Undefined constant Drupal\bootstrap\Plugin\Alter\ThemeRegistry::PREPROCESS_INVOKES in Drupal\Core\Theme\Registry->postProcessExtension()

With the attached MR I think this issue should be set to 'Needs Review'…

Patch works for us. Thanks!

This is a core issue and has been fixed - see 🐛 New constants in \Drupal\Core\Theme\Registry are private but they are accessed with static:: Active - hopefully we will release a new 11.2.x release ASAP.

We've now committed a fix to core and will do a release soon. This issue can be considered a duplicate.