diff --git a/README.md b/README.md
index 6c095aa..131a56b 100644
--- a/README.md
+++ b/README.md
@@ -89,6 +89,14 @@ Install desktop apps like Moonlight or VLC, and set each Android app's resolutio
 **⚡ One-click tools**<br>
 SSH, SFTP, Steam Link, remote desktop, volume, sleep, restart and shut down.
 
+</td>
+</tr>
+<tr>
+<td colspan="2" valign="top">
+
+**💾 Backup and recovery**<br>
+Copy game saves, settings and Android app data to your computer, and restore them after a factory reset. Sign-in files and keys are never copied. A Return to Game Mode button helps when the headset is stuck in Desktop Mode. Not tested on a headset yet. [How it works](docs/backup-and-recovery.md).
+
 </td>
 </tr>
 </table>
diff --git a/docs/backup-and-recovery.md b/docs/backup-and-recovery.md
new file mode 100644
index 0000000..1007819
--- /dev/null
+++ b/docs/backup-and-recovery.md
@@ -0,0 +1,159 @@
+# Backup and recovery
+
+**Tools → Backup & recovery** copies what a factory reset would lose from the
+Steam Frame to your computer, puts it back afterwards, and gets the headset out
+of Desktop Mode. It runs from Frame Control on a computer, not from the iPhone
+app or the Frame itself.
+
+**Not tested on a headset yet.** Everything here is covered by unit tests and
+the fake Frame (see [Verification](#verification)); the save locations and the
+Desktop Mode switch are taken from Valve's tools and from Proton's layout, not
+from a backup and restore on a real Frame.
+
+## Back up
+
+Choose **Game saves**, **Steam and desktop settings** and **Android app data**
+(all three by default), then **Back up now**. **See what's included** lists each
+part and its size first. Backing up only reads the headset.
+
+Each backup is a folder named after the time it started:
+
+```
+~/Documents/Frame Control Backups/2026-10-23-142530/
+  manifest.json
+  saves/saves-1234.tar.gz          one per game
+  saves/saves-linux.tar.gz
+  settings/settings-steam.tar.gz
+  settings/settings-system.tar.gz
+  android/org.example.game.tar.gz  one per Android app
+```
+
+`manifest.json` records the headset's name, SteamOS version and BUILD_ID, every
+file with its size and SHA-256, and each archive's SHA-256. It also lists what
+was skipped and why. A backup is written under a hidden `.…partial` name and
+renamed when complete, so a cut-off backup never shows up as one.
+
+### What's saved
+
+| Part | From the headset (`~` is `/home/steamos`) | Restored? |
+|---|---|---|
+| Windows game saves | `~/.local/share/Steam/steamapps/compatdata/<appid>/pfx/drive_c/users/steamuser/` → `AppData/Roaming`, `AppData/Local`, `AppData/LocalLow`, `Documents`, `Saved Games`. Wine's own folders in them (`Temp`, `Microsoft`, `D3DSCache`, `CrashDumps`) are left out. Sideloaded Windows games (non-Steam shortcuts) have prefixes here too | Yes |
+| Linux game saves | `~/.config/unity3d`, `~/.local/share/godot/app_userdata`: where Unity and Godot games save by default | Yes |
+| Steam controller layouts | `userdata/<account>/241100/remote/controller_config`, `steamapps/common/Steam Controller Configs/<account>/config` | Yes |
+| Steam library settings | `userdata/<account>/config/localconfig.vdf`, `shortcuts.vdf`, `grid/` (custom artwork) | Kept for reference |
+| Desktop settings | `~/.config/kdeglobals`, `kwinrc`, `kxkbrc` (keyboard layout), `konsolerc`, `dolphinrc` | Yes |
+| SteamVR settings | `~/.config/openvr/config/steamvr.vrsettings` | Kept for reference |
+| Android app data | Each Frame Control Android app's private data, through the existing `backup-data` helper ([sidequest.md](sidequest.md#private-app-data-backups)) | Yes |
+
+"Kept for reference" files are in the backup but not put back automatically:
+Steam and SteamVR rewrite them while they run, and an old `shortcuts.vdf` would
+point at apps that aren't installed after a reset. Open the backup folder to
+copy one by hand if you need it.
+
+### What's never copied
+
+- **Steam sign-in:** `steam.token`, `config/config.vdf`, `loginusers.vdf`,
+  `registry.vdf` and `ssfn*` files.
+- **Keys and passwords:** `~/.ssh`, `~/.gnupg`, keyrings and KWallet, any
+  `*.token`, `*.key` or `*.pem` file, Tailscale state and proxy settings
+  (`secrets.env`). These are refused by name wherever they turn up, including
+  inside a game's folder, and a restore refuses them too.
+- Games, Proton and the Steam runtimes: reinstall them from Steam.
+- Steam Cloud's own folders (`userdata/<account>/<appid>`), shader caches and
+  screenshots (**Tools → Capture & Live** saves those to Pictures).
+- Android apps themselves, their OBB files and shared storage (`/sdcard`).
+- Symbolic links (never followed), and single files over 2 GiB.
+
+Backups aren't encrypted. Game folders can still hold a launcher's login, and
+Android app data can hold an app's, so keep backups private.
+
+Android apps that are open are skipped (the helper needs the app closed); close
+them and back up again.
+
+## Restore after a factory reset
+
+1. Set up the headset again: Developer Mode, **Set Up Connection**, sign in to
+   Steam with the same account.
+2. Reinstall your games, and **start each once** so Proton creates its folders.
+3. Reinstall your Android apps from Frame Control.
+4. **Tools → Backup & recovery → Restore…** on a backup. Frame Control checks
+   each part against the headset and says what it would do: how many files it
+   replaces and how many are new.
+5. Tick the parts to restore and **Restore selected**. It asks before replacing
+   anything.
+
+Parts that can't go back yet are skipped, not failed, with the reason:
+
+| Reason | What to do |
+|---|---|
+| Install the game first | Install it from Steam, then restore |
+| Start the game once | Proton hasn't made its folders yet; start the game, quit, restore |
+| Sign in to Steam first | Controller layouts go under your account's folder |
+| Install the app first / close the app first | Android app data needs the app installed and closed |
+| The backup file doesn't match its checksum | The archive changed since it was made |
+
+A restore writes only the files in the parts you chose, and only inside that
+part's folders: it never deletes a file, and a save archive can't write outside
+its game. Before replacing a file it copies the current one to
+`~/.local/share/frame-control/restore-previous/<time>/` on the headset. Files
+already identical are left alone. Android app data goes through the existing
+`restore-data` helper, which keeps the previous data folder beside it.
+
+## Stuck in Desktop Mode
+
+On the Frame, Game Mode is gamescope running Steam, and the Linux desktop
+normally runs *inside* it as one panel (`steamos-nested-desktop`, see
+[how-the-frame-works.md](how-the-frame-works.md#the-layer-cake)). If that panel
+is what you see, you're already in Game Mode: close it from the Steam dashboard.
+
+Full Desktop Mode is a different session. SteamOS picks the session through
+SDDM's autologin file, `/etc/sddm.conf.d/zz-steamos-autologin.conf` (or the
+default `/etc/sddm.conf.d/steamos.conf`), and switches with
+`steamos-session-select` (`holo-session-select` on newer images). This is what
+Valve's own devkit tools on the Frame read and run
+([`steamos-get-status`](../frame/devkit-utils/steamos-get-status),
+[`steamos-delete`](../frame/devkit-utils/steamos-delete)).
+
+**Check** reads that file and whether gamescope and Plasma are running; it
+changes nothing. When the headset isn't in Game Mode, **Return to Game Mode**
+runs exactly `steamos-session-select gamescope` (or `holo-session-select
+gamescope`) over SSH, after asking. It closes the desktop and anything open in
+it. Frame Control never edits the SDDM files itself, and runs nothing when the
+headset is already in Game Mode or the image has neither command.
+
+**Uncertain:** whether the Frame offers a full Desktop Mode session at all
+(only the nested desktop has been seen on BUILD_ID 20260922.6101926 and
+20260925.6191901), and whether `steamos-session-select` there works without
+the Developer Mode password. If the switch is refused, Frame Control says so and
+leaves the headset as it was.
+
+### Manual fallback
+
+If the button can't help, or the headset isn't reachable:
+
+1. **Restart it:** hold Power about 10 seconds until the light goes off, then
+   power on. On the Steam Deck, **Switch to Desktop** starts a one-shot
+   Desktop Mode session, so a restart brings Game Mode back. That the Frame
+   behaves the same is **inferred**, not tested.
+2. **Over SSH** (Developer Mode on), run Valve's switch yourself:
+   `ssh frame steamos-session-select gamescope`.
+3. **Boot menu:** hold Power 10 seconds, then power on while holding the AUX
+   button on top of Power. Choose `Current`, or `Previous` to start the other
+   SteamOS slot; both keep your data. Details and the further options
+   (`Repair Steam Installation`, `Erase User Data`, a full re-image) are in
+   [how-the-frame-works.md](how-the-frame-works.md#facts-worth-knowing) and
+   [recovery-and-images.md](recovery-and-images.md). Back up first if you can:
+   `Erase User Data` is a factory reset.
+
+## Verification
+
+`tests/test_backup.py` runs the headset-side script (`ui/frame_backup_remote.py`)
+for real against a folder laid out like the Frame's home, with only SSH faked:
+which paths are picked, that sign-in files and keys never are (also inside game
+folders), links never followed, the manifest and its checksums, restore checks
+after a reset (game not installed, no Proton folders yet, not signed in), that a
+restore replaces only its own files and keeps the old ones, unsafe archives
+(`..`, absolute paths, links, other games' folders) writing nothing, backup
+names that try to leave the backups folder, and the exact Game Mode command.
+`tests/e2e/test_recovery_kit.py` backs up a Proton save from the fake Frame through
+the server, deletes it and restores it. Neither involves a real headset.
diff --git a/docs/frame-control.md b/docs/frame-control.md
index b3779e9..d1c9679 100644
--- a/docs/frame-control.md
+++ b/docs/frame-control.md
@@ -53,6 +53,11 @@ counts them while they run.
   `~/Videos/SteamFrame`, and **Steam clips**: export clips and background
   recordings from Steam's game recording at any length, without re-encoding.
   See [recording.md](recording.md). Not tested on a headset yet.
+- **Backup & recovery** (Tools): copy game saves, settings and Android app data
+  to `~/Documents/Frame Control Backups/<time>/` with a checksummed manifest,
+  restore chosen parts after a factory reset, and **Return to Game Mode** when
+  the headset is stuck in Desktop Mode. Sign-in files and keys are never copied.
+  Not tested on a headset yet. See [backup-and-recovery.md](backup-and-recovery.md).
 - **Battery** with charging state: charge rate in watts, time to full or empty,
   charger type and wattage (for example USB-C PD 20 W), and battery temperature.
 - **Status**: storage, memory, temperature, Wi-Fi, uptime, and whether SteamVR,
diff --git a/docs/how-the-frame-works.md b/docs/how-the-frame-works.md
index 2d4cbf9..d070d88 100644
--- a/docs/how-the-frame-works.md
+++ b/docs/how-the-frame-works.md
@@ -96,5 +96,6 @@ ssh frame 'cat /opt/steamvr/resources/webinterface/dashboard/localization/dashbo
 - Remote access from anywhere: [tailscale.md](tailscale.md)
 - Floating windows in space: [panels.md](panels.md)
 - Recovery images, what's in them, testing without the headset: [recovery-and-images.md](recovery-and-images.md)
+- Backing up saves and settings, restoring after a reset, leaving Desktop Mode: [backup-and-recovery.md](backup-and-recovery.md)
 - Frame Control on iPhone (the server running on the Frame itself): [iphone.md](iphone.md)
 - What's still unverified: [open-questions.md](open-questions.md)
diff --git a/docs/recovery-and-images.md b/docs/recovery-and-images.md
index ad170d6..537ff12 100644
--- a/docs/recovery-and-images.md
+++ b/docs/recovery-and-images.md
@@ -4,6 +4,9 @@ Where to get the Steam Frame's operating system, what's inside it, and how to
 run it for testing without the headset. For recovering a Frame that won't boot,
 see the boot menu and boot-loop entries in
 [how-the-frame-works.md](how-the-frame-works.md#facts-worth-knowing).
+To keep your game saves, settings and Android app data through a factory reset
+(`Erase User Data`) or a re-image, and to get out of Desktop Mode, see
+[backup-and-recovery.md](backup-and-recovery.md).
 
 ## Downloads
 
diff --git a/docs/testing.md b/docs/testing.md
index e45a762..a2e00d2 100644
--- a/docs/testing.md
+++ b/docs/testing.md
@@ -314,3 +314,14 @@ Chromium rendering and the same helper through HTTP. Close the switcher after
 testing. [The recorded device checks](panels.md#frame-controls-panel-switcher)
 cover actual focus, HTTP guards and an OpenXR sample transition, and separately
 identify the unverified Steam-game, spatial layout, reboot and laser behaviors.
