResolvingPrimaryKeyRelatedField(serializers.PrimaryKeyRelatedField):
+    """
+    A PrimaryKeyRelatedField whose `many=True` form (a DRF ManyRelatedField)
+    resolves all submitted ids with one batched query instead of one query
+    per id. Subclasses only need to implement `get_queryset()` as usual --
+    only `TagsField` is used with `many=True` today, but this is the base
+    for all four so the fix isn't tag-specific: if a future PR puts
+    `many=True` on correspondent/document_type/storage_path, it inherits the
+    same batching instead of reintroducing this as a new bug to rediscover.
+    """
+
+    @classmethod
+    def many_init(cls, *args, **kwargs):
+        list_kwargs = {"child_relation": cls(*args, **kwargs)}
+        for key, value in kwargs.items():
+            if key in relations.MANY_RELATION_KWARGS:
+                list_kwargs[key] = value
+        return _BatchingManyRelatedField(**list_kwargs)
+
+
+class CorrespondentField(BatchResolvingPrimaryKeyRelatedField[Correspondent]):
     def get_queryset(self):
         return Correspondent.objects.all()
 
 
-class TagsField(serializers.PrimaryKeyRelatedField[Tag]):
+class TagsField(BatchResolvingPrimaryKeyRelatedField[Tag]):
     def get_queryset(self):
         return Tag.objects.all()
 
 
-class DocumentTypeField(serializers.PrimaryKeyRelatedField[DocumentType]):
+class DocumentTypeField(BatchResolvingPrimaryKeyRelatedField[DocumentType]):
     def get_queryset(self):
         return DocumentType.objects.all()
 
 
-class StoragePathField(serializers.PrimaryKeyRelatedField[StoragePath]):
+class StoragePathField(BatchResolvingPrimaryKeyRelatedField[StoragePath]):
     def get_queryset(self):
         return StoragePath.objects.all()
 
@@ -876,8 +957,106 @@ def validate_documentlink_targets(user, doc_ids):
         )
 
 
+# A CustomField lookup cache scoped to a single field/serializer instance
+# only helps within that one instance's own validation pass. Several call
+# sites, though, build more than one CustomFieldInstanceSerializer (or its
+# CustomFieldInstanceListSerializer/field) for the same request and pass
+# each of them `context=self.context` -- the *same* dict object, not a
+# copy -- e.g. bulk-edit's _validate_custom_field_values() constructing a
+# fresh CustomFieldInstanceSerializer per submitted field. That context
+# dict is already request-scoped (DRF builds it fresh per request via
+# get_serializer_context()), so stashing the resolved CustomField objects
+# there -- rather than in some new global/thread-local cache -- lets every
+# one of those separately-instantiated serializers reuse them for free
+# while staying entirely within DRF's existing, already-request-scoped
+# machinery.
+_CUSTOM_FIELD_CONTEXT_CACHE_KEY = "_custom_field_lookup_cache"
+
+
+class _CachingCustomFieldPrimaryKeyField(serializers.PrimaryKeyRelatedField):
+    """
+    Resolves CustomField ids with as few queries as possible: a per-instance
+    cache for repeat lookups on this exact field instance, backed by a
+    shared cache on the serializer context (see _CUSTOM_FIELD_CONTEXT_CACHE_KEY
+    above) so later, separately-instantiated fields for the same request
+    reuse what was already resolved instead of re-querying.
+    """
+
+    def __init__(self, **kwargs: Any) -> None:
+        super().__init__(**kwargs)
+        self._cache: dict[int, CustomField] = {}
+
+    def _shared_cache(self) -> dict[int, CustomField]:
+        return self.context.setdefault(_CUSTOM_FIELD_CONTEXT_CACHE_KEY, {})
+
+    @staticmethod
+    def _normalize_pk(data: Any) -> int | None:
+        """
+        Returns `data` coerced to the int a valid CustomField pk would be,
+        or None if `data` isn't a plausible pk (wrong type, unhashable,
+        non-numeric, or a bool -- DRF itself rejects bools as pks since
+        `True == 1` would otherwise silently match). None tells callers to
+        leave `data` alone and let `super().to_internal_value()` report the
+        normal validation error instead of touching the cache/queryset with
+        it directly.
+        """
+        if isinstance(data, bool):
+            return None
+        try:
+            return int(data)
+        except (TypeError, ValueError):
+            return None
+
+    def prefetch(self, ids: Iterable[Any]) -> None:
+        shared_cache = self._shared_cache()
+        candidates = {pk for i in ids if (pk := self._normalize_pk(i)) is not None}
+        missing = {
+            i for i in candidates if i not in self._cache and i not in shared_cache
+        }
+        if missing:
+            for obj in self.get_queryset().filter(pk__in=missing):
+                shared_cache[obj.pk] = obj
+        for i in candidates:
+            obj = shared_cache.get(i)
+            if obj is not None:
+                self._cache[i] = obj
+
+    def to_internal_value(self, data: Any) -> CustomField:
+        pk = self._normalize_pk(data)
+        if pk is None:
+            return super().to_internal_value(data)
+        if pk in self._cache:
+            return self._cache[pk]
+        shared_cache = self._shared_cache()
+        if pk in shared_cache:
+            obj = shared_cache[pk]
+            self._cache[pk] = obj
+            return obj
+        obj: CustomField = super().to_internal_value(data)
+        self._cache[obj.pk] = obj
+        shared_cache[obj.pk] = obj
+        return obj
+
+
+class CustomFieldInstanceListSerializer(serializers.ListSerializer):
+    def to_internal_value(self, data: Any) -> list[Any]:
+        if isinstance(data, list):
+            field_ids = []
+            for item in data:
+                if not isinstance(item, dict) or "field" not in item:
+                    continue
+                try:
+                    hash(item["field"])
+                except TypeError:
+                    continue
+                field_ids.append(item["field"])
+            if field_ids:
+                self.child.fields["field"].prefetch(field_ids)
+        return super().to_internal_value(data)
+
+
 class CustomFieldInstanceSerializer(serializers.ModelSerializer[CustomFieldInstance]):
-    field = serializers.PrimaryKeyRelatedField(queryset=CustomField.objects.all())
+    field = _CachingCustomFieldPrimaryKeyField(queryset=CustomField.objects.all())
     value = ReadWriteSerializerMethodField(allow_null=True)
 
