diff --git a/Cargo.lock b/Cargo.lock
index ebe7663a14..9e22df11e1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1561,7 +1561,7 @@ dependencies = [
 [[package]]
 name = "collections"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "gpui_util",
  "indexmap",
@@ -2208,7 +2208,7 @@ dependencies = [
 [[package]]
 name = "derive_refineable"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -3391,7 +3391,7 @@ dependencies = [
 [[package]]
 name = "gpui"
 version = "0.2.2"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "accesskit",
  "anyhow",
@@ -3507,7 +3507,7 @@ dependencies = [
 [[package]]
 name = "gpui_linux"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "accesskit",
  "accesskit_unix",
@@ -3559,7 +3559,7 @@ dependencies = [
 [[package]]
 name = "gpui_macos"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "accesskit",
  "accesskit_macos",
@@ -3608,7 +3608,7 @@ dependencies = [
 [[package]]
 name = "gpui_macros"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "heck 0.5.0",
  "proc-macro2",
@@ -3619,7 +3619,7 @@ dependencies = [
 [[package]]
 name = "gpui_platform"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "console_error_panic_hook",
  "gpui",
@@ -3632,7 +3632,7 @@ dependencies = [
 [[package]]
 name = "gpui_shared_string"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "schemars",
  "serde",
@@ -3642,7 +3642,7 @@ dependencies = [
 [[package]]
 name = "gpui_tokio"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "anyhow",
  "gpui",
@@ -3653,7 +3653,7 @@ dependencies = [
 [[package]]
 name = "gpui_util"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "anyhow",
  "log",
@@ -3663,7 +3663,7 @@ dependencies = [
 [[package]]
 name = "gpui_web"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "anyhow",
  "console_error_panic_hook",
@@ -3687,7 +3687,7 @@ dependencies = [
 [[package]]
 name = "gpui_wgpu"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "anyhow",
  "bytemuck",
@@ -3716,7 +3716,7 @@ dependencies = [
 [[package]]
 name = "gpui_windows"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "accesskit",
  "accesskit_windows",
@@ -4048,7 +4048,7 @@ dependencies = [
 [[package]]
 name = "http_client"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "anyhow",
  "async-compression",
@@ -5221,7 +5221,7 @@ checksum = "490cc448043f947bae3cbee9c203358d62dbee0db12107a74be5c30ccfd09771"
 [[package]]
 name = "media"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "anyhow",
  "bindgen",
@@ -6364,7 +6364,7 @@ checksum = "9b4f627cb1b25917193a259e49bdad08f671f8d9708acfd5fe0a8c1455d87220"
 [[package]]
 name = "perf"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "collections",
  "serde",
@@ -7443,7 +7443,7 @@ dependencies = [
 [[package]]
 name = "refineable"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "derive_refineable",
 ]
@@ -8129,7 +8129,7 @@ checksum = "c62751faa8bc286982334a082fe125184a29fc89d17775766e4f891b7d726980"
 [[package]]
 name = "scheduler"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "async-task",
  "backtrace",
@@ -8914,7 +8914,7 @@ checksum = "13c2bddecc57b384dee18652358fb23172facb8a2c51ccc10d74c157bdea3292"
 [[package]]
 name = "sum_tree"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "heapless 0.9.3",
  "log",
@@ -10331,7 +10331,7 @@ checksum = "06abde3611657adf66d383f00b093d7faecc7fa57071cce2578660c9f1010821"
 [[package]]
 name = "util_macros"
 version = "0.1.0"
-source = "git+https://github.com/zeronsh/zui?rev=18a89af04cfe079d55275b111ac349d5640d9cda#18a89af04cfe079d55275b111ac349d5640d9cda"
+source = "git+https://github.com/katulevskiy/zui?rev=fd28a46632f8dc1a6c430f694ce970cd3f0a3407#fd28a46632f8dc1a6c430f694ce970cd3f0a3407"
 dependencies = [
  "perf",
  "quote",
diff --git a/Cargo.toml b/Cargo.toml
index 9f66383825..4ceb948410 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -172,3 +172,12 @@ inherits = "release"
 lto = "thin"
 codegen-units = 1
 strip = "debuginfo"
+
+# Whole-window scaling patch; also applies to gpui-base's GPUI dependency so
+# the application and component layer share one GPUI type universe.
+# Remove after the patch is merged and the upstream revision is updated.
+[patch."https://github.com/zeronsh/zui"]
+gpui = { git = "https://github.com/katulevskiy/zui", rev = "fd28a46632f8dc1a6c430f694ce970cd3f0a3407" }
+gpui_platform = { git = "https://github.com/katulevskiy/zui", rev = "fd28a46632f8dc1a6c430f694ce970cd3f0a3407" }
+gpui_tokio = { git = "https://github.com/katulevskiy/zui", rev = "fd28a46632f8dc1a6c430f694ce970cd3f0a3407" }
+gpui_macros = { git = "https://github.com/katulevskiy/zui", rev = "fd28a46632f8dc1a6c430f694ce970cd3f0a3407" }
diff --git a/crates/ui/Cargo.toml b/crates/ui/Cargo.toml
index 60bd67d758..14e6b9901e 100644
--- a/crates/ui/Cargo.toml
+++ b/crates/ui/Cargo.toml
@@ -12,6 +12,7 @@ browser-fixture = []
 windows-render-fixture = []
 appshots-fixture = ["gpui_platform/test-support"]
 resource-profile = ["gpui/bench", "gpui_platform/test-support"]
+ui-scale-fixture = ["gpui/bench", "gpui_platform/test-support"]
 
 [[example]]
 name = "macos-resource-profile"
@@ -33,6 +34,10 @@ required-features = ["windows-render-fixture"]
 name = "appshots-fixture"
 required-features = ["appshots-fixture"]
 
+[[example]]
+name = "ui-scale-fixture"
+required-features = ["ui-scale-fixture"]
+
 [[example]]
 name = "new-project-fixture"
 required-features = ["project-palette-fixture"]
diff --git a/crates/ui/examples/ui-scale-fixture.rs b/crates/ui/examples/ui-scale-fixture.rs
new file mode 100644
index 0000000000..6939310c51
--- /dev/null
+++ b/crates/ui/examples/ui-scale-fixture.rs
@@ -0,0 +1,199 @@
+//! Native UI-scale evidence from an isolated profile; no engine or model calls.
