diff --git a/infra/scripts/post-provision/seed_knowledge_bases.py b/infra/scripts/post-provision/seed_knowledge_bases.py
index 5505196a0..4f6bf0205 100644
--- a/infra/scripts/post-provision/seed_knowledge_bases.py
+++ b/infra/scripts/post-provision/seed_knowledge_bases.py
@@ -21,7 +21,6 @@
   - The caller needs "Search Service Contributor" role on the search service.
 """
 
-import json
 import os
 import sys
 from pathlib import Path
@@ -37,9 +36,12 @@
 SEARCH_ENDPOINT = os.environ.get("AZURE_AI_SEARCH_ENDPOINT", "").rstrip("/")
 AI_SERVICES_ENDPOINT = os.environ.get("AZURE_OPENAI_ENDPOINT", "").rstrip("/")
 
-if not SEARCH_ENDPOINT:
-    print("ERROR: AZURE_AI_SEARCH_ENDPOINT must be set.")
-    sys.exit(1)
+
+def _validate_required_env() -> None:
+    """Validate required environment variables; exit(1) if missing."""
+    if not SEARCH_ENDPOINT:
+        print("ERROR: AZURE_AI_SEARCH_ENDPOINT must be set.")
+        sys.exit(1)
 
 _SEARCH_SCOPE = "https://search.azure.com/.default"
 
@@ -384,6 +386,7 @@ def _parse_only_filter() -> set[str] | None:
 
 def main() -> None:
     """Provision all knowledge bases."""
+    _validate_required_env()
     print(f"Search endpoint: {SEARCH_ENDPOINT}")
     print(f"AI services endpoint: {AI_SERVICES_ENDPOINT or '(not set — KB will have no model)'}")
 
diff --git a/src/backend/api/router.py b/src/backend/api/router.py
index f683e2dab..2297e9571 100644
--- a/src/backend/api/router.py
+++ b/src/backend/api/router.py
@@ -127,8 +127,13 @@ async def _heartbeat() -> None:
             heartbeat_task.cancel()
             try:
                 await heartbeat_task
-            except (asyncio.CancelledError, Exception):
+            except asyncio.CancelledError:
+                # Expected: we just cancelled the heartbeat task above.
                 pass
+            except Exception as e:
+                logging.debug(
+                    f"Unexpected error awaiting cancelled heartbeat task for user {user_id}: {e}"
+                )
             await connection_config.close_connection(process_id=process_id)
 
 
@@ -428,7 +433,9 @@ async def run_orchestration_task():
                 # Give the cancelled task a chance to clean up
                 await asyncio.sleep(0)
             except Exception:
-                pass
+                logger.exception(
+                    "Failed to cancel prior orchestration task for user '%s'", user_id
+                )
             orchestration_config.active_tasks.pop(user_id, None)
 
         # Schedule new task and register it so subsequent requests can cancel it
diff --git a/src/backend/orchestration/orchestration_manager.py b/src/backend/orchestration/orchestration_manager.py
index cb417465d..77846e39f 100644
--- a/src/backend/orchestration/orchestration_manager.py
+++ b/src/backend/orchestration/orchestration_manager.py
@@ -736,8 +736,12 @@ def _get_team_agent_names(workflow) -> list[str]:
             ]
             if names:
                 return names
-        except Exception:
-            pass
+        except Exception as exc:
+            OrchestrationManager.logger.debug(
+                "Failed to read executor names from workflow; falling back to team config: %s",
+                exc,
+                exc_info=True,
+            )
 
         team_config = getattr(workflow, "_team_config", None)
         return [
@@ -914,7 +918,6 @@ async def _handle_tool_approvals(
         Returns:
             A ``{request_id: approval_response}`` dict.
         """
-        import json
         import threading
 
         from tools.clarification_tool import store_answer
diff --git a/src/backend/orchestration/plan_review_helpers.py b/src/backend/orchestration/plan_review_helpers.py
index 72dd820b8..efb2d536e 100644
--- a/src/backend/orchestration/plan_review_helpers.py
+++ b/src/backend/orchestration/plan_review_helpers.py
@@ -95,7 +95,6 @@ def get_magentic_prompt_kwargs(
             "is INVALID — regenerate it\nuntil every listed agent appears as a step.\n"
         )
 
-
     scope_policy = """
 
 TEAM SCOPE POLICY (CRITICAL — EVALUATE THIS FIRST, BEFORE ANY OTHER RULE):
diff --git a/src/tests/agents/test_agent_template_integration.py b/src/tests/agents/test_agent_template_integration.py
index 15a22b883..4e4f1d0b0 100644
--- a/src/tests/agents/test_agent_template_integration.py
+++ b/src/tests/agents/test_agent_template_integration.py
@@ -27,7 +27,6 @@
 from pathlib import Path
 
 import pytest
-import pytest_asyncio
 
 # ---------------------------------------------------------------------------
 # Make sure 'src/backend' is on the path (covers running from repo root and
diff --git a/src/tests/backend/agents/test_agent_factory.py b/src/tests/backend/agents/test_agent_factory.py
index 2444408e1..77f03d62b 100644
--- a/src/tests/backend/agents/test_agent_factory.py
+++ b/src/tests/backend/agents/test_agent_factory.py
@@ -13,7 +13,7 @@
 import logging
 import sys
 from types import SimpleNamespace
-from unittest.mock import AsyncMock, Mock, patch
+from unittest.mock import AsyncMock, Mock
 
 import pytest
 
diff --git a/src/tests/backend/common/database/test_database_base.py b/src/tests/backend/common/database/test_database_base.py
index 72bce96b0..e0b7b75b8 100644
--- a/src/tests/backend/common/database/test_database_base.py
+++ b/src/tests/backend/common/database/test_database_base.py
@@ -3,7 +3,7 @@
 import os
 import sys
 from typing import Any, Dict, List, Optional, Type
-from unittest.mock import AsyncMock, Mock, patch
+from unittest.mock import Mock
 
 import pytest
 
diff --git a/src/tests/backend/common/utils/test_agent_utils.py b/src/tests/backend/common/utils/test_agent_utils.py
index 91d378eeb..d8e8978d4 100644
--- a/src/tests/backend/common/utils/test_agent_utils.py
+++ b/src/tests/backend/common/utils/test_agent_utils.py
@@ -28,10 +28,8 @@
 sys.modules['common.models'] = Mock()
 sys.modules['common.models.messages'] = Mock()
 
