diff --git a/docs/plans/original-completion-2026-10-02/execution/p28-01/restart/probe/test_restart.py b/docs/plans/original-completion-2026-10-02/execution/p28-01/restart/probe/test_restart.py
index cf16653..b551ad9 100644
--- a/docs/plans/original-completion-2026-10-02/execution/p28-01/restart/probe/test_restart.py
+++ b/docs/plans/original-completion-2026-10-02/execution/p28-01/restart/probe/test_restart.py
@@ -191,6 +191,24 @@ def synthetic_receipt(out):
 
 
 class RestartTests(unittest.TestCase):
+    @staticmethod
+    def here_inventory():
+        return {str(path.relative_to(check.HERE)): hashlib.sha256(path.read_bytes()).hexdigest()
+                for path in check.HERE.rglob("*") if path.is_file()}
+
+    @classmethod
+    def setUpClass(cls):
+        cls.inventory_before = cls.here_inventory()
+
+    def setUp(self):
+        # Check after every test, including failures, independently of test order.
+        self.addCleanup(lambda: self.assertEqual(self.here_inventory(), self.inventory_before))
+
+    def test_zz_here_inventory_unchanged(self):
+        # unittest's default ordering places this after all twelve existing tests.
+        self.assertIn("test_restart.py", self.inventory_before)
+        self.assertEqual(self.here_inventory(), self.inventory_before)
+
     def rejects(self, original, mutations, validator):
         for name, mutation in mutations.items():
             with self.subTest(rejection=name):
@@ -328,7 +346,7 @@ class RestartTests(unittest.TestCase):
             next(iterator)
 
     def test_d3_transfer_and_fresh_profiles(self):
-        with tempfile.TemporaryDirectory(dir=check.HERE) as temporary:
+        with tempfile.TemporaryDirectory(dir=os.environ.get("BUILD_OUTPUT_DIR") or None) as temporary:
             base = Path(temporary)
             source = base / "source"
             source.mkdir()
@@ -366,7 +384,7 @@ class RestartTests(unittest.TestCase):
                 check.check_probe(text.replace("GameClock.advance_minutes(1)", replacement))
 
     def test_rs7_rs8_full_receipt_rejections(self):
-        with tempfile.TemporaryDirectory(dir=check.HERE) as temporary:
+        with tempfile.TemporaryDirectory(dir=os.environ.get("BUILD_OUTPUT_DIR") or None) as temporary:
             out = Path(temporary)
             receipt = synthetic_receipt(out)
             check.check_receipt(receipt, out)
@@ -391,7 +409,7 @@ class RestartTests(unittest.TestCase):
                 check.check_receipt(receipt, out)
 
     def test_d6_raw_report_and_audio(self):
-        with tempfile.TemporaryDirectory(dir=check.HERE) as temporary:
+        with tempfile.TemporaryDirectory(dir=os.environ.get("BUILD_OUTPUT_DIR") or None) as temporary:
             out = Path(temporary)
             receipt = synthetic_receipt(out)
             row = receipt["phases"][3]
@@ -418,7 +436,7 @@ class RestartTests(unittest.TestCase):
             "time.sleep(0.15)\n"
             "if mode=='timeout': time.sleep(5)\n"
             "sys.exit(3 if mode=='exit' else 0)\n")
-        with tempfile.TemporaryDirectory(dir=check.HERE) as temporary:
+        with tempfile.TemporaryDirectory(dir=os.environ.get("BUILD_OUTPUT_DIR") or None) as temporary:
             base = Path(temporary)
             script = base / "fake-child"
             script.write_text(child)