New Gmail Labs Offline Feature: How will it handle collisions?

Excellent, great to see the Gmail labs have added the offline capability via Google Gears:

Official Gmail Blog: New in Labs: Offline Gmail

Now it will be interesting to see how this mechanism will handle "collisions": e.g.

Suppose while working offline on computer A, I tag a particular gmail message with tag X, and then (before going back online from that computer A), I inadvertently access the same message from computer B [or perhaps SmartPhone B using mobile gmail] while online, and tag it with tag Y:

Will the Gears-based synchronization interactively detect the discrepancy (data "collision") when I go online again from computer A, and offer me the choice to accept either tag X or tag Y?

Or will it silently choose tag X or Y (and if so, which?)