diff --git a/packages/app/src/components/titlebar-padding.test.ts b/packages/app/src/components/titlebar-padding.test.ts
new file mode 100644
index 0000000000..1c0993cd0f
--- /dev/null
+++ b/packages/app/src/components/titlebar-padding.test.ts
@@ -0,0 +1,13 @@
+import { describe, expect, test } from "bun:test"
+import { macTitlebarLeftPadding } from "./titlebar-padding"
+
+describe("macOS titlebar padding", () => {
+  test("reserves traffic light space while windowed", () => {
+    expect(macTitlebarLeftPadding(1, false)).toBe("84px")
+    expect(macTitlebarLeftPadding(2, false)).toBe("42px")
+  })
+
+  test("does not reserve traffic light space in fullscreen", () => {
+    expect(macTitlebarLeftPadding(1, true)).toBe("0px")
+  })
+})
diff --git a/packages/app/src/components/titlebar-padding.ts b/packages/app/src/components/titlebar-padding.ts
new file mode 100644
index 0000000000..7334201055
--- /dev/null
+++ b/packages/app/src/components/titlebar-padding.ts
@@ -0,0 +1,6 @@
+const macTrafficLightsWidth = 84
+
+export function macTitlebarLeftPadding(zoom: number, fullscreen: boolean) {
+  if (fullscreen) return "0px"
+  return `${macTrafficLightsWidth / zoom}px`
+}
diff --git a/packages/app/src/components/titlebar.tsx b/packages/app/src/components/titlebar.tsx
index aa2f220e49..9cb286c6cb 100644
--- a/packages/app/src/components/titlebar.tsx
+++ b/packages/app/src/components/titlebar.tsx
@@ -29,6 +29,7 @@ import type { PromptSession } from "@/context/prompt"
 import "./titlebar.css"
 import { newTabTooltipKeybind } from "./command-tooltip-keybind"
 import { normalizeSessionInfo } from "@/utils/session"
+import { macTitlebarLeftPadding } from "./titlebar-padding"
 
 type TauriDesktopWindow = {
   startDragging?: () => Promise<void>
@@ -237,8 +238,8 @@ export function Titlebar(props: { update?: TitlebarUpdate; debugTools?: { visibl
       }}
       style={{
         "min-height": minHeight(),
-        // Keep native macOS traffic lights clear even when the desktop window is narrow.
-        "padding-left": mac() ? `${84 / zoom()}px` : 0,
+        // Keep visible native macOS traffic lights clear even when the desktop window is narrow.
+        "padding-left": mac() ? macTitlebarLeftPadding(zoom(), platform.windowFullscreen?.() ?? false) : 0,
         width: electronWindows() ? `env(titlebar-area-width, calc(100vw - ${windowsControlsWidth()}))` : undefined,
         "max-width": electronWindows()
           ? `env(titlebar-area-width, calc(100vw - ${windowsControlsWidth()}))`
diff --git a/packages/app/src/context/platform.tsx b/packages/app/src/context/platform.tsx
index cf343bfa7e..4c374961a3 100644
--- a/packages/app/src/context/platform.tsx
+++ b/packages/app/src/context/platform.tsx
@@ -97,6 +97,9 @@ type PlatformBase = {
   /** Webview zoom level (desktop only) */
   webviewZoom?: Accessor<number>
 
+  /** Whether the native desktop window is fullscreen */
+  windowFullscreen?: Accessor<boolean>
+
   /** Get whether native pinch/Ctrl-scroll zoom gestures are enabled (desktop only) */
   getPinchZoomEnabled?(): Promise<boolean> | boolean
 
diff --git a/packages/desktop/src/main/ipc.ts b/packages/desktop/src/main/ipc.ts
index 4563b688ac..5ecd4cb8c4 100644
--- a/packages/desktop/src/main/ipc.ts
+++ b/packages/desktop/src/main/ipc.ts
@@ -227,6 +227,11 @@ export function registerIpcHandlers(deps: Deps) {
     return win?.isFocused() ?? false
   })
 
