diff --git a/backend/app/api/routes/archives.py b/backend/app/api/routes/archives.py
index ac4bb5810..b517ee211 100644
--- a/backend/app/api/routes/archives.py
+++ b/backend/app/api/routes/archives.py
@@ -1270,7 +1270,7 @@ async def scan_timelapse(
     if not matching_file and (archive.started_at or archive.completed_at or archive.created_at):
         from datetime import datetime, timedelta
 
-        archive_start = archive.started_at
+        _archive_start = archive.started_at
         archive_end = archive.completed_at or archive.created_at
         best_match = None
         best_diff = timedelta(hours=24)
diff --git a/backend/app/main.py b/backend/app/main.py
index c15fd6ba2..20c86dc06 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -963,7 +963,7 @@ async def on_print_start(printer_id: int, data: dict):
                 existing_archive.failure_reason = "Stale - print likely cancelled or failed without status update"
                 await db.commit()
                 # Fall through to create new archive (don't return)
-                existing_archive = None  # Clear so we don't use stale archive
+                _existing_archive = None  # Clear so we don't use stale archive
             else:
                 logger.info(
                     f"Skipping duplicate - already have printing archive {existing_archive.id} for {check_name}"
@@ -1325,7 +1325,6 @@ async def on_print_start(printer_id: int, data: dict):
                 if not notification_sent:
                     archive_data = {"print_time_seconds": archive.print_time_seconds}
                     await _send_print_start_notification(printer_id, data, archive_data, logger)
-                    notification_sent = True
 
                 # Extract printable objects for skip object functionality
                 try:
diff --git a/backend/app/services/bambu_mqtt.py b/backend/app/services/bambu_mqtt.py
index f2477c8ef..89cf09d69 100644
--- a/backend/app/services/bambu_mqtt.py
+++ b/backend/app/services/bambu_mqtt.py
@@ -1064,7 +1064,7 @@ class BambuMQTTClient:
 
     def _update_state(self, data: dict):
         """Update printer state from message data."""
-        previous_state = self.state.state
+        _previous_state = self.state.state
 
         # Update state fields
         if "gcode_state" in data:
@@ -2370,7 +2370,7 @@ class BambuMQTTClient:
     def _handle_kprofile_response(self, data: dict):
         """Handle K-profile response from printer."""
         response_nozzle = data.get("nozzle_diameter")
-        response_seq_id = data.get("sequence_id", "?")
+        _response_seq_id = data.get("sequence_id", "?")
         filaments = data.get("filaments", [])
         expected_nozzle = getattr(self, "_expected_kprofile_nozzle", None)
         has_pending_request = self._pending_kprofile_response is not None
diff --git a/backend/app/services/timelapse_processor.py b/backend/app/services/timelapse_processor.py
index fa03faf18..5fae64ab2 100644
--- a/backend/app/services/timelapse_processor.py
+++ b/backend/app/services/timelapse_processor.py
@@ -258,7 +258,8 @@ class TimelapseProcessor:
             remaining_speed *= 2.0
 
         # Add final atempo for remaining adjustment
-        if 0.5 <= remaining_speed <= 2.0 and remaining_speed != 1.0:
+        # After the while loops above, remaining_speed is guaranteed to be in [0.5, 2.0]
+        if remaining_speed != 1.0:
             filters.append(f"atempo={remaining_speed:.4f}")
 
         return ",".join(filters)
diff --git a/backend/tests/conftest.py b/backend/tests/conftest.py
index 40f487405..ed83cef41 100644
--- a/backend/tests/conftest.py
+++ b/backend/tests/conftest.py
@@ -6,10 +6,8 @@ import json
 import logging
 import os
 import shutil
-import sys
 import tempfile
 from collections.abc import AsyncGenerator
-from datetime import datetime
 from pathlib import Path
 from unittest.mock import AsyncMock, MagicMock, patch
 
diff --git a/backend/tests/integration/test_camera_api.py b/backend/tests/integration/test_camera_api.py
index f6d31e3b4..773b06dca 100644
--- a/backend/tests/integration/test_camera_api.py
+++ b/backend/tests/integration/test_camera_api.py
@@ -3,7 +3,6 @@
 Tests the full request/response cycle for /api/v1/printers/{id}/camera/ endpoints.
 """
 
-import asyncio
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
diff --git a/backend/tests/integration/test_discovery_api.py b/backend/tests/integration/test_discovery_api.py
index 77fe16379..1c4710219 100644
--- a/backend/tests/integration/test_discovery_api.py
+++ b/backend/tests/integration/test_discovery_api.py
@@ -3,8 +3,6 @@
 Tests the full request/response cycle for /api/v1/discovery/ endpoints.
 """
 
