Merge pull request #7: Release 0.9.3-beta.4

Release 0.9.3-beta.4

.github/workflows/ci.yml

@@ -0,0 +1,106 @@
+# SPDX-FileCopyrightText: 2026 Dillard Blom
+# SPDX-License-Identifier: AGPL-3.0-or-later
+name: CI
+
+on:
+  push:
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  unit:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        php: ['8.2', '8.3', '8.4']
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          extensions: sodium, zip
+          coverage: none
+      - run: composer install --no-interaction --no-progress
+      - run: vendor/bin/phpunit -c tests/phpunit.xml
+
+  psalm:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: '8.2'
+          extensions: sodium, zip
+          coverage: none
+      - run: composer install --no-interaction --no-progress
+      - run: composer psalm
+
+  integration:
+    # Full round trip (key, kit, location, backup, incremental, restore modes, database dump and
+    # restore, retention, trash) on a fresh Nextcloud per version and database.
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        nextcloud: ['32', '33', '34', '35']
+        database: ['sqlite', 'mariadb', 'pgsql']
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - name: Round trip on Nextcloud ${{ matrix.nextcloud }} / ${{ matrix.database }}
+        run: tests/integration/matrix.sh "${{ matrix.nextcloud }}" "${{ matrix.database }}"
+
+  integration-targets:
+    # Same round trip, but through the real S3 (s3mock) and SFTP backends instead of a local
+    # path, so files_external's AmazonS3/SFTP backend and auth classes are actually exercised.
+    # Backend correctness does not depend on the Nextcloud version or database, so this runs once.
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - name: Round trip against S3 and SFTP
+        run: tests/integration/targets-matrix.sh
+
+  integration-user:
+    # Per-user backup/restore via user_migration (occ backup:user:backup / backup:user:restore),
+    # an optional dependency installed from the app store. It calls user_migration's internal
+    # UserMigrationService, whose API can change between Nextcloud versions, so this runs on every
+    # supported version (not the database, which the main integration job already covers).
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        nextcloud: ['32', '33', '34', '35']
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - name: Set up a fresh Nextcloud instance
+        run: |
+          docker run -d --name ngbu -e SQLITE_DATABASE=nextcloud -e NEXTCLOUD_ADMIN_USER=admin \
+            -e NEXTCLOUD_ADMIN_PASSWORD=admin-user-roundtrip -e NEXTCLOUD_TRUSTED_DOMAINS=localhost \
+            -v "$PWD:/var/www/html/custom_apps/ng_backup:ro" nextcloud:${{ matrix.nextcloud }}-apache
+          for i in $(seq 1 90); do docker exec -u www-data ngbu php occ status 2>/dev/null | grep -q "installed: true" && break; sleep 4; done
+          docker exec ngbu chown www-data:www-data /var/www/html/custom_apps
+      - name: Per-user backup/restore round trip on Nextcloud ${{ matrix.nextcloud }}
+        run: tests/integration/user-roundtrip.sh "docker exec -u www-data ngbu" /var/www/html/data
+
+  integration-full-restore:
+    # Disaster recovery (occ backup:restore:full) on a SECOND, fresh Nextcloud instance that
+    # never saw the first one, sharing only the backup location. Does not depend on the database
+    # beyond what the main integration job already covers, so this runs once, on one NC version.
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - name: Full restore round trip
+        run: tests/integration/full-restore-roundtrip.sh 35-apache

.gitignore

@@ -1,7 +1,10 @@
 /build/
+cred-*
+*credentials*
 /css/
 /js/
 /node_modules/
 .phpunit.result.cache
+*.secret
 /spikes/out/
 /vendor/

CHANGELOG.md

@@ -0,0 +1,142 @@
+# Changelog
+
+All notable changes to NG Backup are documented here. The format follows
+[Keep a Changelog](https://keepachangelog.com/en/1.1.0/); versioning follows the stages in
+`PLAN.md` section 9. The `<version>` in `appinfo/info.xml` is plain SemVer-numeric on purpose:
+the app store accepts a `-beta` suffix, but Nextcloud servers then only offer the release on the
+beta/daily update channel, which would hide the app from most admins. The stability stage is
+instead carried by the app description, the git tag, the release, and this file.
+
+## [0.9.3-beta.4] - 2026-10-08
+
+Bugfix release.
+
+### Fixed
+- A backup failed with "cannot execute INSERT in a read-only transaction" on PostgreSQL as soon
+  as the database dump filled a whole pack (32 MiB): the pack's index cache row was written
+  inside the read-only dump transaction. On other databases that row was rolled back silently.
+- Backups to a remote location slowed down as the repository grew: every backup step listed the
+  repository's index with a round trip per file. Over SFTP to a Hetzner Storage Box a 60 GiB
+  repository already lost a large part of each step to it; backing up continuously
+  (`occ backup:run`) went from 45 KiB/s to 5.8 MB/s with the fix.
+
+## [0.9.2-beta.3] - 2026-10-08
+
+Bugfix release.
+
+### Added
+- README: notes on using a Hetzner Storage Box over WebDAV and SMB.
+
+### Fixed
+- Adding a backup location in the web interface failed with "Request failed with status code 403"
+  when the login was more than 30 minutes old: the form did not ask for password confirmation.
+- Settings page: the "Backup and restore" / "Settings" tabs line up with the sections below them.
+- Backups: the runs table scrolls horizontally on narrow screens instead of running off the page.
+- `occ backup:verify --deep`: a blob that could not be read (network or storage error) was reported
+  as "corrupted or tampered". Reads are now retried, and a read that keeps failing is reported
+  separately as unreadable, with the error (run the check again; if the same blobs stay unreadable,
+  their pack may be damaged or truncated). Only a blob that was read but fails decryption or its
+  hash check counts as corrupted. Found on a Hetzner Storage Box over WebDAV, where the blob
+  turned out to be intact.
+
+## [0.9.1-beta.2] - 2026-10-07
+
+Second beta, the first release in the Nextcloud app store (signed).
+
+### Added
+- App store listing: screenshots, website, repository and documentation link in `appinfo/info.xml`.
+
+### Fixed
+- Restore: the "new folder" option showed `"Restored "` without the date pattern.
+- Restore: the restore-point dropdown cut off the time.
+- Settings: the passphrase actions are on one line instead of stacked.
+- `docs/HOWTO.md`: the SFTP example used a non-existent auth mechanism (`sftp::password`
+  instead of `password::password`).
+
+## [0.9.0-beta.1] - 2026-10-07
+
+First beta. Tested thoroughly and usable **alongside** your current backup, but **not yet a
+drop-in replacement** for it. We test what we can ourselves (Nextcloud 32–35, SQLite, MariaDB and
+PostgreSQL, S3, SFTP, FTP, SMB and NFS), but we need field experience from other setups: please
+report what works and what doesn't, especially on large instances and on storage providers not
+listed in the README.
+
+### Added
+- Disaster recovery: `occ backup:key:import` and `occ backup:restore:full` restore the database,
+  data directory and config onto a fresh installation of the same major version.
+- Per-user backup and restore via user_migration: `occ backup:user:backup` and
+  `occ backup:user:restore` (replace the account after a safety export, or restore as
+  `<uid>-bak`), also onto a server where the user does not exist yet. The commands ask before
+  installing user_migration (or take `--install-user-migration`).
+- Checksum audit: `occ backup:verify`, shallow or `--deep`, for snapshots and per-user exports.
+- Retention for per-user exports: `occ backup:retention --user-last=N`.
+- FTP and SMB covered by the integration tests; NFS through the `local` backend on a mounted share.
+- `docs/HOWTO.md`: step by step from setup to a tested restore.
+- Warnings when a backup finishes with unreadable files or folders, or with files that kept
+  changing while being read (log, `occ`, notification, snapshot).
+
+### Changed
+- `backup:restore:full` refuses on an installation with more than one user and asks first;
+  `backup:user:restore --mode=replace` asks before deleting an existing account (`--force` for
+  scripts in both cases).
+- A failed scheduled backup is retried at most three times a day, an hour apart.
+- The recovery kit carries the deletion delay; the kit file is created owner-only.
+- Adding a location through the web API needs password confirmation.
+
+### Fixed
+- Exports of users whose id contains `.part-` could be deleted by cleanup on remote locations.
+- Cleanup no longer frees the data of a per-user export whose manifest is missing.
+- Crash safety of moving snapshots to and from the trash, of catalog writes by concurrent
+  backups and per-user exports, and of short uploads.
+- A file that keeps changing no longer makes a backup restart forever.
+- Long restores and exports keep their lock on the location alive.
+- Floating-point database columns are dumped exactly.
+
+### Known limitations
+See "Known limitations" in the README: memory use on very large instances, never two servers
+writing to one location, removing a passphrase slot does not revoke access, no rollback detection
+before a disaster recovery, and a few smaller points. None of them block the road to 1.0.0; they
+are on the backlog in `PLAN.md`.
+
+## [0.1.0-alpha.1] - 2026-10-05
+
+First public alpha. Feature-complete for phase 1: scheduled, encrypted, incremental backups, and
+restore of files and folders. **Not for production use** — test on a copy of production (dev,
+test, staging). Full disaster recovery (`backup:restore:full` on a fresh installation) is phase 2
+and not implemented yet.
+
+### Added
+- Encrypted (XChaCha20-Poly1305), content-addressed, deduplicated, incremental backups, streamed
+  from source to destination without a local copy of the data.
+- Backup locations via files_external's own backend/auth classes, without ever mounting the
+  location: S3 (and compatible services), SFTP, WebDAV, FTP, Swift, or a local path.
+- A recovery kit with up to three passphrase slots, mandatory download-and-confirm before the
+  first backup runs, and an optional encrypted copy by email.
+- Resumable, time-boxed background jobs (database dump, file walk, upload), so a run survives
+  short PHP time limits and a crash is resumed, never restarted, without leaving the instance in
+  maintenance mode.
+- Database dump and restore without external tools, via Nextcloud's own `IDBConnection`/DBAL,
+  streamed through the same pipeline as file data.
+- Restore of files and folders via the web interface and `occ`, into a new folder, merged, or
+  replacing the original (with the previous content going to the trash).
+- Retention policy (last/daily/weekly/monthly), prune with pack repacking, and a snapshot trash
+  with a configurable deletion delay.
+- Append-only locations and documented recommendations against ransomware and a compromised
+  server (object lock, delete-less credentials, off-site copies).
+- Admin settings page (locations, schedule, retention, key management) and a JSON API.
+- Notifications and an admin setup check for a failed or overdue backup.
+- CI: unit tests on PHP 8.2–8.4, and an end-to-end backup→restore round trip on Nextcloud 32–35 ×
+  SQLite/MariaDB/PostgreSQL, and against real S3 and SFTP backends (not just a local path).
+
+### Known limitations
+- No full/disaster-recovery restore yet (phase 2).
+- No per-user backup/restore via user_migration yet (phase 2).
+- No FTP/SMB coverage in CI yet, and no verification/checksum-audit command yet (phase 2).
+- See the "Storage backend experiences" section of the README for provider-specific quirks found
+  so far (e.g. Hetzner Storage Box sub-accounts).
+
+[0.9.3-beta.4]: https://github.com/dillardblom/ng_backup/releases/tag/v0.9.3-beta.4
+[0.9.2-beta.3]: https://github.com/dillardblom/ng_backup/releases/tag/v0.9.2-beta.3
+[0.9.1-beta.2]: https://github.com/dillardblom/ng_backup/releases/tag/v0.9.1-beta.2
+[0.9.0-beta.1]: https://github.com/dillardblom/ng_backup/releases/tag/v0.9.0-beta.1
+[0.1.0-alpha.1]: https://github.com/dillardblom/ng_backup/releases/tag/v0.1.0-alpha.1

PLAN.md

@@ -214,8 +214,8 @@ Daarom:
 ### 3.8 Backup en restore per gebruiker: via user_migration
 
 In plaats van zelf te bepalen welke gegevens van een gebruiker meegaan, hergebruiken we
-**user_migration** (officiële Nextcloud-app, actief onderhouden, NC29–36; staat ook op nc01).
-Die app werkt met *migrators* die andere apps zelf aanleveren. Op nc01 hebben die er al:
+**user_migration** (officiële Nextcloud-app, actief onderhouden, NC29–36; draait ook op onze eigen productie-instantie).
+Die app werkt met *migrators* die andere apps zelf aanleveren. Op onze productie-instantie zijn dat er al:
 calendar, dav (agenda's en contactpersonen), deck, files_trashbin, mail, settings (profiel,
 account, app-instellingen) en de bestanden zelf. Elke app die later een migrator toevoegt, gaat
 automatisch mee.
@@ -276,7 +276,7 @@ onderdelen wel en niet terugkomen, op basis van de geregistreerde migrators.
 | `backup:list [--target=]` | herstelpunten |
 | `backup:verify <snapshot> [--deep]` | checksums controleren, optioneel alles ontsleutelen |
 | `backup:restore:file <snapshot> <user> <pad> [--to=]` | bestand/map terugzetten |
-| `backup:restore:user <snapshot> <user> [--to-user=]` | gebruiker terugzetten via user_migration (fase 2) |
+| `backup:user:restore <snapshot> <user> [--to-user=]` | gebruiker terugzetten via user_migration (fase 2) |
 | `backup:restore:full <snapshot>` | volledige restore (fase 2, verse installatie) |
 | `backup:target:add/list/remove/test` | opslagdoelen beheren en testen |
 | `backup:key:export / import` | herstelkit |
@@ -308,14 +308,14 @@ niet met de hunne, maar bij installatie waarschuwen als `backup` ook actief is.
 | 2 | Backup/restore per gebruiker via user_migration, volledige restore op verse installatie, FTP/SMB, verificatie | 3–4 weken |
 | 3 | In-place volledige restore (restore-modus), zelfbediening voor gebruikers, extra doelen | open |
 
-Release in de app store pas na fase 1 en een periode van eigen gebruik op nc01 (net als occweb):
+Release in de app store pas na fase 1 en een periode van eigen gebruik op onze productie-instantie (net als occweb):
 een backup-app die niet betrouwbaar is, is erger dan geen backup-app.
 
 ## 8. Besluiten (2026-10-01)
 
 1. **Doelgroep:** alle varianten: AIO, losse installaties én gehoste Nextcloud zonder SSH.
 2. **Licentie:** AGPL-3.0-or-later.
-3. **Repository:** Ensembia op Gitea + GitHub (dillardblom), zoals occweb.
+3. **Repository:** eigen Gitea + GitHub (dillardblom), zoals occweb.
 4. **Naam:** "NG Backup", app-id `ng_backup`, occ-voorvoegsel `backup:`.
 5. **Herstelkit:** verplicht downloaden + expliciete bevestiging door de beheerder (vinkje +
    "Yes, I confirm"), zie 3.2; versleuteld per e-mail als optionele extra kopie.
@@ -325,6 +325,67 @@ een backup-app die niet betrouwbaar is, is erger dan geen backup-app.
    export, verwijderen, opnieuw aanmaken), óf terugzetten als `<gebruiker>-bak`, zie 3.8.
 8. **Fase 0 afgerond (2026-10-01),** resultaten in `spikes/RESULTS.md`.
 
+## 9. Releases en versies (besluit 2026-10-02)
+
+| Versie | Betekenis |
+|---|---|
+| 0.1.0-alpha.N | publiek; meetesten gewaardeerd op een kopie van productie (dev, test, staging) |
+| 0.9.0-beta.N | mag meedraaien op productie, naast de reguliere backup; volledige restore aanwezig en getest |
+| 1.0.0-rc.N | releasekandidaten, alleen bugfixes |
+| 1.0.0 | stabiel: vervanging van de reguliere backup, noodherstel bewezen |
+| 1.2.0 e.v. | functies van fase 2 (restore per gebruiker, FTP/SMB, verificatie, ...) |
+
+Volgorde: fase 1 grondig testen, reviewen en debuggen; dan nadenken over 0.1.0-alpha.1. Een
+minimale volledige restore (`occ backup:restore:full` op een verse installatie) komt vóór de beta.
+
+**Roadmap-indeling fase 2 (besluit 2026-10-05):** naar v1.2.0 toewerken met in fase 2:
+1. `backup:restore:full` (disaster recovery, verse installatie) — **klaar** (2026-10-05)
+2. FTP/SMB-ondersteuning — **klaar** (2026-10-06): beide liepen al via files_external's generieke
+   adapter zonder enige ng_backup-code; alleen testdekking toegevoegd
+   (`tests/integration/targets-matrix.sh`) + bevindingen in README ("Storage backend experiences").
+   SMB vereist de `smbclient` PECL-extensie (niet standaard in de Nextcloud-image, in CI nu
+   on-the-fly gebouwd). NFS is geen eigen backend: lokaal mounten + `local`-backend erop richten.
+3. Verificatie/checksum-audit-commando — **klaar** (2026-10-05)
+4. Retentie/prune voor user-exports — **klaar** (2026-10-06): `occ backup:retention --user-last=N`
+   (standaard 3, per installatie, net als de bestaande snapshot-policy), toegepast door
+   `occ backup:prune` (geen prullenbak voor user-exports, in tegenstelling tot snapshots — on-demand,
+   niet het primaire vangnet).
+5. Automatische user-export in het reguliere schema — **naar backlog** (niet voor deze release; on-demand blijft)
+9. SMB-roundtrip (protocol, niet een specifieke server) — **klaar** (2026-10-06): CI-matrix, 2 GB-roundtrip en
+   user-export via SMB; NFS via de OMV-share getest (`local`-backend op een gemounte share, 2026-10-06)
+10. `backup:user:restore` zonder user_migration: vraagt om toestemming om de app te installeren en te activeren (of
+   `--install-user-migration`) — **klaar** (2026-10-06); waarschuwing over de settings-allowlist — **klaar**;
+   agenda/contacten bij migratie naar een server zonder die gebruiker — **getest** (2026-10-06, naar `migrated-personal`/`migrated-contacts`)
+    Backlog: (a) de originele weergavenaam herstellen (het label uit de export is niet getest als
+    weergavenaam); (b) de interne `migrated-`-naam hernoemen (vereist directe databasewijziging, niet voor de beta).
+
+**Backlog uit de pre-beta review (2026-10-07)** — geen belemmering voor 0.9.0-beta of 1.0.0, staat
+in README "Known limitations":
+1. Geheugen bij grote instanties (>1 TB, miljoenen bestanden): blob-index, prune-set, browse van een
+   snapshot in de web-UI, `trashExtras` bij restore en het manifest van een user-export staan volledig
+   in het geheugen; streaming/paginering nodig.
+2. Twee servers op één locatie: catalogus kan breken (generatie overschreven, of anchor >200 generaties
+   achter). Docs-waarschuwing staat er; mogelijk later een echte put-if-absent per backend.
+3. Sleutelrotatie: een slot verwijderen trekt geen toegang in (master-key blijft gelijk).
+4. Rollback vóór DR niet detecteerbaar: referentie-generatie en -hash in de kit opnemen of tonen.
+5. Kit-velden buiten `wrapped_key` (o.a. `delete_delay_days`) zijn niet geauthenticeerd; nu alleen getoond.
+6. Repository-id in de AD van objecten (formaatwijziging).
+7. Wachtwoorden van locaties via `--option-file` of omgevingsvariabele i.p.v. de commandoregel.
+8. Tijdelijke restore-bestanden niet via de Files-API verwijderen (komen nu in de prullenbak).
+9. DB-restore in foreign-key-volgorde (cascades).
+10. Packs zonder index (index-upload mislukt) opruimen.
+11. `backup:restore:full` in onderhoudsmodus en hervatbaar maken; nu: opnieuw draaien met `--force`.
+12. Config/rename op FTP/SMB-servers die geen rename over een bestaand bestand toestaan.
+
+Doorgeschoven naar **v1.3.0** (fase 3, niet meer fase 2): in-place volledige restore
+(eigen restore-modus i.p.v. onderhoudsmodus) en zelfbediening voor gebruikers (eigen bestanden
+terugzetten vanuit de Files-app).
+
+**Let op (ontdekt 2026-10-05):** Nextcloud's eigen `info.xsd` staat voor `<version>` alleen
+`[0-9]+(\.[0-9]+){0,2}` toe — geen `-alpha`/`-beta`/`-rc`-achtervoegsel. De stabiliteitsaanduiding
+uit deze tabel gaat dus niet in `info.xml` (dat blijft gewoon oplopend, bijv. `0.1.0`), maar in de
+git-tag (`v0.1.0-alpha.1`), de GitHub/Gitea release (gemarkeerd als pre-release) en de CHANGELOG.
+
 ## Bijlage: lessen uit nextcloud/backup (test NC34, 2026-10-01)
 
 - Externe programma's (`pg_dump`) en extensies (`pgsql`, `mysqli`) → onbruikbaar op standaard/hosted.

README.md

@@ -1,8 +1,202 @@
 # NG Backup
 
-Encrypted, incremental backups of Nextcloud with restore from the web interface.
-Works without shell access: no external programs, no extra PHP extensions beyond sodium.
+Encrypted, incremental backups of Nextcloud (database, configuration and data) with restore
+from the web interface. Works without shell access: no external programs, no extra PHP
+extensions beyond sodium for ng_backup itself. Runs on Nextcloud All-in-One, regular
+installations and hosted Nextcloud. (Choosing SMB as a storage backend is the one exception:
+see "Storage backend experiences" below — that requirement comes from files_external, not from
+ng_backup, and applies to any Nextcloud app that writes to an SMB share.)
 
-**Status: phase 0 (prototype). Not usable yet.** See `PLAN.md` for the design.
+**Status: beta (0.9.3).** Tested thoroughly, usable alongside your current backup, but not yet a
+drop-in replacement for it. See "Known limitations" below, `PLAN.md` for the design and
+`docs/HOWTO.md` for a step-by-step guide from setup to a tested restore.
 
 License: AGPL-3.0-or-later.
+
+## How it works
+
+- Backups go to a **location**: S3 (and S3-compatible storage), SFTP, WebDAV, FTP, Swift or a
+  local path. NG Backup uses the connection code of Nextcloud's External storage app, but never
+  mounts the location: it is only connected while a backup or restore runs, and it never
+  appears in Files, for anyone.
+- Data is cut into blocks, deduplicated, compressed and encrypted (XChaCha20-Poly1305) before it
+  leaves the server, and streamed straight to the location: no local copy, no double disk space.
+  Unchanged files are not read again; only new data is uploaded.
+- The database is dumped through Nextcloud's own connection, inside one consistent transaction.
+- Restores go through Nextcloud, so overwritten files keep their old content as a version and
+  removed files go to the trash.
+
+## Quick start
+
+```
+occ backup:key:init --label="Safe"                 # first passphrase, deletion delay (default 7 days)
+occ backup:key:slot:add --label="CTO"              # optional second and third passphrase
+occ backup:key:slot:add --label="Head of IT"
+occ backup:key:kit --output=/var/tmp/ng_backup-kit.json
+occ backup:key:confirm
+occ backup:target:add offsite amazons3 -a amazons3::accesskey -o bucket=... -o key=... -o secret=...
+occ backup:run
+```
+
+Or use **Administration settings → NG Backup**.
+
+## The backup key, passphrases and the recovery kit
+
+All backups of an installation are encrypted with one master key.
+
+- The **server** keeps the master key, encrypted with the instance secret, so scheduled backups
+  and restores work without anyone typing a passphrase. Any administrator can restore from the
+  web interface. Consequence: whoever fully controls the server can read the backups; whoever
+  only gets hold of the backup location cannot.
+- For a **restore on a new server** (disaster recovery) you need the **recovery kit** and **one
+  passphrase**. The kit contains the master key, encrypted separately with each passphrase.
+- Up to **three passphrases** ("slots") can open the key, so one person leaving or dying does not
+  lock the company out. A suggested setup:
+
+  | Slot | Kept by |
+  |---|---|
+  | 1 | in the safe (sealed envelope) |
+  | 2 | the CTO |
+  | 3 | the head of IT |
+
+  Every holder keeps a copy of the same recovery kit and only knows their own passphrase. Using
+  a single slot is possible, but then that one passphrase is a single point of failure.
+- When a holder leaves, give their slot a new passphrase (`occ backup:key:slot:replace`), download
+  the new kit and confirm it. Note: an old kit together with the old passphrase still opens the
+  same master key; to revoke it completely, start new locations with a new key. This is noted on
+  the backlog and will be addressed in a future version (key rotation).
+- Downloading the kit, and every change to the slots, requires the administrator's password, is
+  written to the audit log and is announced to all administrators.
+
+## Protection against ransomware and a compromised server
+
+A backup is only useful if an attacker cannot destroy it. An attacker with administrator access
+to Nextcloud could try to remove old restore points so that only infected data remains.
+NG Backup makes this hard and visible, but **software alone can never guarantee it**: the
+location must refuse deletions itself.
+
+What NG Backup does:
+
+- **Deletion delay.** Removed restore points first go to a trash on the location and are only
+  deleted after the delay chosen at installation (default 7 days, cannot be changed afterwards).
+  Within that time any administrator can bring them back (`occ backup:trash:restore`, or in the
+  web interface).
+- **Notifications to all administrators** when restore points are removed, the retention is
+  changed, append-only is turned off, a location is removed or the recovery kit is downloaded,
+  and an entry in the audit log (admin_audit).
+- **Append-only locations** (`occ backup:target:append-only NAME on`): NG Backup never deletes
+  anything there; old data is cleaned up by the location's own lifecycle rules.
+- Removing a location in NG Backup only removes the connection. The backups on the location are
+  not touched and nothing keeps cleaning up in the background.
+
+What you should do on the location (strongly recommended):
+
+- **S3: enable Object Lock** on the bucket, in **compliance mode**, with a default retention of
+  for example **90 days**, plus versioning. Then nobody, not even with the server's credentials,
+  can delete or overwrite backups younger than 90 days. Combine with an append-only location in
+  NG Backup and a lifecycle rule that removes old versions after the lock expires.
+  With Object Lock, a deletion by NG Backup (or by an attacker through it) only adds a *delete
+  marker*: the locked data stays and can be brought back from the bucket's object versions until
+  the lock expires. Tested with an S3-compatible server; still to be verified on AWS itself, which
+  requires a checksum on uploads to locked buckets.
+- Use **credentials without delete rights** for the backup location where the storage supports it.
+- **SFTP / storage boxes:** enable the provider's own snapshots (e.g. daily, kept 30-90 days) and
+  give the backup user access to its own folder only, without a shell.
+- Keep at least one location **off-site**, on a different network than the Nextcloud server.
+
+## Restore
+
+- **Files and folders** of a user: in the web interface or `occ backup:restore`, into a new folder
+  ("Restored <date>"), merged into the original place, or replacing it.
+- **Raw restore** of any path (for example `config/`) to a local directory: `occ backup:restore ... --to-directory=DIR`.
+- **Whole server** (disaster recovery onto a fresh installation): `occ backup:restore:full`, see the how-to.
+- **One user** (account, settings, files, calendars, contacts via user_migration): `occ backup:user:backup` and
+  `occ backup:user:restore`, replacing the account or restoring it as `<uid>-bak`. See the how-to.
+
+## Storage backend experiences
+
+Notes from actually running a backend, beyond what's in files_external's own documentation.
+Contributions welcome via PR — add what you ran into with your own provider.
+
+- **Hetzner Storage Box, sub-account:** the SFTP backend's `root` option must be `home`, not `/`.
+  A sub-account's SFTP login lands in `/home` (confirmed via `pwd()` after login); writing to the
+  literal chroot root (`/`) fails with a generic `NET_SFTP_STATUS_FAILURE` from the SFTP server,
+  while the same write under `home` (or a path below it) succeeds. This affects any backend option
+  form that lets you set a path relative to the account's root, not just ng_backup. Not yet
+  verified whether this also applies to a Hetzner Storage Box **main** account (only tested with a
+  sub-account so far) — if you've tried a main account, please say so in a PR.
+
+- **Hetzner Storage Box over WebDAV and SMB (sub-accounts, 2026-10-07):** both work end to end
+  (backup, incremental run, restore of a folder, verify), tested from outside the Hetzner network
+  with about 66 MiB of data. In the Hetzner Console, enable WebDAV or SMB support for the
+  sub-account, and "External reachability" when your server is not in the Hetzner network.
+  WebDAV: host `https://uXXXXX-subN.your-storagebox.de`, and the `root`
+  must be a folder that already exists (or empty): WebDAV does not create missing parent folders,
+  so a root that doesn't exist yet fails `backup:target:add` with `Sabre\HTTP\ClientHttpException:
+  Conflict`. SMB: share = the sub-account name, port 445 must be reachable from your server (it was
+  from a home connection here, but some providers block it), and the `smbclient` PECL extension is
+  required (see the SMB entry below). Both have a noticeable fixed cost per run: an incremental run
+  that uploads nothing took about 20 s over WebDAV and 50 s over SMB. A deep verify is slow over
+  remote storage, since each blob is fetched with its own request (19 minutes for 66 MiB over
+  WebDAV); run it occasionally, not after every backup.
+
+- **FTP, server-dependent absolute-path handling:** files_external's FTP backend always builds
+  absolute paths (e.g. `MKD /repo`) for the configured root, never relative ones. `atmoz/sftp`-style
+  `vsftpd` test servers (chrooted) can reject that with a generic "create directory operation
+  failed", even though a plain `ftp_mkdir()` with a *relative* path on the same server succeeds;
+  `pure-ftpd` accepts the absolute form fine. If a working FTP server rejects ng_backup's writes,
+  try a different FTP server implementation before assuming the backend itself is broken.
+
+- **SMB/CIFS *lists* as available with just the `smbclient` CLI binary, but does not actually
+  work for ng_backup without the `smbclient` PECL extension too.** files_external falls back to a
+  shell-wrapped `smbclient` process when the native extension is missing, which registers the
+  backend in `occ backup:target:backends` fine, but that fallback's stream cannot seek. ng_backup
+  reads blobs back by byte range while backing up, so even the very first (small) backup fails
+  with `Seek failed in packs/...`. Install the extension (`libsmbclient-dev` + `pecl install
+  smbclient` + `docker-php-ext-enable smbclient` on Debian-based images), not just the CLI tool —
+  the backend being listed is not proof it will work here. Once the extension is present it works
+  the same as any other backend; no ng_backup-specific config beyond host/share/user/password.
+
+- **NFS is not a files_external backend at all.** Mount the NFS export on the server yourself
+  (e.g. via `/etc/fstab` or a systemd `.mount` unit) and point ng_backup's `local` backend at the
+  mount point; ng_backup never mounts or unmounts anything on its own, so an NFS mount dropping
+  mid-run behaves like any other local-path failure (the run resumes). See PLAN.md 3.5 for why NFS
+  can't be driven from PHP directly.
+
+## Known limitations
+
+On the backlog; none of these block the beta or 1.0.0, but know them before you rely on it:
+
+- **Very large instances** (well over 1 TB, millions of files): the blob index, cleanup, browsing a
+  snapshot in the web interface and per-user export manifests are held in memory. Expect high
+  memory use there; reports from such instances are very welcome.
+- **One location, one server.** Never let two Nextcloud servers write to the same location (for
+  example a disaster recovery test server pointed at the production location): they can break each
+  other's catalog, and the location is then refused as possibly tampered with. Test a disaster
+  recovery against a copy of the location, or only read from it.
+- **Removing a passphrase slot does not revoke access.** The master key stays the same, so someone
+  with an old recovery kit and that slot's passphrase can still decrypt the location if they can
+  read it. Key rotation is not available yet.
+- **Rollback before a disaster recovery is not detected.** A fresh server has no record of the
+  newest catalog generation, so a location rolled back to an older state looks valid there.
+- Location passwords passed with `-o password=...` are visible in the process list and shell
+  history while the command runs.
+- Temporary files of a restore into a user's files end up in that user's trash.
+- Restoring the database does not order tables by foreign keys; apps with cascading foreign keys
+  could lose rows (Nextcloud core does not use them).
+- A pack whose index upload failed stays on the location until removed by hand.
+
+## Commands
+
+| Command | Purpose |
+|---|---|
+| `backup:key:init`, `backup:key:kit`, `backup:key:confirm` | create the key, recovery kit, confirmation |
+| `backup:key:slots`, `backup:key:slot:add/replace/remove` | passphrase slots |
+| `backup:target:backends/add/list/remove/append-only` | backup locations |
+| `backup:run`, `backup:status`, `backup:list` | back up, status, restore points |
+| `backup:browse`, `backup:restore` | browse and restore |
+| `backup:retention`, `backup:prune`, `backup:trash`, `backup:trash:restore` | retention, cleanup, trash |
+| `backup:verify` | checksum audit of a restore point (`--deep` downloads and decrypts everything) |
+| `backup:restore:full` | whole-server restore onto a fresh installation (after `backup:key:import`) |
+| `backup:key:import` | import a recovery kit on a fresh installation |
+| `backup:user:backup`, `backup:user:restore` | one user via user_migration (asks before installing it) |

appinfo/info.xml

@@ -4,13 +4,25 @@
     <id>ng_backup</id>
     <name>NG Backup</name>
     <summary>Encrypted, incremental backups of your Nextcloud with restore from the web interface</summary>
-    <description><![CDATA[Work in progress, not ready for use.]]></description>
-    <version>0.0.5</version>
+    <description><![CDATA[Beta: scheduled, encrypted, incremental backups of the database, config and data
+directory to S3, SFTP, WebDAV, FTP, SMB or a local path, with restore of files and folders, of
+single users (via user_migration) and of the whole server onto a fresh installation. Tested
+thoroughly and usable alongside your current backup, but not yet a drop-in replacement for it.
+See the README for known limitations and the recovery kit before relying on it.]]></description>
+    <version>0.9.3</version>
     <licence>agpl</licence>
     <author>Dillard Blom</author>
     <namespace>NgBackup</namespace>
+    <documentation>
+        <admin>https://github.com/dillardblom/ng_backup/blob/main/docs/HOWTO.md</admin>
+    </documentation>
     <category>tools</category>
+    <website>https://apps.nextcloud.com/apps/ng_backup</website>
     <bugs>https://github.com/dillardblom/ng_backup/issues</bugs>
+    <repository type="git">https://github.com/dillardblom/ng_backup</repository>
+    <screenshot>https://raw.githubusercontent.com/dillardblom/ng_backup/main/screenshots/1-backups.png</screenshot>
+    <screenshot>https://raw.githubusercontent.com/dillardblom/ng_backup/main/screenshots/2-restore.png</screenshot>
+    <screenshot>https://raw.githubusercontent.com/dillardblom/ng_backup/main/screenshots/3-settings.png</screenshot>
     <dependencies>
         <php min-version="8.1"/>
         <lib>sodium</lib>
@@ -32,6 +44,22 @@
         <command>OCA\NgBackup\Command\ListSnapshots</command>
         <command>OCA\NgBackup\Command\Browse</command>
         <command>OCA\NgBackup\Command\Restore</command>
+        <command>OCA\NgBackup\Command\Prune</command>
+        <command>OCA\NgBackup\Command\Retention</command>
+        <command>OCA\NgBackup\Command\TargetAppendOnly</command>
+        <command>OCA\NgBackup\Command\TargetTrustCurrent</command>
+        <command>OCA\NgBackup\Command\TargetLimit</command>
+        <command>OCA\NgBackup\Command\Trash</command>
+        <command>OCA\NgBackup\Command\TrashRestore</command>
+        <command>OCA\NgBackup\Command\KeySlots</command>
+        <command>OCA\NgBackup\Command\KeySlotAdd</command>
+        <command>OCA\NgBackup\Command\KeySlotReplace</command>
+        <command>OCA\NgBackup\Command\KeySlotRemove</command>
+        <command>OCA\NgBackup\Command\BackupUser</command>
+        <command>OCA\NgBackup\Command\RestoreUser</command>
+        <command>OCA\NgBackup\Command\KeyImport</command>
+        <command>OCA\NgBackup\Command\RestoreFull</command>
+        <command>OCA\NgBackup\Command\Verify</command>
     </commands>
     <settings>
         <admin>OCA\NgBackup\Settings\Admin</admin>

