Keep music helper startup on demand across rig launches

armada/tasks/2027-music-helpers-on-demand.md

+---
+log: 2027
+title: "Music helpers start with the rig, not every login"
+date: 2026-09-28
+task: "SRE #122"
+tags: [tooling, performance]
+shareable: true
+---
+
+## Cap
+Reduce the laptop's non-music background cost without breaking one-click rig startup.
+
+## Manœuvre
+Changed six existing helper rows in tools/rig_units.py from login to on-demand:
+watchdog, autoroute, MIDI wiring, Bridge, gig-log and perf-tray. Normal gig-up
+still starts them, but its --ensure step no longer re-enables them at login.
+The helpers remain active for tonight. No synth/audio service was restarted.
+
+## Prise
+Mocked the actual ensure() execution: every helper starts, none gets enabled,
+and manual controller-driver units remain untouched. All six installed units
+currently report linked (installed, not enabled). Existing GUI launch unchanged.
+
+## Sel
+Disabling a service once is not an on-demand policy if the next launcher silently
+re-enables it. Put the intent in the inventory the launcher actually consumes.

tools/rig_units.py

@@ -28,19 +28,14 @@ Two structural causes, both fixed here:
 
 BOOT POLICY, and why it is a per-unit field rather than a global
 ---------------------------------------------------------------
-  "login"     enable at default.target. The reconcilers: they idle at ~0 CPU,
-              hold no audio ports, make no sound, and their whole job is to
-              re-assert a binding that something else keeps breaking. There is
-              no such thing as "too early" for them.
-  "on-demand" NOT enabled. `parvagues-sc` is the sound: it claims MIDI, opens
-              the audio graph, and its own unit deliberately refuses
-              Restart=always because audio gear must never flap. PLN launches
-              the rig on purpose; a login should not start SuperDirt.
-
-`is-enabled` returning **`linked`** means the unit file is a symlink and the
-unit is NOT enabled — it reads like a healthy word and is not one. That is the
-state `parvagues-sc` is in, correctly, and the state the watchdog was in by
-accident. `--status` spells it out rather than printing systemd's word.
+  "login"     enabled at login where explicitly desired (MIDI lens).
+  "on-demand" started by an intentional rig bring-up, not enabled at login.
+              This includes SuperDirt AND its six background helpers. The owner
+              does not perform every day; measured helper CPU is not zero.
+
+`is-enabled` returning **`linked`** means the unit is installed but NOT enabled.
+That is correct for on-demand units. The normal gig-up --ensure path must start
+these helpers without silently restoring their old every-login cost.
 """
 from __future__ import annotations
 
@@ -62,9 +57,9 @@ import sys
 #              plugged surface generation; Conflicts= makes auto-start hostile)
 SERVICES = [
     ("parvagues-sc",           "SuperDirt",   "scsynth", "on-demand", "the sound"),
-    ("parvagues-sc-watchdog",  "sc-watchdog", None,      "login",     "restarts SuperDirt if scsynth dies"),
-    ("tidal-ardour-autoroute", "autoroute",   None,      "login",     "orbits → Ardour Tidal NN tracks"),
-    ("midi-autoconnect",       "MIDI wiring", None,      "login",     "LCXL → Midi Through, return leg cut"),
+    ("parvagues-sc-watchdog",  "sc-watchdog", None,      "on-demand",     "restarts SuperDirt if scsynth dies"),
+    ("tidal-ardour-autoroute", "autoroute",   None,      "on-demand",     "orbits → Ardour Tidal NN tracks"),
+    ("midi-autoconnect",       "MIDI wiring", None,      "on-demand",     "LCXL → Midi Through, return leg cut"),
     # Added 2026-09-05, the night the LCXL3 sat untranslated while every check
     # was green: the driver only ran when a session remembered to start it. It
     # translates the v3 DAW protocol to the corpus's v2 CCs (fader → Ardour
@@ -85,18 +80,18 @@ SERVICES = [
     # Conflicts=-kills lcxl3-driver — so neither boot nor --ensure may start
     # it. Start it BY HAND only when the v2 board is plugged.
     ("lcxl-leds-watch",        "LCXL LEDs",   None,      "manual",    "the v2 surface paint (original LCXL only)"),
-    ("parvagues-bridge",       "Bridge",      None,      "login",     "dashboard + perf toolbar"),
+    ("parvagues-bridge",       "Bridge",      None,      "on-demand",     "dashboard + perf toolbar"),
     # Added 2026-08-29. Absent from this list until then, and that absence IS why
     # CosmicFest has no session log: the unit was installed 2026-07-29 and never
     # enabled, so it only ran when someone remembered to start it by hand. The
     # sessions that exist (through 2026-08-20) are exactly those manual runs.
-    # Costs 0.4% of a core at 1 Hz, so there is no reason for it to ever be off.
-    ("gig-log",                "gig-log",     None,      "login",     "1 Hz session recorder: thermals, xruns, gear, MIDI"),
+    # Start it on every rig bring-up; keep it off on non-music days.
+    ("gig-log",                "gig-log",     None,      "on-demand",     "1 Hz session recorder: thermals, xruns, gear, MIDI"),
     # Added 2026-09-05: parvagues-gear managed it but THE list didn't know it —
     # the exact "list lived in three places" failure this module exists to end.
     # Debt: its unit file still lives only in ~/.config/systemd/user (not
     # repo-owned like the others).
-    ("perf-tray",              "perf tray",   None,      "login",     "tray: what's up, perf mode, gear pause"),
+    ("perf-tray",              "perf tray",   None,      "on-demand",     "tray: what's up, perf mode, gear pause"),
     # "login", not "manual": PLN asked for the lens to be permanently present
     # ("now it should always oppen"), on top and on every desktop. On-top is a
     # window flag midiviz already sets; all-desktops is a KWin rule keyed on its
@@ -197,7 +192,7 @@ def gen_target() -> str:
 #
 # This target is deliberately NOT enabled at boot. It Wants parvagues-sc, and a
 # login must not start SuperDirt (see the boot policy note in rig_units.py).
-# The reconcilers are enabled individually, by `rig_units.py --ensure`.
+# Login-policy units alone are enabled by `rig_units.py --ensure`.
 Description=The ParVagues rig (SuperDirt + every reconciler)
 After=pipewire.service
 Wants=pipewire.service