Gauge-condition independence of BRST-closed correlation functions (${\partial }_t⟨\mathcal{O}⟩=i⟨\mathcal{O}s{\dot{\Psi }}_t{⟩}_c=0$)

For an admissible family of gauge-fixing fermions, variation inserts a BRST-exact operator into normalized correlations. If the measured operators are BRST-closed, the graded BRST Ward identity makes that insertion vanish. This extends gauge-parameter independence to changes of the gauge functional itself, provided the action and measure preserve BRST symmetry and the change produces no boundary contribution. It is the perturbative statement; global gauge-orbit problems require additional analysis.