diff --git a/app/routes/api_v1_time_entries.py b/app/routes/api_v1_time_entries.py
index bacc002b..e5bd07bd 100644
--- a/app/routes/api_v1_time_entries.py
+++ b/app/routes/api_v1_time_entries.py
@@ -6,7 +6,7 @@ Sub-blueprint for /api/v1/time-entries and /api/v1/timer/*.
 from flask import Blueprint, g, jsonify, request
 from marshmallow import ValidationError
 
-from app.routes.api_v1_common import _parse_date_range, paginate_query, parse_datetime
+from app.routes.api_v1_common import _parse_date_range, paginate_query
 from app.schemas.time_entry_schema import TimeEntryCreateSchema, TimeEntryUpdateSchema
 from app.utils.api_auth import require_api_token
 from app.utils.api_responses import (
@@ -16,7 +16,9 @@ from app.utils.api_responses import (
     validation_error_response,
 )
 
-api_v1_time_entries_bp = Blueprint("api_v1_time_entries", __name__, url_prefix="/api/v1")
+api_v1_time_entries_bp = Blueprint(
+    "api_v1_time_entries", __name__, url_prefix="/api/v1"
+)
 
 
 @api_v1_time_entries_bp.route("/time-entries", methods=["GET"])
@@ -50,7 +52,9 @@ def list_time_entries():
     per_page = request.args.get("per_page", 50, type=int)
 
     query = TimeEntry.query.options(
-        joinedload(TimeEntry.project), joinedload(TimeEntry.user), joinedload(TimeEntry.task)
+        joinedload(TimeEntry.project),
+        joinedload(TimeEntry.user),
+        joinedload(TimeEntry.task),
     )
     if project_id:
         query = query.filter(TimeEntry.project_id == project_id)
@@ -67,7 +71,12 @@ def list_time_entries():
 
     query = query.order_by(TimeEntry.start_time.desc())
     result = paginate_query(query, page, per_page)
-    return jsonify({"time_entries": [e.to_dict() for e in result["items"]], "pagination": result["pagination"]})
+    return jsonify(
+        {
+            "time_entries": [e.to_dict() for e in result["items"]],
+            "pagination": result["pagination"],
+        }
+    )
 
 
 @api_v1_time_entries_bp.route("/time-entries/<int:entry_id>", methods=["GET"])
@@ -79,7 +88,11 @@ def get_time_entry(entry_id):
     from app.models import TimeEntry
 
     entry = (
-        TimeEntry.query.options(joinedload(TimeEntry.project), joinedload(TimeEntry.user), joinedload(TimeEntry.task))
+        TimeEntry.query.options(
+            joinedload(TimeEntry.project),
+            joinedload(TimeEntry.user),
+            joinedload(TimeEntry.task),
+        )
         .filter_by(id=entry_id)
         .first_or_404()
     )
@@ -92,7 +105,9 @@ def get_time_entry(entry_id):
 @require_api_token("write:time_entries")
 def import_time_entries_csv():
     """Import time entries from CSV (header row required)."""
-    from app.services.time_entry_csv_import_service import import_time_entries_from_csv_text
+    from app.services.time_entry_csv_import_service import (
+        import_time_entries_from_csv_text,
+    )
 
     csv_text = ""
     if request.files and request.files.get("file"):
@@ -104,7 +119,9 @@ def import_time_entries_csv():
     else:
         csv_text = request.get_data(as_text=True) or ""
 
-    result, status = import_time_entries_from_csv_text(csv_text, user_id=g.api_user.id, is_admin=g.api_user.is_admin)
+    result, status = import_time_entries_from_csv_text(
+        csv_text, user_id=g.api_user.id, is_admin=g.api_user.is_admin
+    )
     return jsonify(result), status
 
