fix(desktop): transparent WCO titlebar chrome on Windows/WSLg

Use a transparent native overlay so renderer chrome shows through the min/max/close
band. Sync window pre-paint bg to the computed chrome mix.

apps/desktop/electron/main.cjs

@@ -527,34 +527,30 @@ function getWindowBackgroundColor() {
   return nativeTheme.shouldUseDarkColors ? '#111111' : '#f7f7f7'
 }
 
+// Transparent WCO — renderer chrome shows through. rgba(0,0,0,0) can fall back
+// to GetFrameColor() on some Electron builds; rgba(1,0,0,0) is the escape hatch.
+const TITLEBAR_OVERLAY_COLOR = 'rgba(1, 0, 0, 0)'
+
 function getTitleBarOverlayOptions() {
   if (IS_MAC) {
     return { height: TITLEBAR_HEIGHT }
   }
 
-  // Window Controls Overlay: Windows paints it natively, and WSLg honors it too
-  // (it renders through a real compositor), so keep it enabled there — disabling
-  // it removes the min/max/close buttons entirely. Only plain (non-WSL) Linux,
-  // where some WMs/builds don't support WCO, falls through to no overlay; the
-  // frameless titleBarStyle 'hidden' still applies.
+  // Windows + WSLg paint WCO natively; plain Linux disables it (frameless hidden
+  // titlebar still applies).
   if (!IS_WINDOWS && !IS_WSL) {
     return false
   }
 
-  if (rendererTitleBarTheme) {
-    return {
-      color: rendererTitleBarTheme.background,
-      height: TITLEBAR_HEIGHT,
-      symbolColor: rendererTitleBarTheme.foreground
-    }
-  }
-
-  const useDarkColors = nativeTheme.shouldUseDarkColors
-
   return {
-    color: useDarkColors ? '#111111' : '#f7f7f7',
+    color: TITLEBAR_OVERLAY_COLOR,
     height: TITLEBAR_HEIGHT,
-    symbolColor: useDarkColors ? '#f7f7f7' : '#242424'
+    symbolColor:
+      rendererTitleBarTheme && isHexColor(rendererTitleBarTheme.foreground)
+        ? rendererTitleBarTheme.foreground
+        : nativeTheme.shouldUseDarkColors
+          ? '#f7f7f7'
+          : '#242424'
   }
 }
 

apps/desktop/src/app/shell/app-shell.tsx

@@ -189,6 +189,13 @@ export function AppShell({
         <TitlebarControls leftTools={leftTitlebarTools} onOpenSettings={onOpenSettings} tools={titlebarTools} />
       )}
 
+      {nativeOverlayWidth > 0 && (
+        <div
+          aria-hidden
+          className="pointer-events-none fixed inset-x-0 top-0 z-[4] h-(--titlebar-height) border-b border-(--ui-stroke-tertiary) bg-(--ui-chat-surface-background)"
+        />
+      )}
+
       <main className="relative z-3 flex min-h-0 w-full flex-1 flex-col overflow-hidden transition-none">
         <PaneShell className="min-h-0 flex-1">
           <div

apps/desktop/src/themes/context.tsx

@@ -157,6 +157,12 @@ function renderedModeFor(colors: DesktopThemeColors, mode: 'light' | 'dark'): 'l
 // Per-mode mix knobs. Light/dark fallbacks live in styles.css `:root` /
 // `:root.dark`; setting them inline keeps active-skin overrides surviving
 // the boot-time paint.
+// styles.css --theme-neutral-chrome — keep in sync.
+const NEUTRAL_CHROME = { light: '#f3f3f3', dark: '#0d0d0e' } as const
+
+const chromeBackground = (background: string, isDark: boolean) =>
+  mix(background, NEUTRAL_CHROME[isDark ? 'dark' : 'light'], isDark ? 0.26 : 0.08)
+
 const mixesFor = (isDark: boolean): Record<string, string> => ({
   '--theme-mix-chrome': isDark ? '74%' : '92%',
   '--theme-mix-sidebar': '100%',
@@ -222,8 +228,10 @@ function applyTheme(theme: DesktopTheme, mode: 'light' | 'dark') {
     root.style.setProperty(k, v)
   }
 
+  const chromeBg = chromeBackground(c.background, isDark)
+
   window.hermesDesktop?.setTitleBarTheme?.({
-    background: c.background,
+    background: chromeBg,
     foreground: c.foreground
   })
 
@@ -231,7 +239,7 @@ function applyTheme(theme: DesktopTheme, mode: 'light' | 'dark') {
   // they let a brand-new window paint the themed background on its very first
   // frame, before this module has even loaded.
   try {
-    window.localStorage.setItem('hermes-boot-background', c.background)
+    window.localStorage.setItem('hermes-boot-background', chromeBg)
     window.localStorage.setItem('hermes-boot-color-scheme', rendered)
   } catch {
     // Storage may be unavailable (private mode / quota); the inline script