+
+## Backup and recovery kit
+
+`tests/test_backup.py` runs the headset-side script `ui/frame_backup_remote.py`
+for real against a temporary folder laid out like the Frame's home, with only
+SSH faked: path selection and the secrets it must never copy, the manifest and
+checksums, restore checks after a reset, restore writing only its own files,
+unsafe archives and backup names, and the exact Game Mode command.
+`tests/e2e/test_recovery_kit.py` backs up and restores a Proton save on the fake
+Frame through the server. See [backup-and-recovery.md](backup-and-recovery.md#verification).
+No backup or restore has been run on a real headset yet.
diff --git a/tests/e2e/test_recovery_kit.py b/tests/e2e/test_recovery_kit.py
new file mode 100644
index 0000000..a663943
--- /dev/null
+++ b/tests/e2e/test_recovery_kit.py
@@ -0,0 +1,55 @@
+"""Backup and recovery kit through the server against the fake Frame: a Proton game's save
+goes to this computer and back, Steam's sign-in token never leaves the headset."""
+import json
+import shutil
+import tarfile
+import unittest
+from pathlib import Path
+
+import harness
+from harness import api, finished, ok, ssh
+
+harness.require()
+
+SAVE = '.local/share/Steam/steamapps/compatdata/620980/pfx/drive_c/users/steamuser/AppData/LocalLow/Beat Games/Beat Saber/PlayerData.dat'
+
+
+class Backup(harness.FrameTestCase):
+    def test_saves_round_trip_and_secrets_stay(self):
+        ssh(f"mkdir -p ~/'{Path(SAVE).parent}' && printf 'level 7' > ~/'{SAVE}' && "
+            "mkdir -p ~/.steam && printf SECRET > ~/.steam/steam.token")
+        job = finished(ok('POST', '/api/backup', {'action': 'backup', 'kinds': ['saves', 'settings']}), 120)
+        self.assertIsNone(job['error'], job)
+        folder = Path(job['result']['path'])
+        self.addCleanup(shutil.rmtree, str(folder), True)
+        manifest = json.loads((folder / 'manifest.json').read_text())
+        self.assertEqual(manifest['headset']['build'], '20260922.6101926')
+        saves = next(p for p in manifest['parts'] if p['id'] == 'saves:620980')
+        self.assertEqual(saves['label'], 'Beat Saber saves')
+        self.assertEqual([f['path'] for f in saves['files']], [SAVE])
+        for part in manifest['parts']:
+            with tarfile.open(str(folder / part['archive'])) as tar:
+                self.assertFalse([m.name for m in tar if 'steam.token' in m.name])
+        self.assertEqual(ssh('cat ~/.steam/steam.token'), 'SECRET')  # read-only on the headset
+
+        ssh(f"rm ~/'{SAVE}'")
+        name = folder.name
+        plan = {p['id']: p for p in ok('POST', '/api/backup', {'action': 'plan', 'name': name})['parts']}
+        self.assertEqual((plan['saves:620980']['status'], plan['saves:620980']['new']), ('ok', 1))
+        status, out, _ = api('POST', '/api/backup', {'action': 'restore', 'name': name, 'parts': ['saves:620980']})
+        self.assertEqual(status, 400, out)  # not confirmed
+        job = finished(ok('POST', '/api/backup', {'action': 'restore', 'name': name, 'parts': ['saves:620980'],
+                                                  'confirm': True}), 120)
+        self.assertIsNone(job['error'], job)
+        self.assertEqual(ssh(f"cat ~/'{SAVE}'"), 'level 7')
+
+    def test_bad_names_and_session(self):
+        status, out, _ = api('POST', '/api/backup', {'action': 'plan', 'name': '../../etc'})
+        self.assertEqual(status, 400, out)
+        state = ok('POST', '/api/backup', {'action': 'session'})
+        self.assertIn(state['mode'], ('game', 'desktop', 'unknown'))
+        self.assertIsNone(state['selector'])  # the fake has no session switch command
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tests/test_backup.py b/tests/test_backup.py
new file mode 100644
index 0000000..2cfbd72
--- /dev/null
+++ b/tests/test_backup.py
@@ -0,0 +1,439 @@
+"""Backup and recovery kit (ui/frame_backup.py, ui/frame_backup_remote.py) against a folder laid
+out like the Frame's home. The headset-side script runs for real, locally; only SSH is faked."""
+import sandbox  # noqa: F401  (first: keeps tests off real data and services)
+import io
+import json
+import os
+from pathlib import Path
+import shlex
+import subprocess
+import sys
+import tarfile
+import tempfile
+import unittest
+from unittest.mock import patch
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / 'ui'))
+import frame_android as android  # noqa: E402
+import frame_backup as backup  # noqa: E402
+import frame_backup_remote as remote  # noqa: E402
+import server  # noqa: E402
+
+STEAM = '.local/share/Steam'
+USER = STEAM + '/steamapps/compatdata/%s/pfx/drive_c/users/steamuser'
+SECRETS = ['.steam/steam.token', STEAM + '/config/config.vdf', STEAM + '/config/loginusers.vdf',
+           STEAM + '/ssfn123456', '.ssh/id_ed25519', '.ssh/authorized_keys',
+           USER % 1234 + '/AppData/Roaming/Launcher/session.token',
+           USER % 1234 + '/AppData/Roaming/Launcher/.ssh/id_rsa',
+           '.config/cliproxyapi/secrets.env', '.local/share/keyrings/login.keyring']
+
+
+def write(home, rel, data=b'x'):
+    path = Path(home) / rel
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_bytes(data if isinstance(data, bytes) else data.encode())
+    return path
+
+
+def manifest(home, appid, name):
+    write(home, '%s/steamapps/appmanifest_%s.acf' % (STEAM, appid),
+          '"AppState"\n{\n\t"appid"\t\t"%s"\n\t"name"\t\t"%s"\n}\n' % (appid, name))
+
+
+def frame_home(home):
+    """A Frame before a reset: one Proton game, a Linux game, settings and secrets."""
+    manifest(home, 1234, 'Test Game')
+    write(home, USER % 1234 + '/AppData/Roaming/Studio/Game/save1.dat', b'save one')
+    write(home, USER % 1234 + '/Documents/My Games/Game/profile.sav', b'profile')
+    write(home, USER % 1234 + '/AppData/Local/Temp/junk.tmp', b'junk')
+    write(home, USER % 1234 + '/AppData/Local/Microsoft/Windows/x.db', b'wine')
+    write(home, USER % 999 + '/AppData/Local/Temp/only-cache', b'c')        # no saves: no part
+    write(home, STEAM + '/steamapps/compatdata/2800000001/internal/org.example/x', b'android')
+    write(home, STEAM + '/userdata/555/config/localconfig.vdf', b'local')
+    write(home, STEAM + '/userdata/555/config/shortcuts.vdf', b'shortcuts')
+    write(home, STEAM + '/userdata/555/241100/remote/controller_config/1234/layout.vdf', b'layout')
+    write(home, STEAM + '/userdata/555/1234/remote/cloud.sav', b'cloud')    # Steam Cloud's own
+    write(home, STEAM + '/userdata/555/760/remote/1234/screenshots/a.jpg', b'shot')
+    write(home, '.config/kdeglobals', b'[General]')
+    write(home, '.config/openvr/config/steamvr.vrsettings', b'{}')
+    write(home, '.config/unity3d/Company/LinuxGame/prefs', b'prefs')
+    write(home, '.bashrc', b'# mine')
+    for rel in SECRETS:
+        write(home, rel, b'SECRET')
+
+
+class Remote(unittest.TestCase):
+    def setUp(self):
+        self.tmp = tempfile.TemporaryDirectory()
+        self.home = Path(self.tmp.name)
+        patcher = patch.object(remote, 'HOME', self.home)
+        patcher.start()
+        self.addCleanup(patcher.stop)
+        self.addCleanup(self.tmp.cleanup)
+
+    def files(self, part):
+        return [rel for rel, _ in remote.part_files(part)[0]]
+
+    def test_plan_picks_saves_and_settings_and_never_secrets(self):
+        frame_home(self.home)
+        plan = remote.plan()
+        ids = [p['id'] for p in plan['parts']]
+        self.assertEqual(ids, ['saves:1234', 'saves:linux', 'settings:steam', 'settings:system'])
+        self.assertEqual(plan['parts'][0]['label'], 'Test Game saves')
+        saves = self.files('saves:1234')
+        self.assertEqual(sorted(saves), [USER % 1234 + '/AppData/Roaming/Studio/Game/save1.dat',
+                                         USER % 1234 + '/Documents/My Games/Game/profile.sav'])
+        steam = self.files('settings:steam')
+        self.assertIn(STEAM + '/userdata/555/241100/remote/controller_config/1234/layout.vdf', steam)
+        self.assertIn(STEAM + '/userdata/555/config/localconfig.vdf', steam)
+        self.assertFalse([f for f in steam if '/1234/remote/' in f or '/760/' in f])
+        everything = sum((self.files(i) for i in ids), [])
+        for rel in SECRETS + ['.bashrc']:
+            self.assertNotIn(rel, everything)
+        self.assertFalse([f for f in everything if remote.is_secret(f)])
+        self.assertTrue(any('steam.token' in x for x in plan['excluded']))
+        # The controller layout goes back; localconfig.vdf and shortcuts.vdf are for reference.
+        steam_part = plan['parts'][2]
+        self.assertEqual((steam_part['files'], steam_part['restorable']), (3, 1))
+
+    def test_secret_names(self):
+        for rel in SECRETS + ['a/b/ID_RSA.pub', 'x/kwalletd/k', 'x/cert.PEM']:
+            self.assertTrue(remote.is_secret(rel), rel)
+        for rel in ['saves/game.sav', 'Documents/tokens-collected.txt', 'config/localconfig.vdf']:
+            self.assertFalse(remote.is_secret(rel), rel)
+
+    @unittest.skipIf(os.name == 'nt', 'symlinks need privileges on Windows')
+    def test_links_are_never_followed(self):
+        frame_home(self.home)
+        outside = write(self.home, 'elsewhere/private.txt', b'p')
+        base = self.home / (USER % 1234) / 'Documents'
+        os.symlink(str(outside.parent), str(base / 'linked-dir'))
+        os.symlink(str(outside), str(base / 'linked-file'))
+        self.assertFalse([f for f in self.files('saves:1234') if 'linked' in f])
+
+    def test_big_files_are_listed_as_skipped(self):
+        frame_home(self.home)
+        with patch.object(remote, 'MAX_FILE', 3):
+            files, skipped = remote.part_files('saves:1234')
+        self.assertEqual(files, [])
+        self.assertEqual({s['reason'] for s in skipped}, {'over 2 GiB'})
+
+    def test_pack_holds_exactly_the_planned_files(self):
+        frame_home(self.home)
+        out = io.BytesIO()
+        remote.pack('saves:1234', out)
+        out.seek(0)
+        with tarfile.open(fileobj=out, mode='r:gz') as archive:
+            names = sorted(m.name for m in archive)
+        self.assertEqual(names, sorted(self.files('saves:1234')))
+        with self.assertRaises(ValueError):
+            remote.pack('saves:../../etc', io.BytesIO())
+
+    def archive(self, members):
+        out = io.BytesIO()
+        with tarfile.open(fileobj=out, mode='w:gz') as tar:
+            for name, data in members:
+                info = tarfile.TarInfo(name)
+                info.size = len(data)
+                tar.addfile(info, io.BytesIO(data))
+        out.seek(0)
+        return out
+
+    def test_check_after_a_reset(self):
+        save = USER % 1234 + '/AppData/Roaming/Studio/Game/save1.dat'
+        ask = {'parts': [{'id': 'saves:1234', 'files': [save]},
+                         {'id': 'settings:steam', 'files': [STEAM + '/userdata/555/241100/remote/controller_config/1/a.vdf']},
+                         {'id': 'settings:system', 'files': ['.config/openvr/config/steamvr.vrsettings']},
+                         {'id': 'saves:../x', 'files': []}]}
+        states = lambda: [p['status'] for p in remote.check(ask)['parts']]  # noqa: E731
+        self.assertEqual(states(), ['not_installed', 'no_account', 'reference', 'unknown'])
+        manifest(self.home, 1234, 'Test Game')
+        (self.home / STEAM / 'userdata/555').mkdir(parents=True)
+        self.assertEqual(states()[:2], ['no_prefix', 'ok'])
+        (self.home / (USER % 1234)).mkdir(parents=True)
+        result = remote.check(ask)['parts'][0]
+        self.assertEqual((result['status'], result['new'], result['replace']), ('ok', 1, 0))
+        write(self.home, save, b'newer')
+        self.assertEqual(remote.check(ask)['parts'][0]['replace'], 1)
+
+    def test_restore_replaces_only_its_files_and_keeps_the_old_ones(self):
+        manifest(self.home, 1234, 'Test Game')
+        save = USER % 1234 + '/AppData/Roaming/Studio/Game/save1.dat'
+        write(self.home, save, b'played since')
+        other = write(self.home, USER % 1234 + '/AppData/Roaming/Studio/Game/other.dat', b'untouched')
+        bashrc = write(self.home, '.bashrc', b'# mine')
+        source = self.archive([(save, b'from backup'), (USER % 1234 + '/Documents/new.sav', b'new'),
+                               ('.bashrc', b'# replaced?')])
