hl.on("hyprland.start", function() hl.exec_cmd(...) end) causes programs to exhibit different behavior compared to being launched with hyprctl dispatch 'hl.dsp.exec_cmd(...)'

[tt0fu]

After updating to 0.55 and rewriting my config in lua, some apps that I have set up to autostart with hyprland started exhibiting strange behavior:

• Steam does not autostart. Logging shows bwrap: Unexpected capabilities but not setuid, old file caps config?. Launching it from the terminal or with hyprctl dispatch launches steam just fine.
• Quickshell seems to work fine until I try to launch Steam or OBS studio from it's desktop entry launcher. Steam, again, does not launch. OBS studio does not spawn the pipewire capture portal. Launching quickshell from the terminal or from hyprctl dispatch fixes these issues.

Here are quickshell logs from it being launched via terminal, hyprctl dispatch and hl.on:
quickshell-terminal.txt
quickshell-dispatch.txt
quickshell-hl-on.txt
The hl.on launch clearly throws dbus errors which the terminal and hyprctl dispatch launches do not throw.

OS: NixOS 26.05 (unstable branch)
Version:

Hyprland 0.55.2 built from branch v0.55.2-b at commit 39d7e209c79d451efab1b21151d5938289da838d clean (version: bump to 0.55.2).
Date: 2026-05-16
Tag: v0.55.2, commits: -1

Libraries:
Hyprgraphics: built against 0.5.1, system has unknown
Hyprutils: built against 0.13.1, system has unknown
Hyprcursor: built against 0.1.13, system has unknown
Hyprlang: built against 0.6.8, system has unknown
Aquamarine: built against 0.11.0, system has unknown

Version ABI string: 39d7e209c79d451efab1b21151d5938289da838d_aq_0.11_hu_0.13_hg_0.5_hc_0.1_hlg_0.6
flags set:
nix

[tt0fu]

My hyprland config:
hyprland.lua
My full NixOS config: https://github.com/tt0fu/nixos-config

[goon]

I'm having some similar issues but pretty much exactly what you're experiencing too with Quickshell.

hl.exec_cmd("setpriv --ambient-caps -all quickshell")

Solved the issue for me of Quickshell not launching specific applications especially anything sandboxed or that uses Bubblewrap.
If that works for you I'll explain what I think is going on.

[tt0fu]

I'm having some similar issues but pretty much exactly what you're experiencing too with Quickshell.

hl.exec_cmd("setpriv --ambient-caps -all quickshell")

Solved the issue for me of Quickshell not launching specific applications especially anything sandboxed or that uses Bubblewrap. If that works for you I'll explain what I think is going on.

Adding this fixed both steam and quickshell. Thanks a lot. I would like to hear your idea on the cause of this bug. I'll leave this open until this bug gets addressed.

[goon]

Awesome! From what I understand the executor isn't dropping capabilities and because of how NixOS configures security wrappers the capabilities are then injected into the processes ambient capability set. Everything auto started via Hyprland is inheriting CAP_SYS_NICE and CAP_SETPCAP amongst whatever else.

A lot of sandboxed applications, flatpaks and especially those using bubblewrap like Steam have a strict security check that will just refuse to run the application if it inherits any capabilities it's not expecting. That's what you're seeing with the Unexpected capabilities error.

The flags provided just strip the capabilities from the autostart processes before they're launched which is effectively what Hyprland should be doing internally.

[wabarTM]

this?
#14839