+//! Run with ZERON_OPEN_ROUTE=settings/appearance.
+use gpui::{AppContext, AsyncApp, Bounds, WindowBounds, WindowOptions, px, size};
+use std::{path::PathBuf, time::Duration};
+use zeron_ui::*;
+
+async fn pause(cx: &mut AsyncApp) {
+    cx.background_executor()
+        .timer(Duration::from_millis(300))
+        .await;
+}
+
+fn press(handle: gpui::AnyWindowHandle, cx: &mut AsyncApp, combo: &str) -> anyhow::Result<()> {
+    handle.update(cx, |_, window, cx| {
+        window.draw(cx).clear();
+        window.present_if_needed();
+        let keystroke = gpui::Keystroke::parse(combo).unwrap();
+        window.dispatch_event(
+            gpui::PlatformInput::KeyDown(gpui::KeyDownEvent {
+                keystroke: keystroke.clone(),
+                is_held: false,
+                prefer_character_input: false,
+            }),
+            cx,
+        );
+        window.dispatch_event(
+            gpui::PlatformInput::KeyUp(gpui::KeyUpEvent { keystroke }),
+            cx,
+        );
+    })?;
+    Ok(())
+}
+
+fn capture(
+    handle: gpui::AnyWindowHandle,
+    cx: &mut AsyncApp,
+    output: &std::path::Path,
+    name: &str,
+    expected: u16,
+) -> anyhow::Result<()> {
+    handle.update(cx, |_, window, cx| {
+        assert_eq!(settings::current(cx).ui_scale_percent, expected);
+        assert_eq!(window.ui_scale(), ui_scale::factor(expected));
+        window.draw(cx).clear();
+        window.present_if_needed();
+        let path = output.join(format!("{name}.png"));
+        #[cfg(target_os = "linux")]
+        {
+            anyhow::ensure!(
+                std::env::var_os("WAYLAND_DISPLAY").is_none(),
+                "Linux capture needs an isolated X11 display with WAYLAND_DISPLAY unset"
+            );
+            let status = std::process::Command::new("import")
+                .args(["-silent", "-window", "UI scale fixture"])
+                .arg(path)
+                .status()?;
+            anyhow::ensure!(status.success(), "native X11 window capture failed");
+        }
+        #[cfg(not(target_os = "linux"))]
+        window.render_to_image()?.save(path)?;
+        Ok(())
+    })?
+}
+
+fn main() -> anyhow::Result<()> {
+    tracing_subscriber::fmt().with_env_filter("warn").init();
+    let output = PathBuf::from(std::env::args().nth(1).expect("output directory"));
+    std::fs::create_dir_all(&output)?;
+    let temp = tempfile::tempdir()?;
+    let data = temp.path().to_path_buf();
+    let runtime = tokio::runtime::Runtime::new()?;
+    let _guard = runtime.enter();
+    gpui_platform::application()
+        .with_assets(icons::Assets)
+        .run(move |cx| {
+            gpui_tokio::init(cx);
+            gpui_base::init(cx);
+            let mut saved = settings::UiSettings::default();
+            saved.reduce_motion = motion::ReduceMotion::On;
+            saved.appearance = appearance::AppearanceMode::Dark;
+            settings::init(saved.clone(), data.clone(), cx);
+            let fonts = typography::register_fonts(cx);
+            typography::init(
+                saved.ui_font_family.clone(),
+                saved.ui_font_size,
+                saved.terminal_font_family.clone(),
+                saved.terminal_font_size,
+                saved.code_font_family.clone(),
+                saved.code_font_size,
+                fonts,
+                cx,
+            );
+            theme_library::init(data.clone(), cx);
+            appearance::init(
+                saved.appearance,
+                saved.theme_selection,
+                saved.accent,
+                saved.surface,
+                cx,
+            );
+            history::init(
+                saved.git_history_columns,
+                saved.git_history_column_widths,
+                saved.git_history_column_order,
+                saved.git_history_author_display,
+                cx,
+            );
+            motion::init(
+                saved.reduce_motion,
+                saved.pause_animations_in_background,
+                cx,
+            );
+            composer::init(cx, saved.composer_send_behavior);
+            terminal::panel::init(cx);
+            app_menus::init(cx);
+            let state = cx.new(|_| {
+                let mut state = state::AppState::new();
+                state.connection = zeron_proto::view::ConnectionStatus::Ready;
+                state.workspace_scope = Some(zeron_proto::WorkspaceScope::Local);
+                state.local_device_id = Some("fixture".into());
+                state.auto_selected = true;
+                state.chats_synced = true;
+                state.spaces_synced = true;
+                state
+            });
+            let boot = EngineBootConfig {
+                data_dir: data.clone(),
+                ipc_port: 0,
+                edge_url: String::new(),
+                edge_token: None,
+                org_id: None,
+                workos_client_id: None,
+                default_harness: HarnessId::Mock,
+            };
+            let handle = cx
+                .open_window(
+                    WindowOptions {
+                        window_bounds: Some(WindowBounds::Windowed(Bounds::new(
+                            gpui::point(px(20.), px(20.)),
+                            size(px(1440.), px(1080.)),
+                        ))),
+                        window_min_size: Some(size(px(900.), px(600.))),
+                        window_decorations: cfg!(target_os = "linux")
+                            .then_some(gpui::WindowDecorations::Client),
+                        app_owns_titlebar_drag: true,
+                        window_background: theme::Theme::of(cx).window_background_appearance(),
