diff --git a/backend/Makefile b/backend/Makefile
index 85cf11b..640390b 100644
--- a/backend/Makefile
+++ b/backend/Makefile
@@ -1,5 +1,13 @@
 .PHONY: help lint lint-fix format format-check type-check test test-cov validate clean install-dev
 
+# Virtual environment binaries
+VENV_BIN = .venv/bin
+PYTHON = $(VENV_BIN)/python
+PIP = $(VENV_BIN)/pip
+PYTEST = $(VENV_BIN)/pytest
+RUFF = $(VENV_BIN)/ruff
+MYPY = $(VENV_BIN)/mypy
+
 # Default target
 help:
 	@echo "🚀 FastAPI Backend - Development Commands"
@@ -26,23 +34,23 @@ help:
 
 lint:
 	@echo "🔍 Running Ruff linter..."
-	@ruff check app/ tests/
+	@$(RUFF) check app/ tests/
 
 lint-fix:
 	@echo "🔧 Running Ruff linter with auto-fix..."
-	@ruff check --fix app/ tests/
+	@$(RUFF) check --fix app/ tests/
 
 format:
 	@echo "✨ Formatting code with Ruff..."
-	@ruff format app/ tests/
+	@$(RUFF) format app/ tests/
 
 format-check:
 	@echo "📋 Checking code formatting..."
-	@ruff format --check app/ tests/
+	@$(RUFF) format --check app/ tests/
 
 type-check:
 	@echo "🔎 Running mypy type checking..."
-	@mypy app/
+	@$(MYPY) app/
 
 validate: lint format-check type-check
 	@echo "✅ All quality checks passed!"
@@ -53,11 +61,11 @@ validate: lint format-check type-check
 
 test:
 	@echo "🧪 Running tests..."
-	@IS_TEST=True pytest
+	@IS_TEST=True PYTHONPATH=. $(PYTEST)
 
 test-cov:
 	@echo "🧪 Running tests with coverage..."
-	@IS_TEST=True pytest --cov=app --cov-report=term-missing --cov-report=html -n 0
+	@IS_TEST=True PYTHONPATH=. $(PYTEST) --cov=app --cov-report=term-missing --cov-report=html -n 0
 	@echo "📊 Coverage report generated in htmlcov/index.html"
 
 # ============================================================================
@@ -66,7 +74,7 @@ test-cov:
 
 install-dev:
 	@echo "📦 Installing development dependencies..."
-	@pip install -r requirements.txt
+	@$(PIP) install -r requirements.txt
 	@echo "✅ Development environment ready!"
 
 clean:
diff --git a/backend/app/crud/session.py b/backend/app/crud/session.py
index 528a7ce..efa139b 100755
--- a/backend/app/crud/session.py
+++ b/backend/app/crud/session.py
@@ -309,7 +309,7 @@ class CRUDSession(CRUDBase[UserSession, SessionCreate, SessionUpdate]):
             # Use bulk DELETE with WHERE clause - single query
             stmt = delete(UserSession).where(
                 and_(
-                    not UserSession.is_active,
+                    UserSession.is_active == False,  # noqa: E712
                     UserSession.expires_at < now,
                     UserSession.created_at < cutoff_date,
                 )
@@ -356,7 +356,7 @@ class CRUDSession(CRUDBase[UserSession, SessionCreate, SessionUpdate]):
             stmt = delete(UserSession).where(
                 and_(
                     UserSession.user_id == uuid_obj,
-                    not UserSession.is_active,
+                    UserSession.is_active == False,  # noqa: E712
                     UserSession.expires_at < now,
                 )
             )
diff --git a/backend/pyproject.toml b/backend/pyproject.toml
index 792110e..29104ba 100644
--- a/backend/pyproject.toml
+++ b/backend/pyproject.toml
@@ -139,6 +139,10 @@ plugins = ["pydantic.mypy"]
 module = "alembic.*"
 ignore_errors = true
 
+[[tool.mypy.overrides]]
+module = "app.alembic.*"
+ignore_errors = true
+
 [[tool.mypy.overrides]]
 module = "sqlalchemy.*"
 ignore_missing_imports = true
@@ -171,6 +175,10 @@ ignore_missing_imports = true
 module = "apscheduler.*"
 ignore_missing_imports = true
 
+[[tool.mypy.overrides]]
+module = "starlette.*"
+ignore_missing_imports = true
+
 # ============================================================================
 # Pydantic mypy plugin configuration
 # ============================================================================