@prologic@twtxt.net Just request the last seen twt as well in the Range header and if it doesn’t match the old one you’ve already seen, you know that this feed doesn’t operate in append only mode, so that you can request the whole feed. It’s worth mentioning that this also happens if the key value comments at the beginning of the file have changed, too, e.g. when the maintained subscription list has been modified. Yes, not ideal. Healthy 2021 everybody!