6.6.2 - Theme refinements, Windows Mica/Acrylic, and tab group improvements

Fixes

Theme

• Tab shape has been restored to more closely resemble a physical tab.
• Contrast between active/inactive tabs and the navigation bar is now clearer, making them easier to differentiate.
• The active tab no longer has a blue context line at the top of the tab. You can restore it in Settings → Look & Feel → Interface Components → Tab Bar → Tab Context Line.

• Windows 11 users with supported hardware will now notice subtle translucency matching Windows Mica. If you prefer stronger translucency, you can use Windows Acrylic by setting widget.windows.mica.toplevel-backdrop to 2 in about:config.

Tab Groups

What’s improved

• New tabs stay in the right group

  • New tabs now reliably open in the same tab group as the “source” tab.
  • Placement options (after / first / last) are applied within the group, so tabs won’t “jump” out of the group at the edges.

• Collapsing the only group works as you expect

  • If you collapse the only group in a window, the browser opens a single ungrouped tab and keeps it ungrouped so the group stays collapsed.
  • This works even if the new tab briefly inherits the group during creation.

• “Cancel auto‑grouping” shortcut is dependable

  • The 1‑second cancel window works consistently.
  • Shortcut defaults: Alt+ on macOS, Ctrl+ on other platforms.
  • It no longer duplicates listeners across windows.
  • Backtick/backquote detection is robust across layouts (the Backquote key is recognized reliably).
  • Exact modifier matching (Ctrl vs Cmd vs Alt vs Shift) prevents accidental activations.

• More resilient and cleaner behavior

  • Grouping is skipped for tabs that land in a different window or have no source group.
  • We clean up timers and listeners when tabs are removed or windows close.
  • Listeners are registered across all current and future browser windows.

What didn’t change

• Your existing tab groups and settings are preserved.
• Pinned tabs are never moved into groups.
• Cross‑window grouping is not attempted (only tabs in the same window are grouped).

Reminder: Preferences you can use

• Enable/disable auto grouping: browser.tabs.autoGroupNewTabs
• Placement: browser.tabs.autoGroupNewTabs.placement (after | first | last)
• Delay (1‑second cancel window): browser.tabs.autoGroupNewTabs.delayEnabled
• Delay duration (ms): browser.tabs.autoGroupNewTabs.delayMs
• Shortcut string: browser.tabs.autoGroupNewTabs.cancelShortcut

Misc

• Recent history and top sites are available again in the address bar; they were disabled by accident in the previous release.
• Linux: Middle‑click paste in the address bar works again. A single click no longer interferes with what you’ve selected elsewhere, so middle‑click pastes the text you expect. Double‑click still selects the full address Thanks @VULONKAAZ
• This is the first release that attempts to address a long‑standing issue where, after updating, some users see an empty profile or their old profile appears hidden.