diff --git a/tests/test_comfyui_integration.py b/tests/test_comfyui_integration.py
index 9d26551..67473cd 100644
--- a/tests/test_comfyui_integration.py
+++ b/tests/test_comfyui_integration.py
@@ -76,8 +76,11 @@ class IntegrationTestCase(unittest.TestCase):
     def setUp(self):
         ComfyUIMetadataIntegration._instance = None
         comfyui_integration._integration_instance = None
+        # Patch the module's own ``time`` name rather than ``time.time`` globally:
+        # background threads from other tests (image monitor, watchdog) would
+        # otherwise tick this clock and make fresh registrations look stale.
         self.clock = mock.patch.object(
-            comfyui_integration.time, "time", side_effect=self._now
+            comfyui_integration, "time", types.SimpleNamespace(time=self._now)
         )
         self.clock.start()
         self.addCleanup(self.clock.stop)
diff --git a/tests/test_diagnostics_config.py b/tests/test_diagnostics_config.py
index cc69437..b53dc1a 100644
--- a/tests/test_diagnostics_config.py
+++ b/tests/test_diagnostics_config.py
@@ -112,10 +112,12 @@ class TestAdminEndpointsUseConfigPath(unittest.TestCase):
 
             with sqlite3.connect(db_file) as conn:
                 conn.execute(
-                    "CREATE TABLE prompts (id INTEGER PRIMARY KEY, text TEXT, created_at TEXT)"
+                    "CREATE TABLE prompts "
+                    "(id INTEGER PRIMARY KEY, text TEXT, created_at TEXT)"
                 )
                 conn.execute(
-                    "INSERT INTO prompts (text, created_at) VALUES ('test', '2024-01-01')"
+                    "INSERT INTO prompts (text, created_at) "
+                    "VALUES ('test', '2024-01-01')"
                 )
 
             stub = self._make_api_stub(db_file)
@@ -155,20 +157,29 @@ class TestAdminEndpointsUseConfigPath(unittest.TestCase):
 
         from py.api.admin import AdminRoutesMixin
 
+        from database.operations import PromptDatabase
+
         with tempfile.NamedTemporaryFile(delete=False, suffix=".db") as f:
             db_file = f.name
-            f.write(b"SQLite format 3\x00test data for backup")
 
+        # A WAL-safe backup copies pages through sqlite itself, so the
+        # configured path has to hold a real database, not arbitrary bytes.
+        real_db = PromptDatabase(db_file)
         try:
             stub = self._make_api_stub(db_file)
+            stub.db.model = real_db.model
             result = self._run_async(
                 AdminRoutesMixin.backup_database(stub, MagicMock())
             )
 
             self.assertEqual(result.content_type, "application/octet-stream")
             self.assertGreater(len(result.body), 0)
+            self.assertTrue(result.body.startswith(b"SQLite format 3\x00"))
         finally:
-            os.unlink(db_file)
+            real_db.close()
+            for suffix in ("", "-wal", "-shm"):
+                if os.path.exists(db_file + suffix):
+                    os.unlink(db_file + suffix)
 
     def test_backup_reports_missing_custom_path(self):
         """backup_database should return 404 when configured path doesn't exist."""
diff --git a/tests/test_utils_logging_config.py b/tests/test_utils_logging_config.py
index c7e8a61..b254875 100644
--- a/tests/test_utils_logging_config.py
+++ b/tests/test_utils_logging_config.py
@@ -5,6 +5,7 @@ import os
 import pathlib
 import sys
 import tempfile
+import threading
 import unittest
 import unittest.mock as mock
 
@@ -32,7 +33,14 @@ class IsolatedLoggerTestCase(unittest.TestCase):
             self.manager = object.__new__(PromptManagerLogger)  # bypass singleton
             self.manager.__init__()
         self.manager.update_config({"console_logging": False})
-        self.manager._log_buffer.clear()  # drop the "Updated logging configuration" entry
+        # Drop the "Updated logging configuration" entry.
+        self.manager._log_buffer.clear()
+        # Other tests leave daemon threads (image monitor, watchdog) logging under
+        # "prompt_manager.*"; only records from this test's thread may reach the buffer.
+        this_thread = threading.get_ident()
+        for handler in self.manager.logger.handlers:
+            if isinstance(handler, MemoryBufferHandler):
+                handler.addFilter(lambda record: record.thread == this_thread)
         self.logger = logging.getLogger("prompt_manager.coverage_test")
         self.addCleanup(self._restore_global_logging)