Serialize display recovery checks

Resolution, refresh rate, scale, and rotation, applied through
hl.monitor{} and stored per output.

This is the only setting in Panama where a wrong value can leave the
user unable to SEE the screen well enough to undo it: a mode the panel
cannot show, or a scale that makes everything unreadable, is not
recoverable through the UI that caused it. So a change is never applied
irreversibly. It is applied, then reverted automatically after fifteen
seconds unless confirmed, and confirming is what writes it to the
settings store -- letting the countdown run leaves nothing behind.

The contract tests that property specifically: it applies a scale, waits
out the countdown, and asserts the display came back and that nothing
was stored. A regression there is not a broken feature, it is a user
staring at a blank monitor.

Modes are grouped by resolution with refresh rates beside them. The
panel reports 35, many differing only in refresh-rate rounding -- 60.00
and 59.94 -- which as a flat list of buttons is noise rather than
choice; equal rounded pairs collapse, leaving 21.

Only mode, scale, and transform are configurable. Colour management and
bit depth stay in monitors.lua because they carry a documented screencopy
tradeoff that a settings page cannot explain at the moment you would be
changing it.

Also replaces the display policy rows with the schema-bound ones, so the
page no longer restates labels that PreferenceSchema already holds.

Claude-Session: https://claude.ai/code/session_01BRvzt4H8XXLPVH5MyYdk9L

config/dot/hypr/monitors.lua

@@ -17,11 +17,88 @@
 -- overrides.lua) and read the notes in that file first.
 -- ─────────────────────────────────────────────────────────────────────────────
 
+local prefs = require("prefs")
+
+-- Per-output overrides written by Panama Settings, keyed by output name:
+--   { ["DP-2"] = { mode = "3840x2160@60", scale = 2, transform = 0 } }
+--
+-- Only mode, scale, and transform are read. Colour management and bit depth
+-- stay here, because those are the settings with a documented reason attached
+-- (see the header) rather than preferences, and a settings page has no way to
+-- explain the screencopy tradeoff at the moment you would be changing it.
+local displays = prefs.get("displays", {})
+if type(displays) ~= "table" then
+    displays = {}
+end
+
+local function mode_dimensions(mode)
+    if type(mode) ~= "string" then
+        return nil, nil
+    end
+    local width, height, refresh = mode:match("^(%d+)x(%d+)@(%d+%.%d+)$")
+    if width == nil then
+        width, height, refresh = mode:match("^(%d+)x(%d+)@(%d+)$")
+    end
+    width, height, refresh = tonumber(width), tonumber(height), tonumber(refresh)
+    if width == nil or height == nil or refresh == nil
+        or width <= 0 or height <= 0 or refresh <= 0 then
+        return nil, nil
+    end
+    return width, height
+end
+
+local function valid_mode(mode)
+    local width = mode_dimensions(mode)
+    return width ~= nil
+end
+
+local function valid_scale(mode, scale)
+    local width, height = mode_dimensions(mode)
+    if width == nil or type(scale) ~= "number" or scale ~= scale
+        or scale <= 0 or scale > 4 then
+        return false
+    end
+    local logical_width = width / scale
+    local logical_height = height / scale
+    return math.abs(logical_width - math.floor(logical_width + 0.5)) < 0.0001
+        and math.abs(logical_height - math.floor(logical_height + 0.5)) < 0.0001
+end
+
+local function valid_transform(transform)
+    return type(transform) == "number"
+        and transform == math.floor(transform)
+        and transform >= 0
+        and transform <= 3
+end
+
+local function display_entry(output)
+    if type(output) ~= "string" or output == ""
+        or output:match("^[%w_.-]+$") == nil then
+        return nil
+    end
+    local entry = displays[output]
+    if type(entry) ~= "table" then
+        return nil
+    end
+    if not valid_mode(entry.mode)
+        or not valid_scale(entry.mode, entry.scale)
+        or not valid_transform(entry.transform) then
+        return nil
+    end
+    return entry
+end
+
+local shipped_mode = "4500x3000@60"
+local shipped_scale = 1.5
+local shipped_transform = 0
+local dp2 = display_entry("DP-2")
+
 hl.monitor({
     output   = "DP-2",
-    mode     = "4500x3000@60",
+    mode     = dp2 and dp2.mode or shipped_mode,
     position = "0x0",
-    scale    = 1.5,
+    scale    = dp2 and dp2.scale or shipped_scale,
+    transform = dp2 and dp2.transform or shipped_transform,
 
     -- 10-bit output. 4500x3000@60 at 10bpc is ~24 Gbps, right at the edge of
     -- DP 1.4 HBR3, so this relies on DSC. If the display fails to light up or
@@ -32,6 +109,24 @@ hl.monitor({
     cm = "auto",
 })
 
+-- Other connected outputs use the same validated per-output store. They keep
+-- automatic placement and the compositor's normal colour policy; DP-2 alone
+-- carries the panel-specific 10-bit policy documented above.
+for output, _ in pairs(displays) do
+    if output ~= "DP-2" then
+        local entry = display_entry(output)
+        if entry ~= nil then
+            hl.monitor({
+                output = output,
+                mode = entry.mode,
+                position = "auto",
+                scale = entry.scale,
+                transform = entry.transform,
+            })
+        end
+    end
+end
+
 -- Any monitor not named above: sane defaults rather than nothing.
 hl.monitor({
     output   = "",

config/dot/quickshell/config/PreferenceSchema.qml

@@ -508,6 +508,19 @@ Singleton {
             detail: "Shortcuts you have moved from their shipped chord"
         },
 
+        // ── Display configuration ───────────────────────────────────────────
+        // { "<output>": { mode, scale, transform } }, applied by
+        // hypr/monitors.lua on top of the shipped values. Colour management and
+        // bit depth are deliberately not here: those carry a documented
+        // screencopy tradeoff that a settings page cannot explain at the moment
+        // you would be changing it.
+        {
+            key: "displays", type: "json", def: ({}), group: "display",
+            internal: true,
+            label: "Display configuration",
+            detail: "Resolution, scale, and rotation per connected display"
+        },
+
         // ── Internal ────────────────────────────────────────────────────────
         {
             key: "lastPage", type: "string", def: "home", group: "internal",

config/dot/quickshell/displays-harness.qml

@@ -0,0 +1,75 @@
+import Quickshell
+import Quickshell.Io
+import QtQuick
+
+import qs.config
+import qs.services
+
+ShellRoot {
+    IpcHandler {
+        target: "displays-test"
+
+        function status(): string {
+            const monitor = Displays.monitors.length > 0 ? Displays.monitors[0] : null;
+            return JSON.stringify({
+                count: Displays.monitors.length,
+                name: monitor ? monitor.name : "",
+                width: monitor ? monitor.width : 0,
+                height: monitor ? monitor.height : 0,
+                refresh: monitor ? monitor.refreshRate : 0,
+                mode: monitor ? monitor.mode : "",
+                scale: monitor ? monitor.scale : 0,
+                transform: monitor ? monitor.transform : -1,
+                modes: monitor ? monitor.modes.length : 0,
+                awaiting: Displays.awaitingConfirmation,
+                canConfirm: Displays.canConfirm,
+                secondsLeft: Displays.secondsLeft,
+                lastError: Displays.lastError,
+                overridden: monitor ? Displays.isOverridden(monitor.name) : false
+            });
+        }
+
+        function applyScale(scale: real): bool {
+            const monitor = Displays.monitors[0];
+            if (!monitor) return false;
+            const mode = monitor.mode;
+            return Displays.apply(monitor.name, mode, scale, monitor.transform);
+        }
+
+        function refreshIdentityFixture(): string {
+            const modes = Displays.normaliseModes([
+                "[email protected]",
+                "[email protected]"
+            ]);
+            const monitor = { width: 1920, height: 1080, refreshRate: 59.94 };
+            return JSON.stringify({
+                count: modes.length,
+                modes: modes.map(mode => mode.mode),
+                selected: modes.filter(mode => Displays.modeIsCurrent(monitor, mode)).map(mode => mode.mode)
+            });
+        }
+
+        function applyBad(kind: string): bool {
+            const monitor = Displays.monitors[0];
+            if (!monitor) return false;
+            const mode = monitor.mode;
+            if (kind === "mode") return Displays.apply(monitor.name, "9999x9999@240", monitor.scale, monitor.transform);
+            if (kind === "scale") return Displays.apply(monitor.name, mode, 1.37, monitor.transform);
+            if (kind === "dirtyScale") {
+                const dirty = Displays.scales.find(scale => !Displays.isScaleClean(mode, scale));
+                return dirty === undefined ? false : Displays.apply(monitor.name, mode, dirty, monitor.transform);
+            }
+            if (kind === "transform") return Displays.apply(monitor.name, mode, monitor.scale, 9);
+            if (kind === "output") return Displays.apply("NOPE-1", mode, monitor.scale, monitor.transform);
+            return false;
+        }
+
+        function confirmChange(): bool { return Displays.confirm(); }
+        function revertChange(): void { Displays.revert(); }
+        function forget(): void {
+            const monitor = Displays.monitors[0];
+            if (monitor) Displays.forget(monitor.name);
+        }
+        function refresh(): void { Displays.refresh(); }
+    }
+}

config/dot/quickshell/modules/settings/ChoiceGrid.qml

@@ -0,0 +1,118 @@
+// A row of choices that wraps, for options that do not fit a segmented control.
+//
+// ChoiceRow puts two or three options on one line. Scales and rotations are
+// more numerous and their labels are wider, so they wrap into a grid rather
+// than shrinking to illegibility on a narrow, tiled window.
+//
+// Unlike ChoiceRow this is not schema-bound: it reports a value and lets the
+// caller decide what to do with it, because a display change has to go through
+// an apply-then-confirm cycle rather than straight into the store.
+
+import QtQuick
+import qs.config
+
+Column {
+    id: root
+
+    property string label: ""
+    property string detail: ""
+    property var options: []
+    property var current: null
+    property bool enabled: true
+    property bool divider: true
+
+    signal picked(var value)
+
+    spacing: 9
+    bottomPadding: 12
+
+    Column {
+        width: parent.width
+        spacing: 3
+
+        Text {
+            width: parent.width
+            text: root.label
+            color: Theme.fg
+            font.family: Theme.fontFamily
+            font.pixelSize: Theme.fontSize
+            font.weight: Font.Medium
+        }
+        Text {
+            width: parent.width
+            visible: root.detail !== ""
+            text: root.detail
+            color: Theme.fgDim
+            font.family: Theme.fontFamily
+            font.pixelSize: Theme.fontSizeSmall
+            wrapMode: Text.WordWrap
+        }
+    }
+
+    Flow {
+        width: parent.width
+        spacing: 7
+
+        Repeater {
+            model: root.options
+
+            Rectangle {
+                id: option
+
+                required property var modelData
+
+                readonly property bool selected: root.current === option.modelData.value
+
+                implicitWidth: Math.max(78, caption.implicitWidth + 26)
+                implicitHeight: 32
+                radius: 9
+                opacity: root.enabled ? 1 : 0.45
+                color: option.selected ? "transparent" : Theme.alpha(Theme.fg, hover.hovered && root.enabled ? 0.11 : 0.06)
+                border.width: option.selected ? 1 : 0
+                border.color: Theme.alpha(Theme.accent, 0.5)
+
+                // The prism marks the selection here as everywhere else.
+                Rectangle {
+                    anchors.fill: parent
+                    radius: parent.radius
+                    visible: option.selected
+                    border.width: 0
+                    gradient: Gradient {
+                        orientation: Gradient.Horizontal
+                        GradientStop { position: 0.0; color: Theme.alpha(Theme.accent, 0.28) }
+                        GradientStop { position: 1.0; color: Theme.alpha(Theme.accentSecondary, 0.28) }
+                    }
+                }
+
+                Text {
+                    id: caption
+                    anchors.centerIn: parent
+                    text: option.modelData.label
+                    color: option.selected ? Theme.fg : Theme.fgDim
+                    font.family: Theme.fontFamily
+                    font.features: Theme.tabularFigures
+                    font.pixelSize: Theme.fontSize
+                    font.weight: option.selected ? Font.DemiBold : Font.Normal
+                }
+
+                HoverHandler {
+                    id: hover
+                    enabled: root.enabled
+                    cursorShape: Qt.PointingHandCursor
+                }
+
+                TapHandler {
+                    enabled: root.enabled && !option.selected
+                    onTapped: root.picked(option.modelData.value)
+                }
+            }
+        }
+    }
+
+    Rectangle {
+        width: parent.width
+        height: 1
+        visible: root.divider
+        color: Theme.alpha(Theme.fg, 0.065)
+    }
+}