     def create(self, validated_data):
@@ -978,6 +1157,7 @@ class CustomFieldInstanceSerializer(serializers.ModelSerializer[CustomFieldInsta
 
     class Meta:
         model = CustomFieldInstance
+        list_serializer_class = CustomFieldInstanceListSerializer
         fields = [
             "value",
             "field",
@@ -1043,7 +1223,6 @@ class DocumentVersionInfoSerializer(serializers.Serializer[_DocumentVersionInfo]
 )
 class DocumentSerializer(
     OwnedObjectSerializer,
-    NestedUpdateMixin,
     DocumentUpdateFieldsModelSerializer,
 ):
     correspondent = CorrespondentField(allow_null=True)
@@ -1258,16 +1437,60 @@ class DocumentSerializer(
                     if tag not in inbox_tags_not_being_added
                 ]
 
-        if settings.AUDIT_LOG_ENABLED:
+        custom_fields_data = validated_data.pop("custom_fields", None)
-            with set_actor(self.user):
+
-                super().update(instance, validated_data)
+        actor_context = (
-        else:
+            set_actor(self.user)
+            if settings.AUDIT_LOG_ENABLED
+            else contextlib.nullcontext()
+        )
+        with actor_context:
             super().update(instance, validated_data)
+            if custom_fields_data is not None:
+                self._sync_custom_fields(instance, custom_fields_data)
 
-        # hard delete custom field instances that were soft deleted
-        CustomFieldInstance.deleted_objects.filter(document=instance).delete()
         return instance
 
+    def _sync_custom_fields(
+        self,
+        instance: Document,
+        custom_fields_data: list[dict],
+    ) -> None:
+        """
+        Create/update a CustomFieldInstance for every (field, value) pair in
+        custom_fields_data, then hard-delete any of the document's existing
+        instances whose field wasn't included.
+
+        Replaces drf-writable-nested's generic
+        update_or_create_reverse_relations()/delete_reverse_relations_if_need():
+        that machinery always matched submitted items by an instance "id"
+        this client payload never sends, so its own pk-matching never did
+        anything for this field -- the real upsert semantics were always
+        CustomFieldInstanceSerializer.create()'s update_or_create() below.
+
+        On a partial (PATCH) update, DRF skips the "value" field's required
+        check on the first validation pass because it's absent entirely from
+        the payload item, not merely null. drf-writable-nested happened to
+        re-enforce that check itself, by re-validating each item against a
+        freshly built, non-partial child serializer before saving. Reproduce
+        that specific guarantee explicitly here, since CustomFieldInstance's
+        "value" is not optional.
+        """
+        for item in custom_fields_data:
+            if "value" not in item:
+                raise serializers.ValidationError(
+                    {"custom_fields": [{"value": ["This field is required."]}]},
+                )
+
+        kept_field_ids: set[int] = set()
+        serializer = CustomFieldInstanceSerializer()
+        for item in custom_fields_data:
+            kept_field_ids.add(item["field"].pk)
+            serializer.create({**item, "document": instance})
+        CustomFieldInstance.objects.filter(document=instance).exclude(
+            field_id__in=kept_field_ids,
+        ).hard_delete()
+
     def __init__(self, *args, **kwargs) -> None:
         self.truncate_content = kwargs.pop("truncate_content", False)
 

src/documents/tests/test_api_custom_fields.py

@@ -5,7 +5,9 @@ from unittest.mock import ANY
 
 from django.contrib.auth.models import Permission
 from django.contrib.auth.models import User
+from django.db import connection
 from django.test import override_settings
+from django.test.utils import CaptureQueriesContext
 from guardian.shortcuts import assign_perm
 from rest_framework import status
 from rest_framework.test import APITestCase
@@ -13,6 +15,9 @@ from rest_framework.test import APITestCase
 from documents.models import CustomField
 from documents.models import CustomFieldInstance
 from documents.models import Document
+from documents.serialisers import CustomFieldInstanceSerializer
+from documents.serialisers import DocumentSerializer
+from documents.tests.factories import DocumentFactory
 from documents.tests.utils import DirectoriesMixin
 
 
@@ -530,6 +535,137 @@ class TestCustomFieldsAPI(DirectoriesMixin, APITestCase):
         doc.refresh_from_db()
         self.assertEqual(len(doc.custom_fields.all()), 10)
 