+        result = remote.restore('saves:1234', '20261023-120000', source)
+        self.assertEqual((result['written'], result['replaced']), (2, 1))
+        self.assertEqual(result['held'], {'reference': 1})
+        self.assertEqual((self.home / save).read_bytes(), b'from backup')
+        self.assertEqual(other.read_bytes(), b'untouched')
+        self.assertEqual(bashrc.read_bytes(), b'# mine')
+        kept = self.home / remote.PREVIOUS / '20261023-120000' / save
+        self.assertEqual(kept.read_bytes(), b'played since')
+        self.assertFalse([p for p in (self.home / save).parent.iterdir() if p.name.endswith('.part')])
+
+    def test_unsafe_archives_write_nothing(self):
+        manifest(self.home, 1234, 'Test Game')
+        (self.home / (USER % 1234)).mkdir(parents=True)
+        good = (USER % 1234 + '/Documents/a.sav', b'a')
+        for bad in ('../escape', '/etc/passwd', USER % 1234 + '/Documents/../../../../../../x',
+                    USER % 1234 + '/Documents/a.sav'):
+            with self.assertRaises(ValueError, msg=bad):
+                remote.restore('saves:1234', '20261023-120000', self.archive([good, (bad, b'evil')]))
+            self.assertFalse((self.home / good[0]).exists(), bad)
+        link = io.BytesIO()
+        with tarfile.open(fileobj=link, mode='w:gz') as tar:
+            info = tarfile.TarInfo(USER % 1234 + '/Documents/l')
+            info.type, info.linkname = tarfile.SYMTYPE, '/etc/passwd'
+            tar.addfile(info)
+        link.seek(0)
+        with self.assertRaises(ValueError):
+            remote.restore('saves:1234', '20261023-120000', link)
+        with self.assertRaises(ValueError):
+            remote.restore('saves:1234', '../stamp', self.archive([good]))
+
+    def test_restore_refuses_secrets_and_other_games(self):
+        manifest(self.home, 1234, 'Test Game')
+        (self.home / (USER % 1234)).mkdir(parents=True)
+        result = remote.restore('saves:1234', '20261023-120000', self.archive([
+            (USER % 1234 + '/AppData/Roaming/L/auth.token', b't'), (USER % 5678 + '/Documents/x.sav', b'x')]))
+        self.assertEqual(result['written'], 0)
+        self.assertEqual(result['held'], {'refused': 1, 'reference': 1})
+
+    def test_session_reads_the_mode(self):
+        conf = write(self.home, 'zz-steamos-autologin.conf', '[Autologin]\nSession=plasma-steamos-wayland-oneshot.desktop\n')
+        running = set()
+        with patch.object(remote, 'SDDM_CONFS', (str(conf),)), \
+                patch.object(remote, '_running', side_effect=lambda n, full=False: n in running), \
+                patch.object(remote.shutil, 'which', side_effect=lambda n: '/usr/bin/' + n if n == 'steamos-session-select' else None):
+            state = remote.session()
+            self.assertEqual((state['mode'], state['selector']), ('desktop', 'steamos-session-select'))
+            self.assertEqual(state['configured'], 'plasma-steamos-wayland-oneshot.desktop')
+            running.update({'gamescope', 'plasmashell'})  # the nested desktop panel
+            self.assertEqual(remote.session()['mode'], 'game')
+
+
+def fake_ssh(home, os_release):
+    """Runs the headset-side command locally, as the Frame's python3 would."""
+    def run(command, src=None, dst=None, timeout=None):
+        argv = shlex.split(command)
+        assert argv[:2] == ['python3', '-c'], argv
+        data = src if isinstance(src, bytes) else src.read() if src is not None else b''
+        env = dict(os.environ, FRAME_BACKUP_HOME=str(home), FRAME_BACKUP_OS_RELEASE=str(os_release))
+        r = subprocess.run([sys.executable, *argv[1:]], input=data, capture_output=True, env=env)
+        if r.returncode:
+            raise backup.BackupError(r.stderr.decode(errors='replace'))
+        if dst is not None:
+            dst.write(r.stdout)
+            return None
+        return r.stdout
+    return run
+
+
+class Local(unittest.TestCase):
+    def setUp(self):
+        self.tmp = tempfile.TemporaryDirectory()
+        self.addCleanup(self.tmp.cleanup)
+        base = Path(self.tmp.name)
+        self.home, self.store = base / 'frame', base / 'backups'
+        self.release = write(base, 'os-release', 'ID=steamos\nVERSION_ID=0.4.1\nBUILD_ID=20260925.6191901\n')
+        frame_home(self.home)
+        for p in (patch.dict(os.environ, FRAME_BACKUP_DIR=str(self.store)),
+                  patch.object(backup, '_ssh', side_effect=fake_ssh(self.home, self.release))):
+            p.start()
+            self.addCleanup(p.stop)
+
+    def android_backup(self, package, destination):
+        write(Path(destination).parent, Path(destination).name, b'android archive ' + package.encode())
+        return {'package': package, 'instance': android.instance_id(package), 'files': 3, 'bytes': 42,
+                'path': str(destination), 'sha256': backup._sha256(destination)}
+
+    def make(self):
+        apps = [{'package': 'org.example.open', 'label': 'Open app', 'running': True},
+                {'package': 'org.example.game', 'label': 'Game', 'running': False}]
+        with patch.object(android, 'list_apps', return_value=apps), \
+                patch.object(android, 'backup_data', side_effect=self.android_backup) as data, \
+                patch.object(backup.time, 'strftime', side_effect=lambda f: '2026-10-23-120000' if f == '%Y-%m-%d-%H%M%S'
+                             else '2026-10-23T12:00:00+0100'):
+            result = backup.backup(headset='My Frame')
+        data.assert_called_once()
+        return result
+
+    def test_backup_writes_a_manifest_with_checksums(self):
+        result = self.make()
+        folder = backup.backup_path('2026-10-23-120000')  # resolved: macOS's temp folder is a link
+        self.assertEqual(result['path'], str(folder))
+        self.assertEqual(sorted(p.name for p in self.store.iterdir()), ['2026-10-23-120000'])  # no .partial left
+        m = json.loads((folder / 'manifest.json').read_text())
+        self.assertEqual(m['headset'], {'name': 'My Frame', 'build': '20260925.6191901', 'version': '0.4.1'})
+        self.assertEqual([p['id'] for p in m['parts']],
+                         ['saves:1234', 'saves:linux', 'settings:steam', 'settings:system', 'android:org.example.game'])
+        for part in m['parts']:
+            self.assertEqual(backup._sha256(folder / part['archive']), part['sha256'])
+        saves = m['parts'][0]
+        self.assertEqual(saves['archive'], 'saves/saves-1234.tar.gz')
+        self.assertEqual(sum(f['bytes'] for f in saves['files']), saves['bytes'])
+        self.assertEqual(saves['files'][0]['sha256'], __import__('hashlib').sha256(b'save one').hexdigest())
+        self.assertEqual([s['id'] for s in m['skipped']], ['android:org.example.open'])
+        for part in m['parts'][:-1]:
+            with tarfile.open(str(folder / part['archive'])) as tar:
+                for member in tar:
+                    self.assertFalse(remote.is_secret(member.name), member.name)
+                    self.assertNotEqual(tar.extractfile(member).read(), b'SECRET', member.name)
+
+    def test_a_failed_backup_leaves_nothing_behind(self):
+        with patch.object(backup, 'inspect_archive', side_effect=backup.BackupError('cut off')), \
+                patch.object(android, 'list_apps', return_value=[]):
+            with self.assertRaises(backup.BackupError):
+                backup.backup(kinds=['saves'])
+        self.assertEqual(list(self.store.iterdir()), [])
+
+    def test_backup_names_cannot_leave_the_folder(self):
+        for name in ('../2026-10-23-120000', '2026-10-23-120000/..', '..', '/etc', 'C:\\x', '',
+                     '2026-10-23-120000/../../x', '2026-10-23-12000', None, 5):
+            with self.assertRaises(backup.BackupError, msg=repr(name)):
+                backup.backup_path(name)
+        self.assertEqual(backup.backup_path('2026-10-23-120000'), (self.store / '2026-10-23-120000').resolve())
+
+    def test_manifest_entries_cannot_point_outside_the_backup(self):
+        self.make()
+        path = self.store / '2026-10-23-120000' / 'manifest.json'
+        m = json.loads(path.read_text())
+        for archive in ('../../secret.tar.gz', '/etc/passwd', 'saves/saves-5678.tar.gz'):
+            m['parts'][0]['archive'] = archive
+            path.write_text(json.dumps(m))
+            with self.assertRaises(backup.BackupError, msg=archive):
+                backup.read_manifest('2026-10-23-120000')
+
+    def reset(self):
+        """A factory reset: the home folder is empty again."""
+        import shutil
+        shutil.rmtree(str(self.home))
+        self.home.mkdir()
+
+    def test_restore_after_a_reset_skips_what_is_not_back_yet(self):
+        self.make()
+        self.reset()
+        manifest(self.home, 1234, 'Test Game')
+        (self.home / (USER % 1234)).mkdir(parents=True)  # started once
+        with patch.object(android, 'list_apps', return_value=[]):
+            plan = {p['id']: p for p in backup.restore_plan('2026-10-23-120000')['parts']}
+            self.assertEqual(plan['saves:1234']['status'], 'ok')
+            self.assertEqual(plan['settings:steam']['status'], 'no_account')
+            self.assertEqual(plan['android:org.example.game']['status'], 'not_installed')
+            with self.assertRaises(backup.BackupError):
+                backup.restore('2026-10-23-120000', ['saves:1234'])  # not confirmed
+            self.assertFalse((self.home / (USER % 1234) / 'AppData').exists())
+            result = backup.restore('2026-10-23-120000', ['saves:1234', 'settings:steam', 'android:org.example.game'],
+                                    confirmed=True)
+        self.assertEqual([r['id'] for r in result['restored']], ['saves:1234'])
+        self.assertEqual({s['id'] for s in result['skipped']}, {'settings:steam', 'android:org.example.game'})
+        self.assertEqual((self.home / (USER % 1234) / 'AppData/Roaming/Studio/Game/save1.dat').read_bytes(), b'save one')
+
+    def test_android_data_goes_back_through_the_existing_helper(self):
+        self.make()
+        apps = [{'package': 'org.example.game', 'label': 'Game', 'running': False}]
+        with patch.object(android, 'list_apps', return_value=apps), \
+                patch.object(android, 'restore_data', return_value={'restored': True}) as restore:
+            result = backup.restore('2026-10-23-120000', ['android:org.example.game'], confirmed=True)
+        restore.assert_called_once_with('org.example.game', str(backup.backup_path('2026-10-23-120000') /
+                                                                 'android' / 'org.example.game.tar.gz'))
+        self.assertEqual(len(result['restored']), 1)
+        apps[0]['running'] = True
+        with patch.object(android, 'list_apps', return_value=apps), patch.object(android, 'restore_data') as restore:
+            result = backup.restore('2026-10-23-120000', ['android:org.example.game'], confirmed=True)
+        restore.assert_not_called()
+        self.assertEqual(result['skipped'][0]['reason'], 'Close the app first')
+
+    def test_a_damaged_archive_is_skipped(self):
+        self.make()
+        with open(str(self.store / '2026-10-23-120000/saves/saves-1234.tar.gz'), 'ab') as f:
+            f.write(b'tampered')
+        with patch.object(android, 'list_apps', return_value=[]):
+            result = backup.restore('2026-10-23-120000', ['saves:1234'], confirmed=True)
+        self.assertEqual(result['restored'], [])
+        self.assertIn('checksum', result['skipped'][0]['reason'])
+
+    def test_list_backups(self):
+        self.make()
+        (self.store / '.2026-10-23-130000.partial').mkdir()
+        (self.store / 'notes').mkdir()
+        listed = backup.list_backups()['backups']
+        self.assertEqual([b['name'] for b in listed], ['2026-10-23-120000'])
+        self.assertEqual(listed[0]['build'], '20260925.6191901')
+
+
+class Ssh(unittest.TestCase):
+    def test_bytes_go_as_input_and_files_as_stdin(self):
+        done = subprocess.CompletedProcess([], 0, b'{}', b'')
