# Memory — durable lessons, learned the hard way

Curated, not append-only: one line per fact, newest at the top of its
section; delete entries that stop being true. Details usually live in a
docs/ROADMAP.md decision record — pointer given as (§ item). Add a fact
here the moment a debugging session teaches you something a future
iteration would otherwise rediscover.

## Testing & VM recipes
- **Doctor float V2:** `THEME=<slug> nix build --impure -f tools/doctor-float.nix`
  — softGL Hyprland, `nomarchy-menu doctor`, asserts
  `class=com.nomarchy.doctor` + `floating` + centered midpoints +
  screenshots (Kitty `--class=…`). SoftGL may still struggle with a GPU
  terminal; size can ignore percent windowrules if client geometry wins.
- **theme-shot softGL may not start Kitty** — `btop.png` is best-effort
  (usually identical to desktop). Guest asserts on
  `~/.config/btop/themes/nomarchy.theme` prove baking; the TUI look is
  hardware/GL tier (HARDWARE-QUEUE).
- **Waybar `custom/doctor` tripwire:** status helper must invoke
  `nomarchy-doctor` by **absolute store path** (waybar's env can miss
  system PATH → `command -v … || exit 0` self-hides forever); empty
  `"text"` also self-hides; strip ANSI before packing the tooltip; use
  signal 10 + `format = "{}"`. theme-shot asserts class:bad + glyph and
  pokes RTMIN+10 before the desktop shot.
- **tuigreet dies silently under runNixOSTest** (even bare, no theme
  flag: greetd sits as "(greetd)" with no child, nothing in the
  journal — its stderr goes to the VT) — nixpkgs' own greetd test uses
  agreety instead. Greeter *rendering* is interactive-ISO/hardware
  tier; don't burn another session on a checks.greeter VM test.
- In VM tests `pgrep -f PATTERN` can match the test backdoor's own
  `bash -c` wrapper (the pattern is in its cmdline) — use `pgrep -x`
  or a `[t]uigreet`-style bracket pattern.
- **Don't default a "timer/session" feature to V3 — most of it is VM-testable.**
  A scheduled/session behaviour usually decomposes into a *generic* step
  already covered elsewhere (e.g. `home-manager switch`, exercised by every
  theme apply) and a *specific* decision (which theme, when). Stub the generic
  step (`NOMARCHY_REBUILD=<marker>` for theme-sync) and **simulate time by
  moving the VM clock** (`date -s`, `timedatectl set-ntp false`, `time.timeZone
  = "UTC"`), then assert the decision + state change headlessly. `checks.auto-theme`
  does exactly this for #79's sunset/sunrise. Only the literal
  timer-fires-on-`OnCalendar` is truly on-hardware, and `systemd-analyze
  calendar` validates that schedule. (I first mis-framed #79 as V3 — it's V2.)
- **`writeShellScriptBin` scripts run `set -euo pipefail`** (nomarchy-doctor,
  the menu, lifecycle CLIs). So a **no-match `grep` inside `$(…)`** (grep exits
  1 → command-sub fails → abort) and a **standalone `cond && action`** (false
  cond → abort) both kill the script mid-run — the tell is output that stops
  before the final/verdict line with no error. Guard: `… | grep … || true`
  inside `$()`, `cmd 2>/dev/null || echo 0` for captures, and `if` instead of
  `&& action`. (#77 doctor hibernate section; caught by the checks.doctor VM
  test on first run.)
- A checks.* fixture CANNOT be a writeText/toFile state file read at
  eval time ("path … is not valid" — flake check's eval store won't
  realise it): extract the logic into a pure importable file and
  unit-test THAT (monitor-rules.nix / checks.display-profiles is the
  pattern).
- **Hibernation reference (Latitude / Newton, BACKLOG #76):** LUKS whole
  root BTRFS; `@swap` → `/swap`; file `/swap/swapfile`;
  `boot.resumeDevice` = LUKS root UUID; `resume_offset` from
  `btrfs inspect-internal map-swapfile -r`. Swap is encrypted with root
  (not a cleartext partition). No zram on that box yet — zram is additive
  for live pressure only. Installer already creates this when swapSize>0.
- CI (`.gitea/workflows/check.yml`) is **eval-tier only** (standing
  decision 2026-07-10): act_runner docker-compose on the Gitea VPS; no
  KVM there. Full VM suite is BACKLOG **FUTURE #20**, not NEXT — needs a
  separate nix+/dev/kvm runner. Container gotchas are in the workflow
  header (single-user Nix + nixbld users, `sandbox=false` for Stylix
  IFD, Nix pinned 2.31.5 vs lazy-trees, no JS actions past node20).
- The Gitea instance is **1.25.4** — `on: schedule` workflows are
  supported; bump.yml assumes the Actions token can push to `main`
  (standard Gitea behaviour, but unconfirmed until the first run lands).
- The git server is **Gitea** (gitea/act_runner via docker-compose), NOT
  Forgejo — workflows are read from `.gitea/workflows/` (or `.github/`),
  never `.forgejo/workflows/` (a whole push cycle was lost to that).
- Reusable headless VM harness: `checks.*` via runNixOSTest — existing
  examples to crib from: `distro-id` (boots + `switch-to-configuration
  dry-activate`), `hardware-toggles` (kernel cmdline/PAM assertions),
  `battery-charge-limit` (fake Mains adapter via `test_power`, real udev
  event burst while the oneshot is active; clean inactive result plus an
  `InvocationID` change proves coalesced AC re-apply). AC udev hooks for a
  settling oneshot must use `start`, never `restart`: USB-C docks emit event
  bursts and restarts SIGTERM the in-flight pass into `start-limit-hit`.
- Themed-desktop screenshots work headlessly: software-GL Hyprland
  (`LIBGL_ALWAYS_SOFTWARE` on virtio-gpu) + `machine.screenshot()` QMP
  dump — prototyped 2026-06-19, kept as the fallback for theme previews
  (§ Visual theme picker).
- Hyprland needs guest GL (`virtio-vga-gl`, `gl=on`) in interactive QEMU
  or the session won't start; black screen ≈ missing GL
  (docs/TESTING.md § gotchas). Kitty is the sole terminal (no Ghostty).
- No KVM = slow, not broken; don't read slowness as failure.

