Upgrade Stability
What it is
The property that your custom code and configuration keep working unchanged across SAP releases and updates. It's the outcome Clean Core is designed to produce.
Why it matters for Clean Core
It's the whole business case. Upgrade-stable extensions turn an SAP upgrade from a multi-month regression project into a routine update — which is what RISE and cloud delivery assume.
Common pitfall
Equating 'it compiled after the upgrade' with stability. Stability means released-contract dependencies only; code that compiles today by depending on unreleased internals can break silently in any update.