[snkiz]

The 153 private window doesn't have a mask in the corner? I added an exclusion to that rule for 153 only.

[Firnschnee]

Thanks, good catch. I checked ESR 153.7's browser.xhtml: there is no .private-browsing-indicator-button at all, only the -with-label hbox we already hide. In 160 the button is static markup in every window, so pairing [privatebrowsingmode] with :not(:has(…)) is the right test.

One problem with the approach though: the new rules (2,3,1) also outrank the #13 collapse, and #13 is on by default. In an ESR private window the collapsed cluster then keeps the full hamburger + puzzle margin, and on reveal the clearance stays a margin instead of the padding that keeps the hover bridge closed. Customize mode (:root[customizing]:not([privatebrowsingmode])) and the button-before-cluster rules (:root:not([privatebrowsingmode]) in both #13 blocks) still treat ESR private as "mask present", so they lack clearance as well.

Could you flip the existing logic instead of adding rules? Everything that assumes "the mask carries the clearance" should test for the mask, not for private mode. Then an ESR private window behaves exactly like a normal one, #13 padding included:

• zeroing rule (~3035) and both private reveal-revert rules (~3119, ~3229):
  :root[privatebrowsingmode] → :root[privatebrowsingmode]:has(#TabsToolbar .private-browsing-indicator-button)
• customize rule (~3044) and both button-before-cluster rules (~3079, ~3193):
  :not([privatebrowsingmode]) → :where(:not([privatebrowsingmode]), :not(:has(#TabsToolbar .private-browsing-indicator-button)))

The :where() keeps the specificity from climbing, so the reveal rules still beat the button rule. With that in place the two new rules can go. I haven't run this in ESR myself yet, so a quick check with #13 on and off would be great.

[snkiz]

Thanks, that is cleaner. I've reworked the branch the way you described and pushed it.

The two new rules are gone. The zeroing rule and both private reveal-revert rules now require the mask (:root[privatebrowsingmode]:has(#TabsToolbar .private-browsing-indicator-button)). The customize rule and both button-before-cluster rules wrap the negated selector in :where(), so they also match when the button is absent.

Checked in a private window on ESR 153 and Nightly, with --uc-hide-extension-icons at 1 and at 0 (so with the #13 collapse on and off). It behaves as expected in all four.

Customize mode is still clean.

[Firnschnee]

I keep it simple this time: good job! Thank you!