Error
Request ID: W6M@7grAMG8AAAerQtQAAABL
Request: GET, /w/api.php?...prop=wikitext..&contentformat=text/plain
MWException: Format text/plain is not supported for content model wikitext #0 /srv/mediawiki/php-1.32.0-wmf.20/includes/content/TextContentHandler.php(46): ContentHandler->checkFormat(string) #1 /srv/mediawiki/php-1.32.0-wmf.20/includes/content/AbstractContent.php(155): TextContentHandler->serializeContent(WikitextContent, string) #2 /srv/mediawiki/php-1.32.0-wmf.20/includes/api/ApiParse.php(463): AbstractContent->serialize(string) #3 /srv/mediawiki/php-1.32.0-wmf.20/includes/api/ApiMain.php(1587): ApiParse->execute() #4 /srv/mediawiki/php-1.32.0-wmf.20/includes/api/ApiMain.php(531): ApiMain->executeAction() #5 /srv/mediawiki/php-1.32.0-wmf.20/includes/api/ApiMain.php(502): ApiMain->executeActionWithErrorHandling() #6 /srv/mediawiki/php-1.32.0-wmf.20/api.php(87): ApiMain->execute() #7 /srv/mediawiki/w/api.php(3): include(string)
Notes
API request fatal rate is increased due to this issue.
It appears that this is a matter of a certain feature not being available yet, or intentionally not provided. That's probably fine, at least in the short-term, but it needs to not crash the request to avoid false alarms. As a stop-gap solution it can probably be caught somewhere along the way and simply reject explicitly so as to mark it a user error (rather than server error).
Related: