Currently, the API can take a page name or raw wikitext to run through action=parse. When using a page name, it might be helpful to specify an oldid/revid.
Version: unspecified
Severity: enhancement
URL: http://en.wikipedia.org/w/api.php?action=parse&page=Test&format=xml&revid=1
I was just looking back over this, and it's not quite what I was asking for. We added the ability to return the revID of a page, but we're not able to specify an old TO parse. For example, the current revID of [[w:Test]] is 204141151. If I wanted to parse the original version of the page (id: 11659), there is no way to do so. I guess I'm saying being able to specify a revID /instead/ of a page title, so we can allow parsing of old versions.