Maintain configuration settings in a single authoritative source to avoid duplication and inconsistencies across multiple files. When possible, use `pyproject.toml` as the primary configuration file and remove redundant specifications from other files like `.pre-commit-config.yaml` and `Makefile`. This approach follows the DRY (Don't Repeat Yourself) principle and ensures that configuration changes only need to be made in one place, reducing maintenance overhead and preventing configuration drift. Example: ```toml # pyproject.toml - Single source of truth [tool.ruff.lint] select = [ "UP018", "UP032", "UP034", "W", # -- Warnings, including invalid escape-sequence -- ] ignore = [ "COM812", "PT005", # -- flags mock fixtures with names intentionally matching private method name -- "PT011", ] ``` Remove redundant ruff configurations from `.pre-commit-config.yaml` and `Makefile` so they automatically pick up settings from `pyproject.toml`.