+                        app_id: Some("zeron-ui-scale-fixture".into()),
+                        titlebar: Some(gpui::TitlebarOptions {
+                            title: Some("UI scale fixture".into()),
+                            appears_transparent: true,
+                            ..Default::default()
+                        }),
+                        ..Default::default()
+                    },
+                    |window, cx| {
+                        window.set_rem_size(px(typography::font_size(cx).pixels()));
+                        cx.new(|cx| shell::Shell::new(state, boot, cx))
+                    },
+                )
+                .unwrap();
+            cx.activate(true);
+            cx.spawn(async move |cx| {
+                let result: anyhow::Result<()> = async {
+                    pause(cx).await;
+                    capture(handle.into(), cx, &output, "appearance-100", 100)?;
+                    for _ in 0..5 {
+                        press(handle.into(), cx, "ctrl-shift-+")?;
+                    }
+                    pause(cx).await;
+                    capture(handle.into(), cx, &output, "appearance-150", 150)?;
+                    assert_eq!(settings::UiSettings::load(&data).ui_scale_percent, 150);
+                    // Native bounds updates must preserve the selected zoom.
+                    handle.update(cx, |_, window, cx| window.bounds_changed(cx))?;
+                    capture(
+                        handle.into(),
+                        cx,
+                        &output,
+                        "appearance-150-after-resize",
+                        150,
+                    )?;
+                    press(handle.into(), cx, "ctrl-shift-0")?;
+                    pause(cx).await;
+                    capture(handle.into(), cx, &output, "appearance-reset-100", 100)?;
+                    handle.update(cx, |_, window, cx| {
+                        appearance::set_mode(appearance::AppearanceMode::Light, cx);
+                        ui_scale::set(120, window, cx);
+                    })?;
+                    pause(cx).await;
+                    capture(handle.into(), cx, &output, "appearance-light-120", 120)?;
+                    Ok(())
+                }
+                .await;
+                result.expect("UI scale fixture failed");
+                cx.update(|cx| cx.quit());
+            })
+            .detach();
+        });
+    Ok(())
+}
diff --git a/crates/ui/src/browser/mod.rs b/crates/ui/src/browser/mod.rs
index 6b4cb526a8..92ac1d882e 100644
--- a/crates/ui/src/browser/mod.rs
+++ b/crates/ui/src/browser/mod.rs
@@ -26,6 +26,7 @@ pub(crate) fn bind_keys(cx: &mut App, keymap: &crate::settings::KeymapConfig) {
     // already assign mod-shift-r to the right pane.
     let available = |combo: &str, own: Option<ShortcutId>| {
         !combo.is_empty()
+            && !crate::ui_scale::is_reserved_combo(combo)
             && !ShortcutId::ALL.iter().any(|id| {
                 Some(*id) != own
                     && gpui::Keystroke::parse(&platform_combo(keymap.get(*id))).ok()
@@ -200,6 +201,11 @@ impl BrowserSurface {
                     .iter()
                     .filter(|id| **id != crate::settings::ShortcutId::SaveFile)
                     .map(|id| crate::settings::platform_combo(keymap.get(*id)))
+                    .chain(
+                        crate::ui_scale::combos()
+                            .into_iter()
+                            .map(|(combo, _)| combo.to_owned()),
+                    )
                     .collect(),
             );
         }
diff --git a/crates/ui/src/browser/view.rs b/crates/ui/src/browser/view.rs
index 47d268754b..842a47c830 100644
--- a/crates/ui/src/browser/view.rs
+++ b/crates/ui/src/browser/view.rs
@@ -534,6 +534,9 @@ impl Render for BrowserSurface {
                             let right =
                                 (window.viewport_size().width - right_occlusion).max(mask.left());
                             mask.size.width = mask.size.width.min(right - mask.left());
+                            let bounds = window.ui_to_platform_bounds(bounds);
+                            let mask = window.ui_to_platform_bounds(mask);
+                            let resize_inset = resize_inset * window.ui_scale();
                             let dragging = cx.has_active_drag();
                             window.on_present(move || {
                                 if let Some(native) = native.upgrade() {
diff --git a/crates/ui/src/lib.rs b/crates/ui/src/lib.rs
index 79a33d9886..d9e2eedaa7 100644
--- a/crates/ui/src/lib.rs
+++ b/crates/ui/src/lib.rs
@@ -61,6 +61,7 @@ pub mod theme;
 pub mod theme_library;
 pub mod transcript;
 pub mod typography;
+pub mod ui_scale;
 mod workspace_links;
 
 use std::path::PathBuf;
@@ -420,6 +421,7 @@ fn open_main_window(
                 ..Default::default()
             },
             move |window, cx| {
+                ui_scale::apply_to_window(settings::current(cx).ui_scale_percent, window);
                 window.set_rem_size(px(typography::font_size(cx).pixels()));
                 // React to the user flipping macOS between light and dark. Detached:
                 // the subscription lives as long as the window does, and the window
diff --git a/crates/ui/src/settings.rs b/crates/ui/src/settings.rs
index e142454e63..7a97c77ee3 100644
--- a/crates/ui/src/settings.rs
+++ b/crates/ui/src/settings.rs
@@ -896,6 +896,8 @@ pub struct UiSettings {
     pub ui_font_family: crate::typography::UiFontFamily,
     /// Base size for interface and conversational prose.
     pub ui_font_size: crate::typography::UiFontSize,
+    /// Whole-interface zoom, independent of fonts and system display density.
