diff --git a/frontend/js/labs/opticsbench.js b/frontend/js/labs/opticsbench.js
index f77db02..3dda0ce 100644
--- a/frontend/js/labs/opticsbench.js
+++ b/frontend/js/labs/opticsbench.js
@@ -2551,7 +2551,7 @@ class BenchSim {
       this._mk('lens',   { xf: 0.40, f: 130, ap: 95 }),
       this._mk('screen', { xf: 0.86 }),
     ];
-    this.selectedId = null;
+    this.selectedId = '__src';   // source selected by default so its controls show on open
     this._bindEvents();
     this._ro = new ResizeObserver(() => { this.fit(); this.draw(); });
     this._ro.observe(canvas.parentElement || canvas);
@@ -4413,10 +4413,13 @@ function _benchUpdateUI() {
   if (!benchSim) return;
   const listEl = document.getElementById('bench-list');
   if (listEl) {
-    listEl.innerHTML = benchSim.elements.map(e =>
+    // permanent "Источник" chip so the source is always selectable (not only via canvas)
+    const srcChip = '<button class="preset-btn' + (benchSim.selectedId === '__src' ? ' active' : '') +
+      '" style="font-size:.68rem" onclick="benchSelect(\'__src\')">Источник</button>';
+    listEl.innerHTML = srcChip + benchSim.elements.map(e =>
       '<button class="preset-btn' + (e.id === benchSim.selectedId ? ' active' : '') +
       '" style="font-size:.68rem" onclick="benchSelect(' + e.id + ')">' + _benchElName(e) + '</button>'
-    ).join('') || '<div class="pp-hint">Пусто</div>';
+    ).join('');
   }
   const propsEl = document.getElementById('bench-props');
   if (propsEl) propsEl.innerHTML = _benchPropsHTML();
diff --git a/frontend/lab.html b/frontend/lab.html
index f1eaf0e..400a371 100644
--- a/frontend/lab.html
+++ b/frontend/lab.html
@@ -3194,6 +3194,8 @@
               <button class="preset-btn" style="font-size:.68rem" onclick="benchAdd('aperture')">+ Диафрагма</button>
               <button class="preset-btn" style="font-size:.68rem" onclick="benchAdd('screen')">+ Экран</button>
               <button class="preset-btn" style="font-size:.68rem" onclick="benchAdd('prism')">+ Призма</button>
+              <button class="preset-btn" style="font-size:.68rem" onclick="benchAdd('interface')">+ Граница</button>
+              <button class="preset-btn" style="font-size:.68rem" onclick="benchAdd('slab')">+ Пластина</button>
             </div>
             <div class="gp-section-title" style="margin-bottom:6px">Схема</div>
             <div id="bench-list" style="display:flex;flex-wrap:wrap;gap:3px;margin-bottom:8px"></div>
@@ -4844,7 +4846,7 @@
 <script src="/js/labs/graphtransform.js"></script>
 <script src="/js/labs/pendulum.js"></script>
 <script src="/js/labs/equilibrium.js"></script>
-    <script src="/js/labs/opticsbench.js?v=4"></script>
+    <script src="/js/labs/opticsbench.js?v=6"></script>
 <script src="/js/labs/isoprocess.js"></script>
 <script src="/js/labs/titration.js"></script>
 <script src="/js/labs/probability.js"></script>