How to make fcitx5 use my user-level XCompose file?

[postsolar]

Hi, my initial problem really was Chromium/Electron apps not using system/user XCompose at all (apparently they use their own set of compose sequences).

I found this Chromium bug report and understood the current workaround to be to use an IMF.

I installed fcitx5 and now Chrome does use system XCompose, but I can't figure out how to make fcitx5 use my user XCompose as well (it doesn't respect it in any app). I can't find any issues discussing this, so I guess it was supposed to "just work"?

I use an env var XCOMPOSEFILE poiting to custom location (which does work, except for, as mentioned, Electron), but I also tried copying the file ~/.XCompose, and neither of these work.

fcitx5-diagnose.txt

WM info:

Hyprland 0.48.0 built from branch  at commit a3b96961a2d89b0a2e213f9dcf755e4cab98ac1d  ().
Date: 2025-04-20
Tag: v0.48.0, commits: 
built against:
 aquamarine 0.8.0
 hyprlang 0.6.1
 hyprutils 0.6.0
 hyprcursor 0.1.12
 hyprgraphics 0.1.3

fcitx version is 5.1.12

It's launched as a systemd user service with no arguments.