+    pub ui_scale_percent: u16,
     /// Terminal family and absolute pixel size. Only fixed-width families
     /// qualify, including compatible Nerd Fonts.
     pub terminal_font_family: crate::typography::UiFontFamily,
@@ -1008,6 +1010,7 @@ impl Default for UiSettings {
             git_history_author_display: GitHistoryAuthorDisplay::default(),
             ui_font_family: crate::typography::UiFontFamily::default(),
             ui_font_size: crate::typography::UiFontSize::default(),
+            ui_scale_percent: crate::ui_scale::DEFAULT_PERCENT,
             terminal_font_family: crate::typography::UiFontFamily::GeistMono,
             terminal_font_size: crate::typography::TERMINAL_FONT_SIZE_DEFAULT,
             code_font_family: crate::typography::UiFontFamily::GeistMono,
@@ -1615,11 +1618,17 @@ impl UiSettings {
         self.git_history_column_widths = self.git_history_column_widths.clamped();
         self.git_history_column_order = self.git_history_column_order.normalized();
         self.ui_font_size = self.ui_font_size.normalized();
+        self.ui_scale_percent = crate::ui_scale::clamp(self.ui_scale_percent);
         if let Some(background) = self.new_thread_composer_background.as_mut() {
             background.adjustment = background.adjustment.normalized();
         }
         self.keymap.heal_jump_slots();
         self.keymap.heal_reserved_composer_shortcuts();
+        for id in ShortcutId::ALL {
+            if crate::ui_scale::is_reserved_combo(self.keymap.get(id)) {
+                self.keymap.reset(id);
+            }
+        }
         self
     }
 
@@ -2563,6 +2572,7 @@ mod tests {
             git_history_author_display: GitHistoryAuthorDisplay::Name,
             ui_font_family: crate::typography::UiFontFamily::Installed("Arial".into()),
             ui_font_size: crate::typography::UiFontSize::ALL[5],
+            ui_scale_percent: 150,
             theme_selection: zeron_theme::ThemeSelection {
                 light: "catppuccin-latte".into(),
                 dark: "catppuccin-mocha".into(),
diff --git a/crates/ui/src/settings/appearance.rs b/crates/ui/src/settings/appearance.rs
index 3fc10efcce..08eb95fea7 100644
--- a/crates/ui/src/settings/appearance.rs
+++ b/crates/ui/src/settings/appearance.rs
@@ -3912,6 +3912,91 @@ impl Render for AppearancePage {
         let terminal_size = self.render_size_picker(FontKind::Terminal, &theme, fixed.clone(), cx);
         let code_size = self.render_size_picker(FontKind::Code, &theme, fixed.clone(), cx);
 
+        let scale = crate::settings::current(cx).ui_scale_percent;
+        let mut scale_controls = div().flex().items_center().gap(px(6.0));
+        for (id, label, target, enabled) in [
+            (
+                "ui-scale-decrease",
+                "−",
+                crate::ui_scale::stepped(scale, -1),
+                scale > crate::ui_scale::MIN_PERCENT,
+            ),
+            (
+                "ui-scale-increase",
+                "+",
+                crate::ui_scale::stepped(scale, 1),
+                scale < crate::ui_scale::MAX_PERCENT,
+            ),
+            (
+                "ui-scale-reset",
+                "Reset",
+                crate::ui_scale::DEFAULT_PERCENT,
+                scale != crate::ui_scale::DEFAULT_PERCENT,
+            ),
+        ] {
+            if id == "ui-scale-increase" {
+                scale_controls = scale_controls.child(
+                    div()
+                        .id("ui-scale-value")
+                        .min_w(px(48.0))
+                        .text_center()
+                        .text_size(crate::typography::ui_rems(13.0))
+                        .child(format!("{scale}%")),
+                );
+            }
+            scale_controls = scale_controls.child(
+                widgets::text_action(&theme, widgets::ActionTone::Outlined, label)
+                    .id(id)
+                    .debug_selector(move || id.into())
+                    .aria_label(match id {
+                        "ui-scale-decrease" => "Decrease UI scale",
+                        "ui-scale-increase" => "Increase UI scale",
+                        _ => "Reset UI scale to 100%",
+                    })
+                    .min_w(px(32.0))
+                    .justify_center()
+                    .when(!enabled, |button| button.opacity(0.4).cursor_default())
+                    .when(enabled, |button| {
+                        button
+                            .tab_index(0)
+                            .role(gpui::Role::Button)
+                            .focus_visible(|s| s.border_2().border_color(theme.accent))
+                            .on_click(cx.listener(move |_, _, window, cx| {
+                                crate::ui_scale::set(target, window, cx);
+                            }))
+                    }),
+            );
+        }
+        let scale_card = widgets::section_card(&theme)
+            .mt_0()
+            .font_family(fixed.clone())
+            .child(
+                widgets::card_row(&theme, true)
+                    .justify_between()
+                    .child(
+                        div()
+                            .flex_1()
+                            .child(widgets::row_title(&theme, "UI scale"))
+                            .child(widgets::meta_line(
