diff --git a/crates/chattyness-user-ui/src/components/avatar.rs b/crates/chattyness-user-ui/src/components/avatar.rs
index f05c698..2f7d3d2 100644
--- a/crates/chattyness-user-ui/src/components/avatar.rs
+++ b/crates/chattyness-user-ui/src/components/avatar.rs
@@ -354,12 +354,8 @@ pub fn Avatar(
     /// Opacity for fade-out animation (0.0 to 1.0, default 1.0).
     #[prop(default = 1.0)]
     opacity: f64,
-    /// Scene width in scene coordinates (for boundary calculations).
-    #[prop(optional)]
-    scene_width: Option<Signal<f64>>,
-    /// Scene height in scene coordinates (for boundary calculations).
-    #[prop(optional)]
-    scene_height: Option<Signal<f64>>,
+    /// Screen bounds for clamping (computed once at scene level).
+    screen_bounds: Signal<ScreenBounds>,
     /// Active speech bubble for this avatar (None if not speaking).
     #[prop(optional)]
     active_bubble: Option<Signal<Option<ActiveBubble>>>,
@@ -397,12 +393,8 @@ pub fn Avatar(
             &m.avatar.emotion_layer,
         );
 
-        // Get scene dimensions (use large defaults if not provided)
-        let sw = scene_width.map(|s| s.get()).unwrap_or(10000.0);
-        let sh = scene_height.map(|s| s.get()).unwrap_or(10000.0);
-
-        // Compute screen boundaries and avatar screen position
-        let boundaries = ScreenBounds::from_transform(sw, sh, sx, sy, ox, oy);
+        // Use passed-in screen bounds (computed once at scene level)
+        let boundaries = screen_bounds.get();
         let avatar_screen_x = m.member.position_x * sx + ox;
         let avatar_screen_y = m.member.position_y * sy + oy;
 
@@ -513,16 +505,14 @@ pub fn Avatar(
                 &m.avatar.emotion_layer,
             );
 
-            // Get scene dimensions and transform parameters
+            // Get transform parameters for computing avatar screen position
             let sx = scale_x.get();
             let sy = scale_y.get();
             let ox = offset_x.get();
             let oy = offset_y.get();
-            let sw = scene_width.map(|s| s.get()).unwrap_or(10000.0);
-            let sh = scene_height.map(|s| s.get()).unwrap_or(10000.0);
 
-            // Create unified layout - same calculation as style closure
-            let boundaries = ScreenBounds::from_transform(sw, sh, sx, sy, ox, oy);
+            // Use passed-in screen bounds (computed once at scene level)
+            let boundaries = screen_bounds.get();
             let avatar_screen_x = m.member.position_x * sx + ox;
             let avatar_screen_y = m.member.position_y * sy + oy;
 
diff --git a/crates/chattyness-user-ui/src/components/scene_viewer.rs b/crates/chattyness-user-ui/src/components/scene_viewer.rs
index b87c99a..0adb53a 100644
--- a/crates/chattyness-user-ui/src/components/scene_viewer.rs
+++ b/crates/chattyness-user-ui/src/components/scene_viewer.rs
@@ -22,7 +22,7 @@ use uuid::Uuid;
 
 use chattyness_db::models::{ChannelMemberWithAvatar, LooseProp, Scene};
 
-use super::avatar::{Avatar, member_key};
+use super::avatar::{Avatar, ScreenBounds, member_key};
 #[cfg(feature = "hydrate")]
 use super::canvas_utils::hit_test_canvas;
 use super::chat_types::ActiveBubble;
@@ -450,6 +450,18 @@ pub fn RealmSceneViewer(
     let scene_width_signal = Signal::derive(move || scene_width_f);
     let scene_height_signal = Signal::derive(move || scene_height_f);
 
+    // Compute ScreenBounds once for all avatars (instead of each avatar computing it)
+    let screen_bounds = Signal::derive(move || {
+        ScreenBounds::from_transform(
+            scene_width_signal.get(),
+            scene_height_signal.get(),
+            scale_x_signal.get(),
+            scale_y_signal.get(),
+            offset_x_signal.get(),
+            offset_y_signal.get(),
+        )
+    });
+
     let members_by_key = Signal::derive(move || {
         sorted_members.get().into_iter().enumerate()
             .map(|(idx, m)| (member_key(&m), (idx, m)))
@@ -520,8 +532,7 @@ pub fn RealmSceneViewer(
                                         prop_size=prop_size
                                         z_index=z
                                         text_em_size=text_em_size
-                                        scene_width=scene_width_signal
-                                        scene_height=scene_height_signal
+                                        screen_bounds=screen_bounds
                                         active_bubble=bubble_signal
                                     />
                                 }
@@ -553,8 +564,7 @@ pub fn RealmSceneViewer(
                                             z_index=5
                                             text_em_size=text_em_size
                                             opacity=opacity
-                                            scene_width=scene_width_signal
-                                            scene_height=scene_height_signal
+                                            screen_bounds=screen_bounds
                                         />
                                     })
                                 } else { None }