+    def test_document_serializer_custom_fields_validation_batches_field_lookup(
+        self,
+    ) -> None:
+        """
+        GIVEN:
+            - A document is being validated with several custom field values
+              at once (as happens on every PATCH/PUT/POST)
+        WHEN:
+            - The serializer is validated
+        THEN:
+            - The referenced CustomField objects are resolved with a single
+              query, not one query per custom field
+        """
+        doc = DocumentFactory(mime_type="application/pdf")
+        custom_fields = [
+            CustomField.objects.create(
+                name=f"Test Custom Field {i}",
+                data_type=CustomField.FieldDataType.STRING,
+            )
+            for i in range(5)
+        ]
+
+        serializer = DocumentSerializer(
+            doc,
+            data={
+                "custom_fields": [
+                    {"field": custom_field.id, "value": "test value"}
+                    for custom_field in custom_fields
+                ],
+            },
+            partial=True,
+        )
+
+        with CaptureQueriesContext(connection) as ctx:
+            self.assertTrue(serializer.is_valid(), serializer.errors)
+
+        custom_field_lookups = [
+            query
+            for query in ctx.captured_queries
+            if 'FROM "documents_customfield" WHERE "documents_customfield"."id"'
+            in query["sql"]
+        ]
+        self.assertEqual(
+            len(custom_field_lookups),
+            1,
+            "Expected a single batched query to resolve the custom fields, "
+            f"got {len(custom_field_lookups)}: {custom_field_lookups}",
+        )
+
+    def test_custom_field_lookup_reuses_shared_context_cache(self) -> None:
+        """
+        GIVEN:
+            - A CustomField has already been resolved once, by a serializer
+              sharing a given `context` dict
+        WHEN:
+            - A second, separately-instantiated CustomFieldInstanceSerializer
+              validates the same field id, sharing that same context
+              (this mirrors what real call sites do, e.g. bulk-edit's
+              validate_custom_fields()/_validate_custom_field_values()
+              constructing a fresh CustomFieldInstanceSerializer per
+              submitted field, all sharing the outer serializer's context)
+        THEN:
+            - No additional query is issued to resolve the CustomField
+        """
+        custom_field = CustomField.objects.create(
+            name="Test Custom Field",
+            data_type=CustomField.FieldDataType.STRING,
+        )
+
+        context: dict = {}
+        first_pass = CustomFieldInstanceSerializer(
+            data={"field": custom_field.id, "value": "a"},
+            context=context,
+        )
+        self.assertTrue(first_pass.is_valid(), first_pass.errors)
+
+        second_pass = CustomFieldInstanceSerializer(
+            data={"field": custom_field.id, "value": "b"},
+            context=context,
+        )
+        with CaptureQueriesContext(connection) as ctx:
+            self.assertTrue(second_pass.is_valid(), second_pass.errors)
+
+        custom_field_lookups = [
+            query
+            for query in ctx.captured_queries
+            if 'FROM "documents_customfield" WHERE "documents_customfield"."id"'
+            in query["sql"]
+        ]
+        self.assertEqual(
+            len(custom_field_lookups),
+            0,
+            "Expected the second, separately-instantiated serializer to reuse "
+            f"the already-resolved CustomField, got: {custom_field_lookups}",
+        )
+
+    def test_custom_field_validation_rejects_malformed_field_value(self) -> None:
+        """
+        GIVEN:
+            - A document is being validated with a malformed custom_fields
+              entry whose "field" value is neither a valid CustomField id
+              nor a type DRF's own PrimaryKeyRelatedField can safely reject
+              on its own (unhashable, or a non-numeric scalar)
+        WHEN:
+            - The serializer is validated
+        THEN:
+            - A normal validation error is raised, not an unhandled
+              TypeError/ValueError escaping past DRF's validation layer
+        """
+        doc = DocumentFactory(mime_type="application/pdf")
+
+        bad_field_values = {
+            "unhashable-list": [],
+            "unhashable-dict": {},
+            "non-numeric-scalar": "abc",
+        }
+        for case_id, bad_field_value in bad_field_values.items():
+            with self.subTest(case_id):
+                serializer = DocumentSerializer(
+                    doc,
+                    data={
+                        "custom_fields": [
+                            {"field": bad_field_value, "value": "test value"},
+                        ],
+                    },
+                    partial=True,
+                )
+
+                self.assertFalse(serializer.is_valid())
+                self.assertIn("custom_fields", serializer.errors)
+
     def test_change_custom_field_instance_value(self) -> None:
         """
         GIVEN:
@@ -660,6 +796,72 @@ class TestCustomFieldsAPI(DirectoriesMixin, APITestCase):
         assert _cf_4 is not None
         self.assertEqual(_cf_4.value, date_value)
 
