A unit loses its concealment in the CCPh only if it makes/directs a CC attack [EXC: a successful Ambush; 11.4] or suffers Casualty Reduction.
et
The side with an Ambush advantage may also maintain any concealment it has in CC until it attacks without eliminating/capturing its target.
çà me parait clair, si tu ambush et que tu élimines tout le monde, tu gardes le conceal.