+                                &theme,
+                                vec![
+                                    div()
+                                        .child("Resize the entire interface · 50–200%")
+                                        .into_any_element(),
+                                ],
+                            ))
+                            .child(widgets::meta_line(
+                                &theme,
+                                vec![
+                                    div()
+                                        .child("Ctrl+Shift+Plus / Minus · Ctrl+Shift+0 to reset")
+                                        .into_any_element(),
+                                ],
+                            )),
+                    )
+                    .child(scale_controls),
+            );
+        let scale_section = widgets::section(&theme, "Interface scale", scale_card);
         let mut font_rows = widgets::section_card(&theme)
             .mt_0()
             .font_family(fixed.clone());
@@ -4036,6 +4121,7 @@ impl Render for AppearancePage {
                                     .mt(px(24.0))
                                     .gap(px(12.0)),
                                 )
+                                .child(scale_section)
                                 .child(
                                     widgets::section_card(&theme)
                                         .children(color_rows)
diff --git a/crates/ui/src/settings/shortcuts.rs b/crates/ui/src/settings/shortcuts.rs
index e64a47a486..6cfa2c8059 100644
--- a/crates/ui/src/settings/shortcuts.rs
+++ b/crates/ui/src/settings/shortcuts.rs
@@ -249,6 +249,15 @@ impl ShortcutsPage {
                     cx.stop_propagation();
                     return;
                 }
+                if crate::ui_scale::is_reserved_combo(&combo) {
+                    self.conflict_notice = Some(
+                        format!("{} is reserved for UI scaling.", display_combo(&combo)).into(),
+                    );
+                    self.stop_recording();
+                    cx.notify();
+                    cx.stop_propagation();
+                    return;
+                }
                 if send_combo_is_reserved(self.composer_send_behavior, &combo) {
                     self.conflict_notice = Some(
                         format!("{} is reserved for the composer.", display_combo(&combo)).into(),
diff --git a/crates/ui/src/shell.rs b/crates/ui/src/shell.rs
index 46b26e3024..867536c9b3 100644
--- a/crates/ui/src/shell.rs
+++ b/crates/ui/src/shell.rs
@@ -404,10 +404,10 @@ pub fn apply_keymap(
 ) {
     fn valid_or_default(combo: &str, fallback: &str) -> String {
         let candidate = platform_combo(combo);
-        if Keystroke::parse(&candidate).is_ok() {
+        if Keystroke::parse(&candidate).is_ok() && !crate::ui_scale::is_reserved_combo(combo) {
             candidate
         } else {
-            tracing::warn!(%combo, "unparseable shortcut combo; using default");
+            tracing::warn!(%combo, "invalid or reserved shortcut combo; using default");
             platform_combo(fallback)
         }
     }
@@ -422,6 +422,7 @@ pub fn apply_keymap(
     // close, ⌘M minimize, ⌘H hide on macOS) — these back the native menu
     // key equivalents and must survive keymap re-application.
     crate::app_menus::bind_keys(cx);
+    crate::ui_scale::bind_keys(cx);
     cx.bind_keys([
         KeyBinding::new(
             &valid_or_default(&keymap.random_wallpaper, "mod-u"),
@@ -4478,6 +4479,7 @@ impl Shell {
         self.settings.open_web_links_in_zeron = current.open_web_links_in_zeron;
         self.settings.ui_font_family = current.ui_font_family;
         self.settings.ui_font_size = current.ui_font_size;
+        self.settings.ui_scale_percent = current.ui_scale_percent;
         self.settings.terminal_font_family = current.terminal_font_family;
         self.settings.terminal_font_size = current.terminal_font_size;
         self.settings.code_font_family = current.code_font_family;
@@ -6111,6 +6113,11 @@ impl Shell {
         // The tween runs in cluster-start coordinates; the spacer is that
         // minus the container's own padding.
         let start = self.eval_tween(self.titlebar_tween, titlebar_cluster_start(fullscreen));
+        let start = if fullscreen {
+            start
+        } else {
+            start / crate::ui_scale::factor(self.settings.ui_scale_percent)
+        };
         let width = (start - container_pad).max(0.0);
         Some(div().flex_none().h_full().w(px(width)).into_any_element())
     }
@@ -6131,6 +6138,11 @@ impl Shell {
             self.titlebar_tween,
             cluster_buttons_start(is_macos, fullscreen, self.linux_left_caption_count()),
         );
+        let cluster = if is_macos && !fullscreen {
+            cluster / crate::ui_scale::factor(self.settings.ui_scale_percent)
+        } else {
+            cluster
+        };
         cluster + CLUSTER_BUTTONS_WIDTH + TITLEBAR_IDENTITY_GAP
     }
 
@@ -12436,6 +12448,15 @@ impl Render for Shell {
             // no-ops (zeron __root.tsx gates the hotkey on `!isSettings`, and
             // the terminal panel is only mounted on session routes). The
             // sidebar toggle stays live everywhere, as in the original.
