diff --git a/CHANGELOG.md b/CHANGELOG.md
index d0392b7ae..eff4b3906 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,10 @@ and this project adheres to
 
 ## [Unreleased]
 
+### Changed
+
+- ♻️(backend) reset collaboration connection in cascade for all children #2507
+
 ## [v5.4.0] - 2026-07-07
 
 ### Added
diff --git a/src/backend/core/api/viewsets.py b/src/backend/core/api/viewsets.py
index 0b8e5f213..5d9991bcb 100644
--- a/src/backend/core/api/viewsets.py
+++ b/src/backend/core/api/viewsets.py
@@ -68,6 +68,7 @@ from core.services.search_indexers import (
     get_document_indexer,
     get_visited_document_ids_of,
 )
+from core.tasks.access import reset_service_connections_in_cascade
 from core.tasks.mail import send_ask_for_access_mail
 from core.utils.analytics import PosthogEventName, posthog_capture
 from core.utils.paths import filter_descendants
@@ -1825,7 +1826,7 @@ class DocumentViewSet(
         serializer.save()
 
         # Notify collaboration server about the link updated
-        CollaborationService().reset_connections(str(document.id))
+        reset_service_connections_in_cascade.delay(str(document.id))
 
         return drf.response.Response(serializer.data, status=drf.status.HTTP_200_OK)
 
@@ -2839,7 +2840,7 @@ class DocumentAccessViewSet(
             access_user_id = str(access.user.id)
 
         # Notify collaboration server about the access change
-        CollaborationService().reset_connections(
+        reset_service_connections_in_cascade.delay(
             str(access.document.id), access_user_id
         )
 
@@ -2860,7 +2861,7 @@ class DocumentAccessViewSet(
         )
 
         # Notify collaboration server about the access removed
-        CollaborationService().reset_connections(document_id, user_id)
+        reset_service_connections_in_cascade.delay(document_id, user_id)
 
 
 class InvitationViewset(
diff --git a/src/backend/core/services/collaboration_services.py b/src/backend/core/services/collaboration_services.py
index 9587a1b19..fa1e1e867 100644
--- a/src/backend/core/services/collaboration_services.py
+++ b/src/backend/core/services/collaboration_services.py
@@ -1,10 +1,16 @@
 """Collaboration services."""
 
+from logging import getLogger
+
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured
 
 import requests
 
+from core import models
+
+logger = getLogger(__name__)
+
 
 class CollaborationService:
     """Service class for Collaboration related operations."""
@@ -14,12 +20,34 @@ class CollaborationService:
         if settings.COLLABORATION_API_URL is None:
             raise ImproperlyConfigured("Collaboration configuration not set")
 
-    def reset_connections(self, room, user_id=None):
+    def reset_connections(self, document_id, user_id=None):
         """
-        Reset connections of a room in the collaboration server.
+        Reset the connections of a document and all its descendants in the
+        collaboration server.
+
         Resetting a connection means that the user will be disconnected and will
         have to reconnect to the collaboration server, with updated rights.
         """
+        try:
+            document = models.Document.objects.get(pk=document_id)
+        except models.Document.DoesNotExist:
+            logger.error("Document %s does not exists anymore", document_id)
+            return
+
+        documents = models.Document.objects.filter(
+            path__startswith=document.path, depth__gte=document.depth
+        ).order_by("path")
+
+        for doc in documents:
+            try:
+                self._reset_connection(doc.id, user_id)
+            except requests.HTTPError:
+                logger.error("impossible to reset connections for document %s", doc.id)
+
+    def _reset_connection(self, room, user_id=None):
+        """
+        Reset connections of a single room in the collaboration server.
+        """
         endpoint = "reset-connections"
 
         # room is necessary as a parameter, it is easier to stick to the
diff --git a/src/backend/core/tasks/access.py b/src/backend/core/tasks/access.py
new file mode 100644
index 000000000..1f7dd1ea8
--- /dev/null
+++ b/src/backend/core/tasks/access.py
@@ -0,0 +1,14 @@
+"""Tasks dedicated to document's accesses."""
+
+from core.services.collaboration_services import CollaborationService
+
+from impress.celery_app import app
+
+
+@app.task
+def reset_service_connections_in_cascade(document_id, user_id=None):
+    """
+    For a given document_id, reset the connections of the document and all its
+    descendants by delegating to the CollaborationService.
+    """
+    CollaborationService().reset_connections(document_id, user_id)
diff --git a/src/backend/core/tests/documents/test_api_document_accesses.py b/src/backend/core/tests/documents/test_api_document_accesses.py
index 0feda4a7b..83c4b392f 100644
--- a/src/backend/core/tests/documents/test_api_document_accesses.py
+++ b/src/backend/core/tests/documents/test_api_document_accesses.py
@@ -4,6 +4,7 @@ Test document accesses API endpoints for users in impress's core app.
 # pylint: disable=too-many-lines
 
 import random
+from contextlib import contextmanager
 from unittest import mock
 from uuid import uuid4
 
