Opening on the coding-agent task that keeps failing and then going into the 128-token replay is a good way in, because I think most people treat the attention window like durable state when it is not. The distinction from a checkpoint is worth hammering: nothing about the window survives the way a real checkpoint would, so "it remembered a second ago" is doing a lot of unearned work. Did the retry-test example actually trace back to the replay boundary, or was that mostly the hook?