+        with patch.object(backup.frame_host, 'run_ssh', return_value=done) as run:
+            backup._ssh('true', src=b'{"parts": []}')
+            self.assertEqual(run.call_args.kwargs['input'], b'{"parts": []}')
+            self.assertNotIn('stdin', run.call_args.kwargs)
+            with tempfile.TemporaryFile() as f:
+                backup._ssh('true', src=f)
+                self.assertIs(run.call_args.kwargs['stdin'], f)
+            backup._ssh('true')
+            self.assertIs(run.call_args.kwargs['stdin'], subprocess.DEVNULL)
+            self.assertEqual(run.call_args.args[0][-1], 'true')
+        with patch.object(backup.frame_host, 'run_ssh',
+                          return_value=subprocess.CompletedProcess([], 1, b'', b'Permission denied')):
+            with self.assertRaisesRegex(backup.BackupError, 'Permission denied'):
+                backup._ssh('true')
+
+
+class GameMode(unittest.TestCase):
+    def test_command_is_only_ever_the_session_switch(self):
+        self.assertEqual(backup.session_command('steamos-session-select'), 'steamos-session-select gamescope')
+        self.assertEqual(backup.session_command('holo-session-select'), 'holo-session-select gamescope')
+        for bad in (None, '', 'rm -rf ~', '/tmp/steamos-session-select', 'steamos-session-select; reboot'):
+            with self.assertRaises(backup.BackupError):
+                backup.session_command(bad)
+
+    def test_switch_needs_confirmation_and_desktop_mode(self):
+        with patch.object(backup, '_ssh') as ssh:
+            with self.assertRaises(backup.BackupError):
+                backup.return_to_game_mode()
+            ssh.assert_not_called()
+        with patch.object(backup, 'session_status', return_value={'mode': 'game', 'selector': 'steamos-session-select'}), \
+                patch.object(backup, '_ssh') as ssh:
+            self.assertFalse(backup.return_to_game_mode(confirmed=True)['switched'])
+            ssh.assert_not_called()
+        with patch.object(backup, 'session_status', return_value={'mode': 'desktop', 'selector': 'steamos-session-select'}), \
+                patch.object(backup, '_ssh') as ssh:
+            self.assertTrue(backup.return_to_game_mode(confirmed=True)['switched'])
+            ssh.assert_called_once_with('steamos-session-select gamescope', timeout=60)
+            ssh.side_effect = backup.BackupError('the headset took too long to answer')  # the session restarted
+            self.assertTrue(backup.return_to_game_mode(confirmed=True)['switched'])
+            ssh.side_effect = backup.BackupError('Interactive authentication required')
+            with self.assertRaisesRegex(backup.BackupError, 'manual steps'):
+                backup.return_to_game_mode(confirmed=True)
+        with patch.object(backup, 'session_status', return_value={'mode': 'desktop', 'selector': None}), \
+                patch.object(backup, '_ssh') as ssh:
+            with self.assertRaises(backup.BackupError):
+                backup.return_to_game_mode(confirmed=True)
+            ssh.assert_not_called()
+
+
+class Endpoint(unittest.TestCase):
+    def test_guards_run_before_the_headset(self):
+        with patch.object(backup, '_ssh') as ssh, patch.object(server, 'start_job') as job:
+            for body in ({'action': 'plan', 'name': '../x'}, {'action': 'open', 'name': '..'},
+                         {'action': 'restore', 'name': '2026-10-23-120000', 'parts': ['saves:1234']},
+                         {'action': 'restore', 'name': '2026-10-23-120000', 'parts': ['saves:x'], 'confirm': True},
+                         {'action': 'gamemode'}, {'action': 'backup', 'kinds': ['ssh-keys']}, {'action': 'nope'}):
+                with self.assertRaises(server.Failure, msg=body) as caught:
+                    server.backup_action(body)
+                self.assertEqual(caught.exception.status, 400)
+            ssh.assert_not_called()
+            job.assert_not_called()
+            with patch.object(server, 'LOCAL', True):
+                with self.assertRaises(server.Failure):
+                    server.backup_action({'action': 'list'})
+
+
+if __name__ == '__main__':
+    unittest.main()
diff --git a/tests/test_page_startup.py b/tests/test_page_startup.py
index a482e7f..4746ebc 100644
--- a/tests/test_page_startup.py
+++ b/tests/test_page_startup.py
@@ -9,7 +9,7 @@ import subprocess
 import unittest
 
 ROOT = pathlib.Path(__file__).resolve().parents[1]
-STUBS = ['$', 'toggleLive', 'scrollToY', 'scroller', 'loadMacView', 'loadPanels', 'loadPanelSwitcher', 'loadTitles', 'showAndroidTab',
+STUBS = ['$', 'toggleLive', 'scrollToY', 'scroller', 'loadMacView', 'loadPanels', 'loadPanelSwitcher', 'loadBackups', 'loadTitles', 'showAndroidTab',
          'loadAndroid', 'loadDisplays', 'setGameSource', 'requestAnimationFrame']
 
 RUN = r'''
diff --git a/ui/frame_backup.py b/ui/frame_backup.py
new file mode 100644
index 0000000..8875942
--- /dev/null
+++ b/ui/frame_backup.py
@@ -0,0 +1,397 @@
+"""Backup and recovery kit: copy game saves, settings and Android app data off the Frame,
+put them back after a factory reset, and get out of Desktop Mode. Python stdlib only.
+
+A backup is a folder in ~/Documents/Frame Control Backups/<YYYY-MM-DD-HHMMSS>/ on this
+computer: one tar.gz per part (saves/, settings/, android/) and manifest.json listing every
+file with its size and SHA-256, the archives' checksums and the headset's BUILD_ID. What the
+parts hold, and what is never copied, is decided on the headset by frame_backup_remote.py.
+Backing up only reads the headset. See docs/backup-and-recovery.md.
+
+CLI: python3 ui/frame_backup.py backup | list | plan NAME | restore NAME PART... | session | game-mode
+"""
+import hashlib
+import json
+import os
+from pathlib import Path
+import re
+import shlex
+import shutil
+import subprocess
+import sys
+import tarfile
+import time
+
+import frame_android as android
+import frame_host
+
+REMOTE = Path(__file__).resolve().parent / 'frame_backup_remote.py'
+NAME = re.compile(r'^\d{4}-\d{2}-\d{2}-\d{6}$')
+ARCHIVE = re.compile(r'^(saves|settings|android)/[A-Za-z0-9._-]{1,200}\.tar\.gz$')
+PART = re.compile(r'^(saves:(\d{1,10}|linux)|settings:(steam|system)|android:[A-Za-z][\w]*(\.[A-Za-z_][\w]*)+)$')
+KINDS = ('saves', 'settings', 'android')
+FORMAT = 1
+# The switch Valve's own devkit tools use (frame/devkit-utils/steamos-delete). Nothing else
+# is ever run as a session command.
+SELECTORS = ('holo-session-select', 'steamos-session-select')
+REASONS = {
+    'not_installed': 'Install the game first, then restore its saves',
+    'no_prefix': 'Start the game once so Proton sets up its folders, then restore',
+    'no_account': 'Sign in to Steam on the headset first',
+    'reference': 'Kept for reference only; copy by hand if you need it',
+    'refused': 'Not restored: the path is not safe to write',
+    'running': 'Close the app first',
+    'damaged': "The backup file doesn't match its checksum",
+    'missing': 'The backup file is missing',
+    'empty': 'Nothing to restore',
+    'unknown': 'Not something this version of Frame Control can restore',
+}
+
+
+class BackupError(android.FrameError):
+    pass
+
+
+def backup_root():
+    return Path(os.environ.get('FRAME_BACKUP_DIR') or Path.home() / 'Documents' / 'Frame Control Backups')
+
+
+def backup_path(name):
+    """The folder for a backup name; refuses anything that isn't one of ours."""
+    if not isinstance(name, str) or not NAME.fullmatch(name):
+        raise BackupError('not a backup name')
+    root = backup_root().resolve()
+    path = (root / name).resolve()
+    if path.parent != root:
+        raise BackupError('not a backup name')
+    return path
+
+
+def archive_name(part):
+    kind, _, rest = part.partition(':')
+    return '%s/%s.tar.gz' % (kind, rest if kind == 'android' else part.replace(':', '-'))
+
+
+def remote_command(cmd, *args):
+    return shlex.join(['python3', '-c', REMOTE.read_text(), cmd, *args])
+
+
+def _ssh(command, src=None, dst=None, timeout=1800):
+    try:
+        # src: bytes, or a file to stream (an archive can be larger than memory).
+        feed = {'input': src} if isinstance(src, bytes) else {
+            'stdin': src if src is not None else subprocess.DEVNULL}
+        result = frame_host.run_ssh(['ssh', *android.SSH_OPTS, android.FRAME, command], **feed,
+                                    stdout=dst if dst is not None else subprocess.PIPE,
+                                    stderr=subprocess.PIPE, timeout=timeout)
+    except subprocess.TimeoutExpired:
+        raise BackupError('the headset took too long to answer')
+    except OSError as error:
+        raise BackupError('could not reach the headset: ' + str(error))
+    if result.returncode:
+        raise BackupError(result.stderr.decode(errors='replace').strip()[-600:] or
+                          'the headset command failed')
+    return result.stdout
+
+
+def remote_json(cmd, *args, src=None, timeout=120):
+    out = _ssh(remote_command(cmd, *args), src=src, timeout=timeout)
+    try:
+        return json.loads(out)
+    except (ValueError, TypeError):
+        raise BackupError('unexpected answer from the headset')
+
+
+def _sha256(path):
+    digest = hashlib.sha256()
+    with open(str(path), 'rb') as src:
+        for chunk in iter(lambda: src.read(1024 * 1024), b''):
+            digest.update(chunk)
+    return digest.hexdigest()
+
+
+def inspect_archive(path):
+    """Every file in one of our part archives, with its size and SHA-256; refuses anything else."""
+    files, names = [], set()
+    try:
+        with tarfile.open(str(path), 'r:gz') as archive:
+            for member in archive:
+                name = member.name
+                parts = name.split('/')
+                if (not member.isfile() or name.startswith('/') or '\\' in name or name in names
+                        or any(p in ('', '.', '..') for p in parts)):
+                    raise BackupError('backup archive has an unsafe entry: %r' % name[:200])
+                names.add(name)
+                digest = hashlib.sha256()
+                src = archive.extractfile(member)
+                for chunk in iter(lambda: src.read(1024 * 1024), b''):
+                    digest.update(chunk)
+                files.append({'path': name, 'bytes': member.size, 'sha256': digest.hexdigest()})
+    except (OSError, EOFError, tarfile.TarError) as error:
+        raise BackupError('could not read the backup archive: ' + str(error))
+    return files
+
+
+def preview():
+    """What a backup would hold, before making one."""
+    plan = remote_json('plan')
+    apps, error = _android_apps()
+    return {'build': plan.get('build'), 'version': plan.get('version'), 'parts': plan.get('parts', []),
+            'android': apps, 'android_error': error, 'excluded': plan.get('excluded', []), 'folder': str(backup_root())}
+
+
+def _android_apps():
+    """(installed Android apps, None) or ([], why they couldn't be listed)."""
+    try:
+        return [{'package': a['package'], 'label': a.get('label') or a['package'],
+                 'running': bool(a.get('running'))} for a in android.list_apps()], None
+    except android.FrameError as error:
+        return [], str(error)
+
+
+def backup(report=lambda stage, percent=None: None, kinds=KINDS, headset=None):
+    kinds = [k for k in KINDS if k in kinds]
+    if not kinds:
+        raise BackupError('choose something to back up')
+    report('Reading what is on the headset', 1)
+    plan = remote_json('plan')
+    parts = [p for p in plan.get('parts', []) if p.get('kind') in kinds and PART.fullmatch(str(p.get('id')))]
+    apps, error = _android_apps() if 'android' in kinds else ([], None)
+    root = backup_root()
+    root.mkdir(parents=True, exist_ok=True)
+    name = time.strftime('%Y-%m-%d-%H%M%S')
+    final = backup_path(name)
+    if final.exists():
+        raise BackupError('a backup was started this second already; try again')
+    # Built under a hidden name and renamed when complete, so a cut-off backup is never listed.