+    def test_delete_custom_field_instance_is_hard_deleted_not_soft_deleted(
+        self,
+    ) -> None:
+        """
+        GIVEN:
+            - A document has two custom field instances
+        WHEN:
+            - A PATCH request updates custom_fields to omit one of them
+        THEN:
+            - The omitted instance is immediately hard-deleted: it is gone
+              from both the default manager and the soft-deleted manager,
+              not left in a soft-deleted, not-yet-purged state
+        """
+        doc = Document.objects.create(
+            title="WOW",
+            content="the content",
+            checksum="123-hard-delete",
+            mime_type="application/pdf",
+        )
+        kept_field = CustomField.objects.create(
+            name="Kept Field",
+            data_type=CustomField.FieldDataType.STRING,
+        )
+        removed_field = CustomField.objects.create(
+            name="Removed Field",
+            data_type=CustomField.FieldDataType.STRING,
+        )
+
+        resp = self.client.patch(
+            f"/api/documents/{doc.id}/",
+            data={
+                "custom_fields": [
+                    {"field": kept_field.id, "value": "keep me"},
+                    {"field": removed_field.id, "value": "remove me"},
+                ],
+            },
+            format="json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+        self.assertEqual(CustomFieldInstance.objects.count(), 2)
+
+        resp = self.client.patch(
+            f"/api/documents/{doc.id}/",
+            data={
+                "custom_fields": [
+                    {"field": kept_field.id, "value": "keep me"},
+                ],
+            },
+            format="json",
+        )
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+
+        self.assertEqual(CustomFieldInstance.objects.count(), 1)
+        self.assertEqual(
+            CustomFieldInstance.deleted_objects.filter(field=removed_field).count(),
+            0,
+            "Removed custom field instance should be hard-deleted, not left "
+            "soft-deleted",
+        )
+        self.assertEqual(
+            CustomFieldInstance.global_objects.filter(field=removed_field).count(),
+            0,
+            "Removed custom field instance should not exist at all, even in "
+            "the all-rows manager",
+        )
+
     def test_custom_field_validation(self) -> None:
         """
         GIVEN:
@@ -1351,6 +1553,81 @@ class TestCustomFieldsAPI(DirectoriesMixin, APITestCase):
         results = response.data["results"]
         self.assertEqual(results[0]["document_count"], 0)
 
+    def test_document_update_custom_fields_sync_query_count(self) -> None:
+        """
+        GIVEN:
+            - A document already has 3 custom field instances attached
+        WHEN:
+            - A PATCH request updates 2 of them, adds 1 new one, and omits
+              the 3rd (which should be deleted)
+        THEN:
+            - The omitted custom field is removed via exactly one
+              delete-shaped query, not drf-writable-nested's old two-step
+              soft-delete-then-hard-delete-after pattern (two delete
+              passes)
+        """
+        doc = Document.objects.create(
+            title="WOW",
+            content="the content",
+            checksum="123-sync-count",
+            mime_type="application/pdf",
+        )
+        fields = [
+            CustomField.objects.create(
+                name=f"Sync Field {i}",
+                data_type=CustomField.FieldDataType.STRING,
+            )
+            for i in range(4)
+        ]
+        # Attach the first 3 up front; the 4th is added in the PATCH below,
+        # and the 3rd is omitted (so it should be deleted).
+        for field in fields[:3]:
+            CustomFieldInstance.objects.create(
+                document=doc,
+                field=field,
+                value_text="initial",
+            )
+        self.assertEqual(CustomFieldInstance.objects.count(), 3)
+
+        with CaptureQueriesContext(connection) as ctx:
+            resp = self.client.patch(
+                f"/api/documents/{doc.id}/",
+                data={
+                    "custom_fields": [
+                        {"field": fields[0].id, "value": "updated 0"},
+                        {"field": fields[1].id, "value": "updated 1"},
+                        {"field": fields[3].id, "value": "new 3"},
+                    ],
+                },
+                format="json",
+            )
+        self.assertEqual(resp.status_code, status.HTTP_200_OK)
+
+        delete_queries = [
+            q
+            for q in ctx.captured_queries
+            if 'DELETE FROM "documents_customfieldinstance"' in q["sql"]
+            or (
+                'UPDATE "documents_customfieldinstance"' in q["sql"]
+                and '"deleted_at"' in q["sql"]
+                and '"deleted_at" = NULL' not in q["sql"]
+            )
+        ]
+        self.assertEqual(
+            len(delete_queries),
+            1,
+            "Expected exactly one delete/soft-delete-marking query for the "
+            f"omitted custom field, got {len(delete_queries)}: {delete_queries}",
+        )
+
+        self.assertEqual(CustomFieldInstance.objects.count(), 3)
+        doc.refresh_from_db()
+        values = {cfi.field_id: cfi.value for cfi in doc.custom_fields.all()}
+        self.assertEqual(values[fields[0].id], "updated 0")
+        self.assertEqual(values[fields[1].id], "updated 1")
+        self.assertEqual(values[fields[3].id], "new 3")
+        self.assertNotIn(fields[2].id, values)
+
     def test_patch_document_invalid_date_custom_field_returns_validation_error(
         self,
     ) -> None:

src/documents/tests/test_api_documents.py

@@ -1,5 +1,6 @@
 import datetime
 import json
+import re
 import shutil
 import tempfile
 import uuid
@@ -21,7 +22,9 @@ from django.core import mail
 from django.core.cache import cache
 from django.core.files.uploadedfile import SimpleUploadedFile
 from django.db import DataError
+from django.db import connection
 from django.test import override_settings
+from django.test.utils import CaptureQueriesContext
 from django.utils import timezone
 from guardian.shortcuts import assign_perm
 from rest_framework import status
@@ -252,6 +255,82 @@ class TestDocumentApi(DirectoriesMixin, ConsumeTaskMixin, APITestCase):
         doc.refresh_from_db()
         self.assertEqual(doc.created, date(2023, 6, 28))
 
