Hello, As of r75906 [1] or one of its related revisions, the sessionkey returned by action=upload is no longer an integer but a string. This may affect you if your client library is written in a strongly, statically typed language such as C or C#. This revision is part of MediaWiki 1.17, which is tentatively slated for deployment on Wikimedia in one or two weeks and for release a month or so after that. Other breaking changes previously announced on this list and not yet live on Wikimedia will also go live then. Best regards, Bryan [1] http://www.mediawiki.org/wiki/Special:Code/MediaWiki/75906