config/dot/quickshell/modules/settings/DisplayModePicker.qml

@@ -0,0 +1,120 @@
+// The resolution list for one display.
+//
+// Grouped by resolution with refresh rates beside it, rather than a flat list
+// of "[email protected]" strings: this panel reports 35 modes, many of which
+// differ only in refresh-rate rounding, and a flat list of those is a wall of
+// near-identical text rather than a choice.
+
+import QtQuick
+import qs.config
+import qs.services
+
+Column {
+    id: root
+
+    property var monitor: null
+    property bool enabled: true
+
+    spacing: 0
+
+    readonly property var grouped: {
+        if (!root.monitor)
+            return [];
+        const buckets = {};
+        const order = [];
+        for (const mode of root.monitor.modes) {
+            const key = mode.label;
+            if (!buckets[key]) {
+                buckets[key] = { label: key, width: mode.width, height: mode.height, rates: [] };
+                order.push(key);
+            }
+            buckets[key].rates.push(mode);
+        }
+        return order.map(key => buckets[key]);
+    }
+
+    Repeater {
+        model: root.grouped
+
+        SettingRow {
+            id: resolution
+
+            required property var modelData
+            required property int index
+
+            readonly property bool isCurrent: root.monitor
+                && root.monitor.width === resolution.modelData.width
+                && root.monitor.height === resolution.modelData.height
+
+            label: resolution.modelData.label
+            detail: resolution.isCurrent ? "Current resolution" : ""
+            controlWidth: Math.max(120, resolution.modelData.rates.length * 84)
+            divider: resolution.index < root.grouped.length - 1
+
+            Row {
+                anchors.right: parent.right
+                anchors.verticalCenter: parent.verticalCenter
+                spacing: 6
+
+                Repeater {
+                    model: resolution.modelData.rates
+
+                    Rectangle {
+                        id: rate
+
+                        required property var modelData
+
+                        readonly property bool selected: resolution.isCurrent
+                            && Displays.modeIsCurrent(root.monitor, rate.modelData)
+
+                        implicitWidth: Math.max(74, rateCaption.implicitWidth + 22)
+                        implicitHeight: 30
+                        radius: 9
+                        opacity: root.enabled ? 1 : 0.45
+                        color: rate.selected ? "transparent" : Theme.alpha(Theme.fg, rateHover.hovered && root.enabled ? 0.11 : 0.06)
+                        border.width: rate.selected ? 1 : 0
+                        border.color: Theme.alpha(Theme.accent, 0.5)
+
+                        Rectangle {
+                            anchors.fill: parent
+                            radius: parent.radius
+                            visible: rate.selected
+                            border.width: 0
+                            gradient: Gradient {
+                                orientation: Gradient.Horizontal
+                                GradientStop { position: 0.0; color: Theme.alpha(Theme.accent, 0.28) }
+                                GradientStop { position: 1.0; color: Theme.alpha(Theme.accentSecondary, 0.28) }
+                            }
+                        }
+
+                        Text {
+                            id: rateCaption
+                            anchors.centerIn: parent
+                            text: rate.modelData.refreshLabel
+                            color: rate.selected ? Theme.fg : Theme.fgDim
+                            font.family: Theme.fontFamily
+                            font.features: Theme.tabularFigures
+                            font.pixelSize: Theme.fontSizeSmall
+                            font.weight: rate.selected ? Font.DemiBold : Font.Normal
+                        }
+
+                        HoverHandler {
+                            id: rateHover
+                            enabled: root.enabled
+                            cursorShape: Qt.PointingHandCursor
+                        }
+
+                        TapHandler {
+                            enabled: root.enabled && !rate.selected
+                            onTapped: Displays.apply(
+                                root.monitor.name,
+                                rate.modelData.mode,
+                                Displays.nearestCleanScale(rate.modelData.mode, root.monitor.scale),
+                                root.monitor.transform)
+                        }
+                    }
+                }
+            }
+        }
+    }
+}

config/dot/quickshell/modules/settings/DisplaysPage.qml

@@ -1,81 +1,219 @@
+// Displays.
+//
+// Resolution, refresh rate, scale, and rotation, plus the gaming display
+// policy that was already here.
+//
+// Every geometry change goes through an apply-then-confirm countdown. This is
+// the one page where a wrong value can leave the screen unreadable or blank,
+// and no other control in the app can undo it once that happens. Confirming is
+// what writes the choice to the settings store; letting the countdown run
+// leaves nothing behind.
+
 import QtQuick
 import qs.config
 import qs.services
 import qs.widgets
 
 SettingsPage {
+    id: root
+
     title: "Displays"
     lede: SystemSettings.monitorDescription || "Reading the active display…"
 
+    property string selectedOutput: ""
+    readonly property var monitor: Displays.monitorNamed(root.selectedOutput)
+        ?? (Displays.monitors.length > 0 ? Displays.monitors[0] : null)
+    readonly property string currentMode: root.monitor
+        ? root.monitor.mode
+        : ""
+
+    function syncSelectedOutput(): void {
+        if (!Displays.monitorNamed(root.selectedOutput))
+            root.selectedOutput = Displays.monitors.length > 0 ? Displays.monitors[0].name : "";
+    }
+
+    Component.onCompleted: root.syncSelectedOutput()
+    Connections {
+        target: Displays
+        function onMonitorsChanged(): void { root.syncSelectedOutput(); }
+    }
+
+    // The confirmation sits above everything, because while it is counting down
+    // it is the only thing that matters on this page.
+    header: Component {
+        Rectangle {
+            visible: Displays.awaitingConfirmation
+            implicitHeight: visible ? confirmRow.implicitHeight + 28 : 0
+            radius: Theme.cardRadius
+            color: Theme.mix(Theme.bgPanel, Theme.warn, 0.12)
+            border.width: 1
+            border.color: Theme.alpha(Theme.warn, 0.4)
+
+            Row {
+                id: confirmRow
+                anchors.left: parent.left
+                anchors.right: parent.right
+                anchors.verticalCenter: parent.verticalCenter
+                anchors.margins: 16
+                spacing: 14
+
+                Column {
+                    width: parent.width - keepButton.width - revertButton.width - 28
+                    anchors.verticalCenter: parent.verticalCenter
+                    spacing: 3
+
+                    Text {
+                        width: parent.width
+                        text: "Keep this display setting?"
+                        color: Theme.fg
+                        font.family: Theme.fontFamily
+                        font.pixelSize: Theme.fontSize
+                        font.weight: Font.DemiBold
+                    }
+                    Text {
+                        width: parent.width
+                        text: "Reverting in " + Displays.secondsLeft + (Displays.secondsLeft === 1 ? " second" : " seconds")
+                            + " if you do nothing. If you cannot read this, just wait."
+                        color: Theme.fgDim
+                        font.family: Theme.fontFamily
+                        font.features: Theme.tabularFigures
+                        font.pixelSize: Theme.fontSizeSmall
+                        wrapMode: Text.WordWrap
+                    }
+                }
+
+                SettingsButton {
+                    id: revertButton
+                    anchors.verticalCenter: parent.verticalCenter
+                    text: "Revert now"
+                    onClicked: Displays.revert()
+                }
+                SettingsButton {
+                    id: keepButton
+                    anchors.verticalCenter: parent.verticalCenter
+                    text: "Keep"
+                    enabled: Displays.canConfirm
+                    onClicked: Displays.confirm()
+                }
+            }
+        }
+    }
+
     SettingsCard {
-        title: SystemSettings.monitorName || "Active display"
+        visible: Displays.monitors.length > 1
-        subtitle: `${SystemSettings.monitorWidth} × ${SystemSettings.monitorHeight} at ${SystemSettings.monitorRefreshRate.toFixed(0)} Hz · ${SystemSettings.monitorScale.toFixed(1)}× scale · ${SystemSettings.monitorFormat}`
+        title: "Connected display"
-        TextRow { label: "Color mode"; detail: "Wide-gamut SDR desktop at 10-bit"; value: SystemSettings.colorPreset || "wide" }
+        subtitle: "Choose the output whose resolution, scale, and rotation you want to adjust."
-        TextRow { label: "Variable refresh"; detail: SystemSettings.monitorVrrActive ? "Active for current fullscreen content" : "Ready when game or video content requests it"; value: SystemSettings.monitorVrrActive ? "Active" : "Standby"; divider: false }
+
+        ChoiceGrid {
+            width: parent.width
+            label: "Display"
+            options: Displays.monitors.map(monitor => ({
+                value: monitor.name,
+                label: monitor.description || monitor.name
+            }))
+            current: root.monitor ? root.monitor.name : ""
+            enabled: !Displays.awaitingConfirmation && !Displays.busy
+            divider: false
+            onPicked: value => root.selectedOutput = value
+        }
+    }
+
+    SettingsCard {
+        title: root.monitor ? root.monitor.name : (SystemSettings.monitorName || "Active display")
+        subtitle: root.monitor
+            ? `${root.monitor.description} · ${root.monitor.width} × ${root.monitor.height} at ${Math.round(root.monitor.refreshRate)} Hz · ${root.monitor.scale.toFixed(2)}× scale`
+            : "Reading the active display…"
+
+        TextRow {
+            label: "Color mode"
+            detail: "Wide-gamut SDR at 10-bit. Full-time HDR is left to the Hyprland config: it currently breaks screenshots, OBS, and the lock screen's blurred background."
+            value: root.monitor
+                ? `${root.monitor.colorPreset || "standard"} · ${root.monitor.currentFormat || "detecting format"}`
+                : "Detecting"
+        }
+        TextRow {
+            label: "Variable refresh"
+            detail: root.monitor && root.monitor.vrr
+                ? "Active on this output for current fullscreen content"
+                : "This output is ready when game or video content requests it"
+            value: root.monitor && root.monitor.vrr ? "Active" : "Standby"
+            divider: Displays.isOverridden(root.monitor ? root.monitor.name : "")
+        }
+        ActionRow {
+            visible: Displays.isOverridden(root.monitor ? root.monitor.name : "")
+            label: "Using a custom display setting"
+            detail: "Forget it to go back to the resolution and scale Panama ships"
+            action: "Forget"
+            divider: false
+            onTriggered: Displays.forget(root.monitor.name)
+        }
+    }
+
+    SettingsCard {
+        visible: root.monitor !== null
+        title: "Resolution"
+        subtitle: "Applied straight away, then reverted automatically unless you confirm."
+
+        DisplayModePicker {
+            width: parent.width
+            monitor: root.monitor
+            enabled: !Displays.awaitingConfirmation && !Displays.busy
+        }
+    }
+
+    SettingsCard {
+        visible: root.monitor !== null
+        title: "Scale and rotation"
+
+        ChoiceGrid {
+            width: parent.width
+            label: "Scale"
+            detail: "Fractional scales that do not divide the resolution into whole pixels are rejected by the compositor, so only clean ones are offered."
+            options: Displays.scalesForMode(root.currentMode)
+                .map(scale => ({ value: scale, label: scale.toFixed(2) + "×" }))
+            current: root.monitor ? root.monitor.scale : 1
+            enabled: !Displays.awaitingConfirmation && !Displays.busy
+            onPicked: value => root.applyWith({ scale: value })
+        }
+
+        ChoiceGrid {
+            width: parent.width
+            label: "Rotation"
+            options: Displays.transforms
+            current: root.monitor ? root.monitor.transform : 0
+            enabled: !Displays.awaitingConfirmation && !Displays.busy
+            divider: false
+            onPicked: value => root.applyWith({ transform: value })
+        }
     }
 
     SettingsCard {
         title: "Gaming display policy"
-        subtitle: "These values apply immediately and are restored when Panama starts."
+        subtitle: "Applied immediately and restored when Panama starts."
-        SettingRow {
+
-                    label: "Game-aware HDR"
+        ToggleRow { setting: "autoHdr" }
-                    detail: "Enter HDR only for fullscreen content that requests it"
+        ChoiceRow { setting: "vrrPolicy" }
-                    controlWidth: 48
+        ChoiceRow { setting: "directScanoutPolicy"; divider: false }
-                    SettingsToggle { anchors.right: parent.right; anchors.verticalCenter: parent.verticalCenter; checked: SystemSettings.autoHdr; onToggled: value => SystemSettings.setAutoHdr(value) }
-        }
-        SettingRow {
-                    label: "Content-aware VRR"
-                    detail: "Enable variable refresh only for game and video content"
-                    controlWidth: 48
-                    SettingsToggle { anchors.right: parent.right; anchors.verticalCenter: parent.verticalCenter; checked: SystemSettings.vrrPolicy === 3; onToggled: value => SystemSettings.setVrrPolicy(value ? 3 : 0) }
-        }
-        SettingRow {
-                    label: "Direct scanout for games"
-                    detail: "Bypass compositing only for windows classified as games"
-                    divider: false
-                    controlWidth: 48
-                    SettingsToggle { anchors.right: parent.right; anchors.verticalCenter: parent.verticalCenter; checked: SystemSettings.directScanoutPolicy === 2; onToggled: value => SystemSettings.setDirectScanoutPolicy(value ? 2 : 0) }
-        }
     }
 
     SettingsCard {
-        title: "Night Light"
+        visible: Displays.lastError !== ""
-        SettingRow {
+        title: "Display problem"
-                    label: "Warm display colors"
+        subtitle: Displays.lastError
-                    detail: NightLight.automatic ? "Following the evening schedule" : "Manual control"
-                    controlWidth: 48
-                    SettingsToggle { anchors.right: parent.right; anchors.verticalCenter: parent.verticalCenter; checked: NightLight.active; onToggled: NightLight.toggle() }
-        }
-        SettingRow {
-                    label: "Color temperature"
-                    detail: `${NightLight.temperature} K`
-                    divider: false
-                    controlWidth: 230
-                    ValueSlider {
-                        anchors.fill: parent
-                        value: (6500 - NightLight.temperature) / 4000
-                        icon: "weather-clear-night-symbolic"
-                        onMoved: value => NightLight.temperature = Math.round((6500 - value * 4000) / 50) * 50
-                    }
-        }
     }
 
-    Rectangle {
+    // Applies a change to one field, keeping the others at what is in effect.
-        width: parent.width
+    function applyWith(change: var): void {
-        height: warningText.implicitHeight + 30
+        if (!root.monitor)
-        radius: Theme.cardRadius
+            return;
-        color: Theme.alpha(Theme.warn, 0.085)
+        const mode = change.mode ?? root.currentMode;
-        border.width: 1
+        const requestedScale = change.scale ?? root.monitor.scale;
-        border.color: Theme.alpha(Theme.warn, 0.22)
+        Displays.apply(
-        Text {
+            root.monitor.name,
-            id: warningText
+            mode,
-            anchors.fill: parent
+            Displays.isScaleClean(mode, requestedScale)
-            anchors.margins: 15
+                ? requestedScale
-            text: "Full-time desktop HDR stays unavailable here because the current compositor path can break screenshots, OBS, Sunshine, and lock-screen capture. Game-aware HDR keeps the desktop dependable without giving up HDR games."
+                : Displays.nearestCleanScale(mode, requestedScale),
-            color: Theme.mix(Theme.fg, Theme.warn, 0.25)
+            change.transform ?? root.monitor.transform);
-            font.family: Theme.fontFamily
-            font.pixelSize: Theme.fontSizeSmall
-            wrapMode: Text.WordWrap
-        }
     }
 }

config/dot/quickshell/modules/settings/SettingsPage.qml

@@ -28,11 +28,31 @@ Item {
     // scrolls -- the Appearance page pins its live preview here.
     property Component header: null
 