+    def test_document_update_tags_batches_tag_lookup(self) -> None:
+        """
+        GIVEN:
+            - A document is being updated with several tags at once
+        WHEN:
+            - API PATCH request is made setting the document's tags
+        THEN:
+            - The referenced Tag objects are resolved with a single batched
+              query, not one query per tag
+        """
+        doc = Document.objects.create(
+            title="none",
+            checksum="123",
+            mime_type="application/pdf",
+        )
+        tags = [TagFactory() for _ in range(8)]
+
+        with CaptureQueriesContext(connection) as ctx:
+            response = self.client.patch(
+                f"/api/documents/{doc.pk}/",
+                {"tags": [t.id for t in tags]},
+                format="json",
+            )
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+
+        # Match `"documents_tag"."id" = <literal>` (a single-row WHERE lookup)
+        # but not the same substring appearing as a JOIN's ON condition
+        # (`"documents_tag"."id" = "documents_document_tags"."tag_id"`),
+        # which is a legitimate, unrelated response-serialization query.
+        single_tag_lookup_re = re.compile(r'"documents_tag"\."id" = \d')
+        single_tag_lookups = [
+            q for q in ctx.captured_queries if single_tag_lookup_re.search(q["sql"])
+        ]
+        self.assertEqual(
+            len(single_tag_lookups),
+            0,
+            "Expected tags to be resolved with a batched query, not "
+            f"per-tag lookups, got: {single_tag_lookups}",
+        )
+
+        doc.refresh_from_db()
+        self.assertCountEqual(
+            doc.tags.values_list("id", flat=True),
+            [t.id for t in tags],
+        )
+
+    def test_document_update_tags_rejects_out_of_range_id(self) -> None:
+        """
+        GIVEN:
+            - A document is being updated with a tag id too large for the
+              database's integer column
+        WHEN:
+            - API PATCH request is made setting the document's tags
+        THEN:
+            - A normal 400 validation error is returned, not an unhandled
+              OverflowError/DataError escaping as a 500
+
+        Django's IntegerFieldOverflow guard converts an out-of-range int
+        into a clean "no match" for exact/gt/gte/lt/lte lookups, but not for
+        `in` -- the batched tag resolution uses `pk__in=`, so this has to be
+        guarded explicitly rather than relying on Django to do it.
+        """
+        doc = Document.objects.create(
+            title="none",
+            checksum="123",
+            mime_type="application/pdf",
+        )
+
+        response = self.client.patch(
+            f"/api/documents/{doc.pk}/",
+            {"tags": [99999999999999999999999999999]},
+            format="json",
+        )
+
+        self.assertEqual(response.status_code, status.HTTP_400_BAD_REQUEST)
+
     def test_document_update_legacy_created_format(self) -> None:
         """
         GIVEN:

src/documents/tests/test_api_objects.py

@@ -2,10 +2,15 @@ import datetime
 import json
 from unittest import mock
 
+from django.contrib.auth.models import Group
 from django.contrib.auth.models import Permission
 from django.contrib.auth.models import User
+from django.db import connection
 from django.test import override_settings
+from django.test.utils import CaptureQueriesContext
 from guardian.shortcuts import assign_perm
+from guardian.shortcuts import get_groups_with_perms
+from guardian.shortcuts import get_users_with_perms
 from rest_framework import status
 from rest_framework.test import APITestCase
 
@@ -815,6 +820,59 @@ class TestBulkEditObjects(APITestCase):
         self.assertEqual(response.status_code, status.HTTP_200_OK)
         self.assertEqual(StoragePath.objects.count(), 0)
 
+    def test_bulk_objects_set_permissions_query_count_independent_of_object_count(
+        self,
+    ) -> None:
+        """
+        GIVEN:
+            - Many tags are being bulk-edited to set permissions at once
+        WHEN:
+            - bulk_edit_objects API endpoint is called with set_permissions
+              operation over a small batch vs. a much larger one
+        THEN:
+            - The number of queries issued is the same either way -- each
+              user/group is applied across all tags with one batched call,
+              not one call per (tag, user) pair
+        """
+        group1 = Group.objects.create(name="perm-group")
+        permissions = {
+            "view": {"users": [self.user1.id, self.user2.id], "groups": [group1.id]},
+            "change": {"users": [self.user1.id], "groups": [group1.id]},
+        }
+
+        def run_with_n_tags(n: int) -> int:
+            tags = [Tag.objects.create(name=f"perm-tag-{n}-{i}") for i in range(n)]
+            with CaptureQueriesContext(connection) as ctx:
+                response = self.client.post(
+                    "/api/bulk_edit_objects/",
+                    json.dumps(
+                        {
+                            "objects": [t.id for t in tags],
+                            "object_type": "tags",
+                            "operation": "set_permissions",
+                            "permissions": permissions,
+                            "merge": False,
+                        },
+                    ),
+                    content_type="application/json",
+                )
+            self.assertEqual(response.status_code, status.HTTP_200_OK)
+            for tag in tags:
+                self.assertEqual(get_users_with_perms(tag).count(), 2)
+                self.assertEqual(get_groups_with_perms(tag).count(), 1)
+            return len(ctx.captured_queries)
+
+        small_batch_queries = run_with_n_tags(5)
+        large_batch_queries = run_with_n_tags(50)
+
+        self.assertEqual(
+            small_batch_queries,
+            large_batch_queries,
+            "Expected the same query count regardless of tag count, got "
+            f"{small_batch_queries} queries for 5 tags vs. "
+            f"{large_batch_queries} for 50",
+        )
+
     def test_bulk_objects_delete_all_filtered(self) -> None:
         """
         GIVEN:

src/documents/tests/test_bulk_edit.py

@@ -5,8 +5,11 @@ from unittest import mock
 
 import pikepdf
 from django.contrib.auth.models import Group
+from django.contrib.auth.models import Permission
 from django.contrib.auth.models import User
+from django.db import connection
 from django.test import TestCase
+from django.test.utils import CaptureQueriesContext
 from guardian.shortcuts import assign_perm
 from guardian.shortcuts import get_groups_with_perms
 from guardian.shortcuts import get_users_with_perms
@@ -19,6 +22,7 @@ from documents.models import Document
 from documents.models import DocumentType
 from documents.models import StoragePath
 from documents.models import Tag
+from documents.permissions import set_permissions_for_objects
 from documents.tests.utils import DirectoriesMixin
 
