Access and observation boundary

The accessible data factor is $B=NA$, read only through its computational-basis occupation projectors

The record register $C$ has basis $\{|r{⟩}_C:r\in \mathcal{R}\}$, and its observable algebra is

An optional laboratory spectator $S$ is untouched. An optional reference $Q$ is also untouched and is included for complete channel comparisons, not as assistance to the observer. The accessible recorded-spectator algebra is

The supplier's source labels, channel environments, and measurement-device complements are outside this access boundary.

The newly returned object is $C$ alone. An existing spectator may remain on a comparison interface, but neither $N$ nor $A$ is a quantum output. Allowed continuations may read $C$, act on $S$, and allocate fresh names. They may not reuse the consumed names of $N$ or $A$.