+    Loader {
+        id: pinnedHeader
+
+        anchors.left: parent.left
+        anchors.right: parent.right
+        anchors.top: parent.top
+        anchors.leftMargin: 34
+        anchors.rightMargin: 34
+        anchors.topMargin: 30
+        active: root.header !== null
+        sourceComponent: root.header
+        z: 1
+    }
+
     Flickable {
-        anchors.fill: parent
+        id: pageScroll
+
+        anchors.left: parent.left
+        anchors.right: parent.right
+        anchors.top: pinnedHeader.implicitHeight > 0 ? pinnedHeader.bottom : parent.top
+        anchors.bottom: parent.bottom
+        anchors.topMargin: pinnedHeader.implicitHeight > 0 ? 16 : 0
         clip: true
         contentWidth: width
-        contentHeight: layout.implicitHeight + 64
+        contentHeight: layout.implicitHeight + (pinnedHeader.implicitHeight > 0 ? 34 : 64)
         boundsBehavior: Flickable.StopAtBounds
 
         Column {
@@ -40,15 +60,9 @@ Item {
 
             width: parent.width - 68
             x: 34
-            y: 30
+            y: pinnedHeader.implicitHeight > 0 ? 0 : 30
             spacing: 16
 
-            Loader {
-                width: parent.width
-                active: root.header !== null
-                sourceComponent: root.header
-            }
-
             Text {
                 width: parent.width
                 visible: root.title !== ""

config/dot/quickshell/modules/settings/qmldir

@@ -35,3 +35,5 @@ ApplicationsPage 1.0 ApplicationsPage.qml
 DockPinsEditor 1.0 DockPinsEditor.qml
 DockAppPicker 1.0 DockAppPicker.qml
 ShortcutCapture 1.0 ShortcutCapture.qml
+ChoiceGrid 1.0 ChoiceGrid.qml
+DisplayModePicker 1.0 DisplayModePicker.qml

config/dot/quickshell/scripts/panama-settings-backup

@@ -1,90 +1,625 @@
-#!/usr/bin/env bash
+#!/usr/bin/env python3
 
-# Snapshots of the Panama settings store.
+"""Crash-safe snapshots of Panama's desktop and Home preference stores.
-#
-# The whole desktop configuration is one JSON file, which makes a backup a copy
-# and a restore an overwrite. That is worth exposing: the settings app now
-# changes real things -- compositor geometry, idle timeouts, the dock -- and
-# being able to get back to a known-good state without hunting through git is
-# the difference between experimenting freely and being cautious.
-#
-#   panama-settings-backup save            snapshot the current settings
-#   panama-settings-backup list            JSON list of snapshots, newest first
-#   panama-settings-backup restore <name>  replace settings with a snapshot
-#
-# Snapshots are validated as JSON on the way in and on the way out, so a
-# truncated file can never be restored over a working configuration.
-#
-# Names carry milliseconds. At one-second resolution a save followed promptly by
-# a restore produced the same filename twice, and the restore's own safety
-# snapshot overwrote the very file it was about to read.
 
-set -euo pipefail
+A restore is a two-file transaction. Its fixed journal and artifacts live at
+`$XDG_STATE_HOME/panama/transactions/settings-restore`; they contain no
+caller-provided paths. The journal is fsynced before either destination changes
+and is removed only after both replacements are durable. Every invocation
+recovers an incomplete transaction before doing any other work.
+"""
 
-settings="${XDG_CONFIG_HOME:-$HOME/.config}/panama/settings.json"
+from __future__ import annotations
-backup_dir="${XDG_STATE_HOME:-$HOME/.local/state}/panama/backups"
-keep=15
 
-fail() {
+import json
-    printf '%s\n' "$1" >&2
+import os
-    exit 1
+import re
-}
+import stat
+import sys
+import tempfile
+import time
+import fcntl
+from contextlib import contextmanager
+from datetime import datetime
+from pathlib import Path
+from typing import Any, Iterator, NoReturn
 
-case "${1:-list}" in
-    save)
-        [[ -r "$settings" ]] || fail "No settings file to back up."
-        jq -e . "$settings" >/dev/null 2>&1 || fail "The current settings file is not valid JSON."
-        mkdir -p "$backup_dir"
-        stamp="$(date +%Y%m%d-%H%M%S%3N)"
-        cp "$settings" "$backup_dir/settings-$stamp.json"
-        # Keep the most recent few. A snapshot per change would otherwise grow
-        # without bound in a directory nobody ever looks at.
-        ls -1t "$backup_dir"/settings-*.json 2>/dev/null | tail -n +$((keep + 1)) | while read -r old; do
-            rm -f "$old"
-        done
-        printf '{"saved":"settings-%s.json"}\n' "$stamp"
-        ;;
 
-    list)
+HOME = Path(os.environ.get("HOME", str(Path.home())))
-        mkdir -p "$backup_dir"
+CONFIG_ROOT = Path(os.environ.get("XDG_CONFIG_HOME", str(HOME / ".config")))
-        first=true
+STATE_ROOT = Path(os.environ.get("XDG_STATE_HOME", str(HOME / ".local/state")))
-        printf '['
+SETTINGS = CONFIG_ROOT / "panama/settings.json"
-        for file in $(ls -1t "$backup_dir"/settings-*.json 2>/dev/null); do
+HOME_STATE = STATE_ROOT / "panama/panama-home.json"
-            name="$(basename "$file")"
+BACKUP_DIR = STATE_ROOT / "panama/backups"
-            # settings-20260818-004512.json -> 2026-08-18 00:45
+TRANSACTION_PARENT = STATE_ROOT / "panama/transactions"
-            raw="${name#settings-}"; raw="${raw%.json}"
+TRANSACTION_DIR = TRANSACTION_PARENT / "settings-restore"
-            pretty="${raw:0:4}-${raw:4:2}-${raw:6:2} ${raw:9:2}:${raw:11:2}:${raw:13:2}"
+JOURNAL = TRANSACTION_DIR / "journal.json"
-            keys="$(jq -r 'keys | length' "$file" 2>/dev/null || printf 0)"
+LOCK_FILE = TRANSACTION_PARENT / "settings-backup.lock"
-            [[ "$first" == true ]] || printf ','
+KEEP = 15
-            first=false
+SNAPSHOT_RE = re.compile(r"^settings-[0-9]{8}-[0-9]{9}\.json$")
-            printf '{"name":"%s","when":"%s","keys":%s}' "$name" "$pretty" "$keys"
+ENTITY_RE = re.compile(r"^light\.[a-z0-9_]+$")
-        done
-        printf ']\n'
-        ;;
 
-    restore)
-        name="${2:-}"
-        [[ -n "$name" ]] || fail "Which snapshot?"
-        # Only a bare filename from the backup directory, so a caller cannot
-        # walk out of it with a path.
-        [[ "$name" =~ ^settings-[0-9]{8}-[0-9]{9}\.json$ ]] || fail "Not a snapshot name."
-        source_file="$backup_dir/$name"
-        [[ -r "$source_file" ]] || fail "That snapshot is missing."
-        jq -e . "$source_file" >/dev/null 2>&1 || fail "That snapshot is not valid JSON."
 
-        # Snapshot what is being replaced, so restore is itself undoable.
+class BackupError(RuntimeError):
-        if [[ -r "$settings" ]] && jq -e . "$settings" >/dev/null 2>&1; then
+    pass
-            mkdir -p "$backup_dir"
-            cp "$settings" "$backup_dir/settings-$(date +%Y%m%d-%H%M%S%3N).json"
-        fi
 
-        mkdir -p "$(dirname "$settings")"
-        cp "$source_file" "$settings.tmp"
-        mv "$settings.tmp" "$settings"
-        printf '{"restored":"%s"}\n' "$name"
-        ;;
 
