• Browser: Opera One 135.0.5973.66 (arm64)
• Chromium version: 151.0.7922.176
• OS: macOS Tahoe 26.5.2 (build 25F84), Apple Silicon M1 (MacBook Air)
• Display setup: MacBook internal display + 1 external monitor
• Setting involved: Settings > Video > Video detaching >
  "Make detaching transparent"

Trigger context:

• After resetting Opera (opera://settings/reset), Picture-in-Picture
  worked correctly.
• After signing back into my Opera account and letting sync run,
  the "Make detaching transparent" setting was re-enabled
  (presumably restored via settings sync), and PiP stopped working.
• A "Synchronization has encountered a problem" message also
  appeared during this episode. I have not confirmed a direct
  causal link, but it coincided with the setting being restored.

Steps to reproduce:

1. Go to Settings > Video > Video detaching
2. Enable "Make detaching transparent"
3. Open a video (reproduced on YouTube and Dailymotion)
4. Click the video's Picture-in-Picture button

Observed result:

• The PiP button visually reacts (icon changes) and the video area
  on the page turns black, as if PiP were activating.
• No floating window ever appears on screen.
• No corresponding window shows up in Mission Control (F3) either —
  so the window is not simply mispositioned or off-screen, it is
  never created at all.
• No error appears in the DevTools console when clicking the button.

Expected result:

• A floating, transparent PiP window should appear, exactly as it
  does when the "transparent" setting is disabled.

Workaround found:

1. Disable "Make detaching transparent"

2. Click PiP → window appears normally

3. Re-enable "Make detaching transparent" while the PiP window is
   already open → it becomes transparent without any issue

   This shows the transparent rendering itself works fine; the bug
   is specifically in creating a new PiP window while the
   transparent setting is already active.

Additional note: after a full reset (extensions disabled, settings
cleared), PiP works correctly. The issue reappears after signing
back in and letting account sync complete, suggesting sync restores
this "transparent" setting to its enabled state.