diff --git a/app/engine.js b/app/engine.js
index 0e2f2cf..b23fa2b 100644
--- a/app/engine.js
+++ b/app/engine.js
@@ -2983,14 +2983,26 @@ async function downloadUpdate() {
   try {
     const r = await window.engineHost.updateDownload(updFound.asset.url, updFound.asset.name);
     if (!r.ok) { $('updProgress').textContent = r.error || 'Download failed.'; btn.disabled = false; return; }
-    $('updProgress').textContent = 'Saved to Downloads.';
-    /* Say what is left to do. Nothing installs itself here on purpose — see
-       the note on the main-process side. */
-    $('updWhat').textContent = 'Downloaded ' + updFound.tag + ' (' + fmtMB(r.bytes) + '). ' +
-      'Quit Church Translate, open the disk image, and drag the app over the one in ' +
-      'Applications. Your settings, models and voices are untouched.';
-    log('update ' + updFound.tag + ' downloaded to ' + r.path, 'ok');
-    try { await window.engineHost.updateReveal(r.path); } catch (_) {}
+      $('updProgress').textContent = 'Downloaded. Installing\u2026';
+      log('update ' + updFound.tag + ' downloaded to ' + r.path, 'ok');
+
+      /*
+       * Straight into the install. The app quits, a helper swaps the bundle and
+       * reopens it — so from here the window closing IS the update working, and
+       * saying so before it happens stops that looking like a crash.
+       */
+      $('updWhat').textContent = 'Installing ' + updFound.tag + '. Church Translate will close and ' +
+        'reopen by itself in a few seconds. Your settings, models and voices are untouched.';
+      const ins = await window.engineHost.updateInstall(r.path);
+      if (!ins || !ins.ok) {
+        /* Still useful: the file is downloaded, so fall back to the manual route
+           rather than leaving them with nothing. */
+        $('updProgress').textContent = (ins && ins.error) || 'Could not install.';
+        $('updWhat').textContent = 'Downloaded, but it could not install itself. Quit Church ' +
+          'Translate, open the disk image in Downloads, and drag the app over the one in Applications.';
+        try { await window.engineHost.updateReveal(r.path); } catch (_) {}
+        btn.disabled = false;
+      }
   } catch (e) {
     $('updProgress').textContent = 'Download failed: ' + e.message;
     btn.disabled = false;
diff --git a/app/index.html b/app/index.html
index 8266e8a..50625c0 100644
--- a/app/index.html
+++ b/app/index.html
@@ -391,7 +391,7 @@
           <div id="updFound" hidden>
             <p class="hint" id="updWhat"></p>
             <div class="row">
-              <button class="btn" id="updGet">Download it</button>
+              <button class="btn" id="updGet">Download and install</button>
               <span class="hint" id="updProgress"></span>
             </div>
             <details id="updNotesBox"><summary class="hint">What changed</summary>
diff --git a/app/main.js b/app/main.js
index e9dc8da..701849b 100644
--- a/app/main.js
+++ b/app/main.js
@@ -2259,6 +2259,97 @@ ipcMain.handle('update:download', async (_e, url, name) => {
   });
 });
 
+/*
+ * ─────────────────────────── installing it, in place ──────────────────────
+ *
+ * An app cannot replace itself while it is running, so the swap is done by a
+ * small script that outlives us: it waits for this process to exit, moves the
+ * old bundle aside, copies the new one in, and relaunches.
+ *
+ * MOVED ASIDE, NOT DELETED. If the copy fails half way — a full disk, a bad
+ * download, the volume going away — the old app is put straight back and
+ * relaunched. The failure mode this is written against is a campus Mac with no
+ * working app and a service in an hour, which is far worse than not updating.
+ *
+ * No sudo: /Applications is admin-writable on macOS and the bundle belongs to
+ * the operator, so nothing here needs a password. If that is ever not true the
+ * copy fails, the old app comes back, and the log says so.
