diff --git a/label_studio/data_manager/api.py b/label_studio/data_manager/api.py
index 9ca9182f1dcd..874ab9cf71e6 100644
--- a/label_studio/data_manager/api.py
+++ b/label_studio/data_manager/api.py
@@ -513,7 +513,7 @@ def get(self, request):
         pk = int_from_request(request.GET, 'project', 1)  # replace 1 to None, it's for debug only
         project = generics.get_object_or_404(Project, pk=pk)
         self.check_object_permissions(request, project)
-        data = ProjectSerializer(project).data
+        data = ProjectSerializer(project, context={'request': request}).data
 
         data.update(
             {
diff --git a/label_studio/tests/data_manager/test_project_api.py b/label_studio/tests/data_manager/test_project_api.py
new file mode 100644
index 000000000000..8fa89644fbd2
--- /dev/null
+++ b/label_studio/tests/data_manager/test_project_api.py
@@ -0,0 +1,96 @@
+"""This file and its contents are licensed under the Apache License 2.0. Please see the included NOTICE for copyright information and LICENSE for a copy of the license."""
+
+import json
+
+import pytest
+from rest_framework import status
+
+from ..utils import project_id  # noqa
+
+pytestmark = pytest.mark.django_db
+
+
+def test_dm_project_returns_200(business_client, project_id):
+    """
+    Regression: GET /api/dm/project?project={id} must return 200.
+
+    Previously, ProjectSerializer was instantiated without context in
+    data_manager/api.py, causing KeyError in the user_id property when
+    queue_total / queue_done SerializerMethodFields were evaluated
+    during serialization.
+    """
+    response = business_client.get(f'/api/dm/project?project={project_id}')
+
+    assert response.status_code == status.HTTP_200_OK, response.content
+
+
+def test_dm_project_includes_queue_fields(business_client, project_id):
+    """Response must include queue_total and queue_done computed against the request user."""
+    response = business_client.get(f'/api/dm/project?project={project_id}')
+
+    assert response.status_code == status.HTTP_200_OK, response.content
+    data = response.json()
+    assert 'queue_total' in data
+    assert 'queue_done' in data
+    assert isinstance(data['queue_total'], int)
+    assert isinstance(data['queue_done'], int)
+
+
+def test_dm_project_on_freshly_created_project(business_client):
+    """
+    Same regression, but exercised against a freshly created empty project
+    to ensure the fix holds regardless of pre-existing tasks/annotations.
+    """
+    r = business_client.post(
+        '/api/projects/',
+        data=json.dumps(dict(title='test_dm_project_regression')),
+        content_type='application/json',
+    )
+    assert r.status_code == 201, r.content
+    new_project_id = r.json()['id']
+
+    response = business_client.get(f'/api/dm/project?project={new_project_id}')
+
+    assert response.status_code == status.HTTP_200_OK, response.content
+    data = response.json()
+    assert data['queue_total'] == 0
+    assert data['queue_done'] == 0
+
+
+def test_dm_project_returns_404_for_missing_project(business_client):
+    """Unknown project id should return 404, not 500."""
+    response = business_client.get('/api/dm/project?project=999999')
+
+    assert response.status_code == status.HTTP_404_NOT_FOUND, response.content
+
+
+def test_dm_project_null_creator_returns_200(business_client):
+    """
+    Regression: GET /api/dm/project returns HTTP 500 when project.created_by is None.
+
+    Root cause: ProjectSerializer was called without context. The user_id property
+    fell back to context['user_cache'], which is populated as a side-effect of
+    serializing the created_by field via UserSimpleSerializer. When created_by is
+    None, DRF skips UserSimpleSerializer entirely, user_cache is never set, and
+    user_id raises KeyError: 'user_cache'.
+
+    Fix: pass context={'request': request} so user_id resolves from the request directly.
+    """
+    from projects.models import Project
+
+    r = business_client.post(
+        '/api/projects/',
+        data=json.dumps(dict(title='test_null_creator')),
+        content_type='application/json',
+    )
+    assert r.status_code == 201, r.content
+    project_id = r.json()['id']
+
+    Project.objects.filter(pk=project_id).update(created_by=None)
+
+    response = business_client.get(f'/api/dm/project?project={project_id}')
+
+    assert response.status_code == status.HTTP_200_OK, response.content
+    data = response.json()
+    assert isinstance(data['queue_total'], int)
+    assert isinstance(data['queue_done'], int)