Which @angular/* package(s) are the source of the bug?

Don't known / other

Is this a regression?

Yes

Description

After migrating to Angular 18 and switching to the new application build system (@angular-devkit/build-angular:application), my app renders significantly slower when loaded inside an <iframe>.

However, if I host the same app and open it directly in a browser tab (outside iframe), it renders very fast — suggesting the issue is specific to iframe + new builder interaction.

This performance issue was not present before the migration.

Please provide a link to a minimal reproduction of the bug

No response

Please provide the exception or error you saw

Please provide the environment you discovered this bug in (run ng version)

Angular CLI: 18.2.5
Node: 20.18.0

Anything else?

No response