diff --git a/core/tests.py b/core/tests.py
index c220a5c..98b84aa 100644
--- a/core/tests.py
+++ b/core/tests.py
@@ -964,8 +964,12 @@ class AdjustmentsTabTests(TestCase):
         self.w2 = Worker.objects.create(
             name='Bob', id_number='B1', monthly_salary=Decimal('4000')
         )
+        # Two teams, BOTH workers in BOTH teams, so the naive M2M JOIN
+        # multiplies rows by team count. Exercises the subquery fix.
         self.team = Team.objects.create(name='Alpha', supervisor=self.admin)
+        self.team2 = Team.objects.create(name='Beta', supervisor=self.admin)
         self.team.workers.add(self.w1, self.w2)
+        self.team2.workers.add(self.w1, self.w2)
         self.proj = Project.objects.create(name='Site X')
         # 3 unpaid adjustments — 1 bonus Alice, 1 bonus Bob, 1 deduction Alice
         self.a1 = PayrollAdjustment.objects.create(
@@ -1003,12 +1007,13 @@ class AdjustmentsTabTests(TestCase):
         self.assertEqual(resp.status_code, 302)
 
     def test_type_multi_filter(self):
+        """?type=Bonus&type=Deduction returns the UNION (3 rows: 2 bonuses + 1
+        deduction), not the intersection."""
         self._login_admin()
-        resp = self.client.get(self.url + '&type=Bonus')
+        resp = self.client.get(self.url + '&type=Bonus&type=Deduction')
+        self.assertEqual(resp.context['adj_total_count'], 3)
         ids = {a.id for a in resp.context['adj_page'].object_list}
-        self.assertIn(self.a1.id, ids)
-        self.assertIn(self.a2.id, ids)
-        self.assertNotIn(self.a3.id, ids)
+        self.assertEqual(ids, {self.a1.id, self.a2.id, self.a3.id})
 
     def test_worker_multi_filter(self):
         self._login_admin()
@@ -1019,10 +1024,17 @@ class AdjustmentsTabTests(TestCase):
         self.assertIn(self.a3.id, ids)
 
     def test_team_filter_uses_subquery_no_inflation(self):
-        """Filtering by team must NOT multiply rows (M2M JOIN inflation
-        would give 6 rows for 3 adjustments x 2 workers on team Alpha)."""
+        """Filtering by team must NOT multiply rows. With 2 teams x 2 workers x 3
+        adjustments, a naive worker__teams__id__in filter would return 6 inflated
+        rows; the subquery pattern returns the true 3. See CLAUDE.md ORM gotcha."""
         self._login_admin()
-        resp = self.client.get(self.url + f'&team={self.team.id}')
+        resp = self.client.get(
+            self.url + f'&team={self.team.id}&team={self.team2.id}'
+        )
+        # .count() at the queryset level would blow up under inflation —
+        # asserting it guards against regressions more strictly than checking
+        # the paginator's object_list length.
+        self.assertEqual(resp.context['adj_total_count'], 3)
         self.assertEqual(len(resp.context['adj_page'].object_list), 3)
 
     def test_status_filter_unpaid(self):