DOM changes are cleaned up

When a Chrome extension is updated or disabled while the user has a tab open, the content script context is invalidated but any DOM elements it injected remain. Without cleanup logic, updating the extension leaves orphaned buttons, sidebars, or overlays on long-lived pages — a support and reliability failure that manifests as 'ghost UI' that does nothing when clicked. ISO 25010 reliability requirements apply: a component that cannot clean up its own side effects on context invalidation is not reliably bounded. In enterprise environments where tabs stay open for days, uncleaned DOM from invalidated extension contexts accumulates and causes user-visible breakage.

Connect a port in your content script and listen for onDisconnect to remove injected elements when the extension context is invalidated.

// src/content.js
const port = chrome.runtime.connect();
port.onDisconnect.addListener(() => {
  host.remove(); // Clean up injected UI
});

Alternatively, assign a unique data-extension-id attribute to all injected elements and remove them all via querySelectorAll in a MutationObserver callback that detects context invalidation.