diff --git a/src/backend/core/api/permissions.py b/src/backend/core/api/permissions.py
index 43a0465f..09007847 100644
--- a/src/backend/core/api/permissions.py
+++ b/src/backend/core/api/permissions.py
@@ -6,6 +6,7 @@ from django.http import Http404
 
 from rest_framework import permissions
 
+from core import choices
 from core.models import DocumentAccess, RoleChoices, get_trashbin_cutoff
 
 ACTION_FOR_METHOD_TO_PERMISSION = {
@@ -96,26 +97,27 @@ class CanCreateInvitationPermission(permissions.BasePermission):
         ).exists()
 
 
-class AccessPermission(permissions.BasePermission):
-    """Permission class for access objects."""
+class ResourceWithAccessPermission(permissions.BasePermission):
+    """A permission class for templates and invitations."""
 
     def has_permission(self, request, view):
+        """check create permission for templates."""
         return request.user.is_authenticated or view.action != "create"
 
     def has_object_permission(self, request, view, obj):
         """Check permission for a given object."""
         abilities = obj.get_abilities(request.user)
         action = view.action
-        try:
-            action = ACTION_FOR_METHOD_TO_PERMISSION[view.action][request.method]
-        except KeyError:
-            pass
         return abilities.get(action, False)
 
 
-class DocumentAccessPermission(AccessPermission):
+class DocumentPermission(permissions.BasePermission):
     """Subclass to handle soft deletion specificities."""
 
+    def has_permission(self, request, view):
+        """check create permission for documents."""
+        return request.user.is_authenticated or view.action != "create"
+
     def has_object_permission(self, request, view, obj):
         """
         Return a 404 on deleted documents
@@ -127,10 +129,45 @@ class DocumentAccessPermission(AccessPermission):
         ) and deleted_at < get_trashbin_cutoff():
             raise Http404
 
-        # Compute permission first to ensure the "user_roles" attribute is set
-        has_permission = super().has_object_permission(request, view, obj)
+        abilities = obj.get_abilities(request.user)
+        action = view.action
+        try:
+            action = ACTION_FOR_METHOD_TO_PERMISSION[view.action][request.method]
+        except KeyError:
+            pass
+
+        has_permission = abilities.get(action, False)
 
         if obj.ancestors_deleted_at and not RoleChoices.OWNER in obj.user_roles:
             raise Http404
 
         return has_permission
+
+
+class ResourceAccessPermission(IsAuthenticated):
+    """Permission class for document access objects."""
+
+    def has_permission(self, request, view):
+        """check create permission for accesses in documents tree."""
+        if super().has_permission(request, view) is False:
+            return False
+
+        if view.action == "create":
+            role = getattr(view, view.resource_field_name).get_role(request.user)
+            if role not in choices.PRIVILEGED_ROLES:
+                raise exceptions.PermissionDenied(
+                    "You are not allowed to manage accesses for this resource."
+                )
+
+        return True
+
+    def has_object_permission(self, request, view, obj):
+        """Check permission for a given object."""
+        abilities = obj.get_abilities(request.user)
+
+        requested_role = request.data.get("role")
+        if requested_role and requested_role not in abilities.get("set_role_to", []):
+            return False
+
+        action = view.action
+        return abilities.get(action, False)
diff --git a/src/backend/core/api/serializers.py b/src/backend/core/api/serializers.py
index fcf2a1ea..6bd9da30 100644
--- a/src/backend/core/api/serializers.py
+++ b/src/backend/core/api/serializers.py
@@ -10,7 +10,7 @@ from django.utils.functional import lazy
 from django.utils.translation import gettext_lazy as _
 
 import magic
-from rest_framework import exceptions, serializers
+from rest_framework import serializers
 
 from core import choices, enums, models, utils
 from core.services.ai_services import AI_ACTIONS
@@ -38,78 +38,7 @@ class UserLightSerializer(UserSerializer):
         read_only_fields = ["full_name", "short_name"]
 
 
-class BaseAccessSerializer(serializers.ModelSerializer):
-    """Serialize template accesses."""
-
-    abilities = serializers.SerializerMethodField(read_only=True)
-
-    def update(self, instance, validated_data):
-        """Make "user" field is readonly but only on update."""
-        validated_data.pop("user", None)
-        return super().update(instance, validated_data)
-
-    def get_abilities(self, instance) -> dict:
-        """Return abilities of the logged-in user on the instance."""
-        request = self.context.get("request")
-        if request:
-            return instance.get_abilities(request.user)
-        return {}
-
-    def validate(self, attrs):
-        """
-        Check access rights specific to writing (create/update)
-        """
-        request = self.context.get("request")
-        user = getattr(request, "user", None)
-        role = attrs.get("role")
-
-        # Update
-        if self.instance:
-            can_set_role_to = self.instance.get_abilities(user)["set_role_to"]
-            if role and role not in can_set_role_to:
-                message = (
-                    f"You are only allowed to set role to {', '.join(can_set_role_to)}"
-                    if can_set_role_to
-                    else "You are not allowed to set this role for this template."
-                )
-                raise exceptions.PermissionDenied(message)
-
-        # Create
-        else:
-            try:
-                resource_id = self.context["resource_id"]
-            except KeyError as exc:
-                raise exceptions.ValidationError(
-                    "You must set a resource ID in kwargs to create a new access."
-                ) from exc
-
-            if not self.Meta.model.objects.filter(  # pylint: disable=no-member
-                Q(user=user) | Q(team__in=user.teams),
-                role__in=choices.PRIVILEGED_ROLES,
-                **{self.Meta.resource_field_name: resource_id},  # pylint: disable=no-member
-            ).exists():
-                raise exceptions.PermissionDenied(
-                    "You are not allowed to manage accesses for this resource."
-                )
-
-            if (
-                role == models.RoleChoices.OWNER
-                and not self.Meta.model.objects.filter(  # pylint: disable=no-member
-                    Q(user=user) | Q(team__in=user.teams),
-                    role=models.RoleChoices.OWNER,
-                    **{self.Meta.resource_field_name: resource_id},  # pylint: disable=no-member
-                ).exists()
-            ):
-                raise exceptions.PermissionDenied(
-                    "Only owners of a resource can assign other users as owners."
-                )
-
-        # pylint: disable=no-member
-        attrs[f"{self.Meta.resource_field_name}_id"] = self.context["resource_id"]
-        return attrs
-
-
-class DocumentAccessSerializer(BaseAccessSerializer):
+class DocumentAccessSerializer(serializers.ModelSerializer):
     """Serialize document accesses."""
 
     document_id = serializers.PrimaryKeyRelatedField(
@@ -124,6 +53,7 @@ class DocumentAccessSerializer(BaseAccessSerializer):
         allow_null=True,
     )
     user = UserSerializer(read_only=True)
+    abilities = serializers.SerializerMethodField(read_only=True)
     max_ancestors_role = serializers.SerializerMethodField(read_only=True)
 
     class Meta:
@@ -141,10 +71,22 @@ class DocumentAccessSerializer(BaseAccessSerializer):
         ]
         read_only_fields = ["id", "document_id", "abilities", "max_ancestors_role"]
 
+    def get_abilities(self, instance) -> dict:
+        """Return abilities of the logged-in user on the instance."""
+        request = self.context.get("request")
+        if request:
+            return instance.get_abilities(request.user)
+        return {}
+
     def get_max_ancestors_role(self, instance):
         """Return max_ancestors_role if annotated; else None."""
         return getattr(instance, "max_ancestors_role", None)
 
+    def update(self, instance, validated_data):
+        """Make "user" field is readonly but only on update."""
+        validated_data.pop("user", None)
+        return super().update(instance, validated_data)
+
 
 class DocumentAccessLightSerializer(DocumentAccessSerializer):
     """Serialize document accesses with limited fields."""
@@ -173,15 +115,29 @@ class DocumentAccessLightSerializer(DocumentAccessSerializer):
         ]
 
 
-class TemplateAccessSerializer(BaseAccessSerializer):
+class TemplateAccessSerializer(serializers.ModelSerializer):
     """Serialize template accesses."""
 
+    abilities = serializers.SerializerMethodField(read_only=True)
+
     class Meta:
         model = models.TemplateAccess
         resource_field_name = "template"
         fields = ["id", "user", "team", "role", "abilities"]
         read_only_fields = ["id", "abilities"]
 
