The **ember-disable-prototype-extensions** add‑on adds a tiny runtime shim that disables Ember’s prototype extensions (e.g., `Ember.Array`, `Ember.String`), allowing addon authors to test their code without relying on those experimental features. It’s intended for developers who maintain Ember addons or applications that want to guarantee compatibility with environments where prototype extensions are turned off, ensuring their libraries work regardless of whether the consuming app enables them.