I tried Googling this and looking through the user manual here: https://www.mediawiki.org/wiki/Wikidata_Query_Service/User_Manual

I didn't see any description of what HTTP status codes the service endpoint might return in various situations. I'm hoping to get a list like:

400: Returned when there is a generic problem with the query
455: Returned when the query could not be parsed

500: Unspecified server error
501: Unknown error when trying to parse the query

etc

My main goal is to design my service so that I can decide which errors are transient, caused by connectivity or temporary capacity issues, and can be retried. This is opposed to errors that are caused by the query data I'm sending which will never work.

Thanks!