+    def get_abilities(self, instance) -> dict:
+        """Return abilities of the logged-in user on the instance."""
+        request = self.context.get("request")
+        if request:
+            return instance.get_abilities(request.user)
+        return {}
+
+    def update(self, instance, validated_data):
+        """Make "user" field is readonly but only on update."""
+        validated_data.pop("user", None)
+        return super().update(instance, validated_data)
+
 
 class ListDocumentSerializer(serializers.ModelSerializer):
     """Serialize documents with limited fields for display in lists."""
diff --git a/src/backend/core/api/viewsets.py b/src/backend/core/api/viewsets.py
index f5422da1..5f766293 100644
--- a/src/backend/core/api/viewsets.py
+++ b/src/backend/core/api/viewsets.py
@@ -19,6 +19,7 @@ from django.db.models.expressions import RawSQL
 from django.db.models.functions import Left, Length
 from django.http import Http404, StreamingHttpResponse
 from django.urls import reverse
+from django.utils.functional import cached_property
 from django.utils.text import capfirst, slugify
 from django.utils.translation import gettext_lazy as _
 
@@ -356,7 +357,7 @@ class DocumentViewSet(
     ordering_fields = ["created_at", "updated_at", "title"]
     pagination_class = Pagination
     permission_classes = [
-        permissions.DocumentAccessPermission,
+        permissions.DocumentPermission,
     ]
     queryset = models.Document.objects.all()
     serializer_class = serializers.DocumentSerializer
@@ -842,7 +843,7 @@ class DocumentViewSet(
         try:
             current_document = self.queryset.only("depth", "path").get(pk=pk)
         except models.Document.DoesNotExist as excpt:
-            raise drf.exceptions.NotFound from excpt
+            raise drf.exceptions.NotFound() from excpt
 
         ancestors = (
             (current_document.get_ancestors() | self.queryset.filter(pk=pk))
@@ -902,7 +903,10 @@ class DocumentViewSet(
     @drf.decorators.action(
         detail=True,
         methods=["post"],
-        permission_classes=[permissions.IsAuthenticated, permissions.AccessPermission],
+        permission_classes=[
+            permissions.IsAuthenticated,
+            permissions.DocumentPermission,
+        ],
         url_path="duplicate",
     )
     @transaction.atomic
@@ -1473,25 +1477,32 @@ class DocumentAccessViewSet(
     """
 
     lookup_field = "pk"
-    permission_classes = [permissions.IsAuthenticated, permissions.AccessPermission]
-    queryset = models.DocumentAccess.objects.select_related("user").all()
+    permission_classes = [permissions.ResourceAccessPermission]
+    queryset = models.DocumentAccess.objects.select_related("user", "document").only(
+        "id",
+        "created_at",
+        "role",
+        "team",
+        "user__id",
+        "user__short_name",
+        "user__full_name",
+        "user__email",
+        "user__language",
+        "document__id",
+        "document__path",
+        "document__depth",
+    )
     resource_field_name = "document"
 
-    def __init__(self, *args, **kwargs):
-        """Initialize the viewset and define default value for contextual document."""
-        super().__init__(*args, **kwargs)
-        self.document = None
-
-    def initial(self, request, *args, **kwargs):
-        """Retrieve self.document with annotated user roles."""
-        super().initial(request, *args, **kwargs)
-
+    @cached_property
+    def document(self):
+        """Get related document from resource ID in url and annotate user roles."""
         try:
-            self.document = models.Document.objects.annotate_user_roles(
-                self.request.user
-            ).get(pk=self.kwargs["resource_id"])
+            return models.Document.objects.annotate_user_roles(self.request.user).get(
+                pk=self.kwargs["resource_id"]
+            )
         except models.Document.DoesNotExist as excpt:
-            raise Http404() from excpt
+            raise drf.exceptions.NotFound() from excpt
 
     def get_serializer_class(self):
         """Use light serializer for unprivileged users."""
@@ -1579,8 +1590,24 @@ class DocumentAccessViewSet(
         return drf.response.Response(serialized_data)
 
     def perform_create(self, serializer):
-        """Add a new access to the document and send an email to the new added user."""
-        access = serializer.save()
+        """
+        Actually create the new document access:
+        - Ensures the `document_id` is explicitly set from the URL
+        - If the assigned role is `OWNER`, checks that the requesting user is an owner
+          of the document. This is the only permission check deferred until this step;
+          all other access checks are handled earlier in the permission lifecycle.
+        - Sends an invitation email to the newly added user after saving the access.
+        """
+        role = serializer.validated_data.get("role")
+        if (
+            role == choices.RoleChoices.OWNER
+            and self.document.get_role(self.request.user) != choices.RoleChoices.OWNER
+        ):
+            raise drf.exceptions.PermissionDenied(
+                "Only owners of a document can assign other users as owners."
+            )
+
+        access = serializer.save(document_id=self.kwargs["resource_id"])
 
