NOTE
Open–Closed Principle
Designing stable boundaries so common extensions require less modification to trusted core code.
This is a historical learning note and may contain outdated or incomplete understanding.
The Open–Closed Principle aims for modules that can support expected extensions without repeatedly modifying fragile central logic.
Typical tools include polymorphism, registration, data-driven policy, and extension points. Do not predict every future variation: premature extension mechanisms create complexity. Stabilize only the boundaries where real variation exists.