 
@@ -128,11 +145,17 @@ def bulk_time_entries():
         try:
             ids.append(int(eid))
         except (TypeError, ValueError):
-            return validation_error_response(errors={"entry_ids": ["All entry ids must be integers"]})
-    result = apply_bulk_time_entry_actions(ids, action, value, user_id=g.api_user.id, is_admin=g.api_user.is_admin)
+            return validation_error_response(
+                errors={"entry_ids": ["All entry ids must be integers"]}
+            )
+    result = apply_bulk_time_entry_actions(
+        ids, action, value, user_id=g.api_user.id, is_admin=g.api_user.is_admin
+    )
     if not result.get("success"):
         code = result.get("http_status", 400)
-        return error_response(result.get("error", "Bulk operation failed"), status_code=code)
+        return error_response(
+            result.get("error", "Bulk operation failed"), status_code=code
+        )
     return jsonify({"success": True, "affected": result.get("affected", 0)})
 
 
@@ -151,7 +174,9 @@ def create_time_entry():
 
     idem_key = normalize_idempotency_key(request.headers.get("Idempotency-Key"))
     if idem_key:
-        existing = lookup_idempotent_response(g.api_token.id, SCOPE_POST_TIME_ENTRY, idem_key)
+        existing = lookup_idempotent_response(
+            g.api_token.id, SCOPE_POST_TIME_ENTRY, idem_key
+        )
         if existing:
             status_code, body_json = existing
             return replay_response(status_code, body_json)
@@ -193,9 +218,15 @@ def create_time_entry():
         from app.models import Activity
         from app.utils.audit import get_request_info
 
-        entity_name = entry.project.name if entry.project else (entry.client.name if entry.client else "Unknown")
+        entity_name = (
+            entry.project.name
+            if entry.project
+            else (entry.client.name if entry.client else "Unknown")
+        )
         task_name = entry.task.name if entry.task else None
-        duration_formatted = entry.duration_formatted if hasattr(entry, "duration_formatted") else "0:00"
+        duration_formatted = (
+            entry.duration_formatted if hasattr(entry, "duration_formatted") else "0:00"
+        )
         ip_address, user_agent, _ = get_request_info()
         Activity.log(
             user_id=g.api_user.id,
@@ -211,13 +242,18 @@ def create_time_entry():
                 "client_name": entry.client.name if entry.client else None,
                 "task_name": task_name,
                 "duration_formatted": duration_formatted,
-                "duration_hours": entry.duration_hours if hasattr(entry, "duration_hours") else None,
+                "duration_hours": entry.duration_hours
+                if hasattr(entry, "duration_hours")
+                else None,
             },
             ip_address=ip_address,
             user_agent=user_agent,
         )
 
-    payload = {"message": "Time entry created successfully", "time_entry": result["entry"].to_dict()}
+    payload = {
+        "message": "Time entry created successfully",
+        "time_entry": result["entry"].to_dict(),
+    }
     resp = jsonify(payload)
     resp.status_code = 201
     if idem_key:
@@ -226,10 +262,14 @@ def create_time_entry():
         from app import db
 
         try:
-            store_idempotent_response(g.api_token.id, SCOPE_POST_TIME_ENTRY, idem_key, 201, payload)
+            store_idempotent_response(
+                g.api_token.id, SCOPE_POST_TIME_ENTRY, idem_key, 201, payload
+            )
         except IntegrityError:
             db.session.rollback()
-            existing = lookup_idempotent_response(g.api_token.id, SCOPE_POST_TIME_ENTRY, idem_key)
+            existing = lookup_idempotent_response(
+                g.api_token.id, SCOPE_POST_TIME_ENTRY, idem_key
+            )
             if existing:
                 status_code, body_json = existing
                 return replay_response(status_code, body_json)
@@ -286,7 +326,11 @@ def update_time_entry(entry_id):
         from app.models import Activity
         from app.utils.audit import get_request_info
 
