Antigravity install/sign-in fails on Omarchy ("could not start in this environment", SIGKILL): RLIMIT_RTTIME=0, not T3 Code

[navderek]

If you're on Omarchy and the Antigravity provider won't work in T3 Code, this is probably the cause. It took me a long debugging session to find, so here's the short version.

Symptoms

• Install Antigravity downloads the runtime, then fails with:

  The downloaded Antigravity runtime could not start in this environment.

• Using a custom ACP executable path doesn't help. Sign in fails too.
• In ~/.t3/userdata/logs/server.trace.ndjson you'll see ACP process exited after signal SIGKILL and/or RpcClientDefect: ACP protocol terminated., with no stderr from the runtime.
• The same agy_acp_server.par works fine when you run it from a terminal. It answers initialize in about 1 s.

Cause

It isn't T3 Code, and it isn't the runtime. On Omarchy, apps launched from the shell or app launcher inherit RLIMIT_RTTIME = 0. Google's ACP runtime SIGKILLs itself, or stalls, when its real-time budget is zero.

The chain:

1. rtkit isn't installed, so the xdg-desktop-portal Realtime portal reports RTTimeUSecMax = 0.
2. PipeWire's libpipewire-module-rt applies that value (soft and hard) to its clients, including Omarchy's shell (quickshell).
3. Everything launched from the shell inherits 0/0: T3 Code, its server, and the ACP runtime.

Your terminal has unlimited, so every test you run from it passes. That's what makes this so confusing.

Check if this is you

busctl --user get-property org.freedesktop.portal.Desktop /org/freedesktop/portal/desktop \
  org.freedesktop.portal.Realtime RTTimeUSecMax
# x 0   <- affected

grep 'realtime timeout' /proc/$(pgrep -x quickshell)/limits
# Max realtime timeout  0  0  us   <- affected

You can also compare grep 'realtime timeout' /proc/<t3code pid>/limits with the same line from your shell (/proc/$$/limits).

Fix

This is fixed upstream in Omarchy (repo omacom/omarchy), but the fix wasn't in a release yet as of 4.0.6:

• Give PipeWire realtime with rtkit and stop the silent app kills omacom/omarchy#16824 adds rtkit to the base packages, plus a repair script.
• Keep Hyprland off rtkit realtime until its RT watchdog kills are fixed omacom/omarchy#17103 sets HYPRLAND_NO_RT=1, because once rtkit is installed, Hyprland 0.57 asks for real-time scheduling and can be silently SIGKILLed by the kernel watchdog (Hyprland 0.57 gets silently SIGKILLed now that rtkit is installed on x86 omacom/omarchy#17102, Real-time scheduling. Hyprland dies by SIGKILL when reconnecting HDMI hyprwm/Hyprland#16648).

Your options:

1. Wait for the Omarchy release that includes both PRs (recommended), then reboot and retry the Antigravity install in T3 Code. You can tell it's landed when /usr/share/omarchy/bin/omarchy-realtime-repair exists and grep HYPRLAND_NO_RT /usr/share/omarchy/default/uwsm/default finds a match.
2. Do it by hand now: sudo pacman -S rtkit, add export HYPRLAND_NO_RT=1 to a file in ~/.config/uwsm/env.d/, then log out and back in. Don't install rtkit without HYPRLAND_NO_RT if you're on Hyprland 0.57 or newer, or might upgrade to it.
3. Stopgap (untested): launch T3 Code from a terminal (t3code &). It then inherits the terminal's unlimited limit.

Wrapping the runtime in prlimit --rttime=... won't work. The hard limit is 0, and an unprivileged process can't raise it.

Related

• [Bug]: Antigravity install fails on Linux x86-64 — official agy_acp_server 1.1.1 is SIGKILLed at startup without a seccomp filter (upstream bug + workaround) #13842: the original report, closed because the cause is outside T3 Code. [Bug]: Antigravity provider session never opens on Linux desktop — Electron tree sets RLIMIT_RTTIME=0, agy_acp_server 1.3.0 self-SIGKILLs (confirmed root cause + wrapper) #16744 is a duplicate.
• fix(provider): scope Antigravity Linux seccomp workaround to zero realtime limits #13230: open PR for a T3 Code-side workaround when a zero RTTIME limit is detected.
• Omarchy reports of the same cause killing other apps (Electron/Chromium, Claude Desktop, SteamVR): Without rtkit, apps started from omarchy-shell inherit RLIMIT_RTTIME=0 and the kernel RT watchdog SIGKILLs them (Electron/Chromium, claude-desktop) omacom/omarchy#16348, Apps started from the Super+Space menu inherit RLIMIT_RTTIME=0 (PipeWire + portal without rtkit) and are SIGKILLed once they get a real-time thread; since 4.0.4 this kills SteamVR omacom/omarchy#12443, X web app launched from the Super+Space app menu exits silently within seconds; same web app via Super+Shift+X or a terminal is fine omacom/omarchy#11862, PipeWire runs without realtime priority on a stock install (rtkit is not included) omacom/omarchy#9390.