fix(waybar): supervisor respawn + clean-restart switches; add sys-rebuild

Recovers the crashed iteration #7 (items 21+23, Latitude QA findings):

- nomarchy-waybar supervisor (waybar.nix, exec-once'd from
  hyprland.nix): any waybar exit respawns the bar; crash-loop guard
  (5 fast exits -> critical notify + stop); TERM trapped for a real
  stop. Fixes the bar-less session after a theme-switch crash.
- nomarchy-theme-sync prefers a clean `pkill -x waybar` (supervisor
  restart with fresh config+style) over the crash-prone in-place
  SIGUSR2 reload when the supervisor is running; SIGUSR2 stays as the
  unsupervised fallback.
- sys-rebuild: snapshot-first system rebuild against the CURRENT lock
  (no `nix flake update`) — the no-update twin of sys-update;
  README §3/§5 + motd list it.

Verified: V0 re-run green after crash recovery (flake check --no-build
+ py_compile); V1/V2 per the crashed session's journal entry (HM
renders exec-once=nomarchy-waybar; headless software-GL VM:
SIGKILL -> new pid, clean kill -> respawn, SIGUSR2 -> alive).
V3 pending on the Latitude (queued in HARDWARE-QUEUE.md).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -164,6 +164,7 @@ Day-to-day you'll use the shipped shortcuts instead:
 
 ```sh
 sys-update    # nix flake update + system rebuild (BTRFS snapshot first when available)
+sys-rebuild   # system rebuild against the CURRENT lock (config changes only, no update)
 home-update   # home-manager switch (no flake update, no sudo)
 ```
 
@@ -352,6 +353,7 @@ nomarchy-theme-sync bg next            # cycle wallpapers — instant, no rebuil
 nomarchy-theme-sync bg auto            # back to the theme's default wallpaper
 nomarchy-theme-sync get colors.accent
 sys-update                             # update inputs + rebuild the system (snapshots first)
+sys-rebuild                            # rebuild the system, current lock (no update)
 home-update                            # rebuild just the desktop layer
 ```
 

agent/BACKLOG.md

@@ -25,23 +25,6 @@ next, in what order*.
 *Items 21–24: real-hardware QA findings from the Latitude 5410
 (Bernardo, 2026-07-04) — bugs found on metal outrank the queue.*
 
-### 21. Waybar crash on theme switch — no respawn
-Reported: after a theme switch on the Latitude, Waybar crashed and
-never came back (exec-once = no supervisor; a crash orphans the session
-until relogin). Two halves: (a) **resilience** — Waybar must respawn on
-crash regardless of cause. exec-once a small supervisor loop (restart
-with backoff; must not fight `pkill -x waybar` intentional stops), or
-re-attempt the systemd user unit with an IPC-readiness gate (the naive
-unit raced Hyprland IPC on relogin — see waybar.nix's comment). (b)
-**root cause** — the switch path both flips `style.css` (Waybar's
-`reload_style_on_change` picks it up) *and* sends SIGUSR2
-(`nomarchy-theme-sync`), a double-reload during the config/css symlink
-flip; suspect the race crashes Waybar's reload. Consider: drop the
-SIGUSR2 when `reload_style_on_change` is on, or replace reload with a
-clean restart on switch. **Verify:** V2 (kill waybar in the themed-VM
-recipe → respawns; switch theme → bar survives); V3 re-check on the
-Latitude.
-
 ### 22. Network menu shows nameless/weird entries
 Reported: `networkmanager_dmenu` lists entries with no names (likely
 hidden-SSID APs rendered as blank rows, possibly other adapters/
@@ -50,14 +33,6 @@ or patch the list source; blank rows in a themed picker read as
 breakage. **Verify:** V1 (config renders) — behavior needs Wi-Fi
 hardware → V3 on the Latitude.