+            .on_action(cx.listener(|_, _: &crate::ui_scale::Increase, window, cx| {
+                crate::ui_scale::step(1, window, cx);
+            }))
+            .on_action(cx.listener(|_, _: &crate::ui_scale::Decrease, window, cx| {
+                crate::ui_scale::step(-1, window, cx);
+            }))
+            .on_action(cx.listener(|_, _: &crate::ui_scale::Reset, window, cx| {
+                crate::ui_scale::set(crate::ui_scale::DEFAULT_PERCENT, window, cx);
+            }))
             .on_action(cx.listener(|this, _: &ToggleTerminal, window, cx| {
                 if matches!(this.route, Route::Chat) {
                     this.toggle_terminal(window, cx)
@@ -16412,6 +16433,112 @@ mod settings_modal_regressions {
         assert_eq!(press(&keymap.new_session), (Route::Chat, None));
     }
 
+    #[gpui::test]
+    fn ui_scale_appearance_buttons_use_scaled_hit_testing(cx: &mut TestAppContext) {
+        let dir = tempfile::tempdir().unwrap();
+        init_settings_test(settings::UiSettings::default(), dir.path(), cx);
+        let (shell, cx) = cx.add_window_view(|_, cx| {
+            let mut shell = test_shell(dir.path(), cx);
+            shell.debug_gate = Some(GatePhase::Ready);
+            shell.splash = SplashPhase::Gone;
+            shell
+        });
+        shell.update(cx, |shell, cx| {
+            shell.open_settings(SettingsSection::Appearance, cx)
+        });
+        for (selector, expected) in [
+            ("ui-scale-increase", 110),
+            ("ui-scale-increase", 120),
+            ("ui-scale-decrease", 110),
+            ("ui-scale-reset", 100),
+        ] {
+            cx.update(|window, cx| window.draw(cx).clear());
+            let center = cx
+                .debug_bounds(selector)
+                .expect("scale control visible")
+                .center();
+            let position = cx.update(|window, _| center * window.ui_scale());
+            cx.simulate_click(position, gpui::Modifiers::default());
+            cx.update(|window, cx| {
+                assert_eq!(
+                    settings::current(cx).ui_scale_percent,
+                    expected,
+                    "{selector}"
+                );
+                assert_eq!(window.ui_scale(), crate::ui_scale::factor(expected));
+            });
+        }
+    }
+
+    #[gpui::test]
+    fn ui_scale_shortcuts_work_from_settings_and_preserve_independent_settings(
+        cx: &mut TestAppContext,
+    ) {
+        let dir = tempfile::tempdir().unwrap();
+        init_settings_test(settings::UiSettings::default(), dir.path(), cx);
+        let window = cx.add_window(|_, cx| {
+            let mut shell = test_shell(dir.path(), cx);
+            shell.debug_gate = Some(GatePhase::Ready);
+            shell.splash = SplashPhase::Gone;
+            shell
+        });
+        window
+            .update(cx, |shell, _, cx| {
+                shell.open_settings(SettingsSection::Appearance, cx)
+            })
+            .unwrap();
+        cx.run_until_parked();
+        for (combo, expected) in [
+            ("ctrl-shift-+", 110),
+            ("ctrl-shift-=", 120),
+            ("ctrl-shift--", 110),
+            ("ctrl-shift-_", 100),
+            ("ctrl-shift-+", 110),
+        ] {
+            cx.simulate_keystrokes(window.into(), combo);
+            window
+                .update(cx, |shell, window, cx| {
+                    assert_eq!(settings::current(cx).ui_scale_percent, expected, "{combo}");
+                    assert_eq!(window.ui_scale(), crate::ui_scale::factor(expected));
+                    assert_eq!(shell.route, Route::Settings(SettingsSection::Appearance));
+                    // A later pane save must not restore the shell's stale scale.
+                    shell.settings.sidebar_width = 300.0;
+                    shell.schedule_save(cx);
+                    assert_eq!(settings::current(cx).ui_scale_percent, expected);
+                })
+                .unwrap();
+        }
+        cx.update(|cx| {
+            apply_keymap(
+                cx,
+                &KeymapConfig::default(),
+                ComposerSendBehavior::default(),
+            )
+        });
+        cx.simulate_keystrokes(window.into(), "ctrl-shift-0");
+        window
+            .update(cx, |_, window, cx| {
+                assert_eq!(window.ui_scale(), 1.0);
+                assert_eq!(settings::current(cx).ui_scale_percent, 100);
+                settings::flush(cx);
+            })
+            .unwrap();
+        window
+            .update(cx, |shell, _, cx| shell.close_settings(cx))
+            .unwrap();
+        cx.run_until_parked();
+        window
+            .update(cx, |shell, window, cx| {
+                window.focus(&shell.composer.focus_handle(cx), cx);
+            })
+            .unwrap();
+        cx.simulate_keystrokes(window.into(), "ctrl-shift-+");
+        assert_eq!(cx.read(|cx| settings::current(cx).ui_scale_percent), 110);
+        cx.simulate_keystrokes(window.into(), "ctrl-shift-0");
+        assert_eq!(UiSettings::load(dir.path()).ui_scale_percent, 100);
+        assert_eq!(UiSettings::load(dir.path()).sidebar_width, 300.0);
+    }
+
     #[gpui::test]
     fn settings_reopen_where_they_were_left(cx: &mut TestAppContext) {
         let dir = tempfile::tempdir().unwrap();
diff --git a/crates/ui/src/ui_scale.rs b/crates/ui/src/ui_scale.rs
new file mode 100644
index 0000000000..8bf629b11e
--- /dev/null
+++ b/crates/ui/src/ui_scale.rs
@@ -0,0 +1,211 @@
+//! Device-local, whole-window zoom. Font preferences remain independent.
