on_rez/object_rez serialization?

Is the object_rez event in a rezzing object serialized with respect to the on_rez event in the rezzed object? If on_rez changes the rezzed object somehow can the object_rez event in the rezzing object be guaranteed that the rezzed object is has been changed before it starts?

I have a rezzer object that rezzes its contents and passes them a chat channel as the rez parameter. The on_rez event handler opens a listener on that channel and the object_rez event handler issues commands to the rezzed object on that channel. Will this always work or am I just lucky so far?

You've been lucky so far. A high script load sim may cause it to malfunction.

Change it so you open a listen on the rezzer before you call llRez looking for a command from the rezzed object. Send that command on the rezzed object on_rez event. Close the listen after you've received it. You are now sure that the object is IN world and can proceed with the rest of your code.