diff --git a/internal/system/containerbox.go b/internal/system/containerbox.go
index aa84b44..304192c 100644
--- a/internal/system/containerbox.go
+++ b/internal/system/containerbox.go
@@ -20,7 +20,6 @@ type containerBox struct {
 	attrLayout   attrHierarchy[tomo.AttrLayout]
 
 	children []anyBox
-	layout   tomo.Layout
 
 	on struct {
 		contentBoundsChange event.FuncBroadcaster
@@ -187,19 +186,21 @@ func (this *containerBox) setAttr (attr tomo.Attr, user bool) {
 }
 
 func (this *containerBox) recommendedHeight (width int) int {
-	if this.layout == nil || this.attrOverflow.Value().Y {
+	layout := this.attrLayout.Value().Layout
+	if layout == nil || this.attrOverflow.Value().Y {
 		return this.minSize.Value().Y
 	} else {
-		return this.layout.RecommendedHeight(this.layoutHints(), this.boxQuerier(), width) +
+		return layout.RecommendedHeight(this.layoutHints(), this.boxQuerier(), width) +
 			this.borderAndPaddingSum().Vertical()
 	}
 }
 
 func (this *containerBox) recommendedWidth (height int) int {
-	if this.layout == nil || this.attrOverflow.Value().X {
+	layout := this.attrLayout.Value().Layout
+	if layout == nil || this.attrOverflow.Value().X {
 		return this.minSize.Value().X
 	} else {
-		return this.layout.RecommendedWidth(this.layoutHints(), this.boxQuerier(), height) +
+		return layout.RecommendedWidth(this.layoutHints(), this.boxQuerier(), height) +
 			this.borderAndPaddingSum().Horizontal()
 	}
 }
@@ -274,8 +275,9 @@ func (this *containerBox) layoutHints () tomo.LayoutHints {
 func (this *containerBox) contentMinimum () image.Point {
 	overflow := this.attrOverflow.Value()
 	minimum  := this.box.contentMinimum()
-	if this.layout != nil {
-		layoutMinimum := this.layout.MinimumSize (
+	layout := this.attrLayout.Value().Layout
+	if layout != nil {
+		layoutMinimum := layout.MinimumSize (
 			this.layoutHints(),
 			this.boxQuerier())
 		if overflow.X { layoutMinimum.X = 0 }
@@ -288,12 +290,13 @@ func (this *containerBox) contentMinimum () image.Point {
 func (this *containerBox) doLayout () {
 	this.box.doLayout()
 	previousContentBounds := this.contentBounds
+	layout := this.attrLayout.Value().Layout
 
 	// by default, use innerBounds (translated to 0, 0) for contentBounds.
 	// if a direction overflows, use the layout's minimum size for it.
 	var minimum image.Point
-	if this.layout != nil {
-		minimum = this.layout.MinimumSize (
+	if layout != nil {
+		minimum = layout.MinimumSize (
 			this.layoutHints(),
 			this.boxQuerier())
 	}
@@ -304,10 +307,10 @@ func (this *containerBox) doLayout () {
 	if overflow.Y { this.contentBounds.Max.Y = this.contentBounds.Min.Y + minimum.Y }
 	
 	// arrange children
-	if this.layout != nil {
+	if layout != nil {
 		layoutHints := this.layoutHints()
 		layoutHints.Bounds = this.contentBounds
-		this.layout.Arrange(layoutHints, this.boxArranger())
+		layout.Arrange(layoutHints, this.boxArranger())
 	}
 
 	// build an accurate contentBounds by unioning the bounds of all child
@@ -323,7 +326,7 @@ func (this *containerBox) doLayout () {
 
 	// offset children and contentBounds by scroll
 	for _, box := range this.children {
-		assertAnyBox(box).setBounds(box.Bounds().Add(this.scroll).Add(innerBounds.Min))
+		box.setBounds(box.Bounds().Add(this.scroll).Add(innerBounds.Min))
 	}
 	this.contentBounds = this.contentBounds.Add(this.scroll)