diff --git a/dicom-viewer/src/App.tsx b/dicom-viewer/src/App.tsx
index 4458625..4711987 100644
--- a/dicom-viewer/src/App.tsx
+++ b/dicom-viewer/src/App.tsx
@@ -3582,25 +3582,114 @@ function App({ container_id, imageStacks, autoCacheStack, annotationJson, viewer
       </div>
 
 
-      {/* Viewport grid (inside main div) */}
-      <div
-        style={{
-          position: "absolute",
-          top: 0,
-          left: 0,
-          width: "100%",
-          height: "100%",
-          display: "grid",
-          margin: 3,
-          gridTemplateRows: `repeat(${viewportGrid.rows}, 1fr)`,
-          gridTemplateColumns: `repeat(${viewportGrid.cols}, 1fr)`,
-          gap: "5px", // Increase gap for better visibility
-          zIndex: 1,
-        }}
-      >
-        {viewports}
+      {/* Main content area: viewports and right-side panel in a row so panel pushes content */}
+      <div style={{ display: 'flex', flexDirection: 'row', height: 'calc(100% - 48px)', gap: 8 }}>
+        {/* Viewport grid container — flex:1 so it shrinks when panel takes space */}
+        <div
+          style={{
+            flex: 1,
+            display: 'grid',
+            margin: 3,
+            gridTemplateRows: `repeat(${viewportGrid.rows}, 1fr)`,
+            gridTemplateColumns: `repeat(${viewportGrid.cols}, 1fr)`,
+            gap: '5px',
+            minHeight: 0,
+            minWidth: 0,
+            zIndex: 1,
+            position: 'relative',
+          }}
+        >
+          {viewports}
+        </div>
 
+        {/* Right-side panel occupies layout space when visible or pinned */}
+        <div style={{ width: stackPanelPinned || stackPanelHover ? 320 : 28, transition: 'width 220ms ease', display: 'flex', flexDirection: 'column', pointerEvents: 'none' }}>
+          {/* Reuse the existing right-side panel markup but ensure pointerEvents are enabled inside */}
+          <div style={{ pointerEvents: 'auto', width: '100%', height: '100%' }}>
+            {/* Panel (same content as before) */}
+            <div
+              onMouseEnter={() => setStackPanelHover(true)}
+              onMouseLeave={() => setStackPanelHover(false)}
+              style={{
+                height: '100%',
+                width: '100%',
+                background: '#1f2428',
+                color: '#fff',
+                boxShadow: '0 2px 14px rgba(0,0,0,0.45)',
+                borderLeft: '1px solid #2f3336',
+                transform: 'translateX(0)',
+                transition: 'transform 220ms ease',
+                display: 'flex',
+                flexDirection: 'column',
+                overflow: 'hidden',
+              }}
+            >
+              <div style={{ display: 'flex', alignItems: 'center', justifyContent: 'space-between', padding: '8px 12px', borderBottom: '1px solid #2b2f31' }}>
+                <div style={{ fontWeight: 700 }}>Stacks</div>
+                <div style={{ display: 'flex', gap: 8, alignItems: 'center' }}>
+                  <button
+                    title={stackPanelPinned ? 'Unpin panel' : 'Pin panel'}
+                    onClick={() => setStackPanelPinned(p => !p)}
+                    style={{ background: stackPanelPinned ? '#1976d2' : '#333', color: '#fff', border: 'none', padding: '6px 8px', borderRadius: 4, cursor: 'pointer' }}
+                  >
+                    {stackPanelPinned ? 'Pinned' : 'Pin'}
+                  </button>
+                  <button
+                    title="Close"
+                    onClick={() => { setStackPanelPinned(false); setStackPanelHover(false); }}
+                    style={{ background: 'transparent', color: '#fff', border: 'none', cursor: 'pointer', fontSize: 18 }}
+                  >
+                    ×
+                  </button>
+                </div>
+              </div>
 
+              <div style={{ overflowY: 'auto', padding: 8, flex: 1 }}>
+                {availableStacks.length === 0 ? (
+                  <div style={{ color: '#999', padding: 12 }}>No stacks available</div>
+                ) : (
+                  <div style={{ display: 'flex', flexDirection: 'column', gap: 6 }}>
+                    {availableStacks.map((stack, idx) => {
+                      const imageIds = Array.isArray(stack.imageIds) ? stack.imageIds : [];
+                      const label = stack.name || (stack.caseId ? `Case: ${stack.caseId}` : `Stack ${idx + 1}`);
+                      const count = imageIds.length;
+                      const invalid = !Array.isArray(imageIds) || count === 0;
+                      const isSelected = selectedStackIdx.includes(idx);
+                      return (
+                        <div
+                          key={idx}
+                          draggable={!invalid}
+                          onDragStart={e => {
+                            if (invalid) return;
+                            e.dataTransfer.setData('text/stack-idx', String(idx));
+                            e.dataTransfer.effectAllowed = 'copy';
+                          }}
+                          onClick={() => { if (!invalid) handleLoadStack(0, idx); }}
+                          style={{
+                            display: 'flex',
+                            alignItems: 'center',
+                            justifyContent: 'space-between',
+                            padding: '8px 10px',
+                            background: isSelected ? '#1976d2' : 'transparent',
+                            color: isSelected ? '#fff' : '#ddd',
+                            borderRadius: 6,
+                            cursor: invalid ? 'not-allowed' : 'pointer',
+                          }}
+                        >
+                          <div style={{ display: 'flex', flexDirection: 'column' }}>
+                            <div style={{ fontWeight: 600 }}>{label}</div>
+                            <div style={{ fontSize: 12, opacity: 0.7 }}>{count} img{count === 1 ? '' : 's'}</div>
+                          </div>
+                          <div style={{ fontSize: 12, opacity: 0.8 }}>{stack.studyId || ''}</div>
+                        </div>
+                      );
+                    })}
+                  </div>
+                )}
+              </div>
+            </div>
+          </div>
+        </div>
       </div>