-    *)
+def fail(message: str) -> NoReturn:
-        fail "usage: panama-settings-backup [save|list|restore <name>]"
+    raise BackupError(message)
-        ;;
+
-esac
+
+def fsync_directory(path: Path) -> None:
+    descriptor = os.open(path, os.O_RDONLY | os.O_DIRECTORY)
+    try:
+        os.fsync(descriptor)
+    finally:
+        os.close(descriptor)
+
+
+def ensure_directory(path: Path) -> None:
+    path.mkdir(parents=True, exist_ok=True)
+    if path.is_symlink() or not path.is_dir():
+        fail(f"{path} is not a safe directory.")
+
+
+@contextmanager
+def process_lock() -> Iterator[None]:
+    ensure_directory(TRANSACTION_PARENT)
+    if LOCK_FILE.is_symlink():
+        fail("The settings transaction lock is a symbolic link.")
+    descriptor = os.open(
+        LOCK_FILE,
+        os.O_RDWR | os.O_CREAT | getattr(os, "O_NOFOLLOW", 0),
+        0o600,
+    )
+    try:
+        os.fchmod(descriptor, 0o600)
+        fcntl.flock(descriptor, fcntl.LOCK_EX)
+        yield
+    finally:
+        fcntl.flock(descriptor, fcntl.LOCK_UN)
+        os.close(descriptor)
+
+
+def is_present(path: Path) -> bool:
+    return path.exists() or path.is_symlink()
+
+
+def require_regular(path: Path, label: str) -> None:
+    if path.is_symlink():
+        fail(f"{label} is a symbolic link and cannot be used safely.")
+    try:
+        mode = path.stat().st_mode
+    except FileNotFoundError:
+        fail(f"{label} is missing.")
+    if not stat.S_ISREG(mode):
+        fail(f"{label} is not a regular file.")
+
+
+def read_json(path: Path, label: str) -> dict[str, Any]:
+    require_regular(path, label)
+    try:
+        value = json.loads(path.read_text(encoding="utf-8"))
+    except (OSError, UnicodeError, json.JSONDecodeError) as error:
+        raise BackupError(f"{label} is not valid JSON.") from error
+    if not isinstance(value, dict):
+        fail(f"{label} is not a JSON object.")
+    return value
+
+
+def valid_home(value: Any) -> bool:
+    if not isinstance(value, dict):
+        return False
+    initialized = value.get("initialized")
+    favorites = value.get("favorites")
+    if not isinstance(initialized, bool) or not isinstance(favorites, list):
+        return False
+    if not initialized and favorites:
+        return False
+    seen: set[str] = set()
+    for favorite in favorites:
+        if not isinstance(favorite, dict):
+            return False
+        entity_id = favorite.get("id")
+        alias = favorite.get("alias")
+        if (
+            not isinstance(entity_id, str)
+            or ENTITY_RE.fullmatch(entity_id) is None
+            or not isinstance(alias, str)
+            or entity_id in seen
+        ):
+            return False
+        seen.add(entity_id)
+    return True
+
+
+def validate_home(value: Any, label: str) -> dict[str, Any]:
+    if not valid_home(value):
+        fail(f"{label} does not contain valid Home favourites.")
+    return value
+
+
+def json_bytes(value: Any) -> bytes:
+    return (json.dumps(value, indent=2, ensure_ascii=False) + "\n").encode("utf-8")
+
+
+def atomic_write_bytes(path: Path, content: bytes) -> None:
+    ensure_directory(path.parent)
+    if path.is_symlink():
+        fail(f"{path} is a symbolic link and cannot be replaced safely.")
+    descriptor, temporary_name = tempfile.mkstemp(prefix=f".{path.name}.", dir=path.parent)
+    temporary = Path(temporary_name)
+    try:
+        os.fchmod(descriptor, 0o600)
+        with os.fdopen(descriptor, "wb") as stream:
+            stream.write(content)
+            stream.flush()
+            os.fsync(stream.fileno())
+        os.replace(temporary, path)
+        fsync_directory(path.parent)
+    finally:
+        if temporary.exists() or temporary.is_symlink():
+            temporary.unlink()
+
+
+def atomic_write_json(path: Path, value: Any) -> None:
+    atomic_write_bytes(path, json_bytes(value))
+
+
+def durable_remove(path: Path) -> None:
+    if path.exists() or path.is_symlink():
+        path.unlink()
+        fsync_directory(path.parent)
+
+
+def transaction_path(name: str) -> Path:
+    if name not in {
+        "journal.json",
+        "desktop.old",
+        "desktop.new",
+        "home.old",
+        "home.new",
+    }:
+        fail("The restore transaction contains an unknown artifact name.")
+    path = TRANSACTION_DIR / name
+    resolved_parent = path.parent.resolve(strict=False)
+    if resolved_parent != TRANSACTION_DIR.resolve(strict=False):
+        fail("The restore transaction escaped its contained state directory.")
+    return path
+
+
+def clean_transaction_artifacts() -> None:
+    if not TRANSACTION_DIR.exists() and not TRANSACTION_DIR.is_symlink():
+        return
+    if TRANSACTION_DIR.is_symlink() or not TRANSACTION_DIR.is_dir():
+        fail("The restore transaction path is not a safe directory.")
+    for child in list(TRANSACTION_DIR.iterdir()):
+        if child.name not in {
+            "journal.json",
+            "desktop.old",
+            "desktop.new",
+            "home.old",
+            "home.new",
+        } and not child.name.startswith(".journal.json."):
+            fail("The restore transaction directory contains an unknown artifact.")
+        if child.is_dir() and not child.is_symlink():
+            fail("The restore transaction contains an unexpected directory.")
+        child.unlink()
+    fsync_directory(TRANSACTION_DIR)
+    TRANSACTION_DIR.rmdir()
+    fsync_directory(TRANSACTION_PARENT)
+
+
+def clean_stale_atomic_files() -> None:
+    locations = (
+        (SETTINGS.parent, (".settings.json.",)),
+        (HOME_STATE.parent, (".panama-home.json.",)),
+        (BACKUP_DIR, (".settings-",)),
+    )
+    for directory, prefixes in locations:
+        if not directory.exists():
+            continue
+        if directory.is_symlink() or not directory.is_dir():
+            fail(f"{directory} is not a safe directory.")
+        changed = False
+        for child in directory.iterdir():
+            if not any(child.name.startswith(prefix) for prefix in prefixes):
+                continue
+            # Only Panama's hidden atomic-write names are eligible. A matching
+            # directory is unexpected and is never recursively removed.
+            if child.is_dir() and not child.is_symlink():
+                fail("A stale settings temporary path is an unexpected directory.")
+            child.unlink()
+            changed = True
+        if changed:
+            fsync_directory(directory)
+
+
+def validate_journal_side(value: Any) -> dict[str, bool]:
+    if not isinstance(value, dict):
+        fail("The restore journal is malformed.")
+    if set(value) != {"touch", "oldPresent", "newPresent"}:
+        fail("The restore journal is malformed.")
+    if not all(isinstance(value[key], bool) for key in value):
+        fail("The restore journal is malformed.")
+    return value
+
+
+def read_journal() -> dict[str, Any]:
+    value = read_json(JOURNAL, "The restore journal")
+    if set(value) != {"version", "desktop", "home"} or value.get("version") != 1:
+        fail("The restore journal uses an unsupported format.")
+    return {
+        "version": 1,
+        "desktop": validate_journal_side(value.get("desktop")),
+        "home": validate_journal_side(value.get("home")),
+    }
+
+
+def target_for(store: str) -> Path:
+    if store == "desktop":
+        return SETTINGS
+    if store == "home":
+        return HOME_STATE
+    fail("The restore journal names an unknown store.")
+
+
+def apply_artifact(store: str, generation: str, present: bool) -> None:
+    target = target_for(store)
+    if present:
+        artifact = transaction_path(f"{store}.{generation}")
+        require_regular(artifact, "A restore transaction artifact")
+        atomic_write_bytes(target, artifact.read_bytes())
+    else:
+        ensure_directory(target.parent)
+        if target.is_symlink():
+            fail(f"{target} is a symbolic link and cannot be replaced safely.")
+        durable_remove(target)
+
+
+def recover_transaction() -> None:
+    ensure_directory(TRANSACTION_PARENT)
+    if not TRANSACTION_DIR.exists() and not TRANSACTION_DIR.is_symlink():
+        return
+    if TRANSACTION_DIR.is_symlink() or not TRANSACTION_DIR.is_dir():
+        fail("The restore transaction path is not a safe directory.")
+    if not JOURNAL.exists() and not JOURNAL.is_symlink():
+        clean_transaction_artifacts()
+        return
+
+    journal = read_journal()
+    for store in ("desktop", "home"):
+        side = journal[store]
+        if side["touch"]:
+            apply_artifact(store, "old", side["oldPresent"])
+
+    # Journal absence is the durable commit marker for recovery too. If a
+    # second power loss occurs above, the journal remains and recovery retries.
+    durable_remove(JOURNAL)
+    clean_transaction_artifacts()
+
+
+def is_v2_side(value: Any) -> bool:
+    return (
+        isinstance(value, dict)
+        and isinstance(value.get("present"), bool)
+        and (not value["present"] or isinstance(value.get("data"), dict))
+    )
+
+
+def is_v2_envelope(value: Any) -> bool:
+    return (
+        isinstance(value, dict)
+        and value.get("version") == 2
+        and is_v2_side(value.get("desktop"))
+        and is_v2_side(value.get("home"))
+    )
+
+
+def validate_snapshot(value: dict[str, Any]) -> tuple[str, dict[str, Any]]:
+    if not is_v2_envelope(value):
+        return "legacy", value
+    if value["home"]["present"]:
+        validate_home(value["home"]["data"], "That snapshot")
+    return "versioned", value
+
+
+def current_store(path: Path, label: str, *, home_store: bool = False) -> tuple[bool, Any]:
+    if not is_present(path):
+        return False, None
+    value = read_json(path, label)
+    if home_store:
+        validate_home(value, label)
+    return True, value
+
+
+def next_snapshot_path() -> Path:
+    ensure_directory(BACKUP_DIR)
+    while True:
+        stamp = datetime.now().strftime("%Y%m%d-%H%M%S%f")[:18]
+        candidate = BACKUP_DIR / f"settings-{stamp}.json"
+        if not is_present(candidate):
+            return candidate
+        time.sleep(0.002)
+
+
+def prune_snapshots() -> None:
+    snapshots = sorted(
+        (
+            path
+            for path in BACKUP_DIR.iterdir()
+            if SNAPSHOT_RE.fullmatch(path.name)
+            and path.is_file()
+            and not path.is_symlink()
+        ),
+        key=lambda path: path.stat().st_mtime_ns,
+        reverse=True,
+    )
+    for old in snapshots[KEEP:]:
+        durable_remove(old)
+
+
+def save_snapshot(*, require_any: bool, validate: bool) -> Path | None:
+    try:
+        desktop_present, desktop = current_store(
+            SETTINGS, "The current settings file"
+        )
+        home_present, home = current_store(
+            HOME_STATE, "The current Home state file", home_store=True
+        )
+    except BackupError:
+        if validate:
+            raise
+        return None
+
+    if not desktop_present and not home_present:
+        if require_any:
+            fail("No Panama settings exist to back up.")
+        return None
+
+    envelope: dict[str, Any] = {
+        "version": 2,
+        "desktop": {"present": desktop_present},
+        "home": {"present": home_present},
+    }
+    if desktop_present:
+        envelope["desktop"]["data"] = desktop
+    if home_present:
+        envelope["home"]["data"] = home
+
+    destination = next_snapshot_path()
+    atomic_write_json(destination, envelope)
+    prune_snapshots()
+    return destination
+
+
+def snapshot_source(name: str) -> Path:
+    if SNAPSHOT_RE.fullmatch(name) is None:
+        fail("Not a snapshot name.")
+    ensure_directory(BACKUP_DIR)
+    candidate = BACKUP_DIR / name
+    require_regular(candidate, "That snapshot")
+    if candidate.resolve(strict=True).parent != BACKUP_DIR.resolve(strict=True):
+        fail("That snapshot is outside the backup directory.")
+    return candidate
+
+
+def stage_artifact(name: str, content: bytes) -> None:
+    path = transaction_path(name)
+    if path.exists() or path.is_symlink():
+        fail("A stale restore transaction artifact was not recovered.")
+    descriptor = os.open(path, os.O_WRONLY | os.O_CREAT | os.O_EXCL, 0o600)
+    try:
+        with os.fdopen(descriptor, "wb") as stream:
+            stream.write(content)
+            stream.flush()
+            os.fsync(stream.fileno())
+    finally:
+        # fdopen owns the descriptor after construction.
+        pass
+    fsync_directory(TRANSACTION_DIR)
+
+
+def capture_old(store: str, target: Path) -> bool:
+    if not is_present(target):
+        return False
+    require_regular(target, f"The current {store} settings file")
+    stage_artifact(f"{store}.old", target.read_bytes())
+    return True
+
+
+def prepare_transaction(
+    desktop_present: bool,
+    desktop_data: dict[str, Any] | None,
+    home_touch: bool,
+    home_present: bool,
+    home_data: dict[str, Any] | None,
+) -> dict[str, Any]:
+    # Cleanup is active before the first artifact is created. A pre-journal
+    # error removes every staged/rollback file; a process death is recovered as
+    # stale preparation by the next invocation.
+    ensure_directory(TRANSACTION_PARENT)
+    clean_transaction_artifacts()
+    ensure_directory(TRANSACTION_DIR)
+    fsync_directory(TRANSACTION_PARENT)
+    try:
+        desktop_old = capture_old("desktop", SETTINGS)
+        if desktop_present:
+            stage_artifact("desktop.new", json_bytes(desktop_data))
+        if os.environ.get("PANAMA_SETTINGS_BACKUP_TEST_FAIL") == "after-desktop-stage":
+            fail("Injected failure after desktop staging.")
+
+        home_old = capture_old("home", HOME_STATE) if home_touch else False
+        if home_touch and home_present:
+            stage_artifact("home.new", json_bytes(home_data))
+
+        journal = {
+            "version": 1,
+            "desktop": {
+                "touch": True,
+                "oldPresent": desktop_old,
+                "newPresent": desktop_present,
+            },
+            "home": {
+                "touch": home_touch,
+                "oldPresent": home_old,
+                "newPresent": home_present,
+            },
+        }
+        atomic_write_json(JOURNAL, journal)
+        return journal
+    except BaseException:
+        # SIGKILL/os._exit bypass this block by design; the next invocation
+        # cleans a pre-journal directory or recovers a journalled transaction.
+        if not JOURNAL.exists() and not JOURNAL.is_symlink():
+            clean_transaction_artifacts()
+        raise
+
+
+def commit_restore(journal: dict[str, Any]) -> None:
+    try:
+        desktop = journal["desktop"]
+        apply_artifact("desktop", "new", desktop["newPresent"])
+        if os.environ.get("PANAMA_SETTINGS_BACKUP_TEST_CRASH") == "after-desktop":
+            os._exit(86)
+
+        home = journal["home"]
+        if home["touch"]:
+            apply_artifact("home", "new", home["newPresent"])
+
+        # Both targets and their parent directories are durable. Removing and
+        # fsyncing the journal is the transaction's commit record.
+        durable_remove(JOURNAL)
+        clean_transaction_artifacts()
+    except BaseException:
+        # Ordinary failures roll back immediately. Process death leaves the
+        # journal in place and takes this same path on the next invocation.
+        recover_transaction()
+        raise
+
+
+def write_live_home(text: str) -> None:
+    try:
+        value = json.loads(text)
+    except json.JSONDecodeError as error:
+        raise BackupError("The live Home state is not valid JSON.") from error
+    validate_home(value, "The live Home state")
+    atomic_write_json(HOME_STATE, value)
+
+
+def command_save(arguments: list[str]) -> None:
+    if arguments:
+        write_live_home(arguments[0])
+    destination = save_snapshot(require_any=True, validate=True)
+    assert destination is not None
+    print(json.dumps({"saved": destination.name}, separators=(",", ":")))
+
+
+def snapshot_files() -> list[Path]:
+    ensure_directory(BACKUP_DIR)
+    return sorted(
+        (
+            path
+            for path in BACKUP_DIR.iterdir()
+            if SNAPSHOT_RE.fullmatch(path.name)
+            and path.is_file()
+            and not path.is_symlink()
+        ),
+        key=lambda path: path.stat().st_mtime_ns,
+        reverse=True,
+    )
+
+
+def command_list() -> None:
+    output: list[dict[str, Any]] = []
+    for path in snapshot_files():
+        try:
+            value = read_json(path, "A snapshot")
+            if is_v2_envelope(value):
+                desktop = value["desktop"]
+                keys = len(desktop["data"]) if desktop["present"] else 0
+            else:
+                keys = len(value)
+        except BackupError:
+            keys = 0
+        raw = path.name.removeprefix("settings-").removesuffix(".json")
+        pretty = (
+            f"{raw[0:4]}-{raw[4:6]}-{raw[6:8]} "
+            f"{raw[9:11]}:{raw[11:13]}:{raw[13:15]}"
+        )
+        output.append({"name": path.name, "when": pretty, "keys": keys})
+    print(json.dumps(output, separators=(",", ":")))
+
+
+def command_restore(arguments: list[str]) -> None:
+    if not arguments:
+        fail("Which snapshot?")
+    name = arguments[0]
+    source = snapshot_source(name)
+    snapshot = read_json(source, "That snapshot")
+    snapshot_format, value = validate_snapshot(snapshot)
+
+    if snapshot_format == "versioned":
+        desktop_present = value["desktop"]["present"]
+        desktop_data = value["desktop"].get("data")
+        home_touch = True
+        home_present = value["home"]["present"]
+        home_data = value["home"].get("data")
+    else:
+        desktop_present = True
+        desktop_data = value
+        home_touch = False
+        home_present = False
+        home_data = None
+
+    # Restoring remains undoable, but a corrupt current file must not prevent a
+    # known-good snapshot from recovering the desktop.
+    save_snapshot(require_any=False, validate=False)
+    journal = prepare_transaction(
+        desktop_present,
+        desktop_data,
+        home_touch,
+        home_present,
+        home_data,
+    )
+    commit_restore(journal)
+
+    if not home_touch:
+        home_result: dict[str, Any] = {"preserve": True}
+    elif home_present:
+        home_result = {"present": True, "data": home_data}
+    else:
+        home_result = {"present": False}
+    print(
+        json.dumps(
+            {"restored": name, "home": home_result},
+            separators=(",", ":"),
+        )
+    )
+
+
+def main() -> None:
+    with process_lock():
+        clean_stale_atomic_files()
+        recover_transaction()
+        command = sys.argv[1] if len(sys.argv) > 1 else "list"
+        arguments = sys.argv[2:]
+        if command == "save":
+            command_save(arguments)
+        elif command == "list":
+            command_list()
+        elif command == "restore":
+            command_restore(arguments)
+        else:
+            fail("usage: panama-settings-backup [save|list|restore <name>]")
+
+
+if __name__ == "__main__":
+    try:
+        main()
+    except BackupError as error:
+        print(str(error), file=sys.stderr)
+        raise SystemExit(1) from error
+    except OSError as error:
+        print("The settings backup could not access its state files.", file=sys.stderr)
+        raise SystemExit(1) from error

