mypy black ruff

AGENTS.md

@@ -132,3 +132,15 @@ item = B4wExportFactory.build(  # build() for partial, create() for full
 - Run single test: `pytest tests/test_model_b4wexport.py -v`
 - View migrations: `ls alembic/versions/`
 - Test data location: `/scripts/dummy_data/`
+
+### Type Checking (mypy)
+
+```bash
+# Static type checking with mypy
+uv run mypy src/
+
+# With test coverage
+uv run pytest --cov=src --cov-report=term-missing
+```
+
+**Note**: Some comparisons between `date | None` types require explicit guards or type assertions to satisfy mypy, even when the logic is correct. See `src/domain_utils.py` for examples.