diff --git a/clients/apple/Sources/PunktfunkShared/DefaultsKeys.swift b/clients/apple/Sources/PunktfunkShared/DefaultsKeys.swift
index ae3a9d40..f7c9073b 100644
--- a/clients/apple/Sources/PunktfunkShared/DefaultsKeys.swift
+++ b/clients/apple/Sources/PunktfunkShared/DefaultsKeys.swift
@@ -21,6 +21,14 @@ public enum DefaultsKey {
     /// is native either way, so this degenerates to Auto-native there). Read per session by the
     /// stream views' `MatchWindowFollower`.
     public static let matchWindow = "punktfunk.matchWindow"
+    /// Render-resolution multiplier (a `RenderScale` value, default 1.0): the client asks the host
+    /// to render/encode at `chosen resolution × scale`, then the presenter downscales the larger
+    /// decoded frame to this display in one Catmull-Rom pass. > 1 supersamples (sharper, at the cost
+    /// of more bandwidth AND client decode — both grow ∝ scale²); < 1 renders below native for a
+    /// weak host GPU / constrained link (the presenter upscales). Purely client-side — the host just
+    /// sees a normal (larger/smaller) `Mode`, and Automatic bitrate scales with it. Clamped even +
+    /// to the codec's max dimension at connect. Applies to the fixed mode and the match-window path.
+    public static let renderScale = "punktfunk.renderScale"
     public static let compositor = "punktfunk.compositor"
     public static let gamepadType = "punktfunk.gamepadType"
     public static let gamepadID = "punktfunk.gamepadID"
@@ -69,6 +77,21 @@ public enum DefaultsKey {
     public static let hosts = "punktfunk.hosts"
     /// Client-side cursor mode: "auto" (shown only in gamescope sessions), "always", "never".
     public static let cursorMode = "punktfunk.cursorMode"
+    /// Invert the scroll-wheel / two-finger-scroll direction sent to the host (both axes). Off by
+    /// default: the local (natural-scrolling) sign passes through untouched. When on, the sign is
+    /// negated at the single scroll sink (`InputCapture.sendScroll`), so it flips consistently across
+    /// the macOS wheel, the iOS trackpad pan, and a GCMouse wheel. For users whose host expects the
+    /// opposite convention from their local OS preference.
+    public static let invertScroll = "punktfunk.invertScroll"
+    /// Location-based modifier mapping (a `ModifierLayout` value, default `.mac`): which Windows VK
+    /// each PHYSICAL modifier position forwards to the host. `.mac` keeps ⌥ Option → Alt and
+    /// ⌘ Command → Super/Win (the Apple positions). `.windows` swaps the Alt/Super ROLE between the
+    /// Option and Command keys — preserving side (L/R) — so the key nearest the space bar acts as
+    /// Alt and the next one as the Windows key, matching a Windows keyboard's `Ctrl / ⊞ / Alt` row.
+    /// Only what's FORWARDED changes; client-local shortcuts (⌘⎋ &co.) stay on the physical ⌘ key.
+    /// Read live at the wire boundary by `InputCapture`. Control/Shift never move (same position on
+    /// both keyboards).
+    public static let modifierLayout = "punktfunk.modifierLayout"
     /// iPad: capture the mouse/trackpad pointer (pointer lock → relative movement) for games,
     /// rather than forwarding an absolute cursor position. On by default. Only meaningful on iPad
     /// with a hardware mouse/trackpad; the system grants the lock only to a full-screen, frontmost
@@ -132,6 +155,12 @@ extension Notification.Name {
     /// discoverable menu-bar surface.
     public static let punktfunkReleaseCapture = Notification.Name("io.unom.punktfunk.release-capture")
 
+    /// Posted by the app's Stream menu ("Toggle Fullscreen", ⌃⌘F) and by InputCapture's monitor
+    /// when the same combo fires while input is captured (the menu key-equivalent never reaches a
+    /// captured stream view). The key window's `FullscreenController` flips the window's fullscreen
+    /// state. macOS only.