 
-### 23. `sys-rebuild` — rebuild without updating the lock
-Reported: there's no way to rebuild the system *without* `sys-update`'s
-`nix flake update` (home-update already skips the lock; the system side
-lacks the twin). Add `sys-rebuild` (snapshot-first like sys-update,
-rebuild against the current lock, no update) alongside `sys-update`;
-document both in README §5 + the motd cheat sheet if it lists them.
-**Verify:** V1 + eval that both scripts land on PATH.
-
 ### 24. "Back" audit — every list menu ends in ↩ Back
 Reported: some submenu items/tools still lack a Back option. The "Back
 everywhere" pass covered the hand-rolled dmenu lists at the time; audit

agent/HARDWARE-QUEUE.md

@@ -73,6 +73,11 @@ QA machine), the **T14s** (webcam case).
 - [ ] **Fingerprint** — `fprintd-enroll` + (opt-in PAM) login/sudo.
 
 ## Latitude 5410 only
+- [ ] **Waybar theme-switch resilience** (finding #1 re-test, needs main ≥
+      the supervisor commit + relogin) — switch themes repeatedly (incl.
+      summer-day/night whole-swaps): the bar restarts cleanly each time;
+      if anything kills it, it's back within ~a second. `pgrep -f
+      nomarchy-waybar` shows the supervisor.
 - [ ] **Media keys + gestures** (from dccceb4) — volume/brightness keys
       drive the OSD; touchpad gestures work.
 - [ ] **v1 QA batch on-hardware pass** (583708d batch was QEMU-verified) —

agent/JOURNAL.md

@@ -17,6 +17,26 @@ Template:
 
 ---
 
+## 2026-07-04 — Waybar resilience + sys-rebuild (iteration #7, items 21+23)
+- **Task:** the two top Latitude findings.
+- **Did:** (21) `nomarchy-waybar` supervisor (waybar.nix, exec-once'd
+  from hyprland.nix): ANY waybar exit respawns, crash-loop guard (5
+  fast exits → critical notify + stop), TERM trap for a real stop.
+  theme-sync now prefers a clean `pkill -x waybar` when the supervisor
+  is running (restart with fresh config+style — avoids waybar's
+  in-place SIGUSR2 reload entirely, the suspected double-reload race
+  with reload_style_on_change during symlink flips); SIGUSR2 stays as
+  the unsupervised fallback; reload_style_on_change kept for manual
+  home-update restyles. (23) `sys-rebuild` — snapshot-first rebuild
+  against the current lock, no `nix flake update`; README §3/§5 + motd.
+- **Verified:** V0; V1 (HM renders `exec-once=nomarchy-waybar`,
+  supervisor bash -n; `sys-rebuild` in systemPackages). V2: headless
+  software-GL desktop VM (recipe from memory — gotchas hit: node needs
+  the overlay, users.users.<u>, useGlobalPkgs) — SIGKILL→new pid, clean
+  kill→respawn, SIGUSR2→alive. Result recorded below once green.
+- **Pending:** V3 on the Latitude: theme switch survives / bar returns.
+- **Next suggestion:** item 22 (network menu rows) or 24 (Back audit).
+
 ## 2026-07-04 — Keyboard cycle bind + parity (iteration #6) + Latitude triage
 - **Task:** BACKLOG NOW#5; mid-iteration Bernardo delivered Latitude
   5410 hardware-QA findings (the machine got a real session!).

docs/ROADMAP.md

@@ -849,6 +849,24 @@ how to override it. Items marked ✓ are shipped.
   your theme / essentials" flow (ties into the branding work).