+    staging = root / ('.' + name + '.partial')
+    staging.mkdir()
+    entries = []
+    skipped = [{'id': 'android', 'label': 'Android apps', 'reason': error}] if error else []
+    total = len(parts) + len(apps) or 1
+    try:
+        for i, part in enumerate(parts):
+            report('Copying ' + part['label'], 2 + 90 * i / total)
+            rel = archive_name(part['id'])
+            dest = staging / rel
+            dest.parent.mkdir(parents=True, exist_ok=True)
+            with open(str(dest), 'wb') as dst:
+                _ssh(remote_command('pack', part['id']), dst=dst)
+            files = inspect_archive(dest)
+            entries.append({'id': part['id'], 'kind': part['kind'], 'label': part['label'],
+                            'appid': part.get('appid'), 'archive': rel, 'sha256': _sha256(dest),
+                            'archive_bytes': dest.stat().st_size, 'files': files,
+                            'bytes': sum(f['bytes'] for f in files)})
+            skipped += [{'id': part['id'], 'label': part['label'], 'path': s['path'], 'reason': s['reason']}
+                        for s in part.get('skipped', [])]
+        for j, app in enumerate(apps):
+            report('Copying ' + app['label'] + ' (Android app data)', 2 + 90 * (len(parts) + j) / total)
+            part_id = 'android:' + app['package']
+            if app['running']:
+                skipped.append({'id': part_id, 'label': app['label'], 'reason': 'It was open; close it and back up again'})
+                continue
+            rel = archive_name(part_id)
+            dest = staging / rel
+            dest.parent.mkdir(parents=True, exist_ok=True)
+            try:
+                result = android.backup_data(app['package'], dest)
+            except android.FrameError as error:
+                skipped.append({'id': part_id, 'label': app['label'], 'reason': str(error)})
+                continue
+            entries.append({'id': part_id, 'kind': 'android', 'label': app['label'] + ' (Android app data)',
+                            'package': app['package'], 'instance': result.get('instance'), 'archive': rel,
+                            'sha256': result['sha256'], 'archive_bytes': dest.stat().st_size,
+                            'files': result.get('files'), 'bytes': result.get('bytes')})
+        report('Writing the manifest', 95)
+        manifest = {'format': FORMAT, 'app': 'Frame Control', 'name': name,
+                    'created': time.strftime('%Y-%m-%dT%H:%M:%S%z'),
+                    'headset': {'name': headset or android.FRAME, 'build': plan.get('build'),
+                                'version': plan.get('version')},
+                    'parts': entries, 'skipped': skipped, 'excluded': plan.get('excluded', [])}
+        (staging / 'manifest.json').write_text(json.dumps(manifest, indent=1))
+        os.rename(str(staging), str(final))
+    except BaseException:
+        shutil.rmtree(str(staging), ignore_errors=True)
+        raise
+    size = sum(e['archive_bytes'] for e in entries)
+    message = 'Backed up %d part%s (%s) to %s' % (len(entries), '' if len(entries) == 1 else 's',
+                                                   human(size), final)
+    if skipped:
+        message += '; %d skipped' % len(skipped)
+    return {'message': message, 'name': name, 'path': str(final), 'parts': len(entries),
+            'bytes': size, 'skipped': skipped}
+
+
+def human(n):
+    for unit in ('bytes', 'KB', 'MB', 'GB'):
+        if n < 1000 or unit == 'GB':
+            return ('%d %s' % (n, unit)) if unit == 'bytes' else '%.1f %s' % (n, unit)
+        n /= 1000.0
+
+
+def read_manifest(name):
+    path = backup_path(name)
+    try:
+        manifest = json.loads((path / 'manifest.json').read_text())
+    except (OSError, ValueError):
+        raise BackupError('that backup has no readable manifest')
+    if not isinstance(manifest, dict) or manifest.get('format') != FORMAT or \
+            not isinstance(manifest.get('parts'), list):
+        raise BackupError('that backup was made by a newer or unknown version')
+    for part in manifest['parts']:
+        if (not isinstance(part, dict) or not PART.fullmatch(str(part.get('id'))) or
+                not ARCHIVE.fullmatch(str(part.get('archive'))) or part['archive'] != archive_name(part['id'])):
+            raise BackupError('that backup manifest lists something unexpected')
+    return path, manifest
+
+
+def list_backups():
+    root = backup_root()
+    out = []
+    try:
+        names = sorted((p.name for p in root.iterdir() if NAME.fullmatch(p.name) and p.is_dir()), reverse=True)
+    except OSError:
+        names = []
+    for name in names:
+        try:
+            _, m = read_manifest(name)
+        except BackupError as error:
+            out.append({'name': name, 'error': str(error)})
+            continue
+        out.append({'name': name, 'created': m.get('created'), 'build': (m.get('headset') or {}).get('build'),
+                    'headset': (m.get('headset') or {}).get('name'), 'parts': len(m['parts']),
+                    'bytes': sum(p.get('archive_bytes') or 0 for p in m['parts'])})
+    return {'backups': out, 'folder': str(root)}
+
+
+def restore_plan(name):
+    """Each part of a backup and whether it can go back now; reads only."""
+    path, manifest = read_manifest(name)
+    plans, check = {}, []
+    for part in manifest['parts']:
+        archive = path / part['archive']
+        state = None
+        if not archive.is_file():
+            state = 'missing'
+        elif _sha256(archive) != part.get('sha256'):
+            state = 'damaged'
+        plans[part['id']] = {'id': part['id'], 'kind': part.get('kind'), 'label': part.get('label'),
+                             'bytes': part.get('bytes'), 'status': state}
+        if state is None and part['kind'] != 'android':
+            check.append({'id': part['id'], 'files': [f['path'] for f in part.get('files') or []]})
+    if check:
+        answer = remote_json('check', src=json.dumps({'parts': check}).encode())
+        for result in answer.get('parts', []):
+            plan = plans.get(result.get('id'))
+            if plan:
+                plan.update(status=result.get('status'), replace=result.get('replace', 0),
+                            new=result.get('new', 0), held=result.get('held', {}))
+    android_parts = [p for p in plans.values() if p['kind'] == 'android' and p['status'] is None]
+    if android_parts:
+        installed = {a['package']: a for a in android.list_apps()}
+        for plan in android_parts:
+            app = installed.get(plan['id'].split(':', 1)[1])
+            plan['status'] = 'not_installed' if not app else 'running' if app.get('running') else 'ok'
+            if plan['status'] == 'not_installed':
+                plan['reason'] = 'Install the app first, then restore its data'
+            elif plan['status'] == 'ok':
+                plan['replace'] = 1  # the app's whole private data folder, kept beside it
+    for plan in plans.values():
+        plan.setdefault('reason', REASONS.get(plan['status']) if plan['status'] != 'ok' else None)
+    return {'name': name, 'headset': manifest.get('headset'), 'parts': list(plans.values())}
+
+
+def restore(name, ids, confirmed=False, report=lambda stage, percent=None: None):
+    """Restore the chosen parts that can go back now; the rest are skipped, not failed."""
+    if not isinstance(ids, list) or not ids or not all(isinstance(i, str) and PART.fullmatch(i) for i in ids):
+        raise BackupError('choose what to restore')
+    if confirmed is not True:
+        raise BackupError('confirm the restore first: it replaces files on the headset')
+    path, manifest = read_manifest(name)
+    by_id = {p['id']: p for p in manifest['parts']}
+    plan = {p['id']: p for p in restore_plan(name)['parts']}
+    stamp = time.strftime('%Y%m%d-%H%M%S')
+    done, skipped = [], []
+    for i, part_id in enumerate(ids):
+        part, state = by_id.get(part_id), plan.get(part_id)
+        if not part or not state:
+            skipped.append({'id': part_id, 'reason': 'Not in this backup'})
+            continue
+        if state['status'] != 'ok':
+            skipped.append({'id': part_id, 'label': state['label'], 'reason': state.get('reason') or state['status']})
+            continue
+        report('Restoring ' + state['label'], 5 + 90 * i / len(ids))
+        archive = path / part['archive']
+        try:
+            if part['kind'] == 'android':
+                result = android.restore_data(part_id.split(':', 1)[1], str(archive))
+            else:
+                with open(str(archive), 'rb') as src:
+                    result = remote_json('restore', part_id, stamp, src=src, timeout=1800)
+        except android.FrameError as error:
+            skipped.append({'id': part_id, 'label': state['label'], 'reason': str(error)})
+            continue
+        done.append(dict(result, id=part_id, label=state['label']))
+    message = 'Restored %d part%s' % (len(done), '' if len(done) == 1 else 's')
+    if skipped:
+        message += ', skipped %d' % len(skipped)
+    return {'message': message, 'restored': done, 'skipped': skipped}
+
+
+# ---- Game Mode ---------------------------------------------------------------
+
+def session_status():
+    return remote_json('session', timeout=30)
+
+
+def session_command(selector):
+    """The switch to Game Mode, exactly as Valve's devkit tools run it."""
+    if selector not in SELECTORS:
+        raise BackupError('this SteamOS build has no session switch command; use the steps in the guide')
+    return shlex.join([selector, 'gamescope'])
+
+
+def return_to_game_mode(confirmed=False):
+    if confirmed is not True:
+        raise BackupError('confirm first: switching closes the desktop and any apps open in it')
+    state = session_status()
+    if state.get('mode') == 'game':
+        return {'message': 'The headset is already in Game Mode. The desktop you see is a panel: '
+                           'close it from the Steam dashboard.', 'state': state, 'switched': False}
+    command = session_command(state.get('selector'))
+    try:
+        # The session restarts under it, so the command may not get to answer.
+        _ssh(command, timeout=60)
+    except BackupError as error:
+        if 'took too long' not in str(error):
+            raise BackupError('the switch was refused: %s. Use the manual steps in the guide.' % error)
+    return {'message': 'Asked the headset to return to Game Mode; it restarts its session in a few seconds',
+            'state': state, 'switched': True, 'command': command}
+
+
+def main():
+    cmd, *args = sys.argv[1:] or ['help']
+    try:
+        if cmd == 'backup':
+            r = backup(lambda stage, percent=None: print(stage, file=sys.stderr))
+        elif cmd == 'list':
+            r = list_backups()
+        elif cmd == 'plan' and len(args) == 1:
+            r = restore_plan(args[0])
+        elif cmd == 'restore' and len(args) >= 2:
+            r = restore(args[0], args[1:], confirmed=True)
+        elif cmd == 'session':
+            r = session_status()
+        elif cmd == 'game-mode':
+            r = return_to_game_mode(confirmed=True)
+        else:
+            print(__doc__.strip().splitlines()[-1], file=sys.stderr)
+            return 2
+    except android.FrameError as error:
+        print('error:', error, file=sys.stderr)
+        return 1
+    print(json.dumps(r, indent=1))
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main())
diff --git a/ui/frame_backup_remote.py b/ui/frame_backup_remote.py
new file mode 100644
index 0000000..150f282
--- /dev/null
+++ b/ui/frame_backup_remote.py
@@ -0,0 +1,438 @@
+"""Backup and restore on the Frame: what to save, packing it and putting it back. Stdlib only.
+
+Runs on the headset as `python3 -c <this file> <command> ...` (ui/frame_backup.py sends it),
+so stdin is free for the archive or file list. Commands:
+
+  plan                 JSON: the headset's build and every part worth saving, with sizes
+  pack PART            a tar.gz of that part's files on stdout (reads only)
+  check                stdin JSON {"parts": [{"id", "files": [paths]}]}: what a restore would do
+  restore PART STAMP   stdin tar.gz: write that part's restorable files, keeping replaced ones
+  session              JSON: Game Mode or Desktop Mode, and the switch command on this image
+
+Paths are relative to the home folder, with '/' separators, everywhere: in archives, in the
+manifest and in `check`. Nothing here deletes a file. `restore` replaces only files named in
+its archive, and first copies each one it replaces under PREVIOUS/<stamp>/.
+"""
+import hashlib
+import json
+import os
+from pathlib import Path, PurePosixPath
+import re
+import shutil
+import subprocess
+import sys
+import tarfile
+import tempfile
+
+# FRAME_BACKUP_HOME: the tests point this at a folder laid out like the Frame's home.
+HOME = Path(os.environ.get('FRAME_BACKUP_HOME') or Path.home())
+STEAM = '.local/share/Steam'
+COMPAT = STEAM + '/steamapps/compatdata'
+PREFIX_USER = 'pfx/drive_c/users/steamuser'
+# Where Windows games keep saves inside a Proton prefix. Steam Cloud covers many games, not all.
+SAVE_DIRS = ('AppData/Roaming', 'AppData/Local', 'AppData/LocalLow', 'Documents', 'Saved Games')
+# Wine's and Windows' own folders inside those: caches, not saves.
+SAVE_SKIP = ('AppData/Local/Temp', 'AppData/Local/Microsoft', 'AppData/Roaming/Microsoft',
+             'AppData/Local/D3DSCache', 'AppData/Local/NVIDIA', 'AppData/Local/CrashDumps',
+             'AppData/LocalLow/Microsoft')
+# Native Linux games: the engines' standard save folders.
+LINUX_SAVES = ('.config/unity3d', '.local/share/godot/app_userdata')
+# Steam settings. Controller layouts go back; the rest is kept so you can look things up.
+STEAM_RESTORE = ('241100/remote/controller_config',)  # under userdata/<account>/
+STEAM_REFERENCE = ('config/localconfig.vdf', 'config/shortcuts.vdf', 'config/grid')
+STEAM_CONTROLLER = STEAM + '/steamapps/common/Steam Controller Configs'  # <account>/config/
+# Desktop settings worth keeping. Steam rewrites steamvr.vrsettings while SteamVR runs, so
+# it's only for reference.
+SYSTEM_RESTORE = ('.config/kdeglobals', '.config/kwinrc', '.config/kxkbrc', '.config/konsolerc',
+                  '.config/dolphinrc')
+SYSTEM_REFERENCE = ('.config/openvr/config/steamvr.vrsettings',)
+PREVIOUS = '.local/share/frame-control/restore-previous'
+MAX_FILE = 2 * 1024 ** 3      # a bigger "save" is a cache or a video; listed as skipped
+MAX_PART = 20 * 1024 ** 3
+MAX_FILES = 100000
+SHORTCUT_IDS = 2 ** 31        # non-Steam shortcuts and Lepton instances use ids above this
+
+# Never copied, whatever folder they turn up in. Checked on every path, packing and restoring.
