diff --git a/electron/common-const.test.cjs b/electron/common-const.test.cjs
new file mode 100644
index 0000000000..39e594f7da
--- /dev/null
+++ b/electron/common-const.test.cjs
@@ -0,0 +1,62 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const path = require('node:path');
+
+require('ts-node/register/transpile-only');
+
+const {
+  isGnomeDesktopEnv,
+  isWaylandEnv,
+  isGnomeWaylandEnv,
+} = require(path.resolve(__dirname, 'common.const.ts'));
+
+test('isGnomeDesktopEnv: detects GNOME from desktop env vars', () => {
+  assert.equal(isGnomeDesktopEnv('linux', { XDG_CURRENT_DESKTOP: 'GNOME' }), true);
+  assert.equal(isGnomeDesktopEnv('linux', { XDG_CURRENT_DESKTOP: 'ubuntu:GNOME' }), true);
+  assert.equal(isGnomeDesktopEnv('linux', { DESKTOP_SESSION: 'ubuntu' }), true);
+  assert.equal(isGnomeDesktopEnv('linux', { XDG_SESSION_DESKTOP: 'gnome' }), true);
+});
+
+test('isGnomeDesktopEnv: false for non-GNOME / non-linux', () => {
+  assert.equal(isGnomeDesktopEnv('linux', { XDG_CURRENT_DESKTOP: 'KDE' }), false);
+  assert.equal(isGnomeDesktopEnv('linux', {}), false);
+  // env vars are present but platform is not linux
+  assert.equal(isGnomeDesktopEnv('win32', { XDG_CURRENT_DESKTOP: 'GNOME' }), false);
+  assert.equal(isGnomeDesktopEnv('darwin', { XDG_CURRENT_DESKTOP: 'GNOME' }), false);
+});
+
+test('isWaylandEnv: detects Wayland via session type or display', () => {
+  assert.equal(isWaylandEnv('linux', { XDG_SESSION_TYPE: 'wayland' }), true);
+  // some sessions only set WAYLAND_DISPLAY
+  assert.equal(isWaylandEnv('linux', { WAYLAND_DISPLAY: 'wayland-0' }), true);
+});
+
+test('isWaylandEnv: false for X11 / non-linux', () => {
+  assert.equal(isWaylandEnv('linux', { XDG_SESSION_TYPE: 'x11' }), false);
+  assert.equal(isWaylandEnv('linux', {}), false);
+  assert.equal(isWaylandEnv('win32', { WAYLAND_DISPLAY: 'wayland-0' }), false);
+});
+
+test('isGnomeWaylandEnv: only true for GNOME AND Wayland together', () => {
+  // GNOME + Wayland -> the one combination the kill-switch targets
+  assert.equal(
+    isGnomeWaylandEnv('linux', {
+      XDG_CURRENT_DESKTOP: 'GNOME',
+      XDG_SESSION_TYPE: 'wayland',
+    }),
+    true,
+  );
+  // GNOME on X11 keeps the feature
+  assert.equal(
+    isGnomeWaylandEnv('linux', {
+      XDG_CURRENT_DESKTOP: 'GNOME',
+      XDG_SESSION_TYPE: 'x11',
+    }),
+    false,
+  );
+  // non-GNOME Wayland (e.g. KDE) is unaffected
+  assert.equal(
+    isGnomeWaylandEnv('linux', { XDG_CURRENT_DESKTOP: 'KDE', XDG_SESSION_TYPE: 'wayland' }),
+    false,
+  );
+});
diff --git a/electron/common.const.ts b/electron/common.const.ts
index 9ed099ab72..4098fc3ca1 100644
--- a/electron/common.const.ts
+++ b/electron/common.const.ts
@@ -1,12 +1,35 @@
-export const IS_MAC = process.platform === 'darwin';
-export const IS_GNOME_DESKTOP =
-  process.platform === 'linux' &&
+export const isGnomeDesktopEnv = (
+  platform: NodeJS.Platform,
+  env: NodeJS.ProcessEnv,
+): boolean =>
+  platform === 'linux' &&
   [
-    process.env.XDG_CURRENT_DESKTOP,
-    process.env.XDG_SESSION_DESKTOP,
-    process.env.DESKTOP_SESSION,
-    process.env.GNOME_SHELL_SESSION_MODE,
+    env.XDG_CURRENT_DESKTOP,
+    env.XDG_SESSION_DESKTOP,
+    env.DESKTOP_SESSION,
+    env.GNOME_SHELL_SESSION_MODE,
   ]
     .filter((v): v is string => !!v)
     .map((v) => v.toLowerCase())
     .some((v) => v.includes('gnome') || v.includes('ubuntu'));
+
+// Some sessions only set WAYLAND_DISPLAY and leave XDG_SESSION_TYPE unset, so
+// check both.
+export const isWaylandEnv = (
+  platform: NodeJS.Platform,
+  env: NodeJS.ProcessEnv,
+): boolean =>
+  platform === 'linux' && (env.XDG_SESSION_TYPE === 'wayland' || !!env.WAYLAND_DISPLAY);
+
+// Only GNOME on Wayland reliably fails to render the Window-Controls-Overlay
+// when titleBarStyle is 'hidden', stranding the window with no min/max/close
+// controls. The custom-title-bar kill-switch is narrowed to this combination
+// so GNOME-on-X11 (where the feature works) keeps it.
+export const isGnomeWaylandEnv = (
+  platform: NodeJS.Platform,
+  env: NodeJS.ProcessEnv,
+): boolean => isGnomeDesktopEnv(platform, env) && isWaylandEnv(platform, env);
+
+export const IS_MAC = process.platform === 'darwin';
+export const IS_GNOME_DESKTOP = isGnomeDesktopEnv(process.platform, process.env);
+export const IS_GNOME_WAYLAND = isGnomeWaylandEnv(process.platform, process.env);
diff --git a/electron/electronAPI.d.ts b/electron/electronAPI.d.ts
index 92d83067dd..5053798c19 100644
--- a/electron/electronAPI.d.ts
+++ b/electron/electronAPI.d.ts
@@ -136,6 +136,8 @@ export interface ElectronAPI {
 