+use gpui::{App, KeyBinding, Keystroke, Window, actions};
+
+use crate::settings::{self, SavePolicy};
+
+pub const MIN_PERCENT: u16 = 50;
+pub const MAX_PERCENT: u16 = 200;
+pub const DEFAULT_PERCENT: u16 = 100;
+pub const STEP_PERCENT: u16 = 10;
+
+actions!(ui_scale, [Increase, Decrease, Reset]);
+
+pub fn clamp(percent: u16) -> u16 {
+    percent.clamp(MIN_PERCENT, MAX_PERCENT)
+}
+
+pub fn factor(percent: u16) -> f32 {
+    f32::from(clamp(percent)) / 100.0
+}
+
+pub fn stepped(percent: u16, direction: i16) -> u16 {
+    (i32::from(clamp(percent)) + i32::from(direction) * i32::from(STEP_PERCENT))
+        .clamp(i32::from(MIN_PERCENT), i32::from(MAX_PERCENT)) as u16
+}
+
+pub fn apply_to_window(percent: u16, window: &mut Window) {
+    let scale = factor(percent);
+    window.set_ui_scale(scale);
+    // AppKit keeps the traffic lights at native size. Align their centers
+    // with the scaled titlebar controls, including when the UI shrinks.
+    #[cfg(target_os = "macos")]
+    window.set_traffic_light_position(gpui::point(gpui::px(14.0), gpui::px(21.0 * scale - 7.0)));
+}
+
+pub fn set(percent: u16, window: &mut Window, cx: &mut App) {
+    let percent = clamp(percent);
+    settings::update(SavePolicy::Immediate, cx, |settings| {
+        settings.ui_scale_percent = percent;
+    });
+    apply_to_window(percent, window);
+    // The active window is already borrowed. Update other open windows without
+    // trying to reenter it, so they share the same device-local preference.
+    for handle in cx.windows() {
+        if handle != window.window_handle() {
+            let _ = handle.update(cx, |_, window, _| apply_to_window(percent, window));
+        }
+    }
+    cx.refresh_windows();
+}
+
+pub fn step(direction: i16, window: &mut Window, cx: &mut App) {
+    set(
+        stepped(settings::current(cx).ui_scale_percent, direction),
+        window,
+        cx,
+    );
+}
+
+// Backends can report either the physical punctuation key or its shifted
+// character. Accept both, and preserve the requested Ctrl chords on macOS
+// alongside the usual Command equivalents.
+pub(crate) fn combos() -> Vec<(&'static str, u8)> {
+    let mut combos = vec![
+        ("ctrl-shift-=", 0),
+        ("ctrl-shift-+", 0),
+        ("ctrl-shift--", 1),
+        ("ctrl-shift-_", 1),
+        ("ctrl-shift-0", 2),
+        ("ctrl-shift-)", 2),
+    ];
+    if cfg!(target_os = "macos") {
+        combos.extend([
+            ("cmd-shift-=", 0),
+            ("cmd-shift-+", 0),
+            ("cmd-shift--", 1),
+            ("cmd-shift-_", 1),
+            ("cmd-shift-0", 2),
+            ("cmd-shift-)", 2),
+        ]);
+    }
+    combos
+}
+
+pub fn bind_keys(cx: &mut App) {
+    cx.bind_keys(combos().into_iter().map(|(combo, action)| match action {
+        0 => KeyBinding::new(combo, Increase, None),
+        1 => KeyBinding::new(combo, Decrease, None),
+        _ => KeyBinding::new(combo, Reset, None),
+    }));
+}
+
+pub fn is_reserved_combo(combo: &str) -> bool {
+    let Ok(candidate) = Keystroke::parse(&settings::platform_combo(combo)) else {
+        return false;
+    };
+    combos()
+        .into_iter()
+        .any(|(combo, _)| Keystroke::parse(combo).is_ok_and(|key| key == candidate))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    struct ScaleProbe {
+        clicks: usize,
+        scroll: gpui::Point<gpui::Pixels>,
+    }
+
+    impl gpui::Render for ScaleProbe {
+        fn render(
+            &mut self,
+            _: &mut Window,
+            cx: &mut gpui::Context<Self>,
+        ) -> impl gpui::IntoElement {
+            use gpui::prelude::*;
+            gpui::div().size_full().child(
+                gpui::div()
+                    .absolute()
+                    .left(gpui::px(20.))
+                    .top(gpui::px(20.))
+                    .w(gpui::px(100.))
+                    .h(gpui::px(80.))
+                    .on_mouse_down(
+                        gpui::MouseButton::Left,
+                        cx.listener(|this, _, _, _| this.clicks += 1),
+                    )
+                    .on_scroll_wheel(cx.listener(|this, event: &gpui::ScrollWheelEvent, _, _| {
+                        this.scroll = event.delta.pixel_delta(gpui::px(16.));
+                    })),
+            )
+        }
+    }
+
+    #[gpui::test]
+    fn ui_scale_native_hit_testing_and_scroll_stay_aligned(cx: &mut gpui::TestAppContext) {
+        let (view, cx) = cx.add_window_view(|window, _| {
+            window.set_ui_scale(1.5);
+            ScaleProbe {
+                clicks: 0,
+                scroll: Default::default(),
+            }
+        });
+        cx.simulate_event(gpui::MouseDownEvent {
+            button: gpui::MouseButton::Left,
+            position: gpui::point(gpui::px(150.), gpui::px(90.)),
+            ..Default::default()
+        });
+        assert_eq!(view.read_with(cx, |view, _| view.clicks), 1);
+        cx.simulate_event(gpui::ScrollWheelEvent {
+            position: gpui::point(gpui::px(150.), gpui::px(90.)),
+            delta: gpui::ScrollDelta::Pixels(gpui::point(gpui::px(30.), gpui::px(60.))),
+            ..Default::default()
+        });
+        assert_eq!(
+            view.read_with(cx, |view, _| view.scroll),
+            gpui::point(gpui::px(20.), gpui::px(40.))