appinfo/routes.php

@@ -11,10 +11,16 @@ return [
 		['name' => 'AdminApi#initKey', 'url' => '/api/key', 'verb' => 'POST'],
 		['name' => 'AdminApi#downloadKit', 'url' => '/api/key/kit', 'verb' => 'GET'],
 		['name' => 'AdminApi#confirmKit', 'url' => '/api/key/confirm', 'verb' => 'POST'],
+		['name' => 'AdminApi#addSlot', 'url' => '/api/key/slots', 'verb' => 'POST'],
+		['name' => 'AdminApi#replaceSlot', 'url' => '/api/key/slots/{slot}', 'verb' => 'PUT'],
+		['name' => 'AdminApi#removeSlot', 'url' => '/api/key/slots/{slot}', 'verb' => 'DELETE'],
+		['name' => 'AdminApi#trash', 'url' => '/api/targets/{targetId}/trash', 'verb' => 'GET'],
+		['name' => 'AdminApi#untrash', 'url' => '/api/targets/{targetId}/trash/{snapshotId}', 'verb' => 'POST'],
 		['name' => 'AdminApi#backends', 'url' => '/api/backends', 'verb' => 'GET'],
 		['name' => 'AdminApi#addTarget', 'url' => '/api/targets', 'verb' => 'POST'],
 		['name' => 'AdminApi#removeTarget', 'url' => '/api/targets/{id}', 'verb' => 'DELETE'],
 		['name' => 'AdminApi#testTarget', 'url' => '/api/targets/{id}/test', 'verb' => 'POST'],
+		['name' => 'AdminApi#setTargetLimit', 'url' => '/api/targets/{id}/limit', 'verb' => 'PUT'],
 		['name' => 'AdminApi#startBackup', 'url' => '/api/backups', 'verb' => 'POST'],
 		['name' => 'AdminApi#setSchedule', 'url' => '/api/schedule', 'verb' => 'PUT'],
 		['name' => 'AdminApi#snapshots', 'url' => '/api/targets/{targetId}/snapshots', 'verb' => 'GET'],

docs/HOWTO.md

@@ -0,0 +1,158 @@
+# NG Backup how-to
+
+Step by step: from first install to a tested restore. All commands run as the web user
+(`sudo -u www-data php occ ...`, or `docker exec -u www-data <container> php occ ...` in
+All-in-One and Docker setups). Replace names in `<angle brackets>` with your own.
+
+## 1. Create the key and the recovery kit
+
+```
+occ backup:key:init --label="Main" --delete-delay-days=7
+occ backup:key:kit --output=/var/tmp/ng_backup-kit.json
+occ backup:key:confirm -u <your-admin-uid> --code=<code shown> --confirm="Yes, I confirm"
+```
+
+- The passphrase protects the backup. Keep it somewhere other than this server.
+- Optional: extra passphrases for other people with `occ backup:key:slot:add --label="..."`.
+  Any one passphrase is enough to restore. Removing a slot later does not revoke access for someone
+  who kept an old kit and that passphrase (see "Known limitations" in the README).
+- The recovery kit (`/var/tmp/ng_backup-kit.json` above) is also required for disaster recovery. The web
+  user writes it there; then move it off the server as root, next to the passphrase, and delete the
+  copy in `/var/tmp`. Without the kit and a passphrase, the backup cannot be read.
+
+## 2. Add a backup location
+
+NG Backup uses Nextcloud's External storage backends. Check what your server supports first:
+
+```
+occ backup:target:backends
+```
+
+Examples:
+
+```
+occ backup:target:add offsite amazons3 -a amazons3::accesskey -o bucket=<bucket> -o key=<key> -o secret=<secret>
+occ backup:target:add nas sftp -a password::password -o host=<host> -o user=<user> -o password=<pw> -o root=home
+occ backup:target:add local local -a null::null -o datadir=/mnt/backup
+```
+
+- **SFTP on a Hetzner Storage Box sub-account:** use `-o root=home`, not `/` (see README).
+- **FTP:** use a server that accepts absolute paths (for example `pure-ftpd`).
+- **SMB:** requires the native `smbclient` PHP extension. The CLI binary alone is not enough (see README).
+  `backup:target:add` refuses SMB when the extension is missing.
+- **NFS:** not a backend of its own. Mount the export on the server and use the `local` backend
+  with the mount point as `datadir`.
+
+Verify the location before relying on it:
+
+```
+occ backup:target:list
+occ backup:status
+```
+
+## 3. Run the first backup
+
+```
+occ backup:run offsite -l first
+occ backup:list
+```
+
+Later runs upload only changed data. An unchanged run uploads (almost) nothing; the output shows
+the number of uploaded bytes, so check that value when you test incremental behaviour.
+
+Schedule `occ backup:run` from system cron (or use the Administration settings, if you prefer).
+
+## 4. Check the backup regularly
+
+```
+occ backup:verify offsite <snapshot>          # shallow: all blocks are present
+occ backup:verify offsite <snapshot> --deep   # also downloads and decrypts every block
+```
+
+Run the deep check at least once after setting up a location, and after changing it.
+
+## 5. Restore files and folders
+
+In the web interface, or with occ:
+
+```
+occ backup:browse offsite <snapshot>
+occ backup:restore offsite <snapshot> data/<uid>/files/Docs --mode=new-folder
+occ backup:restore offsite <snapshot> data/<uid>/files/Docs --mode=merge
+occ backup:restore offsite <snapshot> data/<uid>/files/Docs --mode=replace
+occ backup:restore offsite <snapshot> config --to-directory=/var/tmp/restore-config
+```
+
+- `new-folder` (default): puts the files in "Restored <date>" next to the original. Safest choice.
+- `merge`: adds missing files, keeps current ones.
+- `replace`: overwrites the folder. Replaced files keep their old content as a version, and removed
+  files go to the trash.
+- `--to-directory`: writes raw files to a local directory (for example `config/`).
+
+## 6. Back up and restore one user
+
+Needs the `user_migration` app. NG Backup asks before installing it:
+
+```
+occ backup:user:backup offsite <uid>
+occ backup:user:restore offsite users/<uid>/<exportId>               # replace (default)
+occ backup:user:restore offsite users/<uid>/<exportId> --mode=as-backup
+```
+
+- If `user_migration` is missing, the command asks to install and enable it. For non-interactive
+  use, add `--install-user-migration` to approve that explicitly. The command stops after the
+  installation; run it once more.
+- `replace` first makes a safety export of the current account, then recreates the user under the
+  same id. When the account exists, the command asks first; in scripts, add `--force`. Shares to
+  others and data of apps without a user_migration migrator are not restored, so prefer
+  `as-backup` when in doubt: it restores into `<uid>-bak` and leaves the original untouched.
+- A restore onto a server where the user does not exist works. Calendars and address books get an
+  internal name with the prefix `migrated-` (for example `migrated-personal`). That prefix comes from
+  user_migration and cannot be turned off. The user can change the display name of these calendars and
+  address books in the app as usual; the internal name stays as it is.
+- **Settings:** on restore, `user_migration` imports only the app settings on its own allowlist
+  (for example calendar view and reminder settings). Other app settings of the user are skipped.
+  NG Backup reuses `user_migration`'s importer, so this list is not extended.
+- Keep the last few exports per user: `occ backup:retention --user-last=3`.
+
+## 7. Disaster recovery: restore the whole server
+
+Use a fresh Nextcloud installation of the same major version, with NG Backup installed and
+the same location available. For a test, use a **copy** of the location: two servers writing to one
+location break each other's catalog.
+
+```
+occ backup:key:import /path/ng_backup-kit.json --passphrase-file=/path/passphrase
+occ backup:target:add offsite <backend> ...          # same details as on the original server
+occ backup:list offsite                              # the snapshots must be listed
+occ backup:restore:full offsite <snapshot>
+```
+
+The command refuses on an installation that already has more than one user, and asks before it
+starts; `--force` skips both (also needed to rerun it after it stopped halfway).
+
+Afterwards, check that users, files and the database are complete, and run a backup of the restored
+server. The restored installation keeps its own app configuration and secret.
+
+## 8. Retention
+
+```
+occ backup:retention --last=3 --daily=7 --weekly=4 --monthly=12
+occ backup:prune offsite --dry-run   # show first
+occ backup:prune offsite             # apply the policy; forgotten snapshots go to the trash first
+occ backup:trash                  # list the trash
+occ backup:trash:restore offsite <id>
+```
+
+Snapshots are kept according to the policy, and their data is deleted only after the deletion delay
+(set with `backup:key:init --delete-delay-days`). `occ backup:prune offsite --dry-run` shows what would be
+removed without changing anything.
+
+## 9. Checklist before you rely on it
+
+- [ ] Key created, passphrase stored off-server, recovery kit stored off-server
+- [ ] Location added; `backup:status` shows it reachable
+- [ ] First backup done and listed in `backup:list`
+- [ ] `backup:verify --deep` succeeds
+- [ ] One file restore tested (`new-folder`)
+- [ ] Disaster recovery tested on a second, fresh installation (or in a test environment)

lib/AppInfo/Application.php

@@ -12,7 +12,7 @@ use OCP\AppFramework\Bootstrap\IBootContext;
 use OCP\AppFramework\Bootstrap\IBootstrap;
 use OCP\AppFramework\Bootstrap\IRegistrationContext;
 
-class Application extends App implements IBootstrap {
+final class Application extends App implements IBootstrap {
 	public const APP_ID = 'ng_backup';
 
 	public function __construct() {
@@ -20,6 +20,8 @@ class Application extends App implements IBootstrap {
 	}
 
 	public function register(IRegistrationContext $context): void {
+		$context->registerNotifierService(\OCA\NgBackup\Notification\Notifier::class);
+		$context->registerSetupCheck(\OCA\NgBackup\SetupCheck\BackupStatusCheck::class);
 	}
 
 	public function boot(IBootContext $context): void {

lib/Backend/BackendException.php

@@ -7,5 +7,5 @@ declare(strict_types=1);
 
 namespace OCA\NgBackup\Backend;
 
-class BackendException extends \RuntimeException {
+final class BackendException extends \RuntimeException {
 }

lib/Backend/IBackend.php

@@ -27,8 +27,25 @@ interface IBackend {
 
 	public function exists(string $path): bool;
 
+	/**
+	 * Move an object within the same location (used for the trash). Backends must use a native
+	 * rename, not a read+write copy: some storages (e.g. SFTP) cannot reliably read and write on
+	 * the same connection at once, since the read side is a lazily-pulled stream.
+	 */
+	public function move(string $from, string $to): void;
+
 	/** @return list<string> object paths below $prefix (recursive) */
 	public function list(string $prefix): array;
 
+	/**
+	 * Object paths directly in $dir, for a folder that only holds objects (index/, snapshots/,
+	 * catalog/, trash/info/). One listing, without checking the type of every entry: on a remote
+	 * storage list() costs a round trip per entry, which for index/ (one file per pack) grows
+	 * with the size of the repository.
+	 *
+	 * @return list<string>
+	 */
+	public function listFiles(string $dir): array;
+
 	public function delete(string $path): void;
 }

lib/Backend/LocalBackend.php

@@ -33,11 +33,16 @@ final class LocalBackend implements IBackend {
 			if ($out === false) {
 				throw new BackendException('Cannot write ' . $path);
 			}
+			$expected = StorageBackend::remaining($stream);
 			if (stream_copy_to_stream($stream, $out) === false || !fflush($out)) {
 				throw new BackendException('Write failed for ' . $path);
 			}
 			fclose($out);
 			$out = false;
+			clearstatcache(true, $tmp);
+			if ($expected !== null && filesize($tmp) !== $expected) {
+				throw new BackendException('Incomplete write for ' . $path);
+			}
 			if (!rename($tmp, $target)) {
 				throw new BackendException('Cannot finalise ' . $path);
 			}
@@ -94,7 +99,7 @@ final class LocalBackend implements IBackend {
 		$result = [];
 		$it = new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($base, \FilesystemIterator::SKIP_DOTS));
 		foreach ($it as $file) {
-			if ($file->isFile() && !str_contains($file->getFilename(), '.part-')) {
+			if ($file->isFile() && !StorageBackend::isTemporary($file->getFilename())) {
 				$result[] = ltrim(substr($file->getPathname(), strlen($this->root)), '/');
 			}
 		}
@@ -102,10 +107,40 @@ final class LocalBackend implements IBackend {
 		return $result;
 	}
 
+	public function listFiles(string $dir): array {
+		$base = $this->abs($dir);
+		if (!is_dir($base)) {
+			return [];
+		}
+		$result = [];
+		$names = scandir($base);
+		if ($names === false) {
+			throw new BackendException('Cannot list ' . $dir);
+		}
+		foreach ($names as $name) {
+			if ($name !== '.' && $name !== '..' && !StorageBackend::isTemporary($name)) {
+				$result[] = trim($dir, '/') . '/' . $name;
+			}
+		}
+		sort($result);
+		return $result;
+	}
+
 	public function delete(string $path): void {
 		@unlink($this->abs($path));
 	}
 
+	public function move(string $from, string $to): void {
+		$target = $this->abs($to);
+		$dir = dirname($target);
+		if (!is_dir($dir) && !mkdir($dir, 0700, true) && !is_dir($dir)) {
+			throw new BackendException('Cannot create ' . $dir);
+		}
+		if (!rename($this->abs($from), $target)) {
+			throw new BackendException("Cannot move $from to $to");
+		}
+	}
+
 	private function abs(string $path): string {
 		if (str_contains($path, '..') || str_starts_with($path, '/')) {
 			throw new BackendException('Invalid path: ' . $path);

lib/Backend/StorageBackend.php

@@ -30,7 +30,13 @@ final class StorageBackend implements IBackend {
 		}
 	}
 
+	/** A temporary upload of put(): "<name>.part-<8 hex>". */
+	public static function isTemporary(string $name): bool {
+		return preg_match('/\.part-[0-9a-f]{8}$/', $name) === 1;
+	}
+
 	public function put(string $path, $stream): void {
+		$expected = self::remaining($stream);
 		$target = $this->abs($path);
 		$this->mkdirs(dirname($target));
 		$writeTo = $this->atomicPut ? $target : $target . '.part-' . bin2hex(random_bytes(4));
@@ -54,6 +60,10 @@ final class StorageBackend implements IBackend {
 			if (is_resource($stream)) {
 				fclose($stream);
 			}
+			// Some adapters report success after a short write or a failed flush: check the size.
+			if ($expected !== null && $this->storage->filesize($writeTo) !== $expected) {
+				throw new BackendException('Incomplete write for ' . $path);
+			}
 			if ($writeTo !== $target && !$this->storage->rename($writeTo, $target)) {
 				throw new BackendException('Cannot finalise ' . $path);
 			}
@@ -115,6 +125,36 @@ final class StorageBackend implements IBackend {
 		$this->storage->unlink($this->abs($path));
 	}
 
+	public function move(string $from, string $to): void {
+		$target = $this->abs($to);
+		$this->mkdirs(dirname($target));
+		if (!$this->storage->rename($this->abs($from), $target)) {
+			throw new BackendException("Cannot move $from to $to");
+		}
+	}
+
+	public function listFiles(string $dir): array {
+		$abs = $this->abs($dir);
+		if (!$this->storage->is_dir($abs)) {
+			return []; // not created yet
+		}
+		$dh = $this->storage->opendir($abs);
+		if ($dh === false) {
+			// An existing folder read as empty would look like a new repository.
+			throw new BackendException('Cannot list ' . $dir);
+		}
+		$cut = $this->base === '' ? 0 : strlen($this->base) + 1;
+		$result = [];
+		while (($name = readdir($dh)) !== false) {
+			if ($name !== '.' && $name !== '..' && !self::isTemporary($name)) {
+				$result[] = substr($abs . '/' . $name, $cut);
+			}
+		}
+		closedir($dh);
+		sort($result);
+		return $result;
+	}
+
 	private function listInto(string $dir, array &$result): void {
 		if (!$this->storage->is_dir($dir)) {
 			return;
@@ -124,19 +164,39 @@ final class StorageBackend implements IBackend {
 			return;
 		}
 		while (($name = readdir($dh)) !== false) {
-			if ($name === '.' || $name === '..' || str_contains($name, '.part-')) {
+			if ($name === '.' || $name === '..') {
 				continue;
 			}
 			$child = $dir . '/' . $name;
 			if ($this->storage->is_dir($child)) {
 				$this->listInto($child, $result);
-			} else {
+			} elseif (!self::isTemporary($name)) {
 				$result[] = $child;
 			}
 		}
 		closedir($dh);
 	}
 
+	/**
+	 * Bytes left to read in a local $stream (php://temp, php://memory or a plain file), or null:
+	 * stream wrappers of remote storages do not report a reliable size.
+	 */
+	public static function remaining(mixed $stream): ?int {
+		if (!is_resource($stream)) {
+			return null;
+		}
+		$meta = stream_get_meta_data($stream);
+		if (!($meta['seekable'] ?? false) || !in_array($meta['wrapper_type'] ?? '', ['PHP', 'plainfile'], true)) {
+			return null;
+		}
+		$stat = fstat($stream);
+		$pos = ftell($stream);
+		if ($stat === false || $pos === false) {
+			return null;
+		}
+		return max(0, $stat['size'] - $pos);
+	}
+
 	private function mkdirs(string $dir): void {
 		if ($dir === '' || $dir === '.' || $this->storage->is_dir($dir)) {
 			return;

lib/BackgroundJob/BackupJob.php

@@ -22,10 +22,12 @@ use Psr\Log\LoggerInterface;
  * With system cron a step may take minutes; with webcron/AJAX cron it is kept short so it fits
  * in a normal web request (hosted Nextcloud).
  */
-class BackupJob extends TimedJob {
+final class BackupJob extends TimedJob {
 	public function __construct(
 		ITimeFactory $time,
 		private BackupService $backups,
+		private \OCA\NgBackup\Service\PruneService $prune,
+		private \OCA\NgBackup\Service\AlertService $alerts,
 		private TargetService $targets,
 		private RunMapper $runs,
 		private IAppConfig $appConfig,
@@ -36,15 +38,63 @@ class BackupJob extends TimedJob {
 		$this->setTimeSensitivity(IJob::TIME_SENSITIVE);
 	}
 
+	private const MAX_DAILY_ATTEMPTS = 3;
+
 	protected function run($argument): void {
 		$budget = PHP_SAPI === 'cli' ? 240.0 : 20.0;
 		$deadline = microtime(true) + $budget;
 		$this->startScheduled();
 		foreach ($this->runs->findRunning(null, BackupService::KIND_FULL) as $run) {
 			while (microtime(true) < $deadline && $run->getStatus() === 'running') {
-				$run = $this->backups->step($run, min($deadline, microtime(true) + $budget));
+				$next = $this->backups->step($run, min($deadline, microtime(true) + $budget));
+				if ($next === $run) {
+					break; // step() hands back the same object when another process holds the run's lease
+				}
+				$run = $next;
 			}
 		}
+		$this->failStaleRestores();
+		$this->weeklyPrune();
+		foreach ($this->targets->list() as $t) {
+			$this->alerts->checkStale($t);
+		}
+	}
+
+	/** A restore run that has not moved for 6 hours is considered dead (it would block cleanup forever). */
+	private function failStaleRestores(): void {
+		foreach ($this->runs->findRunning(null, 'restore') as $run) {
+			if (time() - $run->getUpdatedAt() > 6 * 3600) {
+				$run->setStatus(\OCA\NgBackup\Db\Run::FAILED);
+				$run->setError('No progress for 6 hours; marked as failed');
+				$run->setFinishedAt(time());
+				$this->runs->update($run);
+				$this->alerts->runFailed($run, '#' . $run->getTargetId());
+			}
+		}
+	}
+
+	/**
+	 * Once a week, apply the retention policy to non-append-only locations: from Sunday on, at the
+	 * first moment no backup is running, so a long Sunday backup only delays it instead of skipping
+	 * the week.
+	 */
+	private function weeklyPrune(): void {
+		$lastWeek = $this->appConfig->getValueString(Application::APP_ID, 'last_prune_week', '');
+		$due = date('N') === '7' ? date('o-W') : date('o-W', (int)strtotime('last sunday'));
+		if (strcmp($lastWeek, $due) >= 0 || $this->runs->findRunning(null, BackupService::KIND_FULL) !== []) {
+			return;
+		}
+		foreach ($this->targets->list() as $t) {
+			if ($t->getAppendOnly()) {
+				continue;
+			}
+			try {
+				$this->prune->apply($t, false, true);
+			} catch (\Throwable $e) {
+				$this->logger->warning('NG Backup: cleanup of ' . $t->getName() . ' failed: ' . $e->getMessage());
+			}
+		}
+		$this->appConfig->setValueString(Application::APP_ID, 'last_prune_week', $due);
 	}
 
 	/** Daily schedule: appconfig ng_backup/schedule_time "HH:MM" (server time); empty = no schedule. */
@@ -53,7 +103,7 @@ class BackupJob extends TimedJob {
 		if (!preg_match('/^([01]\d|2[0-3]):[0-5]\d$/', $at)) {
 			return;
 		}
-		$todayAt = strtotime(date('Y-m-d') . ' ' . $at);
+		$todayAt = (int)strtotime(date('Y-m-d') . ' ' . $at);
 		if (time() < $todayAt) {
 			return;
 		}
@@ -62,6 +112,12 @@ class BackupJob extends TimedJob {
 			if ($this->runs->findRunning($t->getId(), BackupService::KIND_FULL) !== [] || ($last !== null && $last->getStartedAt() >= $todayAt)) {
 				continue;
 			}
+			// After a failure: retry at most MAX_DAILY_ATTEMPTS times a day, an hour apart, instead
+			// of starting (and notifying about) a new full run every five minutes all day.
+			$today = $this->runs->startedSince($t->getId(), BackupService::KIND_FULL, $todayAt);
+			if (count($today) >= self::MAX_DAILY_ATTEMPTS || ($today !== [] && time() - (int)$today[0]->getFinishedAt() < 3600)) {
+				continue;
+			}
 			try {
 				$this->backups->start($t, 'scheduled');
 			} catch (\Throwable $e) {

lib/BackgroundJob/RestoreJob.php

@@ -16,29 +16,46 @@ use OCP\BackgroundJob\QueuedJob;
 use Psr\Log\LoggerInterface;
 
 /** Runs a restore requested from the web interface, outside the web request. */
-class RestoreJob extends QueuedJob {
+final class RestoreJob extends QueuedJob {
 	public function __construct(
 		ITimeFactory $time,
 		private RunMapper $runs,
 		private TargetService $targets,
 		private RestoreService $restore,
 		private LoggerInterface $logger,
+		private \OCA\NgBackup\Service\AlertService $alerts,
 	) {
 		parent::__construct($time);
 	}
 
 	protected function run($argument): void {
-		$run = $this->runs->find((int)$argument['run']);
+		$runId = (int)($argument['run'] ?? 0);
+		try {
+			$run = $this->runs->find($runId);
+		} catch (\Throwable $e) {
+			$this->logger->error('NG Backup restore job: run ' . $runId . ' not found', ['exception' => $e]);
+			return;
+		}
 		if ($run->getStatus() !== Run::RUNNING) {
 			return;
 		}
-		$req = json_decode($run->getState(), true, 512, JSON_THROW_ON_ERROR);
-		$run->setPhase('restoring');
-		$run->setUpdatedAt(time());
-		$this->runs->update($run);
-		@set_time_limit(0);
 		try {
-			$result = $this->restore->restoreUserFiles($this->targets->get((string)$run->getTargetId()), $req['snapshot'], $req['path'], $req['mode']);
+			$req = json_decode($run->getState(), true, 512, JSON_THROW_ON_ERROR);
+			$run->setPhase('restoring');
+			$run->setUpdatedAt(time());
+			$run = $this->runs->update($run);
+			@set_time_limit(0);
+			$lastBeat = time();
+			$result = $this->restore->restoreUserFiles($this->targets->get((string)$run->getTargetId()), $req['snapshot'], $req['path'], $req['mode'],
+				function (int $done, int $total) use (&$run, &$lastBeat): void {
+					// Heartbeat, so a long restore is not mistaken for a dead one.
+					if (time() - $lastBeat >= 60) {
+						$lastBeat = time();
+						$run->setPhase("restoring $done/$total");
+						$run->setUpdatedAt(time());
+						$run = $this->runs->update($run);
+					}
+				});
 			$run->setStatus(Run::DONE);
 			$run->setPhase('done');
 			$run->setStats(json_encode($result, JSON_THROW_ON_ERROR));
@@ -46,6 +63,10 @@ class RestoreJob extends QueuedJob {
 			$this->logger->error('NG Backup restore ' . $run->getId() . ' failed: ' . $e->getMessage(), ['exception' => $e]);
 			$run->setStatus(Run::FAILED);
 			$run->setError($e->getMessage());
+			try {
+				$this->alerts->runFailed($run, '#' . $run->getTargetId());
+			} catch (\Throwable) {
+			}
 		}
 		$run->setFinishedAt(time());
 		$run->setUpdatedAt(time());

lib/Command/BackupUser.php

@@ -0,0 +1,64 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\TargetService;
+use OCA\NgBackup\Service\UserBackupService;
+use OCA\NgBackup\UserMigration\UserMigrationInstaller;
+use OCP\IUserManager;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class BackupUser extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private UserBackupService $userBackup,
+		private IUserManager $userManager,
+		private UserMigrationInstaller $installer,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:user:backup')
+			->setDescription('Back up one user via user_migration (account, settings, files and everything else a migrator covers)')
+			->addArgument('target', InputArgument::REQUIRED, 'Location name or id')
+			->addArgument('user', InputArgument::REQUIRED, 'User id')
+			->addOption('install-user-migration', null, InputOption::VALUE_NONE, 'Install and enable user_migration if it is missing (non-interactive consent)')
+			->setHelp(<<<'HELP'
+Streams a user_migration export straight into the encrypted repository: no zip, no copy in the
+user's own storage. Shares data with the regular backup; this needs the user_migration app
+enabled. The manifest path this prints is what occ backup:user:restore expects.
+
+Example:
+  occ backup:user:backup offsite alice
+HELP);
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$uid = (string)$input->getArgument('user');
+		$user = $this->userManager->get($uid);
+		if ($user === null) {
+			$output->writeln("<error>No such user: $uid</error>");
+			return 1;
+		}
+		try {
+			$target = $this->targets->get($input->getArgument('target'));
+			$this->installer->ensureEnabled($input, $output);
+			$manifest = $this->userBackup->backupUser($target, $user);
+		} catch (\Throwable $e) {
+			$output->writeln('<error>' . $e->getMessage() . '</error>');
+			return 1;
+		}
+		$output->writeln("Backed up <info>$uid</info> to $manifest.");
+		return 0;
+	}
+}

lib/Command/Browse.php

@@ -15,7 +15,7 @@ use Symfony\Component\Console\Input\InputArgument;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class Browse extends Command {
+final class Browse extends Command {
 	public function __construct(
 		private TargetService $targets,
 		private RestoreService $restore,

lib/Command/KeyConfirm.php

@@ -14,7 +14,7 @@ use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 use Symfony\Component\Console\Question\Question;
 
-class KeyConfirm extends Command {
+final class KeyConfirm extends Command {
 	public const STATEMENT = 'I have downloaded the recovery kit and stored it safely, outside this server. '
 		. 'I understand that keeping these keys safe is my own responsibility and that backups cannot be restored without them.';
 	public const CONFIRMATION = 'Yes, I confirm';
@@ -28,7 +28,9 @@ class KeyConfirm extends Command {
 	protected function configure(): void {
 		$this->setName('backup:key:confirm')
 			->setDescription('Confirm that the recovery kit is stored safely (required before the first backup)')
-			->addOption('user', 'u', InputOption::VALUE_REQUIRED, 'Admin user id recorded with the confirmation', 'occ');
+			->addOption('user', 'u', InputOption::VALUE_REQUIRED, 'Admin user id recorded with the confirmation', 'occ')
+			->addOption('code', null, InputOption::VALUE_REQUIRED, 'Confirmation code from the kit file (for scripts; asked otherwise)')
+			->addOption('confirm', null, InputOption::VALUE_REQUIRED, 'The confirmation phrase "' . self::CONFIRMATION . '" (for scripts; asked otherwise)');
 	}
 
 	protected function execute(InputInterface $input, OutputInterface $output): int {
@@ -40,7 +42,12 @@ class KeyConfirm extends Command {
 		$output->writeln('');
 		$output->writeln(wordwrap(self::STATEMENT, 78));
 		$output->writeln('');
-		$answer = (string)$this->getHelper('question')->ask($input, $output, new Question('Type "' . self::CONFIRMATION . '" to proceed: '));
+		$code = $input->getOption('code') ?? (string)$this->getHelper('question')->ask($input, $output, new Question('Confirmation code from the recovery kit file ("confirmation_code"): '));
+		if (!$this->keys->checkKitCode($code)) {
+			$output->writeln('<error>That code does not match the current recovery kit (download it with occ backup:key:kit first).</error>');
+			return 1;
+		}
+		$answer = $input->getOption('confirm') ?? (string)$this->getHelper('question')->ask($input, $output, new Question('Type "' . self::CONFIRMATION . '" to proceed: '));
 		if (trim($answer) !== self::CONFIRMATION) {
 			$output->writeln('<error>Not confirmed.</error>');
 			return 1;

lib/Command/KeyImport.php

@@ -0,0 +1,85 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\KeyService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Question\Question;
+
+final class KeyImport extends Command {
+	public function __construct(
+		private KeyService $keys,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:key:import')
+			->setDescription('Disaster recovery: adopt the backup key from a recovery kit on a fresh installation')
+			->addArgument('kit-file', InputArgument::REQUIRED, 'The recovery kit file (occ backup:key:kit on the original installation)')
+			->addOption('passphrase-file', null, InputOption::VALUE_REQUIRED, 'Read the passphrase from this file instead of asking')
+			->setHelp(<<<'HELP'
+For a fresh installation only (occ backup:key:init must not have been run here yet). Reads one
+of the kit's passphrase slots to recover the original master key, so occ backup:target:add opens
+the existing repository on the location instead of creating a new, empty one.
+
+Example:
+  occ backup:key:import /root/ng_backup-recovery-kit.json
+  occ backup:target:add offsite sftp -a password::password -o host=... -o user=... -o password=...
+  occ backup:restore:full offsite <snapshot>
+HELP);
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		if ($this->keys->isInitialized()) {
+			$output->writeln('<error>A backup key already exists here (fingerprint ' . $this->keys->fingerprint() . '). occ backup:key:import is only for a fresh installation.</error>');
+			return 1;
+		}
+		$kitFile = (string)$input->getArgument('kit-file');
+		$raw = @file_get_contents($kitFile);
+		if ($raw === false) {
+			$output->writeln("<error>Cannot read $kitFile</error>");
+			return 1;
+		}
+		try {
+			$kit = json_decode($raw, true, 512, JSON_THROW_ON_ERROR);
+		} catch (\JsonException $e) {
+			$output->writeln('<error>Not a valid recovery kit file: ' . $e->getMessage() . '</error>');
+			return 1;
+		}
+		$file = $input->getOption('passphrase-file');
+		if ($file !== null) {
+			$raw = @file_get_contents($file);
+			if ($raw === false) {
+				$output->writeln('<error>Cannot read the passphrase file</error>');
+				return 1;
+			}
+			$pass = rtrim($raw, "\r\n");
+		} else {
+			$helper = $this->getHelper('question');
+			$q = (new Question('Passphrase of one of the kit\'s slots: '))->setHidden(true)->setHiddenFallback(false);
+			$pass = (string)$helper->ask($input, $output, $q);
+		}
+		try {
+			$this->keys->importRecoveryKit($kit, $pass);
+		} catch (\Throwable $e) {
+			$output->writeln('<error>' . $e->getMessage() . '</error>');
+			return 1;
+		}
+		$output->writeln('Backup key imported, fingerprint <info>' . $this->keys->fingerprint() . '</info>.');
+		// Read from the kit file, which is not authenticated beyond the wrapped key: show it so a
+		// wrong or altered value stands out.
+		$output->writeln('Deletion delay for forgotten snapshots: <info>' . $this->keys->deleteDelayDays() . '</info> days (from the kit).');
+		$output->writeln('Next: connect the backup location with the same details as before (<info>occ backup:target:add</info>), then <info>occ backup:list</info> and <info>occ backup:restore:full</info>.');
+		return 0;
+	}
+}

lib/Command/KeyInit.php

@@ -14,7 +14,7 @@ use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 use Symfony\Component\Console\Question\Question;
 
-class KeyInit extends Command {
+final class KeyInit extends Command {
 	public function __construct(
 		private KeyService $keys,
 	) {
@@ -25,6 +25,8 @@ class KeyInit extends Command {
 		$this->setName('backup:key:init')
 			->setDescription('Create the backup key, protected by a passphrase you keep safe')
 			->addOption('passphrase-file', null, InputOption::VALUE_REQUIRED, 'Read the passphrase from this file instead of asking')
+			->addOption('label', 'l', InputOption::VALUE_REQUIRED, 'Label of the first passphrase slot (who/where), e.g. "Safe"', 'Slot 1')
+			->addOption('delete-delay-days', null, InputOption::VALUE_REQUIRED, 'Days a removed snapshot stays in the trash before its data is deleted (1-365, fixed after this)', (string)KeyService::DEFAULT_DELETE_DELAY)
 			->setHelp(<<<'HELP'
 Creates the master key that encrypts all backups of this installation.
 
