diff --git a/src/renderer/src/app-shell/TitlebarLeftControls.tsx b/src/renderer/src/app-shell/TitlebarLeftControls.tsx
index 352e3d121fba..1ef2affdaae8 100644
--- a/src/renderer/src/app-shell/TitlebarLeftControls.tsx
+++ b/src/renderer/src/app-shell/TitlebarLeftControls.tsx
@@ -15,6 +15,7 @@ import {
 } from '@/store/slices/worktree-nav-history'
 import { useShortcutLabel } from '../hooks/useShortcutLabel'
 import { useAppStore } from '../store'
+import { macTrafficLightChromeForWindow } from '@/lib/desktop-window-chrome'
 import { hasCustomTitleBar, isMac } from './app-window-chrome'
 import type { AppChromeLayout } from './use-app-chrome-layout'
 
@@ -42,7 +43,10 @@ export function TitlebarLeftControls({ layout }: { layout: AppChromeLayout }): R
       }`}
     >
       <div className="flex h-full items-center">
-        {isMac && !layout.isFullScreen ? (
+        {macTrafficLightChromeForWindow({
+          isMac,
+          isFullScreen: layout.isFullScreen
+        }).showPad ? (
           <div className="titlebar-traffic-light-pad" />
         ) : hasCustomTitleBar ? (
           /* Why: Windows/Linux remove the native title bar, so render the logo plus a ··· button that pops the application menu (as Alt does). */
diff --git a/src/renderer/src/app-shell/app-window-chrome.ts b/src/renderer/src/app-shell/app-window-chrome.ts
index 8305650c4d03..23c4faa3e97c 100644
--- a/src/renderer/src/app-shell/app-window-chrome.ts
+++ b/src/renderer/src/app-shell/app-window-chrome.ts
@@ -1,5 +1,6 @@
 import {
   isPairedWebClientWindow,
+  macTrafficLightChromeForWindow,
   shouldRenderDesktopWindowChrome
 } from '@/lib/desktop-window-chrome'
 
@@ -19,4 +20,8 @@ export const WINDOW_CONTROLS_HEIGHT = hasCustomTitleBar ? '36px' : '0px'
 
 // Why: macOS paints traffic lights on the window's top-left edge. Windows and Linux paint their
 // controls on the right, so only macOS needs a surface to keep the left edge uncovered.
-export const MAC_TRAFFIC_LIGHTS_WIDTH = isMac ? '80px' : '0px'
+// A paired web client on a Mac has no traffic lights (#19299).
+export const MAC_TRAFFIC_LIGHTS_WIDTH = macTrafficLightChromeForWindow({
+  isMac,
+  isFullScreen: false
+}).width
diff --git a/src/renderer/src/lib/desktop-window-chrome.test.ts b/src/renderer/src/lib/desktop-window-chrome.test.ts
index a4bde1495ddd..afe25ade04ab 100644
--- a/src/renderer/src/lib/desktop-window-chrome.test.ts
+++ b/src/renderer/src/lib/desktop-window-chrome.test.ts
@@ -1,5 +1,14 @@
-import { describe, expect, it } from 'vitest'
-import { shouldRenderDesktopWindowChrome } from './desktop-window-chrome'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import {
+  macTrafficLightChromeForWindow,
+  macTrafficLightsWidth,
+  shouldRenderDesktopWindowChrome,
+  shouldShowMacTrafficLightPad
+} from './desktop-window-chrome'
+
+afterEach(() => {
+  vi.unstubAllGlobals()
+})
 
 describe('shouldRenderDesktopWindowChrome', () => {
   it('renders custom chrome for frameless desktop Linux and Windows windows', () => {
@@ -16,3 +25,46 @@ describe('shouldRenderDesktopWindowChrome', () => {
     expect(shouldRenderDesktopWindowChrome({ platform: 'win32', isWebClient: true })).toBe(false)
   })
 })
+
+describe('mac traffic-light inset', () => {
+  it('reserves the inset on desktop macOS, including while fullscreen hides the pad', () => {
+    expect(macTrafficLightsWidth({ isMac: true, isWebClient: false })).toBe('80px')
+    expect(
+      shouldShowMacTrafficLightPad({ isMac: true, isWebClient: false, isFullScreen: false })
+    ).toBe(true)
+    expect(
+      shouldShowMacTrafficLightPad({ isMac: true, isWebClient: false, isFullScreen: true })
+    ).toBe(false)
+  })
+
+  it('does not reserve a traffic-light inset in the paired web client on a Mac', () => {
+    expect(macTrafficLightsWidth({ isMac: true, isWebClient: true })).toBe('0px')
+    expect(
+      shouldShowMacTrafficLightPad({ isMac: true, isWebClient: true, isFullScreen: false })
+    ).toBe(false)
+    expect(
+      shouldShowMacTrafficLightPad({ isMac: true, isWebClient: true, isFullScreen: true })
+    ).toBe(false)
+  })
+
+  it('reads the paired web flag for both the inset width and the pad', () => {
+    vi.stubGlobal('__ORCA_WEB_CLIENT__', true)
+    expect(macTrafficLightChromeForWindow({ isMac: true, isFullScreen: false })).toEqual({
+      width: '0px',
+      showPad: false
+    })
+
+    vi.stubGlobal('__ORCA_WEB_CLIENT__', false)
+    expect(macTrafficLightChromeForWindow({ isMac: true, isFullScreen: false })).toEqual({
+      width: '80px',
+      showPad: true
+    })
+  })
+
+  it('does not reserve a traffic-light inset on Windows or Linux', () => {
+    expect(macTrafficLightsWidth({ isMac: false, isWebClient: false })).toBe('0px')
+    expect(
+      shouldShowMacTrafficLightPad({ isMac: false, isWebClient: false, isFullScreen: false })
+    ).toBe(false)
+  })
+})
diff --git a/src/renderer/src/lib/desktop-window-chrome.ts b/src/renderer/src/lib/desktop-window-chrome.ts
index 59683f155185..affa660c1378 100644
--- a/src/renderer/src/lib/desktop-window-chrome.ts
+++ b/src/renderer/src/lib/desktop-window-chrome.ts
@@ -21,3 +21,39 @@ export function shouldRenderDesktopWindowChrome({
 }: DesktopWindowChromeInput): boolean {
   return !isWebClient && (platform === 'win32' || platform === 'linux')
 }
+
+/** Desktop macOS keeps the left inset for native traffic lights. A paired browser has none. */
+export function macTrafficLightsWidth(input: {
+  isMac: boolean
+  isWebClient: boolean
+}): '80px' | '0px' {
+  return input.isMac && !input.isWebClient ? '80px' : '0px'
+}
+
+/** The pad element is hidden in fullscreen; the width token above stays, matching desktop today. */
+export function shouldShowMacTrafficLightPad(input: {
+  isMac: boolean
+  isWebClient: boolean
+  isFullScreen: boolean
+}): boolean {
+  return input.isMac && !input.isWebClient && !input.isFullScreen
+}
+
+/**
+ * One read of the paired-web flag feeds both the width token and the pad.
+ * Call sites that pass `isWebClient` themselves can drift apart.
+ */
+export function macTrafficLightChromeForWindow(input: { isMac: boolean; isFullScreen: boolean }): {
+  width: '80px' | '0px'
+  showPad: boolean
+} {
+  const isWebClient = isPairedWebClientWindow()
+  return {
+    width: macTrafficLightsWidth({ isMac: input.isMac, isWebClient }),
+    showPad: shouldShowMacTrafficLightPad({
+      isMac: input.isMac,
+      isWebClient,
+      isFullScreen: input.isFullScreen
+    })
+  }
+}