-        entity_name = entry.project.name if entry.project else (entry.client.name if entry.client else "Unknown")
+        entity_name = (
+            entry.project.name
+            if entry.project
+            else (entry.client.name if entry.client else "Unknown")
+        )
         task_name = entry.task.name if entry.task else None
         ip_address, user_agent, _ = get_request_info()
         Activity.log(
@@ -295,7 +339,8 @@ def update_time_entry(entry_id):
             entity_type="time_entry",
             entity_id=entry.id,
             entity_name=f"{entity_name}" + (f" - {task_name}" if task_name else ""),
-            description=f"Updated time entry for {entity_name}" + (f" - {task_name}" if task_name else ""),
+            description=f"Updated time entry for {entity_name}"
+            + (f" - {task_name}" if task_name else ""),
             extra_data={
                 "project_name": entry.project.name if entry.project else None,
                 "client_name": entry.client.name if entry.client else None,
@@ -305,7 +350,12 @@ def update_time_entry(entry_id):
             user_agent=user_agent,
         )
 
-    return jsonify({"message": "Time entry updated successfully", "time_entry": result["entry"].to_dict()})
+    return jsonify(
+        {
+            "message": "Time entry updated successfully",
+            "time_entry": result["entry"].to_dict(),
+        }
+    )
 
 
 @api_v1_time_entries_bp.route("/time-entries/<int:entry_id>", methods=["DELETE"])
@@ -314,7 +364,8 @@ def delete_time_entry(entry_id):
     """Delete a time entry."""
     from app.services import TimeTrackingService
 
-    data = request.get_json() or {}
+    # Optional body — tolerate DELETE with no Content-Type set
+    data = request.get_json(silent=True) or {}
     reason = data.get("reason")
     time_tracking_service = TimeTrackingService()
     result = time_tracking_service.delete_entry(
@@ -379,7 +430,9 @@ def start_timer():
             result.get("message", "Could not start timer"),
             status_code=400,
         )
-    return jsonify({"message": "Timer started successfully", "timer": result["timer"].to_dict()}), 201
+    return jsonify(
+        {"message": "Timer started successfully", "timer": result["timer"].to_dict()}
+    ), 201
 
 
 @api_v1_time_entries_bp.route("/timer/pause", methods=["POST"])
@@ -413,7 +466,9 @@ def resume_timer():
             error_code=result.get("error", "resume_failed"),
             status_code=400,
         )
-    return jsonify({"message": "Timer resumed", "time_entry": result["entry"].to_dict()})
+    return jsonify(
+        {"message": "Timer resumed", "time_entry": result["entry"].to_dict()}
+    )
 
 
 @api_v1_time_entries_bp.route("/timer/stop", methods=["POST"])
@@ -430,11 +485,18 @@ def stop_timer():
             status_code=400,
         )
     time_tracking_service = TimeTrackingService()
-    result = time_tracking_service.stop_timer(user_id=g.api_user.id, entry_id=active_timer.id)
+    result = time_tracking_service.stop_timer(
+        user_id=g.api_user.id, entry_id=active_timer.id
+    )
     if not result.get("success"):
         return error_response(
             result.get("message", "Could not stop timer"),
             error_code=result.get("error", "stop_failed"),
             status_code=400,
         )
-    return jsonify({"message": "Timer stopped successfully", "time_entry": result["entry"].to_dict()})
+    return jsonify(
+        {
+            "message": "Timer stopped successfully",
+            "time_entry": result["entry"].to_dict(),
+        }
+    )
diff --git a/tests/test_client_single_simplification.py b/tests/test_client_single_simplification.py
index 0d1c33fb..fbe8b1d3 100644
--- a/tests/test_client_single_simplification.py
+++ b/tests/test_client_single_simplification.py
@@ -13,7 +13,9 @@ from flask import url_for
 
 @pytest.mark.integration
 @pytest.mark.routes
-def test_manual_entry_shows_single_client_prefilled(authenticated_client, app, user, test_client):
+def test_manual_entry_shows_single_client_prefilled(
+    authenticated_client, app, user, test_client
+):
     """When only one client exists, manual entry form shows pre-filled grayed-out client."""
     with app.app_context():
         # Ensure exactly one active client (test_client from fixture)
@@ -35,15 +37,17 @@ def test_manual_entry_shows_single_client_prefilled(authenticated_client, app, u
 
