Before switching purely to using the new MCR schema, we need to be sure we are not accessing the pre-MCR schema anywhere. In this step, we will make sure that all pre-MCR schema access is gated with SCHEMA_COMPAT_* bitfield values. These changes must be made in MediaWiki core and WMF-production and bundled extensions. These changes should be made or identified and maintainers notified in other extensions searched by code search.
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