A BlurBox isn't following its window

Quick checks

1. Is the overlay actually glued?

Right-click the overlay. If you see “Glue to Window Underneath”, the overlay isn't glued — that's the menu item to turn glue on. If you see “Unglue”, it's glued.

2. Is Accessibility permission still granted?

macOS sometimes invalidates this silently after an update. See Accessibility permission troubleshooting for the fix.

3. Did the underlying window change identity?

Some apps replace their windows under the hood:

• Chrome / Edge / Brave: tearing off a tab into a new window, or merging two windows.
• Native full-screen mode: clicking the green full-screen button moves the window into a new Space.
• Some Electron apps swap windows during view transitions.

When this happens, the overlay's “target” window no longer exists — it's tracking a window that's been replaced. The fix is to re-glue the overlay to the new window:

1. Right-click the overlay and choose “Unglue”
2. Position the overlay over the new window
3. Right-click and choose “Glue to Window Underneath”

If re-gluing doesn't help

That's a rare case worth reporting. Please tell us the exact app and situation. The more reproducible the steps, the faster we can fix it.