-import pytest
-
 from backend.common.database.database_base import DatabaseBase
-from backend.common.models.messages import (CurrentTeamAgent, DataType,
+from backend.common.models.messages import (CurrentTeamAgent,
                                             TeamConfiguration)
 from backend.common.utils.agent_utils import (generate_assistant_id,
                                               get_database_team_agent_id)
diff --git a/src/tests/backend/common/utils/test_event_utils.py b/src/tests/backend/common/utils/test_event_utils.py
index 3696e79f5..cc3517caa 100644
--- a/src/tests/backend/common/utils/test_event_utils.py
+++ b/src/tests/backend/common/utils/test_event_utils.py
@@ -4,7 +4,7 @@
 import os
 import sys
 from pathlib import Path
-from unittest.mock import MagicMock, Mock, patch
+from unittest.mock import Mock, patch
 
 import pytest
 
diff --git a/src/tests/backend/middleware/test_health_check.py b/src/tests/backend/middleware/test_health_check.py
index 5841a1cb0..e5d2bd36c 100644
--- a/src/tests/backend/middleware/test_health_check.py
+++ b/src/tests/backend/middleware/test_health_check.py
@@ -1,7 +1,5 @@
 """Unit tests for backend.middleware.health_check module."""
-import asyncio
-import logging
-from unittest.mock import AsyncMock, MagicMock, Mock, patch
+from unittest.mock import AsyncMock, Mock, patch
 
 import pytest
 
diff --git a/src/tests/backend/models/test_messages.py b/src/tests/backend/models/test_messages.py
index 725069b70..282789f70 100644
--- a/src/tests/backend/models/test_messages.py
+++ b/src/tests/backend/models/test_messages.py
@@ -5,8 +5,6 @@
 import os
 import sys
 
-import pytest
-
 # backend/models/messages.py has internal imports from common.models.messages
 # and models.plan_models using paths relative to src/backend/.  Add src/backend/
 # to sys.path so those internal imports resolve when we load backend.models.messages.
@@ -24,7 +22,7 @@
                                      ReplanApprovalResponse,
                                      UserClarificationRequest,
                                      UserClarificationResponse)
-from backend.models.plan_models import MPlan, MStep, PlanStatus
+from backend.models.plan_models import MPlan, PlanStatus
 
 
 class TestAgentMessage:
diff --git a/src/tests/backend/orchestration/test_orchestration_manager.py b/src/tests/backend/orchestration/test_orchestration_manager.py
index 15245883e..dd8fe5225 100644
--- a/src/tests/backend/orchestration/test_orchestration_manager.py
+++ b/src/tests/backend/orchestration/test_orchestration_manager.py
@@ -7,11 +7,10 @@
 - _process_event_stream() — event dispatch
 """
 
-import asyncio
 import logging
 import os
 import sys
-from unittest.mock import AsyncMock, MagicMock, Mock, patch
+from unittest.mock import AsyncMock, Mock, patch
 
 import pytest
 
diff --git a/src/tests/backend/services/test_mcp_service.py b/src/tests/backend/services/test_mcp_service.py
index 666b92240..44030fb17 100644
--- a/src/tests/backend/services/test_mcp_service.py
+++ b/src/tests/backend/services/test_mcp_service.py
@@ -3,7 +3,7 @@
 
 import os
 import sys
-from unittest.mock import AsyncMock, MagicMock, patch
+from unittest.mock import MagicMock, patch
 
 import pytest
 from aiohttp import ClientError
diff --git a/src/tests/backend/test_app.py b/src/tests/backend/test_app.py
index 8784d276e..c16e83d6b 100644
--- a/src/tests/backend/test_app.py
+++ b/src/tests/backend/test_app.py
@@ -13,7 +13,7 @@
 import pytest
 import sys
 import os
-from unittest.mock import Mock, AsyncMock, MagicMock, patch, NonCallableMock
+from unittest.mock import Mock, AsyncMock, MagicMock, patch
 
 # Environment variables are set by conftest.py, but ensure they're available
 os.environ.setdefault("APPLICATIONINSIGHTS_CONNECTION_STRING", "InstrumentationKey=test-key-12345")
@@ -47,7 +47,6 @@
         del sys.modules[_ma_key]
 
 # Mock external dependencies that may not be installed in test environment
-from fastapi import APIRouter
 
 # Mock azure.monitor.opentelemetry module
 mock_azure_monitor_module = ModuleType('configure_azure_monitor')
diff --git a/test_mcp_tools.py b/test_mcp_tools.py
index 39fcaf94e..758bdd7f1 100644
--- a/test_mcp_tools.py
+++ b/test_mcp_tools.py
@@ -1,5 +1,6 @@
 """Quick test to list MCP tools on /hr/mcp."""
 import json
+import sys
 
 import httpx
 
@@ -31,7 +32,7 @@
 
 if not sid:
     print("No session ID, aborting")
-    exit(1)
+    sys.exit(1)
 
 # 2. List tools
 HEADERS["mcp-session-id"] = sid