 
@@ -344,6 +348,100 @@ class TestBulkEdit(DirectoriesMixin, TestCase):
         assert _cf_3 is not None
         self.assertNotIn(self.doc3.id, _cf_3.value)
 
+    def test_modify_custom_fields_batches_field_lookup(self) -> None:
+        """
+        GIVEN:
+            - Several documents are being bulk-edited to add several custom
+              fields at once
+        WHEN:
+            - modify_custom_fields runs
+        THEN:
+            - Each CustomField is resolved with one batched query total, not
+              once per (field, document) pair
+        """
+        docs = [
+            Document.objects.create(checksum=f"batch-{i}", title=f"batch-{i}")
+            for i in range(6)
+        ]
+        fields = [
+            CustomField.objects.create(
+                name=f"Batch Field {i}",
+                data_type=CustomField.FieldDataType.STRING,
+            )
+            for i in range(4)
+        ]
+
+        with CaptureQueriesContext(connection) as ctx:
+            bulk_edit.modify_custom_fields(
+                [doc.id for doc in docs],
+                add_custom_fields=[field.id for field in fields],
+                remove_custom_fields=[],
+            )
+
+        field_lookups = [
+            q
+            for q in ctx.captured_queries
+            if 'FROM "documents_customfield"' in q["sql"]
+        ]
+        self.assertEqual(
+            len(field_lookups),
+            1,
+            "Expected a single batched query to resolve the custom fields, "
+            f"got {len(field_lookups)}: {field_lookups}",
+        )
+
+        for doc in docs:
+            self.assertEqual(doc.custom_fields.count(), len(fields))
+
+    def test_modify_custom_fields_batches_document_lookup_for_documentlink(
+        self,
+    ) -> None:
+        """
+        GIVEN:
+            - Several documents are being bulk-edited to add a DOCUMENTLINK
+              custom field at once
+        WHEN:
+            - modify_custom_fields runs
+        THEN:
+            - The Document rows needed to reflect the symmetrical links are
+              resolved with one batched query total, not once per document
+        """
+        docs = [
+            Document.objects.create(checksum=f"link-{i}", title=f"link-{i}")
+            for i in range(6)
+        ]
+        target = Document.objects.create(checksum="link-target", title="link-target")
+        doclink_field = CustomField.objects.create(
+            name="Related",
+            data_type=CustomField.FieldDataType.DOCUMENTLINK,
+        )
+
+        with CaptureQueriesContext(connection) as ctx:
+            bulk_edit.modify_custom_fields(
+                [doc.id for doc in docs],
+                add_custom_fields={doclink_field.id: [target.id]},
+                remove_custom_fields=[],
+            )
+
+        single_document_lookups = [
+            q
+            for q in ctx.captured_queries
+            if 'FROM "documents_document"' in q["sql"]
+            and '"documents_document"."id" = ' in q["sql"]
+        ]
+        self.assertEqual(
+            len(single_document_lookups),
+            0,
+            "Expected document rows to come from a batched query, not "
+            f"per-document lookups, got: {single_document_lookups}",
+        )
+
+        for doc in docs:
+            self.assertEqual(
+                doc.custom_fields.get(field=doclink_field).value,
+                [target.id],
+            )
+
     def test_modify_custom_fields_doclink_self_link(self) -> None:
         """
         GIVEN:
@@ -510,6 +608,132 @@ class TestBulkEdit(DirectoriesMixin, TestCase):
         )
         self.assertEqual(groups_with_perms.count(), 2)
 
