Wikimedia Bugzilla is closed!

In the MediaWiki Collection extension, doRender() in RenderingAPI.php uses $wgContLang->getCode() to get the language code for the render service.

For our MediaWiki installation, getCode() returns "de-ch". The render service does not understand this and uses English.

As a temporary fix, I patched doRender() to use "de" as the language code:

   $params['language'] = 'de';