Comment by lifthrasiir

I understand a forward compatibility concern, but have you considered to put an attention-grabbing alert in the encoder and clearly state that official releases in the future won't be able to decompress the output? Also your concern may have been too overblown; there have been more than 100 PAQ versions with mutually incompatible formats but such issues didn't happen too often. (Not to say that ZPAQ was pointless, of course.)