         access.document.send_invitation_email(
             access.user.email,
@@ -1626,7 +1653,7 @@ class TemplateViewSet(
     filter_backends = [drf.filters.OrderingFilter]
     permission_classes = [
         permissions.IsAuthenticatedOrSafe,
-        permissions.AccessPermission,
+        permissions.ResourceWithAccessPermission,
     ]
     ordering = ["-created_at"]
     ordering_fields = ["created_at", "updated_at", "title"]
@@ -1717,11 +1744,19 @@ class TemplateAccessViewSet(
     """
 
     lookup_field = "pk"
-    permission_classes = [permissions.IsAuthenticated, permissions.AccessPermission]
+    permission_classes = [permissions.ResourceAccessPermission]
     queryset = models.TemplateAccess.objects.select_related("user").all()
     resource_field_name = "template"
     serializer_class = serializers.TemplateAccessSerializer
 
+    @cached_property
+    def template(self):
+        """Get related template from resource ID in url."""
+        try:
+            return models.Template.objects.get(pk=self.kwargs["resource_id"])
+        except models.Template.DoesNotExist as excpt:
+            raise drf.exceptions.NotFound() from excpt
+
     def list(self, request, *args, **kwargs):
         """Restrict templates returned by the list endpoint"""
         user = self.request.user
@@ -1739,6 +1774,25 @@ class TemplateAccessViewSet(
         serializer = self.get_serializer(queryset, many=True)
         return drf.response.Response(serializer.data)
 
+    def perform_create(self, serializer):
+        """
+        Actually create the new template access:
+        - Ensures the `template_id` is explicitly set from the URL.
+        - If the assigned role is `OWNER`, checks that the requesting user is an owner
+          of the document. This is the only permission check deferred until this step;
+          all other access checks are handled earlier in the permission lifecycle.
+        """
+        role = serializer.validated_data.get("role")
+        if (
+            role == choices.RoleChoices.OWNER
+            and self.template.get_role(self.request.user) != choices.RoleChoices.OWNER
+        ):
+            raise drf.exceptions.PermissionDenied(
+                "Only owners of a template can assign other users as owners."
+            )
+
+        serializer.save(template_id=self.kwargs["resource_id"])
+
 
 class InvitationViewset(
     drf.mixins.CreateModelMixin,
@@ -1771,7 +1825,7 @@ class InvitationViewset(
     pagination_class = Pagination
     permission_classes = [
         permissions.CanCreateInvitationPermission,
-        permissions.AccessPermission,
+        permissions.ResourceWithAccessPermission,
     ]
     queryset = (
         models.Invitation.objects.all()
diff --git a/src/backend/core/models.py b/src/backend/core/models.py
index 8c4cd35b..5d16dacf 100644
--- a/src/backend/core/models.py
+++ b/src/backend/core/models.py
@@ -1291,10 +1291,10 @@ class Template(BaseModel):
     def __str__(self):
         return self.title
 
-    def get_roles(self, user):
+    def get_role(self, user):
         """Return the roles a user has on a resource as an iterable."""
         if not user.is_authenticated:
-            return []
+            return None
 
         try:
             roles = self.user_roles or []
@@ -1305,21 +1305,20 @@ class Template(BaseModel):
                 ).values_list("role", flat=True)
             except (models.ObjectDoesNotExist, IndexError):
                 roles = []
-        return roles
+
+        return RoleChoices.max(*roles)
 
     def get_abilities(self, user):
         """
         Compute and return abilities for a given user on the template.
         """
-        roles = self.get_roles(user)
-        is_owner_or_admin = bool(
-            set(roles).intersection({RoleChoices.OWNER, RoleChoices.ADMIN})
-        )
-        can_get = self.is_public or bool(roles)
-        can_update = is_owner_or_admin or RoleChoices.EDITOR in roles
+        role = self.get_role(user)
+        is_owner_or_admin = role in PRIVILEGED_ROLES
+        can_get = self.is_public or bool(role)
+        can_update = is_owner_or_admin or role == RoleChoices.EDITOR
 
         return {
-            "destroy": RoleChoices.OWNER in roles,
+            "destroy": role == RoleChoices.OWNER,
             "generate_document": can_get,
             "accesses_manage": is_owner_or_admin,
             "update": can_update,
diff --git a/src/backend/core/tests/documents/test_api_document_accesses_create.py b/src/backend/core/tests/documents/test_api_document_accesses_create.py
index 8b831980..5af0da91 100644
--- a/src/backend/core/tests/documents/test_api_document_accesses_create.py
+++ b/src/backend/core/tests/documents/test_api_document_accesses_create.py
@@ -103,32 +103,37 @@ def test_api_document_accesses_create_authenticated_reader_or_editor(
     assert not models.DocumentAccess.objects.filter(user=other_user).exists()
 
