Major Khaletskiy's agent is a character appearing in S.T.A.L.K.E.R.: Clear Sky.
This strange military agent will appear at a camp east to the Rookie Village in the Cordon if the player helped Major Khaletskiy escape from the Loners base by handing him a pistol. Much like Semyon Lambee, he shows up as an enemy on the radar due to his affiliation with the army, but will not react to the player's presence and can be talked to. His role is quite unspecified as the player will have no dialogue options with him, and he uses generic intro quotes.
It is worth noting he is referred within the game files to as an "army secret trader", implying he had a larger role in early development.