## Summary

There is no way to keep the screensaver while disabling the idle lock, and the value a user would naturally reach for to express that — `idle.lock: 0` — does the exact opposite: it locks **immediately** on idle.

Two asks in one report, because they are the same gap seen from both sides:

1. **Feature** — give `idle.lock` a real "never lock" value.
2. **Bug / footgun** — `0`, `null` and `false` all currently mean "lock instantly", which is the opposite of how every one of them reads.

## Use case

Desktop that runs long jobs unattended. The user wants the screensaver to kick in, but never wants to come back to a password prompt, and never wants the machine to suspend. Screensaver and lock are separate concepts in the shell (`omarchy-launch-screensaver` vs `omarchy-system-lock`), so wanting one without the other is coherent — there is just no way to express it.

## The footgun

`shell/plugins/services/idle/Service.qml`:

```qml
readonly property int lockTimeoutSeconds: secondsFromConfig(idleConfig.lock, defaultLockSeconds)
readonly property int firstIdleTimeoutSeconds: Math.min(screensaverTimeoutSeconds, lockTimeoutSeconds)
readonly property int lockDelaySeconds: Math.max(0, lockTimeoutSeconds - firstIdleTimeoutSeconds)
...
if (root.lockDelaySeconds === 0) lockSystem("lock-timeout-immediate")
```

With `"lock": 0`, `firstIdleTimeoutSeconds` becomes `min(screensaver, 0) = 0` and `lockDelaySeconds` is `0`, so `startIdleCycle()` calls `lockSystem("lock-timeout-immediate")` the moment idle is detected. The `IdleMonitor` timeout also collapses to `0`.

The other two intuitive spellings fail the same way, via `shell/plugins/services/idle/IdleModel.js`:

```js
function secondsFromConfig(value, fallback) {
  var n = Number(value)
  if (!isFinite(n) || n < 0) return fallback
  return Math.floor(n)
}
```

`Number(null)` and `Number(false)` are both `0` — finite and not negative — so they sail through the guard and land on the immediate-lock path. And a negative value is rejected into the 300s fallback, so there is no escape hatch there either.

Net result: of the four values a user would try to mean "off" (`0`, `-1`, `null`, `false`), three lock instantly and one silently keeps the default.

## Current workaround, and why it is not a fix

Set `idle.lock` to a value large enough that the timer never fires:

```json
{ "idle": { "screensaver": 150, "lock": 604800 } }
```

This works — the lock timer is armed for ~7 days and the cycle is cancelled the moment the screensaver is dismissed via `handleScreensaverWindowClosed` → `cancelIdleCycle`. But it is a workaround for three reasons:

- **It relies on an undocumented ceiling.** `Timer.interval` is a 32-bit int in milliseconds, so `lockDelaySeconds` must stay under ~2,147,483 (≈24.8 days) or it overflows. Nothing in `shell/README.md` tells a user this, and the natural instinct (`99999999`) is past the limit.
- **It does not express intent.** A reader of `shell.json` sees a magic number, not "locking is off".
- **`shell/README.md` §7 documents `idle.lock` as seconds only.** There is no supported spelling for the behaviour, so anyone who wants it has to read the QML.

## Suggested fix

Treat an explicit `false` (and/or `null`) as "never lock", and either accept `0` as the same thing or reject it loudly rather than treating it as instant:

```qml
readonly property bool lockEnabled: idleConfig.lock !== false
                                 && idleConfig.lock !== null
                                 && lockTimeoutSeconds > 0
```

then guard the two `lockSystem` call sites (the `lockDelaySeconds === 0` branch in `startIdleCycle`, and `lockTimer.onTriggered`) on `lockEnabled`, and skip arming `lockTimer` when it is false.

If instant-lock-on-idle is a behaviour someone actually relies on, it deserves an explicit spelling (`"lock": "immediate"`) rather than being what you get for typing the number that reads as "off".

Whatever is chosen, `shell/README.md` §7 should state it, since that section is the only place the idle schema is documented.

## Environment

- Omarchy 4.0.0.alpha
- Config: `~/.config/omarchy/shell.json` → `idle.screensaver: 150`, `idle.lock: 300` (default)
- Verified against the running shell with `omarchy-shell idle status`