Yeah this is tricky. In the worker context they're not prefixed with anything either. A ``nameko.lang`` "header" in a message becomes just a "lang" key in the worker context data. The prefix was to make debugging clearer "over the wire", which doesn't make much sense outside of a messaging implementation.

A better catchall term is perhaps "meta" because it doesn't imply messaging. But changing the name doesn't solve the prefix problem...