@merks Which category.xml are these, e.g. org.apache.xerces, being moved to? And how I do correctly add the Jakarta servlet and servlet-jsp 6.1 API bundles going forward?

I believe those were already present. But I"m on my travel computer now so it's hard to check this week.

Generally you add bundles by specifying a dependency in the MANIFEST.MF and including them in the/category.xml if/when necessary. (Personally I more often define a dependencies feature and centralize the includes there but that's equivalent to including it in a category.xml for the purpose of composing the necessary content in an update site.)

BTW, you can also use imports in features, if necessary, but it's rarely necessary because bundles generally specify all the necessary requirements. But imports don't help you ensure that the content is included in an update site just that the content is installed when the feature is installed...

@merks I can't find Xerces, at least, in any of WTP's category.xml files. In theory, adopters only need to refer to the source editing repos (plus common and servertools) to install its bundles/features, so would removing these from the feature without adding them to one of their category.xml files break that ability? Would I be implicitly relying on another repository to supply those bundles?

See

https://github.com/eclipse-servertools/servertools/pull/18/changes

I did added each removed thing to a category.xml but not every repository has its own category.xml.

Maybe those also need to be here?

webtools.releng.aggregator/webtools.repositories/repository/category.xml

It's not entirely clear to me which is/are used to build the site(s).