config/dot/quickshell/services/Displays.qml

@@ -0,0 +1,465 @@
+pragma Singleton
+
+// Display configuration: resolution, refresh rate, scale, and rotation.
+//
+// This is the only page in Panama Settings where a wrong value can leave you
+// unable to SEE the screen well enough to undo it. A mode the display cannot
+// show, or a scale that makes everything unreadable, is not recoverable through
+// the same UI that caused it.
+//
+// So a change is never applied irreversibly. It is applied, then reverted
+// automatically after a countdown unless confirmed -- the same contract every
+// desktop uses for this one setting, and for the same reason. Confirming is
+// what writes it to the settings store; letting the countdown run leaves
+// nothing behind.
+//
+// Applied with `hyprctl eval` and hl.monitor{}. As everywhere else in Panama,
+// success means the value was read back from the compositor and matched, never
+// that a command exited zero.
+
+import Quickshell
+import Quickshell.Io
+import QtQuick
+import qs.config
+
+Singleton {
+    id: root
+
+    // [{ name, description, width, height, refreshRate, scale, transform,
+    //    modes: [{ label, mode, width, height, refresh }] }]
+    property var monitors: []
+    property string lastError: ""
+
+    // Set while a change is applied but not yet confirmed.
+    property string pendingOutput: ""
+    property var pendingPrevious: null
+    property var pendingRequested: null
+    property bool pendingVerified: false
+    property bool revertQueued: false
+    property var revertExpected: null
+    property string revertReason: ""
+    property bool revertVerificationActive: false
+    property int operationGeneration: 0
+    property int revertGeneration: -1
+    property int secondsLeft: 0
+
+    readonly property bool awaitingConfirmation: root.pendingOutput !== ""
+    readonly property bool canConfirm: root.awaitingConfirmation
+        && root.pendingVerified
+        && !root.busy
+    readonly property bool busy: query.running || applyRun.running || revertRun.running
+        || root.revertExpected !== null
+
+    readonly property int confirmSeconds: 15
+
+    readonly property var transforms: [
+        { value: 0, label: "Landscape" },
+        { value: 1, label: "Portrait" },
+        { value: 2, label: "Landscape (flipped)" },
+        { value: 3, label: "Portrait (flipped)" }
+    ]
+
+    // Scales that divide this desktop's common resolutions into whole pixels.
+    // Hyprland rejects a fractional scale that does not, and the message it
+    // gives is not something to put in front of a user.
+    readonly property var scales: [1.0, 1.25, 1.5, 1.75, 2.0, 2.5, 3.0]
+
+    Process {
+        id: query
+        property int generation: 0
+        command: ["hyprctl", "-j", "monitors"]
+        stdout: StdioCollector {
+            onStreamFinished: root.parse(this.text, query.generation)
+        }
+        onExited: (exitCode, exitStatus) => {
+            if (exitCode !== 0)
+                root.lastError = "Could not read the connected displays.";
+            if (root.revertQueued && !applyRun.running && root.awaitingConfirmation)
+                root.performRevert();
+        }
+    }
+
+    Process {
+        id: applyRun
+        onExited: (exitCode, exitStatus) => {
+            if (!root.awaitingConfirmation)
+                return;
+            if (root.revertQueued) {
+                if (!query.running)
+                    root.performRevert();
+                return;
+            }
+            if (exitCode !== 0) {
+                root.revertWithMessage("The display rejected that change and Panama restored the previous setting.");
+                return;
+            }
+            verifyTimer.attempts = 0;
+            verifyTimer.ticks = 0;
+            verifyTimer.restart();
+        }
+    }
+
+    Process {
+        id: revertRun
+        onExited: (exitCode, exitStatus) => {
+            // Exit status is advisory only. Hyprland's Lua bridge can report
+            // success without applying a value, so exact readback decides.
+            root.revertVerificationActive = true;
+            revertVerifyTimer.attempts = 0;
+            revertVerifyTimer.ticks = 0;
+            revertVerifyTimer.restart();
+        }
+    }
+
+    Component.onCompleted: root.refresh()
+
+    function refresh(): bool {
+        if (!query.running) {
+            query.generation = root.operationGeneration;
+            query.running = true;
+            return true;
+        }
+        return false;
+    }
+
+    function parse(text: string, generation: int): void {
+        try {
+            const raw = JSON.parse(text);
+            root.monitors = raw.map(monitor => {
+                const modes = root.normaliseModes(monitor.availableModes ?? []);
+                const width = monitor.width ?? 0;
+                const height = monitor.height ?? 0;
+                const refreshRate = monitor.refreshRate ?? 0;
+                const current = modes
+                    .filter(mode => mode.width === width && mode.height === height)
+                    .sort((left, right) =>
+                        Math.abs(left.refresh - refreshRate) - Math.abs(right.refresh - refreshRate))[0];
+                return {
+                    name: monitor.name ?? "",
+                    description: monitor.description ?? monitor.model ?? "Display",
+                    width: width,
+                    height: height,
+                    refreshRate: refreshRate,
+                    mode: current?.mode ?? `${width}x${height}@${refreshRate}`,
+                    scale: monitor.scale ?? 1,
+                    transform: monitor.transform ?? 0,
+                    currentFormat: monitor.currentFormat ?? "",
+                    colorPreset: monitor.colorManagementPreset ?? "",
+                    vrr: monitor.vrr === true,
+                    modes: modes
+                };
+            });
+            if (root.awaitingConfirmation && root.pendingRequested
+                    && root.matchesRequest(root.monitorNamed(root.pendingOutput), root.pendingRequested)) {
+                root.pendingVerified = true;
+                verifyTimer.stop();
+                root.lastError = "";
+            } else if (root.revertVerificationActive
+                    && generation === root.revertGeneration
+                    && root.revertExpected
+                    && root.matchesRequest(root.monitorNamed(root.revertExpected.output), root.revertExpected)) {
+                revertVerifyTimer.stop();
+                root.revertVerificationActive = false;
+                root.revertGeneration = -1;
+                root.revertExpected = null;
+                if (root.revertReason === "")
+                    root.lastError = "";
+                else
+                    root.lastError = root.revertReason;
+                root.revertReason = "";
+            } else if (!root.awaitingConfirmation && !root.revertExpected && (
+                    root.lastError === "Could not read the connected displays."
+                    || root.lastError === "The display list could not be read.")) {
+                root.lastError = "";
+            }
+        } catch (error) {
+            root.lastError = "The display list could not be read.";
+        }
+    }
+
+    // "[email protected]" -> a sortable record. The compositor reports the same
+    // resolution at distinct rates such as 60.00 and 59.94. Those identities
+    // remain separate because confirmation and recovery must read back the
+    // exact mode the user chose, even when their rounded labels look similar.
+    function normaliseModes(raw: var): var {
+        const seen = {};
+        const out = [];
+        for (const entry of raw) {
+            const match = String(entry).match(/^(\d+)x(\d+)@([\d.]+)Hz$/);
+            if (!match)
+                continue;
+            const width = Number(match[1]);
+            const height = Number(match[2]);
+            const refreshText = match[3];
+            const refresh = Number(refreshText);
+            const roundedRefresh = Math.round(refresh);
+            const key = `${width}x${height}@${refreshText}`;
+            if (seen[key])
+                continue;
+            seen[key] = true;
+            out.push({
+                label: `${width} × ${height}`,
+                refreshLabel: Math.abs(refresh - roundedRefresh) < 0.005
+                    ? `${roundedRefresh} Hz`
+                    : `${refresh.toFixed(2)} Hz`,
+                mode: `${width}x${height}@${refreshText}`,
+                width: width,
+                height: height,
+                refresh: refresh
+            });
+        }
+        return out.sort((a, b) => (b.width * b.height) - (a.width * a.height) || b.refresh - a.refresh);
+    }
+
+    function monitorNamed(name: string): var {
+        return root.monitors.find(monitor => monitor.name === name) ?? null;
+    }
+
+    function modeParts(mode: string): var {
+        const match = String(mode).match(/^(\d+)x(\d+)@(\d+(?:\.\d+)?)$/);
+        if (!match)
+            return null;
+        return {
+            width: Number(match[1]),
+            height: Number(match[2]),
+            refresh: Number(match[3])
+        };
+    }
+
+    function isScaleClean(mode: string, scale: real): bool {
+        const parts = root.modeParts(mode);
+        if (!parts || root.scales.indexOf(scale) < 0 || !Number.isFinite(scale) || scale <= 0)
+            return false;
+        const logicalWidth = parts.width / scale;
+        const logicalHeight = parts.height / scale;
+        return Math.abs(logicalWidth - Math.round(logicalWidth)) < 0.0001
+            && Math.abs(logicalHeight - Math.round(logicalHeight)) < 0.0001;
+    }
+
+    function scalesForMode(mode: string): var {
+        return root.scales.filter(scale => root.isScaleClean(mode, scale));
+    }
+
+    function nearestCleanScale(mode: string, preferred: real): real {
+        const choices = root.scalesForMode(mode);
+        if (choices.length === 0)
+            return 1.0;
+        return choices.reduce((best, candidate) =>
+            Math.abs(candidate - preferred) < Math.abs(best - preferred) ? candidate : best,
+            choices[0]);
+    }
+
+    function matchesRequest(monitor: var, requested: var): bool {
+        if (!monitor || !requested || monitor.name !== requested.output)
+            return false;
+        const parts = root.modeParts(requested.mode);
+        return !!parts
+            && monitor.width === parts.width
+            && monitor.height === parts.height
+            && Math.abs(monitor.refreshRate - parts.refresh) < 0.01
+            && Math.abs(monitor.scale - requested.scale) < 0.001
+            && monitor.transform === requested.transform;
+    }
+
+    function modeIsCurrent(monitor: var, candidate: var): bool {
+        return !!monitor && !!candidate
+            && monitor.width === candidate.width
+            && monitor.height === candidate.height
+            && Math.abs(monitor.refreshRate - candidate.refresh) < 0.01;
+    }
+
+    // Applies immediately and starts the countdown. Nothing is stored yet: the
+    // settings file is only written by confirm().
+    function apply(output: string, mode: string, scale: real, transform: int): bool {
+        if (root.busy) {
+            root.lastError = "Wait for the current display operation to finish.";
+            return false;
+        }
+        if (root.awaitingConfirmation) {
+            root.lastError = "Finish the current display change first.";
+            return false;
+        }
+        const monitor = root.monitorNamed(output);
+        if (!monitor) {
+            root.lastError = "That display is not connected.";
+            return false;
+        }
+        if (!monitor.modes.some(candidate => candidate.mode === mode)) {
+            root.lastError = "That display does not offer that mode.";
+            return false;
+        }
+        if (!root.isScaleClean(mode, scale)) {
+            root.lastError = "That scale does not divide this resolution cleanly.";
+            return false;
+        }
+        if (!root.transforms.some(candidate => candidate.value === transform)) {
+            root.lastError = "That rotation is not one Panama offers.";
+            return false;
+        }
+
+        root.pendingPrevious = {
+            output: output,
+            mode: monitor.mode,
+            scale: monitor.scale,
+            transform: monitor.transform
+        };
+        root.operationGeneration++;
+        root.pendingRequested = {
+            output: output,
+            mode: mode,
+            scale: scale,
+            transform: transform
+        };
+        root.pendingOutput = output;
+        root.pendingVerified = false;
+        root.revertQueued = false;
+        root.secondsLeft = root.confirmSeconds;
+        root.lastError = "";
+        countdown.restart();
+
+        root.push(output, mode, scale, transform);
+        return true;
+    }
+
+    function push(output: string, mode: string, scale: real, transform: int): void {
+        // Values are validated above and the output name comes from the
+        // compositor's own list, so nothing user-authored reaches the payload.
+        applyRun.exec(["hyprctl", "eval",
+            `hl.monitor({ output = "${output}", mode = "${mode}", scale = ${scale}, transform = ${transform} })`]);
+    }
+
+    function confirm(): bool {
+        if (!root.canConfirm || !root.matchesRequest(
+                root.monitorNamed(root.pendingOutput), root.pendingRequested)) {
+            if (root.awaitingConfirmation)
+                root.lastError = "Wait for the display to finish applying before keeping it.";
+            return false;
+        }
+
+        const stored = DesktopPreferences.get("displays");
+        const next = Object.assign({}, (stored && typeof stored === "object") ? stored : {});
+        next[root.pendingOutput] = {
+            mode: root.pendingRequested.mode,
+            scale: root.pendingRequested.scale,
+            transform: root.pendingRequested.transform
+        };
+        if (!DesktopPreferences.set("displays", next)) {
+            root.lastError = "That display setting could not be saved. Revert it and try again.";
+            return false;
+        }
+
+        root.clearPending();
+        root.lastError = "";
+        return true;
+    }
+
+    function clearPending(): void {
+        countdown.stop();
+        verifyTimer.stop();
+        root.pendingOutput = "";
+        root.pendingPrevious = null;
+        root.pendingRequested = null;
+        root.pendingVerified = false;
+        root.revertQueued = false;
+        root.secondsLeft = 0;
+    }
+
+    function revert(): void {
+        root.revertWithMessage("");
+    }
+
+    function revertWithMessage(message: string): void {
+        if (!root.awaitingConfirmation)
+            return;
+        countdown.stop();
+        verifyTimer.stop();
+        root.pendingVerified = false;
+        root.revertReason = message;
+        if (message !== "")
+            root.lastError = message;
+        if (applyRun.running || query.running) {
+            root.revertQueued = true;
+            return;
+        }
+        root.performRevert();
+    }
+
+    function performRevert(): void {
+        const previous = root.pendingPrevious;
+        root.operationGeneration++;
+        root.revertGeneration = root.operationGeneration;
+        root.revertExpected = previous;
+        root.revertVerificationActive = false;
+        root.clearPending();
+        if (previous) {
+            revertRun.exec(["hyprctl", "eval",
+                `hl.monitor({ output = "${previous.output}", mode = "${previous.mode}", scale = ${previous.scale}, transform = ${previous.transform} })`]);
+        }
+    }
+
+    // Clears any stored override for an output so it returns to the value
+    // shipped in hypr/monitors.lua on the next start.
+    function forget(output: string): void {
+        const stored = DesktopPreferences.get("displays");
+        if (!stored || typeof stored !== "object" || stored[output] === undefined)
+            return;
+        const next = Object.assign({}, stored);
+        delete next[output];
+        DesktopPreferences.set("displays", next);
+    }
+
+    function isOverridden(output: string): bool {
+        const stored = DesktopPreferences.get("displays");
+        return !!(stored && typeof stored === "object" && stored[output] !== undefined);
+    }
+
+    Timer {
+        id: verifyTimer
+        property int attempts: 0
+        property int ticks: 0
+        interval: 120
+        repeat: true
+        onTriggered: {
+            ticks++;
+            if (ticks > 50) {
+                root.revertWithMessage("The display did not apply that setting, so Panama restored the previous one.");
+                return;
+            }
+            if (root.refresh())
+                attempts++;
+        }
+    }
+
+    Timer {
+        id: revertVerifyTimer
+        property int attempts: 0
+        property int ticks: 0
+        interval: 120
+        repeat: true
+        onTriggered: {
+            ticks++;
+            if (ticks > 50) {
+                stop();
+                root.revertVerificationActive = false;
+                root.revertGeneration = -1;
+                root.revertExpected = null;
+                root.revertReason = "";
+                root.lastError = "The previous display setting could not be verified. Open Displays and restore it manually.";
+                return;
+            }
+            if (root.refresh())
+                attempts++;
+        }
+    }
+
+    Timer {
+        id: countdown
+        interval: 1000
+        repeat: true
+        onTriggered: {
+            root.secondsLeft -= 1;
+            if (root.secondsLeft <= 0)
+                root.revert();
+        }
+    }
+}

