Decision — desk and deskd

Status: accepted 2026-10-13. Follows the multi-call precedent of rec and play; within the naming rules of the source layout (AGENTS.md §3).

The decision

• desk is the desktop's applications in one binary. The GUI apps (busviewer, ced, dopus, prefs, screenshot, backdrop, and term when it lands) build into one executable, desk. Each app's name is a link to it in /opt/mixos/bin, and the binary runs the app it was started as. desk <app> [args] does the same, and desk alone lists the apps.
• deskd is the desktop's session services in one binary, by the same rule: the services a desktop session runs and a headless host does not (portald, settingsd, editd). Each keeps its name as a link and its own unit.
• What stays separate:
  • mix (the shell, on every host);
  • noded (the broker, on every host, desktop or not);
  • hostd (the host's information and privilege service, on every host). It runs as root and is the one way to elevate: it never shares a binary with deskd or anything else that runs as the session account;
  • compd (the compositor: its robustness and its dependency set are its own).
• Each app and service is still its own process. A crash ends one app, not the others; units, desktop entries and scripts keep calling /opt/mixos/bin/<name>.
• Each crate keeps a run entry point and its own main, so cargo run -p ced and every per-app test work as before. The multi-call crates only dispatch. Identity (build info, app ID, version) is passed by each app's run, never taken from the multi-call crate's package.

Why

Every egui app links its own egui, wgpu, naga, fonts and icons: about 22 MB of each binary is that shared runtime, and an app's own code is 1 to 3 MB. A measured prototype put six apps (backdrop, busviewer, ced, dopus, prefs, screenshot; release profile, fat LTO) in one binary: 128.7 MB separately, 29.4 MB together. Link-time optimisation removes the duplicates, and running apps share one mapped executable, so the runtime is in memory once.

Rust dynamic libraries were rejected: there is no stable Rust ABI, libstd would ship as a shared library, LTO stops at the boundary, and generic code is still copied into each app. A C-ABI wrapper around egui would be a second UI API.

The names

• desk and deskd are plain nouns, a pair in the <role>d convention (§3.1, §3.4), unique in the dependency graph, and installed by no Arch package (checked 2026-10-13; the other distributions' file lists are checked before first use).

• The layers read in order:

  • MixOS is the system.
  • mix is its shell and language.
  • noded is the broker on every host.
  • hostd is the host's information and privileged actions, as root, on every host.
  • compd, desk and deskd are the desktop.

  A headless host runs mix, noded and hostd; a desktop adds the other three.

• A machine running the desktop is "a desk"; numbered instances (a desk and its number) are names of machines, not of these binaries.

Not decided here

When each app and service moves in, the install layout of the links, and how component_install.mix and the unit collector treat a multi-call binary. Those land with the implementation.