@@ -13,14 +14,30 @@ from rest_framework.test import APIClient
 from core import choices, factories, models
 from core.api import serializers
 from core.tests.conftest import TEAM, USER, VIA
-from core.tests.test_services_collaboration_services import (  # pylint: disable=unused-import
-    mock_reset_connections,
-)
 from core.utils.analytics import PosthogEventName
 
 pytestmark = pytest.mark.django_db
 
 
+@pytest.fixture(name="mock_reset_connections")
+def mock_reset_connections_fixture():
+    """
+    Provide a context manager that patches the ``reset_service_connections_in_cascade``
+    Celery task and asserts its ``delay`` method is called exactly once for the given
+    document and user when leaving the context.
+    """
+
+    @contextmanager
+    def _mock_reset_connections(document_id, user_id=None):
+        with mock.patch(
+            "core.api.viewsets.reset_service_connections_in_cascade.delay"
+        ) as mock_delay:
+            yield mock_delay
+            mock_delay.assert_called_once_with(str(document_id), user_id)
+
+    return _mock_reset_connections
+
+
 def test_api_document_accesses_list_anonymous():
     """Anonymous users should not be allowed to list document accesses."""
     document = factories.DocumentFactory()
@@ -737,7 +754,7 @@ def test_api_document_accesses_update_administrator_except_owner(
     create_for,
     via,
     mock_user_teams,
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     A user who is a direct administrator in a document should be allowed to update a user
@@ -847,7 +864,7 @@ def test_api_document_accesses_update_administrator_from_owner(via, mock_user_te
 def test_api_document_accesses_update_administrator_to_owner(
     via,
     mock_user_teams,
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     A user who is an administrator in a document, should not be allowed to update
@@ -914,7 +931,7 @@ def test_api_document_accesses_update_owner(
     create_for,
     via,
     mock_user_teams,
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     A user who is an owner in a document should be allowed to update
@@ -977,7 +994,7 @@ def test_api_document_accesses_update_owner(
 def test_api_document_accesses_update_owner_self_root(
     via,
     mock_user_teams,
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     A user who is owner of a document should be allowed to update
@@ -1039,7 +1056,7 @@ def test_api_document_accesses_update_owner_self_root(
 def test_api_document_accesses_update_owner_self_child(
     via,
     mock_user_teams,
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     A user who is owner of a document should be allowed to update
@@ -1153,7 +1170,7 @@ def test_api_document_accesses_delete_reader_or_editor(via, role, mock_user_team
 def test_api_document_accesses_delete_administrators_except_owners(
     via,
     mock_user_teams,
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     Users who are administrators in a document should be allowed to delete an access
@@ -1238,7 +1255,7 @@ def test_api_document_accesses_delete_administrator_on_owners(via, mock_user_tea
 def test_api_document_accesses_delete_owners(
     via,
     mock_user_teams,
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     Users should be able to delete the document access of another user
@@ -1311,7 +1328,7 @@ def test_api_document_accesses_delete_owners_last_owner_root(via, mock_user_team
 
 
 def test_api_document_accesses_delete_owners_last_owner_child_user(
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     It should be possible to delete the last owner access from a document that is not a root.
@@ -1342,7 +1359,7 @@ def test_api_document_accesses_delete_owners_last_owner_child_user(
 )
 def test_api_document_accesses_delete_owners_last_owner_child_team(
     mock_user_teams,
-    mock_reset_connections,  # pylint: disable=redefined-outer-name
+    mock_reset_connections,
 ):
     """
     It should be possible to delete the last owner access from a document that
diff --git a/src/backend/core/tests/documents/test_api_documents_link_configuration.py b/src/backend/core/tests/documents/test_api_documents_link_configuration.py
index 2c271ca1e..9a3a3c8fd 100644
--- a/src/backend/core/tests/documents/test_api_documents_link_configuration.py
+++ b/src/backend/core/tests/documents/test_api_documents_link_configuration.py
@@ -1,18 +1,37 @@
 """Tests for link configuration of documents on API endpoint"""
 
