fix(window): refine cross-platform window frames and eliminate Windows shadow bleed

- Set shadow: false on Windows main and Properties window builders to prevent rectangular DWM shadow bleed behind rounded corners.
- Refine active and inactive window frame tokens across themes for subtle, non-glaring boundaries.
- Apply a 0.5px hairline window border rule specifically on macOS to match native Retina AppKit window strokes.
- Synchronize document platform dataset attribute on app boot across main and Properties windows.
- Update and extend window configuration and platform synchronization test suites.

src-tauri/src/properties_window.rs

@@ -455,12 +455,14 @@ pub async fn open_download_properties_window(
         // A hidden WebView2 must not request focus during construction. The
         // native reveal path focuses it after the window is visible.
         .focused(false);
-    // Native elevation follows the window shape on macOS. On Windows, Tauri
-    // gives an undecorated window the system contour and Windows 11 corners as
-    // well as its shadow. Linux does not implement this API, so its guaranteed
-    // boundary remains the renderer's theme-aware contour and non-transparent frame.
-    #[cfg(any(target_os = "windows", target_os = "macos"))]
+    // Native elevation follows the window shape on macOS. On Windows, Tao enables
+    // an undecorated shadow that leaves an opaque native frame outside the rounded
+    // renderer surface at the corners, so shadow is disabled. Linux does not implement
+    // this API, so its boundary remains the renderer's theme-aware contour.
+    #[cfg(target_os = "macos")]
     let builder = builder.transparent(true).shadow(true);
+    #[cfg(target_os = "windows")]
+    let builder = builder.transparent(true).shadow(false);
     #[cfg(target_os = "linux")]
     let builder = builder.transparent(false).shadow(false);
     #[cfg(any(target_os = "windows", target_os = "macos", target_os = "linux"))]

src-tauri/tauri.windows.conf.json

@@ -10,7 +10,7 @@
         "minHeight": 640,
         "transparent": true,
         "decorations": false,
-        "shadow": true
+        "shadow": false
       }
     ]
   },

src/App.tsx

@@ -1222,7 +1222,7 @@ function App() {
   }, [autoAddClipboardLinks, coreReady, showKeychainModal]);
 
   return (
-    <div data-window-active={isWindowActive ? 'true' : 'false'} className={`app-shell flex h-screen w-screen overflow-hidden text-text-primary ${
+    <div data-window-active={isWindowActive ? 'true' : 'false'} className={`app-shell app-shell--style-${windowControlStyle} flex h-screen w-screen overflow-hidden text-text-primary ${
       isSidebarOnRight ? 'app-shell--sidebar-right' : 'app-shell--sidebar-left'
     } ${
       hasWindowChrome ? 'app-shell--window-chrome' : ''

src/index.css

@@ -27,8 +27,8 @@
   /* Keep this token alpha-free because some consumers apply their own /alpha. */
   --surface-overlay: 0 0% 100%;
   --shadow-color: 220 10% 20% / 0.1;
-  --window-frame-active: 220 12% 30% / 0.60;
-  --window-frame-inactive: 220 10% 30% / 0.18;
+  --window-frame-active: 220 12% 30% / 0.22;
+  --window-frame-inactive: 220 10% 30% / 0.08;
   --sidebar-shell-bg: 0 0% 92%;
   --sidebar-panel-bg: 0 0% 96%;
   --workspace-bg: 0 0% 98%;
@@ -75,8 +75,8 @@
   --properties-header-surface: hsl(var(--bg-modal));
   --surface-overlay: 0 0% 100%;
   --shadow-color: 220 10% 20% / 0.1;
-  --window-frame-active: 220 12% 30% / 0.60;
-  --window-frame-inactive: 220 10% 30% / 0.18;
+  --window-frame-active: 220 12% 30% / 0.22;
+  --window-frame-inactive: 220 10% 30% / 0.08;
   --sidebar-shell-bg: 0 0% 92%;
   --sidebar-panel-bg: 0 0% 96%;
   --workspace-bg: 0 0% 98%;
@@ -107,8 +107,8 @@
   --bg-input: 0 0% 16%;
   --properties-header-surface: hsl(0 0% 10%);
   --shadow-color: 0 0% 0% / 0.30;
-  --window-frame-active: 0 0% 100% / 0.35;
-  --window-frame-inactive: 0 0% 100% / 0.14;
+  --window-frame-active: 0 0% 100% / 0.14;
+  --window-frame-inactive: 0 0% 100% / 0.06;
   --status-completed: 136 62% 48%;
   --status-paused: 0 0% 56%;
   --status-downloading: 211 100% 56%;
@@ -156,8 +156,8 @@
   --bg-input: 231 15% 20%;
   --properties-header-surface: hsl(231 15% 17%);
   --shadow-color: 231 20% 8% / 0.35;
-  --window-frame-active: 228 14% 84% / 0.45;
-  --window-frame-inactive: 228 14% 84% / 0.18;
+  --window-frame-active: 228 14% 84% / 0.18;
+  --window-frame-inactive: 228 14% 84% / 0.08;
   --status-completed: 135 94% 65%;
   --status-paused: 65 92% 76%;
   --status-downloading: 191 97% 77%;
@@ -205,8 +205,8 @@
   --bg-input: 220 16% 24%;
   --properties-header-surface: hsl(220 16% 19%);
   --shadow-color: 220 25% 10% / 0.34;
-  --window-frame-active: 218 27% 88% / 0.45;
-  --window-frame-inactive: 218 27% 88% / 0.18;
+  --window-frame-active: 218 27% 88% / 0.18;
+  --window-frame-inactive: 218 27% 88% / 0.08;
   --status-completed: 92 28% 65%;
   --status-paused: 40 71% 73%;
   --status-downloading: 193 43% 67%;
@@ -2369,6 +2369,10 @@ html[data-list-density="relaxed"] {
     box-shadow: none;
   }
 
