working epics ioc and tested

web/src/App.tsx

@@ -15,6 +15,8 @@ export default function App() {
   const [mode, setMode] = useState<AppMode>('view');
   const [wsStatus, setWsStatus] = useState('connecting');
   const [editTarget, setEditTarget] = useState<Interface | null>(null);
+  // Interface to show when returning to view mode after editing
+  const [viewTarget, setViewTarget] = useState<Interface | null>(null);
 
   useEffect(() => {
     const unsub = wsClient.status.subscribe(setWsStatus);
@@ -36,7 +38,8 @@ export default function App() {
     setMode('edit');
   }
 
-  function exitEdit() {
+  function exitEdit(iface: Interface) {
+    setViewTarget(iface);
     setMode('view');
     setEditTarget(null);
   }
@@ -46,10 +49,14 @@ export default function App() {
       {wsStatus === 'disconnected' && (
         <div class="connection-banner">WebSocket disconnected — reconnecting…</div>
       )}
-      {mode === 'view'
-        ? <ViewMode onEdit={enterEdit} />
-        : <EditMode initial={editTarget} onDone={exitEdit} />
-      }
+      {/* ViewMode is always mounted so PlotPanel ring-buffers are never destroyed.
+          EditMode is conditionally rendered; it resets from props each time anyway. */}
+      <div style={`display:${mode === 'view' ? 'contents' : 'none'}`}>
+        <ViewMode onEdit={enterEdit} initialInterface={viewTarget} />
+      </div>
+      {mode === 'edit' && (
+        <EditMode initial={editTarget} onDone={exitEdit} />
+      )}
     </div>
   );
 }