 @pytest.mark.integration
 @pytest.mark.routes
-def test_manual_entry_shows_select_when_multiple_clients(authenticated_client, app, user, test_client):
+def test_manual_entry_shows_select_when_multiple_clients(
+    authenticated_client, app, user, test_client
+):
     """When multiple clients exist, manual entry form shows normal client select."""
     with app.app_context():
         # Add a second client
         second = Client(
             name="Second Client",
             email="second@example.com",
-            status="active",
         )
+        second.status = "active"
         db.session.add(second)
         db.session.commit()
 
@@ -55,6 +59,6 @@ def test_manual_entry_shows_select_when_multiple_clients(authenticated_client, a
         html = response.get_data(as_text=True)
 
         # Should have normal select, not single-client hidden + disabled
-        assert '<select' in html
+        assert "<select" in html
         assert 'id="client_id"' in html or 'name="client_id"' in html
         assert "Select a client" in html or "client" in html.lower()
diff --git a/tests/test_routes/test_api_v1_expenses_complete.py b/tests/test_routes/test_api_v1_expenses_complete.py
index 4cf2a145..73f0ddd9 100644
--- a/tests/test_routes/test_api_v1_expenses_complete.py
+++ b/tests/test_routes/test_api_v1_expenses_complete.py
@@ -8,7 +8,7 @@ pytestmark = [pytest.mark.api, pytest.mark.integration]
 
 from datetime import date
 from decimal import Decimal
-from app.models import Expense, Project, ApiToken
+from app.models import Expense, ApiToken, User
 
 
 class TestAPIExpensesComplete:
@@ -18,7 +18,9 @@ class TestAPIExpensesComplete:
     def api_token(self, app, user):
         """Create an API token for testing"""
         token, plain_token = ApiToken.create_token(
-            user_id=user.id, name="Test API Token", scopes="read:expenses,write:expenses"
+            user_id=user.id,
+            name="Test API Token",
+            scopes="read:expenses,write:expenses",
         )
         from app import db
 
@@ -34,7 +36,9 @@ class TestAPIExpensesComplete:
         test_client.environ_base["HTTP_AUTHORIZATION"] = f"Bearer {plain_token}"
         return test_client
 
-    def test_list_expenses_with_filters(self, app, client_with_token, user, project, expense):
+    def test_list_expenses_with_filters(
+        self, app, client_with_token, user, project, expense
+    ):
         """Test list_expenses with various filters"""
         # Filter by project
         response = client_with_token.get(f"/api/v1/expenses?project_id={project.id}")
@@ -109,7 +113,7 @@ class TestAPIExpensesComplete:
 
     def test_expense_permissions(self, app, user, project):
         """Test expense access permissions"""
-        from app.models import Expense, ApiToken
+        from app.models import ApiToken
         from app import db
 
         # Create expense for another user
@@ -127,7 +131,9 @@ class TestAPIExpensesComplete:
 
             # Create token for first user
             token, plain_token = ApiToken.create_token(
-                user_id=user.id, name="Test Token", scopes="read:expenses,write:expenses"
+                user_id=user.id,
+                name="Test Token",
+                scopes="read:expenses,write:expenses",
             )
             db.session.add(token)
             db.session.commit()
diff --git a/tests/test_utils/test_api_auth_enhanced.py b/tests/test_utils/test_api_auth_enhanced.py
index ab572692..89bb22c6 100644
--- a/tests/test_utils/test_api_auth_enhanced.py
+++ b/tests/test_utils/test_api_auth_enhanced.py
@@ -7,10 +7,13 @@ import pytest
 pytestmark = [pytest.mark.unit, pytest.mark.utils]
 
 from datetime import datetime, timedelta
-from unittest.mock import Mock, patch, MagicMock
 from flask import Flask, g
 from app.models import ApiToken, User
-from app.utils.api_auth import authenticate_token, require_api_token, extract_token_from_request
+from app.utils.api_auth import (
+    authenticate_token,
+    require_api_token,
+    extract_token_from_request,
+)
 from app import db
 
 
@@ -19,27 +22,28 @@ class TestExtractToken:
 
     def test_extract_from_bearer_header(self):
         """Test extracting token from Bearer Authorization header"""
-        from flask import Flask, request
 
         app = Flask(__name__)
 