 
+@pytest.mark.parametrize("depth", [1, 2, 3])
 @pytest.mark.parametrize("via", VIA)
-def test_api_document_accesses_create_authenticated_administrator(via, mock_user_teams):
+def test_api_document_accesses_create_authenticated_administrator(
+    via, depth, mock_user_teams
+):
     """
-    Administrators of a document should be able to create document accesses
-    except for the "owner" role.
+    Administrators of a document (direct or by heritage) should be able to create
+    document accesses except for the "owner" role.
     An email should be sent to the accesses to notify them of the adding.
     """
     user = factories.UserFactory(with_owned_document=True)
-
     client = APIClient()
     client.force_login(user)
 
-    document = factories.DocumentFactory()
+    documents = []
+    for i in range(depth):
+        parent = documents[i - 1] if i > 0 else None
+        documents.append(factories.DocumentFactory(parent=parent))
+
     if via == USER:
         factories.UserDocumentAccessFactory(
-            document=document, user=user, role="administrator"
+            document=documents[0], user=user, role="administrator"
         )
     elif via == TEAM:
         mock_user_teams.return_value = ["lasuite", "unknown"]
         factories.TeamDocumentAccessFactory(
-            document=document, team="lasuite", role="administrator"
+            document=documents[0], team="lasuite", role="administrator"
         )
 
     other_user = factories.UserFactory(language="en-us")
-
-    # It should not be allowed to create an owner access
+    document = documents[-1]
     response = client.post(
         f"/api/v1.0/documents/{document.id!s}/accesses/",
         {
@@ -140,7 +145,7 @@ def test_api_document_accesses_create_authenticated_administrator(via, mock_user
 
     assert response.status_code == 403
     assert response.json() == {
-        "detail": "Only owners of a resource can assign other users as owners."
+        "detail": "Only owners of a document can assign other users as owners."
     }
 
     # It should be allowed to create a lower access
@@ -184,28 +189,35 @@ def test_api_document_accesses_create_authenticated_administrator(via, mock_user
     assert "docs/" + str(document.id) + "/" in email_content
 
 
+@pytest.mark.parametrize("depth", [1, 2, 3])
 @pytest.mark.parametrize("via", VIA)
-def test_api_document_accesses_create_authenticated_owner(via, mock_user_teams):
+def test_api_document_accesses_create_authenticated_owner(via, depth, mock_user_teams):
     """
-    Owners of a document should be able to create document accesses whatever the role.
-    An email should be sent to the accesses to notify them of the adding.
+    Owners of a document (direct or by heritage) should be able to create document accesses
+    whatever the role. An email should be sent to the accesses to notify them of the adding.
     """
     user = factories.UserFactory()
 
     client = APIClient()
     client.force_login(user)
 
-    document = factories.DocumentFactory()
+    documents = []
+    for i in range(depth):
+        parent = documents[i - 1] if i > 0 else None
+        documents.append(factories.DocumentFactory(parent=parent))
+
     if via == USER:
-        factories.UserDocumentAccessFactory(document=document, user=user, role="owner")
+        factories.UserDocumentAccessFactory(
+            document=documents[0], user=user, role="owner"
+        )
     elif via == TEAM:
         mock_user_teams.return_value = ["lasuite", "unknown"]
         factories.TeamDocumentAccessFactory(
-            document=document, team="lasuite", role="owner"
+            document=documents[0], team="lasuite", role="owner"
         )
 
     other_user = factories.UserFactory(language="en-us")
-
+    document = documents[-1]
     role = random.choice([role[0] for role in models.RoleChoices.choices])
 
     assert len(mail.outbox) == 0
diff --git a/src/backend/core/tests/templates/test_api_template_accesses_create.py b/src/backend/core/tests/templates/test_api_template_accesses_create.py
index f52a5344..a33cd470 100644
--- a/src/backend/core/tests/templates/test_api_template_accesses_create.py
+++ b/src/backend/core/tests/templates/test_api_template_accesses_create.py
@@ -133,7 +133,7 @@ def test_api_template_accesses_create_authenticated_administrator(via, mock_user
 
     assert response.status_code == 403
     assert response.json() == {
-        "detail": "Only owners of a resource can assign other users as owners."
+        "detail": "Only owners of a template can assign other users as owners."
     }
 
     # It should be allowed to create a lower access