   isGnomeDesktop(): boolean;
 
+  isGnomeWayland(): boolean;
+
   isMacOS(): boolean;
 
   isAppleSilicon(): boolean;
diff --git a/electron/main-window.ts b/electron/main-window.ts
index 5bfcb5cedd..c32ec6f057 100644
--- a/electron/main-window.ts
+++ b/electron/main-window.ts
@@ -16,7 +16,7 @@ import { IPC } from './shared-with-frontend/ipc-events.const';
 import { isExternalUrlSchemeAllowed } from './shared-with-frontend/is-external-url-allowed';
 import { readFileSync, stat, writeFileSync } from 'fs';
 import { error, log } from 'electron-log/main';
-import { IS_MAC, IS_GNOME_DESKTOP } from './common.const';
+import { IS_MAC, IS_GNOME_WAYLAND } from './common.const';
 import {
   destroyTaskWidget,
   getIsTaskWidgetAlwaysShow,
@@ -148,10 +148,12 @@ export const createWindow = async ({
   const userPrefersCustomWindowTitleBar =
     persistedIsUseCustomWindowTitleBar ??
     legacyIsUseObsidianStyleHeader ??
-    !IS_GNOME_DESKTOP;
-  // GNOME + Wayland combinations can miss native controls when titleBarStyle is hidden.
-  // Force native decorations on GNOME to keep window controls available.
-  const isUseCustomWindowTitleBar = IS_GNOME_DESKTOP
+    !IS_GNOME_WAYLAND;
+  // GNOME + Wayland can't render the Window-Controls-Overlay when titleBarStyle
+  // is 'hidden', leaving the window with no min/max/close controls. Force native
+  // decorations only for that combination; GNOME-on-X11 and every other desktop
+  // honor the user's preference. Keep in sync with global-theme.service.ts.
+  const isUseCustomWindowTitleBar = IS_GNOME_WAYLAND
     ? false
     : userPrefersCustomWindowTitleBar;
   // On macOS use 'hiddenInset' so AppKit positions the traffic lights at the
diff --git a/electron/preload.ts b/electron/preload.ts
index f5b3ca4245..b034803142 100644
--- a/electron/preload.ts
+++ b/electron/preload.ts
@@ -6,6 +6,7 @@ import {
   webUtils,
 } from 'electron';
 import { ElectronAPI } from './electronAPI.d';
+import { IS_GNOME_DESKTOP, IS_GNOME_WAYLAND } from './common.const';
 import { IPC, IPCEventValue } from './shared-with-frontend/ipc-events.const';
 import {
   getDistChannel,
@@ -30,25 +31,6 @@ const _invoke: (channel: IPCEventValue, ...args: unknown[]) => Promise<unknown>
   ...args
 ) => ipcRenderer.invoke(channel, ...args);
 