@@ -57,12 +59,14 @@ HELP);
 			}
 		}
 		try {
-			$this->keys->initialize($pass);
+			$this->keys->initialize($pass, (int)$input->getOption('delete-delay-days'), (string)$input->getOption('label'));
 		} catch (\InvalidArgumentException $e) {
 			$output->writeln('<error>' . $e->getMessage() . '</error>');
 			return 1;
 		}
 		$output->writeln('Backup key created, fingerprint <info>' . $this->keys->fingerprint() . '</info>.');
+		$output->writeln('Removed snapshots stay in the trash on the location for <info>' . $this->keys->deleteDelayDays() . ' days</info> (cannot be changed later).');
+		$output->writeln('Tip: add up to two more passphrases for other people with occ backup:key:slot:add (e.g. CTO, head of IT).');
 		$output->writeln('Next: save the recovery kit with <info>occ backup:key:kit --output=FILE</info> and confirm with <info>occ backup:key:confirm</info>.');
 		return 0;
 	}

lib/Command/KeyKit.php

@@ -13,9 +13,10 @@ use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class KeyKit extends Command {
+final class KeyKit extends Command {
 	public function __construct(
 		private KeyService $keys,
+		private \OCA\NgBackup\Service\AlertService $alerts,
 	) {
 		parent::__construct();
 	}
@@ -31,17 +32,31 @@ class KeyKit extends Command {
 			$output->writeln('<error>No backup key yet: run occ backup:key:init first.</error>');
 			return 1;
 		}
+		$this->alerts->securityEvent('kit_downloaded');
 		$json = json_encode($this->keys->recoveryKit(), JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_THROW_ON_ERROR) . "\n";
 		$file = $input->getOption('output');
 		if ($file === null) {
 			$output->write($json, false, OutputInterface::OUTPUT_RAW);
 			return 0;
 		}
-		if (file_put_contents($file, $json) === false) {
+		// Created owner-only from the start (no window where it is world-readable), never over an
+		// existing file or symlink someone else may have placed at a predictable path.
+		$old = umask(0077);
+		try {
+			$fh = @fopen($file, 'xb');
+		} finally {
+			umask($old);
+		}
+		if ($fh === false) {
+			$output->writeln("<error>Cannot create $file (it must not exist yet)</error>");
+			return 1;
+		}
+		$ok = fwrite($fh, $json) === strlen($json);
+		if (!fclose($fh) || !$ok) {
+			@unlink($file);
 			$output->writeln("<error>Cannot write $file</error>");
 			return 1;
 		}
-		@chmod($file, 0600);
 		$output->writeln("Recovery kit written to <info>$file</info>. Copy it off this server, then run <info>occ backup:key:confirm</info>.");
 		return 0;
 	}

lib/Command/KeySlotAdd.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\KeyService;
+use OCA\NgBackup\Service\KeySlotService;
+
+final class KeySlotAdd extends KeySlots {
+	public function __construct(KeyService $keys, KeySlotService $slots) {
+		parent::__construct($keys, $slots, 'add');
+	}
+}

lib/Command/KeySlotRemove.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\KeyService;
+use OCA\NgBackup\Service\KeySlotService;
+
+final class KeySlotRemove extends KeySlots {
+	public function __construct(KeyService $keys, KeySlotService $slots) {
+		parent::__construct($keys, $slots, 'remove');
+	}
+}

lib/Command/KeySlotReplace.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\KeyService;
+use OCA\NgBackup\Service\KeySlotService;
+
+final class KeySlotReplace extends KeySlots {
+	public function __construct(KeyService $keys, KeySlotService $slots) {
+		parent::__construct($keys, $slots, 'replace');
+	}
+}

lib/Command/KeySlots.php

@@ -0,0 +1,97 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\KeyService;
+use OCA\NgBackup\Service\KeySlotService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Helper\Table;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Question\Question;
+
+/** backup:key:slots, backup:key:slot:add, backup:key:slot:replace, backup:key:slot:remove */
+class KeySlots extends Command {
+	public function __construct(
+		private KeyService $keys,
+		private KeySlotService $slots,
+		private string $action = 'list',
+	) {
+		// list is the default; subclasses pick another action
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$help = <<<'HELP'
+Up to three passphrases ("slots") can open the backup key, so that one person leaving or dying
+does not lock you out. Example: one passphrase in the safe, one with the CTO, one with the head
+of IT. Each holder keeps a copy of the same recovery kit and only knows their own passphrase.
+After every change: occ backup:key:kit and occ backup:key:confirm.
+HELP;
+		match ($this->action) {
+			'add' => $this->setName('backup:key:slot:add')->setDescription('Add a passphrase slot')
+				->addOption('label', 'l', InputOption::VALUE_REQUIRED, 'Who or where, e.g. "CTO" or "Safe"', 'Slot'),
+			'replace' => $this->setName('backup:key:slot:replace')->setDescription('Set a new passphrase for a slot (e.g. its holder left)')
+				->addArgument('slot', InputArgument::REQUIRED, 'Slot number (see backup:key:slots)')
+				->addOption('label', 'l', InputOption::VALUE_REQUIRED, 'New label'),
+			'remove' => $this->setName('backup:key:slot:remove')->setDescription('Remove a passphrase slot (not the last one)')
+				->addArgument('slot', InputArgument::REQUIRED, 'Slot number (see backup:key:slots)'),
+			default => $this->setName('backup:key:slots')->setDescription('List the passphrase slots of the backup key'),
+		};
+		if ($this->action === 'add' || $this->action === 'replace') {
+			$this->addOption('passphrase-file', null, InputOption::VALUE_REQUIRED, 'Read the passphrase from this file');
+		}
+		$this->setHelp($help);
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		if (!$this->keys->isInitialized()) {
+			$output->writeln('<error>No backup key yet: run occ backup:key:init first.</error>');
+			return 1;
+		}
+		try {
+			switch ($this->action) {
+				case 'add':
+					$n = $this->slots->add($this->passphrase($input, $output), (string)$input->getOption('label'));
+					$output->writeln("Slot $n added.");
+					break;
+				case 'replace':
+					$this->slots->replace((int)$input->getArgument('slot'), $this->passphrase($input, $output), $input->getOption('label'));
+					$output->writeln('Slot ' . (int)$input->getArgument('slot') . ' has a new passphrase.');
+					break;
+				case 'remove':
+					$this->slots->remove((int)$input->getArgument('slot'));
+					$output->writeln('Slot ' . (int)$input->getArgument('slot') . ' removed.');
+					break;
+				default:
+					(new Table($output))->setHeaders(['slot', 'label', 'set on'])
+						->setRows(array_map(fn ($s) => [$s['slot'], $s['label'], $s['created'] ? date('Y-m-d H:i', $s['created']) : ''], $this->keys->slots()))->render();
+					return 0;
+			}
+		} catch (\Throwable $e) {
+			$output->writeln('<error>' . $e->getMessage() . '</error>');
+			return 1;
+		}
+		$output->writeln('Now download and confirm the new recovery kit: occ backup:key:kit -o FILE && occ backup:key:confirm');
+		return 0;
+	}
+
+	private function passphrase(InputInterface $input, OutputInterface $output): string {
+		if ($file = $input->getOption('passphrase-file')) {
+			return rtrim((string)@file_get_contents($file), "\r\n");
+		}
+		$h = $this->getHelper('question');
+		$p = (string)$h->ask($input, $output, (new Question('Passphrase (min. 12 characters): '))->setHidden(true)->setHiddenFallback(false));
+		if ($p !== (string)$h->ask($input, $output, (new Question('Repeat: '))->setHidden(true)->setHiddenFallback(false))) {
+			throw new \InvalidArgumentException('The passphrases do not match');
+		}
+		return $p;
+	}
+}

lib/Command/ListSnapshots.php

@@ -15,7 +15,7 @@ use Symfony\Component\Console\Input\InputArgument;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class ListSnapshots extends Command {
+final class ListSnapshots extends Command {
 	public function __construct(
 		private TargetService $targets,
 		private SnapshotMapper $snapshots,

lib/Command/Prune.php

@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\PruneService;
+use OCA\NgBackup\Service\TargetService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class Prune extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private PruneService $prune,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:prune')
+			->setDescription('Apply the retention policy: remove old snapshots and the data only they used')
+			->addArgument('target', InputArgument::OPTIONAL, 'Location name or id (default: all that are not append-only)')
+			->addOption('dry-run', null, InputOption::VALUE_NONE, 'Only show what would be removed');
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$name = $input->getArgument('target');
+		$targets = $name === null ? array_filter($this->targets->list(), fn ($t) => !$t->getAppendOnly()) : [$this->targets->get($name)];
+		$dry = (bool)$input->getOption('dry-run');
+		$output->writeln('Policy: ' . json_encode($this->prune->policy()->toArray()) . ($dry ? ' (dry run)' : ''));
+		$rc = 0;
+		foreach ($targets as $t) {
+			// User exports first: Repository::prune()'s blob garbage collection (run as part of
+			// apply() below) scans the users/ manifests still on the location at that point, so
+			// forgetting one here lets its now-unused blobs be freed in this same pass.
+			try {
+				$ru = $this->prune->applyUserExports($t, $dry);
+			} catch (\Throwable $e) {
+				// Snapshot retention is independent of this: report and carry on with it.
+				$output->writeln('<error>' . $t->getName() . ' (user exports): ' . $e->getMessage() . '</error>');
+				$rc = 1;
+				$ru = ['forgotten' => []];
+			}
+			if ($ru['forgotten'] !== []) {
+				$affected = count(array_unique(array_map(static fn (string $path): string => explode('/', $path)[1] ?? '', $ru['forgotten'])));
+				$output->writeln(sprintf('<info>%s</info>: %s %d user export(s) for %d user(s)',
+					$t->getName(), $dry ? 'would forget' : 'forgot', count($ru['forgotten']), $affected));
+			}
+			try {
+				$r = $this->prune->apply($t, $dry);
+			} catch (\Throwable $e) {
+				$output->writeln('<error>' . $t->getName() . ': ' . $e->getMessage() . '</error>');
+				$rc = 1;
+				continue;
+			}
+			$p = $r['prune'];
+			$output->writeln(sprintf('<info>%s</info>: keep %d, %s %d snapshots; packs: %d, %s %d, repack %d, frees %.1f MiB',
+				$t->getName(), count($r['kept']), $dry ? 'would forget' : 'forgot', count($r['forgotten']), $p['packs'],
+				$dry ? 'would delete' : 'deleted', $p['deleted'], $p['repacked'], $p['freedBytes'] / 1048576));
+		}
+		return $rc;
+	}
+}

lib/Command/Restore.php

@@ -15,7 +15,7 @@ use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class Restore extends Command {
+final class Restore extends Command {
 	public function __construct(
 		private TargetService $targets,
 		private RestoreService $restore,
@@ -49,7 +49,7 @@ HELP);
 		try {
 			$target = $this->targets->get($input->getArgument('target'));
 			$snapshot = $input->getArgument('snapshot');
-			$path = $input->getArgument('path');
+			$path = trim((string)$input->getArgument('path'), '/'); // CLI convenience; the service itself only accepts canonical paths
 			if ($dir = $input->getOption('to-directory')) {
 				$n = $this->restore->restoreToDirectory($target, $snapshot, $path, $dir);
 				$output->writeln("Restored <info>$n</info> files to $dir.");

lib/Command/RestoreFull.php

@@ -0,0 +1,97 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\RestoreFullService;
+use OCA\NgBackup\Service\TargetService;
+use OCP\IUserManager;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Helper\QuestionHelper;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Question\ConfirmationQuestion;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class RestoreFull extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private RestoreFullService $restoreFull,
+		private IUserManager $userManager,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:restore:full')
+			->setDescription('Disaster recovery: restore the database, data directory and config on a fresh installation')
+			->addArgument('target', InputArgument::REQUIRED, 'Location name or id')
+			->addArgument('snapshot', InputArgument::REQUIRED, 'Snapshot id (see backup:list)')
+			->addOption('force', null, InputOption::VALUE_NONE, 'Also on an installation that already has more than one user, and without asking')
+			->setHelp(<<<'HELP'
+For a FRESH Nextcloud installation only, same major version as the backup, right after
+occ maintenance:install, occ backup:key:import and occ backup:target:add -- before anyone else
+uses this instance.
+
+Every app that was enabled when the snapshot was taken must already be installed here (its
+database tables must exist before the restore can write into them); the command lists what is
+missing and refuses to continue rather than guess.
+
+Steps: the database is replaced (consistent, in one transaction); the data directory is restored
+directly in place; config.php is merged in -- everything from the backup except the database
+connection and data directory settings, which stay as occ maintenance:install configured them
+here. Other files under config/ (if any) are not restored.
+
+Afterwards: check trusted_domains and overwritehost/overwriteprotocol match this server, and
+occ maintenance:repair.
+
+Example:
+  occ backup:restore:full offsite 537bf7e9c1a4...
+HELP);
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$force = (bool)$input->getOption('force');
+		// A whole-server restore replaces the database and data directory of THIS instance. On
+		// anything but a fresh install (only the admin from occ maintenance:install) that is
+		// almost certainly a mistake, so it needs --force.
+		$users = $this->userManager->countUsersTotal(2);
+		if (!$force && ($users === false || $users > 1)) {
+			$output->writeln('<error>This installation already has more than one user: backup:restore:full would replace its whole database and data directory. It is meant for a fresh installation. Use --force if this really is what you want.</error>');
+			return 1;
+		}
+		if (!$force && $input->isInteractive()) {
+			$q = new ConfirmationQuestion('This replaces the database, the data directory and config.php of this installation. Continue? [y/N] ', false);
+			if (!(new QuestionHelper())->ask($input, $output, $q)) {
+				$output->writeln('Cancelled.');
+				return 1;
+			}
+		}
+		try {
+			$target = $this->targets->get($input->getArgument('target'));
+			$snapshot = (string)$input->getArgument('snapshot');
+			$result = $this->restoreFull->restoreFull($target, $snapshot);
+		} catch (\Throwable $e) {
+			$output->writeln('<error>' . $e->getMessage() . '</error>');
+			$output->writeln('If this happened after the restore had started, the instance may be partly restored: fix the cause and run the same command again with --force.');
+			return 1;
+		}
+		$output->writeln(sprintf(
+			'Database restored (<info>%d</info> tables, <info>%d</info> unchanged), config merged (<info>%d</info> keys), <info>%d</info> data files restored.',
+			count($result['dbReport']['restored']),
+			count($result['dbReport']['skipped']),
+			$result['configKeys'],
+			$result['dataFiles'],
+		));
+		if (!$result['dbConsistent']) {
+			$output->writeln('<comment>Warning: this snapshot\'s database dump was made over several steps (web cron), so it is not one consistent point in time. Check the instance carefully; prefer a snapshot made with system cron.</comment>');
+		}
+		$output->writeln('Next: check trusted_domains and overwritehost/overwriteprotocol match this server, then occ maintenance:repair.');
+		return 0;
+	}
+}

lib/Command/RestoreUser.php

@@ -0,0 +1,82 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\TargetService;
+use OCA\NgBackup\Service\UserRestoreService;
+use OCA\NgBackup\UserMigration\UserMigrationInstaller;
+use OCP\IUserManager;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Helper\QuestionHelper;
+use Symfony\Component\Console\Question\ConfirmationQuestion;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class RestoreUser extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private UserRestoreService $userRestore,
+		private UserMigrationInstaller $installer,
+		private IUserManager $userManager,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:user:restore')
+			->setDescription('Restore a user from a user_migration export (see backup:user:backup)')
+			->addArgument('target', InputArgument::REQUIRED, 'Location name or id')
+			->addArgument('manifest', InputArgument::REQUIRED, 'Manifest path printed by backup:user:backup (users/<uid>/<exportId>)')
+			->addOption('mode', 'm', InputOption::VALUE_REQUIRED, 'replace or as-backup', UserRestoreService::MODE_REPLACE)
+			->addOption('force', null, InputOption::VALUE_NONE, 'Replace an existing account without asking (required when not interactive)')
+			->addOption('install-user-migration', null, InputOption::VALUE_NONE, 'Install and enable user_migration if it is missing (non-interactive consent)')
+			->setHelp(<<<'HELP'
+Never imports over a live account. Modes:
+  replace    (default) safety-exports the current account first, then deletes and recreates it
+             fresh from the backup, under the same user id
+  as-backup  restores into a new account "<uid>-bak" (or "-bak-2", ...) instead, so an admin can
+             compare and transfer by hand; Nextcloud cannot rename a user id, so the backup gets
+             the new name, never the existing account
+
+Example:
+  occ backup:user:restore offsite users/alice/20261005T120000Z-ab12cd34
+  occ backup:user:restore offsite users/alice/20261005T120000Z-ab12cd34 --mode=as-backup
+HELP);
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$mode = (string)$input->getOption('mode');
+		$uid = explode('/', (string)$input->getArgument('manifest'))[1] ?? '';
+		if ($mode === UserRestoreService::MODE_REPLACE && $uid !== '' && $this->userManager->userExists($uid) && !$input->getOption('force')) {
+			// Replace deletes the live account (after a safety export). Shares to others and data of
+			// apps without a user_migration migrator do not come back, so never do it unasked.
+			if (!$input->isInteractive()) {
+				$output->writeln("<error>$uid exists: --mode=replace deletes and recreates it. Add --force, or use --mode=as-backup.</error>");
+				return 1;
+			}
+			$q = new ConfirmationQuestion("$uid exists and will be deleted and recreated from the backup (a safety export is made first; its shares to others and data of apps without a migrator are not restored). Continue? [y/N] ", false);
+			if (!(new QuestionHelper())->ask($input, $output, $q)) {
+				$output->writeln('Cancelled.');
+				return 1;
+			}
+		}
+		try {
+			$output->writeln('<comment>Note: on restore, user_migration only imports the app settings on its own allowlist (e.g. calendar view and reminder settings); other app settings of this user are skipped. Reason: NG Backup uses user_migration\'s importer; widening the list would mean building a settings importer of our own.</comment>');
+			$target = $this->targets->get($input->getArgument('target'));
+			$this->installer->ensureEnabled($input, $output);
+			$user = $this->userRestore->restoreUser($target, (string)$input->getArgument('manifest'), $mode);
+		} catch (\Throwable $e) {
+			$output->writeln('<error>' . $e->getMessage() . '</error>');
+			return 1;
+		}
+		$output->writeln('Restored <info>' . $user->getUID() . '</info>.');
+		return 0;
+	}
+}

lib/Command/Retention.php

@@ -0,0 +1,68 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\PruneService;
+use OCA\NgBackup\Service\RetentionPolicy;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class Retention extends Command {
+	public function __construct(
+		private PruneService $prune,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:retention')
+			->setDescription('Show or set how many snapshots are kept')
+			->addOption('last', null, InputOption::VALUE_REQUIRED, 'Always keep the newest N')
+			->addOption('daily', null, InputOption::VALUE_REQUIRED, 'Keep one per day for the last N days with a backup')
+			->addOption('weekly', null, InputOption::VALUE_REQUIRED, 'Keep one per week for N weeks')
+			->addOption('monthly', null, InputOption::VALUE_REQUIRED, 'Keep one per month for N months')
+			->addOption('user-last', null, InputOption::VALUE_REQUIRED, 'Keep the newest N of each user\'s own exports (occ backup:user:backup)')
+			->setHelp("Example: occ backup:retention --last=3 --daily=7 --weekly=4 --monthly=12 --user-last=3");
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		if ($input->getOption('user-last') !== null && !ctype_digit((string)$input->getOption('user-last'))) {
+			$output->writeln('<error>--user-last must be a whole number</error>');
+			return 1;
+		}
+		$p = $this->prune->policy()->toArray();
+		$changed = false;
+		foreach (['last', 'daily', 'weekly', 'monthly'] as $k) {
+			if ($input->getOption($k) !== null) {
+				$p[$k] = max(0, (int)$input->getOption($k));
+				$changed = true;
+			}
+		}
+		if ($changed) {
+			try {
+				$this->prune->setPolicy(RetentionPolicy::fromArray($p));
+			} catch (\InvalidArgumentException $e) {
+				$output->writeln('<error>' . $e->getMessage() . '</error>');
+				return 1;
+			}
+		}
+		if ($input->getOption('user-last') !== null) {
+			try {
+				$this->prune->setUserExportRetention((int)$input->getOption('user-last'));
+			} catch (\InvalidArgumentException $e) {
+				$output->writeln('<error>' . $e->getMessage() . '</error>');
+				return 1;
+			}
+		}
+		$output->writeln(sprintf('Keep the last %d, plus one per day for %d days, per week for %d weeks, per month for %d months.', $p['last'], $p['daily'], $p['weekly'], $p['monthly']));
+		$output->writeln(sprintf('Keep the newest %d of each user\'s own exports.', $this->prune->userExportRetention()));
+		return 0;
+	}
+}

lib/Command/RunBackup.php

@@ -16,7 +16,7 @@ use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class RunBackup extends Command {
+final class RunBackup extends Command {
 	public function __construct(
 		private BackupService $backups,
 		private TargetService $targets,
@@ -75,6 +75,13 @@ HELP);
 			});
 			if ($run->getStatus() === Run::DONE) {
 				$output->writeln(sprintf('  done in %.0fs', microtime(true) - $start));
+				$f = json_decode($run->getStats() ?? '{}', true)['files'] ?? [];
+				if (($f['unreadable'] ?? 0) > 0) {
+					$output->writeln(sprintf('<comment>  warning: %d unreadable files or folders are missing from this backup (see the server log)</comment>', $f['unreadable']));
+				}
+				if (($f['changing'] ?? 0) > 0) {
+					$output->writeln(sprintf('<comment>  warning: %d files kept changing and were saved as read (see the server log)</comment>', $f['changing']));
+				}
 			} else {
 				$output->writeln('<error>  ' . $run->getStatus() . ': ' . $run->getError() . '</error>');
 				$failed++;

lib/Command/Status.php

@@ -15,7 +15,7 @@ use Symfony\Component\Console\Helper\Table;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class Status extends Command {
+final class Status extends Command {
 	public function __construct(
 		private KeyService $keys,
 		private TargetService $targets,

lib/Command/TargetAdd.php

@@ -15,7 +15,7 @@ use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class TargetAdd extends Command {
+final class TargetAdd extends Command {
 	public function __construct(
 		private TargetService $targets,
 		private KeyService $keys,

lib/Command/TargetAppendOnly.php

@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\TargetService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class TargetAppendOnly extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private \OCA\NgBackup\Service\AlertService $alerts,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:target:append-only')
+			->setDescription('Make a location append-only (NG Backup never deletes there) or normal again')
+			->addArgument('target', InputArgument::REQUIRED, 'Location name or id')
+			->addArgument('state', InputArgument::REQUIRED, 'on or off')
+			->setHelp("Append-only protects backups if this server is compromised: combine it with credentials\nwithout delete rights and a lifecycle rule or object lock on the location itself.");
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$state = strtolower((string)$input->getArgument('state'));
+		if (!in_array($state, ['on', 'off'], true)) {
+			$output->writeln('<error>state must be on or off</error>');
+			return 1;
+		}
+		$t = $this->targets->setAppendOnly($this->targets->get($input->getArgument('target')), $state === 'on');
+		if ($state === 'off') {
+			$this->alerts->securityEvent('append_only_off', ['target' => $t->getName()]);
+		}
+		$output->writeln($t->getName() . ' is ' . ($t->getAppendOnly() ? 'append-only' : 'normal') . '.');
+		return 0;
+	}
+}

lib/Command/TargetBackends.php

@@ -12,7 +12,7 @@ use OCA\NgBackup\Service\TargetService;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class TargetBackends extends Base {
+final class TargetBackends extends Base {
 	public function __construct(
 		private TargetService $targets,
 	) {

lib/Command/TargetLimit.php

@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\TargetService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class TargetLimit extends Command {
+	public function __construct(
+		private TargetService $targets,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:target:limit')
+			->setDescription('Set a maximum size for the backups stored on a location (e.g. 100G), or "none"')
+			->addArgument('target', InputArgument::REQUIRED, 'Location name or id')
+			->addArgument('size', InputArgument::OPTIONAL, 'Size like 500M, 20G, 2T, or "none"; omit to show the current limit')
+			->setHelp("A backup that would exceed the limit stops with an error and administrators are notified.\n"
+				. "Note: with versioning or Object Lock on the location, removed data keeps using space there\n"
+				. "until it expires; keep the limit below what you are willing to pay for.");
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$t = $this->targets->get($input->getArgument('target'));
+		$size = $input->getArgument('size');
+		if ($size !== null) {
+			if (strtolower($size) === 'none') {
+				$t = $this->targets->setMaxBytes($t, null);
+			} elseif (preg_match('/^(\d+(?:\.\d+)?)\s*([KMGT]?)i?B?$/i', $size, $m)) {
+				$factor = ['' => 1, 'K' => 1024, 'M' => 1024 ** 2, 'G' => 1024 ** 3, 'T' => 1024 ** 4][strtoupper($m[2])];
+				$t = $this->targets->setMaxBytes($t, (int)round((float)$m[1] * $factor));
+			} else {
+				$output->writeln('<error>Use a size like 500M, 20G or 2T, or "none".</error>');
+				return 1;
+			}
+		}
+		$used = $this->targets->repository($t)->storedBytes();
+		$output->writeln(sprintf('%s: %.2f GiB stored, limit %s', $t->getName(), $used / 1073741824,
+			$t->getMaxBytes() === null ? 'none' : sprintf('%.2f GiB', $t->getMaxBytes() / 1073741824)));
+		return 0;
+	}
+}

lib/Command/TargetList.php

@@ -13,7 +13,7 @@ use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Input\InputOption;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class TargetList extends Base {
+final class TargetList extends Base {
 	public function __construct(
 		private TargetService $targets,
 	) {

lib/Command/TargetRemove.php

@@ -13,9 +13,10 @@ use Symfony\Component\Console\Input\InputArgument;
 use Symfony\Component\Console\Input\InputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
-class TargetRemove extends Command {
+final class TargetRemove extends Command {
 	public function __construct(
 		private TargetService $targets,
+		private \OCA\NgBackup\Service\AlertService $alerts,
 	) {
 		parent::__construct();
 	}
@@ -34,6 +35,7 @@ class TargetRemove extends Command {
 			return 1;
 		}
 		$this->targets->remove($t);
+		$this->alerts->securityEvent('target_removed', ['target' => $t->getName()]);
 		$output->writeln('Removed <info>' . $t->getName() . '</info>. The backups on the location itself were not touched; add it again to use them.');
 		return 0;
 	}

lib/Command/TargetTrustCurrent.php

@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Db\AppConfigCatalogAnchor;
+use OCA\NgBackup\Service\AlertService;
+use OCA\NgBackup\Service\TargetService;
+use OCP\IAppConfig;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Question\Question;
+
+/**
+ * Accept the state a location shows now, after NG Backup refused it as rolled back. Only for
+ * legitimate cases (e.g. the location was restored from the provider's own snapshot), only from
+ * occ, audited and announced to all administrators.
+ */
+final class TargetTrustCurrent extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private IAppConfig $appConfig,
+		private AlertService $alerts,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:target:trust-current')
+			->setDescription('Accept the current state of a location that was refused as rolled back')
+			->addArgument('target', InputArgument::REQUIRED, 'Location name or id')
+			->setHelp("NG Backup refuses a location whose backup catalog is older than what this server saw\n"
+				. "before, because an attacker could have restored an old state. If you restored the location\n"
+				. "yourself (e.g. from the provider's snapshot), accept it with this command.");
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$t = $this->targets->get($input->getArgument('target'));
+		$output->writeln('<comment>Only continue if you know why the location shows an older state.</comment>');
+		$answer = (string)$this->getHelper('question')->ask($input, $output, new Question('Type the location name to accept its current state: '));
+		if ($answer !== $t->getName()) {
+			$output->writeln('<error>Not confirmed.</error>');
+			return 1;
+		}
+		$this->appConfig->deleteKey('ng_backup', 'catalog_' . preg_replace('/[^a-f0-9]/', '', (string)$t->getRepositoryId()));
+		$repo = $this->targets->repository($t); // re-anchors on the newest valid catalog
+		$this->alerts->securityEvent('catalog_trusted', ['target' => $t->getName(), 'generation' => (string)$repo->catalogGeneration()]);
+		$output->writeln(sprintf('Accepted generation %d of %s (%d snapshots).', $repo->catalogGeneration(), $t->getName(), count($repo->listSnapshots())));
+		return 0;
+	}
+}

lib/Command/Trash.php

@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\KeyService;
+use OCA\NgBackup\Service\TargetService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Helper\Table;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class Trash extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private KeyService $keys,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:trash')
+			->setDescription('List removed snapshots that can still be restored (backup:trash:restore)')
+			->addArgument('target', InputArgument::OPTIONAL, 'Location name or id (default: all)');
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		$name = $input->getArgument('target');
+		$delay = $this->keys->deleteDelayDays() * 86400;
+		$rows = [];
+		foreach ($name === null ? $this->targets->list() : [$this->targets->get($name)] as $t) {
+			foreach ($this->targets->repository($t)->trash() as $id => $info) {
+				$rows[] = [$t->getName(), $id, (string)($info['time'] ?? ''), $info['label'], date('Y-m-d H:i', $info['forgottenAt']), $info['by'],
+					date('Y-m-d H:i', $info['forgottenAt'] + $delay)];
+			}
+		}
+		if ($rows === []) {
+			$output->writeln('The trash is empty.');
+			return 0;
+		}
+		(new Table($output))->setHeaders(['location', 'snapshot', 'made', 'label', 'removed', 'by', 'deleted after'])->setRows($rows)->render();
+		return 0;
+	}
+}

lib/Command/TrashRestore.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\PruneService;
+use OCA\NgBackup\Service\TargetService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class TrashRestore extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private PruneService $prune,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:trash:restore')
+			->setDescription('Bring a removed snapshot back from the trash')
+			->addArgument('target', InputArgument::REQUIRED, 'Location name or id')
+			->addArgument('snapshot', InputArgument::REQUIRED, 'Snapshot id (see backup:trash)');
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		try {
+			$this->prune->untrash($this->targets->get($input->getArgument('target')), $input->getArgument('snapshot'));
+		} catch (\Throwable $e) {
+			$output->writeln('<error>' . $e->getMessage() . '</error>');
+			return 1;
+		}
+		$output->writeln('Snapshot restored from the trash.');
+		return 0;
+	}
+}

lib/Command/Verify.php

@@ -0,0 +1,81 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Command;
+
+use OCA\NgBackup\Service\TargetService;
+use OCA\NgBackup\Service\VerifyService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputArgument;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class Verify extends Command {
+	public function __construct(
+		private TargetService $targets,
+		private VerifyService $verify,
+	) {
+		parent::__construct();
+	}
+
+	protected function configure(): void {
+		$this->setName('backup:verify')
+			->setDescription('Checksum audit of a snapshot: every blob it needs must be in the (freshly re-checked) index and its pack present')
+			->addArgument('target', InputArgument::REQUIRED, 'Location name or id')
+			->addArgument('snapshot', InputArgument::REQUIRED, 'Snapshot id (see backup:list)')
+			->addOption('deep', null, InputOption::VALUE_NONE, 'Also download and decrypt every blob (verifies its authentication tag and content hash, not just that it is listed); much slower')
+			->setHelp(<<<'HELP'
+Without --deep this re-downloads and re-authenticates the index (never trusting the local cache)
+and confirms every blob the snapshot needs is listed and its pack is present -- fast, no blob
+content is read, so it cannot by itself catch a truncated or bit-rotted pack. With --deep every
+blob is also downloaded and decrypted, which fails loudly on exactly that even if the index still
+lists it -- the same verification an actual restore would do, run here deliberately instead of
+waiting to find out during one.
+
+Run this periodically (cron, picking a sample of recent snapshots) rather than only right before
+you'd need to rely on a restore.
+
+Examples:
+  occ backup:verify offsite 537bf7e9c1a4...
+  occ backup:verify offsite 537bf7e9c1a4... --deep
+HELP);
+	}
+
+	protected function execute(InputInterface $input, OutputInterface $output): int {
+		try {
+			$target = $this->targets->get($input->getArgument('target'));
+			$ref = (string)$input->getArgument('snapshot');
+			$deep = (bool)$input->getOption('deep');
+			$result = str_starts_with($ref, 'users/')
+				? $this->verify->verifyUserExport($target, $ref, $deep)
+				: $this->verify->verify($target, $ref, $deep);
+		} catch (\Throwable $e) {
+			$output->writeln('<error>' . $e->getMessage() . '</error>');
+			return 1;
+		}
+		$output->writeln(sprintf('%d files, %d blobs checked%s.', $result['filesChecked'], $result['blobsChecked'],
+			$deep ? sprintf(' (%.1f MiB decrypted)', $result['bytesChecked'] / 1048576) : ''));
+		if ($result['missing'] !== []) {
+			$output->writeln('<error>' . count($result['missing']) . ' blob(s) missing from the index:</error> ' . implode(', ', $result['missing']));
+		}
+		if ($result['failed'] !== []) {
+			$output->writeln('<error>' . count($result['failed']) . ' blob(s) failed verification (corrupted or tampered):</error> ' . implode(', ', $result['failed']));
+		}
+		if ($result['unreadable'] !== []) {
+			$output->writeln('<error>' . count($result['unreadable']) . ' blob(s) could not be read from the location</error> (often a temporary storage '
+				. 'or network error: run the check again; if the same blobs stay unreadable, their pack may be damaged or truncated): '
+				. implode(', ', $result['unreadable']));
+			$output->writeln('Last read error: ' . $result['readError']);
+		}
+		if ($result['missing'] === [] && $result['failed'] === [] && $result['unreadable'] === []) {
+			$output->writeln('<info>OK</info>');
+			return 0;
+		}
+		return 1;
+	}
+}

lib/Controller/AdminApiController.php

@@ -19,6 +19,8 @@ use OCA\NgBackup\Service\RestoreService;
 use OCA\NgBackup\Service\TargetService;
 use OCP\AppFramework\Controller;
 use OCP\AppFramework\Http;
+use OCP\AppFramework\Http\Attribute\NoCSRFRequired;
+use OCP\AppFramework\Http\Attribute\PasswordConfirmationRequired;
 use OCP\AppFramework\Http\DataDownloadResponse;
 use OCP\AppFramework\Http\JSONResponse;
 use OCP\BackgroundJob\IJobList;
@@ -30,7 +32,7 @@ use OCP\IUserSession;
  * JSON API for the admin settings page. Every method requires an admin (the AppFramework
  * default for controllers without NoAdminRequired) and a valid CSRF token.
  */
-class AdminApiController extends Controller {
+final class AdminApiController extends Controller {
 	public function __construct(
 		IRequest $request,
 		private KeyService $keys,
@@ -42,6 +44,9 @@ class AdminApiController extends Controller {
 		private IAppConfig $appConfig,
 		private IJobList $jobs,
 		private IUserSession $session,
+		private \OCA\NgBackup\Service\AlertService $alerts,
+		private \OCA\NgBackup\Service\KeySlotService $slots,
+		private \OCA\NgBackup\Service\PruneService $prune,
 	) {
 		parent::__construct(Application::APP_ID, $request);
 	}
@@ -50,12 +55,15 @@ class AdminApiController extends Controller {
 		$targets = [];
 		foreach ($this->targets->list() as $t) {
 			$targets[] = ['id' => $t->getId(), 'name' => $t->getName(), 'backend' => $t->getBackend(), 'path' => $t->getBasePath(),
-				'repositoryId' => $t->getRepositoryId(), 'createdAt' => $t->getCreatedAt()];
+				'repositoryId' => $t->getRepositoryId(), 'createdAt' => $t->getCreatedAt(), 'appendOnly' => (bool)$t->getAppendOnly(),
+				'maxBytes' => $t->getMaxBytes(), 'storedBytes' => $this->alerts->lastStoredBytes($t)];
 		}
 		$runs = array_map(fn (Run $r) => $this->runJson($r), $this->runs->findRecent(15));
 		return new JSONResponse([
 			'key' => ['initialized' => $this->keys->isInitialized(), 'fingerprint' => $this->keys->fingerprint(),
-				'confirmation' => $this->keys->recoveryKitConfirmation()],
+				'confirmation' => $this->keys->recoveryKitConfirmation(), 'everConfirmed' => $this->keys->isInitialized() && $this->keys->everConfirmed(),
+				'slots' => $this->keys->isInitialized() ? $this->keys->slots() : [], 'maxSlots' => \OCA\NgBackup\Service\KeyService::MAX_SLOTS,
+				'deleteDelayDays' => $this->keys->isInitialized() ? $this->keys->deleteDelayDays() : \OCA\NgBackup\Service\KeyService::DEFAULT_DELETE_DELAY],
 			'statement' => KeyConfirm::STATEMENT,
 			'confirmationPhrase' => KeyConfirm::CONFIRMATION,
 			'targets' => $targets,
@@ -64,47 +72,127 @@ class AdminApiController extends Controller {
 		]);
 	}
 
-	public function initKey(string $passphrase): JSONResponse {
+	#[PasswordConfirmationRequired]
+	public function initKey(string $passphrase, int $deleteDelayDays = \OCA\NgBackup\Service\KeyService::DEFAULT_DELETE_DELAY, string $label = 'Slot 1'): JSONResponse {
 		try {
-			$this->keys->initialize($passphrase);
+			$this->keys->initialize($passphrase, $deleteDelayDays, $label);
 		} catch (\Throwable $e) {
 			return new JSONResponse(['error' => $e->getMessage()], Http::STATUS_BAD_REQUEST);
 		}
 		return new JSONResponse(['fingerprint' => $this->keys->fingerprint()]);
 	}
 
+	/**
+	 * Plain download link (no CSRF token on a navigation), therefore guarded by a recent password
+	 * confirmation instead, logged to the audit log and announced to all administrators. The kit
+	 * only holds the passphrase-wrapped key: useless without the passphrase.
+	 */
+	#[NoCSRFRequired]
+	#[PasswordConfirmationRequired]
 	public function downloadKit(): DataDownloadResponse|JSONResponse {
 		if (!$this->keys->isInitialized()) {
 			return new JSONResponse(['error' => 'No backup key yet'], Http::STATUS_BAD_REQUEST);
 		}
+		$this->alerts->securityEvent('kit_downloaded');
 		$json = json_encode($this->keys->recoveryKit(), JSON_PRETTY_PRINT | JSON_UNESCAPED_SLASHES | JSON_THROW_ON_ERROR);
 		return new DataDownloadResponse($json, 'ng_backup-recovery-kit-' . $this->keys->fingerprint() . '.json', 'application/json');
 	}
 
-	/** The admin must tick the statement and send the exact confirmation phrase. */
-	public function confirmKit(bool $accepted, string $phrase): JSONResponse {
+	/** The admin must tick the statement, send the exact phrase and the code from the kit file. */
+	#[PasswordConfirmationRequired]
+	public function confirmKit(bool $accepted, string $phrase, string $code = ''): JSONResponse {
 		if (!$accepted || $phrase !== KeyConfirm::CONFIRMATION) {
 			return new JSONResponse(['error' => 'Not confirmed'], Http::STATUS_BAD_REQUEST);
 		}
+		if (!$this->keys->checkKitCode($code)) {
+			return new JSONResponse(['error' => 'The confirmation code does not match the current recovery kit'], Http::STATUS_BAD_REQUEST);
+		}
 		$this->keys->confirmRecoveryKit($this->session->getUser()?->getUID() ?? 'unknown');
 		return new JSONResponse(['confirmation' => $this->keys->recoveryKitConfirmation()]);
 	}
 