+SECRET_NAMES = {'steam.token', 'loginusers.vdf', 'registry.vdf', 'config.vdf', 'secrets.env',
+                'authorized_keys', 'known_hosts', 'credentials', 'credentials.json'}
+SECRET_DIRS = {'.ssh', '.gnupg', '.pki', 'keyrings', 'kwalletd', 'cliproxyapi', 'tailscale'}
+SECRET_SUFFIXES = ('.token', '.pem', '.key', '.kwl')
+EXCLUDED = [
+    'Steam sign-in: steam.token, config/config.vdf, loginusers.vdf, registry.vdf, ssfn files',
+    'Keys and passwords: ~/.ssh, ~/.gnupg, keyrings and KWallet, *.token/*.key/*.pem files, '
+    'Tailscale and proxy settings (secrets.env)',
+    'Games themselves, Proton and runtimes (reinstall them from Steam), shader caches, Steam '
+    'Cloud folders under userdata/<account>/<appid>, screenshots (Tools → Capture & Live saves them)',
+    'Android apps themselves and their shared storage (/sdcard); only private app data is saved',
+    'Symbolic links, and single files over 2 GiB',
+]
+
+
+def is_secret(rel):
+    parts = PurePosixPath(rel).parts
+    name = parts[-1].lower() if parts else ''
+    return (name in SECRET_NAMES or name.startswith('ssfn') or name.startswith('id_rsa') or
+            name.startswith('id_ed25519') or name.startswith('id_ecdsa') or
+            name.endswith(SECRET_SUFFIXES) or any(p.lower() in SECRET_DIRS for p in parts[:-1]))
+
+
+def safe_rel(rel):
+    """A relative '/' path with no '..', '.', empty or absolute parts."""
+    if not isinstance(rel, str) or not rel or '\\' in rel or '\0' in rel or rel.startswith('/'):
+        return False
+    parts = rel.split('/')
+    return all(p not in ('', '.', '..') for p in parts) and not re.match(r'^[A-Za-z]:', rel)
+
+
+def _under(rel, root):
+    return rel == root or rel.startswith(root + '/')
+
+
+def _walk(rel_root, skip=()):
+    """Regular files under HOME/rel_root, never following links: [(rel, size)], [skipped]."""
+    files, skipped = [], []
+    base = HOME / rel_root
+    if base.is_symlink() or not base.is_dir():
+        if base.is_file() and not base.is_symlink():
+            return [(rel_root, base.stat().st_size)], skipped
+        return files, skipped
+    for top, dirs, names in os.walk(str(base)):
+        rel_top = PurePosixPath(rel_root, *Path(top).relative_to(base).parts).as_posix()
+        dirs[:] = sorted(d for d in dirs if not os.path.islink(os.path.join(top, d)) and
+                         not any(_under(rel_top + '/' + d, s) for s in skip) and
+                         not is_secret(rel_top + '/' + d + '/x'))
+        for name in sorted(names):
+            path, rel = os.path.join(top, name), rel_top + '/' + name
+            if os.path.islink(path) or is_secret(rel):
+                continue
+            try:
+                st = os.lstat(path)
+            except OSError:
+                continue
+            if not os.path.isfile(path):
+                continue
+            if st.st_size > MAX_FILE:
+                skipped.append({'path': rel, 'reason': 'over 2 GiB'})
+                continue
+            files.append((rel, st.st_size))
+    return files, skipped
+
+
+def _manifest_field(text, key):
+    m = re.search(r'"%s"\s+"([^"]*)"' % key, text)
+    return m.group(1) if m else None
+
+
+def game_name(appid):
+    try:
+        text = (HOME / STEAM / 'steamapps' / ('appmanifest_%s.acf' % appid)).read_text(errors='replace')
+    except OSError:
+        return None
+    return _manifest_field(text, 'name')
+
+
+def accounts():
+    root = HOME / STEAM / 'userdata'
+    try:
+        return sorted(p.name for p in root.iterdir() if p.name.isdigit() and p.is_dir()
+                      and not p.is_symlink() and p.name != '0')
+    except OSError:
+        return []
+
+
+def _prefixes():
+    try:
+        return sorted((p.name for p in (HOME / COMPAT).iterdir()
+                       if p.name.isdigit() and (p / PREFIX_USER).is_dir()), key=int)
+    except OSError:
+        return []
+
+
+def part_roots(part):
+    """(roots to save, roots that a restore may write) for a part id, or None if unknown."""
+    if part.startswith('saves:') and part[6:].isdigit():
+        user = '%s/%s/%s' % (COMPAT, part[6:], PREFIX_USER)
+        roots = tuple(user + '/' + d for d in SAVE_DIRS)
+        return roots, roots
+    if part == 'saves:linux':
+        return LINUX_SAVES, LINUX_SAVES
+    if part == 'settings:steam':
+        save, restore = [], []
+        for acct in accounts():
+            base = '%s/userdata/%s/' % (STEAM, acct)
+            restore += [base + r for r in STEAM_RESTORE] + ['%s/%s/config' % (STEAM_CONTROLLER, acct)]
+            save += [base + r for r in STEAM_REFERENCE]
+        return tuple(save + restore), tuple(restore)
+    if part == 'settings:system':
+        return SYSTEM_RESTORE + SYSTEM_REFERENCE, SYSTEM_RESTORE
+    return None
+
+
+def restore_roots(part, rel):
+    """The restore roots for rel within part; the Steam ones don't depend on today's accounts."""
+    if part == 'settings:steam':
+        m = re.match(r'^(?:%s/userdata/(\d+)/|%s/(\d+)/)' % (re.escape(STEAM), re.escape(STEAM_CONTROLLER)), rel)
+        acct = m and (m.group(1) or m.group(2))
+        if not acct:
+            return ()
+        base = '%s/userdata/%s/' % (STEAM, acct)
+        return tuple(base + r for r in STEAM_RESTORE) + ('%s/%s/config' % (STEAM_CONTROLLER, acct),)
+    roots = part_roots(part)
+    return roots[1] if roots else ()
+
+
+def part_files(part):
+    roots = part_roots(part)
+    if roots is None:
+        raise ValueError('unknown backup part %r' % part)
+    skip = ()
+    if part.startswith('saves:') and part != 'saves:linux':
+        skip = tuple('%s/%s/%s/%s' % (COMPAT, part[6:], PREFIX_USER, s) for s in SAVE_SKIP)
+    files, skipped = [], []
+    for root in roots[0]:
+        f, s = _walk(root, skip)
+        files += f
+        skipped += s
+    return files, skipped
+
+
+def part_label(part):
+    if part == 'saves:linux':
+        return 'Linux game saves (Unity and Godot games)'
+    if part == 'settings:steam':
+        return 'Steam settings and controller layouts'
+    if part == 'settings:system':
+        return 'Desktop and SteamVR settings'
+    appid = part[6:]
+    name = game_name(appid)
+    if name:
+        return name + ' saves'
+    return ('Non-Steam game %s saves' if int(appid) >= SHORTCUT_IDS else 'Game %s saves') % appid
+
+
+def plan():
+    parts = []
+    ids = ['saves:' + a for a in _prefixes()] + ['saves:linux', 'settings:steam', 'settings:system']
+    for part in ids:
+        files, skipped = part_files(part)
+        if not files:
+            continue
+        parts.append({'id': part, 'kind': part.split(':')[0], 'label': part_label(part),
+                      'files': len(files), 'bytes': sum(s for _, s in files), 'skipped': skipped,
+                      'appid': part[6:] if part[6:].isdigit() else None,
+                      'restorable': sum(1 for rel, _ in files
+                                        if any(_under(rel, r) for r in restore_roots(part, rel)))})
+    return {'build': os_release().get('BUILD_ID'), 'version': os_release().get('VERSION_ID'),
+            'parts': parts, 'excluded': EXCLUDED}
+
+
+def os_release():
+    out = {}
+    try:
+        for line in Path(os.environ.get('FRAME_BACKUP_OS_RELEASE') or '/etc/os-release').read_text().splitlines():
+            k, _, v = line.partition('=')
+            out[k.strip()] = v.strip().strip('"')
+    except OSError:
+        pass
+    return out
+
+
+def pack(part, output):
+    files, _ = part_files(part)
+    if len(files) > MAX_FILES or sum(s for _, s in files) > MAX_PART:
+        raise ValueError('this part is too big to back up (over 100,000 files or 20 GiB)')
+    with tarfile.open(fileobj=output, mode='w|gz') as archive:
+        for rel, _ in files:
+            path = HOME / rel
+            try:
+                with open(str(path), 'rb') as src:
+                    st = os.fstat(src.fileno())
+                    member = tarfile.TarInfo(rel)
+                    member.size, member.mtime, member.mode = st.st_size, int(st.st_mtime), st.st_mode & 0o755
+                    archive.addfile(member, src)
+            except OSError:
+                continue  # gone since the walk (a game wrote it); the manifest lists what's in the archive
+
+
+def target_status(part, rel):
+    """None if rel may be restored now, else why not (a short code)."""
+    if is_secret(rel) or not safe_rel(rel):
+        return 'refused'
+    if not any(_under(rel, r) for r in restore_roots(part, rel)):
+        return 'reference'
+    if part.startswith('saves:') and part != 'saves:linux':
+        appid = part[6:]
+        if int(appid) < SHORTCUT_IDS and \
+                not (HOME / STEAM / 'steamapps' / ('appmanifest_%s.acf' % appid)).is_file():
+            return 'not_installed'
+        if not (HOME / COMPAT / appid / PREFIX_USER).is_dir():
+            return 'no_prefix'
+    if part == 'settings:steam':
+        acct = re.search(r'/(\d+)/', rel[len(STEAM):])
+        if not acct or not (HOME / STEAM / 'userdata' / acct.group(1)).is_dir():
+            return 'no_account'
+    # A link anywhere on the way could send the write somewhere else.
+    path = HOME
+    for p in rel.split('/')[:-1]:
+        path = path / p
+        if path.is_symlink() or (path.exists() and not path.is_dir()):
+            return 'refused'
+    if (HOME / rel).is_symlink() or ((HOME / rel).exists() and not (HOME / rel).is_file()):
+        return 'refused'
+    return None
+
+
+def check(request):
+    out = []
+    for item in request.get('parts', []):
+        part, files = item.get('id'), item.get('files') or []
+        if not isinstance(part, str) or part_roots(part) is None:
+            out.append({'id': part, 'status': 'unknown'})
+            continue
+        counts = {}
+        replace = new = 0
+        for rel in files:
+            why = target_status(part, rel)
+            if why:
+                counts[why] = counts.get(why, 0) + 1
+            elif (HOME / rel).exists():
+                replace += 1
+            else:
+                new += 1
+        status = 'ok' if replace + new else next(
+            (c for c in ('not_installed', 'no_prefix', 'no_account', 'reference', 'refused') if c in counts), 'empty')
+        out.append({'id': part, 'status': status, 'replace': replace, 'new': new, 'held': counts})
+    return {'parts': out}
+
+
+def _sha256(path):
+    digest = hashlib.sha256()
+    with open(str(path), 'rb') as src:
+        for chunk in iter(lambda: src.read(1024 * 1024), b''):
+            digest.update(chunk)
+    return digest.hexdigest()
+
+
+def restore(part, stamp, source):
+    if part_roots(part) is None:
+        raise ValueError('unknown backup part %r' % part)
+    if not re.fullmatch(r'\d{8}-\d{6}', stamp):
+        raise ValueError('bad restore stamp')
+    # Spool first: everything is checked before anything is written.
+    spool_dir = HOME / '.cache/frame-control'
+    spool_dir.mkdir(parents=True, exist_ok=True)
+    written, replaced, held = [], [], {}
+    with tempfile.TemporaryDirectory(prefix='restore-', dir=str(spool_dir)) as tmp:
+        spool = Path(tmp) / 'part.tar.gz'
+        with open(str(spool), 'wb') as dst:
+            shutil.copyfileobj(source, dst, 1024 * 1024)
+        todo, names, total = [], set(), 0
+        with tarfile.open(str(spool), 'r:gz') as archive:
+            for member in archive:
+                if not member.isfile() or not safe_rel(member.name) or member.name in names:
+                    raise ValueError('backup has an unsafe, duplicate or non-file entry: %r' % member.name[:200])
+                names.add(member.name)
+                total += member.size
+                if len(names) > MAX_FILES or total > MAX_PART:
+                    raise ValueError('backup part is too big')
+                why = target_status(part, member.name)
+                if why:
+                    held[why] = held.get(why, 0) + 1
+                else:
+                    todo.append(member.name)
+        previous = HOME / PREVIOUS / stamp
+        keep = set(todo)
+        with tarfile.open(str(spool), 'r:gz') as archive:
+            for member in archive:
+                if member.name not in keep:
+                    continue
+                target = HOME / member.name
+                target.parent.mkdir(parents=True, exist_ok=True)
+                part_file = target.parent / ('.frame-restore-%d.part' % os.getpid())
+                with archive.extractfile(member) as src, open(str(part_file), 'wb') as dst:
+                    shutil.copyfileobj(src, dst, 1024 * 1024)
+                os.chmod(str(part_file), (member.mode & 0o755) | 0o600)
+                os.utime(str(part_file), (member.mtime, member.mtime))
+                if target.exists():
+                    if _sha256(target) == _sha256(part_file):
+                        os.unlink(str(part_file))
+                        held['same'] = held.get('same', 0) + 1
+                        continue
+                    keep_copy = previous / member.name
+                    keep_copy.parent.mkdir(parents=True, exist_ok=True)
+                    shutil.copy2(str(target), str(keep_copy))
+                    replaced.append(member.name)
+                os.replace(str(part_file), str(target))
+                written.append(member.name)
+    return {'id': part, 'written': len(written), 'replaced': len(replaced), 'held': held,
+            'previous': (PREVIOUS + '/' + stamp) if replaced else None}
+
+
+# ---- Game Mode and Desktop Mode --------------------------------------------
+#
+# The Frame normally runs gamescope (Game Mode) with Plasma nested inside it as one panel
+# (steamos-nested-desktop). A full Desktop Mode session is SDDM autologin into Plasma
+# instead. Valve's own devkit tools (frame/devkit-utils: steamos-get-status, steamos-delete)
+# read the session from these files and switch with holo-session-select or
+# steamos-session-select, so that's what this reads and suggests.