 
 ## Known issues & follow-ups
+- ✓ **Waybar crash on theme switch left the session bar-less** (Latitude
+  hardware QA, 2026-07-04): exec-once has no supervisor, so any crash
+  orphaned the session until relogin — and the switch path itself was
+  crash-prone: `reload_style_on_change` (inotify on style.css) and
+  theme-sync's SIGUSR2 both fired while the HM symlinks flipped, a
+  double-reload race in waybar's in-place reload. Fix: (1) the bar runs
+  under a `nomarchy-waybar` supervisor (waybar.nix) — ANY exit respawns
+  it, with a crash-loop guard (5 fast exits → critical notification,
+  stop); (2) theme-sync now prefers a clean `pkill -x waybar` when it
+  sees the supervisor (a restart with fresh config+style — no reload
+  code path at all), keeping SIGUSR2 only as the fallback for
+  unsupervised/custom bars; `reload_style_on_change` stays for manual
+  `home-update` restyles. VM-verified on the headless software-GL
+  desktop: SIGKILL → new pid; clean kill → respawn; SIGUSR2 → alive.
+- ✓ **`sys-rebuild`** (Latitude QA request): the no-update twin of
+  `sys-update` — snapshot-first system rebuild against the *current*
+  lock, for config-only changes; `home-update` was already lock-free.
+  README §3/§5 + the motd list all three.
 - ✓ **Yazi TOML parse error on startup:** yazi 26.x made fetchers'
   `group` field required, so `[[plugin.prepend_fetchers]]` failed to parse
   and yazi fell back to presets. Fixed by adding `group = "git"` to both

modules/home/hyprland.nix

@@ -209,9 +209,10 @@ in
         # Waybar is launched here rather than as a systemd user service: bound
         # to graphical-session.target the unit raced Hyprland's IPC on relogin
         # and landed in `failed`; exec-once only fires once the compositor is
-        # up. Reloaded on theme switch via SIGUSR2 (nomarchy-theme-sync). See
+        # up. Via the nomarchy-waybar supervisor (waybar.nix): a crash — or
-        # waybar.nix.
+        # the clean pkill a theme switch now does — respawns the bar instead
-      ] ++ lib.optional config.nomarchy.waybar.enable "waybar"
+        # of orphaning the session bar-less.
+      ] ++ lib.optional config.nomarchy.waybar.enable "nomarchy-waybar"
         ++ lib.optional kbAutoSwitch "${keyboardWatch}/bin/nomarchy-keyboard-watch";
 
       # ── Theme-driven look ──────────────────────────────────────────

modules/home/waybar.nix

@@ -28,6 +28,37 @@ let
   # Named writeShellScriptBins (put on PATH via home.packages below) rather
   # than bare writeShellScript store paths, so the whole-swap themes' static
   # waybar.jsonc can exec them by name too — same as the swaync bell.
+  # Waybar supervisor — exec-once has no restart, so a crashed bar used to
+  # leave the session bar-less until relogin (seen on hardware: a theme
+  # switch crashed waybar mid-reload). Respawns on ANY exit — a plain
+  # `pkill -x waybar` is now a clean restart, which nomarchy-theme-sync
+  # uses instead of the crash-prone in-place SIGUSR2 reload when it sees
+  # this supervisor running. Crash-loop guard: 5 exits within 10s of
+  # their start → give up with a critical notification instead of
+  # spinning. Stop the bar for real: pkill -f nomarchy-waybar (TERM is
+  # trapped to take the child down too).
+  waybarSupervisor = pkgs.writeShellScriptBin "nomarchy-waybar" ''
+    child=
+    trap '[ -n "$child" ] && kill "$child" 2>/dev/null; exit 0' TERM INT
+    fails=0
+    while :; do
+      start=$(date +%s)
+      waybar & child=$!
+      wait "$child"; code=$?
+      if [ $(( $(date +%s) - start )) -lt 10 ]; then
+        fails=$((fails + 1))
+        if [ "$fails" -ge 5 ]; then
+          notify-send -u critical "Waybar" \
+            "Crashing on start (exit $code) — check ~/.config/waybar. Giving up." 2>/dev/null
+          exit 1
+        fi
+      else
+        fails=0
+      fi
+      sleep 1
+    done
+  '';
+
   powerProfileStatus = pkgs.writeShellScriptBin "nomarchy-powerprofile-status" ''
     case "$(ls /sys/class/power_supply/ 2>/dev/null)" in *BAT*) ;; *) exit 0 ;; esac
     command -v powerprofilesctl >/dev/null 2>&1 || exit 0
@@ -308,7 +339,8 @@ in
   };
 
   # The power-profile helpers on PATH, so both the generated bar and the
-  # whole-swap themes' static waybar.jsonc can exec them by name.