+	#[PasswordConfirmationRequired]
+	public function addSlot(string $passphrase, string $label): JSONResponse {
+		try {
+			return new JSONResponse(['slot' => $this->slots->add($passphrase, $label)]);
+		} catch (\Throwable $e) {
+			return new JSONResponse(['error' => $e->getMessage()], Http::STATUS_BAD_REQUEST);
+		}
+	}
+
+	#[PasswordConfirmationRequired]
+	public function replaceSlot(int $slot, string $passphrase, ?string $label = null): JSONResponse {
+		try {
+			$this->slots->replace($slot, $passphrase, $label);
+			return new JSONResponse([]);
+		} catch (\Throwable $e) {
+			return new JSONResponse(['error' => $e->getMessage()], Http::STATUS_BAD_REQUEST);
+		}
+	}
+
+	#[PasswordConfirmationRequired]
+	public function removeSlot(int $slot): JSONResponse {
+		try {
+			$this->slots->remove($slot);
+			return new JSONResponse([]);
+		} catch (\Throwable $e) {
+			return new JSONResponse(['error' => $e->getMessage()], Http::STATUS_BAD_REQUEST);
+		}
+	}
+
+	public function trash(int $targetId): JSONResponse {
+		try {
+			$delay = $this->keys->deleteDelayDays() * 86400;
+			$out = [];
+			foreach ($this->targets->repository($this->targets->get((string)$targetId))->trash() as $id => $info) {
+				$out[] = ['id' => $id, 'label' => $info['label'], 'time' => $info['time'], 'removedAt' => $info['forgottenAt'],
+					'by' => $info['by'], 'deleteAfter' => $info['forgottenAt'] + $delay];
+			}
+			return new JSONResponse($out);
+		} catch (\Throwable $e) {
+			return new JSONResponse(['error' => $e->getMessage()], Http::STATUS_BAD_REQUEST);
+		}
+	}
+
+	#[PasswordConfirmationRequired]
+	public function untrash(int $targetId, string $snapshotId): JSONResponse {
+		try {
+			$this->prune->untrash($this->targets->get((string)$targetId), $snapshotId);
+			return new JSONResponse([]);
+		} catch (\Throwable $e) {
+			return new JSONResponse(['error' => $e->getMessage()], Http::STATUS_BAD_REQUEST);
+		}
+	}
+
 	public function backends(): JSONResponse {
 		return new JSONResponse($this->targets->availableBackends());
 	}
 
-	public function addTarget(string $name, string $backend, string $auth, array $options = [], string $path = 'ng_backup'): JSONResponse {
+	#[PasswordConfirmationRequired]
+	public function addTarget(string $name, string $backend, string $auth, array $options = [], string $path = 'ng_backup', ?float $maxGb = null): JSONResponse {
 		try {
 			$r = $this->targets->add($name, $backend, $auth, $options, $path);
+			if ($maxGb !== null && $maxGb > 0) {
+				$this->targets->setMaxBytes($r['target'], (int)round($maxGb * 1073741824));
+			}
 		} catch (\Throwable $e) {
 			return new JSONResponse(['error' => $e->getMessage()], Http::STATUS_BAD_REQUEST);
 		}
 		return new JSONResponse(['id' => $r['target']->getId(), 'created' => $r['created']]);
 	}
 
+	/** Size limit in GiB; null or 0 = unlimited. */
+	#[PasswordConfirmationRequired]
+	public function setTargetLimit(int $id, ?float $maxGb = null): JSONResponse {
+		$t = $this->targets->setMaxBytes($this->targets->get((string)$id), ($maxGb !== null && $maxGb > 0) ? (int)round($maxGb * 1073741824) : null);
+		return new JSONResponse(['maxBytes' => $t->getMaxBytes()]);
+	}
+
+	#[PasswordConfirmationRequired]
 	public function removeTarget(int $id): JSONResponse {
-		$this->targets->remove($this->targets->get((string)$id));
+		$target = $this->targets->get((string)$id);
+		$this->targets->remove($target);
+		$this->alerts->securityEvent('target_removed', ['target' => $target->getName()]);
 		return new JSONResponse([]);
 	}
 
@@ -152,13 +240,19 @@ class AdminApiController extends Controller {
 	}
 
 	/** Queue a restore of user files; it runs as a background job and shows up in the runs. */
+	#[PasswordConfirmationRequired]
 	public function startRestore(int $targetId, string $snapshotId, string $path, string $mode = RestoreService::MODE_NEW_FOLDER): JSONResponse {
 		if (!in_array($mode, [RestoreService::MODE_NEW_FOLDER, RestoreService::MODE_MERGE, RestoreService::MODE_REPLACE], true)
-			|| !preg_match('#^data/[^/]+/files(/.*)?$#', $path)) {
+			|| !\OCA\NgBackup\Repository\Repository::isSafePath($path) || !preg_match('#^data/[^/]+/files(/.*)?$#', $path)) {
 			return new JSONResponse(['error' => 'Invalid path or mode'], Http::STATUS_BAD_REQUEST);
 		}
+		try {
+			$target = $this->targets->get((string)$targetId);
+		} catch (\Throwable) {
+			return new JSONResponse(['error' => 'No such location'], Http::STATUS_NOT_FOUND);
+		}
 		$run = new Run();
-		$run->setTargetId($targetId);
+		$run->setTargetId($target->getId());
 		$run->setKind('restore');
 		$run->setStatus(Run::RUNNING);
 		$run->setPhase('queued');
@@ -167,14 +261,27 @@ class AdminApiController extends Controller {
 		$run->setSnapshotId($snapshotId);
 		$run->setStartedAt(time());
 		$run->setUpdatedAt(time());
-		$run = $this->runs->insert($run);
+		try {
+			$run = $this->prune->underStartLock($target, fn () => $this->runs->insert($run));
+		} catch (\Throwable $e) {
+			return new JSONResponse(['error' => $e->getMessage()], Http::STATUS_CONFLICT);
+		}
 		$this->jobs->add(RestoreJob::class, ['run' => $run->getId()]);
 		return new JSONResponse($this->runJson($run));
 	}
 
 	private function runJson(Run $r): array {
+		$snapshot = null;
+		if ($r->getSnapshotId() !== null) {
+			try {
+				$s = $this->snapshots->findOne($r->getTargetId(), $r->getSnapshotId());
+				$snapshot = ['createdAt' => $s->getCreatedAt(), 'label' => $s->getLabel()];
+			} catch (\Throwable) {
+				// Snapshot already pruned or trashed: the run keeps its id, just not the date.
+			}
+		}
 		return ['id' => $r->getId(), 'targetId' => $r->getTargetId(), 'kind' => $r->getKind(), 'status' => $r->getStatus(),
-			'phase' => $r->getPhase(), 'snapshotId' => $r->getSnapshotId(), 'startedAt' => $r->getStartedAt(),
+			'phase' => $r->getPhase(), 'snapshotId' => $r->getSnapshotId(), 'snapshot' => $snapshot, 'startedAt' => $r->getStartedAt(),
 			'updatedAt' => $r->getUpdatedAt(), 'finishedAt' => $r->getFinishedAt(), 'error' => $r->getError(),
 			'stats' => json_decode($r->getStats() ?? 'null', true)];
 	}

lib/Crypto/CryptoException.php

@@ -7,5 +7,5 @@ declare(strict_types=1);
 
 namespace OCA\NgBackup\Crypto;
 
-class CryptoException extends \RuntimeException {
+final class CryptoException extends \RuntimeException {
 }

lib/Crypto/KeyRing.php

@@ -76,9 +76,32 @@ final class KeyRing {
 		];
 	}
 
+	/**
+	 * Open a key field that is either one wrapped key or {"slots": [{slot, label, key}, ...]}:
+	 * every slot holds the same master key under its own passphrase.
+	 */
+	public static function unwrapAny(array $field, #[\SensitiveParameter] string $passphrase): self {
+		if (!isset($field['slots'])) {
+			return self::unwrap($field, $passphrase);
+		}
+		foreach ($field['slots'] as $slot) {
+			try {
+				return self::unwrap($slot['key'], $passphrase);
+			} catch (CryptoException) {
+			}
+		}
+		throw new CryptoException('Wrong passphrase or damaged key');
+	}
+
 	/** @param array{v:int, salt:string, ops:int, mem:int, nonce:string, key:string} $wrapped */
 	public static function unwrap(array $wrapped, #[\SensitiveParameter] string $passphrase): self {
 		$b64 = static fn (string $s): string => sodium_base642bin($s, SODIUM_BASE64_VARIANT_ORIGINAL);
+		// ops/mem come from unauthenticated JSON (kit file, repository config): bound them, so a
+		// damaged or crafted file cannot make the KDF use unbounded memory or time.
+		if ($wrapped['ops'] < SODIUM_CRYPTO_PWHASH_OPSLIMIT_INTERACTIVE || $wrapped['ops'] > SODIUM_CRYPTO_PWHASH_OPSLIMIT_SENSITIVE
+			|| $wrapped['mem'] < SODIUM_CRYPTO_PWHASH_MEMLIMIT_INTERACTIVE || $wrapped['mem'] > SODIUM_CRYPTO_PWHASH_MEMLIMIT_SENSITIVE) {
+			throw new CryptoException('Unsupported key derivation parameters (damaged or foreign key file)');
+		}
 		$kek = sodium_crypto_pwhash(SODIUM_CRYPTO_SECRETBOX_KEYBYTES, $passphrase, $b64($wrapped['salt']),
 			$wrapped['ops'], $wrapped['mem'], SODIUM_CRYPTO_PWHASH_ALG_ARGON2ID13);
 		$master = sodium_crypto_secretbox_open($b64($wrapped['key']), $b64($wrapped['nonce']), $kek);

lib/Crypto/StreamCipher.php

@@ -122,6 +122,7 @@ final class StreamCipher {
 	/** fread() may return short reads on network streams; keep reading until $length or EOF. */
 	private static function readFull($in, int $length): string {
 		$buffer = '';
+		$empty = 0;
 		while (strlen($buffer) < $length && !feof($in)) {
 			$chunk = fread($in, $length - strlen($buffer));
 			if ($chunk === false) {
@@ -132,8 +133,15 @@ final class StreamCipher {
 				if (feof($in)) {
 					break;
 				}
+				// A stalled network stream returns '' without EOF forever: back off, then give up
+				// (about a minute) instead of spinning at full CPU until the lease expires.
+				if (++$empty > 600) {
+					throw new CryptoException('Read stalled');
+				}
+				usleep(100000);
 				continue;
 			}
+			$empty = 0;
 			$buffer .= $chunk;
 		}
 		return $buffer;

lib/Db/AppConfigCatalogAnchor.php

@@ -0,0 +1,34 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Db;
+
+use OCA\NgBackup\AppInfo\Application;
+use OCA\NgBackup\Repository\ICatalogAnchor;
+use OCP\IAppConfig;
+
+/** Keeps the newest catalog generation seen per repository in the app config (outside the location). */
+final class AppConfigCatalogAnchor implements ICatalogAnchor {
+	public function __construct(
+		private IAppConfig $appConfig,
+	) {
+	}
+
+	public function get(string $repositoryId): ?array {
+		$raw = $this->appConfig->getValueString(Application::APP_ID, $this->key($repositoryId), '', true);
+		$data = $raw === '' ? null : json_decode($raw, true);
+		return is_array($data) && isset($data['gen'], $data['hash']) ? ['gen' => (int)$data['gen'], 'hash' => (string)$data['hash']] : null;
+	}
+
+	public function set(string $repositoryId, int $gen, string $hash): void {
+		$this->appConfig->setValueString(Application::APP_ID, $this->key($repositoryId), json_encode(['gen' => $gen, 'hash' => $hash]), true);
+	}
+
+	private function key(string $repositoryId): string {
+		return 'catalog_' . preg_replace('/[^a-f0-9]/', '', $repositoryId);
+	}
+}

lib/Db/DbDumper.php

@@ -31,6 +31,8 @@ use OCA\NgBackup\Repository\Repository;
  */
 final class DbDumper {
 	private const BATCH = 2000;
+	/** Rows per INSERT on restore; keeps the number of bound parameters well below database limits. */
+	private const INSERT_ROWS = 100;
 	/** Tables without a primary key are read in one query; refuse that above this size. */
 	private const MAX_ROWS_WITHOUT_PK = 50000;
 
@@ -41,39 +43,94 @@ final class DbDumper {
 	}
 
 	/**
-	 * @return array{tables: array<string, array{blobs: list<string>, rows: int, bytes: int, sha256: string}>, provider: string}
+	 * Dump everything in one go (one transaction, fully consistent).
+	 *
+	 * @return array{tables: array<string, array{blobs: list<string>, rows: int, bytes: int, sha256: string}>, sequences: array, provider: string, consistent: bool}
 	 */
 	public function dump(Repository $repo, array &$stats): array {
-		$sm = $this->db->createSchemaManager();
-		$tables = array_values(array_filter($sm->listTableNames(), fn (string $t) => str_starts_with($t, $this->prefix)));
-		sort($tables);
+		$state = $this->startDump();
+		while (!$state['done']) {
+			$state = $this->dumpStep($repo, $state, PHP_FLOAT_MAX, $stats);
+		}
+		return $this->manifest($state);
+	}
 
-		$this->db->setTransactionIsolation(TransactionIsolationLevel::REPEATABLE_READ);
-		$this->db->beginTransaction();
+	/** State for a resumable dump (see dumpStep()). */
+	public function startDump(): array {
+		$tables = array_values(array_filter($this->db->createSchemaManager()->listTableNames(), fn (string $t) => str_starts_with($t, $this->prefix)));
+		sort($tables);
+		return ['tables' => $tables, 'i' => 0, 'after' => null, 'segments' => [], 'rows' => 0, 'bytes' => 0, 'hash' => null,
+			'result' => [], 'sequences' => [], 'steps' => 0, 'done' => false];
+	}
+
+	/**
+	 * Dump tables until $deadline, inside one REPEATABLE READ transaction for this step. A table
+	 * that does not fit is resumed in the next step at the last primary key written. If the whole
+	 * dump fits in one step it is fully consistent; otherwise each step is consistent on its own
+	 * ('consistent' => false in the manifest).
+	 */
+	public function dumpStep(Repository $repo, array $state, float $deadline, array &$stats): array {
+		$state['steps']++;
+		$sm = $this->db->createSchemaManager();
+		// A pack that fills up during the dump is uploaded right away; its index cache row must
+		// wait until the read-only transaction is over.
+		$repo->holdIndexCache();
 		try {
-			if ($this->db->getDatabasePlatform() instanceof \Doctrine\DBAL\Platforms\PostgreSQLPlatform) {
-				$this->db->executeStatement('SET TRANSACTION READ ONLY');
-			}
-			$result = [];
-			foreach ($tables as $table) {
-				$writer = $repo->blobWriter($stats);
-				$hash = hash_init('sha256');
-				$rows = 0;
-				foreach ($this->tableLines($sm->introspectTable($table)) as $kind => $line) {
-					$writer->write($line . "\n");
-					if ($kind === 'row') {
+			$this->db->setTransactionIsolation(TransactionIsolationLevel::REPEATABLE_READ);
+			$this->db->beginTransaction();
+			try {
+				if ($this->db->getDatabasePlatform() instanceof \Doctrine\DBAL\Platforms\PostgreSQLPlatform) {
+					$this->db->executeStatement('SET TRANSACTION READ ONLY');
+				}
+				while ($state['i'] < count($state['tables'])) {
+					$table = $state['tables'][$state['i']];
+					$schema = $sm->introspectTable($table);
+					$writer = $repo->blobWriter($stats);
+					$hash = $state['hash'] !== null ? unserialize(base64_decode($state['hash']), ['allowed_classes' => [\HashContext::class]]) : hash_init('sha256');
+					if ($state['after'] === null && $state['segments'] === []) {
+						$writer->write($this->header($schema) . "\n");
+					}
+					$complete = true;
+					foreach ($this->rowLines($schema, $state['after']) as [$key, $line]) {
+						$writer->write($line . "\n");
 						hash_update($hash, $line . "\n");
-						$rows++;
+						$state['rows']++;
+						$state['after'] = $key;
+						if (microtime(true) >= $deadline) {
+							$complete = false;
+							break;
+						}
+					}
+					$state['segments'][] = $writer->finish();
+					$state['bytes'] += $writer->bytes();
+					if (!$complete) {
+						$state['hash'] = base64_encode(serialize($hash));
+						break;
+					}
+					$state['result'][$table] = ['blobs' => array_merge(...$state['segments']), 'rows' => $state['rows'],
+						'bytes' => $state['bytes'], 'sha256' => hash_final($hash)];
+					$state = array_merge($state, ['i' => $state['i'] + 1, 'after' => null, 'segments' => [], 'rows' => 0, 'bytes' => 0, 'hash' => null]);
+					if (microtime(true) >= $deadline && $state['i'] < count($state['tables'])) {
+						break;
 					}
 				}
-				$result[$table] = ['blobs' => $writer->finish(), 'rows' => $rows, 'bytes' => $writer->bytes(), 'sha256' => hash_final($hash)];
+				if ($state['i'] >= count($state['tables'])) {
+					$state['sequences'] = $this->sequenceStates($state['tables']);
+					$state['done'] = true;
+				}
+			} finally {
+				$this->db->rollBack();
 			}
-			$sequences = $this->sequenceStates($tables);
 		} finally {
-			$this->db->rollBack();
+			$repo->releaseIndexCache();
 		}
 		$repo->flushPacks();
-		return ['tables' => $result, 'sequences' => $sequences, 'provider' => get_class($this->db->getDatabasePlatform())];
+		return $state;
+	}
+
+	public function manifest(array $state): array {
+		return ['tables' => $state['result'], 'sequences' => $state['sequences'],
+			'provider' => get_class($this->db->getDatabasePlatform()), 'consistent' => $state['steps'] === 1];
 	}
 
 	/**
@@ -82,16 +139,23 @@ final class DbDumper {
 	 *
 	 * @param array{tables: array<string, array{blobs: list<string>, rows: int}>} $manifest
 	 */
-	public function restore(Repository $repo, array $manifest): int {
+	public function restore(Repository $repo, array $manifest, ?array &$report = null, ?callable $heartbeat = null): int {
 		$sm = $this->db->createSchemaManager();
 		$existing = array_flip($sm->listTableNames());
 		$total = 0;
+		$report = ['skipped' => [], 'restored' => []];
 		$this->db->beginTransaction();
 		try {
 			foreach ($manifest['tables'] as $table => $info) {
 				if (!isset($existing[$table])) {
 					throw new \RuntimeException("Table $table from the backup does not exist here (different app versions?)");
 				}
+				// Unchanged since the backup: leave it alone (much faster than delete + insert).
+				$live = $this->checksum($table);
+				if ($live['rows'] === $info['rows'] && hash_equals($info['sha256'], $live['sha256'])) {
+					$report['skipped'][] = $table;
+					continue;
+				}
 				$this->db->executeStatement('DELETE FROM ' . $this->db->quoteIdentifier($table));
 				$columns = null;
 				$binary = [];
@@ -112,17 +176,21 @@ final class DbDumper {
 						if (is_array($value) && isset($value['$b'])) {
 							$value = base64_decode($value['$b'], true); // text that was not valid UTF-8
 						}
-						$row[$col] = ($value !== null && isset($binary[$col])) ? base64_decode($value, true) : $value;
+						$row[] = ($value !== null && isset($binary[$col])) ? base64_decode($value, true) : $value;
 					}
 					$batch[] = $row;
-					if (count($batch) >= 500) {
-						$total += $this->insertBatch($table, $batch, $binary);
+					if (count($batch) >= self::INSERT_ROWS) {
+						$total += $this->insertBatch($table, $columns, $batch, $binary);
 						$batch = [];
+						if ($heartbeat !== null) {
+							$heartbeat();
+						}
 					}
 				}
 				if ($batch !== []) {
-					$total += $this->insertBatch($table, $batch, $binary);
+					$total += $this->insertBatch($table, $columns, $batch, $binary);
 				}
+				$report['restored'][] = $table;
 			}
 			$this->restoreSequences($manifest['sequences'] ?? []);
 			$this->db->commit();
@@ -135,20 +203,22 @@ final class DbDumper {
 
 	/** Same checksum as dump(): sha256 over the row lines in primary-key order. */
 	public function checksum(string $table): array {
-		$sm = $this->db->createSchemaManager();
 		$hash = hash_init('sha256');
 		$rows = 0;
-		foreach ($this->tableLines($sm->introspectTable($table)) as $kind => $line) {
-			if ($kind === 'row') {
-				hash_update($hash, $line . "\n");
-				$rows++;
-			}
+		foreach ($this->rowLines($this->db->createSchemaManager()->introspectTable($table)) as [, $line]) {
+			hash_update($hash, $line . "\n");
+			$rows++;
 		}
 		return ['rows' => $rows, 'sha256' => hash_final($hash)];
 	}
 
-	/** @return \Generator<string, string> 'header' => line, then 'row' => line ... */
-	private function tableLines(\Doctrine\DBAL\Schema\Table $table): \Generator {
+	private function header(\Doctrine\DBAL\Schema\Table $table): string {
+		[$columns, $binary, $pk] = $this->describe($table);
+		return json_encode(['table' => $table->getName(), 'columns' => $columns, 'binary' => $binary, 'pk' => $pk], JSON_THROW_ON_ERROR);
+	}
+
+	/** @return array{0: list<string>, 1: list<string>, 2: list<string>} columns, binary columns, primary key */
+	private function describe(\Doctrine\DBAL\Schema\Table $table): array {
 		$columns = array_values(array_map(fn ($c) => $c->getName(), $table->getColumns()));
 		$binary = [];
 		foreach ($table->getColumns() as $c) {
@@ -156,25 +226,34 @@ final class DbDumper {
 				$binary[] = $c->getName();
 			}
 		}
-		$pk = $table->getPrimaryKey()?->getColumns() ?? [];
-		yield 'header' => json_encode(['table' => $table->getName(), 'columns' => array_values($columns), 'binary' => $binary, 'pk' => $pk], JSON_THROW_ON_ERROR);
+		return [$columns, $binary, $table->getPrimaryKey()?->getColumns() ?? []];
+	}
 
+	/**
+	 * Rows in primary-key order, after the key $after (resume), as [key, JSON line].
+	 *
+	 * @return \Generator<array{0: list<mixed>|null, 1: string}>
+	 */
+	private function rowLines(\Doctrine\DBAL\Schema\Table $table, ?array $after = null): \Generator {
+		[$columns, $binary, $pk] = $this->describe($table);
 		$binaryFlip = array_flip($binary);
 		$q = fn (string $c) => $this->db->quoteIdentifier($c);
 		$select = 'SELECT ' . implode(', ', array_map($q, $columns)) . ' FROM ' . $q($table->getName());
-
 		if ($pk === []) {
-			// Nextcloud requires primary keys; small odd tables are read in one query.
+			// Nextcloud requires primary keys; small odd tables are read in one query (not resumable).
 			$count = (int)$this->db->fetchOne('SELECT COUNT(*) FROM ' . $q($table->getName()));
 			if ($count > self::MAX_ROWS_WITHOUT_PK) {
 				throw new \RuntimeException("Table {$table->getName()} has no primary key and $count rows; cannot dump it with bounded memory");
 			}
 			$batches = [$this->db->fetchAllNumeric($select)];
+			$pkIdx = [];
 		} else {
-			$batches = $this->keysetBatches($select, $pk, $columns);
+			$batches = $this->keysetBatches($select, $pk, $columns, $after);
+			$pkIdx = array_map(fn ($c) => array_search($c, $columns, true), $pk);
 		}
 		foreach ($batches as $rows) {
 			foreach ($rows as $row) {
+				$key = $pkIdx === [] ? null : array_map(fn ($i) => $row[$i], $pkIdx);
 				foreach ($columns as $i => $col) {
 					if (is_resource($row[$i])) {
 						$row[$i] = stream_get_contents($row[$i]);
@@ -184,28 +263,32 @@ final class DbDumper {
 					} elseif (is_string($row[$i]) && !mb_check_encoding($row[$i], 'UTF-8')) {
 						// Keep invalid UTF-8 byte-exact instead of substituting characters.
 						$row[$i] = ['$b' => base64_encode($row[$i])];
-					} elseif (is_int($row[$i]) || is_float($row[$i]) || is_bool($row[$i])) {
+					} elseif (is_float($row[$i])) {
+						// var_export uses serialize_precision (shortest exact form), not the lossy
+						// 14-digit 'precision' of a (string) cast.
+						$row[$i] = var_export($row[$i], true);
+					} elseif (is_int($row[$i]) || is_bool($row[$i])) {
 						// Normalise: drivers differ in returning numbers as int or string.
 						$row[$i] = (string)(is_bool($row[$i]) ? (int)$row[$i] : $row[$i]);
 					}
 				}
-				yield 'row' => json_encode($row, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_THROW_ON_ERROR);
+				yield [$key, json_encode($row, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_THROW_ON_ERROR)];
 			}
 		}
 	}
 
 	/** @return \Generator<list<list<mixed>>> */
-	private function keysetBatches(string $select, array $pk, array $columns): \Generator {
+	private function keysetBatches(string $select, array $pk, array $columns, ?array $after): \Generator {
 		$q = fn (string $c) => $this->db->quoteIdentifier($c);
 		$order = ' ORDER BY ' . implode(', ', array_map($q, $pk));
-		$pkIdx = array_map(fn ($c) => array_search($c, $columns, true), $pk);
-		$last = null;
+		$cols = array_map(fn ($c) => $q($c), $pk);
+		$last = $after;
 		while (true) {
 			$sql = $select;
 			$params = [];
 			if ($last !== null) {
 				// Row-value comparison (a, b) > (?, ?), supported by PostgreSQL, MySQL/MariaDB and SQLite.
-				$sql .= ' WHERE (' . implode(', ', array_map($q, $pk)) . ') > (' . implode(', ', array_fill(0, count($pk), '?')) . ')';
+				$sql .= ' WHERE (' . implode(', ', $cols) . ') > (' . implode(', ', array_fill(0, count($pk), '?')) . ')';
 				$params = $last;
 			}
 			$rows = $this->db->fetchAllNumeric($sql . $order . ' LIMIT ' . self::BATCH, $params);
@@ -213,22 +296,29 @@ final class DbDumper {
 				return;
 			}
 			yield $rows;
-			$end = end($rows);
-			$last = array_map(fn ($i) => $end[$i], $pkIdx);
 			if (count($rows) < self::BATCH) {
 				return;
 			}
+			$end = end($rows);
+			$last = array_map(fn ($c) => $end[array_search($c, $columns, true)], $pk);
 		}
 	}
 
-	private function insertBatch(string $table, array $rows, array $binary): int {
+	/** One INSERT with several rows (portable multi-row VALUES). */
+	private function insertBatch(string $table, array $columns, array $rows, array $binary): int {
+		$q = fn (string $c) => $this->db->quoteIdentifier($c);
+		$placeholders = '(' . implode(', ', array_fill(0, count($columns), '?')) . ')';
+		$sql = 'INSERT INTO ' . $q($table) . ' (' . implode(', ', array_map($q, $columns)) . ') VALUES '
+			. implode(', ', array_fill(0, count($rows), $placeholders));
+		$params = [];
+		$types = [];
 		foreach ($rows as $row) {
-			$types = [];
-			foreach ($row as $col => $_) {
-				$types[$col] = isset($binary[$col]) ? \Doctrine\DBAL\ParameterType::LARGE_OBJECT : \Doctrine\DBAL\ParameterType::STRING;
+			foreach ($columns as $i => $col) {
+				$params[] = $row[$i];
+				$types[] = isset($binary[$col]) ? \Doctrine\DBAL\ParameterType::LARGE_OBJECT : ($row[$i] === null ? \Doctrine\DBAL\ParameterType::NULL : \Doctrine\DBAL\ParameterType::STRING);
 			}
-			$this->db->insert($this->db->quoteIdentifier($table), array_combine(array_map(fn ($c) => $this->db->quoteIdentifier($c), array_keys($row)), $row), array_values($types));
 		}
+		$this->db->executeStatement($sql, $params, $types);
 		return count($rows);
 	}
 

lib/Db/DbIndexCache.php

@@ -11,7 +11,7 @@ use OCA\NgBackup\Repository\IIndexCache;
 use OCP\DB\Exception;
 use OCP\IDBConnection;
 
-class DbIndexCache implements IIndexCache {
+final class DbIndexCache implements IIndexCache {
 	public function __construct(
 		private IDBConnection $db,
 	) {

lib/Db/Run.php

@@ -33,7 +33,7 @@ use OCP\AppFramework\Db\Entity;
  * @method int|null getFinishedAt()
  * @method void setFinishedAt(?int $v)
  */
-class Run extends Entity {
+final class Run extends Entity {
 	public const RUNNING = 'running';
 	public const DONE = 'done';
 	public const FAILED = 'failed';

lib/Db/RunMapper.php

@@ -12,7 +12,7 @@ use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\IDBConnection;
 
 /** @template-extends QBMapper<Run> */
-class RunMapper extends QBMapper {
+final class RunMapper extends QBMapper {
 	public function __construct(IDBConnection $db) {
 		parent::__construct($db, 'ngb_runs', Run::class);
 	}
@@ -43,6 +43,17 @@ class RunMapper extends QBMapper {
 		return $this->findEntities($qb);
 	}
 
+	/** @return list<Run> runs of $kind started at or after $since, newest first */
+	public function startedSince(int $targetId, string $kind, int $since): array {
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('*')->from($this->getTableName())
+			->where($qb->expr()->eq('target_id', $qb->createNamedParameter($targetId, IQueryBuilder::PARAM_INT)))
+			->andWhere($qb->expr()->eq('kind', $qb->createNamedParameter($kind)))
+			->andWhere($qb->expr()->gte('started_at', $qb->createNamedParameter($since, IQueryBuilder::PARAM_INT)))
+			->orderBy('id', 'DESC');
+		return $this->findEntities($qb);
+	}
+
 	public function lastFinished(int $targetId, string $kind): ?Run {
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('*')->from($this->getTableName())

lib/Db/Snapshot.php

@@ -25,7 +25,7 @@ use OCP\AppFramework\Db\Entity;
  * @method int|null getBytes()
  * @method void setBytes(?int $v)
  */
-class Snapshot extends Entity {
+final class Snapshot extends Entity {
 	protected int $targetId = 0;
 	protected string $snapshotId = '';
 	protected string $kind = '';

lib/Db/SnapshotMapper.php

@@ -12,7 +12,7 @@ use OCP\DB\QueryBuilder\IQueryBuilder;
 use OCP\IDBConnection;
 
 /** @template-extends QBMapper<Snapshot> */
-class SnapshotMapper extends QBMapper {
+final class SnapshotMapper extends QBMapper {
 	public function __construct(IDBConnection $db) {
 		parent::__construct($db, 'ngb_snapshots', Snapshot::class);
 	}

lib/Db/Target.php

@@ -22,10 +22,14 @@ use OCP\AppFramework\Db\Entity;
  * @method void setBasePath(string $v)
  * @method string|null getRepositoryId()
  * @method void setRepositoryId(?string $v)
+ * @method bool|null getAppendOnly()
+ * @method void setAppendOnly(bool $v)
+ * @method int|null getMaxBytes()
+ * @method void setMaxBytes(?int $v)
  * @method int getCreatedAt()
  * @method void setCreatedAt(int $v)
  */
-class Target extends Entity {
+final class Target extends Entity {
 	protected string $name = '';
 	protected string $backend = '';
 	protected string $auth = '';
@@ -33,8 +37,12 @@ class Target extends Entity {
 	protected string $basePath = '';
 	protected ?string $repositoryId = null;
 	protected int $createdAt = 0;
+	protected ?bool $appendOnly = null;
+	protected ?int $maxBytes = null;
 
 	public function __construct() {
 		$this->addType('createdAt', 'integer');
+		$this->addType('appendOnly', 'boolean');
+		$this->addType('maxBytes', 'integer');
 	}
 }

lib/Db/TargetMapper.php

@@ -11,7 +11,7 @@ use OCP\AppFramework\Db\QBMapper;
 use OCP\IDBConnection;
 
 /** @template-extends QBMapper<Target> */
-class TargetMapper extends QBMapper {
+final class TargetMapper extends QBMapper {
 	public function __construct(IDBConnection $db) {
 		parent::__construct($db, 'ngb_targets', Target::class);
 	}

lib/Job/BackupRun.php

@@ -49,9 +49,11 @@ final class BackupRun {
 	public static function step(Repository $repo, array $state, float $deadline): array {
 		$state['steps']++;
 		if ($state['phase'] === 'files') {
-			$walker = new TreeWalker($state['roots'], $state['exclude']);
-			$parent = new ParentCursor($repo, $state['parent'], $state['parentPos']);
 			$stats = $state['stats'];
+			$walker = new TreeWalker($state['roots'], $state['exclude'], function (string $logical) use (&$state, &$stats): void {
+				self::recordUnreadable($state, $stats, $logical);
+			});
+			$parent = new ParentCursor($repo, $state['parent'], $state['parentPos']);
 			$lines = [];
 			$finishedWalk = true;
 
@@ -68,15 +70,20 @@ final class BackupRun {
 					$stats['reused']++;
 				} else {
 					$cur = $state['cur'];
-					if ($cur === null || $cur['path'] !== $logical || $cur['version'] !== $version) {
-						if ($cur !== null && $cur['path'] === $logical) {
-							$stats['retried'] = ($stats['retried'] ?? 0) + 1; // changed since the previous step
+					if ($cur !== null && $cur['path'] === $logical && $cur['version'] !== $version) {
+						// Changed since the previous step: start over, unless it keeps changing.
+						if (self::countRetry($state, $stats, $logical)) {
+							$cur['version'] = $version;
+						} else {
+							$cur = null;
 						}
+					}
+					if ($cur === null || $cur['path'] !== $logical) {
 						$cur = ['path' => $logical, 'offset' => 0, 'blobs' => [], 'version' => $version];
 					}
-					$fh = fopen($path, 'rb');
+					$fh = @fopen($path, 'rb');
 					if ($fh === false) {
-						$stats['unreadable'] = ($stats['unreadable'] ?? 0) + 1;
+						self::recordUnreadable($state, $stats, $logical);
 						$state['cur'] = null;
 						continue;
 					}
@@ -91,12 +98,17 @@ final class BackupRun {
 						}
 					}
 					fclose($fh);
-					if (Repository::fileVersion($path) !== $cur['version']) {
-						// Changed while reading: read it again from the start (now or next step).
-						$stats['retried'] = ($stats['retried'] ?? 0) + 1;
-						$state['cur'] = null;
-						$finishedWalk = false;
-						break;
+					$now = Repository::fileVersion($path);
+					if ($now !== $cur['version']) {
+						if (!self::countRetry($state, $stats, $logical)) {
+							// Changed while reading: read it again from the start (now or next step).
+							$state['cur'] = null;
+							$finishedWalk = false;
+							break;
+						}
+						// Keeps changing (a live database, VM image or log): keep what was read,
+						// like any copy of a file in use, and report it instead of retrying forever.
+						$cur['version'] = $now;
 					}
 					if (!$complete) {
 						$state['cur'] = $cur;
@@ -104,6 +116,7 @@ final class BackupRun {
 						break;
 					}
 					$blobs = $cur['blobs'];
+					$size = $cur['offset'];
 					$state['cur'] = null;
 					$stats['read']++;
 				}
@@ -133,19 +146,66 @@ final class BackupRun {
 
 		if ($state['phase'] === 'finish') {
 			$segments = $state['segments'];
-			$repo->writeSnapshot($state['snapshot'],
+			$repo->putSnapshot($state['snapshot'],
 				['time' => $state['started'], 'parent' => $state['parent'], 'label' => $state['label'],
-					'roots' => array_keys($state['roots']), 'stats' => $state['stats']] + $state['meta'],
+					'roots' => array_keys($state['roots']), 'stats' => $state['stats'],
+					'warnings' => self::warnings($state)] + $state['meta'],
 				(function () use ($repo, $segments) {
 					foreach ($segments as $blobs) {
 						yield from $repo->readLines($blobs);
 					}
 				})());
-			$state['phase'] = 'done';
+			$state['phase'] = 'commit';
 		}
 		return $state;
 	}
 