+from contextlib import contextmanager
+from unittest import mock
+
 import pytest
 from rest_framework.test import APIClient
 
 from core import factories, models
 from core.api import serializers
 from core.tests.conftest import TEAM, USER, VIA
-from core.tests.test_services_collaboration_services import (  # pylint: disable=unused-import
-    mock_reset_connections,
-)
 
 pytestmark = pytest.mark.django_db
 
 
+@pytest.fixture(name="mock_reset_connections")
+def mock_reset_connections_fixture():
+    """
+    Provide a context manager that patches the ``reset_service_connections_in_cascade``
+    Celery task and asserts its ``delay`` method is called exactly once for the given
+    document when leaving the context.
+    """
+
+    @contextmanager
+    def _mock_reset_connections(document_id):
+        with mock.patch(
+            "core.api.viewsets.reset_service_connections_in_cascade.delay"
+        ) as mock_delay:
+            yield mock_delay
+            mock_delay.assert_called_once_with(str(document_id))
+
+    return _mock_reset_connections
+
+
 @pytest.mark.parametrize("role", models.LinkRoleChoices.values)
 @pytest.mark.parametrize("reach", models.LinkReachChoices.values)
 def test_api_documents_link_configuration_update_anonymous(reach, role):
diff --git a/src/backend/core/tests/external_api/test_external_api_documents_link_configuration.py b/src/backend/core/tests/external_api/test_external_api_documents_link_configuration.py
index 9fc3d8dd3..885862f0f 100644
--- a/src/backend/core/tests/external_api/test_external_api_documents_link_configuration.py
+++ b/src/backend/core/tests/external_api/test_external_api_documents_link_configuration.py
@@ -63,7 +63,7 @@ def test_external_api_documents_link_configuration_not_allowed(
     COLLABORATION_API_URL="http://example.com/",
     COLLABORATION_SERVER_SECRET="secret-token",
 )
-@patch("core.services.collaboration_services.CollaborationService.reset_connections")
+@patch("core.api.viewsets.reset_service_connections_in_cascade.delay")
 def test_external_api_documents_link_configuration_can_be_allowed(
     mock_reset, user_token, resource_server_backend, user_specific_sub
 ):
@@ -103,3 +103,6 @@ def test_external_api_documents_link_configuration_can_be_allowed(
     document.refresh_from_db()
     assert document.link_reach == models.LinkReachChoices.PUBLIC
     assert document.link_role == models.LinkRoleChoices.EDITOR
+
+    # the collaboration server should be notified through the Celery task
+    mock_reset.assert_called_once_with(str(document.id))
diff --git a/src/backend/core/tests/test_services_collaboration_services.py b/src/backend/core/tests/test_services_collaboration_services.py
index 5a9151700..35e607d21 100644
--- a/src/backend/core/tests/test_services_collaboration_services.py
+++ b/src/backend/core/tests/test_services_collaboration_services.py
@@ -4,8 +4,11 @@ core.services.collaboration_services module.
 """
 
 import json
+import logging
 import re
 from contextlib import contextmanager
+from unittest import mock
+from uuid import uuid4
 
 from django.core.exceptions import ImproperlyConfigured
 
@@ -13,11 +16,14 @@ import pytest
 import requests
 import responses
 
+from core import factories, models
 from core.services.collaboration_services import CollaborationService
 
+# pylint: disable=protected-access
 
-@pytest.fixture
-def mock_reset_connections(settings):
+
+@pytest.fixture(name="mock_reset_connections")
+def mock_reset_connections_fixture(settings):
     """
     Creates a context manager to mock the reset-connections endpoint for collaboration services.
     Args:
@@ -88,8 +94,8 @@ def test_init_with_api_url(settings):
 
 
 @responses.activate
-def test_reset_connections_with_user_id(settings):
-    """Test reset_connections with a provided user_id."""
+def test_reset_connection_with_user_id(settings):
+    """Test _reset_connection with a provided user_id."""
     settings.COLLABORATION_API_URL = "http://example.com/"
     settings.COLLABORATION_SERVER_SECRET = "secret-token"
     service = CollaborationService()
@@ -100,7 +106,7 @@ def test_reset_connections_with_user_id(settings):
 
     responses.add(responses.POST, endpoint_url, json={}, status=200)
 
-    service.reset_connections(room, user_id)
+    service._reset_connection(room, user_id)
 
     assert len(responses.calls) == 1
     request = responses.calls[0].request
@@ -111,8 +117,8 @@ def test_reset_connections_with_user_id(settings):
 
