Remark: A flag is not a success certificate

The code branch contains both coherent code transfer and residual-vacuum ambiguity. At $\eta =0$ it occurs with probability one, although no message is recoverable from $R$. Thus $\mathsf{c}$ must not be relabeled “successful recovery.”

Adding the flag leaves the flag-forgotten error $t$ unchanged. This statement concerns the declared decoder, not the possible value of the flag for other processing. Conditional normalization is nonlinear and is not a deterministic recovery channel. The no-signaling identity holds after summing all outcomes; conditional reference states may differ.