An irreversible damage flag

Let $Q$ be a qubit and $s\in \{0,1\}$ indicate whether its one coherent edge has been scarred. Choose a fresh independent damage flag with probability $h\in (0,1)$ whenever $s=0$.

For $s=0$, use

For $s=1$, use ${K_0}^{(1)}=I$ and $f(1,0)=1$. These complete operations leave $Q$ unchanged.

This hazard is an explicit comparison-model choice, not a derivation of the source's threshold controller.