## Known-broken / watchlist
- **btrfs-assistant "segfault" was unprivileged-only** (re-diagnosed
  2026-07-04): libbtrfsutil's unprivileged subvolume iteration crashes on
  btrfs-progs 6.17.1 (upstream-fixed after); **as root it works**, and the
  pkexec launcher runs it as root. The real distro bug was **no polkit
  agent in the session** (every pkexec failed silently) — hyprpolkitagent
  now ships (hyprland.nix exec-once). `checks.snapshot-gui` guards the
  root path. Lesson: before "app X is broken", check WHO it runs as — and
  whether polkit prompts can render at all (§ Snapshot browse/restore).
- **NixOS release bump is a trap:** the discarded attempt
  (branch deleted 2026-06-22) hit a Hyprland OOM blocker; a redo is a
  deliberate `v2`, never part of routine lock bumps.
- `state.json` is git-tracked inside an 86 MB flake tree, so every
  state write re-copies the source before eval — the wallpapers-artifact
  split (BACKLOG LATER) is the decided fix (§ Faster switches).
- **Friendly theme-state load** (`modules/state-read.nix`, #66):
  `builtins.tryEval` does **not** catch `readFile`/`fromJSON` failures —
  gate with `pathExists` + empty/non-object checks before `fromJSON`.
  Subtle JSON syntax errors still surface from nlohmann (line/col);
  field schema stays in `theme.nix`. mkFlake must `builtins.seq` the
  check onto the whole return set or lazy attr access skips it.

## Design invariants
- **Dock transitions are ordered safety operations (#100):** dock in one
  `hyprctl --batch` (external on → every internal workspace moved → focus
  external → internal off); undock enables internal *before* moving anything.
  The Hyprland watcher, not a shell-pipeline subshell, owns a low-level
  `handle-lid-switch` inhibitor until the lid is physically open; startup
  cleans a validated stale process group. HDMI availability may appear only
  as `change:sink`, so fresh `monitoradded` is the intent boundary for the
  settled PipeWire/WirePlumber reprobe + sink pick; generic audio changes must
  not override a manual in-dock speaker choice.
- **Waybar status is never color-only** (item 28 sweep, iteration #69):
  every status module must distinguish its states by SHAPE (glyph) or
  presence (self-hide), never color alone — good/warn/bad collapse under
  color-blindness. When adding a state, give it a distinct glyph or gate
  the module on it; a new `class` that only recolors an existing glyph is
  a regression. Suppressed notification states (DND *and* app-inhibited)
  all use the bell-off glyph + @muted.
- **Identity themes are not traffic lights** (#69): white, vantablack,
  lumon, hackerman, matte-black, miasma — monochrome / mono-hue / earthy
  status by design. `audit-theme-design.py` tags their hue/CVD/ANSI-family
  findings `[identity]`; do not "fix" them into R/Y/G.
- **Import hierarchy ≠ ANSI** (#70): `import-palettes.py` must not set
  surface==overlay when color0==color8; light color0 is often ANSI black
  (not a chip). Roles are first-class — never bulk-reimport shipped JSON
  without a hierarchy pass.