+	/**
+	 * A file or directory that could not be read: it is missing from this snapshot. Remembered (first
+	 * 1000, deduplicated across steps) so the run can report it instead of silently succeeding.
+	 */
+	private static function recordUnreadable(array &$state, array &$stats, string $logical): void {
+		if (isset($state['unreadable'][$logical])) {
+			return;
+		}
+		if (count($state['unreadable'] ?? []) < 1000) {
+			$state['unreadable'][$logical] = true;
+		}
+		$stats['unreadable'] = ($stats['unreadable'] ?? 0) + 1;
+	}
+
+	/** @return array{unreadable: list<string>, changing: list<string>} examples for the report (first 50 each) */
+	public static function warnings(array $state): array {
+		return [
+			'unreadable' => array_slice(array_map('strval', array_keys($state['unreadable'] ?? [])), 0, 50),
+			'changing' => array_slice(array_map('strval', array_values($state['changing'] ?? [])), 0, 50),
+		];
+	}
+
+	/** Retries of one file that changes while it is read, before its last read is kept anyway. */
+	public const MAX_RETRIES = 3;
+
+	/**
+	 * Count a retry of $logical. Returns true once it has changed MAX_RETRIES times: the caller then
+	 * keeps the data it read, and the file is listed in $state['changing'] (first 50) for the report.
+	 */
+	private static function countRetry(array &$state, array &$stats, string $logical): bool {
+		$stats['retried'] = ($stats['retried'] ?? 0) + 1;
+		$n = (($state['retryPath'] ?? null) === $logical ? (int)($state['retryCount'] ?? 0) : 0) + 1;
+		$state['retryPath'] = $logical;
+		$state['retryCount'] = $n;
+		if ($n < self::MAX_RETRIES) {
+			return false;
+		}
+		if ($n === self::MAX_RETRIES) {
+			$stats['changing'] = ($stats['changing'] ?? 0) + 1;
+			if (count($state['changing'] ?? []) < 50) {
+				$state['changing'][] = $logical;
+			}
+		}
+		return true;
+	}
+
 	private static function readFull($fh, int $length): string {
 		$buffer = '';
 		while (strlen($buffer) < $length && !feof($fh)) {

lib/Job/TreeWalker.php

@@ -23,6 +23,8 @@ final class TreeWalker {
 	public function __construct(
 		private array $roots,
 		private array $exclude = [],
+		/** Called with the logical path of a directory that cannot be listed. */
+		private ?\Closure $onUnreadable = null,
 	) {
 	}
 
@@ -57,6 +59,9 @@ final class TreeWalker {
 		}
 		$names = @scandir($abs);
 		if ($names === false) {
+			if ($this->onUnreadable !== null) {
+				($this->onUnreadable)($logical === '' ? '/' : $logical);
+			}
 			return;
 		}
 		$names = array_values(array_diff($names, ['.', '..']));

lib/Migration/Version000001Date20261002000000.php

@@ -13,7 +13,7 @@ use OCP\DB\Types;
 use OCP\Migration\IOutput;
 use OCP\Migration\SimpleMigrationStep;
 
-class Version000001Date20261002000000 extends SimpleMigrationStep {
+final class Version000001Date20261002000000 extends SimpleMigrationStep {
 	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
 		/** @var ISchemaWrapper $schema */
 		$schema = $schemaClosure();

lib/Migration/Version000002Date20261002010000.php

@@ -14,7 +14,7 @@ use OCP\Migration\IOutput;
 use OCP\Migration\SimpleMigrationStep;
 
 /** Local cache of the per-pack index files, so opening a repository does not download them all. */
-class Version000002Date20261002010000 extends SimpleMigrationStep {
+final class Version000002Date20261002010000 extends SimpleMigrationStep {
 	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
 		/** @var ISchemaWrapper $schema */
 		$schema = $schemaClosure();

lib/Migration/Version000003Date20261002020000.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\DB\Types;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+/** Append-only locations: NG Backup never deletes anything there (cleanup by the location's own lifecycle rules). */
+final class Version000003Date20261002020000 extends SimpleMigrationStep {
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+		$t = $schema->getTable('ngb_targets');
+		if (!$t->hasColumn('append_only')) {
+			$t->addColumn('append_only', Types::BOOLEAN, ['notnull' => false, 'default' => false]);
+			return $schema;
+		}
+		return null;
+	}
+}

lib/Migration/Version000004Date20261002030000.php

@@ -0,0 +1,28 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\DB\Types;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+/** Optional size limit per location (cost control; S3 has no bucket quota). */
+final class Version000004Date20261002030000 extends SimpleMigrationStep {
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+		$t = $schema->getTable('ngb_targets');
+		if (!$t->hasColumn('max_bytes')) {
+			$t->addColumn('max_bytes', Types::BIGINT, ['notnull' => false, 'unsigned' => true]);
+			return $schema;
+		}
+		return null;
+	}
+}

lib/Migration/Version000005Date20261002040000.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Migration;
+
+use Closure;
+use OCP\DB\ISchemaWrapper;
+use OCP\DB\Types;
+use OCP\Migration\IOutput;
+use OCP\Migration\SimpleMigrationStep;
+
+/** Leases with an expiry: a killed process cannot block a location for longer than its lease. */
+final class Version000005Date20261002040000 extends SimpleMigrationStep {
+	public function changeSchema(IOutput $output, Closure $schemaClosure, array $options): ?ISchemaWrapper {
+		/** @var ISchemaWrapper $schema */
+		$schema = $schemaClosure();
+		if ($schema->hasTable('ngb_leases')) {
+			return null;
+		}
+		$t = $schema->createTable('ngb_leases');
+		$t->addColumn('id', Types::STRING, ['notnull' => true, 'length' => 32]);
+		$t->addColumn('name', Types::STRING, ['notnull' => true, 'length' => 128]);
+		$t->addColumn('mode', Types::STRING, ['notnull' => true, 'length' => 1]);
+		$t->addColumn('expires_at', Types::BIGINT, ['notnull' => true, 'unsigned' => true]);
+		$t->setPrimaryKey(['id']);
+		$t->addIndex(['name'], 'ngb_leases_name');
+		return $schema;
+	}
+}

lib/Notification/Notifier.php

@@ -0,0 +1,83 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Notification;
+
+use OCA\NgBackup\AppInfo\Application;
+use OCP\IURLGenerator;
+use OCP\L10N\IFactory;
+use OCP\Notification\INotification;
+use OCP\Notification\INotifier;
+use OCP\Notification\UnknownNotificationException;
+
+final class Notifier implements INotifier {
+	public function __construct(
+		private IFactory $l10n,
+		private IURLGenerator $url,
+	) {
+	}
+
+	public function getID(): string {
+		return Application::APP_ID;
+	}
+
+	public function getName(): string {
+		return $this->l10n->get(Application::APP_ID)->t('NG Backup');
+	}
+
+	public function prepare(INotification $notification, string $languageCode): INotification {
+		if ($notification->getApp() !== Application::APP_ID) {
+			throw new UnknownNotificationException();
+		}
+		$l = $this->l10n->get(Application::APP_ID, $languageCode);
+		$p = $notification->getSubjectParameters();
+		switch ($notification->getSubject()) {
+			case 'run_failed':
+				$notification->setParsedSubject($p['kind'] === 'restore'
+					? $l->t('Restore from %s failed', [$p['target']])
+					: $l->t('Backup to %s failed', [$p['target']]));
+				$notification->setParsedMessage((string)($p['error'] ?? ''));
+				break;
+			case 'run_warnings':
+				$notification->setParsedSubject($l->t('Backup to %1$s finished with warnings: %2$s unreadable, %3$s changed while being read', [$p['target'], $p['unreadable'], $p['changing']]));
+				$notification->setParsedMessage($l->t('Unreadable files and folders are missing from this backup (check their permissions). Files that kept changing were saved as they were while being read. Examples: %s', [$p['examples'] ?? '']));
+				break;
+			case 'quota_warning':
+				$notification->setParsedSubject($l->t('Backup location %1$s is at %2$s%% of its limit (%3$s of %4$s)', [$p['target'], $p['percent'], $p['used'], $p['limit']]));
+				$notification->setParsedMessage($l->t('Backups stop when the limit is reached. Raise the limit, or let the retention policy remove older backups.'));
+				break;
+			case 'backup_stale':
+				$notification->setParsedSubject($l->t('No successful backup to %1$s since %2$s', [$p['target'], $p['since']]));
+				$notification->setParsedMessage($l->t('Check the backup settings and the server log.'));
+				break;
+			case 'security_event':
+				$who = (string)($p['actor'] ?? '');
+				$notification->setParsedSubject(match ($p['event'] ?? '') {
+					'kit_downloaded' => $l->t('%s downloaded the backup recovery kit', [$who]),
+					'target_removed' => $l->t('%1$s removed backup location %2$s', [$who, $p['target'] ?? '']),
+					'append_only_off' => $l->t('%1$s turned off append-only for backup location %2$s', [$who, $p['target'] ?? '']),
+					'retention_changed' => $l->t('%1$s changed the backup retention to %2$s', [$who, $p['policy'] ?? '']),
+					'snapshots_forgotten' => $l->t('%1$s moved %2$s snapshots of %3$s to the trash; they are deleted permanently after %4$s unless restored', [$who, $p['count'] ?? '', $p['target'] ?? '', $p['until'] ?? '']),
+					'snapshot_untrashed' => $l->t('%1$s restored snapshot %2$s of %3$s from the trash', [$who, $p['snapshot'] ?? '', $p['target'] ?? '']),
+					'catalog_trusted' => $l->t('%1$s accepted an older state of backup location %2$s (catalog generation %3$s)', [$who, $p['target'] ?? '', $p['generation'] ?? '']),
+					'slot_added' => $l->t('%1$s added backup passphrase slot %2$s (%3$s); download and confirm the new recovery kit', [$who, $p['slot'] ?? '', $p['label'] ?? '']),
+					'slot_replaced' => $l->t('%1$s set a new passphrase for backup key slot %2$s (%3$s); download and confirm the new recovery kit', [$who, $p['slot'] ?? '', $p['label'] ?? '']),
+					'user_export_retention_changed' => $l->t('%1$s changed how many exports per user are kept to %2$s', [$who, $p['keep'] ?? '']),
+					'user_exports_forgotten' => $l->t('%1$s removed %2$s per-user exports from %3$s', [$who, $p['count'] ?? '', $p['target'] ?? '']),
+					'slot_removed' => $l->t('%1$s removed backup passphrase slot %2$s; download and confirm the new recovery kit', [$who, $p['slot'] ?? '']),
+					default => $l->t('NG Backup security event'),
+				});
+				$notification->setParsedMessage($l->t('If this was not you or another administrator, check who has admin access.'));
+				break;
+			default:
+				throw new UnknownNotificationException();
+		}
+		$notification->setLink($this->url->linkToRouteAbsolute('settings.AdminSettings.index', ['section' => 'ng_backup']));
+		$notification->setIcon($this->url->getAbsoluteURL($this->url->imagePath(Application::APP_ID, 'app-dark.svg')));
+		return $notification;
+	}
+}

lib/Repository/BlobIndex.php

@@ -25,6 +25,8 @@ final class BlobIndex {
 	private array $pending = [];
 
 	private ?IIndexCache $cache = null;
+	/** @var list<\Closure():void>|null cache writes held back by holdCache(), or null when writing directly */
+	private ?array $heldCacheWrites = null;
 	private string $repositoryId = '';
 	/** @var int index files downloaded by the last load() (for tests and diagnostics) */
 	public int $downloaded = 0;
@@ -40,16 +42,57 @@ final class BlobIndex {
 		$this->repositoryId = $repositoryId;
 	}
 
+	/**
+	 * Hold back cache writes until releaseCache(). The database dump reads inside a read-only
+	 * transaction on the same connection that the cache writes to: a write there fails on
+	 * PostgreSQL and would be rolled back with the dump transaction elsewhere.
+	 */
+	public function holdCache(): void {
+		$this->heldCacheWrites ??= [];
+	}
+
+	/** Write the cache changes held back since holdCache(). */
+	public function releaseCache(): void {
+		$writes = $this->heldCacheWrites ?? [];
+		$this->heldCacheWrites = null;
+		foreach ($writes as $write) {
+			$write();
+		}
+	}
+
+	/** @param list<array{id:string, offset:int, length:int, raw:int, flags:int}> $entries */
+	private function cachePut(string $packId, array $entries): void {
+		if ($this->heldCacheWrites !== null) {
+			$this->heldCacheWrites[] = function () use ($packId, $entries): void {
+				$this->cache?->put($this->repositoryId, $packId, $entries);
+			};
+			return;
+		}
+		$this->cache?->put($this->repositoryId, $packId, $entries);
+	}
+
+	/** @param list<string> $packIds */
+	private function cacheRemove(array $packIds): void {
+		if ($this->heldCacheWrites !== null) {
+			$this->heldCacheWrites[] = function () use ($packIds): void {
+				$this->cache?->remove($this->repositoryId, $packIds);
+			};
+			return;
+		}
+		$this->cache?->remove($this->repositoryId, $packIds);
+	}
+
 	/**
 	 * Load the index: one listing of index/, entries from the local cache where available,
 	 * and only the index files that are not cached yet are downloaded. Cached packs that no
 	 * longer exist on the backend are dropped from the cache.
 	 */
-	public function load(): void {
-		$cached = $this->cache?->all($this->repositoryId) ?? [];
+	public function load(bool $verify = false): void {
+		$this->blobs = [];
+		$cached = $verify ? [] : ($this->cache?->all($this->repositoryId) ?? []);
 		$present = [];
 		$this->downloaded = 0;
-		foreach ($this->backend->list('index') as $path) {
+		foreach ($this->backend->listFiles('index') as $path) {
 			$packId = basename($path);
 			$present[$packId] = true;
 			if (isset($cached[$packId])) {
@@ -65,6 +108,20 @@ final class BlobIndex {
 				$this->blobs[$e['id']] = [$packId, $e['offset'], $e['length'], $e['raw'], $e['flags']];
 			}
 		}
+		if ($verify && $this->cache !== null) {
+			// Refresh the cache from what was just verified.
+			$this->cache->remove($this->repositoryId, array_keys($this->cache->all($this->repositoryId)));
+			foreach ($this->packs() as $packId => $_) {
+				$entries = [];
+				foreach ($this->blobs as $id => [$pack, $offset, $length, $raw, $flags]) {
+					if ($pack === $packId) {
+						$entries[] = ['id' => $id, 'offset' => $offset, 'length' => $length, 'raw' => $raw, 'flags' => $flags];
+					}
+				}
+				$this->cache->put($this->repositoryId, $packId, $entries);
+			}
+			return;
+		}
 		$stale = array_keys(array_diff_key($cached, $present));
 		if ($stale !== []) {
 			$this->cache?->remove($this->repositoryId, $stale);
@@ -97,13 +154,42 @@ final class BlobIndex {
 		fwrite($stream, $this->cipher->encryptString(json_encode($entries, JSON_THROW_ON_ERROR), 'index:' . $packId));
 		rewind($stream);
 		$this->backend->put('index/' . $packId, $stream);
-		$this->cache?->put($this->repositoryId, $packId, $entries);
+		$this->cachePut($packId, $entries);
 		foreach ($entries as $e) {
 			$this->blobs[$e['id']] = [$packId, $e['offset'], $e['length'], $e['raw'], $e['flags']];
 			unset($this->pending[$e['id']]);
 		}
 	}
 
+	/** @return array<string, list<array{id:string, offset:int, length:int}>> packId => blobs currently located in that pack */
+	public function packs(): array {
+		$packs = [];
+		foreach ($this->blobs as $id => [$pack, $offset, $length]) {
+			$packs[$pack][] = ['id' => $id, 'offset' => $offset, 'length' => $length];
+		}
+		return $packs;
+	}
+
+	/** Forget a pack: delete its index file and cache row. Blobs that now live elsewhere are kept. */
+	public function removePack(string $packId): void {
+		$this->backend->delete('index/' . $packId);
+		$this->cacheRemove([$packId]);
+		foreach ($this->blobs as $id => $loc) {
+			if ($loc[0] === $packId) {
+				unset($this->blobs[$id]);
+			}
+		}
+	}
+
+	/** Bytes of all blobs in the index (encrypted size, i.e. what is stored in packs). */
+	public function storedBytes(): int {
+		$total = 0;
+		foreach ($this->blobs as [, , $length]) {
+			$total += $length;
+		}
+		return $total;
+	}
+
 	public function count(): int {
 		return count($this->blobs);
 	}

lib/Repository/Catalog.php

@@ -0,0 +1,141 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Repository;
+
+use OCA\NgBackup\Backend\IBackend;
+use OCA\NgBackup\Crypto\StreamCipher;
+
+/**
+ * Chained catalog of a repository's state, against rollback and hidden snapshots.
+ *
+ * Every change to the set of snapshots or trash entries writes catalog/<generation>: the
+ * encrypted list of snapshot and trash ids plus the hash of the previous generation. The server
+ * keeps the newest generation it has seen (ICatalogAnchor). On open, the newest catalog on the
+ * location must be at least the anchored generation and lead back to it through the chain;
+ * snapshots listed in the catalog must exist. Otherwise the location was rolled back or
+ * tampered with, and the repository is refused.
+ */
+final class Catalog {
+	private const KEEP = 200; // generations kept on the location (enough to verify long gaps)
+
+	public int $gen = 0;
+	/** @var array<string, true> */
+	public array $snapshots = [];
+	/** @var array<string, true> */
+	public array $trash = [];
+	/** @var array<string, true> manifest path => true, for a per-user export (users/<uid>/<exportId>) */
+	public array $userExports = [];
+	public string $hash = '';
+
+	public function __construct(
+		private IBackend $backend,
+		private StreamCipher $cipher,
+		private string $repositoryId,
+		private ?ICatalogAnchor $anchor,
+	) {
+	}
+
+	/** Load and verify the newest catalog; create the first one for repositories that have none. */
+	public function load(callable $listSnapshots, callable $listTrash, callable $listUserExports): void {
+		$gens = $this->generations();
+		if ($gens === []) {
+			// First use (new or pre-catalog repository): adopt the current state as generation 1.
+			$anchored = $this->anchor?->get($this->repositoryId);
+			if ($anchored !== null) {
+				throw new RepositoryException('The catalog of this repository has disappeared from the location (possible tampering)');
+			}
+			$this->snapshots = array_fill_keys($listSnapshots(), true);
+			$this->trash = array_fill_keys($listTrash(), true);
+			$this->userExports = array_fill_keys($listUserExports(), true);
+			$this->write();
+			return;
+		}
+		$head = max($gens);
+		[$data, $hash] = $this->read($head);
+		$anchored = $this->anchor?->get($this->repositoryId);
+		if ($anchored !== null) {
+			if ($head < $anchored['gen']) {
+				throw new RepositoryException(sprintf('The location shows catalog generation %d, but this server has seen %d: the backups were rolled back', $head, $anchored['gen']));
+			}
+			// Walk back to the anchored generation, checking every link.
+			[$cur, $curHash] = [$data, $hash];
+			for ($g = $head; $g > $anchored['gen']; $g--) {
+				[$prev, $prevHash] = $this->read($g - 1);
+				if (!hash_equals($prevHash, (string)$cur['prev'])) {
+					throw new RepositoryException("Catalog chain broken at generation $g (possible tampering)");
+				}
+				[$cur, $curHash] = [$prev, $prevHash];
+			}
+			if (!hash_equals($anchored['hash'], $curHash)) {
+				throw new RepositoryException('The catalog does not match what this server saw before (possible tampering)');
+			}
+		}
+		$this->gen = $head;
+		$this->hash = $hash;
+		$this->snapshots = array_fill_keys($data['snapshots'], true);
+		$this->trash = array_fill_keys($data['trash'], true);
+		// Catalogs written before user exports existed have no such key: default to empty rather
+		// than adopting the location's current users/ listing (that would skip verification).
+		$this->userExports = array_fill_keys($data['userExports'] ?? [], true);
+		$this->anchor?->set($this->repositoryId, $this->gen, $this->hash);
+	}
+
+	/** Write the next generation after the in-memory state was changed. */
+	public function write(): void {
+		$next = $this->gen + 1;
+		// Two writers starting from the same generation would otherwise overwrite each other
+		// silently and break the chain for whichever server anchored the lost write.
+		if ($this->backend->exists($this->path($next))) {
+			throw new RepositoryException("Catalog generation $next was written by another process at the same time; try again");
+		}
+		$plain = json_encode(['repository' => $this->repositoryId, 'gen' => $next, 'time' => gmdate('c'), 'prev' => $this->hash,
+			'snapshots' => array_keys($this->snapshots), 'trash' => array_keys($this->trash),
+			'userExports' => array_keys($this->userExports)], JSON_THROW_ON_ERROR);
+		$encrypted = $this->cipher->encryptString($plain, $this->ad($next));
+		$stream = fopen('php://memory', 'w+b');
+		fwrite($stream, $encrypted);
+		rewind($stream);
+		$this->backend->put($this->path($next), $stream);
+		$this->gen = $next;
+		$this->hash = hash('sha256', $encrypted);
+		$this->anchor?->set($this->repositoryId, $this->gen, $this->hash);
+		$old = $next - self::KEEP;
+		if ($old > 0) {
+			$this->backend->delete($this->path($old));
+		}
+	}
+
+	/** @return array{0: array, 1: string} decoded catalog and the hash of its encrypted bytes */
+	private function read(int $gen): array {
+		try {
+			$fh = $this->backend->get($this->path($gen));
+		} catch (\Throwable) {
+			throw new RepositoryException("Catalog generation $gen is missing (possible tampering)");
+		}
+		$encrypted = (string)stream_get_contents($fh);
+		fclose($fh);
+		$data = json_decode($this->cipher->decryptString($encrypted, $this->ad($gen)), true, 512, JSON_THROW_ON_ERROR);
+		if (($data['repository'] ?? '') !== $this->repositoryId || ($data['gen'] ?? 0) !== $gen) {
+			throw new RepositoryException("Catalog generation $gen belongs to another repository or position");
+		}
+		return [$data, hash('sha256', $encrypted)];
+	}
+
+	/** @return list<int> */
+	private function generations(): array {
+		return array_map(fn ($p) => (int)basename($p), $this->backend->listFiles('catalog'));
+	}
+
+	private function path(int $gen): string {
+		return sprintf('catalog/%010d', $gen);
+	}
+
+	private function ad(int $gen): string {
+		return 'catalog:' . $this->repositoryId . ':' . $gen;
+	}
+}

lib/Repository/ICatalogAnchor.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Repository;
+
+/**
+ * Where the server remembers the newest catalog generation it has seen for a repository, outside
+ * the (untrusted) location. A location that presents an older generation, or a chain that does
+ * not lead back to this anchor, is rolled back or tampered with.
+ */
+interface ICatalogAnchor {
+	/** @return array{gen:int, hash:string}|null */
+	public function get(string $repositoryId): ?array;
+
+	public function set(string $repositoryId, int $gen, string $hash): void;
+}

lib/Repository/PackWriter.php

@@ -32,6 +32,7 @@ final class PackWriter {
 		private StreamCipher $cipher,
 		private BlobIndex $index,
 		private int $targetSize = 32 * 1048576,
+		private ?int $maxBytes = null,
 	) {
 		$this->reset();
 	}
@@ -49,11 +50,27 @@ final class PackWriter {
 		return strlen($encrypted);
 	}
 
+	/** Add an already encrypted blob as-is (repacking: no decryption needed, the blob is bound to its id, not to a pack). */
+	public function addRaw(string $id, string $encrypted, int $rawLength, int $flags): void {
+		fwrite($this->buffer, $encrypted);
+		$this->entries[] = ['id' => $id, 'offset' => $this->size, 'length' => strlen($encrypted), 'raw' => $rawLength, 'flags' => $flags];
+		$this->size += strlen($encrypted);
+		if ($this->size >= $this->targetSize) {
+			$this->flush();
+		}
+	}
+
 	/** Upload the current pack (if any) and record it in the index. */
 	public function flush(): void {
 		if ($this->entries === []) {
 			return;
 		}
+		if ($this->maxBytes !== null && $this->index->storedBytes() + $this->size > $this->maxBytes) {
+			$this->index->dropPending(array_column($this->entries, 'id'));
+			$this->reset();
+			throw new QuotaExceededException(sprintf('Storage limit of this location reached (%.1f GiB): backup stopped',
+				$this->maxBytes / 1073741824));
+		}
 		$packId = bin2hex(random_bytes(16));
 		$header = $this->cipher->encryptString(json_encode($this->entries, JSON_THROW_ON_ERROR), 'pack-header:' . $packId);
 		fwrite($this->buffer, $header . pack('N', strlen($header)));

lib/Repository/QuotaExceededException.php

@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Repository;
+
+final class QuotaExceededException extends RepositoryException {
+}

lib/Repository/Repository.php

@@ -28,10 +28,14 @@ final class Repository {
 	public const FORMAT = 1;
 	public const BLOB_SIZE = 4 * 1048576;
 	private const FLAG_DEFLATE = 1;
+	/** Reads per blob in a deep verify before it is reported as unreadable (not corrupted). */
+	private const VERIFY_READ_ATTEMPTS = 3;
 
 	private StreamCipher $cipher;
 	private BlobIndex $index;
 	private ?PackWriter $runPacks = null;
+	private ?int $maxBytes = null;
+	private Catalog $catalog;
 
 	private function __construct(
 		private IBackend $backend,
@@ -52,7 +56,7 @@ final class Repository {
 	 * copy (KeyRing::wrap) stored in the repository config, so the repository can be opened
 	 * with the passphrase from the recovery kit even when the server is gone.
 	 */
-	public static function initWithKey(IBackend $backend, KeyRing $keys, array $wrappedKey): self {
+	public static function initWithKey(IBackend $backend, KeyRing $keys, array $wrappedKey, ?ICatalogAnchor $anchor = null): self {
 		if ($backend->exists('config')) {
 			throw new RepositoryException('A repository already exists at this location');
 		}
@@ -60,11 +64,13 @@ final class Repository {
 		$config = ['format' => self::FORMAT, 'id' => $id, 'created' => gmdate('c'), 'key' => $wrappedKey,
 			'check' => base64_encode((new StreamCipher($keys))->encryptString($id, 'config-check'))];
 		self::putString($backend, 'config', json_encode($config, JSON_PRETTY_PRINT | JSON_THROW_ON_ERROR));
-		return new self($backend, $keys, $id);
+		$repo = new self($backend, $keys, $id);
+		$repo->loadCatalog($anchor);
+		return $repo;
 	}
 
 	/** Open with the master key the server holds (scheduled backups, no passphrase needed). */
-	public static function openWithKey(IBackend $backend, KeyRing $keys, ?IIndexCache $cache = null): self {
+	public static function openWithKey(IBackend $backend, KeyRing $keys, ?IIndexCache $cache = null, ?ICatalogAnchor $anchor = null): self {
 		$config = self::readConfig($backend);
 		try {
 			$ok = isset($config['check']) && (new StreamCipher($keys))->decryptString((string)base64_decode($config['check'], true), 'config-check') === $config['id'];
@@ -79,9 +85,32 @@ final class Repository {
 			$repo->index->setCache($cache, $config['id']);
 		}
 		$repo->index->load();
+		$repo->loadCatalog($anchor);
 		return $repo;
 	}
 
+	private function loadCatalog(?ICatalogAnchor $anchor): void {
+		$this->catalog = new Catalog($this->backend, $this->cipher, $this->repositoryId, $anchor);
+		$this->catalog->load(
+			fn () => array_map('basename', $this->backend->listFiles('snapshots')),
+			fn () => array_map('basename', $this->backend->listFiles('trash/info')),
+			fn () => $this->backend->list('users'));
+	}
+
+	/** Refuse uploads that would make the stored data larger than this (null = no limit). */
+	public function setMaxBytes(?int $maxBytes): void {
+		$this->maxBytes = $maxBytes;
+	}
+
+	public function storedBytes(): int {
+		return $this->index->storedBytes();
+	}
+
+	/** Current catalog generation (for status and tests). */
+	public function catalogGeneration(): int {
+		return $this->catalog->gen;
+	}
+
 	/** Index files downloaded when this repository was opened (0 when the local cache was complete). */
 	public function indexDownloads(): int {
 		return $this->index->downloaded;
@@ -101,14 +130,22 @@ final class Repository {
 		return $config;
 	}
 
+	/** Replace the passphrase-wrapped key slots in this repository's config (after a slot change). */
+	public function updateWrappedKey(array $wrappedKey): void {
+		$config = self::readConfig($this->backend);
+		$config['key'] = $wrappedKey;
+		self::putString($this->backend, 'config', json_encode($config, JSON_PRETTY_PRINT | JSON_THROW_ON_ERROR));
+	}
+
 	public function id(): string {
 		return $this->repositoryId;
 	}
 
 	public static function open(IBackend $backend, #[\SensitiveParameter] string $passphrase): self {
 		$config = self::readConfig($backend);
-		$repo = new self($backend, KeyRing::unwrap($config['key'], $passphrase), $config['id']);
+		$repo = new self($backend, KeyRing::unwrapAny($config['key'], $passphrase), $config['id']);
 		$repo->index->load();
+		$repo->loadCatalog(null); // disaster recovery on a new server: no anchor yet, trust the newest valid chain
 		return $repo;
 	}
 
@@ -121,7 +158,7 @@ final class Repository {
 	public function backupDirectory(string $source, ?string $parent = null, string $label = ''): array {
 		$source = rtrim($source, '/');
 		$previous = $parent !== null ? $this->loadEntries($parent) : [];
-		$packs = new PackWriter($this->backend, $this->cipher, $this->index);
+		$packs = new PackWriter($this->backend, $this->cipher, $this->index, 32 * 1048576, $this->maxBytes);
 		$stats = ['files' => 0, 'reused' => 0, 'read' => 0, 'newBlobs' => 0, 'dupBlobs' => 0, 'uploaded' => 0];
 
 		$tree = fopen('php://temp/maxmemory:' . (4 * 1048576), 'w+b');
@@ -149,35 +186,65 @@ final class Repository {
 		rewind($encrypted);
 		$this->backend->put('snapshots/' . $snapshotId, $encrypted);
 		fclose($tree);
+		$this->catalog->snapshots[$snapshotId] = true;
+		$this->catalog->write();
 
 		return ['snapshot' => $snapshotId] + $stats;
 	}
 
-	/** Restore a snapshot (or only paths starting with $prefix) into a local directory. */
-	public function restore(string $snapshotId, string $target, string $prefix = ''): int {
+	/**
+	 * Restore a snapshot (or only paths starting with $prefix) into a local directory.
+	 *
+	 * @param bool $stripPrefix write "$target/<path without $prefix>" instead of
+	 *             "$target/<full logical path>" (disaster recovery: restoring e.g. "data/" or
+	 *             "config/" directly into the real data/config directory, not a subdirectory
+	 *             named after the prefix). Ignored when $prefix is '' (nothing to strip).
+	 */
+	public function restore(string $snapshotId, string $target, string $prefix = '', bool $stripPrefix = false, ?callable $heartbeat = null): int {
+		if ($prefix !== '' && !self::isSafePath(rtrim($prefix, '/'))) {
+			throw new RepositoryException('Invalid path prefix');
+		}
 		$count = 0;
 		foreach ($this->streamEntries($snapshotId) as $entry) {
 			if ($prefix !== '' && !str_starts_with($entry['p'], $prefix)) {
 				continue;
 			}
-			$dest = rtrim($target, '/') . '/' . $entry['p'];
+			$relPath = ($stripPrefix && $prefix !== '') ? substr($entry['p'], strlen(rtrim($prefix, '/')) + 1) : $entry['p'];
+			$dest = rtrim($target, '/') . '/' . $relPath;
 			if (!is_dir(dirname($dest))) {
 				mkdir(dirname($dest), 0700, true);
 			}
+			// Defence in depth: the resolved directory must stay below the target (no symlink escapes).
+			$base = realpath($target);
+			$dir = realpath(dirname($dest));
+			if ($base === false || $dir === false || ($dir !== $base && !str_starts_with($dir, $base . '/')) || is_link($dest)) {
+				throw new RepositoryException('Refusing to write outside the restore directory: ' . $entry['p']);
+			}
 			// Write next to the destination and rename after all blobs verified: at most one file
 			// is ever present twice.
-			$tmp = $dest . '.ngb-restore';
-			$out = fopen($tmp, 'wb');
+			$tmp = $dest . '.ngb-restore-' . bin2hex(random_bytes(6));
+			$out = @fopen($tmp, 'xb'); // fails if anything (including a symlink) already exists there
+			if ($out === false) {
+				throw new RepositoryException('Cannot create a temporary file for ' . $entry['p']);
+			}
 			foreach ($entry['b'] as $id) {
 				fwrite($out, $this->loadBlob($id));
+				if ($heartbeat !== null) {
+					$heartbeat();
+				}
 			}
 			fclose($out);
 			if (filesize($tmp) !== $entry['s']) {
 				unlink($tmp);
 				throw new RepositoryException('Size mismatch restoring ' . $entry['p']);
 			}
-			rename($tmp, $dest);
-			touch($dest, $entry['m']);
+			if (!rename($tmp, $dest)) {
+				@unlink($tmp);
+				throw new RepositoryException('Cannot put the restored file in place: ' . $entry['p']);
+			}
+			if (!touch($dest, $entry['m'])) {
+				throw new RepositoryException('Cannot set the modification time of ' . $entry['p']);
+			}
 			$count++;
 		}
 		return $count;
@@ -188,13 +255,22 @@ final class Repository {
 	 * run is done, so the last pack is uploaded before anything references it.
 	 */
 	public function blobWriter(array &$stats): BlobWriter {
-		$this->runPacks ??= new PackWriter($this->backend, $this->cipher, $this->index);
+		$this->runPacks ??= new PackWriter($this->backend, $this->cipher, $this->index, 32 * 1048576, $this->maxBytes);
 		$packs = $this->runPacks;
 		return new BlobWriter(function (string $data) use ($packs, &$stats): string {
 			return $this->storeBlob($data, $packs, $stats);
 		});
 	}
 
+	/** See BlobIndex::holdCache(): no database writes until releaseIndexCache(). */
+	public function holdIndexCache(): void {
+		$this->index->holdCache();
+	}
+
+	public function releaseIndexCache(): void {
+		$this->index->releaseCache();
+	}
+
 	public function flushPacks(): void {
 		$this->runPacks?->flush();
 	}
@@ -220,7 +296,7 @@ final class Repository {
 
 	/** Store one blob of file data in the current run (deduplicated); returns its id. */
 	public function storeData(string $data, array &$stats): string {
-		$this->runPacks ??= new PackWriter($this->backend, $this->cipher, $this->index);
+		$this->runPacks ??= new PackWriter($this->backend, $this->cipher, $this->index, 32 * 1048576, $this->maxBytes);
 		return $this->storeBlob($data, $this->runPacks, $stats);
 	}
 
@@ -231,6 +307,17 @@ final class Repository {
 	 * @param iterable<string> $lines
 	 */
 	public function writeSnapshot(string $snapshotId, array $meta, iterable $lines): void {
+		$this->putSnapshot($snapshotId, $meta, $lines);
+		$this->recordSnapshot($snapshotId);
+	}
+
+	/**
+	 * Store a snapshot object without touching the catalog. Use recordSnapshot() afterwards, from a
+	 * repository opened inside the catalog lock, so the catalog write builds on the latest generation.
+	 *
+	 * @param iterable<string> $lines
+	 */
+	public function putSnapshot(string $snapshotId, array $meta, iterable $lines): void {
 		$tree = fopen('php://temp/maxmemory:' . (4 * 1048576), 'w+b');
 		fwrite($tree, json_encode(['snapshot' => $snapshotId] + $meta, JSON_THROW_ON_ERROR) . "\n");
 		foreach ($lines as $line) {
@@ -246,6 +333,11 @@ final class Repository {
 		$this->backend->put('snapshots/' . $snapshotId, $encrypted);
 	}
 
+	public function recordSnapshot(string $snapshotId): void {
+		$this->catalog->snapshots[$snapshotId] = true;
+		$this->catalog->write();
+	}
+
 	/** @return array<string, array{s:int, m:int, b:list<string>}> */
 	public function snapshotEntries(string $snapshotId): array {
 		return $this->loadEntries($snapshotId);
@@ -261,6 +353,19 @@ final class Repository {
 		}
 	}
 
+	/** Relative path of non-empty segments, without ".", "..", NUL, backslash or control characters. */
+	public static function isSafePath(string $path): bool {
+		if ($path === '' || str_starts_with($path, '/') || preg_match('/[\x00-\x1f\\\\]/', $path)) {
+			return false;
+		}
+		foreach (explode('/', $path) as $segment) {
+			if ($segment === '' || $segment === '.' || $segment === '..') {
+				return false;
+			}
+		}
+		return true;
+	}
+
 	/** Small encrypted objects (manifests). */
 	public function putObject(string $path, string $data): void {
 		self::putString($this->backend, $path, $this->cipher->encryptString($data, 'object:' . $path));
@@ -273,9 +378,280 @@ final class Repository {
 		return $data;
 	}
 
