CX

CX refers to "content translation". You may be looking for:

• Content translation (mediawiki.org), manual for users.
• Extension:ContentTranslation (mediawiki.org), developer manual of the MediaWiki extension (provides the UI and wiki integration).
• cxserver, the Node.js-powered backend that powers this feature:
  • mediawiki/services/cxserver.git (source code)
  • https://cxserver.wikimedia.org/v1/?doc (live instance and API docs)