-const isGnomeDesktop = (): boolean => {
-  if (process.platform !== 'linux') {
-    return false;
-  }
-
-  const desktopValues = [
-    process.env.XDG_CURRENT_DESKTOP,
-    process.env.XDG_SESSION_DESKTOP,
-    process.env.DESKTOP_SESSION,
-    process.env.GNOME_SHELL_SESSION_MODE,
-  ]
-    .filter((value): value is string => !!value)
-    .map((value) => value.toLowerCase());
-
-  return desktopValues.some(
-    (value) => value.includes('gnome') || value.includes('ubuntu'),
-  );
-};
-
 const ea: ElectronAPI = {
   on: (
     channel: string,
@@ -108,7 +90,8 @@ const ea: ElectronAPI = {
   },
   getZoomFactor: () => webFrame.getZoomFactor(),
   isLinux: () => process.platform === 'linux',
-  isGnomeDesktop,
+  isGnomeDesktop: () => IS_GNOME_DESKTOP,
+  isGnomeWayland: () => IS_GNOME_WAYLAND,
   isMacOS: () => process.platform === 'darwin',
   isAppleSilicon: () => process.platform === 'darwin' && process.arch === 'arm64',
   isSnap: () => process && process.env && !!process.env.SNAP,
diff --git a/src/app/app.constants.ts b/src/app/app.constants.ts
index 71c32e6361..5edb011be5 100644
--- a/src/app/app.constants.ts
+++ b/src/app/app.constants.ts
@@ -14,7 +14,11 @@ export const IS_ELECTRON_TOKEN = new InjectionToken<boolean>('IS_ELECTRON', {
 });
 // effectively IS_BROWSER
 export const IS_WEB_BROWSER = !IS_ELECTRON && !IS_ANDROID_WEB_VIEW;
-export const IS_GNOME_DESKTOP = IS_ELECTRON && window.ea.isGnomeDesktop();
+// Only GNOME+Wayland force-disables the custom title bar (the Window-Controls-
+// Overlay won't render there). Mirrors electron/common.const.ts so the renderer
+// and main process agree. See global-theme.service.ts / main-window.ts.
+// (window.ea.isGnomeDesktop() still exists on the bridge for plugin use.)
+export const IS_GNOME_WAYLAND = IS_ELECTRON && window.ea.isGnomeWayland();
 // True only inside the Electron build — preload exposes process.arch.
 // Web builds can't reliably distinguish Apple Silicon from Intel and stay false.
 export const IS_APPLE_SILICON = IS_ELECTRON && window.ea.isAppleSilicon();
diff --git a/src/app/core/theme/global-theme.service.ts b/src/app/core/theme/global-theme.service.ts
index 4e18df762d..faca61ff11 100644
--- a/src/app/core/theme/global-theme.service.ts
+++ b/src/app/core/theme/global-theme.service.ts
@@ -9,7 +9,7 @@ import {
   untracked,
 } from '@angular/core';
 import { takeUntilDestroyed, toObservable, toSignal } from '@angular/core/rxjs-interop';
-import { BodyClass, IS_ELECTRON, IS_GNOME_DESKTOP } from '../../app.constants';
+import { BodyClass, IS_ELECTRON, IS_GNOME_WAYLAND } from '../../app.constants';
 import { IS_MAC } from '../../util/is-mac';
 import { distinctUntilChanged, map, startWith, switchMap, take } from 'rxjs/operators';
 import { IS_TOUCH_ONLY } from '../../util/is-touch-only';
@@ -93,8 +93,22 @@ export class GlobalThemeService {
   private _iosViewportChangeRaf: number | null = null;
 