-	/** @return list<string> */
+	/**
+	 * Move a snapshot (and its database dump) to the trash on the location. Its data stays in
+	 * use until purgeTrash() removes it after the deletion delay, so a malicious or mistaken
+	 * cleanup can be undone with untrash() within that time.
+	 */
+	public function forget(string $snapshotId, string $by = ''): void {
+		$meta = $this->snapshotMeta($snapshotId);
+		$dbInTrash = null;
+		if (isset($meta['db']) && is_string($meta['db']) && $this->backend->exists($meta['db'])) {
+			// Its encryption is bound to its path (object:db/...), which changes on a move, so it
+			// must be decrypted and re-encrypted under the new path, not moved as raw bytes.
+			$dbInTrash = 'trash/' . $meta['db'];
+			$this->putObject($dbInTrash, $this->getObject($meta['db']));
+		}
+		// Copy first, switch the catalog, delete the originals last: a crash at any point leaves
+		// either the old state or the new one plus unreferenced leftovers, never a catalog entry
+		// pointing at a missing object. The snapshot object is bound to its id (not its path),
+		// so it can be copied as raw bytes.
+		$this->copyRaw('snapshots/' . $snapshotId, 'trash/snapshots/' . $snapshotId);
+		$this->putObject('trash/info/' . $snapshotId, json_encode(['forgottenAt' => time(), 'by' => $by, 'db' => $meta['db'] ?? null,
+			'dbInTrash' => $dbInTrash, 'time' => $meta['time'] ?? null, 'label' => $meta['label'] ?? ''], JSON_THROW_ON_ERROR));
+		unset($this->catalog->snapshots[$snapshotId]);
+		$this->catalog->trash[$snapshotId] = true;
+		$this->catalog->write();
+		if ($dbInTrash !== null) {
+			$this->backend->delete($meta['db']);
+		}
+		$this->backend->delete('snapshots/' . $snapshotId);
+	}
+
+	/** Undo forget(): move a snapshot back from the trash. */
+	public function untrash(string $snapshotId): void {
+		$info = $this->trashInfo($snapshotId);
+		$restoreDb = $info['dbInTrash'] !== null && $this->backend->exists($info['dbInTrash']);
+		if ($restoreDb) {
+			$this->putObject($info['db'], $this->getObject($info['dbInTrash']));
+		}
+		// Same order as forget(): copy, switch the catalog, then delete the trash copies.
+		$this->copyRaw('trash/snapshots/' . $snapshotId, 'snapshots/' . $snapshotId);
+		$this->catalog->snapshots[$snapshotId] = true;
+		unset($this->catalog->trash[$snapshotId]);
+		$this->catalog->write();
+		if ($restoreDb) {
+			$this->backend->delete($info['dbInTrash']);
+		}
+		$this->backend->delete('trash/snapshots/' . $snapshotId);
+		$this->backend->delete('trash/info/' . $snapshotId);
+	}
+
+	/** Copy an object as raw bytes, buffered locally (remote read streams cannot be uploaded directly everywhere). */
+	private function copyRaw(string $from, string $to): void {
+		$in = $this->backend->get($from);
+		$buffer = fopen('php://temp/maxmemory:' . (4 * 1048576), 'w+b');
+		if ($buffer === false) {
+			fclose($in);
+			throw new RepositoryException("Cannot buffer $from");
+		}
+		try {
+			if (stream_copy_to_stream($in, $buffer) === false) {
+				throw new RepositoryException("Cannot read $from");
+			}
+		} finally {
+			fclose($in);
+		}
+		rewind($buffer);
+		$this->backend->put($to, $buffer);
+	}
+
+	/** Record a user_migration export's manifest in the catalog (rollback-protected like a snapshot). */
+	public function recordUserExport(string $manifestPath): void {
+		$this->catalog->userExports[$manifestPath] = true;
+		$this->catalog->write();
+	}
+
+	/**
+	 * User export manifests according to the verified catalog, newest first. A manifest the
+	 * catalog lists but the location no longer has means it was deleted or hidden behind NG
+	 * Backup's back, same as a missing snapshot (see listSnapshots()).
+	 *
+	 * @return list<string>
+	 */
+	public function listUserExports(?string $uid = null): array {
+		$prefix = $uid !== null ? 'users/' . $uid . '/' : 'users/';
+		$out = [];
+		foreach (array_keys($this->catalog->userExports) as $path) {
+			if (!str_starts_with($path, $prefix)) {
+				continue;
+			}
+			if (!$this->backend->exists($path)) {
+				throw new RepositoryException("User export $path is missing on the location (deleted or hidden outside NG Backup)");
+			}
+			$out[] = $path;
+		}
+		sort($out, SORT_STRING);
+		return array_reverse($out);
+	}
+
+	/** Whether $manifestPath is a user export the verified catalog actually recorded. */
+	public function isRecordedUserExport(string $manifestPath): bool {
+		return isset($this->catalog->userExports[$manifestPath]);
+	}
+
+	/** Permanently delete a user export. Its blobs are freed by the next prune() like any other. */
+	public function forgetUserExport(string $manifestPath): void {
+		if (!isset($this->catalog->userExports[$manifestPath])) {
+			throw new RepositoryException("$manifestPath is not a recorded user export");
+		}
+		unset($this->catalog->userExports[$manifestPath]);
+		$this->catalog->write();
+		$this->backend->delete($manifestPath);
+	}
+
+	/** @return array<string, array{forgottenAt:int, by:string, db:?string, dbInTrash:?string, time:?string, label:string}> */
+	public function trash(): array {
+		$out = [];
+		foreach (array_keys($this->catalog->trash) as $id) {
+			try {
+				$out[$id] = $this->trashInfo($id);
+			} catch (\Throwable) {
+				throw new RepositoryException("Trash entry $id listed in the catalog is missing on the location (possible tampering)");
+			}
+		}
+		return $out;
+	}
+
+	/** Permanently delete trash entries older than $delaySeconds. @return list<string> purged snapshot ids */
+	public function purgeTrash(int $delaySeconds): array {
+		$doomed = [];
+		foreach ($this->trash() as $id => $info) {
+			if (time() - $info['forgottenAt'] < $delaySeconds) {
+				continue;
+			}
+			$doomed[$id] = $info;
+			unset($this->catalog->trash[$id]);
+		}
+		if ($doomed === []) {
+			return [];
+		}
+		$this->catalog->write();
+		foreach ($doomed as $id => $info) {
+			if ($info['dbInTrash'] !== null) {
+				$this->backend->delete($info['dbInTrash']);
+			}
+			$this->backend->delete('trash/snapshots/' . $id);
+			$this->backend->delete('trash/info/' . $id);
+		}
+		return array_keys($doomed);
+	}
+
+	private function trashInfo(string $snapshotId): array {
+		return json_decode($this->getObject('trash/info/' . $snapshotId), true, 512, JSON_THROW_ON_ERROR);
+	}
+
+	/**
+	 * Delete packs no snapshot or user export uses any more, and repack packs where more than
+	 * $repackThreshold of the bytes are unused. Must not run while a backup to this repository
+	 * is in progress (its blobs are not referenced by a snapshot yet); callers hold the lock.
+	 *
+	 * @return array{packs:int, deleted:int, repacked:int, freedBytes:int, keptBlobs:int, unusedBlobs:int}
+	 */
+	public function prune(bool $dryRun = false, float $repackThreshold = 0.5, array $ignoreSnapshots = []): array {
+		// Deleting is decided on the authenticated index files on the location, never on the local cache.
+		$this->index->load(true);
+		$used = [];
+		$ignore = array_flip($ignoreSnapshots); // e.g. snapshots a dry run would forget first
+		foreach ($this->listSnapshots() as $sid) {
+			if (isset($ignore[$sid])) {
+				continue;
+			}
+			foreach ($this->streamEntries($sid) as $e) {
+				foreach ($e['b'] as $b) {
+					$used[$b] = true;
+				}
+			}
+			$meta = $this->snapshotMeta($sid);
+			if (isset($meta['db']) && $this->backend->exists($meta['db'])) {
+				foreach (json_decode($this->getObject($meta['db']), true, 512, JSON_THROW_ON_ERROR)['tables'] as $t) {
+					foreach ($t['blobs'] as $b) {
+						$used[$b] = true;
+					}
+				}
+			}
+		}
+		// Snapshots in the trash keep their data until purgeTrash() removed them.
+		foreach ($this->trash() as $sid => $info) {
+			foreach ($this->streamEntries($sid, 'trash/snapshots/') as $e) {
+				foreach ($e['b'] as $b) {
+					$used[$b] = true;
+				}
+			}
+			if ($info['dbInTrash'] !== null && $this->backend->exists($info['dbInTrash'])) {
+				foreach (json_decode($this->getObject($info['dbInTrash']), true, 512, JSON_THROW_ON_ERROR)['tables'] as $t) {
+					foreach ($t['blobs'] as $b) {
+						$used[$b] = true;
+					}
+				}
+			}
+		}
+		// listUserExports() throws when a recorded export's manifest is missing: then stop, since
+		// freeing its blobs would turn a tampering or storage alarm into irreversible deletion.
+		$exports = array_unique(array_merge($this->listUserExports(), $this->backend->list('users')));
+		foreach ($exports as $path) {
+			foreach (json_decode($this->getObject($path), true, 512, JSON_THROW_ON_ERROR)['entries'] as $e) {
+				foreach ($e['b'] ?? [] as $b) {
+					$used[$b] = true;
+				}
+			}
+		}
+
+		$stats = ['packs' => 0, 'deleted' => 0, 'repacked' => 0, 'freedBytes' => 0, 'keptBlobs' => count($used), 'unusedBlobs' => 0];
+		$packs = $this->index->packs();
+		$stats['packs'] = count($packs);
+		$writer = null;
+		$toRemove = [];
+		foreach ($packs as $packId => $blobs) {
+			$total = 0;
+			$unused = 0;
+			foreach ($blobs as $b) {
+				$total += $b['length'];
+				if (!isset($used[$b['id']])) {
+					$unused += $b['length'];
+					$stats['unusedBlobs']++;
+				}
+			}
+			if ($unused === 0 || ($unused < $total && $unused / $total <= $repackThreshold)) {
+				continue;
+			}
+			$stats['freedBytes'] += $unused;
+			if ($unused === $total) {
+				$stats['deleted']++;
+			} else {
+				$stats['repacked']++;
+				if (!$dryRun) {
+					// No size limit here: repacking is how space is freed.
+					$writer ??= new PackWriter($this->backend, $this->cipher, $this->index);
+					$path = 'packs/' . substr($packId, 0, 2) . '/' . $packId;
+					foreach ($blobs as $b) {
+						if (isset($used[$b['id']])) {
+							[, , , $raw, $flags] = $this->index->get($b['id']);
+							$writer->addRaw($b['id'], $this->backend->getRange($path, $b['offset'], $b['length']), $raw, $flags);
+						}
+					}
+				}
+			}
+			$toRemove[] = $packId;
+		}
+		if ($dryRun) {
+			return $stats;
+		}
+		// New packs and their index entries are durable before any old pack is removed.
+		$writer?->flush();
+		foreach ($toRemove as $packId) {
+			$this->index->removePack($packId);
+			$this->backend->delete('packs/' . substr($packId, 0, 2) . '/' . $packId);
+		}
+		return $stats;
+	}
+
+	/**
+	 * Snapshots according to the verified catalog. A snapshot the catalog lists but the location
+	 * no longer has means it was deleted or hidden behind NG Backup's back.
+	 *
+	 * @return list<string>
+	 */
 	public function listSnapshots(): array {
-		return array_map('basename', $this->backend->list('snapshots'));
+		$present = array_flip(array_map('basename', $this->backend->listFiles('snapshots')));
+		$listed = array_keys($this->catalog->snapshots);
+		foreach ($listed as $id) {
+			if (!isset($present[$id])) {
+				throw new RepositoryException("Snapshot $id is missing on the location (deleted or hidden outside NG Backup)");
+			}
+		}
+		sort($listed);
+		return $listed;
 	}
 
 	public function blobCount(): int {
@@ -331,8 +707,13 @@ final class Repository {
 	}
 
 	private function loadBlob(string $id): string {
-		[$pack, $offset, $length, $raw, $flags] = $this->index->get($id);
-		$encrypted = $this->backend->getRange('packs/' . substr($pack, 0, 2) . '/' . $pack, $offset, $length);
+		[$pack, $offset, $length] = $this->index->get($id);
+		return $this->decodeBlob($id, $this->backend->getRange('packs/' . substr($pack, 0, 2) . '/' . $pack, $offset, $length));
+	}
+
+	/** Decrypts and checks a blob read from its pack; throws when it is corrupted or tampered with. */
+	private function decodeBlob(string $id, string $encrypted): string {
+		[, , , $raw, $flags] = $this->index->get($id);
 		$payload = $this->cipher->decryptString($encrypted, 'blob:' . $id);
 		$data = ($flags & self::FLAG_DEFLATE) ? gzinflate($payload) : $payload;
 		if ($data === false || strlen($data) !== $raw || $this->keys->blobId($data) !== $id) {
@@ -355,6 +736,134 @@ final class Repository {
 		return $this->streamEntries($snapshotId);
 	}
 
+	/**
+	 * Checksum audit of a snapshot: every blob it references (files and the database dump, when
+	 * the snapshot has one) must be in the index, freshly re-downloaded and re-authenticated from
+	 * the location rather than trusted from the local cache (same reasoning as prune()), and its
+	 * pack must still be present. With $deep, each blob is also downloaded and decrypted, which
+	 * verifies its AEAD authentication tag and its content hash against the blob id (loadBlob()
+	 * already does both on every real read -- this just does it for everything in the snapshot,
+	 * deliberately, rather than relying on it to come up during a later restore). A blob
+	 * referenced by more than one file is only checked once; a missing database manifest is a
+	 * failure, not something to silently skip over.
+	 *
+	 * @param ?callable $heartbeat called after every blob (shallow) or every blob read (deep);
+	 *        callers use it to keep a time-boxed lease alive during a large audit
+	 * @return array{filesChecked:int, blobsChecked:int, bytesChecked:int, missing:list<string>, failed:list<string>, unreadable:list<string>, readError:string}
+	 */
+	public function verify(string $snapshotId, bool $deep = false, ?callable $heartbeat = null): array {
+		$heartbeat ??= static function (): void {
+		};
+		$this->index->load(true);
+		$stats = ['filesChecked' => 0, 'blobsChecked' => 0, 'bytesChecked' => 0, 'missing' => [], 'failed' => [], 'unreadable' => [], 'readError' => ''];
+		$seen = [];
+		$packSeen = []; // pack id => exists on the backend; avoids one exists() call per blob
+		foreach ($this->streamEntries($snapshotId) as $entry) {
+			$stats['filesChecked']++;
+			foreach ($entry['b'] as $id) {
+				if (isset($seen[$id])) {
+					continue;
+				}
+				$seen[$id] = true;
+				$this->verifyBlob($id, $deep, $stats, $packSeen);
+				$heartbeat();
+			}
+		}
+		$meta = $this->snapshotMeta($snapshotId);
+		if (isset($meta['db']) && is_string($meta['db'])) {
+			if (!$this->backend->exists($meta['db'])) {
+				$stats['missing'][] = $meta['db'];
+			} else {
+				$dbManifest = json_decode($this->getObject($meta['db']), true, 512, JSON_THROW_ON_ERROR);
+				foreach ($dbManifest['tables'] as $info) {
+					foreach ($info['blobs'] as $id) {
+						if (isset($seen[$id])) {
+							continue;
+						}
+						$seen[$id] = true;
+						$this->verifyBlob($id, $deep, $stats, $packSeen);
+						$heartbeat();
+					}
+				}
+			}
+		}
+		return $stats;
+	}
+
+	/**
+	 * Same checks as verify(), for a user export: every blob its manifest references must be in
+	 * the freshly re-authenticated index with its pack present; $deep also decrypts each.
+	 *
+	 * @return array{filesChecked:int, blobsChecked:int, bytesChecked:int, missing:list<string>, failed:list<string>, unreadable:list<string>, readError:string}
+	 */
+	public function verifyUserExport(string $manifestPath, bool $deep = false, ?callable $heartbeat = null): array {
+		if (!$this->isRecordedUserExport($manifestPath)) {
+			throw new RepositoryException("$manifestPath is not a recorded user export for this location");
+		}
+		$heartbeat ??= static function (): void {
+		};
+		$this->index->load(true);
+		$stats = ['filesChecked' => 0, 'blobsChecked' => 0, 'bytesChecked' => 0, 'missing' => [], 'failed' => [], 'unreadable' => [], 'readError' => ''];
+		$seen = [];
+		$packSeen = [];
+		$manifest = json_decode($this->getObject($manifestPath), true, 512, JSON_THROW_ON_ERROR);
+		foreach ($manifest['entries'] as $entry) {
+			if (($entry['t'] ?? '') !== 'f') {
+				continue;
+			}
+			$stats['filesChecked']++;
+			foreach ($entry['b'] ?? [] as $id) {
+				if (isset($seen[$id])) {
+					continue;
+				}
+				$seen[$id] = true;
+				$this->verifyBlob($id, $deep, $stats, $packSeen);
+				$heartbeat();
+			}
+		}
+		return $stats;
+	}
+
+	/** @param array<string, bool> $packSeen */
+	private function verifyBlob(string $id, bool $deep, array &$stats, array &$packSeen): void {
+		if (!$this->index->has($id)) {
+			$stats['missing'][] = $id;
+			return;
+		}
+		[$pack] = $this->index->get($id);
+		$packExists = $packSeen[$pack] ??= $this->backend->exists('packs/' . substr($pack, 0, 2) . '/' . $pack);
+		if (!$packExists) {
+			$stats['missing'][] = $id;
+			return;
+		}
+		$stats['blobsChecked']++;
+		if (!$deep) {
+			return;
+		}
+		// Reading and checking are kept apart: a read that fails is usually a network or
+		// storage error, so it is retried and reported as unreadable (a pack that stays
+		// unreadable may still be truncated). Only a blob that was read but does not
+		// decrypt or match its id counts as failed: that is proof of damage.
+		[, $offset, $length] = $this->index->get($id);
+		$encrypted = null;
+		for ($attempt = 1; $attempt <= self::VERIFY_READ_ATTEMPTS && $encrypted === null; $attempt++) {
+			try {
+				$encrypted = $this->backend->getRange('packs/' . substr($pack, 0, 2) . '/' . $pack, $offset, $length);
+			} catch (\Exception $e) { // storage adapters throw their own exceptions; \Error (a bug) is not retried
+				$stats['readError'] = $e->getMessage();
+			}
+		}
+		if ($encrypted === null) {
+			$stats['unreadable'][] = $id;
+			return;
+		}
+		try {
+			$stats['bytesChecked'] += strlen($this->decodeBlob($id, $encrypted));
+		} catch (\Throwable) {
+			$stats['failed'][] = $id;
+		}
+	}
+
 	/** The meta record (first line) of a snapshot. */
 	public function snapshotMeta(string $snapshotId): array {
 		$plain = fopen('php://temp/maxmemory:' . (4 * 1048576), 'w+b');
@@ -368,15 +877,20 @@ final class Repository {
 	}
 
 	/** @return \Generator<array{p:string, s:int, m:int, b:list<string>}> */
-	private function streamEntries(string $snapshotId): \Generator {
+	private function streamEntries(string $snapshotId, string $dir = 'snapshots/'): \Generator {
 		$plain = fopen('php://temp/maxmemory:' . (4 * 1048576), 'w+b');
-		$fh = $this->backend->get('snapshots/' . $snapshotId);
+		$fh = $this->backend->get($dir . $snapshotId);
 		$this->cipher->decrypt($fh, $plain, 'snapshot:' . $snapshotId);
 		fclose($fh);
 		rewind($plain);
 		fgets($plain); // meta line
 		while (($line = fgets($plain)) !== false) {
-			yield json_decode($line, true, 512, JSON_THROW_ON_ERROR);
+			$entry = json_decode($line, true, 512, JSON_THROW_ON_ERROR);
+			if (!is_array($entry) || !is_string($entry['p'] ?? null) || !self::isSafePath($entry['p'])
+				|| !is_int($entry['s'] ?? null) || !is_array($entry['b'] ?? null)) {
+				throw new RepositoryException('Invalid entry in snapshot ' . $snapshotId);
+			}
+			yield $entry;
 		}
 		fclose($plain);
 	}

lib/Service/AlertService.php

@@ -0,0 +1,121 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCA\NgBackup\AppInfo\Application;
+use OCA\NgBackup\Db\Run;
+use OCA\NgBackup\Db\RunMapper;
+use OCA\NgBackup\Db\Target;
+use OCP\IGroupManager;
+use OCP\Notification\IManager;
+
+/** Notifies administrators about failed runs and locations without a recent successful backup. */
+final class AlertService {
+	public const STALE_AFTER = 2 * 86400;
+
+	public function __construct(
+		private IManager $notifications,
+		private IGroupManager $groups,
+		private RunMapper $runs,
+		private \OCP\IAppConfig $appConfig,
+		private \OCP\EventDispatcher\IEventDispatcher $events,
+		private \OCP\IUserSession $session,
+	) {
+	}
+
+	/**
+	 * Security-relevant change (recovery kit downloaded, location removed, append-only off,
+	 * retention changed, snapshots forgotten): written to the audit log (admin_audit) and sent
+	 * to every administrator, so a single compromised admin account cannot do it unnoticed.
+	 *
+	 * @param array<string, string> $params
+	 */
+	public function actor(): string {
+		return $this->session->getUser()?->getUID() ?? (PHP_SAPI === 'cli' ? 'occ' : 'unknown');
+	}
+
+	public function securityEvent(string $event, array $params = [], bool $notify = true): void {
+		$actor = $this->actor();
+		$params = ['actor' => $actor] + $params;
+		$this->events->dispatchTyped(new \OCP\Log\Audit\CriticalActionPerformedEvent(
+			'NG Backup: %s by %s ' . json_encode(array_diff_key($params, ['actor' => 1]), JSON_UNESCAPED_SLASHES), ['event' => $event, 'actor' => $actor]));
+		if ($notify) {
+			$this->notifyAdmins('security_event', $event . '-' . time(), ['event' => $event] + $params);
+		}
+	}
+
+	public function runFailed(Run $run, string $targetName): void {
+		$this->notifyAdmins('run_failed', 'run-' . $run->getId(),
+			['kind' => $run->getKind(), 'target' => $targetName, 'error' => mb_strimwidth((string)$run->getError(), 0, 300, '…')]);
+	}
+
+	/** A backup that finished but is missing unreadable files, or holds files that changed while read. */
+	public function runWarnings(Run $run, string $targetName, int $unreadable, int $changing, array $examples): void {
+		$this->notifyAdmins('run_warnings', 'run-' . $run->getId(), ['target' => $targetName,
+			'unreadable' => (string)$unreadable, 'changing' => (string)$changing,
+			'examples' => mb_strimwidth(implode(', ', array_merge($examples['unreadable'], $examples['changing'])), 0, 300, '…')]);
+	}
+
+	/**
+	 * Remember how much is stored on a location (for the settings page) and warn administrators
+	 * once a day when it is at 80% of its limit or more.
+	 */
+	public function storedBytes(Target $target, int $bytes): void {
+		$this->appConfig->setValueString(Application::APP_ID, 'stored_' . $target->getId(), (string)$bytes);
+		$limit = $target->getMaxBytes();
+		if ($limit === null || $limit <= 0 || $bytes < 0.8 * $limit) {
+			return;
+		}
+		$key = 'quota_notified_' . $target->getId();
+		if ($this->appConfig->getValueString(Application::APP_ID, $key, '') === date('Y-m-d')) {
+			return;
+		}
+		$this->appConfig->setValueString(Application::APP_ID, $key, date('Y-m-d'));
+		$this->notifyAdmins('quota_warning', 'quota-' . $target->getId() . '-' . date('Y-m-d'), [
+			'target' => $target->getName(), 'percent' => (string)round($bytes / $limit * 100),
+			'used' => self::gib($bytes), 'limit' => self::gib($limit)]);
+	}
+
+	private static function gib(int $bytes): string {
+		$g = $bytes / 1073741824;
+		return sprintf($g < 10 ? '%.2f GiB' : '%.1f GiB', $g);
+	}
+
+	public function lastStoredBytes(Target $target): ?int {
+		$v = $this->appConfig->getValueString(Application::APP_ID, 'stored_' . $target->getId(), '');
+		return $v === '' ? null : (int)$v;
+	}
+
+	/** At most one notification per location per day. */
+	public function checkStale(Target $target): void {
+		$last = $this->runs->lastFinished($target->getId(), BackupService::KIND_FULL);
+		$lastTime = $last?->getFinishedAt() ?? $target->getCreatedAt();
+		if (time() - $lastTime < self::STALE_AFTER || $this->runs->findRunning($target->getId(), BackupService::KIND_FULL) !== []) {
+			return;
+		}
+		$key = 'stale_notified_' . $target->getId();
+		if ($this->appConfig->getValueString(Application::APP_ID, $key, '') === date('Y-m-d')) {
+			return;
+		}
+		$this->appConfig->setValueString(Application::APP_ID, $key, date('Y-m-d'));
+		$this->notifyAdmins('backup_stale', 'stale-' . $target->getId() . '-' . date('Y-m-d'),
+			['target' => $target->getName(), 'since' => $last ? date('Y-m-d H:i', $lastTime) : 'never']);
+	}
+
+	private function notifyAdmins(string $subject, string $objectId, array $params): void {
+		foreach ($this->groups->get('admin')?->getUsers() ?? [] as $admin) {
+			$n = $this->notifications->createNotification();
+			$n->setApp(Application::APP_ID)
+				->setUser($admin->getUID())
+				->setDateTime(new \DateTime())
+				->setObject($subject, $objectId)
+				->setSubject($subject, $params);
+			$this->notifications->notify($n);
+		}
+	}
+}

lib/Service/BackupService.php

@@ -14,6 +14,7 @@ use OCA\NgBackup\Db\Snapshot;
 use OCA\NgBackup\Db\SnapshotMapper;
 use OCA\NgBackup\Db\Target;
 use OCA\NgBackup\Job\BackupRun;
+use OCA\NgBackup\Repository\RepositoryException;
 use OCP\App\IAppManager;
 use OCP\IConfig;
 use OCP\IDBConnection;
@@ -28,7 +29,7 @@ use Psr\Log\LoggerInterface;
  * Excluded by default: previews, log files, the updater's backups and each user's cache and
  * temporary uploads (all regenerable or temporary).
  */
-class BackupService {
+final class BackupService {
 	public const KIND_FULL = 'full';
 
 	public function __construct(
@@ -41,16 +42,33 @@ class BackupService {
 		private IAppManager $appManager,
 		private ILockingProvider $locking,
 		private LoggerInterface $logger,
+		private AlertService $alerts,
+		private LeaseService $leases,
 	) {
 	}
 
 	public function start(Target $target, string $label = ''): Run {
-		if ($this->keys->recoveryKitConfirmation() === null) {
+		if (!$this->keys->everConfirmed()) {
 			throw new \RuntimeException('Confirm the recovery kit first (occ backup:key:confirm)');
 		}
 		if ($this->config->getSystemValue('objectstore', null) !== null) {
 			throw new \RuntimeException('Object storage as primary storage is not supported yet');
 		}
+		// Check and create the run under the location's exclusive lock, so a cleanup cannot start
+		// in between (it takes the same lock and refuses while a run exists).
+		// A run that is already in progress is simply continued; no lease needed for that.
+		$running = $this->runs->findRunning($target->getId(), self::KIND_FULL);
+		if ($running !== []) {
+			return $running[0];
+		}
+		try {
+			return $this->leases->with(PruneService::lockKey($target), LeaseService::EXCLUSIVE, 60, fn () => $this->createRun($target, $label));
+		} catch (LockedException) {
+			throw new \RuntimeException('A cleanup or another start for ' . $target->getName() . ' is running; try again later');
+		}
+	}
+
+	private function createRun(Target $target, string $label): Run {
 		$running = $this->runs->findRunning($target->getId(), self::KIND_FULL);
 		if ($running !== []) {
 			return $running[0];
@@ -86,10 +104,18 @@ class BackupService {
 	 * run locked and returns immediately.
 	 */
 	public function step(Run $run, float $deadline): Run {
-		$lockKey = 'ng_backup/run/' . $run->getId();
+		// Leases expire on their own: a step killed by a time limit or OOM blocks nothing for long.
+		$ttl = (int)min(3600, max(120, $deadline - microtime(true) + 120));
 		try {
-			$this->locking->acquireLock($lockKey, ILockingProvider::LOCK_EXCLUSIVE);
+			$runLease = $this->leases->acquire('run/' . $run->getId(), LeaseService::EXCLUSIVE, $ttl);
 		} catch (LockedException) {
+			return $run; // another process is doing this step
+		}
+		// Shared lease on the location while this step writes: a cleanup (exclusive) cannot run now.
+		try {
+			$targetLease = $this->leases->acquire('ng_backup/target/' . $run->getTargetId(), LeaseService::SHARED, $ttl);
+		} catch (LockedException) {
+			$this->leases->release($runLease);
 			return $run;
 		}
 		try {
@@ -102,18 +128,49 @@ class BackupService {
 			$state = json_decode($run->getState(), true, 512, JSON_THROW_ON_ERROR);
 
 			if ($run->getPhase() === 'db') {
-				@set_time_limit(0); // the dump is one transaction; it cannot be split across requests yet
-				$dbStats = [];
-				$manifest = (new DbDumper($this->db->getInner(), $this->config->getSystemValueString('dbtableprefix', 'oc_')))->dump($repo, $dbStats);
-				$repo->putObject('db/' . $state['files']['snapshot'], json_encode($manifest, JSON_THROW_ON_ERROR));
-				$state['files']['meta']['db'] = 'db/' . $state['files']['snapshot'];
-				$state['dbStats'] = $dbStats + ['tables' => count($manifest['tables']),
-					'rows' => array_sum(array_column($manifest['tables'], 'rows'))];
-				$run->setPhase('files');
+				$dumper = new DbDumper($this->db->getInner(), $this->config->getSystemValueString('dbtableprefix', 'oc_'));
+				$dbStats = $state['dbStats'] ?? [];
+				// With system cron the whole dump usually fits in one step (one transaction, fully
+				// consistent). Under web cron it continues per step; the snapshot then says so.
+				$dump = $dumper->dumpStep($repo, $state['dump'] ?? $dumper->startDump(), $deadline, $dbStats);
+				$state['dbStats'] = $dbStats;
+				if ($dump['done']) {
+					$manifest = $dumper->manifest($dump);
+					$repo->putObject('db/' . $state['files']['snapshot'], json_encode($manifest, JSON_THROW_ON_ERROR));
+					$state['files']['meta']['db'] = 'db/' . $state['files']['snapshot'];
+					$state['files']['meta']['dbConsistent'] = $manifest['consistent'];
+					$state['dbStats'] += ['tables' => count($manifest['tables']), 'rows' => array_sum(array_column($manifest['tables'], 'rows')),
+						'steps' => $dump['steps'], 'consistent' => $manifest['consistent']];
+					unset($state['dump']);
+					$run->setPhase('files');
+				} else {
+					$state['dump'] = $dump;
+				}
 			} else {
 				$state['files'] = BackupRun::step($repo, $state['files'], $deadline);
+				if ($state['files']['phase'] === 'commit') {
+					// Catalog write under the catalog lock, from a repository opened inside it: a per-user
+					// export or restore may have written the catalog since this step opened $repo.
+					try {
+						$this->leases->with(PruneService::catalogLockKey($target), LeaseService::EXCLUSIVE, 300,
+							fn () => $this->targets->repository($target)->recordSnapshot((string)$state['files']['snapshot']));
+						$state['files']['phase'] = 'done';
+					} catch (LockedException|RepositoryException) {
+						// Another catalog write is in progress (or just raced us to the next
+						// generation): the next step retries this commit on the fresh catalog.
+					}
+				}
 				if ($state['files']['phase'] === 'done') {
 					$this->recordSnapshot($run, $state['files']);
+					$this->alerts->storedBytes($target, $repo->storedBytes());
+					$stats = $state['files']['stats'];
+					if (($stats['unreadable'] ?? 0) > 0 || ($stats['changing'] ?? 0) > 0) {
+						$warnings = BackupRun::warnings($state['files']);
+						$this->logger->warning(sprintf('NG Backup run %d to %s: %d unreadable (missing from the snapshot): %s; %d changed while being read: %s',
+							$run->getId(), $target->getName(), $stats['unreadable'] ?? 0, implode(', ', $warnings['unreadable']),
+							$stats['changing'] ?? 0, implode(', ', $warnings['changing'])));
+						$this->alerts->runWarnings($run, $target->getName(), (int)($stats['unreadable'] ?? 0), (int)($stats['changing'] ?? 0), $warnings);
+					}
 					$run->setStatus(Run::DONE);
 					$run->setPhase('done');
 					$run->setFinishedAt(time());
@@ -129,16 +186,29 @@ class BackupService {
 			$run->setError($e->getMessage());
 			$run->setFinishedAt(time());
 			$run->setUpdatedAt(time());
-			return $this->runs->update($run);
+			$run = $this->runs->update($run);
+			try {
+				$this->alerts->runFailed($run, isset($target) ? $target->getName() : '#' . $run->getTargetId());
+			} catch (\Throwable) {
+			}
+			return $run;
 		} finally {
-			$this->locking->releaseLock($lockKey, ILockingProvider::LOCK_EXCLUSIVE);
+			$this->leases->release($targetLease);
+			$this->leases->release($runLease);
 		}
 	}
 
 	/** Run to completion in this process (occ, system cron), reporting progress. */
 	public function runToCompletion(Run $run, ?callable $progress = null, float $stepSeconds = 30): Run {
 		while ($run->getStatus() === Run::RUNNING) {
+			$before = $run->getUpdatedAt();
 			$run = $this->step($run, microtime(true) + $stepSeconds);
+			if ($run->getStatus() === Run::RUNNING && $run->getUpdatedAt() === $before) {
+				// Step was not possible (another process holds the run, or a crashed step's lease has
+				// not expired yet): wait instead of spinning.
+				sleep(5);
+				$run = $this->runs->find($run->getId());
+			}
 			if ($progress !== null) {
 				$progress($run);
 			}
@@ -177,6 +247,15 @@ class BackupService {
 			'data/*/cache',
 			'data/*/uploads',
 		];
+		// SQLite: the database file is in the data directory; it is backed up by the logical dump,
+		// and copying the live file would give an inconsistent copy.
+		if ($this->config->getSystemValueString('dbtype') === 'sqlite3') {
+			$dbName = $this->config->getSystemValueString('dbname', 'owncloud');
+			$exclude[] = "data/$dbName.db";
+			$exclude[] = "data/$dbName.db-journal";
+			$exclude[] = "data/$dbName.db-wal";
+			$exclude[] = "data/$dbName.db-shm";
+		}
 		$logFile = $this->config->getSystemValueString('logfile', '');
 		if ($logFile !== '' && str_starts_with($logFile, $dataDir . '/')) {
 			$exclude[] = 'data/' . substr($logFile, strlen($dataDir) + 1);

lib/Service/KeyService.php

@@ -22,11 +22,15 @@ use OCP\Security\ICrypto;
  *   into the recovery kit, so backups can be restored on a fresh server with the passphrase.
  * - The admin must confirm having stored the recovery kit before the first backup runs.
  */
-class KeyService {
+final class KeyService {
 	private const KEY_MASTER = 'master_key';
 	private const KEY_WRAPPED = 'master_key_wrapped';
 	private const KEY_CONFIRMED = 'recovery_kit_confirmed';
 	private const KEY_FINGERPRINT = 'master_key_fingerprint';
+	private const KEY_DELETE_DELAY = 'delete_delay_days';
+	private const KEY_KIT_VERSION = 'recovery_kit_version';
+	private const KEY_KIT_CODE = 'recovery_kit_code';
+	public const DEFAULT_DELETE_DELAY = 7;
 
 	private ?KeyRing $cached = null;
 
@@ -40,7 +44,15 @@ class KeyService {
 		return $this->appConfig->getValueString(Application::APP_ID, self::KEY_MASTER, '', true) !== '';
 	}
 