+ */
+ipcMain.handle('update:install', async (_e, dmgPath) => {
+  const dmg = String(dmgPath || '');
+  if (!dmg || !fs.existsSync(dmg)) return { ok: false, error: 'That installer is no longer on disk.' };
+
+  /* Never mid-service. Quitting the app stops every listener's captions, and an
+     update is never worth that — the operator stops translation first. */
+  if (engineIsLive) {
+    return { ok: false, error: 'Translation is live. Press Stop translating first, then install.' };
+  }
+
+  const appPath = app.getPath('exe').replace(/\/Contents\/MacOS\/[^/]+$/, '');
+  if (!/\.app$/.test(appPath)) {
+    return { ok: false, error: 'This copy is not running from an .app bundle, so it cannot replace itself.' };
+  }
+
+  const tmp = path.join(require('os').tmpdir(), 'ct-install-' + process.pid + '.sh');
+  const mount = '/Volumes/ChurchTranslateUpdate';
+  const aside = appPath + '.replacing-' + process.pid;
+  const script = [
+    '#!/bin/bash',
+    '# Written by Church Translate to swap itself. Safe to delete.',
+    'set -u',
+    'DMG=' + JSON.stringify(dmg),
+    'APP=' + JSON.stringify(appPath),
+    'ASIDE=' + JSON.stringify(aside),
+    'MNT=' + JSON.stringify(mount),
+    'PID=' + process.pid,
+    'LOG="$HOME/Library/Application Support/Church Translate/data/logs/install.log"',
+    'mkdir -p "$(dirname "$LOG")"',
+    'say(){ echo "$(date "+%Y-%m-%d %H:%M:%S") $*" >> "$LOG"; }',
+    'say "installing $DMG into $APP"',
+    '# wait for the app to actually be gone (up to 30s)',
+    'for i in $(seq 1 60); do kill -0 "$PID" 2>/dev/null || break; sleep 0.5; done',
+    'if kill -0 "$PID" 2>/dev/null; then say "app did not exit; aborting"; exit 1; fi',
+    'hdiutil detach "$MNT" -quiet 2>/dev/null',
+    'if ! hdiutil attach "$DMG" -nobrowse -quiet -mountpoint "$MNT"; then say "could not mount"; open -a "$APP"; exit 1; fi',
+    'NEW="$MNT/Church Translate.app"',
+    '# refuse to touch the installed app unless the replacement is really there',
+    'if [ ! -f "$NEW/Contents/Info.plist" ]; then say "disk image has no app"; hdiutil detach "$MNT" -quiet; open -a "$APP"; exit 1; fi',
+    'rm -rf "$ASIDE"',
+    'if ! mv "$APP" "$ASIDE"; then say "could not move the old app aside"; hdiutil detach "$MNT" -quiet; open -a "$APP"; exit 1; fi',
+    'if cp -R "$NEW" "$APP"; then',
+    '  xattr -dr com.apple.quarantine "$APP" 2>/dev/null',
+    '  say "installed $( /usr/libexec/PlistBuddy -c "Print :CFBundleVersion" "$APP/Contents/Info.plist" 2>/dev/null )"',
+    '  rm -rf "$ASIDE"',
+    'else',
+    '  say "copy failed — putting the old app back"',
+    '  rm -rf "$APP"; mv "$ASIDE" "$APP"',
+    'fi',
+    'hdiutil detach "$MNT" -quiet 2>/dev/null',
+    'open -a "$APP"',
+    'say "relaunched"',
+    'rm -f "$0"'
+  ].join('\n');
+
+  try {
+    fs.writeFileSync(tmp, script, { mode: 0o755 });
+  } catch (e) {
+    return { ok: false, error: 'Could not prepare the installer: ' + e.message };
+  }
+
+  /* Detached and unref'd, or it dies with us the moment we quit. */
+  try {
+    const child = spawn('/bin/bash', [tmp], { detached: true, stdio: 'ignore' });
+    child.unref();
+  } catch (e) {
+    return { ok: false, error: 'Could not start the installer: ' + e.message };
+  }
+
+  /* Give the renderer a moment to show the message before we go. */
+  forceQuit = true;
+  setTimeout(() => { try { app.quit(); } catch (_) {} }, 600);
+  return { ok: true };
+});
+
 ipcMain.handle('update:reveal', (_e, p2) => { try { shell.showItemInFolder(String(p2)); return true; } catch (_) { return false; } });
 
 ipcMain.handle('config:get', () => loadConfig());
diff --git a/app/package.json b/app/package.json
index 762aca5..7e58b43 100644
--- a/app/package.json
+++ b/app/package.json
@@ -2,7 +2,7 @@
   "name": "church-translate-engine",
   "productName": "Church Translate",
   "version": "3.23.2",
-  "buildNumber": 114,
+  "buildNumber": 115,
   "private": true,
   "description": "Live sermon translation — self-contained: captures audio, transcribes, translates, and serves the congregation page itself",
   "main": "main.js",
@@ -106,7 +106,7 @@
       ]
     },
     "asar": false,
-    "buildVersion": "114",
+    "buildVersion": "115",
     "win": {
       "target": [
         {
diff --git a/app/preload.js b/app/preload.js
index e22dc06..b5a0314 100644
--- a/app/preload.js
+++ b/app/preload.js
@@ -24,6 +24,7 @@ contextBridge.exposeInMainWorld('engineHost', {
   updateCheck:  ()      => ipcRenderer.invoke('update:check'),
   updateDownload: (u, n) => ipcRenderer.invoke('update:download', u, n),
   updateReveal: (p)     => ipcRenderer.invoke('update:reveal', p),
+  updateInstall: (p)    => ipcRenderer.invoke('update:install', p),
   onUpdateProgress: (fn) => ipcRenderer.on('update:progress', (_e, p) => fn(p)),
   settingsExport: ()    => ipcRenderer.invoke('settings:export'),
   settingsImport: ()    => ipcRenderer.invoke('settings:import'),