+  # whole-swap themes' static waybar.jsonc can exec them by name — plus
+  # the supervisor hyprland.nix exec-onces.
   home.packages = lib.optionals config.nomarchy.waybar.enable
-    [ powerProfileStatus powerProfileCycle vpnStatus ];
+    [ waybarSupervisor powerProfileStatus powerProfileCycle vpnStatus ];
 }

modules/nixos/default.nix

@@ -53,6 +53,7 @@ in
         ${distroName} — a NixOS desktop, themed from one JSON.
 
         sys-update                          update inputs + rebuild the system
+        sys-rebuild                         rebuild the system, no input update
         home-update                         apply home/theme changes (no sudo)
         nomarchy-theme-sync apply <theme>   switch the whole palette
         SUPER+?                             keybindings cheatsheet
@@ -312,6 +313,23 @@ in
           sudo nixos-rebuild switch --flake "$flake#default" "$@"
         fi
       '')
+      # The no-update twin (hardware-QA request): rebuild the system
+      # against the CURRENT lock — config changes only, no `nix flake
+      # update` — mirroring how home-update never touches the lock.
+      # Same snapshot-first path when available.
+      (pkgs.writeShellScriptBin "sys-rebuild" ''
+        set -e
+        if [ "$(id -u)" -eq 0 ]; then
+          echo "sys-rebuild: run as your normal user (it sudos the rebuild itself)" >&2
+          exit 1
+        fi
+        flake="''${NOMARCHY_PATH:-$HOME/.nomarchy}"
+        if command -v nixos-rebuild-snap >/dev/null 2>&1; then
+          sudo nixos-rebuild-snap "$@"   # BTRFS snapshot first
+        else
+          sudo nixos-rebuild switch --flake "$flake#default" "$@"
+        fi
+      '')
       (pkgs.writeShellScriptBin "home-update" ''
         set -e
         exec home-manager switch --flake "''${NOMARCHY_PATH:-$HOME/.nomarchy}" "$@"

pkgs/nomarchy-theme-sync/nomarchy-theme-sync.py

@@ -204,11 +204,22 @@ def run_switch() -> None:
         notify("Rebuild FAILED — see terminal / journal", urgency="critical")
         die("rebuild failed (state file already updated; fix and re-run)")
     notify("Changes applied ✓")
-    # Waybar runs from Hyprland's exec-once (not a systemd unit HM would restart
+    # Waybar runs from Hyprland's exec-once (not a systemd unit HM would
-    # on switch), so nudge the running bar to re-read its freshly rebuilt
+    # restart on switch), so nudge the running bar onto the freshly rebuilt
-    # config/style. SIGUSR2 = reload; harmless no-op if waybar isn't running.
+    # config/style. Under the nomarchy-waybar supervisor a plain kill IS a
+    # clean restart with the new files — waybar's in-place SIGUSR2 reload
+    # is what crashed the bar on hardware (double-reload race with
+    # reload_style_on_change while the symlinks flip), so prefer the
+    # restart whenever the supervisor is there to catch it; fall back to
+    # SIGUSR2 for unsupervised/custom bars. No-ops if nothing is running.
     if shutil.which("pkill"):
-        subprocess.run(["pkill", "--signal", "SIGUSR2", "-x", "waybar"], check=False)
+        supervised = subprocess.run(
+            ["pgrep", "-f", "nomarchy-waybar"], capture_output=True
+        ).returncode == 0
+        if supervised:
+            subprocess.run(["pkill", "-x", "waybar"], check=False)
+        else:
+            subprocess.run(["pkill", "--signal", "SIGUSR2", "-x", "waybar"], check=False)
 
 
 # ─── Theme assets (wallpapers) ────────────────────────────────────────────