config/dot/quickshell/services/SettingsBackup.qml

@@ -1,14 +1,15 @@
 pragma Singleton
 
-// Snapshots of the settings store.
+// Snapshots of Panama's durable settings stores.
 //
-// The whole desktop configuration is one JSON file, so a backup is a copy and a
+// DesktopPreferences and HomePreferences use separate files. The helper owns
-// restore is an overwrite. Worth exposing now that the settings app changes
+// the transactional filesystem boundary; this service owns settling the live
-// real things -- compositor geometry, idle timeouts, the dock -- because being
+// desktop after those files have changed underneath it.
-// able to return to a known-good state is what makes experimenting feel safe.
 //
-// Restoring rewrites the file underneath the running shell, so the store is
+// HomePreferences intentionally keeps its FileView in Quickshell's private
-// told to re-read afterwards rather than waiting for the next change.
+// state directory while snapshots use Panama's canonical state directory. This
+// service bridges them through HomePreferences' public mutation API, then soft
+// reloads once external consumers have settled.
 
 import Quickshell
 import Quickshell.Io
@@ -24,7 +25,31 @@ Singleton {
     property string lastError: ""
     property string lastAction: ""
 
+    // Narrow service boundaries keep restore sequencing explicit and make it
+    // possible to verify the real handler in an isolated shell without ever
+    // calling the daily-driver compositor or wallpaper services.
+    property var readHomeState: function() {
+        return {
+            initialized: HomePreferences.initialized,
+            favorites: HomePreferences.favorites
+        };
+    }
+    property var resetHome: function() { HomePreferences.resetHomeDefaults(); }
+    property var initializeHome: function(ids) { HomePreferences.initialize(ids); }
+    property var aliasHome: function(id, alias) { HomePreferences.setAlias(id, alias); }
+    property var reloadDesktop: function() { DesktopPreferences.reload(); }
+    property var applyCompositor: function() { SystemSettings.applyPersistedDisplayPolicy(); }
+    property var reloadKeybinds: function() { Keybinds.applyReload(); }
+    property var keybindsReloading: function() { return Keybinds.reloading; }
+    property var systemBusy: function() { return SystemSettings.busy; }
+    property var currentWallpaper: function() {
+        return String(DesktopPreferences.get("wallpaperPath") ?? "");
+    }
+    property var applyWallpaper: function(path) { Wallpaper.set(path); }
+    property var reloadShell: function() { Quickshell.reload(false); }
+
     readonly property bool busy: listQuery.running || actionRun.running
+        || applyRestoredState.running || settleReload.running
 
     Process {
         id: listQuery
@@ -34,7 +59,8 @@ Singleton {
                 try {
                     const parsed = JSON.parse(this.text);
                     root.snapshots = Array.isArray(parsed) ? parsed : [];
-                    root.lastError = "";
+                    if (root.lastError === "Could not read the list of snapshots.")
+                        root.lastError = "";
                 } catch (error) {
                     root.lastError = "Could not read the list of snapshots.";
                 }
@@ -45,6 +71,11 @@ Singleton {
     Process {
         id: actionRun
         property bool restoring: false
+        property string outputText: ""
+        stdout: StdioCollector {
+            onStreamFinished: actionRun.outputText = this.text
+        }
+        onStarted: actionRun.outputText = ""
         onExited: (exitCode, exitStatus) => {
             if (exitCode !== 0) {
                 root.lastError = actionRun.restoring
@@ -52,14 +83,52 @@ Singleton {
                     : "The settings could not be backed up.";
                 return;
             }
-            root.lastError = "";
             root.lastAction = actionRun.restoring ? "restored" : "saved";
-            if (actionRun.restoring)
+            if (actionRun.restoring) {
-                DesktopPreferences.reload();
+                const homeReloaded = root.handleRestoreOutput(actionRun.outputText);
+                root.lastError = homeReloaded
+                    ? ""
+                    : "Desktop settings were restored, but Home favourites could not be reloaded.";
+            } else
+                root.lastError = "";
             root.refresh();
         }
     }
 
+    Timer {
+        id: applyRestoredState
+        interval: 80
+        repeat: false
+        onTriggered: {
+            // DesktopPreferences.reload() invalidates reactive shell bindings.
+            // These services also own state outside QML and need an explicit
+            // replay: compositor options, Lua-generated binds, and hyprpaper.
+            root.applyCompositor();
+            root.reloadKeybinds();
+            root.applyWallpaper(root.currentWallpaper());
+
+            settleReload.attempts = 0;
+            settleReload.restart();
+        }
+    }
+
+    Timer {
+        id: settleReload
+        property int attempts: 0
+        interval: 100
+        repeat: true
+        onTriggered: {
+            attempts++;
+            // Let the current instances finish their external writes before a
+            // soft reload replaces them. The cap keeps a failed external tool
+            // from leaving restored Home state stale indefinitely.
+            if ((!root.keybindsReloading() && !root.systemBusy()) || attempts >= 30) {
+                stop();
+                root.reloadShell();
+            }
+        }
+    }
+
     Component.onCompleted: root.refresh()
 
     function refresh(): void {
@@ -71,7 +140,81 @@ Singleton {
         if (actionRun.running)
             return;
         actionRun.restoring = false;
-        actionRun.exec([root.helperPath, "save"]);
+        actionRun.exec([root.helperPath, "save", root.serialiseHomeState()]);
+    }
+
+    function serialiseHomeState(): string {
+        const current = root.readHomeState();
+        const favorites = [];
+        for (const favorite of current.favorites ?? []) {
+            favorites.push({
+                id: String(favorite.id ?? ""),
+                alias: String(favorite.alias ?? "")
+            });
+        }
+        return JSON.stringify({
+            initialized: current.initialized === true,
+            favorites: favorites
+        });
+    }
+
+    function handleRestoreOutput(text: string): bool {
+        if (!root.reloadHomeState(text))
+            return false;
+        root.reloadDesktop();
+        applyRestoredState.restart();
+        return true;
+    }
+
+    // Restore output carries the canonical Home state. Reconstructing through
+    // these methods keeps validation and persistence inside HomePreferences;
+    // this service never mutates its aliases or private FileView directly.
+    function reloadHomeState(text: string): bool {
+        try {
+            const result = JSON.parse(text);
+            const restored = result?.home;
+            if (!restored || restored.preserve === true)
+                return true;
+
+            if (restored.present !== true)
+                return restored.present === false
+                    ? root.resetHomeState()
+                    : false;
+
+            const data = restored.data;
+            if (!data || typeof data.initialized !== "boolean" || !Array.isArray(data.favorites))
+                return false;
+            const ids = [];
+            const aliases = [];
+            const seen = {};
+            for (const favorite of data.favorites) {
+                const id = favorite?.id;
+                const alias = favorite?.alias;
+                if (typeof id !== "string" || !/^light\.[a-z0-9_]+$/.test(id)
+                        || typeof alias !== "string" || seen[id])
+                    return false;
+                seen[id] = true;
+                ids.push(id);
+                aliases.push(alias);
+            }
+            if (!data.initialized && ids.length > 0)
+                return false;
+
+            root.resetHome();
+            if (!data.initialized)
+                return true;
+            root.initializeHome(ids);
+            for (let index = 0; index < ids.length; index++)
+                root.aliasHome(ids[index], aliases[index]);
+            return true;
+        } catch (error) {
+            return false;
+        }
+    }
+
+    function resetHomeState(): bool {
+        root.resetHome();
+        return true;
     }
 
     // The name is matched against the snapshot list rather than trusted, so no

config/dot/quickshell/settings-backup-harness.qml

@@ -0,0 +1,76 @@
+// Isolated behavioral harness for SettingsBackup's live restore handoff.
+// Every external consumer is replaced before restore output is exercised, so
+// this file never writes the real compositor, wallpaper, keymap, or shell.
+import Quickshell
+import Quickshell.Io
+import QtQuick
+
+import qs.services
+
+ShellRoot {
+    id: root
+
+    property var calls: []
+    property bool homeInitialized: false
+    property var homeFavorites: []
+
+    function record(name: string): void {
+        const next = root.calls.slice();
+        next.push(name);
+        root.calls = next;
+    }
+
+    Component.onCompleted: {
+        SettingsBackup.readHomeState = function() {
+            return {
+                initialized: root.homeInitialized,
+                favorites: root.homeFavorites
+            };
+        };
+        SettingsBackup.resetHome = function() {
+            root.record("home.reset");
+            root.homeInitialized = false;
+            root.homeFavorites = [];
+        };
+        SettingsBackup.initializeHome = function(ids) {
+            root.record("home.initialize:" + ids.join(","));
+            root.homeInitialized = true;
+            root.homeFavorites = ids.map(id => ({ id: id, alias: "" }));
+        };
+        SettingsBackup.aliasHome = function(id, alias) {
+            root.record("home.alias:" + id + "=" + alias);
+            root.homeFavorites = root.homeFavorites.map(favorite =>
+                favorite.id === id ? { id: id, alias: alias } : favorite);
+        };
+        SettingsBackup.reloadDesktop = function() { root.record("desktop.reload"); };
+        SettingsBackup.applyCompositor = function() { root.record("system.apply"); };
+        SettingsBackup.reloadKeybinds = function() { root.record("keybinds.reload"); };
+        SettingsBackup.keybindsReloading = function() { return false; };
+        SettingsBackup.systemBusy = function() { return false; };
+        SettingsBackup.currentWallpaper = function() { return "/tmp/restored-wallpaper.jpg"; };
+        SettingsBackup.applyWallpaper = function(path) { root.record("wallpaper.set:" + path); };
+        SettingsBackup.reloadShell = function() { root.record("shell.reload"); };
+    }
+
+    IpcHandler {
+        target: "settings-backup-behavior"
+
+        function reset(): void {
+            root.calls = [];
+            root.homeInitialized = false;
+            root.homeFavorites = [];
+        }
+
+        function apply(output: string): bool {
+            return SettingsBackup.handleRestoreOutput(output);
+        }
+
+        function status(): string {
+            return JSON.stringify({
+                calls: root.calls,
+                initialized: root.homeInitialized,
+                favorites: root.homeFavorites
+            });
+        }
+    }
+}