-	public function initialize(#[\SensitiveParameter] string $passphrase): void {
+	/**
+	 * @param int $deleteDelayDays how long forgotten snapshots stay in the trash on the location
+	 *                             before their data is really deleted. Fixed here, at installation:
+	 *                             there is deliberately no way to change it later from NG Backup.
+	 */
+	public function initialize(#[\SensitiveParameter] string $passphrase, int $deleteDelayDays = self::DEFAULT_DELETE_DELAY, string $label = 'Slot 1'): void {
+		if ($deleteDelayDays < 1 || $deleteDelayDays > 365) {
+			throw new \InvalidArgumentException('The deletion delay must be between 1 and 365 days');
+		}
 		if ($this->isInitialized()) {
 			throw new \RuntimeException('A backup key already exists');
 		}
@@ -50,13 +62,95 @@ class KeyService {
 		$keys = KeyRing::generate();
 		$this->appConfig->setValueString(Application::APP_ID, self::KEY_MASTER,
 			$this->crypto->encrypt(base64_encode($keys->exportMasterKey())), true, true);
-		$this->appConfig->setValueString(Application::APP_ID, self::KEY_WRAPPED,
-			json_encode($keys->wrap($passphrase), JSON_THROW_ON_ERROR), true, true);
+		$this->cached = $keys;
+		$this->saveSlots([['slot' => 1, 'label' => self::cleanLabel($label), 'created' => time(), 'key' => $keys->wrap($passphrase)]]);
 		$this->appConfig->setValueString(Application::APP_ID, self::KEY_FINGERPRINT, $this->fingerprintOf($keys), true);
+		$this->appConfig->setValueInt(Application::APP_ID, self::KEY_DELETE_DELAY, $deleteDelayDays, true);
+		$this->appConfig->setValueInt(Application::APP_ID, self::KEY_KIT_VERSION, 1, true);
 		$this->appConfig->deleteKey(Application::APP_ID, self::KEY_CONFIRMED);
 		$this->cached = $keys;
 	}
 
+	/**
+	 * Disaster recovery on a fresh installation: adopt the master key from a recovery kit
+	 * (occ backup:key:kit on the original installation) instead of generating a new one.
+	 * Afterwards occ backup:target:add opens the existing repository on the location with this
+	 * key, instead of creating a new, empty one.
+	 *
+	 * @param array<string, mixed> $kit as produced by recoveryKit()
+	 * @throws \OCA\NgBackup\Crypto\CryptoException wrong passphrase, or a damaged/foreign kit
+	 */
+	public function importRecoveryKit(array $kit, #[\SensitiveParameter] string $passphrase): void {
+		if ($this->isInitialized()) {
+			throw new \RuntimeException('A backup key already exists');
+		}
+		if (!isset($kit['wrapped_key'])) {
+			throw new \InvalidArgumentException('Not a NG Backup recovery kit file');
+		}
+		$keys = KeyRing::unwrapAny($kit['wrapped_key'], $passphrase);
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_MASTER,
+			$this->crypto->encrypt(base64_encode($keys->exportMasterKey())), true, true);
+		$this->cached = $keys;
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_WRAPPED, json_encode($kit['wrapped_key'], JSON_THROW_ON_ERROR), true, true);
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_FINGERPRINT, $this->fingerprintOf($keys), true);
+		// Kits from before this field existed fall back to the default.
+		$delay = (int)($kit['delete_delay_days'] ?? self::DEFAULT_DELETE_DELAY);
+		$this->appConfig->setValueInt(Application::APP_ID, self::KEY_DELETE_DELAY, ($delay >= 1 && $delay <= 365) ? $delay : self::DEFAULT_DELETE_DELAY, true);
+		$this->appConfig->setValueInt(Application::APP_ID, self::KEY_KIT_VERSION, (int)($kit['kit_version'] ?? 1), true);
+		// Having and successfully using a real kit file is stronger proof than the normal
+		// download-and-confirm flow it replaces.
+		$this->confirmRecoveryKit('cli-import');
+	}
+
+	/**
+	 * The master key and the recovery kit code are stored encrypted with Nextcloud's own
+	 * instance secret (ICrypto), not with themselves; the wrapped key is not (it is sealed with
+	 * the admin's passphrase instead), but Nextcloud's own AppConfig additionally encrypts any
+	 * "sensitive" value with the instance secret regardless, underneath whatever we store. So
+	 * changing that secret (occ backup:restore:full merging config.php) would otherwise leave
+	 * all three permanently undecryptable. Call $applySecretChange (which must be the only thing
+	 * that changes the secret) through here instead: all three are decrypted first, then
+	 * re-encrypted under whatever secret is active once $applySecretChange returns.
+	 *
+	 * Not crash-safe: a process kill between the delete and the re-save of one of these keys
+	 * would leave it missing rather than merely stale. Disaster recovery is run once, by hand,
+	 * right after occ maintenance:install; a dedicated two-phase write is not justified yet for
+	 * that narrow a window.
+	 */
+	public function reencryptForSecretRotation(callable $applySecretChange): mixed {
+		$master = $this->appConfig->getValueString(Application::APP_ID, self::KEY_MASTER, '', true);
+		$wrapped = $this->appConfig->getValueString(Application::APP_ID, self::KEY_WRAPPED, '', true);
+		$kitCodeRaw = $this->appConfig->getValueString(Application::APP_ID, self::KEY_KIT_CODE, '', true);
+		$kitCode = $kitCodeRaw !== '' ? json_decode($kitCodeRaw, true, 512, JSON_THROW_ON_ERROR) : null;
+		$masterPlain = $master !== '' ? $this->crypto->decrypt($master) : null;
+		$kitCodePlain = $kitCode !== null && isset($kitCode['code']) ? $this->crypto->decrypt($kitCode['code']) : null;
+
+		$result = $applySecretChange();
+		$this->cached = null; // the master key is about to be re-saved; do not keep the pre-rotation copy
+
+		// Nextcloud's own AppConfig additionally encrypts a "sensitive" value itself (tied to
+		// the same secret, underneath our own encrypt() above); setValueString() on an existing
+		// key reads the old value first to compare, which would try to decrypt it with the new
+		// secret and fail the same way. Delete first so there is nothing to compare against.
+		if ($masterPlain !== null) {
+			$this->appConfig->deleteKey(Application::APP_ID, self::KEY_MASTER);
+			$this->appConfig->setValueString(Application::APP_ID, self::KEY_MASTER, $this->crypto->encrypt($masterPlain), true, true);
+		}
+		if ($wrapped !== '') {
+			// Already plaintext JSON here: getValueString() above transparently undid
+			// AppConfig's own sensitive-value encryption; there is no encrypt() of our own to
+			// redo (wrapping is sealed with the passphrase, not the instance secret).
+			$this->appConfig->deleteKey(Application::APP_ID, self::KEY_WRAPPED);
+			$this->appConfig->setValueString(Application::APP_ID, self::KEY_WRAPPED, $wrapped, true, true);
+		}
+		if ($kitCodePlain !== null) {
+			$kitCode['code'] = $this->crypto->encrypt($kitCodePlain);
+			$this->appConfig->deleteKey(Application::APP_ID, self::KEY_KIT_CODE);
+			$this->appConfig->setValueString(Application::APP_ID, self::KEY_KIT_CODE, json_encode($kitCode, JSON_THROW_ON_ERROR), true, true);
+		}
+		return $result;
+	}
+
 	public function keyRing(): KeyRing {
 		if ($this->cached === null) {
 			$enc = $this->appConfig->getValueString(Application::APP_ID, self::KEY_MASTER, '', true);
@@ -68,9 +162,99 @@ class KeyService {
 		return $this->cached;
 	}
 
+	/** Deletion delay in days, fixed at installation (installations from before this setting get the default once). */
+	public function deleteDelayDays(): int {
+		$days = $this->appConfig->getValueInt(Application::APP_ID, self::KEY_DELETE_DELAY, 0, true);
+		if ($days === 0 && $this->isInitialized()) {
+			$days = self::DEFAULT_DELETE_DELAY;
+			$this->appConfig->setValueInt(Application::APP_ID, self::KEY_DELETE_DELAY, $days, true);
+		}
+		return $days;
+	}
+
+	public const MAX_SLOTS = 3;
+
+	/** @return list<array{slot:int, label:string, created:int}> passphrase slots, without key material */
+	public function slots(): array {
+		return array_map(fn ($s) => ['slot' => $s['slot'], 'label' => $s['label'], 'created' => $s['created']], $this->wrappedKey()['slots']);
+	}
+
+	/** Add a passphrase slot (e.g. one per person who must be able to restore). Returns the slot number. */
+	public function addSlot(#[\SensitiveParameter] string $passphrase, string $label): int {
+		self::checkPassphrase($passphrase);
+		$slots = $this->wrappedKey()['slots'];
+		if (count($slots) >= self::MAX_SLOTS) {
+			throw new \InvalidArgumentException('At most ' . self::MAX_SLOTS . ' passphrase slots');
+		}
+		$used = array_column($slots, 'slot');
+		$n = min(array_diff(range(1, self::MAX_SLOTS), $used));
+		$slots[] = ['slot' => $n, 'label' => self::cleanLabel($label), 'created' => time(), 'key' => $this->keyRing()->wrap($passphrase)];
+		usort($slots, fn ($a, $b) => $a['slot'] <=> $b['slot']);
+		$this->saveSlots($slots);
+		return $n;
+	}
+
+	/** New passphrase for a slot (e.g. its holder left). The master key and all backups stay the same. */
+	public function replaceSlot(int $slot, #[\SensitiveParameter] string $passphrase, ?string $label = null): void {
+		self::checkPassphrase($passphrase);
+		$slots = $this->wrappedKey()['slots'];
+		$found = false;
+		foreach ($slots as &$s) {
+			if ($s['slot'] === $slot) {
+				$s['key'] = $this->keyRing()->wrap($passphrase);
+				$s['created'] = time();
+				if ($label !== null) {
+					$s['label'] = self::cleanLabel($label);
+				}
+				$found = true;
+			}
+		}
+		unset($s);
+		if (!$found) {
+			throw new \InvalidArgumentException("There is no slot $slot");
+		}
+		$this->saveSlots($slots);
+	}
+
+	public function removeSlot(int $slot): void {
+		$slots = array_values(array_filter($this->wrappedKey()['slots'], fn ($s) => $s['slot'] !== $slot));
+		if (count($slots) === count($this->wrappedKey()['slots'])) {
+			throw new \InvalidArgumentException("There is no slot $slot");
+		}
+		if ($slots === []) {
+			throw new \InvalidArgumentException('The last passphrase slot cannot be removed');
+		}
+		$this->saveSlots($slots);
+	}
+
+	/** Every change to the slots asks for a new recovery kit (and its confirmation). */
+	private function saveSlots(array $slots): void {
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_WRAPPED, json_encode(['slots' => $slots], JSON_THROW_ON_ERROR), true, true);
+		$this->appConfig->setValueInt(Application::APP_ID, self::KEY_KIT_VERSION, $this->kitVersion() + 1, true);
+	}
+
+	private static function checkPassphrase(string $passphrase): void {
+		if (strlen($passphrase) < 12) {
+			throw new \InvalidArgumentException('The passphrase must be at least 12 characters');
+		}
+	}
+
+	private static function cleanLabel(string $label): string {
+		$label = trim(preg_replace('/[\x00-\x1f]/', '', $label) ?? '');
+		return mb_substr($label === '' ? 'Slot' : $label, 0, 64);
+	}
+
+	public function kitVersion(): int {
+		return $this->appConfig->getValueInt(Application::APP_ID, self::KEY_KIT_VERSION, 1, true);
+	}
+
 	/** Passphrase-wrapped copy of the master key (for repository configs and the recovery kit). */
 	public function wrappedKey(): array {
-		return json_decode($this->appConfig->getValueString(Application::APP_ID, self::KEY_WRAPPED, '{}', true), true, 512, JSON_THROW_ON_ERROR);
+		$data = json_decode($this->appConfig->getValueString(Application::APP_ID, self::KEY_WRAPPED, '{}', true), true, 512, JSON_THROW_ON_ERROR);
+		if (!isset($data['slots'])) {
+			$data = ['slots' => $data === [] ? [] : [['slot' => 1, 'label' => 'Slot 1', 'created' => 0, 'key' => $data]]];
+		}
+		return $data;
 	}
 
 	/** Short identifier of the key, shown in the UI and the kit (not secret). */
@@ -78,29 +262,75 @@ class KeyService {
 		return $this->appConfig->getValueString(Application::APP_ID, self::KEY_FINGERPRINT, '', true);
 	}
 
-	/** @return array{version:int, app:string, fingerprint:string, created:string, wrapped_key:array, instructions:string} */
+	/** @return array{version:int, app:string, fingerprint:string, kit_version:int, delete_delay_days:int, confirmation_code:string, created:string, wrapped_key:array, slots:list<array{slot:int, label:string, created:int}>, instructions:string} */
 	public function recoveryKit(): array {
 		return [
 			'version' => 1,
 			'app' => 'NG Backup',
 			'fingerprint' => $this->fingerprint(),
+			'kit_version' => $this->kitVersion(),
+			'delete_delay_days' => $this->deleteDelayDays(),
+			'confirmation_code' => $this->kitCode(),
 			'created' => gmdate('c'),
 			'wrapped_key' => $this->wrappedKey(),
-			'instructions' => 'Keep this file and your passphrase safe, outside this server. To restore on a new server: install NG Backup, '
-				. 'add the backup location, and enter this kit with your passphrase. Without both, the backups cannot be decrypted.',
+			'slots' => $this->slots(),
+			'instructions' => 'Keep this file safe, outside this server. Any one of the passphrases of the slots listed here opens it. '
+				. 'To restore on a new server: install NG Backup, add the backup location and enter this kit with one passphrase. '
+				. 'Without the kit (or the location) and a passphrase, the backups cannot be decrypted.',
 		];
 	}
 
+	/**
+	 * Short code printed in the current kit file. Typing it back when confirming proves the
+	 * admin actually has the downloaded kit. A new code per kit version; the server only keeps
+	 * its own copy encrypted with the instance secret.
+	 */
+	private function kitCode(): string {
+		$stored = json_decode($this->appConfig->getValueString(Application::APP_ID, self::KEY_KIT_CODE, '{}', true), true) ?: [];
+		if (($stored['version'] ?? 0) === $this->kitVersion() && isset($stored['code'])) {
+			return $this->crypto->decrypt($stored['code']);
+		}
+		$alphabet = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'; // no 0/O, 1/I
+		$code = '';
+		for ($i = 0; $i < 8; $i++) {
+			$code .= $alphabet[random_int(0, strlen($alphabet) - 1)];
+		}
+		$code = substr($code, 0, 4) . '-' . substr($code, 4);
+		$this->appConfig->setValueString(Application::APP_ID, self::KEY_KIT_CODE,
+			json_encode(['version' => $this->kitVersion(), 'code' => $this->crypto->encrypt($code)], JSON_THROW_ON_ERROR), true, true);
+		return $code;
+	}
+
+	public function checkKitCode(string $code): bool {
+		$stored = json_decode($this->appConfig->getValueString(Application::APP_ID, self::KEY_KIT_CODE, '{}', true), true) ?: [];
+		if (($stored['version'] ?? 0) !== $this->kitVersion() || !isset($stored['code'])) {
+			return false; // no kit downloaded for this version yet
+		}
+		$normalise = static fn (string $c) => strtoupper(preg_replace('/[^A-Za-z0-9]/', '', $c) ?? '');
+		return hash_equals($normalise($this->crypto->decrypt($stored['code'])), $normalise($code));
+	}
+
 	public function confirmRecoveryKit(string $uid): void {
 		$this->appConfig->setValueString(Application::APP_ID, self::KEY_CONFIRMED,
-			json_encode(['uid' => $uid, 'time' => time(), 'fingerprint' => $this->fingerprint()], JSON_THROW_ON_ERROR), true);
+			json_encode(['uid' => $uid, 'time' => time(), 'fingerprint' => $this->fingerprint(), 'kit_version' => $this->kitVersion()], JSON_THROW_ON_ERROR), true);
 	}
 
-	/** Confirmation for the current key, or null. */
+	/**
+	 * Whether a recovery kit for this key was ever confirmed (any passphrase version). Backups
+	 * keep running after a passphrase change, so changing it cannot be used to stop backups; the
+	 * missing re-confirmation is reported as an error in the admin overview instead.
+	 */
+	public function everConfirmed(): bool {
+		$raw = $this->appConfig->getValueString(Application::APP_ID, self::KEY_CONFIRMED, '', true);
+		$data = $raw === '' ? null : json_decode($raw, true);
+		return $data !== null && ($data['fingerprint'] ?? '') === $this->fingerprint();
+	}
+
+	/** Confirmation for the current key and kit version, or null. */
 	public function recoveryKitConfirmation(): ?array {
 		$raw = $this->appConfig->getValueString(Application::APP_ID, self::KEY_CONFIRMED, '', true);
 		$data = $raw === '' ? null : json_decode($raw, true);
-		return ($data !== null && ($data['fingerprint'] ?? '') === $this->fingerprint()) ? $data : null;
+		return ($data !== null && ($data['fingerprint'] ?? '') === $this->fingerprint() && ($data['kit_version'] ?? 1) === $this->kitVersion()) ? $data : null;
 	}
 
 	private function fingerprintOf(KeyRing $keys): string {

lib/Service/KeySlotService.php

@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+/**
+ * Passphrase slots (like LUKS): up to three passphrases, each opening the same master key, so
+ * that one person leaving or dying does not lock the company out of its backups. Every change
+ * is written to all locations and announced to all administrators; a new recovery kit must be
+ * downloaded and confirmed afterwards (backups keep running meanwhile).
+ */
+final class KeySlotService {
+	public function __construct(
+		private KeyService $keys,
+		private TargetService $targets,
+		private AlertService $alerts,
+	) {
+	}
+
+	public function add(#[\SensitiveParameter] string $passphrase, string $label): int {
+		$slot = $this->keys->addSlot($passphrase, $label);
+		$this->apply('slot_added', $slot);
+		return $slot;
+	}
+
+	public function replace(int $slot, #[\SensitiveParameter] string $passphrase, ?string $label = null): void {
+		$this->keys->replaceSlot($slot, $passphrase, $label);
+		$this->apply('slot_replaced', $slot);
+	}
+
+	public function remove(int $slot): void {
+		$this->keys->removeSlot($slot);
+		$this->apply('slot_removed', $slot);
+	}
+
+	private function apply(string $event, int $slot): void {
+		$wrapped = $this->keys->wrappedKey();
+		$failed = [];
+		foreach ($this->targets->list() as $t) {
+			try {
+				$this->targets->repository($t)->updateWrappedKey($wrapped);
+			} catch (\Throwable $e) {
+				$failed[] = $t->getName();
+			}
+		}
+		$label = '';
+		foreach ($this->keys->slots() as $s) {
+			if ($s['slot'] === $slot) {
+				$label = $s['label'];
+			}
+		}
+		$this->alerts->securityEvent($event, ['slot' => (string)$slot, 'label' => $label]);
+		if ($failed !== []) {
+			throw new \RuntimeException('Saved, but these locations could not be updated (they still accept the previous passphrases): ' . implode(', ', $failed));
+		}
+	}
+}

lib/Service/LeaseService.php

@@ -0,0 +1,99 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCP\IDBConnection;
+use OCP\Lock\ILockingProvider;
+use OCP\Lock\LockedException;
+
+/**
+ * Shared/exclusive leases with an expiry, stored in ngb_leases.
+ *
+ * Nextcloud's locks live up to an hour; a PHP process killed while holding one (web cron time
+ * limit, OOM, kill -9) would block a location that long. A lease expires on its own unless its
+ * holder keeps refreshing it. Nextcloud's lock is only held for the few milliseconds in which a
+ * lease is checked and written.
+ */
+final class LeaseService {
+	public const SHARED = 's';
+	public const EXCLUSIVE = 'x';
+
+	public function __construct(
+		private IDBConnection $db,
+		private ILockingProvider $locking,
+	) {
+	}
+
+	/** @return string lease id; throws LockedException when it conflicts with a live lease */
+	public function acquire(string $name, string $mode, int $ttl): string {
+		$guard = 'ng_backup/lease/' . $name;
+		$this->locking->acquireLock($guard, ILockingProvider::LOCK_EXCLUSIVE);
+		try {
+			$now = time();
+			$qb = $this->db->getQueryBuilder();
+			$qb->delete('ngb_leases')
+				->where($qb->expr()->eq('name', $qb->createNamedParameter($name)))
+				->andWhere($qb->expr()->lt('expires_at', $qb->createNamedParameter($now)));
+			$qb->executeStatement();
+
+			$qb = $this->db->getQueryBuilder();
+			$qb->select('mode')->from('ngb_leases')->where($qb->expr()->eq('name', $qb->createNamedParameter($name)));
+			$modes = $qb->executeQuery()->fetchAll(\PDO::FETCH_COLUMN);
+			if ($modes !== [] && ($mode === self::EXCLUSIVE || in_array(self::EXCLUSIVE, $modes, true))) {
+				throw new LockedException($name);
+			}
+			$id = bin2hex(random_bytes(16));
+			$qb = $this->db->getQueryBuilder();
+			$qb->insert('ngb_leases')->values([
+				'id' => $qb->createNamedParameter($id),
+				'name' => $qb->createNamedParameter($name),
+				'mode' => $qb->createNamedParameter($mode),
+				'expires_at' => $qb->createNamedParameter($now + $ttl),
+			]);
+			$qb->executeStatement();
+			return $id;
+		} finally {
+			$this->locking->releaseLock($guard, ILockingProvider::LOCK_EXCLUSIVE);
+		}
+	}
+
+	/** Extend a lease while its holder is still working. */
+	public function refresh(string $id, int $ttl): void {
+		$qb = $this->db->getQueryBuilder();
+		$qb->update('ngb_leases')->set('expires_at', $qb->createNamedParameter(time() + $ttl))
+			->where($qb->expr()->eq('id', $qb->createNamedParameter($id)));
+		$qb->executeStatement();
+	}
+
+	public function release(string $id): void {
+		$qb = $this->db->getQueryBuilder();
+		$qb->delete('ngb_leases')->where($qb->expr()->eq('id', $qb->createNamedParameter($id)));
+		$qb->executeStatement();
+	}
+
+	/** Wraps $refresh so calling it often (per file, per row batch) only touches the database every $seconds. */
+	public static function throttled(callable $refresh, int $seconds = 60): \Closure {
+		$last = time();
+		return static function () use ($refresh, $seconds, &$last): void {
+			if (time() - $last >= $seconds) {
+				$refresh();
+				$last = time();
+			}
+		};
+	}
+
+	/** Run $fn under a lease; $refresh() can be called during long work. */
+	public function with(string $name, string $mode, int $ttl, callable $fn): mixed {
+		$id = $this->acquire($name, $mode, $ttl);
+		try {
+			return $fn(fn () => $this->refresh($id, $ttl));
+		} finally {
+			$this->release($id);
+		}
+	}
+}

lib/Service/PruneService.php

@@ -0,0 +1,240 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCA\NgBackup\AppInfo\Application;
+use OCA\NgBackup\Db\RunMapper;
+use OCA\NgBackup\Db\SnapshotMapper;
+use OCA\NgBackup\Db\Target;
+use OCP\IAppConfig;
+use OCP\Lock\ILockingProvider;
+use OCP\Lock\LockedException;
+
+/**
+ * Applies the retention policy to a location: forgets snapshots the policy does not keep and
+ * prunes data no remaining snapshot uses. Never runs on append-only locations, never while a
+ * backup to the same location is running (the location lock is shared with BackupService).
+ */
+final class PruneService {
+	public function __construct(
+		private TargetService $targets,
+		private RunMapper $runs,
+		private SnapshotMapper $snapshots,
+		private IAppConfig $appConfig,
+		private ILockingProvider $locking,
+		private AlertService $alerts,
+		private KeyService $keys,
+		private LeaseService $leases,
+	) {
+	}
+
+	public function untrash(Target $target, string $snapshotId): void {
+		$lease = $this->lockExclusive($target, 300);
+		try {
+			$this->doUntrash($target, $snapshotId);
+		} finally {
+			$this->leases->release($lease);
+		}
+	}
+
+	/**
+	 * Run $fn under the location's exclusive lock (to create a run atomically with respect to a
+	 * cleanup, which takes the same lock and then refuses while a run exists).
+	 */
+	public function underStartLock(Target $target, callable $fn): mixed {
+		try {
+			return $this->leases->with(self::lockKey($target), LeaseService::EXCLUSIVE, 60, fn () => $fn());
+		} catch (LockedException) {
+			throw new \RuntimeException('A cleanup of ' . $target->getName() . ' is in progress; try again later');
+		}
+	}
+
+	/**
+	 * Exclusive lock on the location, then make sure no run of any kind (backup, restore, export)
+	 * is in progress: their data may not be referenced by a snapshot yet, or is being read.
+	 */
+	private function lockExclusive(Target $target, int $ttl): string {
+		try {
+			$lease = $this->leases->acquire(self::lockKey($target), LeaseService::EXCLUSIVE, $ttl);
+		} catch (LockedException) {
+			throw new \RuntimeException('A backup, restore or cleanup of ' . $target->getName() . ' is in progress; try again later');
+		}
+		if ($this->runs->findRunning($target->getId()) !== []) {
+			$this->leases->release($lease);
+			throw new \RuntimeException('A backup or restore of ' . $target->getName() . ' is running; try again later');
+		}
+		return $lease;
+	}
+
+	private function doUntrash(Target $target, string $snapshotId): void {
+		$repo = $this->targets->repository($target);
+		if (!array_key_exists($snapshotId, $repo->trash())) {
+			throw new \InvalidArgumentException('That snapshot is not in the trash (or was already deleted)');
+		}
+		$repo->untrash($snapshotId);
+		// Put it back in the local snapshot list as well.
+		$meta = $repo->snapshotMeta($snapshotId);
+		$s = new \OCA\NgBackup\Db\Snapshot();
+		$s->setTargetId($target->getId());
+		$s->setSnapshotId($snapshotId);
+		$s->setKind((string)($meta['kind'] ?? 'full'));
+		$s->setLabel(($meta['label'] ?? '') !== '' ? $meta['label'] : null);
+		$s->setCreatedAt((int)strtotime((string)($meta['time'] ?? 'now')));
+		$s->setFiles((int)($meta['stats']['files'] ?? 0));
+		$s->setBytes((int)($meta['stats']['bytes'] ?? 0));
+		try {
+			$this->snapshots->insert($s);
+		} catch (\Throwable) {
+		}
+		$this->alerts->securityEvent('snapshot_untrashed', ['target' => $target->getName(), 'snapshot' => $snapshotId]);
+	}
+
+	public static function lockKey(Target $target): string {
+		return 'ng_backup/target/' . $target->getId();
+	}
+
+	/**
+	 * A separate, short-lived exclusive lock serializing writes to the catalog itself. The
+	 * per-target lock above only keeps readers/writers out while a cleanup runs; it does not
+	 * stop two SHARED holders (e.g. two concurrent per-user backups, or one alongside a full
+	 * backup) from both reading the same catalog generation and racing to write the next one,
+	 * silently dropping whichever's change loses. The full-backup path avoids this today only
+	 * because a Run row makes concurrent runs for the same target mutually exclusive; per-user
+	 * backup/restore has no such row, so it takes this lock around the catalog write itself.
+	 */
+	public static function catalogLockKey(Target $target): string {
+		return self::lockKey($target) . '/catalog';
+	}
+
+	/** How many of each user's own exports (occ backup:user:backup) to keep, newest first. */
+	public function userExportRetention(): int {
+		return $this->appConfig->getValueInt(Application::APP_ID, 'user_export_retention', 3);
+	}
+
+	public function setUserExportRetention(int $keep): void {
+		if ($keep < 1) {
+			throw new \InvalidArgumentException('Keep at least the last export');
+		}
+		$old = $this->userExportRetention();
+		$this->appConfig->setValueInt(Application::APP_ID, 'user_export_retention', $keep);
+		if ($old !== $keep) {
+			$this->alerts->securityEvent('user_export_retention_changed', ['keep' => (string)$keep]);
+		}
+	}
+
+	/**
+	 * Forgets a user's older exports once more than userExportRetention() exist for them,
+	 * newest first; no trash, unlike a full snapshot (occ backup:user:backup is on-demand, not
+	 * yet the primary safety net the deletion delay protects).
+	 *
+	 * @return array{kept: array<string, list<string>>, forgotten: list<string>}
+	 */
+	public function applyUserExports(Target $target, bool $dryRun = false): array {
+		if ($target->getAppendOnly()) {
+			throw new \RuntimeException('Location ' . $target->getName() . ' is append-only: NG Backup does not delete anything there');
+		}
+		$lease = $this->lockExclusive($target, 1800);
+		try {
+			$repo = $this->targets->repository($target);
+			$keep = $this->userExportRetention();
+			$byUser = [];
+			foreach ($repo->listUserExports() as $path) {
+				$uid = explode('/', $path)[1] ?? '';
+				$manifest = json_decode($repo->getObject($path), true, 512, JSON_THROW_ON_ERROR);
+				$byUser[$uid][$path] = (int)strtotime((string)($manifest['time'] ?? '@0'));
+			}
+			$kept = [];
+			$forget = [];
+			foreach ($byUser as $uid => $times) {
+				arsort($times);
+				$i = 0;
+				foreach (array_keys($times) as $path) {
+					if ($i++ < $keep) {
+						$kept[$uid][] = $path;
+					} else {
+						$forget[] = $path;
+					}
+				}
+			}
+			if (!$dryRun) {
+				foreach ($forget as $path) {
+					$repo->forgetUserExport($path);
+				}
+				if ($forget !== []) {
+					$this->alerts->securityEvent('user_exports_forgotten', ['target' => $target->getName(), 'count' => (string)count($forget)], false);
+				}
+			}
+			return ['kept' => $kept, 'forgotten' => $forget];
+		} finally {
+			$this->leases->release($lease);
+		}
+	}
+
+	public function policy(): RetentionPolicy {
+		return RetentionPolicy::fromArray(json_decode($this->appConfig->getValueString(Application::APP_ID, 'retention', '{}'), true) ?: []);
+	}
+
+	public function setPolicy(RetentionPolicy $policy): void {
+		if ($policy->last < 1) {
+			throw new \InvalidArgumentException('Keep at least the last snapshot');
+		}
+		$old = $this->policy()->toArray();
+		$this->appConfig->setValueString(Application::APP_ID, 'retention', json_encode($policy->toArray(), JSON_THROW_ON_ERROR));
+		if ($old !== $policy->toArray()) {
+			$this->alerts->securityEvent('retention_changed', ['policy' => json_encode($policy->toArray())]);
+		}
+	}
+
+	/**
+	 * Snapshots the policy drops go to the trash on the location; trash entries older than the
+	 * deletion delay are purged, and only then is their data freed.
+	 *
+	 * @return array{kept: array<string, list<string>>, forgotten: list<string>, purged: list<string>, prune: array}
+	 */
+	public function apply(Target $target, bool $dryRun = false, bool $scheduled = false): array {
+		if ($target->getAppendOnly()) {
+			throw new \RuntimeException('Location ' . $target->getName() . ' is append-only: NG Backup does not delete anything there');
+		}
+		$lease = $this->lockExclusive($target, 1800);
+		try {
+			$repo = $this->targets->repository($target);
+			$times = [];
+			foreach ($repo->listSnapshots() as $id) {
+				$meta = $repo->snapshotMeta($id);
+				$times[$id] = (int)strtotime((string)($meta['time'] ?? '@0'));
+			}
+			$keep = $this->policy()->keep($times);
+			$forget = array_values(array_diff(array_keys($times), array_keys($keep)));
+			$actor = $scheduled ? 'retention policy' : $this->alerts->actor();
+			$purged = [];
+			if (!$dryRun) {
+				foreach ($forget as $id) {
+					$repo->forget($id, $actor);
+					try {
+						$this->snapshots->delete($this->snapshots->findOne($target->getId(), $id));
+					} catch (\Throwable) {
+					}
+				}
+			}
+			// Also removes leftovers of interrupted runs. A dry run counts the snapshots it would forget as gone.
+			$delay = $this->keys->deleteDelayDays();
+			if (!$dryRun && $forget !== []) {
+				// Scheduled cleanup follows the policy: audit log only, no notification every week.
+				$this->alerts->securityEvent('snapshots_forgotten', ['target' => $target->getName(), 'count' => (string)count($forget),
+					'until' => date('Y-m-d', time() + $delay * 86400)], !$scheduled);
+			}
+			if (!$dryRun) {
+				$purged = $repo->purgeTrash($delay * 86400);
+			}
+			$prune = $repo->prune($dryRun);
+			return ['kept' => $keep, 'forgotten' => $forget, 'purged' => $purged, 'prune' => $prune];
+		} finally {
+			$this->leases->release($lease);
+		}
+	}
+}

