Given a first sync on a new device + forgotten passphrase, Weave will need to delete server data to change the passphrase. It will then upload the current client's data, but of course not be able to download any other device's data. This is mostly a ux problem, users might not realize what's going on and be confused. There is one additional case that is extra confusing: if the user chooses a directional sync down (replace client with cloud data), Weave will upload the current client's data to the cloud *before* wiping the client, so you end up with the same data anyway. Not that the "correct" solution is much better (wipe local before), in that case you would end up with no data whatsoever.

First, we should have better reset passphrase UI, so that users will try to check another machine instead of starting over. I don't know what the current behaviour is here, after the stale data bug has been fixed. Second, reset/change passphrase (they're both going to be the same thing) should probably be something we have a more explicit handling for clients. i.e. if the server was reset, we need to have a clearly defined behaviour for how we re-upload.

This is fixed as a part of bug 545725... we are now explicit about what happens at each state, and other fixes handle firstSync case much better, so I think this is done.