+
+SDDM_CONFS = ('/etc/sddm.conf.d/zz-steamos-autologin.conf', '/etc/sddm.conf.d/steamos.conf')
+
+
+def _running(name, full=False):
+    try:
+        return subprocess.call(['pgrep', '-f' if full else '-x', name], stdout=subprocess.DEVNULL,
+                               stderr=subprocess.DEVNULL) == 0
+    except OSError:
+        return False
+
+
+def session():
+    configured, conf = None, None
+    for path in SDDM_CONFS:
+        try:
+            text = Path(path).read_text(errors='replace')
+        except OSError:
+            continue
+        m = re.search(r'^\s*Session\s*=\s*(\S+)', text, re.M)
+        conf, configured = path, (m.group(1) if m else None)
+        break
+    selector = next((s for s in ('holo-session-select', 'steamos-session-select') if shutil.which(s)), None)
+    gamescope, plasma = _running('gamescope'), _running('plasmashell')
+    nested = _running('steamos-nested-desktop', full=True)  # a script: its process name is the shell's
+    if gamescope:
+        mode = 'game'
+    elif plasma or (configured and 'plasma' in configured):
+        mode = 'desktop'
+    else:
+        mode = 'unknown'
+    return {'mode': mode, 'gamescope': gamescope, 'plasma': plasma, 'nested_desktop': nested,
+            'configured': configured, 'config_file': conf, 'selector': selector}
+
+
+def main(argv):
+    cmd, args = (argv[0] if argv else ''), argv[1:]
+    try:
+        if cmd == 'plan':
+            print(json.dumps(plan()))
+        elif cmd == 'pack' and len(args) == 1:
+            out = sys.stdout.buffer
+            pack(args[0], out)
+            out.flush()
+        elif cmd == 'check':
+            print(json.dumps(check(json.load(sys.stdin))))
+        elif cmd == 'restore' and len(args) == 2:
+            print(json.dumps(restore(args[0], args[1], sys.stdin.buffer)))
+        elif cmd == 'session':
+            print(json.dumps(session()))
+        else:
+            sys.stderr.write('usage: plan | pack PART | check | restore PART STAMP | session\n')
+            return 2
+    except (OSError, ValueError, tarfile.TarError) as error:
+        sys.stderr.write(str(error) + '\n')
+        return 1
+    return 0
+
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv[1:]))
diff --git a/ui/index.html b/ui/index.html
index 4b374cf..53c75ad 100644
--- a/ui/index.html
+++ b/ui/index.html
@@ -1412,7 +1412,7 @@
 
   <div class="page" data-page="tools">
 <div class="workspace-heading"><div><a href="#tools" id="toolBack" class="workspace-link" hidden>← All tools</a><h1 id="toolTitle">Tools</h1><p id="toolSubtitle">Choose a task for your Frame.</p></div></div>
-<div id="toolDirectory"><section class="tool-group"><h2>Content & files</h2><div class="quick-routes"><a href="#transfer"><span>Send to Frame</span><small>Add files, APKs or your own games</small></a><a href="#media"><span>Media player</span><small>Play your own videos and media</small></a><a href="#linuxApps"><span>Linux apps</span><small>Install and manage desktop apps</small></a></div></section><section class="tool-group"><h2>Play & control</h2><div class="quick-routes"><a href="#capture"><span>Capture & Live</span><small>See and control the headset view</small></a><a href="#pad" title="Type on the headset (T)"><span>Type on the headset</span><small>Keyboard, trackpad and clipboard</small></a><a href="#panels"><span>Panel switcher</span><small>Bring an open panel into view</small></a><a href="#vrTools"><span>VR tools</span><small>Performance HUD and VR utilities</small></a><a href="#comfort"><span>Family & comfort</span><small>Session reminders and breaks</small></a><a href="#macview" id="macToolLink" hidden><span>Mac in the headset</span><small>Share Mac windows and displays</small></a></div></section><section class="tool-group"><h2>Your Frame</h2><a class="workspace-link" href="#settings">Connection, display &amp; preferences →</a></section><section class="tool-group"><h2>Assistant</h2><a class="workspace-link" href="/assistant">Open assistant &amp; AI agents →</a><p class="sub">Use your own model endpoint or review a proposed MCP action.</p></section></div>
+<div id="toolDirectory"><section class="tool-group"><h2>Content & files</h2><div class="quick-routes"><a href="#transfer"><span>Send to Frame</span><small>Add files, APKs or your own games</small></a><a href="#media"><span>Media player</span><small>Play your own videos and media</small></a><a href="#linuxApps"><span>Linux apps</span><small>Install and manage desktop apps</small></a></div></section><section class="tool-group"><h2>Play & control</h2><div class="quick-routes"><a href="#capture"><span>Capture & Live</span><small>See and control the headset view</small></a><a href="#pad" title="Type on the headset (T)"><span>Type on the headset</span><small>Keyboard, trackpad and clipboard</small></a><a href="#panels"><span>Panel switcher</span><small>Bring an open panel into view</small></a><a href="#vrTools"><span>VR tools</span><small>Performance HUD and VR utilities</small></a><a href="#comfort"><span>Family & comfort</span><small>Session reminders and breaks</small></a><a href="#macview" id="macToolLink" hidden><span>Mac in the headset</span><small>Share Mac windows and displays</small></a></div></section><section class="tool-group"><h2>Your Frame</h2><div class="quick-routes"><a href="#backup" id="backupToolLink"><span>Backup &amp; recovery</span><small>Save games and settings, restore after a reset</small></a></div><a class="workspace-link" href="#settings">Connection, display &amp; preferences →</a></section><section class="tool-group"><h2>Assistant</h2><a class="workspace-link" href="/assistant">Open assistant &amp; AI agents →</a><p class="sub">Use your own model endpoint or review a proposed MCP action.</p></section></div>
   <div class="grid-3" id="toolWorkspace">
 <section class="panel" id="vrTools">
     <div class="shelf-head"><h2>VR comfort and performance</h2><span class="spacer"></span><span class="sub" id="vrUpdated">Waiting for the Frame</span></div>
@@ -1644,6 +1644,41 @@
         Saved spatial layouts are not available yet.</div>
     </section>
 
+    <section class="panel" id="backup" hidden>
+      <div class="shelf-head"><h2>Back up the Frame</h2><span class="spacer"></span>
+        <button class="small" id="backupFolder">Open backups folder</button></div>
+      <p class="sub">Copies game saves, settings and Android app data from the headset to a dated folder on this computer.
+        It only reads the headset. Games themselves aren't copied: reinstall them from Steam.</p>
+      <div class="chips" id="backupKinds">
+        <label><input type="checkbox" value="saves" checked> Game saves</label>
+        <label><input type="checkbox" value="settings" checked> Steam and desktop settings</label>
+        <label><input type="checkbox" value="android" checked> Android app data</label>
+      </div>
+      <div class="row" style="margin-top:12px"><button class="small" id="backupPreview">See what's included</button>
+        <button class="small action" id="backupStart">Back up now</button></div>
+      <div class="sub" id="backupProgress" role="status" aria-live="polite"></div>
+      <div class="list" id="backupSummary"></div>
+      <div class="hint">Never copied: Steam sign-in files (steam.token, config.vdf, loginusers.vdf), SSH keys,
+        keyrings and other passwords. Backups aren't encrypted, and game folders can hold launcher logins, so keep them private.
+        Close Android apps first: open ones are skipped.</div>
+
+      <div class="shelf-head" style="margin-top:20px"><h2>Restore</h2><span class="spacer"></span>
+        <button class="small" id="backupRefresh">Refresh</button></div>
+      <div class="list" id="backupList"><div class="sub">Open this tool to see your backups.</div></div>
+      <div id="restorePlan"></div>
+      <div class="hint">After a factory reset, sign in to Steam, reinstall your games and start each once, and reinstall
+        your Android apps. Then restore. Parts that can't go back yet are skipped, not failed. Files a restore replaces are
+        kept on the headset in ~/.local/share/frame-control/restore-previous.</div>
+
+      <div class="shelf-head" style="margin-top:20px"><h2>Stuck in Desktop Mode?</h2><span class="spacer"></span>
+        <button class="small" id="sessionCheck">Check</button></div>
+      <div class="sub" id="sessionState">Check which mode the headset is in.</div>
+      <div class="row" style="margin-top:12px"><button class="small" id="sessionGame" disabled>Return to Game Mode</button></div>
+      <div class="hint">Uses the same switch as Valve's developer tools (<code>steamos-session-select gamescope</code>).
+        It closes the desktop and anything open in it. If the headset can't be reached, hold Power for 10 seconds to
+        restart it; <a href="https://github.com/saphid/frame-control/blob/main/docs/backup-and-recovery.md#stuck-in-desktop-mode" target="_blank">more ways back</a>.</div>
+    </section>
+
     <section class="panel" id="macview" hidden>
       <div class="shelf-head"><h2>Mac in the headset</h2><span class="count" id="mvCount"></span><span class="spacer"></span>
         <button class="small" id="mvRefresh">Refresh</button></div>
@@ -5268,6 +5303,138 @@ $("panelList").onclick = e => {
   act("Show panel", () => api("/api/panels", {action: "focus", key: b.dataset.panel}), b);
 };
 
+// ---- Backup and recovery kit (ui/frame_backup.py) ----
+const BACKUP_KIND = {saves: "Game saves", settings: "Settings", android: "Android app data"};
+function sizeText(n) {
+  if (n == null) return "";
+  for (const unit of ["bytes", "KB", "MB", "GB"]) {
+    if (n < 1000 || unit === "GB") return unit === "bytes" ? `${n} bytes` : `${n.toFixed(1)} ${unit}`;
+    n /= 1000;
+  }
+}
+const backupKinds = () => [...$("backupKinds").querySelectorAll("input:checked")].map(i => i.value);
+let backupSeq = 0, backupBusy = false;
+async function loadBackups() {
+  const seq = ++backupSeq;
+  try {
+    const r = await api("/api/backup", {action: "list"});
+    if (seq !== backupSeq) return;
+    $("backupList").innerHTML = r.backups.length ? r.backups.map(b => `<div class="item"><div class="grow">
+        <div class="t">${esc(b.name)}</div><div class="s">${b.error ? esc(b.error) :
+        esc([b.headset, b.build && `SteamOS build ${b.build}`, `${b.parts} part${b.parts === 1 ? "" : "s"}`, sizeText(b.bytes)].filter(Boolean).join(" · "))}</div></div>
+        ${b.error ? "" : `<button class="small" data-backup-plan="${esc(b.name)}">Restore…</button>`}</div>`).join("")
+      : `<div class="sub">No backups in ${esc(r.folder)} yet.</div>`;
+  } catch (e) { if (seq === backupSeq) failed($("backupList"), e); }
+}
+function backupPartRow(p, restore) {
+  const detail = restore
+    ? (p.status === "ok" ? [p.replace ? `replaces ${p.replace} file${p.replace === 1 ? "" : "s"}` : "", p.new ? `${p.new} new` : "",
+                            p.held && p.held.reference ? `${p.held.reference} kept for reference` : ""].filter(Boolean).join(", ") || "ready"
+                         : p.reason || p.status)
+    : [`${p.files} file${p.files === 1 ? "" : "s"}`, sizeText(p.bytes), p.skipped && p.skipped.length ? `${p.skipped.length} too big, skipped` : ""].filter(Boolean).join(" · ");
+  const box = restore ? `<input type="checkbox" data-restore-part="${esc(p.id)}" ${p.status === "ok" ? "checked" : "disabled"} aria-label="Restore ${esc(p.label)}"> ` : "";
+  return `<div class="item"><div class="grow"><div class="t">${box}${esc(p.label)}</div><div class="s">${esc(detail)}</div></div></div>`;
+}
+$("backupPreview").onclick = e => act("Check what a backup includes", async () => {
+  const r = await api("/api/backup", {action: "preview"}), kinds = backupKinds();
+  const rows = r.parts.filter(p => kinds.includes(p.kind)).map(p => backupPartRow(p, false));
+  if (kinds.includes("android")) rows.push(...r.android.map(a => `<div class="item"><div class="grow"><div class="t">${esc(a.label)} (Android app data)</div>
+      <div class="s">${a.running ? "Open now: close it or it's skipped" : "Saved while closed"}</div></div></div>`));
+  if (r.android_error && kinds.includes("android")) rows.push(`<div class="sub">Android apps couldn't be listed: ${esc(r.android_error)}</div>`);
+  $("backupSummary").innerHTML = (rows.join("") || '<div class="sub">Nothing to back up for that choice.</div>') +
+    `<details><summary>Never copied</summary><ul>${r.excluded.map(x => `<li>${esc(x)}</li>`).join("")}</ul></details>`;
+  return {message: `SteamOS build ${r.build || "unknown"}: ${rows.length} part${rows.length === 1 ? "" : "s"} to back up`};
+}, e.currentTarget);
+// Like runJob, without counting as an install in the header.