+    public static let punktfunkToggleFullscreen = Notification.Name("io.unom.punktfunk.toggle-fullscreen")
+
     /// Posted by the Live Activity's / Shortcuts' End-stream intent (`EndStreamIntent.perform`,
     /// which runs in the app's process): the app tears the active session down deliberately
     /// (quit-close the host). Same cross-process-signal pattern as `punktfunkReleaseCapture` —
diff --git a/clients/apple/Sources/PunktfunkShared/RenderScale.swift b/clients/apple/Sources/PunktfunkShared/RenderScale.swift
new file mode 100644
index 00000000..57c93a16
--- /dev/null
+++ b/clients/apple/Sources/PunktfunkShared/RenderScale.swift
@@ -0,0 +1,72 @@
+// Render-resolution scaling — the pure geometry behind `DefaultsKey.renderScale`. The client asks
+// the host to render/encode at `chosen resolution × scale` and lets the presenter downscale the
+// larger decoded frame to the display (a Catmull-Rom minification, > 1 = supersampling for
+// sharpness) or upscale a smaller one (< 1 = a performance mode for a weak host GPU / thin link).
+//
+// This is where the multiplier is turned into a host-valid `Mode` dimension: multiply, preserve the
+// aspect ratio, floor to even (the host's `validate_dimensions` rejects odd sizes), and clamp to the
+// codec's per-axis ceiling so the connect can't ask for something the encoder will reject. Kept
+// dependency-free + side-effect-free so it's unit-tested (`RenderScaleTests`) and reused by both the
+// fixed-mode connect and the match-window follower.
+
+import Foundation
+
+public enum RenderScale {
+    /// The supported multiplier range. Below 1 renders under native (upscaled on present); above 1
+    /// supersamples. The UI clamps its slider to this and the connect clamps the raw stored value.
+    public static let range: ClosedRange<Double> = 0.5...4.0
+
+    /// The multipliers the picker offers. 1.0 (Native) is the default; the rest are the round stops
+    /// users reason about.
+    public static let presets: [Double] = [0.5, 0.67, 0.75, 1.0, 1.25, 1.5, 2.0, 3.0, 4.0]
+
+    /// The encoder/host per-axis ceiling for a codec preference string (`DefaultsKey.codec`). H.264
+    /// tops out at 4096 px/axis; HEVC / AV1 / PyroWave (and "auto", which negotiates one of those in
+    /// practice) at 8192. The host enforces the same walls in `codec.rs::validate_dimensions`.
+    public static func maxDimension(codec: String) -> Int {
+        codec == "h264" ? 4096 : 8192
+    }
+
+    /// A compact user-facing label for a multiplier: "Native (1×)", "1.5×", "2× · supersample".
+    /// Shared by every platform's picker so the wording stays identical.
+    public static func label(_ scale: Double) -> String {
+        if scale == 1.0 { return "Native (1×)" }
+        let magnitude = String(format: "%g×", scale)
+        return scale > 1 ? "\(magnitude) · supersample" : magnitude
+    }
+
+    /// Clamp a raw stored multiplier into `range`, treating a missing/zero value as 1.0 (Native).
+    public static func sanitize(_ raw: Double) -> Double {
+        guard raw > 0 else { return 1.0 }
+        return min(max(raw, range.lowerBound), range.upperBound)
+    }
+
+    /// Apply `scale` to a base pixel size, preserving aspect, even-flooring each axis, and clamping
+    /// uniformly so neither axis exceeds `maxDimension` (the larger axis lands on the cap, the ratio
+    /// is kept). Also floors each axis at `minWidth`/`minHeight` (the host never accepts < 320×200).
+    /// The result is a directly host-valid `Mode` width/height.
+    public static func apply(
+        baseWidth: Int,
+        baseHeight: Int,
+        scale rawScale: Double,
+        maxDimension: Int,
+        minWidth: Int = 320,
+        minHeight: Int = 200
+    ) -> (width: UInt32, height: UInt32) {
+        let scale = sanitize(rawScale)
+        var w = Double(max(baseWidth, 1)) * scale
+        var h = Double(max(baseHeight, 1)) * scale
+        // Uniform down-clamp if either axis blew past the ceiling — keep the aspect ratio intact.
+        let cap = Double(maxDimension)
+        let over = max(w / cap, h / cap)
+        if over > 1 {
+            w /= over
+            h /= over
+        }
+        let evenFloor: (Double, Int) -> UInt32 = { value, minimum in
+            let clamped = max(Int(value.rounded(.down)), minimum)
+            return UInt32(clamped / 2 * 2)
+        }
+        return (evenFloor(w, minWidth), evenFloor(h, minHeight))
+    }
+}