+  ipcMain.handle("get-window-fullscreen", (event: IpcMainInvokeEvent) => {
+    const win = BrowserWindow.fromWebContents(event.sender)
+    return win?.isFullScreen() ?? false
+  })
+
   ipcMain.handle("set-window-focus", (event: IpcMainInvokeEvent) => {
     const win = BrowserWindow.fromWebContents(event.sender)
     win?.focus()
diff --git a/packages/desktop/src/main/windows.ts b/packages/desktop/src/main/windows.ts
index 7a594b5302..516d05e634 100644
--- a/packages/desktop/src/main/windows.ts
+++ b/packages/desktop/src/main/windows.ts
@@ -219,6 +219,7 @@ export function createMainWindow(id: string = randomUUID()) {
 
   state.manage(win)
   registerWindow(win, id)
+  wireFullscreen(win)
   loadWindow(win, "index.html")
   wireZoom(win)
 
@@ -472,6 +473,11 @@ function wireZoom(win: BrowserWindow) {
   })
 }
 
+function wireFullscreen(win: BrowserWindow) {
+  win.on("enter-full-screen", () => win.webContents.send("window-fullscreen-changed", true))
+  win.on("leave-full-screen", () => win.webContents.send("window-fullscreen-changed", false))
+}
+
 function clampZoom(value: number) {
   return Math.min(Math.max(value, minZoomLevel), maxZoomLevel)
 }
diff --git a/packages/desktop/src/preload/index.ts b/packages/desktop/src/preload/index.ts
index 87eac1fa80..1a0056dfe7 100644
--- a/packages/desktop/src/preload/index.ts
+++ b/packages/desktop/src/preload/index.ts
@@ -100,6 +100,12 @@ const api: ElectronAPI = {
   readClipboardImage: () => ipcRenderer.invoke("read-clipboard-image"),
   showNotification: (title, body) => ipcRenderer.send("show-notification", title, body),
   getWindowFocused: () => ipcRenderer.invoke("get-window-focused"),
+  getWindowFullscreen: () => ipcRenderer.invoke("get-window-fullscreen"),
+  onWindowFullscreenChanged: (cb) => {
+    const handler = (_: unknown, fullscreen: boolean) => cb(fullscreen)
+    ipcRenderer.on("window-fullscreen-changed", handler)
+    return () => ipcRenderer.removeListener("window-fullscreen-changed", handler)
+  },
   setWindowFocus: () => ipcRenderer.invoke("set-window-focus"),
   showWindow: () => ipcRenderer.invoke("show-window"),
   relaunch: () => ipcRenderer.send("relaunch"),
diff --git a/packages/desktop/src/preload/types.ts b/packages/desktop/src/preload/types.ts
index 5fbace72c7..ea201af63e 100644
--- a/packages/desktop/src/preload/types.ts
+++ b/packages/desktop/src/preload/types.ts
@@ -91,6 +91,8 @@ export type ElectronAPI = {
   readClipboardImage: () => Promise<{ buffer: ArrayBuffer; width: number; height: number } | null>
   showNotification: (title: string, body?: string) => void
   getWindowFocused: () => Promise<boolean>
+  getWindowFullscreen: () => Promise<boolean>
+  onWindowFullscreenChanged: (cb: (fullscreen: boolean) => void) => () => void
   setWindowFocus: () => Promise<void>
   showWindow: () => Promise<void>
   relaunch: () => void
diff --git a/packages/desktop/src/renderer/index.tsx b/packages/desktop/src/renderer/index.tsx
index b7d2d9a74d..fa4c7f325e 100644
--- a/packages/desktop/src/renderer/index.tsx
+++ b/packages/desktop/src/renderer/index.tsx
@@ -30,6 +30,10 @@ import "./styles.css"
 import { Splash } from "@opencode-ai/ui/logo"
 import { useTheme } from "@opencode-ai/ui/theme/context"
 
+const [windowFullscreen, setWindowFullscreen] = createSignal(false)
+window.api.onWindowFullscreenChanged(setWindowFullscreen)
+void window.api.getWindowFullscreen().then(setWindowFullscreen)
+
 const root = document.getElementById("root")
 if (import.meta.env.DEV && !(root instanceof HTMLElement)) {
   throw new Error(t("error.dev.rootNotFound"))
@@ -294,6 +298,8 @@ const createPlatform = (windowState: DesktopWindowState): Platform => {
 
     webviewZoom,
 
+    windowFullscreen,
+
     getPinchZoomEnabled: () => window.api.getPinchZoomEnabled(),
 
     setPinchZoomEnabled,