==== Error ====
* [[ https://logstash.wikimedia.org/app/discover#/doc/logstash-*/logstash-deploy-1-7.0.0-1-2025.06.04?id=t77CPJcBbAObVjXF0vxK | c0db9828-eb96-46b7-9095-b0052671bfab ]]
```name=message
Error: Typed property MediaWiki\Extension\CampaignEvents\Event\EventRegistration::$participationOptions must not be accessed before initialization
```
```name=trace,lines=10
from /srv/mediawiki/php-1.45.0-wmf.4/extensions/CampaignEvents/src/Event/EventRegistration.php(245)
#0 /srv/mediawiki/php-1.45.0-wmf.4/extensions/CampaignEvents/src/EventPage/EventPageDecorator.php(448): MediaWiki\Extension\CampaignEvents\Event\EventRegistration->getParticipationOptions()
#1 /srv/mediawiki/php-1.45.0-wmf.4/extensions/CampaignEvents/src/EventPage/EventPageDecorator.php(406): MediaWiki\Extension\CampaignEvents\EventPage\EventPageDecorator->getEventInfoHeaderRow(MediaWiki\Extension\CampaignEvents\Event\ExistingEventRegistration, int)
#2 /srv/mediawiki/php-1.45.0-wmf.4/extensions/CampaignEvents/src/EventPage/EventPageDecorator.php(276): MediaWiki\Extension\CampaignEvents\EventPage\EventPageDecorator->getHeaderElement(MediaWiki\Extension\CampaignEvents\Event\ExistingEventRegistration, int)
#3 /srv/mediawiki/php-1.45.0-wmf.4/extensions/CampaignEvents/src/EventPage/EventPageDecorator.php(164): MediaWiki\Extension\CampaignEvents\EventPage\EventPageDecorator->addRegistrationHeader(MediaWiki\Page\WikiPage, MediaWiki\Extension\CampaignEvents\Event\ExistingEventRegistration)
#4 /srv/mediawiki/php-1.45.0-wmf.4/extensions/CampaignEvents/src/Hooks/Handlers/ArticleViewHeaderHandler.php(35): MediaWiki\Extension\CampaignEvents\EventPage\EventPageDecorator->decoratePage(MediaWiki\Page\WikiPage)
#5 /srv/mediawiki/php-1.45.0-wmf.4/includes/HookContainer/HookContainer.php(155): MediaWiki\Extension\CampaignEvents\Hooks\Handlers\ArticleViewHeaderHandler->onArticleViewHeader(MediaWiki\Page\Article, null, bool)
#6 /srv/mediawiki/php-1.45.0-wmf.4/includes/HookContainer/HookRunner.php(880): MediaWiki\HookContainer\HookContainer->run(string, array)
#7 /srv/mediawiki/php-1.45.0-wmf.4/includes/page/Article.php(708): MediaWiki\HookContainer\HookRunner->onArticleViewHeader(MediaWiki\Page\Article, null, bool)
#8 /srv/mediawiki/php-1.45.0-wmf.4/includes/page/Article.php(551): MediaWiki\Page\Article->generateContentOutput(MediaWiki\User\User, MediaWiki\Parser\ParserOptions, int, MediaWiki\Output\OutputPage, array)
#9 /srv/mediawiki/php-1.45.0-wmf.4/includes/actions/ViewAction.php(80): MediaWiki\Page\Article->view()
#10 /srv/mediawiki/php-1.45.0-wmf.4/includes/actions/ActionEntryPoint.php(728): MediaWiki\Actions\ViewAction->show()
#11 /srv/mediawiki/php-1.45.0-wmf.4/includes/actions/ActionEntryPoint.php(505): MediaWiki\Actions\ActionEntryPoint->performAction(MediaWiki\Page\Article, MediaWiki\Title\Title)
#12 /srv/mediawiki/php-1.45.0-wmf.4/includes/actions/ActionEntryPoint.php(143): MediaWiki\Actions\ActionEntryPoint->performRequest()
#13 /srv/mediawiki/php-1.45.0-wmf.4/includes/MediaWikiEntryPoint.php(198): MediaWiki\Actions\ActionEntryPoint->execute()
#14 /srv/mediawiki/php-1.45.0-wmf.4/index.php(58): MediaWiki\MediaWikiEntryPoint->run()
#15 /srv/mediawiki/w/index.php(3): require(string)
#16 {main}
```
==== Impact ====
Event pages fail to load and display this error instead.
==== Notes ====
The property name was changed in [[https://gerrit.wikimedia.org/r/c/mediawiki/extensions/CampaignEvents/+/1152266 | r1152266]]. My guess is that the cache (added for T392784) holds objects with the old property name that aren't therefore being unserialized properly.