diff --git a/frontend/src/tools/drawing/SeatingTemplateTool.ts b/frontend/src/tools/drawing/SeatingTemplateTool.ts
index 70ef2ad..e2a1ed7 100644
--- a/frontend/src/tools/drawing/SeatingTemplateTool.ts
+++ b/frontend/src/tools/drawing/SeatingTemplateTool.ts
@@ -71,7 +71,7 @@ class SeatingTemplateTool extends Tool {
       
       // Create table
       this.yjsDoc.createElement({
-        id: Date.now().toString() + '_table_' + i,
+        id: crypto.randomUUID() + '_table_' + i,
         type: 'rectangular_table',
         layerId: 'default',
         x: tableX,
@@ -88,7 +88,7 @@ class SeatingTemplateTool extends Tool {
         
         // Top side chairs
         this.yjsDoc.createElement({
-          id: Date.now().toString() + '_chair_top_' + i + '_' + j,
+          id: crypto.randomUUID() + '_chair_top_' + i + '_' + j,
           type: 'chair',
           layerId: 'default',
           x: tableX + positionRatio * tableWidth - chairWidth / 2,
@@ -100,7 +100,7 @@ class SeatingTemplateTool extends Tool {
         
         // Bottom side chairs
         this.yjsDoc.createElement({
-          id: Date.now().toString() + '_chair_bottom_' + i + '_' + j,
+          id: crypto.randomUUID() + '_chair_bottom_' + i + '_' + j,
           type: 'chair',
           layerId: 'default',
           x: tableX + positionRatio * tableWidth - chairWidth / 2,
@@ -126,7 +126,7 @@ class SeatingTemplateTool extends Tool {
         
         // Create round table
         this.yjsDoc.createElement({
-          id: Date.now().toString() + '_table_' + i + '_' + j,
+          id: crypto.randomUUID() + '_table_' + i + '_' + j,
           type: 'round_table',
           layerId: 'default',
           x: tableX - tableRadius,
@@ -148,7 +148,7 @@ class SeatingTemplateTool extends Tool {
           const chairY = tableY + (tableRadius + this.chairSpacing) * Math.sin(angle) - 22.5;
           
           this.yjsDoc.createElement({
-            id: Date.now().toString() + '_chair_' + i + '_' + j + '_' + k,
+            id: crypto.randomUUID() + '_chair_' + i + '_' + j + '_' + k,
             type: 'chair',
             layerId: 'default',
             x: chairX,
@@ -176,7 +176,7 @@ class SeatingTemplateTool extends Tool {
         
         // Create table
         this.yjsDoc.createElement({
-          id: Date.now().toString() + '_table_' + i + '_' + j,
+          id: crypto.randomUUID() + '_table_' + i + '_' + j,
           type: 'rectangular_table',
           layerId: 'default',
           x: tableX,
@@ -198,7 +198,7 @@ class SeatingTemplateTool extends Tool {
     
     // Create main table (president's table)
     this.yjsDoc.createElement({
-      id: Date.now().toString() + '_main_table',
+      id: crypto.randomUUID() + '_main_table',
       type: 'rectangular_table',
       layerId: 'default',
       x: x + tableWidth / 2,
@@ -213,7 +213,7 @@ class SeatingTemplateTool extends Tool {
     for (let i = 0; i < sideTablesCount; i++) {
       // Left side table
       this.yjsDoc.createElement({
-        id: Date.now().toString() + '_left_table_' + i,
+        id: crypto.randomUUID() + '_left_table_' + i,
         type: 'rectangular_table',
         layerId: 'default',
         x: x,
@@ -225,7 +225,7 @@ class SeatingTemplateTool extends Tool {
       
       // Right side table
       this.yjsDoc.createElement({
-        id: Date.now().toString() + '_right_table_' + i,
+        id: crypto.randomUUID() + '_right_table_' + i,
         type: 'rectangular_table',
         layerId: 'default',
         x: x + tableWidth + tableWidth / 2,
@@ -238,7 +238,7 @@ class SeatingTemplateTool extends Tool {
       // Create chairs for side tables
       // Left side chairs
       this.yjsDoc.createElement({
-        id: Date.now().toString() + '_left_chair_' + i,
+        id: crypto.randomUUID() + '_left_chair_' + i,
         type: 'chair',
         layerId: 'default',
         x: x - this.chairSpacing - chairWidth,
@@ -250,7 +250,7 @@ class SeatingTemplateTool extends Tool {
       
       // Right side chairs
       this.yjsDoc.createElement({
-        id: Date.now().toString() + '_right_chair_' + i,
+        id: crypto.randomUUID() + '_right_chair_' + i,
         type: 'chair',
         layerId: 'default',
         x: x + tableWidth + tableWidth / 2 + tableWidth / 2 + this.chairSpacing,
@@ -262,7 +262,7 @@ class SeatingTemplateTool extends Tool {
     }
   }
 
-  // Create Klasse template (U-shape classroom layout)
+  // Create Klasse template (U-shape classroom layout open at bottom)
   private createKlasseTemplate(x: number, y: number): void {
     const tableWidth = 120;
     const tableHeight = 60;
@@ -271,7 +271,7 @@ class SeatingTemplateTool extends Tool {
     
     // Create teacher's table
     this.yjsDoc.createElement({
-      id: Date.now().toString() + '_teacher_table',
+      id: crypto.randomUUID() + '_teacher_table',
       type: 'rectangular_table',
       layerId: 'default',
       x: x + tableWidth,
@@ -281,13 +281,14 @@ class SeatingTemplateTool extends Tool {
       properties: {}
     });
     
-    // Create student tables in U-shape
+    // Create student tables in U-shape (open at bottom)
     const rows = 4;
     const cols = 5;
     
     for (let i = 0; i < rows; i++) {
       for (let j = 0; j < cols; j++) {
-        // Skip center tables to create U-shape
+        // Create U-shape that is open at the bottom
+        // Skip inner tables but keep the bottom row
         if (i > 0 && i < rows - 1 && j > 0 && j < cols - 1) continue;
         
         const tableX = x + j * (tableWidth + this.tableSpacing);
@@ -295,7 +296,7 @@ class SeatingTemplateTool extends Tool {
         
         // Create table
         this.yjsDoc.createElement({
-          id: Date.now().toString() + '_student_table_' + i + '_' + j,
+          id: crypto.randomUUID() + '_student_table_' + i + '_' + j,
           type: 'rectangular_table',
           layerId: 'default',
           x: tableX,
@@ -307,7 +308,7 @@ class SeatingTemplateTool extends Tool {
         
         // Create chair behind each table
         this.yjsDoc.createElement({
-          id: Date.now().toString() + '_student_chair_' + i + '_' + j,
+          id: crypto.randomUUID() + '_student_chair_' + i + '_' + j,
           type: 'chair',
           layerId: 'default',
           x: tableX + tableWidth / 2 - chairWidth / 2,