+async function backupJob(label, start) {
+  log(label + "…");
+  try {
+    const { job } = await start();
+    for (let misses = 0; ;) {
+      await new Promise(ok => setTimeout(ok, 1500));
+      let j;
+      try { j = await api(`/api/job?id=${encodeURIComponent(job)}`); misses = 0; }
+      catch (e) { if (++misses >= 20 || /no such job/.test(e.message)) throw e; continue; }
+      backupProgress(j);
+      if (!j.done) continue;
+      if (j.error) throw new Error(j.error);
+      log(j.message, "ok"); toast(j.message);
+      return j.result || {};
+    }
+  } catch (e) {
+    log(`${label} failed: ${e.message}`, "e"); toast(`${label} failed: ${e.message}`, true);
+  }
+}
+function backupProgress(j) {
+  $("backupProgress").textContent = j.done ? "" : `${j.stage || "Starting"}${j.percent != null ? ` · ${Math.round(j.percent)}%` : ""}`;
+}
+$("backupStart").onclick = async e => {
+  const kinds = backupKinds();
+  if (!kinds.length) return toast("Choose something to back up", true);
+  if (backupBusy) return;
+  backupBusy = true; e.currentTarget.disabled = true;
+  try {
+    const r = await backupJob("Back up the Frame", () => api("/api/backup", {action: "backup", kinds}));
+    if (r) {
+      $("backupSummary").innerHTML = `<div class="sub">${esc(r.message)}</div>` + (r.skipped || []).map(s =>
+        `<div class="item"><div class="grow"><div class="t">${esc(s.label || s.id)}${s.path ? `: ${esc(s.path)}` : ""}</div>
+         <div class="s">Skipped: ${esc(s.reason)}</div></div></div>`).join("");
+      loadBackups();
+    }
+  } finally { backupBusy = false; $("backupStart").disabled = false; $("backupProgress").textContent = ""; }
+};
+$("backupFolder").onclick = e => act("Open backups folder", () => api("/api/backup", {action: "open"}), e.currentTarget);
+$("backupRefresh").onclick = loadBackups;
+let restoreName = null;
+$("backupList").onclick = async e => {
+  const b = e.target.closest("[data-backup-plan]"); if (!b) return;
+  restoreName = b.dataset.backupPlan;
+  $("restorePlan").innerHTML = '<div class="sub">Checking what can go back…</div>';
+  try {
+    const r = await api("/api/backup", {action: "plan", name: restoreName});
+    if (r.name !== restoreName) return;
+    $("restorePlan").innerHTML = `<h3>Restore ${esc(r.name)}</h3>` + r.parts.map(p => backupPartRow(p, true)).join("") +
+      `<div class="row" style="margin-top:12px"><button class="small danger" id="restoreStart">Restore selected</button>
+       <button class="small" data-backup-open="${esc(r.name)}">Show files</button></div>`;
+    $("restorePlan").plan = r;
+  } catch (err) { failed($("restorePlan"), err); }
+};
+$("restorePlan").onclick = async e => {
+  const open = e.target.closest("[data-backup-open]");
+  if (open) return act("Show backup files", () => api("/api/backup", {action: "open", name: open.dataset.backupOpen}), open);
+  if (!e.target.closest("#restoreStart") || backupBusy) return;
+  const plan = $("restorePlan").plan;
+  const parts = [...$("restorePlan").querySelectorAll("[data-restore-part]:checked")].map(i => i.dataset.restorePart);
+  if (!plan || !parts.length) return toast("Choose something to restore", true);
+  const chosen = plan.parts.filter(p => parts.includes(p.id));
+  const replacing = chosen.reduce((n, p) => n + (p.replace || 0), 0);
+  if (!confirm(`Restore ${chosen.length} part${chosen.length === 1 ? "" : "s"} from ${plan.name}?\n\n` +
+               `${replacing ? `This replaces ${replacing} file${replacing === 1 ? "" : "s"} or app data folder${replacing === 1 ? "" : "s"} on the headset. ` : ""}` +
+               "Replaced files are kept on the headset. Close the games and apps you're restoring first.")) return;
+  backupBusy = true;
+  try {
+    const r = await backupJob("Restore from backup", () => api("/api/backup", {action: "restore", name: plan.name, parts, confirm: true}));
+    if (r) $("restorePlan").innerHTML = `<div class="sub">${esc(r.message)}</div>` + (r.skipped || []).map(s =>
+      `<div class="item"><div class="grow"><div class="t">${esc(s.label || s.id)}</div><div class="s">Skipped: ${esc(s.reason)}</div></div></div>`).join("");
+  } finally { backupBusy = false; $("backupProgress").textContent = ""; }
+};
+const SESSION_TEXT = {game: "Game Mode: the headset is running normally. A desktop you see is a panel; close it from the Steam dashboard.",
+  desktop: "Desktop Mode: the headset started the full desktop instead of Game Mode.",
+  unknown: "Couldn't tell which mode the headset is in."};
+$("sessionCheck").onclick = async e => {
+  e.currentTarget.disabled = true;
+  try {
+    const s = await api("/api/backup", {action: "session"});
+    $("sessionState").textContent = SESSION_TEXT[s.mode] + (s.selector ? "" : " This SteamOS build has no session switch command; use the manual steps.");
+    $("sessionGame").disabled = s.mode === "game" || !s.selector;
+  } catch (err) { failed($("sessionState"), err); }
+  finally { $("sessionCheck").disabled = false; }
+};
+$("sessionGame").onclick = e => {
+  if (!confirm("Return the headset to Game Mode?\n\nThis closes the desktop and any apps open in it, then starts Steam's Game Mode.")) return;
+  act("Return to Game Mode", () => api("/api/backup", {action: "gamemode", confirm: true}), e.currentTarget);
+};
+
 // ---- Mac in the headset: windows and displays as panels (ui/frame_macview.py) ----
 let mvSeq = 0, mvTimer = 0;
 // streaming: the src it's shown as (a window may be "separate:<id>"), or "".
@@ -5381,10 +5548,10 @@ const PAGES = ["apps", "games", "tools", "settings"];
 const SECONDARY_PAGES = ["home", "capture", "devices", "control"];
 const SECTION_PAGE = {library:"games", discover:"apps", android:"apps", view:"capture", shots:"capture", device:"home",
   vrTools:"tools", comfort:"tools", assistant:"tools", pad:"tools", sideloaded:"games", getgames:"games", steamStore:"games", androidLibrary:"apps", appStore:"apps", linuxApps:"apps",
-  display:"settings", androidSettings:"settings", transfer:"tools", media:"tools", artworkSettings:"settings", power:"settings", macview:"tools", privacy:"settings", panels:"tools"};
+  display:"settings", androidSettings:"settings", transfer:"tools", media:"tools", artworkSettings:"settings", power:"settings", macview:"tools", privacy:"settings", panels:"tools", backup:"tools"};
 const TOOL_TITLES = {transfer:"Send to Frame", media:"Media player", artworkSettings:"Library artwork",
   pad:"Type on the headset", panels:"Panel switcher", vrTools:"VR tools", comfort:"Family & comfort", androidSettings:"App display & reports",
-  power:"Remote & power", macview:"Mac in the headset", privacy:"Privacy & updates"};
+  power:"Remote & power", macview:"Mac in the headset", privacy:"Privacy & updates", backup:"Backup & recovery"};
 const workspace = {source:"all", scope:"installed", apps:"installed", scroll:new Map(), key:null, hash:null, y:0};
 let page = "apps";
 // Reuse the existing live lists and form handlers in their new destinations.
@@ -5490,6 +5657,7 @@ function showPage(e) {
   }
   if (tool === 'macview') loadMacView();
   if (tool === 'panels') loadPanelSwitcher();
+  if (tool === 'backup') loadBackups();
   if (tool === 'androidSettings') {
     $('repNew').hidden = false; $('androidSettings').prepend($('repNew')); loadDisplays();
   }
@@ -6881,6 +7049,7 @@ api("/api/host").then(h => {
   Object.assign(HOST, h);
   window.frameControlCenter?.host(h);
   $("macToolLink").hidden = h.mobile || h.os !== "macOS";
+  $("backupToolLink").hidden = !!h.mobile;  // backups are folders on a computer
   if (h.mobile) return;
   $("offSetup").hidden = false; $("offSetup").onclick = setUpActive;  // the server opens it in a terminal
   watchConnection();
diff --git a/ui/server.py b/ui/server.py
index 432a241..7cc02fd 100755
--- a/ui/server.py
+++ b/ui/server.py
@@ -45,6 +45,7 @@ import frame_agent  # noqa: E402
 import frame_assistant  # noqa: E402
 import frame_android  # noqa: E402
 import frame_android_import  # noqa: E402
+import frame_backup  # noqa: E402
 from apk_sources import search as apk_search, SourceError  # noqa: E402
 from apk_sources import fdroid as apk_fdroid  # noqa: E402
 import frame_apk_versions  # noqa: E402
@@ -2609,6 +2610,73 @@ def panels_action(body):
     return result
 
 
+# ---- Backup and recovery kit (frame_backup.py) ------------------------------
+#
+# Backups are folders on this computer, so they run from the computer app only. One backup
+# or restore at a time: both are long jobs the page follows through /api/job.
+
+_backup_lock = threading.Lock()
+
+
+def backup_action(body):
+    action = body.get("action")
+    if LOCAL:
+        raise Failure("Backups are made from Frame Control on your computer", 400)
+    if action in ("plan", "restore") or (action == "open" and body.get("name") is not None):
+        try:
+            frame_backup.backup_path(body.get("name"))  # refused before anything reads or runs
+        except frame_backup.BackupError as e:
+            raise Failure(str(e), 400)
+    if action in ("gamemode", "restore") and body.get("confirm") is not True:
+        raise Failure("Confirm first: this changes the headset", 400)
+    if action == "list":
+        return frame_backup.list_backups()
+    if action == "preview":
+        return frame_backup.preview()
+    if action == "plan":
+        return frame_backup.restore_plan(body.get("name"))
+    if action == "session":
+        return frame_backup.session_status()
+    if action == "gamemode":
+        return frame_backup.return_to_game_mode(confirmed=True)
+    if action == "open":
+        folder = frame_backup.backup_root()
+        if body.get("name") is not None:
+            folder = frame_backup.backup_path(body.get("name"))
+        folder.mkdir(parents=True, exist_ok=True)
+        try:
+            frame_host.open_path(folder)
+        except frame_host.HostError as e:
+            raise Failure(str(e), 500)
+        return {"message": f"Opened {folder} in {frame_host.FILE_MANAGER}"}
+    if action == "backup":
+        kinds = body.get("kinds", list(frame_backup.KINDS))
+        if not isinstance(kinds, list) or not kinds or any(k not in frame_backup.KINDS for k in kinds):
+            raise Failure("Choose what to back up", 400)
+        name = agent_target()["name"]
+        work = lambda report: frame_backup.backup(report, kinds, headset=name)  # noqa: E731
+        label = "Back up the Frame"
+    elif action == "restore":
+        name, ids = body.get("name"), body.get("parts")
+        if not isinstance(ids, list) or not ids or not all(
+                isinstance(i, str) and frame_backup.PART.fullmatch(i) for i in ids):
+            raise Failure("Choose what to restore", 400)
+        work = lambda report: frame_backup.restore(name, ids, True, report)  # noqa: E731
+        label = "Restore from backup"
+    else:
+        raise Failure("Unknown backup action", 400)
+
+    def exclusive(report):
+        if not _backup_lock.acquire(blocking=False):
+            raise Failure("A backup or restore is already running", 409)
+        try:
+            return work(report)
+        finally:
+            _backup_lock.release()
+    ensure_master()
+    return start_job(label, exclusive, progress=True)
+
+
 # ---- Our Frame-side media player -----------------------------------------
 
 _MEDIA_LOCK = threading.Lock()
@@ -2841,7 +2909,7 @@ def source_manage(body):
 
 
 POST = {
-    "/api/android/backup": android_backup,
+    "/api/android/backup": android_backup, "/api/backup": backup_action,
     "/api/vr": vr,
     "/api/comfort": comfort, "/api/media": media, "/api/agent/call": agent_call,
     "/api/agent/approval": agent_approval, "/api/assistant/chat": assistant_chat,