diff --git a/Tactical/Points.cpp b/Tactical/Points.cpp
index 4c0ac1fce..b6a8c1153 100644
--- a/Tactical/Points.cpp
+++ b/Tactical/Points.cpp
@@ -391,6 +391,13 @@ INT16 TerrainBreathPoints(SOLDIERTYPE * pSoldier, INT32 sGridNo, INT8 bDir, UINT
 
 
 INT16 ActionPointCost( SOLDIERTYPE *pSoldier, INT32 sGridNo, INT8 bDir, UINT16 usMovementMode )
+{
+	// Real, per-step movement: the soldier is physically at his current stance, so his
+	// live anim state IS the previous tile's mode.
+	return ActionPointCost( pSoldier, sGridNo, bDir, usMovementMode, pSoldier->usAnimState );
+}
+
+INT16 ActionPointCost( SOLDIERTYPE *pSoldier, INT32 sGridNo, INT8 bDir, UINT16 usMovementMode, UINT16 usPrevMovementMode )
 {
 	INT16 sTileCost, sSwitchValue;
 	FLOAT sPoints = 0;
@@ -535,7 +542,7 @@ INT16 ActionPointCost( SOLDIERTYPE *pSoldier, INT32 sGridNo, INT8 bDir, UINT16 u
 			sPoints = max(1.0f, ( sPoints * (100 - (FLOAT)gSkillTraitValues.ubATAPsMovementReduction) / 100.0f ) );
 		}
 
-		if (usMovementMode == RUNNING && pSoldier->usAnimState != RUNNING)
+		if (usMovementMode == RUNNING && usPrevMovementMode != RUNNING)
 		{
 			// CHRISL
 			if ((UsingNewInventorySystem() == true) && FindBackpackOnSoldier(pSoldier) != ITEM_NOT_FOUND)
diff --git a/Tactical/Points.h b/Tactical/Points.h
index 9bf9dec9f..ce3833522 100644
--- a/Tactical/Points.h
+++ b/Tactical/Points.h
@@ -282,6 +282,13 @@ INT16 BaseAPsToShootOrStabNoModifier( INT16 bAPs, INT16 bAimSkill, OBJECTTYPE *
 INT16 BaseAPsToShootOrStabNoModifier( INT16 bAPs, INT16 bAimSkill, OBJECTTYPE * pObj );
 
 INT16 TerrainActionPoints( SOLDIERTYPE *pSoldier, INT32 sGridno, INT8 bDir, INT8 bLevel );
+// Per-tile movement AP cost - the single source of truth for what a step costs.
+// usPrevMovementMode is the mode the soldier was in on the PREVIOUS tile, used to
+// charge the one-time "spin up to run" penalty exactly once. Real movement passes
+// the soldier's live anim state; a path estimator must pass its simulated prior mode,
+// because the soldier doesn't actually move while the path is being summed.
+INT16 ActionPointCost( SOLDIERTYPE *pSoldier, INT32 sGridNo, INT8 bDir, UINT16 usMovementMode, UINT16 usPrevMovementMode );
+// Convenience overload: prev mode = the soldier's current anim state (correct for real, per-step movement).
 INT16 ActionPointCost( SOLDIERTYPE *pSoldier, INT32 sGridNo, INT8 bDir, UINT16 usMovementMode	);
 INT16 EstimateActionPointCost( SOLDIERTYPE *pSoldier, INT32 sGridNo, INT8 bDir, UINT16 usMovementMode, INT8 bPathIndex, INT8 bPathLength );
 BOOLEAN SelectedMercCanAffordMove(	);