 
 @responses.activate
-def test_reset_connections_without_user_id(settings):
-    """Test reset_connections without a user_id."""
+def test_reset_connection_without_user_id(settings):
+    """Test _reset_connection without a user_id."""
     settings.COLLABORATION_API_URL = "http://example.com/"
     settings.COLLABORATION_SERVER_SECRET = "secret-token"
     service = CollaborationService()
@@ -128,7 +134,7 @@ def test_reset_connections_without_user_id(settings):
         status=200,
     )
 
-    service.reset_connections(room, user_id)
+    service._reset_connection(room, user_id)
 
     assert len(responses.calls) == 1
     request = responses.calls[0].request
@@ -139,7 +145,7 @@ def test_reset_connections_without_user_id(settings):
 
 
 @responses.activate
-def test_reset_connections_non_200_response(settings):
+def test_reset_connection_non_200_response(settings):
     """Test that an HTTPError is raised when the response status is not 200."""
     settings.COLLABORATION_API_URL = "http://example.com/"
     settings.COLLABORATION_SERVER_SECRET = "secret-token"
@@ -157,13 +163,13 @@ def test_reset_connections_non_200_response(settings):
     ) + re.escape(json.dumps(response_body))
 
     with pytest.raises(requests.HTTPError, match=expected_exception_message):
-        service.reset_connections(room, user_id)
+        service._reset_connection(room, user_id)
 
     assert len(responses.calls) == 1
 
 
 @responses.activate
-def test_reset_connections_request_exception(settings):
+def test_reset_connection_request_exception(settings):
     """Test that an HTTPError is raised when a RequestException occurs."""
     settings.COLLABORATION_API_URL = "http://example.com/"
     settings.COLLABORATION_SERVER_SECRET = "secret-token"
@@ -180,6 +186,159 @@ def test_reset_connections_request_exception(settings):
     )
 
     with pytest.raises(requests.HTTPError, match="Failed to notify WebSocket server."):
-        service.reset_connections(room, user_id)
+        service._reset_connection(room, user_id)
 
