Running the proton-auth application from AUR produces the following error message:
/usr/bin/…/lib64/gcc/x86_64-pc-linux-gnu/15.1.1/…/…/…/…/include/c++/15.1.1/span:302: reference std::span::operator const [_Type = const char8_t, _Extent = 18446744073709551615]: Assertion ‘__idx < size()’ failed.
Reinstalling the application and doing a full -Syu update do not yield any results.
Currently running Cinnamon-X11 as DE if that helps, but tried the Wayland version as well with the same outcome.
That message looks strange.
pacman will not install or update this package
pacman -Syu will just update your base system - nothing from the AUR
How did you install the package?
It does have some dependencies but it is basically just the pre-compiled Debian package unpacked.
The PKGBUILD on the AUR was updated a few hours ago - depending on how you install the package, you might have gotten the older cached version.
Perhaps try installing it again using makepkg?
Sorry if my report caused confusion.
The installation was done via the AUR (I use bauh as a front-end to manage AURs, flatpaks and snaps).
The pacman update was suggested as a comment in the AUR thread as the error suggests some type of mismatch with the C++ standard library versions.
I did even try using Debtap prior to finding the AUR package, but it ended giving me the same error, so I figure it’s something with my configuration or dependencies
Welcome to the forum! 
Can’t reproduce using the Manjaro unstable branch.
Every single comment there is no longer relevant. There were some previous packaging issues that were resolved.
Sorry, can’t read that. Please edit your post and use proper formatting.
Please see:
The AUR does not have a package named ‘proton-authenticator’, though it DOES have ‘proton-authenticator-bin’.
Repository : aur
Name : proton-authenticator-bin
Version : 1.0.0-3
Description : An open source and end-to-end encrypted 2FA app. Securely sync and backup your
2FA codes easily.
URL : https://proton.me/authenticator
AUR URL : https://aur.archlinux.org/packages/proton-authenticator-bin
Groups : None
Licenses : GPL-3.0-or-later
Provides : proton-authenticator
Depends On : cairo gcc-libs gdk-pixbuf2 glib2 glibc gtk3 hicolor-icon-theme libsoup3
pango webkit2gtk-4.1
Make Deps : libarchive
Check Deps : None
Optional Deps : None
Conflicts With : proton-authenticator
Maintainer : AlphaLynx
Votes : 9
Popularity : 8.767704
First Submitted : Fri, 1 Aug 2025 00:34:17
Last Modified : Mon, 4 Aug 2025 03:34:42
Out Of Date : No
It is rather important to be accurate… not least after the recent AUR debacle where a normal package was spoofed with a ‘normal-bin’ package.
Fontconfig warning: using without calling FcInit()
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/15.1.1/../../../../include/c++/15.1.1/span:302: reference std::span<const char8_t>::operator[](size_type) const [_Type = const char8_t, _Extent = 18446744073709551615]: Assertion '__idx < size()' failed.
This on Plasma (Testing) agrees with you, so this is a case where the AUR is aligned with Arch - and there are occasional failures when Arch moves on (along with the AUR) and possibly left us behind.
As previously mentioned - it’s a good idea to learn some basic Markdown, and forum editing 
Overall the solution may be to 1. Snapshot and switch to Unstable branch or 2. Wait for the C++ stars to align 
For your information, I have the same issue with proton-authenticator-bin 1.0.0.3.
We need to wait.
Kernel: 6.12.39-1-MANJARO arch: x86_64 bits: 64 compiler: gcc v: 15.1.1 Desktop: Xfce v: 4.20.1 tk: Gtk v: 3.24.48 wm: xfwm4 v: 4.20.0
I received the manjaro updates today. It works now, without a reinstall of proton-authenticator-bin. Thanks for your work.
Thank you all for the participation and feedback.
I can now confirm that with the latest stable update of the gcc packages proton-authenticator-bin 1.0.0.3 is now able to open and function.