tests/quickshell/displays-contract.sh

@@ -0,0 +1,300 @@
+#!/usr/bin/env bash
+
+# Display configuration.
+#
+# This is the only setting in Panama that can leave the user unable to SEE the
+# screen well enough to undo it: a mode the panel cannot show, or a scale that
+# makes everything unreadable, is not recoverable through the UI that caused it.
+#
+# So the property under test is not "can it change the resolution" but "does an
+# unconfirmed change always come back". A regression here is not a broken
+# feature, it is a user staring at a blank monitor.
+#
+#   * an unconfirmed change reverts on its own, and stores nothing
+#   * a confirmed change is what writes to the settings store
+#   * a mode, scale, rotation, or output the compositor did not offer is refused
+#     before anything is applied
+#
+# The compositor is the live one -- there is no way to test this otherwise --
+# but preferences are isolated, and every path restores the display it started
+# from.
+
+set -euo pipefail
+
+repo_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+harness="$repo_dir/config/dot/quickshell/displays-harness.qml"
+service="$repo_dir/config/dot/quickshell/services/Displays.qml"
+page="$repo_dir/config/dot/quickshell/modules/settings/DisplaysPage.qml"
+settings_page="$repo_dir/config/dot/quickshell/modules/settings/SettingsPage.qml"
+monitors_lua="$repo_dir/config/dot/hypr/monitors.lua"
+
+fail() {
+    printf 'displays contract: %s\n' "$1" >&2
+    exit 1
+}
+
+# Keep is unavailable until compositor readback exactly matches the request.
+for contract in \
+    'property var pendingRequested:' \
+    'property var revertExpected:' \
+    'property bool revertVerificationActive:' \
+    'property int revertGeneration:' \
+    'readonly property bool canConfirm:' \
+    'function matchesRequest(' \
+    'function scalesForMode(' \
+    'function isScaleClean('; do
+    rg -Fq "$contract" "$service" || fail "display service contract is missing: $contract"
+done
+rg -Fq 'enabled: Displays.canConfirm' "$page" \
+    || fail 'Keep is enabled before the display change is verified'
+rg -Fq 'options: Displays.scalesForMode(' "$page" \
+    || fail 'scale choices are not filtered for the active resolution'
+rg -Fq 'property string selectedOutput:' "$page" \
+    || fail 'connected outputs cannot be selected'
+rg -Fq 'options: Displays.monitors.map(' "$page" \
+    || fail 'the output selector is not populated from connected displays'
+rg -Fq 'id: revertVerifyTimer' "$service" \
+    || fail 'automatic restoration has no bounded readback verification'
+rg -Fq 'if (root.busy)' "$service" \
+    || fail 'the display service accepts a new apply while another operation is busy'
+
+# Stored JSON is untyped at field level, so the Lua startup consumer is the
+# final validation boundary and must support every named output it accepts.
+for contract in 'valid_mode' 'valid_scale' 'valid_transform' 'pairs(displays)'; do
+    rg -Fq "$contract" "$monitors_lua" || fail "monitor startup validation is missing: $contract"
+done
+
+# SettingsPage headers are genuinely pinned outside its scrolling surface.
+python3 - "$settings_page" <<'PY' || fail 'SettingsPage header is not pinned outside the Flickable'
+import sys
+text = open(sys.argv[1], encoding="utf-8").read()
+loader = text.find("id: pinnedHeader")
+flickable = text.find("id: pageScroll")
+if loader < 0 or flickable < 0 or loader > flickable:
+    raise SystemExit(1)
+PY
+
+MONITORS_LUA="$monitors_lua" lua - <<'LUA' || fail 'monitor startup accepted invalid persisted geometry or ignored a named output'
+package.preload["prefs"] = function()
+    return {
+        get = function()
+            return {
+                ["DP-2"] = { mode = "not-a-mode", scale = -1, transform = 99 },
+                ["HDMI-A-1"] = { mode = "1920x1080@60", scale = 1.5, transform = 1 },
+                ["BAD OUTPUT"] = { mode = "1920x1080@60", scale = 1, transform = 0 },
+            }
+        end,
+    }
+end
+
+local calls = {}
+hl = { monitor = function(value) table.insert(calls, value) end }
+assert(loadfile(os.getenv("MONITORS_LUA")))()
+
+local by_output = {}
+for _, value in ipairs(calls) do by_output[value.output] = value end
+assert(by_output["DP-2"].mode == "4500x3000@60")
+assert(by_output["DP-2"].scale == 1.5)
+assert(by_output["DP-2"].transform == 0)
+assert(by_output["HDMI-A-1"].mode == "1920x1080@60")
+assert(by_output["HDMI-A-1"].scale == 1.5)
+assert(by_output["HDMI-A-1"].transform == 1)
+assert(by_output["BAD OUTPUT"] == nil)
+assert(by_output[""] ~= nil)
+LUA
+
+if [[ "${PANAMA_DISPLAYS_STATIC_ONLY:-0}" == "1" ]]; then
+    printf 'displays contract: PASS (static)\n'
+    exit 0
+fi
+
+config_home="$(mktemp -d /tmp/panama-displays-config.XXXXXX)"
+
+run() { XDG_CONFIG_HOME="$config_home" qs -p "$harness" "$@"; }
+status() { run ipc call displays-test status; }
+
+original_mode=""
+original_scale=""
+original_transform=""
+original_width=""
+original_height=""
+original_refresh=""
+monitor_name=""
+
+monitor_state() {
+    hyprctl -j monitors | jq -c --arg output "$monitor_name" '.[] | select(.name == $output)'
+}
+
+display_is_restored() {
+    local current
+    current="$(monitor_state)"
+    [[ -n "$current" ]] || return 1
+    jq -e \
+        --argjson width "$original_width" \
+        --argjson height "$original_height" \
+        --argjson refresh "$original_refresh" \
+        --argjson scale "$original_scale" \
+        --argjson transform "$original_transform" \
+        '.width == $width and .height == $height
+            and ((.refreshRate - $refresh) | fabs) < 0.01
+            and ((.scale - $scale) | fabs) < 0.001
+            and .transform == $transform' <<<"$current" >/dev/null
+}
+
+restore_display() {
+    [[ -n "$original_mode" ]] || return 0
+    hyprctl eval "hl.monitor({ output = \"$monitor_name\", mode = \"$original_mode\", scale = $original_scale, transform = $original_transform })" >/dev/null \
+        || return 1
+    for _ in $(seq 1 50); do
+        display_is_restored && return 0
+        sleep 0.2
+    done
+    return 1
+}
+
+stop_harness() {
+    # Kill by PID, never `pkill -f displays-harness`: that pattern also matches
+    # any shell whose command line contains this script's text, which includes
+    # the invoking shell itself.
+    [[ -n "${harness_pid:-}" ]] && kill "$harness_pid" >/dev/null 2>&1 || true
+    rm -rf "$config_home"
+}
+
+cleanup() {
+    local status=$?
+    trap - EXIT
+    if ! restore_display; then
+        printf 'displays contract: FAILED to restore %s to %s scale %s transform %s\n' \
+            "$monitor_name" "$original_mode" "$original_scale" "$original_transform" >&2
+        status=1
+    fi
+    stop_harness
+    exit "$status"
+}
+trap cleanup EXIT
+
+XDG_CONFIG_HOME="$config_home" qs -p "$harness" --daemonize >/dev/null
+harness_pid=""
+for _ in $(seq 1 40); do
+    run ipc show 2>/dev/null | rg -q '^target displays-test$' && break
+    sleep 0.1
+done
+run ipc show 2>/dev/null | rg -q '^target displays-test$' || fail 'test IPC target did not start'
+harness_pid="$(run list | awk '/Process ID:/ { print $3; exit }')"
+
+refresh_fixture="$(run ipc call displays-test refreshIdentityFixture)"
+jq -e '
+    .count == 2
+    and .modes == ["[email protected]", "[email protected]"]
+    and .selected == ["[email protected]"]
+' <<<"$refresh_fixture" >/dev/null \
+    || fail "59.94 Hz and 60.00 Hz lost their distinct selection identity: $refresh_fixture"
+
+for _ in $(seq 1 50); do
+    [[ "$(status | jq -r .count)" != "0" ]] && break
+    sleep 0.1
+done
+
+state="$(status)"
+monitor_name="$(jq -r .name <<<"$state")"
+[[ -n "$monitor_name" ]] || fail "no display was detected: $state"
+original_mode="$(jq -r .mode <<<"$state")"
+original_width="$(jq -r .width <<<"$state")"
+original_height="$(jq -r .height <<<"$state")"
+original_refresh="$(jq -r .refresh <<<"$state")"
+original_scale="$(jq -r .scale <<<"$state")"
+original_transform="$(jq -r .transform <<<"$state")"
+
+[[ "$(jq -r .modes <<<"$state")" -gt 0 ]] || fail 'the display reported no usable modes'
+
+# ── Anything the compositor did not offer is refused before applying ─────────
+while IFS= read -r kind; do
+    [[ "$(run ipc call displays-test applyBad "$kind")" == "false" ]] \
+        || fail "an invalid $kind was accepted"
+    [[ "$(status | jq -r .awaiting)" == "false" ]] \
+        || fail "an invalid $kind left a change pending"
+done <<'KINDS'
+mode
+scale
+transform
+output
+dirtyScale
+KINDS
+
+# The display must not have moved for any of those.
+now="$(status)"
+[[ "$(jq -r .scale <<<"$now")" == "$original_scale" ]] || fail 'a refused change still altered the scale'
+
+# An immediate Revert may race both the apply process and its first readback.
+# It must queue until both are clear, then verify the original generation.
+target_scale=$(awk -v s="$original_scale" 'BEGIN { print (s == 1.25) ? 1.5 : 1.25 }')
+[[ "$(run ipc call displays-test applyScale "$target_scale")" == "true" ]] \
+    || fail 'the immediate-revert fixture could not apply'
+run ipc call displays-test revertChange >/dev/null
+immediate_reverted=false
+for _ in $(seq 1 60); do
+    if display_is_restored && [[ "$(status | jq -r .awaiting)" == "false" ]]; then
+        immediate_reverted=true
+        break
+    fi
+    sleep 0.2
+done
+[[ "$immediate_reverted" == true ]] \
+    || fail 'an immediate Revert raced the apply/readback and did not restore the display'
+
+# ── An unconfirmed change reverts on its own and stores nothing ──────────────
+[[ "$(run ipc call displays-test applyScale "$target_scale")" == "true" ]] \
+    || fail 'a valid scale change was refused'
+
+applied=false
+for _ in $(seq 1 30); do
+    [[ "$(monitor_state | jq -r '.scale')" == "$target_scale" ]] && { applied=true; break; }
+    sleep 0.2
+done
+[[ "$applied" == true ]] || fail 'the scale change never reached the compositor'
+[[ "$(status | jq -r .awaiting)" == "true" ]] || fail 'an applied change is not awaiting confirmation'
+[[ "$(status | jq -r .canConfirm)" == "true" ]] || fail 'an applied change was never verified by compositor readback'
+
+# Wait out the countdown. This is the whole point of the contract.
+reverted=false
+for _ in $(seq 1 120); do
+    if [[ "$(monitor_state | jq -r '.scale')" == "$original_scale" ]]; then
+        reverted=true
+        break
+    fi
+    sleep 0.5
+done
+[[ "$reverted" == true ]] || fail 'an unconfirmed change did NOT revert -- this would strand a user on an unreadable display'
+[[ "$(status | jq -r .awaiting)" == "false" ]] || fail 'the pending state survived the revert'
+[[ "$(status | jq -r .overridden)" == "false" ]] || fail 'an unconfirmed change was written to the settings store'
+
+# ── A confirmed change is what writes ────────────────────────────────────────
+run ipc call displays-test applyScale "$target_scale" >/dev/null
+[[ "$(run ipc call displays-test confirmChange)" == "false" ]] \
+    || fail 'Keep accepted a display change before compositor readback'
+verified=false
+for _ in $(seq 1 30); do
+    [[ "$(status | jq -r .canConfirm)" == "true" ]] && { verified=true; break; }
+    sleep 0.2
+done
+[[ "$verified" == true ]] || fail 'the confirmed change never became safe to keep'
+[[ "$(run ipc call displays-test confirmChange)" == "true" ]] \
+    || fail 'Keep refused a verified display change'
+sleep 0.6
+[[ "$(status | jq -r .awaiting)" == "false" ]] || fail 'confirming did not clear the pending state'
+[[ "$(status | jq -r .overridden)" == "true" ]] || fail 'confirming did not store the change'
+
+store="$config_home/panama/settings.json"
+jq -e --arg m "$monitor_name" '.displays[$m].scale != null' "$store" >/dev/null \
+    || fail 'the confirmed change is not in the settings store'
+
+# ── Forgetting clears it ─────────────────────────────────────────────────────
+run ipc call displays-test forget >/dev/null
+sleep 0.6
+[[ "$(status | jq -r .overridden)" == "false" ]] || fail 'forget did not clear the stored display setting'
+
+restore_display || fail 'the final cleanup could not restore and verify the original display'
+original_mode=""
+stop_harness
+trap - EXIT
+printf 'displays contract: PASS\n'

tests/quickshell/settings-backup-contract.sh

@@ -22,10 +22,26 @@ cleanup() { rm -rf "$work"; }
 trap cleanup EXIT
 
 settings="$work/config/panama/settings.json"
+home="$work/state/panama/panama-home.json"
 backups="$work/state/panama/backups"
+transaction_dir="$work/state/panama/transactions/settings-restore"
 mkdir -p "$(dirname "$settings")"
 
 run() { XDG_CONFIG_HOME="$work/config" XDG_STATE_HOME="$work/state" "$helper" "$@"; }
+run_with() { XDG_CONFIG_HOME="$work/config" XDG_STATE_HOME="$work/state" env "$@"; }
+
+assert_transaction_clean() {
+    if [[ -d "$transaction_dir" ]] && find "$transaction_dir" -mindepth 1 -print -quit | rg -q .; then
+        fail 'restore left staged, rollback, or journal files behind'
+    fi
+    if find "$work" -type f \( \
+            -name '.settings-restore.*' -o -name '.home-restore.*' \
+            -o -name '*rollback*' -o -name '.journal.json.*' \
+            -o -name '.settings.json.*' -o -name '.panama-home.json.*' \
+        \) -print -quit | rg -q .; then
+        fail 'restore left a temporary target or journal file behind'
+    fi
+}
 
 # ── Nothing to back up ───────────────────────────────────────────────────────
 run save >/dev/null 2>&1 && fail 'backing up a missing settings file reported success'
@@ -33,15 +49,96 @@ run save >/dev/null 2>&1 && fail 'backing up a missing settings file reported su
 