-from unittest.mock import AsyncMock, patch
-
 import pytest
 from httpx import AsyncClient
 
diff --git a/backend/tests/integration/test_endpoint_auth.py b/backend/tests/integration/test_endpoint_auth.py
index cadde1bdb..414398b67 100644
--- a/backend/tests/integration/test_endpoint_auth.py
+++ b/backend/tests/integration/test_endpoint_auth.py
@@ -4,7 +4,7 @@ Tests that verify endpoints properly enforce authentication when auth is enabled
 and allow access when auth is disabled (CVE-2026-25505 fix verification).
 """
 
-from unittest.mock import AsyncMock, patch
+from unittest.mock import patch
 
 import pytest
 from httpx import AsyncClient
diff --git a/backend/tests/integration/test_print_lifecycle.py b/backend/tests/integration/test_print_lifecycle.py
index 24dcde112..bc166aa32 100644
--- a/backend/tests/integration/test_print_lifecycle.py
+++ b/backend/tests/integration/test_print_lifecycle.py
@@ -13,11 +13,9 @@ Full end-to-end tests require the actual database setup.
 """
 
 import asyncio
-from datetime import datetime
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
-from sqlalchemy import select
 
 
 class TestPrintStartLogic:
diff --git a/backend/tests/integration/test_printers_api.py b/backend/tests/integration/test_printers_api.py
index cc0cd1dd1..498f88fab 100644
--- a/backend/tests/integration/test_printers_api.py
+++ b/backend/tests/integration/test_printers_api.py
@@ -3,7 +3,7 @@
 Tests the full request/response cycle for /api/v1/printers/ endpoints.
 """
 
-from unittest.mock import AsyncMock, MagicMock, patch
+from unittest.mock import MagicMock, patch
 
 import pytest
 from httpx import AsyncClient
diff --git a/backend/tests/integration/test_updates_api.py b/backend/tests/integration/test_updates_api.py
index 4daaff14c..e52f28e63 100644
--- a/backend/tests/integration/test_updates_api.py
+++ b/backend/tests/integration/test_updates_api.py
@@ -1,6 +1,6 @@
 """Integration tests for Updates API endpoints."""
 
-from unittest.mock import AsyncMock, MagicMock, patch
+from unittest.mock import AsyncMock, patch
 
 import pytest
 from httpx import AsyncClient
diff --git a/backend/tests/unit/services/test_archive_service.py b/backend/tests/unit/services/test_archive_service.py
index 51e59e21a..688db05b8 100644
--- a/backend/tests/unit/services/test_archive_service.py
+++ b/backend/tests/unit/services/test_archive_service.py
@@ -1,9 +1,6 @@
 """Unit tests for the archive service."""
 
 from datetime import datetime
-from unittest.mock import AsyncMock, MagicMock, patch
-
-import pytest
 
 
 class TestArchiveServiceHelpers:
@@ -364,41 +361,25 @@ class TestThreeMFPlateIndexExtraction:
         # First priority should be plate_5.png
         assert thumbnail_paths[0] == "Metadata/plate_5.png"
 
-    def test_print_name_enhanced_for_plate_greater_than_1(self):
-        """Test that print_name is enhanced with plate info for plate > 1."""
-        plate_index = 5
-        print_name = "Benchy"
-
-        # Logic from archive.py
+    @staticmethod
+    def _enhance_print_name(print_name: str, plate_index: int) -> str:
+        """Apply plate name enhancement logic from archive.py."""
         if plate_index and plate_index > 1:
             if print_name and f"Plate {plate_index}" not in print_name:
                 print_name = f"{print_name} - Plate {plate_index}"
+        return print_name
 
-        assert print_name == "Benchy - Plate 5"
+    def test_print_name_enhanced_for_plate_greater_than_1(self):
+        """Test that print_name is enhanced with plate info for plate > 1."""
+        assert self._enhance_print_name("Benchy", 5) == "Benchy - Plate 5"
 
     def test_print_name_not_enhanced_for_plate_1(self):
         """Test that print_name is NOT enhanced for plate 1."""
-        plate_index = 1
-        print_name = "Benchy"
-
-        # Logic from archive.py
-        if plate_index and plate_index > 1:
-            if print_name and f"Plate {plate_index}" not in print_name:
-                print_name = f"{print_name} - Plate {plate_index}"
-
-        assert print_name == "Benchy"  # Unchanged for plate 1
+        assert self._enhance_print_name("Benchy", 1) == "Benchy"
 
     def test_print_name_not_duplicated(self):
         """Test that plate info is not added if already present in print_name."""
-        plate_index = 5
-        print_name = "Benchy - Plate 5"
-
-        # Logic from archive.py
-        if plate_index and plate_index > 1:
-            if print_name and f"Plate {plate_index}" not in print_name:
-                print_name = f"{print_name} - Plate {plate_index}"
-
-        assert print_name == "Benchy - Plate 5"  # Not duplicated
+        assert self._enhance_print_name("Benchy - Plate 5", 5) == "Benchy - Plate 5"
 