     assert len(responses.calls) == 1
+
+
+@pytest.fixture(name="collaboration_service")
+def collaboration_service_fixture(settings):
+    """Return a configured CollaborationService instance."""
+    settings.COLLABORATION_API_URL = "http://example.com/"
+    settings.COLLABORATION_SERVER_SECRET = "secret-token"
+    return CollaborationService()
+
+
+@pytest.mark.django_db
+@mock.patch.object(CollaborationService, "_reset_connection")
+def test_reset_connections_document_does_not_exist(
+    mock_reset_connection,
+    collaboration_service,
+    caplog,
+):
+    """
+    When the document does not exist anymore, an error is logged and no
+    connection is reset.
+    """
+    unknown_id = uuid4()
+
+    with caplog.at_level(logging.ERROR, logger="core.services.collaboration_services"):
+        collaboration_service.reset_connections(unknown_id)
+
+    mock_reset_connection.assert_not_called()
+    assert f"Document {unknown_id} does not exists anymore" in caplog.text
+
+
+@pytest.mark.django_db
+@mock.patch.object(CollaborationService, "_reset_connection")
+def test_reset_connections_single_document(
+    mock_reset_connection,
+    collaboration_service,
+):
+    """A document without descendants should have its own connections reset."""
+    document = factories.DocumentFactory()
+
+    collaboration_service.reset_connections(document.id)
+
+    mock_reset_connection.assert_called_once_with(document.id, None)
+
+
+@pytest.mark.django_db
+@mock.patch.object(CollaborationService, "_reset_connection")
+def test_reset_connections_cascade_on_document_and_descendants(
+    mock_reset_connection,
+    collaboration_service,
+):
+    """
+    The document itself and every one of its descendants should be reset,
+    ordered by path.
+    """
+    root = factories.DocumentFactory()
+    child1 = factories.DocumentFactory(parent=root)
+    child2 = factories.DocumentFactory(parent=root)
+    grandchild = factories.DocumentFactory(parent=child1)
+
+    collaboration_service.reset_connections(root.id)
+
+    expected_ids = [
+        doc.id
+        for doc in models.Document.objects.filter(
+            path__startswith=root.path, depth__gte=root.depth
+        ).order_by("path")
+    ]
+    assert set(expected_ids) == {root.id, child1.id, child2.id, grandchild.id}
+
+    called_ids = [call.args[0] for call in mock_reset_connection.call_args_list]
+    assert called_ids == expected_ids
+    assert mock_reset_connection.call_count == 4
+
+
+@pytest.mark.django_db
+@mock.patch.object(CollaborationService, "_reset_connection")
+def test_reset_connections_starts_from_a_sub_document(
+    mock_reset_connection,
+    collaboration_service,
+):
+    """
+    When called on a sub-document, only that sub-document and its own
+    descendants should be reset, not its ancestors or siblings.
+    """
+    root = factories.DocumentFactory()
+    child = factories.DocumentFactory(parent=root)
+    sibling = factories.DocumentFactory(parent=root)
+    grandchild = factories.DocumentFactory(parent=child)
+
+    collaboration_service.reset_connections(child.id)
+
+    called_ids = {call.args[0] for call in mock_reset_connection.call_args_list}
+    assert called_ids == {child.id, grandchild.id}
+    assert root.id not in called_ids
+    assert sibling.id not in called_ids
+
+
+@pytest.mark.django_db
+@mock.patch.object(CollaborationService, "_reset_connection")
+def test_reset_connections_forwards_user_id(
+    mock_reset_connection,
+    collaboration_service,
+):
+    """The provided user_id should be forwarded to every reset call."""
+    root = factories.DocumentFactory()
+    factories.DocumentFactory(parent=root)
+    user_id = str(uuid4())
+
+    collaboration_service.reset_connections(root.id, user_id=user_id)
+
+    assert mock_reset_connection.call_count == 2
+    for call in mock_reset_connection.call_args_list:
+        assert call.args[1] == user_id
+
+
+@pytest.mark.django_db
+@mock.patch.object(CollaborationService, "_reset_connection")
+def test_reset_connections_continues_on_http_error(
+    mock_reset_connection,
+    collaboration_service,
+    caplog,
+):
+    """
+    An HTTPError raised while resetting one document should be logged and must
+    not prevent the remaining documents from being processed.
+    """
+    root = factories.DocumentFactory()
+    child1 = factories.DocumentFactory(parent=root)
+    child2 = factories.DocumentFactory(parent=root)
+
+    ordered_docs = list(
+        models.Document.objects.filter(
+            path__startswith=root.path, depth__gte=root.depth
+        ).order_by("path")
+    )
+    failing_doc = ordered_docs[1]
+
+    def _side_effect(room, _user_id=None):
+        if room == failing_doc.id:
+            raise requests.HTTPError("boom")
+
+    mock_reset_connection.side_effect = _side_effect
+
+    with caplog.at_level(logging.ERROR, logger="core.services.collaboration_services"):
+        collaboration_service.reset_connections(root.id)
+
+    assert mock_reset_connection.call_count == 3
+    called_ids = [call.args[0] for call in mock_reset_connection.call_args_list]
+    assert set(called_ids) == {root.id, child1.id, child2.id}
+
+    assert (
+        f"impossible to reset connections for document {failing_doc.id}" in caplog.text
+    )
diff --git a/src/backend/core/tests/test_tasks_access.py b/src/backend/core/tests/test_tasks_access.py
new file mode 100644
index 000000000..d794c6b24
--- /dev/null
+++ b/src/backend/core/tests/test_tasks_access.py
@@ -0,0 +1,48 @@
+"""
+Tests for the `reset_service_connections_in_cascade` Celery task in the
+core.tasks.access module.
+"""
+
+from unittest import mock
+
+from django.core.exceptions import ImproperlyConfigured
+
+import pytest
+
+from core.tasks.access import reset_service_connections_in_cascade
+
+
+@mock.patch("core.tasks.access.CollaborationService")
+def test_reset_service_connections_delegates_to_service(mock_service):
+    """
+    The task should delegate the whole reset to the CollaborationService,
+    forwarding both the document id and the user id.
+    """
+    reset_service_connections_in_cascade("document-id", "user-id")
+
+    mock_service.return_value.reset_connections.assert_called_once_with(
+        "document-id", "user-id"
+    )
+
+
+@mock.patch("core.tasks.access.CollaborationService")
+def test_reset_service_connections_defaults_user_id_to_none(mock_service):
+    """When no user id is provided, the task should forward None to the service."""
+    reset_service_connections_in_cascade("document-id")
+
+    mock_service.return_value.reset_connections.assert_called_once_with(
+        "document-id", None
+    )
+
+
+@mock.patch(
+    "core.tasks.access.CollaborationService",
+    side_effect=ImproperlyConfigured("Collaboration configuration not set"),
+)
+def test_reset_service_connections_propagates_improperly_configured(mock_service):  # pylint: disable=unused-argument
+    """
+    If the collaboration service is not configured, instantiating it raises
+    ImproperlyConfigured, which should propagate out of the task.
+    """
+    with pytest.raises(ImproperlyConfigured):
+        reset_service_connections_in_cascade("document-id")