+    @mock.patch("documents.tasks.bulk_update_documents.apply_async")
+    def test_set_permissions_query_count_independent_of_document_count(
+        self,
+        m,
+    ) -> None:
+        """
+        GIVEN:
+            - Many documents are being bulk-edited to set permissions at once
+        WHEN:
+            - set_permissions runs over a small batch vs. a much larger one
+        THEN:
+            - The number of queries issued is the same either way -- each
+              user/group is applied across all documents with one batched
+              call, not one call per (document, user) pair
+        """
+        permissions = {
+            "view": {
+                "users": [self.user1.id, self.user2.id],
+                "groups": [self.group2.id],
+            },
+            "change": {
+                "users": [self.user1.id],
+                "groups": [self.group2.id],
+            },
+        }
+
+        def run_with_n_documents(n: int) -> int:
+            docs = [
+                Document.objects.create(checksum=f"perm-{n}-{i}", title=f"perm-{n}-{i}")
+                for i in range(n)
+            ]
+            with CaptureQueriesContext(connection) as ctx:
+                bulk_edit.set_permissions(
+                    [doc.id for doc in docs],
+                    set_permissions=permissions,
+                    owner=self.owner,
+                    merge=False,
+                )
+            for doc in docs:
+                self.assertEqual(get_users_with_perms(doc).count(), 2)
+                self.assertEqual(get_groups_with_perms(doc).count(), 1)
+            return len(ctx.captured_queries)
+
+        small_batch_queries = run_with_n_documents(5)
+        large_batch_queries = run_with_n_documents(50)
+
+        self.assertEqual(
+            small_batch_queries,
+            large_batch_queries,
+            "Expected the same query count regardless of document count, got "
+            f"{small_batch_queries} queries for 5 documents vs. "
+            f"{large_batch_queries} for 50",
+        )
+
+    @mock.patch("documents.tasks.bulk_update_documents.apply_async")
+    def test_set_permissions_grants_direct_perm_even_if_already_granted_via_group(
+        self,
+        m,
+    ) -> None:
+        """
+        GIVEN:
+            - A user already has view access to a document via group
+              membership, with no direct grant of their own
+        WHEN:
+            - set_permissions explicitly grants that same user direct view
+              access via bulk_edit
+        THEN:
+            - A direct permission grant is created for the user, not skipped
+              because they already have equivalent access via the group
+
+        Regression test: guardian's queryset-aware assign_perm() (routed to
+        when the target is a list/queryset) skips creating a direct row for
+        anyone whose ObjectPermissionChecker.has_perm() already returns True
+        -- which includes group-derived access. The single-object assign_perm
+        this bulk path replaces has no such check; it always ensures a
+        direct row via get_or_create. Losing that guarantee would mean
+        revoking the group's grant later silently strips access that was
+        supposed to be explicit.
+        """
+        self.doc1.owner = self.user1
+        self.doc1.save()
+        self.user1.groups.add(self.group1)
+        assign_perm("view_document", self.group1, self.doc1)
+
+        bulk_edit.set_permissions(
+            [self.doc1.id],
+            set_permissions={
+                "view": {"users": [self.user1.id], "groups": []},
+            },
+            merge=True,
+        )
+
+        direct_users = get_users_with_perms(
+            self.doc1,
+            only_with_perms_in=["view_document"],
+            with_group_users=False,
+        )
+        self.assertIn(self.user1, direct_users)
+
+    def test_set_permissions_for_objects_raises_for_unknown_action(self) -> None:
+        """
+        GIVEN:
+            - An unrecognized permission action name with users to grant it
+              to
+        WHEN:
+            - set_permissions_for_objects is called
+        THEN:
+            - Permission.DoesNotExist is raised, not a silent no-op
+
+        Regression test: the endpoint that calls this
+        (BulkEditObjectPermissionsView) never actually validates action
+        names against the raw client-supplied permissions dict --
+        BulkEditObjectsSerializer._validate_permissions calls
+        validate_set_permissions() only for its side-effecting user/group id
+        checks and discards the filtered dict it returns -- so a bogus
+        action key reaches this function as-is. Resolving the Permission via
+        a bare `.filter()` (which returns empty instead of raising) would
+        silently drop the grant and report success.
+        """
+        with self.assertRaises(Permission.DoesNotExist):
+            set_permissions_for_objects(
+                {"not_a_real_action": {"users": [self.user1.id], "groups": []}},
+                Document,
+                [self.doc1.pk],
+            )
+
     @mock.patch("documents.models.Document.delete")
     def test_delete_documents_old_uuid_field(self, m) -> None:
         m.side_effect = Exception("Data too long for column 'transaction_id' at row 1")

src/documents/tests/test_data_models.py

@@ -0,0 +1,58 @@
+from django.db import connection
+from django.test import TestCase
+from django.test.utils import CaptureQueriesContext
+
+from documents.data_models import DocumentMetadataOverrides
+from documents.models import CustomField
+from documents.models import CustomFieldInstance
+from documents.tests.factories import DocumentFactory
+from documents.tests.utils import DirectoriesMixin
+
+
+class TestDocumentMetadataOverridesFromDocument(DirectoriesMixin, TestCase):
+    def test_from_document_batches_custom_field_lookup_after_refresh_from_db(
+        self,
+    ) -> None:
+        """
+        GIVEN:
+            - A document has several custom field values
+            - The document instance has just been refreshed from the database,
+              which drops any prefetched related objects (as
+              send_websocket_document_updated does before building overrides)
+        WHEN:
+            - DocumentMetadataOverrides.from_document() reads the document's
+              custom field values
+        THEN:
+            - The referenced CustomField objects are resolved with a single
+              query, not one query per custom field
+        """
+        doc = DocumentFactory(mime_type="application/pdf")
+        for i in range(5):
+            CustomFieldInstance.objects.create(
+                document=doc,
+                field=CustomField.objects.create(
+                    name=f"Test Custom Field {i}",
+                    data_type=CustomField.FieldDataType.STRING,
+                ),
+                value_text="value",
+            )
+
+        doc.refresh_from_db()
+
+        with CaptureQueriesContext(connection) as ctx:
+            overrides = DocumentMetadataOverrides.from_document(doc)
+
+        self.assertEqual(len(overrides.custom_fields), 5)
+        unbatched_field_lookups = [
+            query
+            for query in ctx.captured_queries
+            if 'FROM "documents_customfield" WHERE "documents_customfield"."id"'
+            in query["sql"]
+        ]
+        self.assertEqual(
+            unbatched_field_lookups,
+            [],
+            "Expected CustomField data to come from the CustomFieldInstance "
+            "join, not a separate per-instance lookup, "
+            f"got: {unbatched_field_lookups}",
+        )

src/documents/views.py

@@ -178,7 +178,7 @@ from documents.permissions import has_perms_owner_aware
 from documents.permissions import has_system_status_permission
 from documents.permissions import permitted_document_ids
 from documents.permissions import permitted_object_ids
-from documents.permissions import set_permissions_for_object
+from documents.permissions import set_permissions_for_objects
 from documents.plugins.date_parsing import get_date_parser
 from documents.schema import generate_object_with_permissions_schema
 from documents.search import SearchHit
@@ -4917,12 +4917,12 @@ class BulkEditObjectsView(PassUserMixin):
                     qs_owner_update.update(owner=owner)
 