 # ── A snapshot round-trips ───────────────────────────────────────────────────
 printf '{"gapsOut":24,"windowRounding":6}' >"$settings"
+mkdir -p "$(dirname "$home")"
+printf '{"initialized":true,"favorites":[{"id":"light.desk","alias":"Desk"}]}' >"$home"
 run save >/dev/null || fail 'save failed on a valid settings file'
 name="$(run list | jq -r '.[0].name')"
 [[ "$name" =~ ^settings-[0-9]{8}-[0-9]{9}\.json$ ]] || fail "unexpected snapshot name: $name"
 [[ "$(run list | jq -r '.[0].keys')" == "2" ]] || fail 'snapshot key count is wrong'
 
 printf '{"gapsOut":99}' >"$settings"
-run restore "$name" >/dev/null || fail 'restore failed'
+printf '{"initialized":false,"favorites":[]}' >"$home"
+restore_result="$(run restore "$name")" || fail 'restore failed'
 [[ "$(jq -r .gapsOut "$settings")" == "24" ]] || fail 'restore did not bring back the snapshot contents'
 [[ "$(jq -r .windowRounding "$settings")" == "6" ]] || fail 'restore lost a key'
+[[ "$(jq -r '.favorites[0].id' "$home")" == "light.desk" ]] || fail 'restore did not bring back Home favourites'
+[[ "$(jq -r '.favorites[0].alias' "$home")" == "Desk" ]] || fail 'restore lost a Home alias'
+jq -e '.home.present == true and .home.data.favorites[0].id == "light.desk"' <<<"$restore_result" >/dev/null \
+    || fail 'restore did not return Home state for the live service to reload'
+
+# ── Absence is part of a snapshot ───────────────────────────────────────────
+rm -f "$home"
+printf '{"gapsOut":30}' >"$settings"
+run save >/dev/null || fail 'save failed when Home state was absent'
+absent_name="$(run list | jq -r '.[0].name')"
+printf '{"initialized":true,"favorites":[{"id":"light.living_room","alias":"Living room"}]}' >"$home"
+absent_result="$(run restore "$absent_name")" || fail 'restore failed for a snapshot without Home state'
+[[ ! -e "$home" ]] || fail 'restore did not preserve the snapshot’s absent Home state'
+jq -e '.home.present == false and (.home | has("data") | not)' <<<"$absent_result" >/dev/null \
+    || fail 'restore did not return absent Home state for the live service to reload'
+
+# Desktop absence is symmetric: a Home-only snapshot removes a desktop file
+# created later and restores the Home store.
+rm -f "$settings"
+printf '{"initialized":true,"favorites":[{"id":"light.porch","alias":"Porch"}]}' >"$home"
+run save >/dev/null || fail 'save failed when desktop settings were absent'
+desktop_absent_name="$(run list | jq -r '.[0].name')"
+printf '{"gapsOut":47}' >"$settings"
+printf '{"initialized":false,"favorites":[]}' >"$home"
+run restore "$desktop_absent_name" >/dev/null || fail 'Home-only snapshot restore failed'
+[[ ! -e "$settings" ]] || fail 'restore did not preserve the snapshot’s absent desktop state'
+[[ "$(jq -r '.favorites[0].id' "$home")" == "light.porch" ]] \
+    || fail 'Home-only snapshot did not restore Home state'
+assert_transaction_clean
+
+printf '{"gapsOut":17}' >"$settings"
+
+# A legacy settings-only snapshot predates presence metadata. Its safest
+# interpretation is to restore desktop settings without deleting current Home
+# state that the old format knew nothing about.
+legacy="settings-20000101-010203004.json"
+printf '{"gapsOut":17}' >"$backups/$legacy"
+printf '{"initialized":true,"favorites":[{"id":"light.office","alias":"Office"}]}' >"$home"
+run restore "$legacy" >/dev/null || fail 'legacy snapshot restore failed'
+[[ "$(jq -r .gapsOut "$settings")" == "17" ]] || fail 'legacy snapshot did not restore desktop settings'
+[[ "$(jq -r '.favorites[0].id' "$home")" == "light.office" ]] || fail 'legacy snapshot destroyed Home state it did not describe'
+
+# `version` is a valid unknown desktop preference. It is only an envelope when
+# the complete v2 shape is present.
+legacy_version="settings-20000101-010203005.json"
+printf '{"version":77,"gapsOut":19}' >"$backups/$legacy_version"
+run restore "$legacy_version" >/dev/null || fail 'a legacy snapshot with an unknown version key was rejected'
+[[ "$(jq -r '.version' "$settings")" == "77" ]] || fail 'legacy version key was not restored as desktop data'
+[[ "$(jq -r '.favorites[0].id' "$home")" == "light.office" ]] || fail 'legacy version key changed Home state'
+
+# ── A durable journal recovers a process/power-loss split ────────────────────
+printf '{"gapsOut":28,"windowRounding":12}' >"$settings"
+printf '{"initialized":true,"favorites":[{"id":"light.desk","alias":"Snapshot"}]}' >"$home"
+run save >/dev/null || fail 'could not create crash-recovery snapshot'
+crash_name="$(run list | jq -r '.[0].name')"
+
+printf '{"gapsOut":91,"windowRounding":3}' >"$settings"
+printf '{"initialized":true,"favorites":[{"id":"light.office","alias":"Before crash"}]}' >"$home"
+run_with PANAMA_SETTINGS_BACKUP_TEST_CRASH=after-desktop "$helper" restore "$crash_name" >/dev/null 2>&1 \
+    && fail 'crash injection completed restore instead of terminating after the first replacement'
+[[ "$(jq -r '.gapsOut' "$settings")" == "28" ]] || fail 'crash did not occur after desktop replacement'
+[[ "$(jq -r '.favorites[0].alias' "$home")" == "Before crash" ]] || fail 'crash unexpectedly replaced Home state'
+[[ -f "$transaction_dir/journal.json" ]] || fail 'crash left no durable recovery journal'
+
+# Every entry point must recover before doing its own work. `list` is the least
+# invasive proof and must put both stores back to the pre-restore generation.
+run list >/dev/null || fail 'next invocation could not recover the interrupted restore'
+[[ "$(jq -r '.gapsOut' "$settings")" == "91" ]] || fail 'recovery did not roll desktop settings back'
+[[ "$(jq -r '.favorites[0].alias' "$home")" == "Before crash" ]] || fail 'recovery did not keep Home state in the same generation'
+assert_transaction_clean
+
+# Cleanup is installed before staging. A deterministic pre-journal failure
+# must leave both destinations untouched and no hidden artifacts behind.
+run_with PANAMA_SETTINGS_BACKUP_TEST_FAIL=after-desktop-stage "$helper" restore "$crash_name" >/dev/null 2>&1 \
+    && fail 'staging failure injection unexpectedly restored the snapshot'
+[[ "$(jq -r '.gapsOut' "$settings")" == "91" ]] || fail 'staging failure changed desktop settings'
+[[ "$(jq -r '.favorites[0].alias' "$home")" == "Before crash" ]] || fail 'staging failure changed Home state'
+assert_transaction_clean
 
 # ── Restoring snapshots what it replaced, so it is undoable ──────────────────
 count="$(run list | jq 'length')"
@@ -52,12 +149,44 @@ bad="settings-19990101-000000000.json"
 mkdir -p "$backups"
 printf '{ truncated' >"$backups/$bad"
 run restore "$bad" >/dev/null 2>&1 && fail 'a corrupt snapshot was restored'
-[[ "$(jq -r .gapsOut "$settings")" == "24" ]] || fail 'a refused restore still damaged the settings file'
+[[ "$(jq -r .gapsOut "$settings")" == "91" ]] || fail 'a refused restore still damaged the settings file'
+
+invalid_home="settings-19990101-000000001.json"
+jq -n '{
+    version: 2,
+    desktop: {present: true, data: {gapsOut: 88}},
+    home: {present: true, data: {
+        initialized: true,
+        favorites: [
+            {id: "light.desk", alias: "Desk"},
+            {id: "light.desk", alias: "Duplicate"}
+        ]
+    }}
+}' >"$backups/$invalid_home"
+run restore "$invalid_home" >/dev/null 2>&1 && fail 'a snapshot with duplicate Home favourites was restored'
+[[ "$(jq -r .gapsOut "$settings")" == "91" ]] || fail 'an invalid Home snapshot still damaged desktop settings'
+
+printf '{ truncated' >"$home"
+run save >/dev/null 2>&1 && fail 'a corrupt Home state file was backed up'
+printf '{"initialized":true,"favorites":[]}' >"$home"
+
+# ── The live service can sync its private Home state before save ─────────────
+rm -f "$home"
+printf '{"gapsOut":21}' >"$settings"
+live_home='{"initialized":true,"favorites":[{"id":"light.studio","alias":"Studio"}]}'
+run save "$live_home" >/dev/null || fail 'save rejected valid live Home state'
+live_name="$(run list | jq -r '.[0].name')"
+jq -e '.home.present == true and .home.data.favorites[0].alias == "Studio"' \
+    "$backups/$live_name" >/dev/null \
+    || fail 'live Home state was not written to the canonical snapshot'
 
 # ── A snapshot cannot name a path outside the backup directory ───────────────
 printf '{"pwned":true}' >"$work/outside.json"
 run restore "../../outside.json" >/dev/null 2>&1 && fail 'a traversing snapshot name was accepted'
 run restore "/etc/passwd" >/dev/null 2>&1 && fail 'an absolute snapshot path was accepted'
+link_name="settings-20000101-000000001.json"
+ln -s "$work/outside.json" "$backups/$link_name"
+run restore "$link_name" >/dev/null 2>&1 && fail 'a snapshot symlink escaping the backup directory was accepted'
 jq -e 'has("pwned") | not' "$settings" >/dev/null || fail 'a file outside the backup directory was restored'
 
 # ── A snapshot that is not listed is refused ─────────────────────────────────

tests/quickshell/settings-backup-live-contract.sh

@@ -0,0 +1,132 @@
+#!/usr/bin/env bash
+
+# Behavioral coverage for the QML handoff after the helper commits a restore.
+# The harness has a unique shell identity, isolated XDG roots, and fake external
+# consumers. It records the real SettingsBackup call order without touching the
+# daily-driver shell, compositor, keymap, or wallpaper.
+
+set -euo pipefail
+
+repo_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+service="$repo_dir/config/dot/quickshell/services/SettingsBackup.qml"
+harness="$repo_dir/config/dot/quickshell/settings-backup-harness.qml"
+work="$(mktemp -d /tmp/panama-settings-backup-live.XXXXXX)"
+
+fail() {
+    printf 'settings backup live contract: %s\n' "$1" >&2
+    exit 1
+}
+
+qs_test() {
+    XDG_CONFIG_HOME="$work/config" XDG_STATE_HOME="$work/state" qs -p "$harness" "$@"
+}
+
+cleanup() {
+    qs_test kill >/dev/null 2>&1 || true
+    rm -rf "$work"
+}
+trap cleanup EXIT
+
+# The production command boundary must remain argv-only.
+rg -Fq 'actionRun.exec([root.helperPath, "save", root.serialiseHomeState()]);' "$service" \
+    || fail 'save does not pass live Home state as one argument'
+rg -Fq 'actionRun.exec([root.helperPath, "restore", name]);' "$service" \
+    || fail 'restore is not executed through an argument array'
+if rg -q 'bash.*-c|sh.*-c' "$service"; then
+    fail 'the restore service constructs a shell command'
+fi
+
+# The harness replaces these seams, while these mappings prove the production
+# defaults still delegate to Panama's existing public service APIs.
+for mapping in \
+    'HomePreferences.resetHomeDefaults();' \
+    'HomePreferences.initialize(ids);' \
+    'HomePreferences.setAlias(id, alias);' \
+    'DesktopPreferences.reload();' \
+    'SystemSettings.applyPersistedDisplayPolicy();' \
+    'Keybinds.applyReload();' \
+    'Wallpaper.set(path);' \
+    'Quickshell.reload(false);'; do
+    rg -Fq "$mapping" "$service" || fail "production restore seam is missing: $mapping"
+done
+
+qs_test --daemonize >"$work/quickshell.log" 2>&1
+ready=false
+for _ in $(seq 1 60); do
+    if qs_test ipc show 2>/dev/null | rg -q '^target settings-backup-behavior$'; then
+        ready=true
+        break
+    fi
+    sleep 0.1
+done
+if [[ "$ready" != true ]]; then
+    sed -n '1,200p' "$work/quickshell.log" >&2
+    fail 'isolated SettingsBackup harness did not start'
+fi
+
+qs_test ipc call settings-backup-behavior reset >/dev/null
+payload='{"restored":"settings-20260818-010203004.json","home":{"present":true,"data":{"initialized":true,"favorites":[{"id":"light.desk","alias":"Desk"},{"id":"light.office","alias":"Office"}]}}}'
+[[ "$(qs_test ipc call settings-backup-behavior apply "$payload")" == "true" ]] \
+    || fail 'valid restore output was rejected'
+
+status=""
+for _ in $(seq 1 50); do
+    status="$(qs_test ipc call settings-backup-behavior status)"
+    jq -e '.calls[-1] == "shell.reload"' <<<"$status" >/dev/null 2>&1 && break
+    sleep 0.1
+done
+jq -e '
+    .calls == [
+        "home.reset",
+        "home.initialize:light.desk,light.office",
+        "home.alias:light.desk=Desk",
+        "home.alias:light.office=Office",
+        "desktop.reload",
+        "system.apply",
+        "keybinds.reload",
+        "wallpaper.set:/tmp/restored-wallpaper.jpg",
+        "shell.reload"
+    ]
+    and .initialized == true
+    and .favorites == [
+        {"id":"light.desk","alias":"Desk"},
+        {"id":"light.office","alias":"Office"}
+    ]
+' <<<"$status" >/dev/null || fail "restore handoff order/state was wrong: $status"
+
+# Invalid output is rejected before Home state or external consumers change.
+qs_test ipc call settings-backup-behavior reset >/dev/null
+invalid='{"home":{"present":true,"data":{"initialized":true,"favorites":[{"id":"light.desk","alias":"One"},{"id":"light.desk","alias":"Two"}]}}}'
+[[ "$(qs_test ipc call settings-backup-behavior apply "$invalid")" == "false" ]] \
+    || fail 'duplicate Home state was accepted'
+status="$(qs_test ipc call settings-backup-behavior status)"
+jq -e '.calls == [] and .initialized == false and .favorites == []' <<<"$status" >/dev/null \
+    || fail 'invalid restore output caused partial live mutations'
+
+# An absent Home generation uses the same ordered external handoff but leaves
+# the live Home service reset rather than manufacturing an initialized store.
+qs_test ipc call settings-backup-behavior reset >/dev/null
+absent='{"restored":"settings-20260818-010203005.json","home":{"present":false}}'
+[[ "$(qs_test ipc call settings-backup-behavior apply "$absent")" == "true" ]] \
+    || fail 'absent Home restore output was rejected'
+for _ in $(seq 1 50); do
+    status="$(qs_test ipc call settings-backup-behavior status)"
+    jq -e '.calls[-1] == "shell.reload"' <<<"$status" >/dev/null 2>&1 && break
+    sleep 0.1
+done
+jq -e '
+    .calls == [
+        "home.reset",
+        "desktop.reload",
+        "system.apply",
+        "keybinds.reload",
+        "wallpaper.set:/tmp/restored-wallpaper.jpg",
+        "shell.reload"
+    ]
+    and .initialized == false
+    and .favorites == []
+' <<<"$status" >/dev/null || fail "absent Home handoff was wrong: $status"
+
+trap - EXIT
+cleanup
+printf 'settings backup live contract: PASS\n'