Zen builds on Firefox and layers its own interface over Gecko. Working in it means reading a large codebase you did not write, finding the one place a piece of state goes wrong, and changing as little as possible around it.
Merged
| PR | Fix |
|---|---|
| #13460 | Clear the pending attribute on synced tabs (gh-12142) |
| #12481 | Hide the folder icon remove action when no icon is set |
| #12470 | Keep the app menu fullscreen button visible under localized labels |
| #12468 | Fix screenshot actions hidden behind Glance |
The shape of these bugs
None of the four are algorithmic. Each is a piece of interface state that disagrees with what the user can see: a control offering to remove an icon that is not there, or a button that vanishes once a translation lengthens its label.
Bugs like these survive review because the person writing the feature tests it in one language, at one window size, in the state they built it in. Thousands of users then open the browser in configurations the author did not try.
The synced-tabs fix is the one I would point at. A tab arrives from another device carrying a pending attribute, and nothing clears it once the tab loads, so the browser goes on treating a loaded tab as unloaded.
The fork
I keep a personal fork at AndreNijman/my-zen for trying changes before they become pull requests. Zen itself is MPL 2.0.