+  html[data-platform="macos"] :is(.app-shell, .properties-window-shell) {
+    border-width: 0.5px;
+  }
+
   @media (forced-colors: active) {
     .app-shell,
     .properties-window-shell {

src/main.tsx

@@ -14,6 +14,7 @@ import { error as logError, warn as logWarn, initLogger } from "./utils/logger";
 import { getCurrentWindow } from '@tauri-apps/api/window';
 import { invokeCommand as invoke } from './ipc';
 import { useWindowFocusState } from './utils/windowFocus';
+import './utils/platform';
 
 const isPropertiesWindow = getCurrentWindow().label.startsWith('properties-');
 

src/utils/platform.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest';
-import { shouldUseCustomWindowControls } from './platform';
+import { shouldUseCustomWindowControls, syncPlatformDataset } from './platform';
 
 describe('shouldUseCustomWindowControls', () => {
   it('keeps custom controls present while Windows/Linux detection is unresolved', () => {
@@ -20,3 +20,32 @@ describe('shouldUseCustomWindowControls', () => {
     expect(shouldUseCustomWindowControls('unknown', 'Mozilla/5.0 (Linux; Android 14; Mobile)')).toBe(false);
   });
 });
+
+describe('syncPlatformDataset', () => {
+  it('synchronizes known desktop platforms to document dataset', () => {
+    const mockDocument = { documentElement: { dataset: {} as Record<string, string | undefined> } };
+
+    syncPlatformDataset('macos', mockDocument);
+    expect(mockDocument.documentElement.dataset.platform).toBe('macos');
+
+    syncPlatformDataset('windows', mockDocument);
+    expect(mockDocument.documentElement.dataset.platform).toBe('windows');
+
+    syncPlatformDataset('linux', mockDocument);
+    expect(mockDocument.documentElement.dataset.platform).toBe('linux');
+  });
+
+  it('ignores unknown or unsupported platforms', () => {
+    const mockDocument = { documentElement: { dataset: { platform: 'macos' } } };
+
+    syncPlatformDataset('unknown', mockDocument);
+    expect(mockDocument.documentElement.dataset.platform).toBe('macos');
+
+    syncPlatformDataset('android', mockDocument);
+    expect(mockDocument.documentElement.dataset.platform).toBe('macos');
+  });
+
+  it('safely handles missing document in headless environments', () => {
+    expect(() => syncPlatformDataset('macos', undefined)).not.toThrow();
+  });
+});

src/utils/platform.ts

@@ -22,12 +22,39 @@ export const shouldUseCustomWindowControls = (os: string, userAgent: string): bo
 let cached: PlatformInfo | null = null;
 let pending: Promise<PlatformInfo> | null = null;
 
+type TargetDocument = {
+  documentElement: {
+    dataset: Record<string, string | undefined>;
+  };
+};
+
+export const syncPlatformDataset = (
+  os: string,
+  targetDocument: TargetDocument | undefined = typeof document !== 'undefined' ? document : undefined,
+): void => {
+  if (!targetDocument) return;
+  if (os === 'macos' || os === 'windows' || os === 'linux') {
+    targetDocument.documentElement.dataset.platform = os;
+  }
+};
+
+if (typeof document !== 'undefined' && typeof navigator !== 'undefined') {
+  if (/Macintosh|Mac OS X/i.test(navigator.userAgent)) {
+    syncPlatformDataset('macos');
+  } else if (/Windows/i.test(navigator.userAgent)) {
+    syncPlatformDataset('windows');
+  } else if (/Linux/i.test(navigator.userAgent)) {
+    syncPlatformDataset('linux');
+  }
+}
+
 export const getPlatformInfo = (): Promise<PlatformInfo> => {
   if (cached) return Promise.resolve(cached);
   if (!pending) {
     pending = invoke('get_platform_info')
       .then(info => {
         cached = info;
+        syncPlatformDataset(info.os);
         return info;
       })
       .finally(() => {

src/utils/windowConfiguration.test.ts

@@ -24,22 +24,25 @@ describe('main window configuration', () => {
     }
   });
 
-  it('uses native elevation where Tauri supports undecorated window shadows', () => {
-    for (const [platform, config] of [
-      ['macOS', macosConfiguration],
-      ['Windows', windowsConfiguration],
-    ] as const) {
-      expect(config.app.windows[0], platform).toMatchObject({
-        transparent: true,
-        decorations: false,
-        shadow: true,
-      });
-    }
+  it('uses native elevation on macOS where undecorated window shadows conform to the surface', () => {
+    expect(macosConfiguration.app.windows[0], 'macOS').toMatchObject({
+      transparent: true,
+      decorations: false,
+      shadow: true,
+    });
+  });
+
+  it('keeps Windows transparent without native shadow bleed outside rounded corners', () => {
+    expect(windowsConfiguration.app.windows[0], 'Windows').toMatchObject({
+      transparent: true,
+      decorations: false,
+      shadow: false,
+    });
   });
 
   it('keeps Linux on the renderer contour without claiming native shadow support', () => {
     const mainWindow = linuxConfiguration.app.windows[0];
-    expect(mainWindow).toMatchObject({
+    expect(mainWindow, 'Linux').toMatchObject({
       transparent: false,
       decorations: false,
       shadow: false,