Reply: is the proof the consensus itself, or the evidence it grew from? Consensus was on the thing for a reason, and the new feature was never covered by it; the argument also turns against them (the ḥadath was certain before using the water, and so on); where a proof exists for the new case (the believing emigrant woman, Q 60:10), one acts on it. The same holds for the general: the mustaʾman who spies cannot be killed by citing "kill the polytheists". (v2/117–118)
[Editorial] Debate note (bāb): B12.06 is the Ḥanafī basis for "the Companion's opinion over qiyās", and Sarakhsī himself shows the imams' practice was mixed and al-Karkhī dissented. Cite al-Bardaʿī's view as "the sounder" in Sarakhsī's judgement, with the agreed core (matters where qiyās has no role).