   private _isCustomWindowTitleBarEnabled(): boolean {
+    // The main process (main-window.ts) force-disables the custom title bar on
+    // GNOME+Wayland because the Window-Controls-Overlay won't render there.
+    // Mirror that here so we never lay the custom header on top of native
+    // decorations, which would produce a doubled header.
+    if (IS_GNOME_WAYLAND) {
+      return false;
+    }
+    // Default ON to match main-window's `?? !IS_GNOME_WAYLAND` default.
+    // KNOWN RESIDUAL: main-window also honors the legacy `isUseObsidianStyleHeader`
+    // SimpleStore field, which is never mirrored into global config, so it isn't
+    // visible here. A user who explicitly disabled the *old* header and never set
+    // the new toggle gets native decorations + custom header (doubled). This is a
+    // pre-existing divergence (already present for non-GNOME) and is self-healing:
+    // the now-visible Misc toggle lets them turn the custom header off.
     const misc = this._globalConfigService.misc();
-    return misc?.isUseCustomWindowTitleBar ?? !IS_GNOME_DESKTOP;
+    return misc?.isUseCustomWindowTitleBar ?? true;
   }
 
   darkMode = signal<DarkModeCfg>(
diff --git a/src/app/features/config/default-global-config.const.ts b/src/app/features/config/default-global-config.const.ts
index 7faf15a3e2..331ddd550a 100644
--- a/src/app/features/config/default-global-config.const.ts
+++ b/src/app/features/config/default-global-config.const.ts
@@ -63,8 +63,9 @@ export const DEFAULT_GLOBAL_CONFIG: GlobalConfigState = {
     // NOTE: isUseCustomWindowTitleBar is intentionally NOT defaulted here. A
     // persisted default would be pushed to Electron on every launch and override
     // a legacy `isUseObsidianStyleHeader` choice. Its effective default is resolved
-    // at read time (main-window.ts / global-theme.service.ts: `?? !IS_GNOME_DESKTOP`)
-    // and the settings checkbox is seeded display-only in misc-settings-form (#7891).
+    // at read time (main-window.ts / global-theme.service.ts: defaults on, forced
+    // off only on GNOME+Wayland) and the settings checkbox is seeded display-only
+    // in misc-settings-form (#7891).
     isShowProductivityTipLonger: false,
     customTheme: 'default',
     defaultStartPage: 0,
diff --git a/src/app/features/config/form-cfgs/misc-settings-form.const.ts b/src/app/features/config/form-cfgs/misc-settings-form.const.ts
index acbfe38ca5..b94d9ea060 100644
--- a/src/app/features/config/form-cfgs/misc-settings-form.const.ts
+++ b/src/app/features/config/form-cfgs/misc-settings-form.const.ts
@@ -4,7 +4,7 @@ import {
   MiscConfig,
 } from '../global-config.model';
 import { T } from '../../../t.const';
-import { IS_ELECTRON, IS_GNOME_DESKTOP } from '../../../app.constants';
+import { IS_ELECTRON, IS_GNOME_WAYLAND } from '../../../app.constants';
 import { isValidSplitTime } from '../../../util/is-valid-split-time';
 
 export const MISC_SETTINGS_FORM_CFG: ConfigFormSection<MiscConfig> = {
@@ -102,21 +102,21 @@ export const MISC_SETTINGS_FORM_CFG: ConfigFormSection<MiscConfig> = {
         label: T.GCF.MISC.IS_TRAY_SHOW_CURRENT_COUNTDOWN,
       },
     },
-    ...((IS_ELECTRON && !IS_GNOME_DESKTOP
+    ...((IS_ELECTRON && !IS_GNOME_WAYLAND
       ? [
           {
             key: 'isUseCustomWindowTitleBar',
             type: 'checkbox',
             // Display-only default: seed the checkbox so it reflects the actual
             // window state on a fresh install (the custom title bar is on by
-            // default here -- this field is only shown on non-GNOME Electron, see
-            // the enclosing guard). formly seeds the control without an initial
-            // modelChange, so nothing is persisted on load.
+            // default here -- this field is hidden only on GNOME+Wayland, where the
+            // main process force-disables it, see the enclosing guard). formly seeds
+            // the control without an initial modelChange, so nothing is persisted on load.
             // KNOWN RESIDUAL (#7891): saving any *other* Misc setting emits the
             // whole model and persists this seeded value too. We accept that over a
             // persisted DEFAULT_GLOBAL_CONFIG default, which would be pushed to
             // Electron on *every* launch and override a legacy `isUseObsidianStyleHeader`
-            // choice. So a pre-2025-12 non-GNOME user who had disabled the old
+            // choice. So a pre-2025-12 user who had disabled the old
             // header may see it re-enabled after editing Misc settings (reversible here).
             defaultValue: true,
             templateOptions: {