                 if "permissions" in serializer.validated_data:
-                    for obj in qs:
+                    set_permissions_for_objects(
-                        set_permissions_for_object(
+                        permissions=permissions,
-                            permissions=permissions,
+                        model=object_class,
-                            object=obj,
+                        pks=qs.values_list("pk", flat=True),
-                            merge=merge,
+                        merge=merge,
-                        )
+                    )
 
             except Exception as e:
                 logger.warning(

uv.lock

@@ -4,11 +4,11 @@ requires-python = ">=3.11"
 resolution-markers = [
     "python_full_version >= '3.15' and sys_platform == 'darwin'",
     "python_full_version >= '3.15' and sys_platform == 'linux'",
+    "python_full_version == '3.14.*' and platform_machine == 'x86_64' and sys_platform == 'linux'",
+    "python_full_version == '3.14.*' and platform_machine == 'aarch64' and sys_platform == 'linux'",
     "python_full_version >= '3.12' and python_full_version < '3.15' and sys_platform == 'darwin'",
     "python_full_version == '3.12.*' and platform_machine == 'x86_64' and sys_platform == 'linux'",
     "python_full_version == '3.12.*' and platform_machine == 'aarch64' and sys_platform == 'linux'",
-    "python_full_version == '3.14.*' and platform_machine == 'x86_64' and sys_platform == 'linux'",
-    "python_full_version == '3.14.*' and platform_machine == 'aarch64' and sys_platform == 'linux'",
     "(python_full_version >= '3.12' and python_full_version < '3.15' and platform_machine != 'aarch64' and platform_machine != 'x86_64' and sys_platform == 'linux') or (python_full_version == '3.13.*' and platform_machine == 'aarch64' and sys_platform == 'linux') or (python_full_version == '3.13.*' and platform_machine == 'x86_64' and sys_platform == 'linux')",
     "python_full_version < '3.12' and sys_platform == 'darwin'",
     "python_full_version < '3.12' and sys_platform == 'linux'",
@@ -1175,14 +1175,6 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/9d/76/d08f5c79f7643dbff4512605c28b75481966ed6c8cc9b397c9dd2ee91cd1/drf_spectacular_sidecar-2026.7.1-py3-none-any.whl", hash = "sha256:bc6d50c9b64660e45e09296d39553b3e759eedd825fc41d631ee5b3f88e0c5de", size = 2617384, upload-time = "2026-07-01T13:39:03.787Z" },
 ]
 
-[[package]]
-name = "drf-writable-nested"
-version = "0.7.2"
-source = { registry = "https://pypi.org/simple" }
-wheels = [
-    { url = "https://files.pythonhosted.org/packages/e8/57/df87d92fbfc3f0f2ef1a49c47f2a83389a4a13b7acf62b8bf7b223627d82/drf_writable_nested-0.7.2-py3-none-any.whl", hash = "sha256:4a3d2737c1cbfafa690e30236b169112e5b23cfe3d288f3992b0651a1b828c4d", size = 10570, upload-time = "2025-03-10T19:59:05.482Z" },
-]
-
 [[package]]
 name = "execnet"
 version = "2.1.2"
@@ -2895,7 +2887,6 @@ dependencies = [
     { name = "djangorestframework" },
     { name = "drf-spectacular" },
     { name = "drf-spectacular-sidecar" },
-    { name = "drf-writable-nested" },
     { name = "filelock" },
     { name = "flower" },
     { name = "gotenberg-client" },
@@ -3045,7 +3036,6 @@ requires-dist = [
     { name = "djangorestframework", specifier = "~=3.16" },
     { name = "drf-spectacular", specifier = "~=0.30" },
     { name = "drf-spectacular-sidecar", specifier = "~=2026.7.1" },
-    { name = "drf-writable-nested", specifier = "~=0.7.1" },
     { name = "filelock", specifier = "~=3.32.0" },
     { name = "flower", specifier = "~=2.0.1" },
     { name = "gotenberg-client", specifier = "~=0.14.0" },
@@ -5014,10 +5004,10 @@ version = "2.13.0+cpu"
 source = { registry = "https://download.pytorch.org/whl/cpu" }
 resolution-markers = [
     "python_full_version >= '3.15' and sys_platform == 'linux'",
-    "python_full_version == '3.12.*' and platform_machine == 'x86_64' and sys_platform == 'linux'",
-    "python_full_version == '3.12.*' and platform_machine == 'aarch64' and sys_platform == 'linux'",
     "python_full_version == '3.14.*' and platform_machine == 'x86_64' and sys_platform == 'linux'",
     "python_full_version == '3.14.*' and platform_machine == 'aarch64' and sys_platform == 'linux'",
+    "python_full_version == '3.12.*' and platform_machine == 'x86_64' and sys_platform == 'linux'",
+    "python_full_version == '3.12.*' and platform_machine == 'aarch64' and sys_platform == 'linux'",
     "(python_full_version >= '3.12' and python_full_version < '3.15' and platform_machine != 'aarch64' and platform_machine != 'x86_64' and sys_platform == 'linux') or (python_full_version == '3.13.*' and platform_machine == 'aarch64' and sys_platform == 'linux') or (python_full_version == '3.13.*' and platform_machine == 'x86_64' and sys_platform == 'linux')",
     "python_full_version < '3.12' and sys_platform == 'linux'",
 ]