-        with app.test_request_context(headers={"Authorization": "Bearer tt_testtoken123"}):
+        with app.test_request_context(
+            headers={"Authorization": "Bearer tt_testtoken123"}
+        ):
             token = extract_token_from_request()
             assert token == "tt_testtoken123"
 
     def test_extract_from_token_header(self):
         """Test extracting token from Token Authorization header"""
-        from flask import Flask, request
 
         app = Flask(__name__)
 
-        with app.test_request_context(headers={"Authorization": "Token tt_testtoken123"}):
+        with app.test_request_context(
+            headers={"Authorization": "Token tt_testtoken123"}
+        ):
             token = extract_token_from_request()
             assert token == "tt_testtoken123"
 
     def test_extract_from_api_key_header(self):
         """Test extracting token from X-API-Key header"""
-        from flask import Flask, request
 
         app = Flask(__name__)
 
@@ -49,7 +53,6 @@ class TestExtractToken:
 
     def test_extract_none_when_missing(self):
         """Test that None is returned when no token is present"""
-        from flask import Flask, request
 
         app = Flask(__name__)
 
@@ -64,7 +67,8 @@ class TestAuthenticateToken:
     @pytest.fixture
     def sample_user(self, app):
         """Create a sample user for testing"""
-        user = User(username="testuser", is_active=True)
+        user = User(username="testuser")
+        user.is_active = True
         db.session.add(user)
         db.session.commit()
         return user
@@ -73,7 +77,10 @@ class TestAuthenticateToken:
     def sample_token(self, app, sample_user):
         """Create a sample API token"""
         token, plain_token = ApiToken.create_token(
-            user_id=sample_user.id, name="Test Token", scopes="read:projects", expires_days=30
+            user_id=sample_user.id,
+            name="Test Token",
+            scopes="read:projects",
+            expires_days=30,
         )
         db.session.add(token)
         db.session.commit()
@@ -83,7 +90,7 @@ class TestAuthenticateToken:
         """Test authentication with valid token"""
         token, plain_token = sample_token
 
-        with app.test_request_context(remote_addr="127.0.0.1"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "127.0.0.1"}):
             user, api_token, error = authenticate_token(plain_token)
 
             assert user is not None
@@ -95,13 +102,15 @@ class TestAuthenticateToken:
     def test_authenticate_expired_token(self, app, sample_user):
         """Test authentication with expired token"""
         token, plain_token = ApiToken.create_token(
-            user_id=sample_user.id, name="Expired Token", expires_days=-1  # Expired
+            user_id=sample_user.id,
+            name="Expired Token",
+            expires_days=-1,  # Expired
         )
         token.expires_at = datetime.utcnow() - timedelta(days=1)
         db.session.add(token)
         db.session.commit()
 
-        with app.test_request_context(remote_addr="127.0.0.1"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "127.0.0.1"}):
             user, api_token, error = authenticate_token(plain_token)
 
             assert user is None
@@ -114,7 +123,7 @@ class TestAuthenticateToken:
         token.is_active = False
         db.session.commit()
 
-        with app.test_request_context(remote_addr="127.0.0.1"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "127.0.0.1"}):
             user, api_token, error = authenticate_token(plain_token)
 
             assert user is None
@@ -130,7 +139,7 @@ class TestAuthenticateToken:
         db.session.add(token)
         db.session.commit()
 
-        with app.test_request_context(remote_addr="127.0.0.1"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "127.0.0.1"}):
             user, api_token, error = authenticate_token(plain_token)
 
             assert user is not None
@@ -146,7 +155,7 @@ class TestAuthenticateToken:
         db.session.add(token)
         db.session.commit()
 
-        with app.test_request_context(remote_addr="10.0.0.1"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "10.0.0.1"}):
             user, api_token, error = authenticate_token(plain_token)
 
             assert user is None
@@ -155,12 +164,14 @@ class TestAuthenticateToken:
 
     def test_authenticate_with_cidr_block(self, app, sample_user):
         """Test authentication with CIDR block in whitelist"""
-        token, plain_token = ApiToken.create_token(user_id=sample_user.id, name="CIDR Token", scopes="read:projects")
+        token, plain_token = ApiToken.create_token(
+            user_id=sample_user.id, name="CIDR Token", scopes="read:projects"
+        )
         token.ip_whitelist = "192.168.1.0/24"
         db.session.add(token)
         db.session.commit()
 