## Gotchas (cost a debugging session once)
- **#127 forensics/method lessons (three wrong diagnoses' worth):** drive the
  real code path or measure nothing (a hand-run `dpms off` has no wake path
  watching it, so "input didn't wake it" was guaranteed); do not read output
  lists as lid positions — `/proc/acpi/button/lid/*/state` is the evidence
  (a reload can light a panel inside a shut lid, #148); and anchor forensics
  on the right boot — an *unclean boot end* (journald corruption + dirty bit
  on the next boot) is itself the incident marker, and `--list-boots` comes
  before any grep.
- **OVMF exposes /dev/fd0 as TYPE=disk (#112):** disk picker must exclude
  `/dev/fd*` and tiny sizes; sort largest-first or blind Enter picks floppy.
- **Live ISO offline theme switch (#113):** only the *default/pinned* HM
  generation is offline-safe; other presets may try to build the world —
  document the contract and fail with a network-oriented message.
- **Installer HM pre-activate needs XDG_RUNTIME_DIR (+ session bus) (#123):**
  `runuser … activate` inside `nixos-enter` has no user session. Without
  `mkdir -p /run/user/$UID` owned by the install user and
  `XDG_RUNTIME_DIR` (prefer `dbus-run-session -- activate`), dconf dies
  with Permission denied and the bake aborts mid-way — first boot looks
  unthemed / missing nm-applet even though the system installed.
- **ISO filename is `image.baseName` (#125):** volumeID alone does not rename
  `result/iso/…`; force `image.baseName` to `nomarchy-…` or the artifact
  stays `nixos-live-….iso`.
- **Install flake ref must match the ISO branch (#124):** while `v1` lags
  `main`, seed `?ref=main` (and compose-lock original) from main-built ISOs;
  `NOMARCHY_FLAKE_URL` must actually rewrite `inputs.nomarchy.url` (was set
  but unused until #124).
- Gum `filter` returns unmatched typed text by default; catalog-only pickers
  require `--strict` plus an independent exact-membership validation boundary.
- Waybar `layer: top` renders above **even real-fullscreen windows** — the
  bar draws over a fullscreen video. `layer: bottom` lets the fullscreen
  surface cover it while the exclusive zone still reserves the bar's space
  in normal tiling (trade-off: floating windows can now overlap the bar
  strip). Set in both waybar.nix and every whole-swap jsonc (item 30).
- Hyprland binds match the exact modmask: a shifted keysym (`question`)
  needs SHIFT in `mods` or the bind never fires — the keypress falls
  through to the focused window (§ item 26; caught on hardware, invisible
  to eval-tier tests).
- Never kill a Wayland session-lock client (hyprlock): its crash
  failsafe drops to a tty instead of unlocking (§ Hibernate
  double-unlock).
- rofi `element-icon size` is one value = a square cell; `WxH` silently
  collapses and non-square icons letterbox — pre-crop images square at
  build (§ Visual theme picker).
- WirePlumber 0.5 monitor rules can only early-match `device.api`;
  `device.product.name` etc. bind *after* the rule runs — surgical
  libcamera scoping is impossible (§ Webcam).
- `hyprctl switchxkblayout` is a *global* layout flip; per-device isolation
  needs `device[<name>]:kb_layout` keywords (§ Keyboard layouts).
- Waybar's clock captures the timezone at construction — a zone change
  needs SIGUSR2 (watcher in `timezone.nix`) (§ Automatic timezone).
- Waybar `persistent_workspaces` (underscore) is dead syntax silently
  ignored; the hyphen form is honoured and renders phantom workspaces
  (§ Waybar shows non-existent workspaces).
- GTK4/libadwaita/Qt6 read light/dark from the portal's
  `org.freedesktop.appearance color-scheme` (dconf), not Stylix polarity
  (§ GTK/Qt ignore the theme's mode).
- Update order matters downstream: `nomarchy-pull` (lock) then
  `nomarchy-rebuild` then `nomarchy-home`, or desktop changes are silently
  skipped against the old
  lock (README § 3).
- Hyprland 0.55 renames `stayfocused` → `stay_focused` (and similar
  underscore effects); `stayfocused 1` is `invalid field type` at parse
  (§ polkit workspace rules, 2026-07-10 hardware).
- Never gate a safety listener behind the optional feature it also serves:
  the display menu existed with no profiles while its blackout rescue did
  not. Rofi defaults to mouse-pointer output (`monitor=-5`), which is stale
  in clamshell mode; use focused output (`-1`) for keyboard-launched UI.
- Hyprland 0.53 rewrote window rules: `windowrulev2` is a hard error and
  the old rule-first `float, class:^…$` no longer parses — both surface a
  red config-error banner on the default desktop. Hyprlang legacy form is
  now `<effect> <value>, match:<prop> ^…$` (e.g. `float 1, match:class ^…$`);
  effects carry a value, matchers take `match:` (§ windowrule migration).
- grub `loadfont`s every `.pf2` in a theme dir — reuse a bundled DejaVu
  rather than shipping fonts (§ Distro branding).
- Agent instructions live vendor-neutrally in `agent/` (VERIFICATION,
  DELEGATION, THEME-DESIGN; entry AGENTS.md) — `.claude/` is a thin
  adapter (permissions + subagent defs only; skills were removed
  2026-07-11). Never `git add -A` blindly: check `git status --short`
  for genuine strangers first (`settings.local.json`, harness-dropped
  files) and commit with explicit pathspecs (§ loop hygiene).
