diff --git a/server/tests/api/test_audio_processing_templates_api.py b/server/tests/api/test_audio_processing_templates_api.py
index d2ddd77..cd7b76a 100644
--- a/server/tests/api/test_audio_processing_templates_api.py
+++ b/server/tests/api/test_audio_processing_templates_api.py
@@ -1,9 +1,7 @@
 """API tests for audio processing template endpoints."""
 
 import pytest
-from fastapi.testclient import TestClient
 
-from wled_controller.main import app
 from wled_controller.config import get_config
 
 # Ensure audio filters registered
@@ -17,6 +15,9 @@ AUTH = {"Authorization": f"Bearer {_api_key}"} if _api_key else {}
 @pytest.fixture(scope="module")
 def client():
     """Provide a TestClient with lifespan (startup/shutdown) properly triggered."""
+    from fastapi.testclient import TestClient
+    from wled_controller.main import app
+
     with TestClient(app) as c:
         yield c
 
diff --git a/server/tests/conftest.py b/server/tests/conftest.py
index 12d246c..f7e295e 100644
--- a/server/tests/conftest.py
+++ b/server/tests/conftest.py
@@ -1,20 +1,52 @@
-"""Pytest configuration and shared fixtures."""
+"""Pytest configuration and shared fixtures.
 
+IMPORTANT: This conftest patches the global config singleton BEFORE any test
+module can import ``wled_controller.main``.  ``main.py`` reads ``get_config()``
+at module level to open the database — if the singleton is not patched first,
+the REAL production database (``data/ledgrab.db``) is opened and tests
+read/write/delete production data.
+"""
+
+import tempfile
 from datetime import datetime, timezone
+from pathlib import Path
 
 import pytest
 
-from wled_controller.config import Config, StorageConfig, ServerConfig, AuthConfig
-from wled_controller.storage.database import Database
-from wled_controller.storage.device_store import Device, DeviceStore
-from wled_controller.storage.sync_clock import SyncClock
-from wled_controller.storage.sync_clock_store import SyncClockStore
-from wled_controller.storage.output_target_store import OutputTargetStore
-from wled_controller.storage.automation import (
-    Automation,
+# ---------------------------------------------------------------------------
+# ISOLATE ALL TESTS FROM PRODUCTION DATA — must happen before any test module
+# imports ``wled_controller.main``.
+# ---------------------------------------------------------------------------
+
+import wled_controller.config as _config_mod  # noqa: E402
+
+_test_tmp = Path(tempfile.mkdtemp(prefix="wled_test_"))
+_test_db_path = str(_test_tmp / "test_ledgrab.db")
+_test_assets_dir = str(_test_tmp / "test_assets")
+
+_original_config = _config_mod.Config.load()
+_test_config = _original_config.model_copy(
+    update={
+        "storage": _config_mod.StorageConfig(database_file=_test_db_path),
+        "assets": _config_mod.AssetsConfig(
+            assets_dir=_test_assets_dir,
+            max_file_size_mb=_original_config.assets.max_file_size_mb,
+        ),
+    },
 )
-from wled_controller.storage.automation_store import AutomationStore
-from wled_controller.storage.value_source_store import ValueSourceStore
+_config_mod.config = _test_config
+
+# ---------------------------------------------------------------------------
+
+from wled_controller.config import Config, StorageConfig, ServerConfig, AuthConfig  # noqa: E402
+from wled_controller.storage.database import Database  # noqa: E402
+from wled_controller.storage.device_store import Device, DeviceStore  # noqa: E402
+from wled_controller.storage.sync_clock import SyncClock  # noqa: E402
+from wled_controller.storage.sync_clock_store import SyncClockStore  # noqa: E402
+from wled_controller.storage.output_target_store import OutputTargetStore  # noqa: E402
+from wled_controller.storage.automation import Automation  # noqa: E402
+from wled_controller.storage.automation_store import AutomationStore  # noqa: E402
+from wled_controller.storage.value_source_store import ValueSourceStore  # noqa: E402
 
 
 # ---------------------------------------------------------------------------
@@ -242,3 +274,17 @@ def sample_calibration():
             {"edge": "left", "led_start": 110, "led_count": 40, "reverse": True},
         ],
     }
+
+
+# ---------------------------------------------------------------------------
+# Session cleanup — remove temporary test directory
+# ---------------------------------------------------------------------------
+
+
+@pytest.fixture(scope="session", autouse=True)
+def _cleanup_test_tmp():
+    """Remove the temporary test directory after all tests complete."""
+    import shutil
+
+    yield
+    shutil.rmtree(_test_tmp, ignore_errors=True)
diff --git a/server/tests/test_api.py b/server/tests/test_api.py
index bc0e564..30fabf5 100644
--- a/server/tests/test_api.py
+++ b/server/tests/test_api.py
@@ -4,31 +4,39 @@ import os
 import sys
 
 import pytest
-from fastapi.testclient import TestClient
 
-from wled_controller.main import app
 from wled_controller import __version__
 from wled_controller.config import get_config
 
-_has_display = bool(os.environ.get("DISPLAY") or sys.platform == "win32" or sys.platform == "darwin")
+_has_display = bool(
+    os.environ.get("DISPLAY") or sys.platform == "win32" or sys.platform == "darwin"
+)
 requires_display = pytest.mark.skipif(not _has_display, reason="No display available (headless CI)")
 
-client = TestClient(app)
-
 # Build auth header from the first configured API key
 _config = get_config()
 _api_key = next(iter(_config.auth.api_keys.values()), "")
 AUTH_HEADERS = {"Authorization": f"Bearer {_api_key}"} if _api_key else {}
 
 
-def test_root_endpoint():
+@pytest.fixture(scope="module")
+def client():
+    """Provide a TestClient backed by the isolated test database."""
+    from fastapi.testclient import TestClient
+    from wled_controller.main import app
+
+    with TestClient(app, raise_server_exceptions=False) as c:
+        yield c
+
+
+def test_root_endpoint(client):
     """Test root endpoint returns the HTML dashboard."""
     response = client.get("/")
     assert response.status_code == 200
     assert "text/html" in response.headers["content-type"]
 
 
-def test_health_check():
+def test_health_check(client):
     """Test health check endpoint."""
     response = client.get("/health")
     assert response.status_code == 200
@@ -38,7 +46,7 @@ def test_health_check():
     assert "timestamp" in data
 
 
-def test_version_endpoint():
+def test_version_endpoint(client):
     """Test version endpoint."""
     response = client.get("/api/v1/version")
     assert response.status_code == 200
@@ -49,7 +57,7 @@ def test_version_endpoint():
 
 
 @requires_display
-def test_get_displays():
+def test_get_displays(client):
     """Test get displays endpoint (requires auth and a real display)."""
     response = client.get("/api/v1/config/displays", headers=AUTH_HEADERS)
     assert response.status_code == 200
@@ -69,7 +77,7 @@ def test_get_displays():
         assert "is_primary" in display
 
 
-def test_openapi_docs():
+def test_openapi_docs(client):
     """Test OpenAPI documentation is available."""
     response = client.get("/openapi.json")
     assert response.status_code == 200
@@ -77,7 +85,7 @@ def test_openapi_docs():
     assert data["info"]["version"] == __version__
 
 
-def test_swagger_ui():
+def test_swagger_ui(client):
     """Test Swagger UI is available."""
     response = client.get("/docs")
     assert response.status_code == 200