-        with app.test_request_context(remote_addr="192.168.1.100"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "192.168.1.100"}):
             user, api_token, error = authenticate_token(plain_token)
 
             assert user is not None
@@ -169,7 +180,7 @@ class TestAuthenticateToken:
 
     def test_authenticate_invalid_token_format(self, app):
         """Test authentication with invalid token format"""
-        with app.test_request_context(remote_addr="127.0.0.1"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "127.0.0.1"}):
             user, api_token, error = authenticate_token("invalid_token")
 
             assert user is None
@@ -180,7 +191,7 @@ class TestAuthenticateToken:
         """Test authentication with non-existent token"""
         fake_token = "tt_" + "x" * 32
 
-        with app.test_request_context(remote_addr="127.0.0.1"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "127.0.0.1"}):
             user, api_token, error = authenticate_token(fake_token)
 
             assert user is None
@@ -193,7 +204,7 @@ class TestAuthenticateToken:
         token.user.is_active = False
         db.session.commit()
 
-        with app.test_request_context(remote_addr="127.0.0.1"):
+        with app.test_request_context(environ_overrides={"REMOTE_ADDR": "127.0.0.1"}):
             user, api_token, error = authenticate_token(plain_token)
 
             assert user is None
@@ -220,12 +231,16 @@ class TestRequireApiToken:
 
         return app
 
-    def test_protected_route_with_valid_token(self, app_with_routes, sample_user, sample_token):
+    def test_protected_route_with_valid_token(
+        self, app_with_routes, sample_user, sample_token
+    ):
         """Test accessing protected route with valid token"""
         token, plain_token = sample_token
 
         with app_with_routes.test_client() as client:
-            response = client.get("/test/protected", headers={"Authorization": f"Bearer {plain_token}"})
+            response = client.get(
+                "/test/protected", headers={"Authorization": f"Bearer {plain_token}"}
+            )
 
             assert response.status_code == 200
             data = response.get_json()
@@ -242,16 +257,22 @@ class TestRequireApiToken:
             assert "error" in data
             assert "Authentication required" in data["error"]
 
-    def test_protected_route_with_insufficient_scope(self, app_with_routes, sample_user):
+    def test_protected_route_with_insufficient_scope(
+        self, app_with_routes, sample_user
+    ):
         """Test accessing protected route with insufficient scope"""
         token, plain_token = ApiToken.create_token(
-            user_id=sample_user.id, name="Limited Token", scopes="read:time_entries"  # Different scope
+            user_id=sample_user.id,
+            name="Limited Token",
+            scopes="read:time_entries",  # Different scope
         )
         db.session.add(token)
         db.session.commit()
 
         with app_with_routes.test_client() as client:
-            response = client.get("/test/protected", headers={"Authorization": f"Bearer {plain_token}"})
+            response = client.get(
+                "/test/protected", headers={"Authorization": f"Bearer {plain_token}"}
+            )
 
             assert response.status_code == 403
             data = response.get_json()
@@ -261,13 +282,17 @@ class TestRequireApiToken:
     def test_protected_route_with_wildcard_scope(self, app_with_routes, sample_user):
         """Test accessing protected route with wildcard scope"""
         token, plain_token = ApiToken.create_token(
-            user_id=sample_user.id, name="Admin Token", scopes="read:*"  # Wildcard scope
+            user_id=sample_user.id,
+            name="Admin Token",
+            scopes="read:*",  # Wildcard scope
         )
         db.session.add(token)
         db.session.commit()
 
         with app_with_routes.test_client() as client:
-            response = client.get("/test/protected", headers={"Authorization": f"Bearer {plain_token}"})
+            response = client.get(
+                "/test/protected", headers={"Authorization": f"Bearer {plain_token}"}
+            )
 
             assert response.status_code == 200
             data = response.get_json()