diff --git a/electron/main/index.ts b/electron/main/index.ts
index 858f80c..7dcd85d 100644
--- a/electron/main/index.ts
+++ b/electron/main/index.ts
@@ -1,4 +1,4 @@
-import { app, BrowserWindow, dialog, ipcMain, session } from 'electron'
+import { app, BrowserWindow, dialog, ipcMain, session, systemPreferences } from 'electron'
 import type { IpcMainInvokeEvent } from 'electron'
 import { mkdir, readFile, writeFile } from 'node:fs/promises'
 import { execFile } from 'node:child_process'
@@ -227,6 +227,32 @@ async function pickOpenPath(): Promise<PickResult> {
 }
 
 function registerIpcHandlers(): void {
+  /*
+   * `titleBarStyle: 'hiddenInset'` gives the renderer the drag region
+   * (`-webkit-app-region: drag` on the TopBar, see TopBar.module.css) but
+   * NOT the OS's usual double-click-to-zoom behaviour that a real title
+   * bar has for free — Chromium's drag region is a plain mouse listener,
+   * not an NSWindow title bar, so nothing tells macOS to react to the
+   * second click. The renderer's own dblclick handler calls this so we
+   * can honour the user's actual System Settings > Desktop & Dock choice
+   * ("Zoom", "Minimize" or "None") instead of hardcoding one.
+   */
+  ipcMain.handle('window:titlebarDoubleClick', (evt) => {
+    if (process.platform !== 'darwin') return
+    const win = BrowserWindow.fromWebContents(evt.sender)
+    if (!win) return
+    const action = systemPreferences.getUserDefault('AppleActionOnDoubleClick', 'string')
+    if (action === 'Minimize') {
+      win.minimize()
+    } else if (action === 'None') {
+      // no-op, matches the system setting
+    } else {
+      // Default action ('Maximize', or unset) mirrors a native title bar.
+      if (win.isMaximized()) win.unmaximize()
+      else win.maximize()
+    }
+  })
+
   ipcMain.handle('dialog:save', async (evt, defaultName: string) => {
     /*
      * Parent the modal to the window that MADE the call, not to whatever
diff --git a/electron/preload/index.ts b/electron/preload/index.ts
index 4bba3fc..eff60b6 100644
--- a/electron/preload/index.ts
+++ b/electron/preload/index.ts
@@ -268,7 +268,9 @@ const api = {
   window: {
     /** Represented file + edited flag: macOS proxy icon and title-bar dot. */
     setDocument: (p: { path: string | null; edited: boolean }): void =>
-      ipcRenderer.send('window:document', p)
+      ipcRenderer.send('window:document', p),
+    titlebarDoubleClick: (): Promise<void> =>
+      ipcRenderer.invoke('window:titlebarDoubleClick')
   },
   /** Errors the main process caught instead of dying from. */
   onMainError: (cb: (msg: string) => void): (() => void) => onChannel('app:main-error', cb),
diff --git a/src/components/layout/TopBar.module.css b/src/components/layout/TopBar.module.css
index f53debd..aefa754 100644
--- a/src/components/layout/TopBar.module.css
+++ b/src/components/layout/TopBar.module.css
@@ -22,6 +22,16 @@
    */
   position: relative;
   z-index: var(--dp-z-chrome, 20);
+  -webkit-app-region: drag;
+}
+
+.root button,
+.root input,
+.root select,
+.root a,
+.root [role='tab'],
+.root [role='option'] {
+  -webkit-app-region: no-drag;
 }
 
 .left {
diff --git a/src/components/layout/TopBar.tsx b/src/components/layout/TopBar.tsx
index 351fa1c..a11900d 100644
--- a/src/components/layout/TopBar.tsx
+++ b/src/components/layout/TopBar.tsx
@@ -230,8 +230,22 @@ export function TopBar() {
   const [verificationOpen, setVerificationOpen] = useState(false)
   const [testKind, setTestKind] = useState<NodeKind | null>(null)
 
+  /*
+   * The drag region (`-webkit-app-region: drag` in TopBar.module.css)
+   * substitutes for the title bar `hiddenInset` removes, but it's just a
+   * mouse listener to Chromium — macOS never learns to zoom the window on
+   * a second click there the way it would for a real NSWindow title bar.
+   * Skip it entirely over interactive descendants so double-clicking a
+   * button/tab doesn't ALSO toggle the window size.
+   */
+  const onRootDoubleClick = (e: React.MouseEvent): void => {
+    const target = e.target as HTMLElement
+    if (target.closest('button, input, select, a, [role="tab"], [role="option"]')) return
+    void window.daisy.window.titlebarDoubleClick()
+  }
+
   return (
-    <div className={styles.root}>
+    <div className={styles.root} onDoubleClick={onRootDoubleClick}>
       <div className={styles.left}>
         <span className={styles.dot} aria-hidden />
         <span className={styles.wordmark}>DAISYPATCHER</span>