     def test_high_plate_number_extraction(self):
         """Test extracting high plate numbers (e.g., plate 28)."""
diff --git a/backend/tests/unit/services/test_bambu_mqtt.py b/backend/tests/unit/services/test_bambu_mqtt.py
index 50e41bf44..f490068ac 100644
--- a/backend/tests/unit/services/test_bambu_mqtt.py
+++ b/backend/tests/unit/services/test_bambu_mqtt.py
@@ -4,8 +4,6 @@ Tests for the BambuMQTTClient service.
 These tests focus on timelapse tracking during prints.
 """
 
-from unittest.mock import MagicMock, patch
-
 import pytest
 
 
diff --git a/backend/tests/unit/services/test_external_camera.py b/backend/tests/unit/services/test_external_camera.py
index a404a273a..503abaa0f 100644
--- a/backend/tests/unit/services/test_external_camera.py
+++ b/backend/tests/unit/services/test_external_camera.py
@@ -4,7 +4,7 @@ Tests for the external camera service.
 These tests cover pure functions and frame parsing logic.
 """
 
-from unittest.mock import MagicMock, patch
+from unittest.mock import patch
 
 import pytest
 
diff --git a/backend/tests/unit/services/test_hms_errors.py b/backend/tests/unit/services/test_hms_errors.py
index 02fcb42b8..50f82789d 100644
--- a/backend/tests/unit/services/test_hms_errors.py
+++ b/backend/tests/unit/services/test_hms_errors.py
@@ -1,7 +1,5 @@
 """Tests for HMS error code translations."""
 
-import pytest
-
 from backend.app.services.hms_errors import HMS_ERROR_DESCRIPTIONS, get_error_description
 
 
diff --git a/backend/tests/unit/services/test_notification_service.py b/backend/tests/unit/services/test_notification_service.py
index 0d3d530ec..1f8eb492a 100644
--- a/backend/tests/unit/services/test_notification_service.py
+++ b/backend/tests/unit/services/test_notification_service.py
@@ -4,7 +4,6 @@ Tests event-based notifications and toggle behavior.
 """
 
 import json
-from datetime import datetime
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
diff --git a/backend/tests/unit/services/test_plate_detection.py b/backend/tests/unit/services/test_plate_detection.py
index 6896b73bd..49862a73b 100644
--- a/backend/tests/unit/services/test_plate_detection.py
+++ b/backend/tests/unit/services/test_plate_detection.py
@@ -1,7 +1,5 @@
 """Unit tests for plate detection service."""
 
-import tempfile
-from pathlib import Path
 from unittest.mock import MagicMock, patch
 
 import pytest
@@ -17,7 +15,12 @@ class TestPlateDetectionResult:
     def test_result_to_dict(self):
         """Verify PlateDetectionResult.to_dict() returns correct structure."""
         with patch.dict("sys.modules", {"cv2": cv2_mock, "numpy": np_mock}):
-            from backend.app.services.plate_detection import PlateDetectionResult
+            import importlib
+
+            import backend.app.services.plate_detection as pd_module
+
+            importlib.reload(pd_module)
+            PlateDetectionResult = pd_module.PlateDetectionResult
 
             result = PlateDetectionResult(
                 is_empty=True,
@@ -40,7 +43,12 @@ class TestPlateDetectionResult:
     def test_result_with_debug_image(self):
         """Verify has_debug_image is True when debug_image is provided."""
         with patch.dict("sys.modules", {"cv2": cv2_mock, "numpy": np_mock}):
-            from backend.app.services.plate_detection import PlateDetectionResult
+            import importlib
+
+            import backend.app.services.plate_detection as pd_module
+
+            importlib.reload(pd_module)
+            PlateDetectionResult = pd_module.PlateDetectionResult
 
             result = PlateDetectionResult(
                 is_empty=False,
@@ -57,7 +65,12 @@ class TestPlateDetectionResult:
     def test_result_needs_calibration(self):
         """Verify needs_calibration flag is preserved."""
         with patch.dict("sys.modules", {"cv2": cv2_mock, "numpy": np_mock}):
-            from backend.app.services.plate_detection import PlateDetectionResult
+            import importlib
+
+            import backend.app.services.plate_detection as pd_module
+
+            importlib.reload(pd_module)
+            PlateDetectionResult = pd_module.PlateDetectionResult
 
             result = PlateDetectionResult(
                 is_empty=True,
diff --git a/backend/tests/unit/services/test_printer_manager.py b/backend/tests/unit/services/test_printer_manager.py
index bd014c627..51e434207 100644
--- a/backend/tests/unit/services/test_printer_manager.py
+++ b/backend/tests/unit/services/test_printer_manager.py
@@ -3,9 +3,7 @@
 Tests printer connection management, status tracking, and print control.
 """
 
