published version in webstore

background.js

@@ -1,6 +1,9 @@
 // Let Chrome open the panel when the toolbar icon is clicked
+// Guard: some Chromium variants may not expose sidePanel
+const hasSidePanel = !!chrome.sidePanel?.setOptions;
+
 chrome.runtime.onInstalled.addListener(() => {
-    chrome.sidePanel?.setPanelBehavior?.({ openPanelOnActionClick: true });
+    if (hasSidePanel) chrome.sidePanel.setPanelBehavior?.({ openPanelOnActionClick: true });
 });
 
 // If you still want to ensure the correct path on click, setOptions ONLY:
@@ -19,7 +22,8 @@ chrome.action.onClicked.addListener(async () => {
         try { await chrome.scripting.executeScript({ target: { tabId: tab.id }, files: ['content.js'] }); } catch {}
       }
   
-    await chrome.sidePanel.setOptions({ tabId: tab.id, path: "panel.html" }); // Chrome opens it
+    await chrome.sidePanel.setOptions({ tabId: tab.id, path: "panel.html" });
+    try { await chrome.sidePanel.open({ tabId: tab.id }); } catch {}
 });
   
 // Keyboard shortcut: we do open() here (this is a user gesture)