Currently on the beta cluster, e.g. here: https://de.wikipedia.beta.wmflabs.org/w/index.php?title=TabellenTest&stable=1
```counterexample, lines=5
[ZnKErfFC6F8ObEoF4FNawQAAAAc] /w/index.php?stable=1&title=TabellenTest InvalidArgumentException: LinksMigration config 769 on pagelinks table is not supported anymore
Backtrace:
from /srv/mediawiki/php-master/includes/linker/LinksMigration.php(171)
#0 /srv/mediawiki/php-master/includes/linker/LinksMigration.php(113): MediaWiki\Linker\LinksMigration->assertMapping(string)
#1 /srv/mediawiki/php-master/extensions/FlaggedRevs/includes/backend/FRDependencyUpdate.php(212): MediaWiki\Linker\LinksMigration->getQueryInfo(string)
#2 /srv/mediawiki/php-master/extensions/FlaggedRevs/includes/backend/FRDependencyUpdate.php(45): FRDependencyUpdate->getCurrentVersionLinks()
#3 /srv/mediawiki/php-master/extensions/FlaggedRevs/includes/frontend/FlaggablePageView.php(641): FRDependencyUpdate->doUpdate(integer)
#4 /srv/mediawiki/php-master/extensions/FlaggedRevs/includes/frontend/FlaggablePageView.php(317): FlaggablePageView->showStableVersion(FlaggedRevision, string, string)
#5 /srv/mediawiki/php-master/extensions/FlaggedRevs/includes/frontend/FlaggedRevsUIHooks.php(248): FlaggablePageView->setPageContent(NULL, boolean)
#6 /srv/mediawiki/php-master/includes/HookContainer/HookContainer.php(159): FlaggedRevsUIHooks->onArticleViewHeader(Article, NULL, boolean)
#7 /srv/mediawiki/php-master/includes/HookContainer/HookRunner.php(861): MediaWiki\HookContainer\HookContainer->run(string, array)
#8 /srv/mediawiki/php-master/includes/page/Article.php(610): MediaWiki\HookContainer\HookRunner->onArticleViewHeader(Article, NULL, boolean)
#9 /srv/mediawiki/php-master/includes/page/Article.php(539): Article->generateContentOutput(MediaWiki\User\User, ParserOptions, integer, MediaWiki\Output\OutputPage, array)
#10 /srv/mediawiki/php-master/includes/actions/ViewAction.php(78): Article->view()
#11 /srv/mediawiki/php-master/includes/actions/ActionEntryPoint.php(731): ViewAction->show()
#12 /srv/mediawiki/php-master/includes/actions/ActionEntryPoint.php(508): MediaWiki\Actions\ActionEntryPoint->performAction(Article, MediaWiki\Title\Title)
#13 /srv/mediawiki/php-master/includes/actions/ActionEntryPoint.php(145): MediaWiki\Actions\ActionEntryPoint->performRequest()
#14 /srv/mediawiki/php-master/includes/MediaWikiEntryPoint.php(200): MediaWiki\Actions\ActionEntryPoint->execute()
#15 /srv/mediawiki/php-master/index.php(58): MediaWiki\MediaWikiEntryPoint->run()
#16 /srv/mediawiki/w/index.php(3): require(string)
#17 {main}
```
The only open ticket I can find related to this is {T299947}.
I suspect a misconfiguration on the beta cluster, but it could also be a mistake in the code. 769 is 0x301, which is SCHEMA_COMPAT_READ_NEW + SCHEMA_COMPAT_WRITE_NEW + SCHEMA_COMPAT_WRITE_OLD. The code I can find via #CodeSearch ([e.g. here](https://gerrit.wikimedia.org/g/operations/mediawiki-config/+/dea50cac51f80d391352ff3e868aff8a234ee241/wmf-config/InitialiseSettings-labs.php#1160)) makes it look like SCHEMA_COMPAT_WRITE_OLD got deprecated, while still being enabled by default?
I'm afraid this could even affect production the moment it is rolled out. I'm going to mark this as a candidate for UBN because of this.