-import asyncio
-from datetime import datetime
-from unittest.mock import AsyncMock, MagicMock, PropertyMock, patch
+from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
 
diff --git a/backend/tests/unit/services/test_smart_plug_manager.py b/backend/tests/unit/services/test_smart_plug_manager.py
index 5d66c0da0..c5e23c4ca 100644
--- a/backend/tests/unit/services/test_smart_plug_manager.py
+++ b/backend/tests/unit/services/test_smart_plug_manager.py
@@ -4,7 +4,6 @@ These tests specifically target the auto-off behavior and toggle functionality
 that were identified as common regression points.
 """
 
-import asyncio
 from datetime import datetime
 from unittest.mock import AsyncMock, MagicMock, patch
 
diff --git a/backend/tests/unit/services/test_spoolman_tracking.py b/backend/tests/unit/services/test_spoolman_tracking.py
index 7e7467fff..0a854d79d 100644
--- a/backend/tests/unit/services/test_spoolman_tracking.py
+++ b/backend/tests/unit/services/test_spoolman_tracking.py
@@ -1,7 +1,5 @@
 """Unit tests for Spoolman tracking service helpers."""
 
-import pytest
-
 from backend.app.services.spoolman_tracking import (
     _resolve_global_tray_id,
     _resolve_spool_tag,
diff --git a/backend/tests/unit/services/test_stl_thumbnail.py b/backend/tests/unit/services/test_stl_thumbnail.py
index 31b6a0a19..22937c090 100644
--- a/backend/tests/unit/services/test_stl_thumbnail.py
+++ b/backend/tests/unit/services/test_stl_thumbnail.py
@@ -2,7 +2,6 @@
 
 import tempfile
 from pathlib import Path
-from unittest.mock import MagicMock, patch
 
 import pytest
 
diff --git a/backend/tests/unit/test_code_quality.py b/backend/tests/unit/test_code_quality.py
index d56a53af6..32a3b7aae 100644
--- a/backend/tests/unit/test_code_quality.py
+++ b/backend/tests/unit/test_code_quality.py
@@ -6,7 +6,6 @@ that could cause runtime errors but aren't caught by normal tests.
 """
 
 import ast
-import os
 from pathlib import Path
 
 import pytest
diff --git a/backend/tests/unit/test_log_error_detection.py b/backend/tests/unit/test_log_error_detection.py
index 93d0fa865..6793f94b8 100644
--- a/backend/tests/unit/test_log_error_detection.py
+++ b/backend/tests/unit/test_log_error_detection.py
@@ -5,10 +5,6 @@ These tests use the capture_logs fixture to detect runtime errors
 that might not cause test failures but indicate problems.
 """
 
-from unittest.mock import AsyncMock, MagicMock, patch
-
-import pytest
-
 
 class TestMQTTMessageProcessingNoErrors:
     """Verify MQTT message processing doesn't log errors."""
diff --git a/backend/tests/unit/test_plate_object_extraction.py b/backend/tests/unit/test_plate_object_extraction.py
index 303928529..00cf9d817 100644
--- a/backend/tests/unit/test_plate_object_extraction.py
+++ b/backend/tests/unit/test_plate_object_extraction.py
@@ -1,6 +1,5 @@
 """Unit tests for plate object extraction from 3MF model_settings.config."""
 
-import pytest
 from defusedxml import ElementTree as ET
 
 
diff --git a/backend/tests/unit/test_threemf_tools.py b/backend/tests/unit/test_threemf_tools.py
index 93008f5d8..b07bd749d 100644
--- a/backend/tests/unit/test_threemf_tools.py
+++ b/backend/tests/unit/test_threemf_tools.py
@@ -6,8 +6,6 @@ and cumulative layer usage lookup.
 
 import math
 
-import pytest
-
 from backend.app.utils.threemf_tools import (
     get_cumulative_usage_at_layer,
     mm_to_grams,
diff --git a/tests/e2e_toggle_persistence_test.py b/tests/e2e_toggle_persistence_test.py
index d0cf9fe2b..5992c8def 100644
--- a/tests/e2e_toggle_persistence_test.py
+++ b/tests/e2e_toggle_persistence_test.py
@@ -8,7 +8,7 @@ are properly persisted to the database and survive page reloads.
 import os
 import time
 
-from playwright.sync_api import expect, sync_playwright
+from playwright.sync_api import sync_playwright
 
 BASE_URL = os.environ.get("BAMBUDDY_URL", "http://localhost:8000")