Cover re-pick veto callback (npc_on_best_cover_repick)

gamedata/scripts/callbacks_gameobject.script

@@ -446,6 +446,20 @@ _G.CAI_Stalker__AllowCombatActionSwitch = function(npc, from_op, to_op)
 	return flags.allow ~= false
 end
 
+-- NPC best-cover re-pick veto. Fires BEFORE the NPC replaces its current best cover
+-- (on_best_cover_changed, which clears InCover/LookedOut/PositionHolded, runs after an
+-- allowed change). Set flags.allow = false to keep the current cover. Only fires when a
+-- cover is already held; a change to a different point and losing the cover entirely both count.
+-- Re-asked on the next invalidation while denied; two invalidators are standing state (enemy
+-- within 3m of the held cover, smart cover without a loophole) and re-ask every combat action
+-- update, so keep subscribers cheap and cap a continuous denial.
+AddScriptCallback("npc_on_best_cover_repick")
+_G.CAI_Stalker__AllowCoverRepick = function(npc)
+	local flags = { allow = true }
+	SendScriptCallback("npc_on_best_cover_repick", npc, flags)
+	return flags.allow ~= false
+end
+
 -- NPC TakeCover destination callback. Only fires when a real cover point is found, not on fallback paths
 AddScriptCallback("npc_on_take_cover_destination")
 _G.CAI_Stalker__OnTakeCoverDestination = function(npc, cover_pos, enemy)

src/xrGame/ai/stalker/ai_stalker_cover.cpp

@@ -298,10 +298,22 @@ const CCoverPoint* CAI_Stalker::best_cover(const Fvector& position_to_cover_from
 	const CCoverPoint* best_cover = find_best_cover(position_to_cover_from);
 	if (best_cover != m_best_cover)
 	{
-		on_best_cover_changed(best_cover, m_best_cover);
-		m_best_cover = best_cover;
-		m_best_cover_advance_cover = 0;
-		m_best_cover_can_try_advance = false;
+		// Let Lua veto replacing the held cover before on_best_cover_changed clears the cover props.
+		// allow = false keeps m_best_cover. Only when a cover is already held; no functor means allow.
+		bool allow = true;
+		if (m_best_cover)
+		{
+			luabind::functor<bool> repick_funct;
+			if (ai().script_engine().functor("_G.CAI_Stalker__AllowCoverRepick", repick_funct))
+				allow = repick_funct(lua_game_object());
+		}
+		if (allow)
+		{
+			on_best_cover_changed(best_cover, m_best_cover);
+			m_best_cover = best_cover;
+			m_best_cover_advance_cover = 0;
+			m_best_cover_can_try_advance = false;
+		}
 	}
 
 	m_best_cover_value = m_best_cover ? best_cover_value(position_to_cover_from) : flt_max;