+        );
+    }
+
+    #[test]
+    fn scale_steps_clamp_without_overflow_and_reset_to_default() {
+        assert_eq!(stepped(100, 1), 110);
+        assert_eq!(stepped(100, -1), 90);
+        assert_eq!(stepped(200, 1), 200);
+        assert_eq!(stepped(50, -1), 50);
+        assert_eq!(stepped(u16::MAX, i16::MAX), 200);
+        assert_eq!(stepped(0, i16::MIN), 50);
+        assert_eq!(factor(DEFAULT_PERCENT), 1.0);
+    }
+
+    #[test]
+    fn scaling_shortcuts_parse_and_are_reserved() {
+        for (combo, _) in combos() {
+            Keystroke::parse(combo).unwrap();
+            assert!(is_reserved_combo(combo));
+        }
+        assert!(!is_reserved_combo("mod-s"));
+        assert!(!is_reserved_combo("ctrl-+"));
+    }
+
+    #[test]
+    fn ui_scale_reserved_shortcuts_heal_only_colliding_preferences() {
+        let mut saved = settings::UiSettings::default();
+        saved.keymap.random_wallpaper = "ctrl-shift-+".into();
+        saved.keymap.save_file = "mod-alt-s".into();
+        let healed = saved.clamped();
+        assert_eq!(
+            healed.keymap.random_wallpaper,
+            settings::ShortcutId::RandomWallpaper.default_combo()
+        );
+        assert_eq!(healed.keymap.save_file, "mod-alt-s");
+    }
+
+    #[test]
+    fn scale_defaults_migrates_clamps_and_round_trips() {
+        let legacy: settings::UiSettings = serde_json::from_str("{}").unwrap();
+        assert_eq!(legacy.ui_scale_percent, 100);
+        let dir = tempfile::tempdir().unwrap();
+        let mut settings = settings::UiSettings::default();
+        settings.ui_scale_percent = 150;
+        settings.save(dir.path()).unwrap();
+        let restored = settings::UiSettings::load(dir.path());
+        assert_eq!(restored.ui_scale_percent, 150);
+        assert_eq!(restored.ui_font_size, settings.ui_font_size);
+        settings.ui_scale_percent = 0;
+        assert_eq!(settings.clone().clamped().ui_scale_percent, 50);
+        settings.ui_scale_percent = u16::MAX;
+        assert_eq!(settings.clamped().ui_scale_percent, 200);
+    }
+}
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@@ -0,0 +1,54 @@
+# Desktop UI scale
+
+Settings → Appearance → Interface scale resizes text, icons, spacing, and panes together. Use the minus and plus buttons to change the scale in 10 percentage point steps between 50% and 200%, or Reset to return to 100%.
+
+Keyboard shortcuts work from conversations and settings:
+
+- `Ctrl+Shift+Plus` increases the scale.
+- `Ctrl+Shift+Minus` decreases the scale.
+- `Ctrl+Shift+0` resets to 100%.
+
+macOS also accepts the corresponding Command shortcuts. Both shifted punctuation and physical key spellings are bound. These shortcuts are reserved; existing conflicting shortcut preferences revert to their defaults, while unrelated customizations remain intact.
+
+The scale is device-local and saved immediately in `ui-settings.json` as `uiScalePercent`. Missing preferences default to 100%. Font preferences and native window geometry remain independent. Startup and reopened windows restore the saved scale; native resize and display changes preserve it.
+
+The [supporting ZUI PR](https://github.com/zeronsh/zui/pull/14) adds `Window::set_ui_scale`. It multiplies the display density for layout/painting, divides the logical viewport and native input coordinates, and converts IME and native child-view bounds back to platform coordinates. A Cargo patch makes the app and `gpui-base` use the same GPUI implementation. Return that dependency to upstream after the supporting ZUI change is merged.
+
+## Native screenshots
+
+The images come from the production shell with an isolated temporary profile and no engine or model calls. The native window remains 1440 × 1080 logical pixels in each capture.
+
+| Dark, 100% | Dark, 150% |
+| --- | --- |
+| ![Appearance at 100%](screenshots/ui-scale/appearance-100.png) | ![Appearance at 150%](screenshots/ui-scale/appearance-150.png) |
+
+![Light appearance at 120%](screenshots/ui-scale/appearance-light-120.png)
+
+Reproduce the captures:
+
+```sh
+ZERON_OPEN_ROUTE=settings/appearance cargo run -p zeron-ui \
+  --example ui-scale-fixture --features ui-scale-fixture -- /tmp/zeron-ui-scale-shots
+```
+
+On Linux, run in an isolated X11 display (Xvfb and ImageMagick are required):
+
+```sh
+Xvfb :97 -screen 0 1600x1200x24 -nolisten tcp &
+env -u WAYLAND_DISPLAY DISPLAY=:97 LP_NUM_THREADS=4 \
+  ZERON_OPEN_ROUTE=settings/appearance cargo run -p zeron-ui \
+  --example ui-scale-fixture --features ui-scale-fixture -- /tmp/zeron-ui-scale-shots
+```
+
+The fixture asserts shortcut changes, immediate persistence, scale retention after native bounds updates, and reset behavior before saving its images. Linux captures the actual X11 app window; macOS uses the native rendered frame.
+
+## Checks
+
+```sh
+cargo test --locked -p zeron-ui --lib -- --test-threads=1
+cargo check --locked -p zeron
+```
+
+The supporting ZUI checkout runs `cargo test -p gpui --lib ui_scale -- --test-threads=1` separately.
+
+Regression coverage includes old settings, persistence/clamping, shifted-key aliases, reserved shortcuts, settings-button hit testing after zoom, pixel-scroll conversion, and retaining zoom through later pane saves. Native screenshots are exercised on Linux; macOS and Windows still need live platform verification.