diff --git a/core/tests.py b/core/tests.py
index c46d493..8679c60 100644
--- a/core/tests.py
+++ b/core/tests.py
@@ -3862,3 +3862,42 @@ class AttendanceDateRangeCapTests(TestCase):
     def test_range_of_exactly_31_days_is_allowed(self):
         errs = self._range_errors('2026-01-01', '2026-02-01')   # 31-day diff
         self.assertFalse(any('31 days' in e for e in errs), errs)
+
+
+# =============================================================================
+# === AUDIT FIX #6 — WORKER REPORT VIEWS MUST SURVIVE BAD QUERY PARAMS ===
+# Stale bookmarks and hand-edited URLs (?project=99999 after a delete,
+# ?team=abc from a typo) hit all three worker-report views (HTML / CSV /
+# PDF). Bad filter values must degrade to "no filter", never 500.
+# render_to_pdf is mocked so these tests don't depend on the local GTK3
+# install — the crashes under test happen BEFORE PDF rendering anyway.
+# =============================================================================
+
+class WorkerReportBadParamsTests(TestCase):
+    """?project= / ?team= junk degrades gracefully on all 3 report views."""
+
+    def setUp(self):
+        self.admin = User.objects.create_user(
+            username='pdfguard_admin', password='x', is_staff=True)
+        self.client.force_login(self.admin)
+
+    def _get_pdf(self, params):
+        with mock.patch('core.utils.render_to_pdf',
+                        return_value=b'%PDF-1.4 fake'):
+            return self.client.get(reverse('worker_batch_report_pdf'), params)
+
+    def test_pdf_nonexistent_project_id_falls_back(self):
+        resp = self._get_pdf({'project': '99999'})
+        self.assertEqual(resp.status_code, 200)
+
+    def test_pdf_non_numeric_team_falls_back(self):
+        resp = self._get_pdf({'team': 'abc'})
+        self.assertEqual(resp.status_code, 200)
+
+    def test_html_non_numeric_project_falls_back(self):
+        resp = self.client.get(reverse('worker_batch_report'), {'project': 'abc'})
+        self.assertEqual(resp.status_code, 200)
+
+    def test_csv_non_numeric_team_falls_back(self):
+        resp = self.client.get(reverse('worker_batch_report_csv'), {'team': 'abc'})
+        self.assertEqual(resp.status_code, 200)
diff --git a/core/views.py b/core/views.py
index d9f814e..ec6d87e 100644
--- a/core/views.py
+++ b/core/views.py
@@ -1645,6 +1645,19 @@ def worker_edit(request, worker_id=None):
 # === WORKER BATCH REPORT ===
 # =============================================================
 
+def _int_param_or_none(raw):
+    """Coerce a raw query-string value to int, or None if absent/invalid.
+
+    Stale bookmarks and hand-edited URLs (?project=abc, ?team= after a
+    delete) must degrade to "no filter" — never crash the view with a
+    ValueError deep inside a queryset. (Audit fix, Jun 2026.)
+    """
+    try:
+        return int(raw)
+    except (TypeError, ValueError):
+        return None
+
+
 def _build_worker_report_context(status=None, project_id=None, team_id=None):
     """Build the per-worker aggregation list used by HTML / CSV / PDF views.
 
@@ -1724,8 +1737,8 @@ def worker_batch_report(request):
         return HttpResponseForbidden("Admin access required.")
 
     status = request.GET.get('status') or 'all'
-    project_id = request.GET.get('project') or None
-    team_id = request.GET.get('team') or None
+    project_id = _int_param_or_none(request.GET.get('project'))
+    team_id = _int_param_or_none(request.GET.get('team'))
 
     rows = _build_worker_report_context(status=status, project_id=project_id, team_id=team_id)
 
@@ -1749,8 +1762,8 @@ def worker_batch_report_csv(request):
         return HttpResponseForbidden("Admin access required.")
 
     status = request.GET.get('status') or 'all'
-    project_id = request.GET.get('project') or None
-    team_id = request.GET.get('team') or None
+    project_id = _int_param_or_none(request.GET.get('project'))
+    team_id = _int_param_or_none(request.GET.get('team'))
 
     rows = _build_worker_report_context(status=status, project_id=project_id, team_id=team_id)
 
@@ -1788,18 +1801,27 @@ def worker_batch_report_pdf(request):
     from .utils import render_to_pdf
 
     status = request.GET.get('status') or 'all'
-    project_id = request.GET.get('project') or None
-    team_id = request.GET.get('team') or None
+    project_id = _int_param_or_none(request.GET.get('project'))
+    team_id = _int_param_or_none(request.GET.get('team'))
 
     rows = _build_worker_report_context(status=status, project_id=project_id, team_id=team_id)
 
+    # Filter names are display-only — a deleted project/team (stale
+    # bookmark) degrades to the unfiltered label instead of crashing.
+    try:
+        project_name = Project.objects.get(id=project_id).name if project_id else 'All Projects'
+    except Project.DoesNotExist:
+        project_name = 'All Projects'
+    try:
+        team_name = Team.objects.get(id=team_id).name if team_id else 'All Teams'
+    except Team.DoesNotExist:
+        team_name = 'All Teams'
+
     context = {
         'rows': rows,
         'status': status,
-        'project_name': (
-            Project.objects.get(id=project_id).name if project_id else 'All Projects'
-        ),
-        'team_name': Team.objects.get(id=team_id).name if team_id else 'All Teams',
+        'project_name': project_name,
+        'team_name': team_name,
         'now': timezone.now(),
         'total_workers': len(rows),
     }