lib/Service/RestoreFullService.php

@@ -0,0 +1,228 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCA\NgBackup\Db\DbDumper;
+use OCA\NgBackup\Db\Target;
+use OCP\App\IAppManager;
+use OCP\IConfig;
+use OCP\IDBConnection;
+use OCP\Lock\LockedException;
+
+/**
+ * Disaster recovery on a fresh Nextcloud installation (same major version): replace the
+ * database, restore the data directory and merge the backed-up config.php, see PLAN.md 3.7.
+ *
+ * Deliberately NOT handled yet (phase 3): restoring in place over a live, already-used
+ * installation. The admin is expected to run this once, right after occ maintenance:install and
+ * occ backup:key:import/backup:target:add, before anyone else touches the instance.
+ */
+final class RestoreFullService {
+	/**
+	 * Config keys that must keep pointing at THIS installation's actual, already-working
+	 * database and data directory (set by occ maintenance:install), never at the old server's.
+	 */
+	private const CONNECTION_KEYS = [
+		'dbtype', 'dbhost', 'dbport', 'dbname', 'dbuser', 'dbpassword', 'dbpersistent',
+		'dbtableprefix', 'dbdriveroptions', 'datadirectory',
+	];
+
+	public function __construct(
+		private TargetService $targets,
+		private RestoreService $restore,
+		private LeaseService $leases,
+		private IConfig $config,
+		private IDBConnection $db,
+		private IAppManager $appManager,
+		private KeyService $keys,
+	) {
+	}
+
+	/**
+	 * Whether this installation can receive $snapshotId: same Nextcloud major version, and every
+	 * app that was enabled at backup time already installed here (its tables must exist before
+	 * the database restore can write into them).
+	 *
+	 * @return array{ok:bool, currentMajor:string, snapshotMajor:string, missingApps:list<string>}
+	 */
+	public function checkCompatibility(Target $target, string $snapshotId): array {
+		$meta = $this->targets->repository($target)->snapshotMeta($snapshotId);
+		$currentMajor = explode('.', $this->config->getSystemValueString('version'))[0];
+		$snapshotMajor = explode('.', (string)($meta['nextcloud'] ?? ''))[0];
+		$enabled = array_flip($this->appManager->getEnabledApps());
+		$missingApps = array_values(array_diff(array_keys($meta['apps'] ?? []), array_keys($enabled)));
+		return [
+			'ok' => $currentMajor === $snapshotMajor && $missingApps === [],
+			'currentMajor' => $currentMajor,
+			'snapshotMajor' => $snapshotMajor,
+			'missingApps' => $missingApps,
+		];
+	}
+
+	/** @return array{dbReport:array, dataFiles:int, configKeys:int, dbConsistent:bool} */
+	public function restoreFull(Target $target, string $snapshotId): array {
+		$check = $this->checkCompatibility($target, $snapshotId);
+		if (!$check['ok']) {
+			throw new \RuntimeException($this->describeBlockers($check));
+		}
+		return $this->withSharedLock($target, function (callable $refresh) use ($target, $snapshotId) {
+			$beat = LeaseService::throttled($refresh);
+			$repo = $this->targets->repository($target);
+			$meta = $repo->snapshotMeta($snapshotId);
+
+			$dbReport = null;
+			$manifest = [];
+			if (isset($meta['db'])) {
+				$manifest = json_decode($repo->getObject($meta['db']), true, 512, JSON_THROW_ON_ERROR);
+				$prefix = $this->config->getSystemValueString('dbtableprefix', 'oc_');
+				// ng_backup's own tables (and its own rows in the shared appconfig table) must
+				// survive this restore untouched: they describe the backup/key/target that is
+				// actively performing it right now, on THIS installation, not the one that was
+				// backed up. Overwriting them mid-restore would pull the rug from under it.
+				foreach (array_keys($manifest['tables']) as $table) {
+					/** @var string $table */
+					if (str_starts_with($table, $prefix . 'ngb_')) {
+						unset($manifest['tables'][$table]);
+					}
+				}
+				// Sequences are keyed separately from tables; excluding a table does not exclude
+				// its sequence, which would otherwise rewind a retained ngb_* table's sequence
+				// below its current ids (PostgreSQL only -- see DbDumper::restoreSequences()).
+				foreach (array_keys($manifest['sequences'] ?? []) as $seq) {
+					/** @var string $seq */
+					if (str_starts_with((string)($manifest['sequences'][$seq]['table'] ?? ''), $prefix . 'ngb_')) {
+						unset($manifest['sequences'][$seq]);
+					}
+				}
+				$ownAppConfig = $this->preserveOwnAppConfig();
+				$dumper = new DbDumper($this->db->getInner(), $prefix);
+				try {
+					$dumper->restore($repo, $manifest, $dbReport, $beat);
+				} finally {
+					$this->restoreOwnAppConfig($ownAppConfig);
+				}
+			}
+
+			// Read (but do not yet apply) the backed-up config.php before touching the data
+			// directory: once applied, 'secret' may differ from what ng_backup's own Target
+			// options were encrypted with (see restoreFull()'s docblock), and every further
+			// repository access through $this->targets would fail to decrypt them.
+			/** @var array<string, mixed> $backupConfig */
+			$backupConfig = $this->fetchBackupConfig($target, $snapshotId);
+
+			$dataDir = rtrim($this->config->getSystemValueString('datadirectory'), '/');
+			$dataFiles = $this->restore->restoreToDirectory($target, $snapshotId, 'data', $dataDir, stripPrefix: true, heartbeat: $beat);
+
+			// Last step: nothing after this may need $this->targets->repository($target) again.
+			if ($backupConfig !== []) {
+				$this->targets->reencryptOptionsAround(
+					fn (): mixed => $this->keys->reencryptForSecretRotation(fn (): mixed => $this->config->setSystemValues($backupConfig)),
+				);
+			}
+
+			return ['dbReport' => $dbReport ?? ['skipped' => [], 'restored' => []], 'dataFiles' => $dataFiles, 'configKeys' => count($backupConfig),
+				'dbConsistent' => (bool)($manifest['consistent'] ?? true)];
+		});
+	}
+
+	/** @return array<string, mixed> config.php's $CONFIG from the backup, minus the connection keys */
+	private function fetchBackupConfig(Target $target, string $snapshotId): array {
+		$tmp = sys_get_temp_dir() . '/ngb-restore-config-' . bin2hex(random_bytes(6));
+		try {
+			$this->restore->restoreToDirectory($target, $snapshotId, 'config', $tmp, stripPrefix: true);
+			$path = $tmp . '/config.php';
+			if (!is_file($path)) {
+				return []; // nothing to merge; the live config.php stays as occ maintenance:install made it
+			}
+			$backupConfig = (static function () use ($path): array {
+				$CONFIG = [];
+				include $path;
+				return $CONFIG;
+			})();
+			foreach (self::CONNECTION_KEYS as $key) {
+				unset($backupConfig[$key]);
+			}
+			return $backupConfig;
+		} finally {
+			$this->rmrf($tmp);
+		}
+	}
+
+	/** @return list<array<string, mixed>> raw appconfig rows (appid, configkey, configvalue, type, lazy) */
+	private function preserveOwnAppConfig(): array {
+		$qb = $this->db->getQueryBuilder();
+		$qb->select('*')->from('appconfig')
+			->where($qb->expr()->eq('appid', $qb->createNamedParameter(\OCA\NgBackup\AppInfo\Application::APP_ID)));
+		/** @var list<array<string, mixed>> */
+		return $qb->executeQuery()->fetchAll();
+	}
+
+	/**
+	 * @param list<array<string, mixed>> $rows raw appconfig rows, as returned by preserveOwnAppConfig()
+	 *
+	 * Runs in its own transaction (DbDumper::restore() already committed its own by the time
+	 * this is called): not a full guarantee against a crash spanning both, but means this step
+	 * itself cannot leave ng_backup's appconfig rows half deleted, half reinserted.
+	 */
+	private function restoreOwnAppConfig(array $rows): void {
+		$this->db->beginTransaction();
+		try {
+			$qb = $this->db->getQueryBuilder();
+			$qb->delete('appconfig')
+				->where($qb->expr()->eq('appid', $qb->createNamedParameter(\OCA\NgBackup\AppInfo\Application::APP_ID)));
+			$qb->executeStatement();
+			foreach ($rows as $row) {
+				$ins = $this->db->getQueryBuilder();
+				$ins->insert('appconfig')->values([
+					'appid' => $ins->createNamedParameter($row['appid']),
+					'configkey' => $ins->createNamedParameter($row['configkey']),
+					'configvalue' => $ins->createNamedParameter($row['configvalue']),
+					'type' => $ins->createNamedParameter($row['type'], \OCP\DB\QueryBuilder\IQueryBuilder::PARAM_INT),
+					'lazy' => $ins->createNamedParameter($row['lazy'], \OCP\DB\QueryBuilder\IQueryBuilder::PARAM_INT),
+				]);
+				$ins->executeStatement();
+			}
+			$this->db->commit();
+		} catch (\Throwable $e) {
+			$this->db->rollBack();
+			throw $e;
+		}
+	}
+
+	private function rmrf(string $dir): void {
+		if (!is_dir($dir)) {
+			return;
+		}
+		foreach (new \RecursiveIteratorIterator(new \RecursiveDirectoryIterator($dir, \FilesystemIterator::SKIP_DOTS), \RecursiveIteratorIterator::CHILD_FIRST) as $f) {
+			$f->isDir() ? rmdir($f->getPathname()) : unlink($f->getPathname());
+		}
+		rmdir($dir);
+	}
+
+	private function describeBlockers(array $check): string {
+		$parts = [];
+		if ($check['currentMajor'] !== $check['snapshotMajor']) {
+			$parts[] = "this installation is Nextcloud {$check['currentMajor']}, the backup is from {$check['snapshotMajor']} (same major version required)";
+		}
+		if ($check['missingApps'] !== []) {
+			$parts[] = 'install these apps first (their tables must exist before the database restore can use them): '
+				. implode(', ', array_map(fn (string $a) => "occ app:install $a", $check['missingApps']));
+		}
+		return implode('; ', $parts);
+	}
+
+	private function withSharedLock(Target $target, callable $fn): mixed {
+		try {
+			// Refreshed during the database and data restore (per row batch, per blob), so a
+			// cleanup cannot take over the location while a long restore is still reading it.
+			return $this->leases->with(PruneService::lockKey($target), LeaseService::SHARED, 7200, $fn);
+		} catch (LockedException) {
+			throw new \RuntimeException('A cleanup of ' . $target->getName() . ' is in progress; try again later');
+		}
+	}
+}

lib/Service/RestoreService.php

@@ -28,7 +28,7 @@ use OCP\Files\NotFoundException;
  *  - merge:   into the original place, existing files are overwritten (old content kept as a version)
  *  - replace: like merge, and files that are not in the snapshot are moved to the trash
  */
-class RestoreService {
+final class RestoreService {
 	public const MODE_NEW_FOLDER = 'new-folder';
 	public const MODE_MERGE = 'merge';
 	public const MODE_REPLACE = 'replace';
@@ -36,9 +36,19 @@ class RestoreService {
 	public function __construct(
 		private TargetService $targets,
 		private IRootFolder $root,
+		private LeaseService $leases,
 	) {
 	}
 
+	/** Shared lock on the location while restoring: a cleanup (exclusive) must not delete what is being read. */
+	private function withSharedLock(Target $target, callable $fn, int $ttl = 600): mixed {
+		try {
+			return $this->leases->with(PruneService::lockKey($target), LeaseService::SHARED, $ttl, $fn);
+		} catch (\OCP\Lock\LockedException) {
+			throw new \RuntimeException('A cleanup of ' . $target->getName() . ' is running; try again later');
+		}
+	}
+
 	/**
 	 * Direct children (files and folders) of a path in a snapshot.
 	 *
@@ -72,7 +82,24 @@ class RestoreService {
 	 * @return array{restored:int, trashed:int, target:string}
 	 */
 	public function restoreUserFiles(Target $target, string $snapshotId, string $logicalPath, string $mode = self::MODE_NEW_FOLDER, ?callable $progress = null): array {
-		if (!preg_match('#^data/([^/]+)/files(?:/(.*))?$#', trim($logicalPath, '/'), $m)) {
+		return $this->withSharedLock($target, function (callable $refresh) use ($target, $snapshotId, $logicalPath, $mode, $progress) {
+			$last = time();
+			// Keep the lease alive while files are being written.
+			$beat = function (int $done, int $total, string $name) use ($refresh, $progress, &$last): void {
+				if (time() - $last >= 60) {
+					$refresh();
+					$last = time();
+				}
+				if ($progress !== null) {
+					$progress($done, $total, $name);
+				}
+			};
+			return $this->doRestoreUserFiles($target, $snapshotId, $logicalPath, $mode, $beat);
+		});
+	}
+
+	private function doRestoreUserFiles(Target $target, string $snapshotId, string $logicalPath, string $mode, ?callable $progress): array {
+		if (!Repository::isSafePath($logicalPath) || !preg_match('#^data/([^/]+)/files(?:/(.*))?$#', $logicalPath, $m)) {
 			throw new \InvalidArgumentException('Expected a path like data/<user>/files/<folder or file>');
 		}
 		[$uid, $rel] = [$m[1], trim($m[2] ?? '', '/')];
@@ -122,12 +149,30 @@ class RestoreService {
 		return ['restored' => $restored, 'trashed' => $trashed, 'target' => $uid . ':' . $userFolder->getRelativePath($dest->getPath())];
 	}
 
-	/** Raw restore of any snapshot path to a local directory (administrators, disaster recovery). */
-	public function restoreToDirectory(Target $target, string $snapshotId, string $prefix, string $directory): int {
+	/**
+	 * Raw restore of any snapshot path to a local directory (administrators, disaster recovery).
+	 *
+	 * @param bool $stripPrefix write into $directory itself instead of $directory/$prefix (see
+	 *             Repository::restore()); used to restore "data/" or "config/" straight into the
+	 *             real data/config directory for occ backup:restore:full.
+	 */
+	public function restoreToDirectory(Target $target, string $snapshotId, string $prefix, string $directory, bool $stripPrefix = false, ?callable $heartbeat = null): int {
+		if ($prefix !== '' && !Repository::isSafePath($prefix)) {
+			throw new \InvalidArgumentException('Invalid path: ' . $prefix);
+		}
 		if (!is_dir($directory) && !mkdir($directory, 0750, true) && !is_dir($directory)) {
 			throw new \RuntimeException("Cannot create $directory");
 		}
-		return $this->targets->repository($target)->restore($snapshotId, $directory, trim($prefix, '/') === '' ? '' : trim($prefix, '/') . '/');
+		return $this->withSharedLock($target, function (callable $refresh) use ($target, $snapshotId, $prefix, $directory, $stripPrefix, $heartbeat): int {
+			$own = LeaseService::throttled($refresh);
+			$beat = static function () use ($own, $heartbeat): void {
+				$own();
+				if ($heartbeat !== null) {
+					$heartbeat();
+				}
+			};
+			return $this->targets->repository($target)->restore($snapshotId, $directory, trim($prefix, '/') === '' ? '' : trim($prefix, '/') . '/', $stripPrefix, $beat);
+		}, 3600);
 	}
 
 	private function writeFile(Repository $repo, Folder $dest, string $relPath, array $entry): void {

lib/Service/RetentionPolicy.php

@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+/**
+ * Which snapshots to keep: the newest $last, plus the newest snapshot of each of the most recent
+ * $daily days, $weekly ISO weeks and $monthly months that have a snapshot (like restic/borg).
+ */
+final class RetentionPolicy {
+	public function __construct(
+		public readonly int $last = 3,
+		public readonly int $daily = 7,
+		public readonly int $weekly = 4,
+		public readonly int $monthly = 6,
+	) {
+	}
+
+	public static function fromArray(array $a): self {
+		return new self((int)($a['last'] ?? 3), (int)($a['daily'] ?? 7), (int)($a['weekly'] ?? 4), (int)($a['monthly'] ?? 6));
+	}
+
+	public function toArray(): array {
+		return ['last' => $this->last, 'daily' => $this->daily, 'weekly' => $this->weekly, 'monthly' => $this->monthly];
+	}
+
+	/**
+	 * @param array<string, int> $snapshots id => unix time
+	 * @return array<string, list<string>> id => reasons it is kept (ids not in the result are removed)
+	 */
+	public function keep(array $snapshots): array {
+		arsort($snapshots);
+		$keep = [];
+		$i = 0;
+		foreach ($snapshots as $id => $time) {
+			if ($i++ < $this->last) {
+				$keep[$id][] = 'last';
+			}
+		}
+		foreach (['daily' => 'Y-m-d', 'weekly' => 'o-W', 'monthly' => 'Y-m'] as $kind => $format) {
+			$seen = [];
+			foreach ($snapshots as $id => $time) {
+				$bucket = date($format, $time);
+				if (isset($seen[$bucket])) {
+					continue;
+				}
+				if (count($seen) >= $this->$kind) {
+					break;
+				}
+				$seen[$bucket] = true;
+				$keep[$id][] = $kind;
+			}
+		}
+		return $keep;
+	}
+}

lib/Service/TargetService.php

@@ -10,10 +10,13 @@ namespace OCA\NgBackup\Service;
 use OCA\NgBackup\Backend\ExternalStorageFactory;
 use OCA\NgBackup\Backend\IBackend;
 use OCA\NgBackup\Backend\StorageBackend;
+use OCA\NgBackup\Db\Snapshot;
+use OCA\NgBackup\Db\SnapshotMapper;
 use OCA\NgBackup\Db\Target;
 use OCA\NgBackup\Db\TargetMapper;
 use OCA\NgBackup\Repository\Repository;
 use OCP\App\IAppManager;
+use OCP\AppFramework\Db\DoesNotExistException;
 use OCP\Security\ICrypto;
 use OCP\Server;
 
@@ -22,13 +25,15 @@ use OCP\Server;
  * object is built only while it is used; nothing is mounted. files_external is loaded for its
  * classes but its enabled/disabled state is left as the admin set it.
  */
-class TargetService {
+final class TargetService {
 	public function __construct(
 		private TargetMapper $mapper,
 		private KeyService $keys,
 		private ICrypto $crypto,
 		private IAppManager $appManager,
 		private \OCA\NgBackup\Db\DbIndexCache $indexCache,
+		private \OCA\NgBackup\Db\AppConfigCatalogAnchor $anchor,
+		private SnapshotMapper $snapshots,
 	) {
 	}
 
@@ -48,6 +53,12 @@ class TargetService {
 		if (!preg_match('/^[A-Za-z0-9][A-Za-z0-9 _.-]{0,63}$/', $name)) {
 			throw new \InvalidArgumentException('Name: letters, digits, space, _ . - (max 64)');
 		}
+		// Without the native extension files_external falls back to the smbclient binary, which
+		// registers fine but cannot seek: the first backup then fails with "Seek failed". Refuse
+		// up front instead of letting the admin find out from a failed run.
+		if ($backend === 'smb' && !extension_loaded('smbclient')) {
+			throw new \InvalidArgumentException('The SMB backend needs the PHP smbclient extension (pecl install smbclient); the smbclient binary alone cannot seek and every backup would fail');
+		}
 		try {
 			$this->mapper->findByName($name);
 			throw new \InvalidArgumentException("A target named '$name' already exists");
@@ -56,10 +67,10 @@ class TargetService {
 		$keys = $this->keys->keyRing();
 		$storageBackend = $this->buildBackend($backend, $auth, $options, $basePath);
 		if ($storageBackend->exists('config')) {
-			$repo = Repository::openWithKey($storageBackend, $keys);
+			$repo = Repository::openWithKey($storageBackend, $keys, $this->indexCache, $this->anchor);
 			$created = false;
 		} else {
-			$repo = Repository::initWithKey($storageBackend, $keys, $this->keys->wrappedKey());
+			$repo = Repository::initWithKey($storageBackend, $keys, $this->keys->wrappedKey(), $this->anchor);
 			$created = true;
 		}
 
@@ -77,7 +88,62 @@ class TargetService {
 		$target->setBasePath(trim($basePath, '/'));
 		$target->setRepositoryId($repo->id());
 		$target->setCreatedAt(time());
-		return ['target' => $this->mapper->insert($target), 'created' => $created];
+		$target = $this->mapper->insert($target);
+		if (!$created) {
+			// Disaster recovery: occ backup:list reads this local cache, not the repository
+			// directly, so a snapshot made by another installation must be backfilled here too.
+			$this->adoptSnapshots($target, $repo);
+		}
+		return ['target' => $target, 'created' => $created];
+	}
+
+	/**
+	 * A target's options are encrypted with Nextcloud's own instance secret (ICrypto), not
+	 * ng_backup's key, so changing that secret (occ backup:restore:full merging config.php)
+	 * would otherwise leave every target permanently undecryptable. Call $applySecretChange
+	 * (which must be the only thing that changes the secret) through here instead: every
+	 * target's options are decrypted first, then re-encrypted under whatever secret is active
+	 * once $applySecretChange returns.
+	 */
+	public function reencryptOptionsAround(callable $applySecretChange): mixed {
+		$plain = [];
+		foreach ($this->mapper->findAll() as $target) {
+			$plain[$target->getId()] = $this->options($target);
+		}
+		$result = $applySecretChange();
+		foreach ($this->mapper->findAll() as $target) {
+			if (!isset($plain[$target->getId()])) {
+				continue; // added by $applySecretChange itself; nothing to re-encrypt
+			}
+			$target->setOptions($this->crypto->encrypt(json_encode($plain[$target->getId()], JSON_THROW_ON_ERROR)));
+			$this->mapper->update($target);
+		}
+		return $result;
+	}
+
+	private function adoptSnapshots(Target $target, Repository $repo): void {
+		foreach ($repo->listSnapshots() as $snapshotId) {
+			try {
+				$this->snapshots->findOne($target->getId(), $snapshotId);
+				continue; // already known locally
+			} catch (DoesNotExistException) {
+			}
+			// One unreadable/corrupt snapshot must not stop the rest of the location's
+			// snapshots from being backfilled, nor abort adding the target itself.
+			try {
+				$meta = $repo->snapshotMeta($snapshotId);
+				$s = new Snapshot();
+				$s->setTargetId($target->getId());
+				$s->setSnapshotId($snapshotId);
+				$s->setKind((string)($meta['kind'] ?? 'full'));
+				$s->setLabel(($meta['label'] ?? '') !== '' ? $meta['label'] : null);
+				$s->setCreatedAt((int)strtotime((string)($meta['time'] ?? 'now')));
+				$s->setFiles((int)($meta['stats']['files'] ?? 0));
+				$s->setBytes((int)($meta['stats']['bytes'] ?? 0));
+				$this->snapshots->insert($s);
+			} catch (\Throwable) {
+			}
+		}
 	}
 
 	/** @return list<Target> */
@@ -86,7 +152,22 @@ class TargetService {
 	}
 
 	public function get(string $nameOrId): Target {
-		return ctype_digit($nameOrId) ? $this->mapper->find((int)$nameOrId) : $this->mapper->findByName($nameOrId);
+		try {
+			return ctype_digit($nameOrId) ? $this->mapper->find((int)$nameOrId) : $this->mapper->findByName($nameOrId);
+		} catch (DoesNotExistException) {
+			throw new \InvalidArgumentException("No such location: $nameOrId");
+		}
+	}
+
+	/** Size limit for the data stored on this location (null = none). */
+	public function setMaxBytes(Target $target, ?int $maxBytes): Target {
+		$target->setMaxBytes($maxBytes);
+		return $this->mapper->update($target);
+	}
+
+	public function setAppendOnly(Target $target, bool $appendOnly): Target {
+		$target->setAppendOnly($appendOnly);
+		return $this->mapper->update($target);
 	}
 
 	/** Remove the target from NG Backup. The backups on the target itself are not touched. */
@@ -99,10 +180,11 @@ class TargetService {
 	}
 
 	public function repository(Target $target): Repository {
-		$repo = Repository::openWithKey($this->backend($target), $this->keys->keyRing(), $this->indexCache);
+		$repo = Repository::openWithKey($this->backend($target), $this->keys->keyRing(), $this->indexCache, $this->anchor);
 		if ($target->getRepositoryId() !== null && $repo->id() !== $target->getRepositoryId()) {
 			throw new \RuntimeException('The target now contains a different repository than when it was added');
 		}
+		$repo->setMaxBytes($target->getMaxBytes());
 		return $repo;
 	}
 
@@ -115,11 +197,33 @@ class TargetService {
 		return new StorageBackend($this->factory()->create($backend, $auth, $options), $basePath);
 	}
 
+	private ?ExternalStorageFactory $factory = null;
+
+	/**
+	 * files_external's connection code, without changing the app's state:
+	 * - enabled: it is booted by Nextcloud; use its own BackendService;
+	 * - disabled: do NOT boot it (booting registers its mount provider and listeners, which use
+	 *   its database tables; on installations where it was never enabled those do not exist).
+	 *   Only its classes are loaded, and a private BackendService gets its backends and auth
+	 *   mechanisms from its Application class.
+	 */
 	private function factory(): ExternalStorageFactory {
-		// Load files_external's classes without enabling the app (its state stays as the admin set it).
-		if (!class_exists(\OCA\Files_External\Service\BackendService::class)) {
-			$this->appManager->loadApp('files_external');
+		if ($this->factory !== null) {
+			return $this->factory;
 		}
-		return new ExternalStorageFactory(Server::get(\OCA\Files_External\Service\BackendService::class));
+		if ($this->appManager->isEnabledForAnyone('files_external')) {
+			$this->appManager->loadApp('files_external');
+			return $this->factory = new ExternalStorageFactory(Server::get(\OCA\Files_External\Service\BackendService::class));
+		}
+		if (!class_exists(\OCA\Files_External\AppInfo\Application::class)) {
+			$path = $this->appManager->getAppPath('files_external');
+			require_once $path . '/composer/autoload.php';
+		}
+		$service = new \OCA\Files_External\Service\BackendService(
+			Server::get(\OCP\IAppConfig::class), Server::get(\Psr\Log\LoggerInterface::class));
+		$app = new \OCA\Files_External\AppInfo\Application();
+		$service->registerBackendProvider($app);
+		$service->registerAuthMechanismProvider($app);
+		return $this->factory = new ExternalStorageFactory($service);
 	}
 }

lib/Service/UserBackupService.php

@@ -0,0 +1,66 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCA\NgBackup\Db\Target;
+use OCA\NgBackup\UserMigration\RepositoryExportDestination;
+use OCA\NgBackup\UserMigration\UserMigrationServiceLocator;
+use OCP\IUser;
+use OCP\Lock\LockedException;
+use OCP\UserMigration\UserMigrationException;
+
+/**
+ * Per-user backup via user_migration: every registered migrator's export streams straight into
+ * the encrypted repository (no zip, no copy in the user's own storage, see
+ * RepositoryExportDestination). Shares blobs with the full backup; prune() keeps a user export's
+ * blobs referenced through its manifest under users/<uid>/.
+ *
+ * user_migration is an optional dependency (unlike files_external): without it, only this
+ * per-user backup/restore is unavailable, the full backup still works.
+ */
+final class UserBackupService {
+	public function __construct(
+		private TargetService $targets,
+		private LeaseService $leases,
+		private UserMigrationServiceLocator $locator,
+	) {
+	}
+
+	/** @throws UserMigrationException when user_migration is not enabled, or the export itself fails */
+	public function backupUser(Target $target, IUser $user): string {
+		$service = $this->locator->get();
+		return $this->withSharedLock($target, function (callable $refresh) use ($target, $user, $service) {
+			$repo = $this->targets->repository($target);
+			$dest = new RepositoryExportDestination($repo, $user->getUID(), LeaseService::throttled($refresh));
+			$service->export($dest, $user);
+			// A short exclusive lock around the catalog write only: the shared lock above
+			// allows another concurrent backup (full or per-user) to be writing the catalog at
+			// the same time. The repository is reopened inside the lock, so the write builds on
+			// the latest catalog generation instead of the one loaded before the lock was taken.
+			$this->withCatalogLock($target, fn () => $this->targets->repository($target)->recordUserExport($dest->manifestPath()));
+			return $dest->manifestPath();
+		});
+	}
+
+	private function withSharedLock(Target $target, callable $fn): mixed {
+		try {
+			// Refreshed by RepositoryExportDestination as it writes data, so a long export keeps it.
+			return $this->leases->with(PruneService::lockKey($target), LeaseService::SHARED, 3600, $fn);
+		} catch (LockedException) {
+			throw new \RuntimeException('A cleanup of ' . $target->getName() . ' is in progress; try again later');
+		}
+	}
+
+	private function withCatalogLock(Target $target, callable $fn): mixed {
+		try {
+			return $this->leases->with(PruneService::catalogLockKey($target), LeaseService::EXCLUSIVE, 300, $fn);
+		} catch (LockedException) {
+			throw new \RuntimeException('Another catalog write for ' . $target->getName() . ' is in progress; try again');
+		}
+	}
+}

lib/Service/UserRestoreService.php

@@ -0,0 +1,137 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCA\NgBackup\Db\Target;
+use OCA\NgBackup\UserMigration\RepositoryExportDestination;
+use OCA\NgBackup\UserMigration\RepositoryImportSource;
+use OCA\NgBackup\UserMigration\UserMigrationServiceLocator;
+use OCP\EventDispatcher\IEventDispatcher;
+use OCP\Files\Events\Node\FilesystemTornDownEvent;
+use OCP\IUser;
+use OCP\IUserManager;
+use OCP\Lock\LockedException;
+use OCP\Security\ISecureRandom;
+use OCP\UserMigration\UserMigrationException;
+
+/**
+ * Restoring a user from a user_migration export (see UserBackupService), never over an existing
+ * account:
+ *  - replace: a safety export of the current state goes into the repository first, then the
+ *    account is deleted and recreated fresh from the backup, under the same uid;
+ *  - as-backup: the backup is restored into a new account "<uid>-bak" (or "-bak-2", ...) instead,
+ *    so an admin can compare and transfer by hand. Nextcloud cannot rename a uid, so the *backup*
+ *    gets the new name, never the existing account.
+ */
+final class UserRestoreService {
+	public const MODE_REPLACE = 'replace';
+	public const MODE_AS_BACKUP = 'as-backup';
+
+	public function __construct(
+		private TargetService $targets,
+		private LeaseService $leases,
+		private UserMigrationServiceLocator $locator,
+		private IUserManager $userManager,
+		private ISecureRandom $random,
+		private IEventDispatcher $events,
+	) {
+	}
+
+	/** @throws UserMigrationException when user_migration is not enabled, or the restore itself fails */
+	public function restoreUser(Target $target, string $manifestPath, string $mode = self::MODE_REPLACE): IUser {
+		$service = $this->locator->get();
+		return $this->withSharedLock($target, function (callable $refresh) use ($target, $manifestPath, $mode, $service): IUser {
+			$repo = $this->targets->repository($target);
+			// Only ever read a manifest the verified catalog actually recorded: a path alone
+			// (even one this app generated before) proves nothing about it still being current
+			// or genuine once the catalog's rollback protection is supposed to vouch for it.
+			if (!$repo->isRecordedUserExport($manifestPath)) {
+				throw new \InvalidArgumentException("$manifestPath is not a recorded user export for this location");
+			}
+			$beat = LeaseService::throttled($refresh);
+			$source = new RepositoryImportSource($repo, $manifestPath, $beat);
+			$originalUid = $source->getOriginalUid();
+
+			if ($mode === self::MODE_AS_BACKUP) {
+				$backupUid = $this->freeBackupUid($originalUid);
+				$user = $this->userManager->createUser($backupUid, $this->random->generate(32));
+				if ($user === false) {
+					throw new \RuntimeException("Could not create the account $backupUid");
+				}
+				try {
+					return $service->import($source, $user);
+				} catch (\Throwable $e) {
+					// A partially-imported, never-used account left behind is strictly worse
+					// than no account at all; the original source account was never touched.
+					$user->delete();
+					throw $e;
+				}
+			}
+
+			if ($mode !== self::MODE_REPLACE) {
+				throw new \InvalidArgumentException("Unknown restore mode: $mode");
+			}
+			$existing = $this->userManager->get($originalUid);
+			$safetyManifestPath = null;
+			if ($existing !== null) {
+				// Never import over a live account: export its current state first, so nothing
+				// is lost if the restore turns out to be the wrong choice.
+				$safety = new RepositoryExportDestination($repo, $originalUid, $beat);
+				$service->export($safety, $existing);
+				$safetyManifestPath = $safety->manifestPath();
+				// Same race as UserBackupService::backupUser(): reopen the repository inside the
+				// catalog lock so the write builds on the latest generation.
+				$this->withCatalogLock($target, fn () => $this->targets->repository($target)->recordUserExport($safetyManifestPath));
+				if (!$existing->delete()) {
+					throw new \RuntimeException("Could not delete the existing account $originalUid before restoring; its safety export is at $safetyManifestPath");
+				}
+				// IRootFolder caches a Folder per uid for the lifetime of this process; without
+				// this it would still hand the just-deleted account's (now storage-less) folder
+				// to the import below, and every write would fail.
+				$this->events->dispatchTyped(new FilesystemTornDownEvent());
+			}
+			try {
+				return $service->import($source, null);
+			} catch (\Throwable $e) {
+				// The original account is already gone at this point (or never existed); a
+				// failure here can only be reported, not undone in place. Its safety export
+				// (if any) is the recovery path, already recorded above.
+				throw new UserMigrationException(
+					"Could not restore $originalUid" . ($safetyManifestPath !== null ? "; its safety export is at $safetyManifestPath" : '') . ': ' . $e->getMessage(),
+					0,
+					$e,
+				);
+			}
+		});
+	}
+
+	private function freeBackupUid(string $uid): string {
+		$candidate = $uid . '-bak';
+		for ($n = 2; $this->userManager->userExists($candidate); $n++) {
+			$candidate = $uid . '-bak-' . $n;
+		}
+		return $candidate;
+	}
+
+	private function withSharedLock(Target $target, callable $fn): mixed {
+		try {
+			// Refreshed while the safety export writes and the import reads (see UserBackupService::withSharedLock()).
+			return $this->leases->with(PruneService::lockKey($target), LeaseService::SHARED, 3600, $fn);
+		} catch (LockedException) {
+			throw new \RuntimeException('A cleanup of ' . $target->getName() . ' is in progress; try again later');
+		}
+	}
+
+	private function withCatalogLock(Target $target, callable $fn): mixed {
+		try {
+			return $this->leases->with(PruneService::catalogLockKey($target), LeaseService::EXCLUSIVE, 300, $fn);
+		} catch (LockedException) {
+			throw new \RuntimeException('Another catalog write for ' . $target->getName() . ' is in progress; try again');
+		}
+	}
+}

lib/Service/VerifyService.php

@@ -0,0 +1,48 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCA\NgBackup\Db\Target;
+use OCP\Lock\LockedException;
+
+/** Checksum audit of a snapshot (occ backup:verify), see Repository::verify(). */
+final class VerifyService {
+	public function __construct(
+		private TargetService $targets,
+		private LeaseService $leases,
+	) {
+	}
+
+	/** @return array{filesChecked:int, blobsChecked:int, bytesChecked:int, missing:list<string>, failed:list<string>, unreadable:list<string>, readError:string} */
+	public function verify(Target $target, string $snapshotId, bool $deep = false): array {
+		return $this->run($target, $deep, fn (\OCA\NgBackup\Repository\Repository $repo, callable $heartbeat): array => $repo->verify($snapshotId, $deep, $heartbeat));
+	}
+
+	/** @return array{filesChecked:int, blobsChecked:int, bytesChecked:int, missing:list<string>, failed:list<string>, unreadable:list<string>, readError:string} */
+	public function verifyUserExport(Target $target, string $manifestPath, bool $deep = false): array {
+		return $this->run($target, $deep, fn (\OCA\NgBackup\Repository\Repository $repo, callable $heartbeat): array => $repo->verifyUserExport($manifestPath, $deep, $heartbeat));
+	}
+
+	private function run(Target $target, bool $deep, callable $fn): array {
+		$ttl = $deep ? 600 : 300;
+		try {
+			return $this->leases->with(PruneService::lockKey($target), LeaseService::SHARED, $ttl, function (callable $refresh) use ($target, $deep, $ttl, $fn): array {
+				$last = time();
+				$heartbeat = function () use ($refresh, $ttl, &$last): void {
+					if (time() - $last >= intdiv($ttl, 2)) {
+						$refresh();
+						$last = time();
+					}
+				};
+				return $fn($this->targets->repository($target), $heartbeat);
+			});
+		} catch (LockedException) {
+			throw new \RuntimeException('A cleanup of ' . $target->getName() . ' is in progress; try again later');
+		}
+	}
+}

lib/Settings/Admin.php

@@ -11,7 +11,7 @@ use OCP\AppFramework\Http\TemplateResponse;
 use OCP\Settings\ISettings;
 use OCP\Util;
 
-class Admin implements ISettings {
+final class Admin implements ISettings {
 	public function getForm(): TemplateResponse {
 		Util::addScript('ng_backup', 'ng_backup-admin');
 		Util::addStyle('ng_backup', 'ng_backup-admin');

lib/Settings/AdminSection.php

@@ -11,7 +11,7 @@ use OCP\IL10N;
 use OCP\IURLGenerator;
 use OCP\Settings\IIconSection;
 
-class AdminSection implements IIconSection {
+final class AdminSection implements IIconSection {
 	public function __construct(
 		private IL10N $l,
 		private IURLGenerator $url,

lib/SetupCheck/BackupStatusCheck.php

@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\SetupCheck;
+
+use OCA\NgBackup\Db\Run;
+use OCA\NgBackup\Db\RunMapper;
+use OCA\NgBackup\Service\AlertService;
+use OCA\NgBackup\Service\BackupService;
+use OCA\NgBackup\Service\KeyService;
+use OCA\NgBackup\Service\TargetService;
+use OCP\IL10N;
+use OCP\IURLGenerator;
+use OCP\SetupCheck\ISetupCheck;
+use OCP\SetupCheck\SetupResult;
+
+/** Shows the backup state in the admin overview (Security & setup warnings). */
+final class BackupStatusCheck implements ISetupCheck {
+	public function __construct(
+		private IL10N $l,
+		private IURLGenerator $url,
+		private KeyService $keys,
+		private TargetService $targets,
+		private RunMapper $runs,
+	) {
+	}
+
+	public function getCategory(): string {
+		return 'system';
+	}
+
+	public function getName(): string {
+		return $this->l->t('NG Backup');
+	}
+
+	public function run(): SetupResult {
+		$link = $this->url->linkToRouteAbsolute('settings.AdminSettings.index', ['section' => 'ng_backup']);
+		if (!$this->keys->isInitialized() || !$this->keys->everConfirmed()) {
+			return SetupResult::error($this->l->t('Backups are not set up: create the backup key and confirm the recovery kit.'), $link);
+		}
+		if ($this->keys->recoveryKitConfirmation() === null) {
+			return SetupResult::error($this->l->t('The backup passphrase was changed: download and confirm the new recovery kit.'), $link);
+		}
+		$targets = $this->targets->list();
+		if ($targets === []) {
+			return SetupResult::warning($this->l->t('No backup location is configured.'), $link);
+		}
+		$problems = [];
+		foreach ($targets as $t) {
+			$last = $this->runs->lastFinished($t->getId(), BackupService::KIND_FULL);
+			if ($last === null) {
+				$problems[] = $this->l->t('%s: no successful backup yet', [$t->getName()]);
+			} elseif (time() - (int)$last->getFinishedAt() > AlertService::STALE_AFTER) {
+				$problems[] = $this->l->t('%1$s: last successful backup %2$s', [$t->getName(), date('Y-m-d H:i', (int)$last->getFinishedAt())]);
+			}
+		}
+		foreach ($this->runs->findRecent(10) as $r) {
+			if ($r->getStatus() === Run::FAILED && $r->getStartedAt() > time() - AlertService::STALE_AFTER) {
+				$problems[] = $this->l->t('A %1$s run failed: %2$s', [$r->getKind(), mb_strimwidth((string)$r->getError(), 0, 120, '…')]);
+				break;
+			}
+		}
+		return $problems === []
+			? SetupResult::success($this->l->t('Recent backups to all locations succeeded.'))
+			: SetupResult::warning(implode("\n", $problems), $link);
+	}
+}

lib/UserMigration/RepositoryExportDestination.php

@@ -28,6 +28,8 @@ final class RepositoryExportDestination implements IExportDestination {
 	public function __construct(
 		private Repository $repo,
 		private string $uid,
+		/** Called while data is written (per chunk), to keep the location lease alive. */
+		private ?\Closure $heartbeat = null,
 	) {
 		$this->exportId = gmdate('Ymd\THis\Z') . '-' . bin2hex(random_bytes(4));
 	}
@@ -36,6 +38,7 @@ final class RepositoryExportDestination implements IExportDestination {
 		$writer = $this->repo->blobWriter($this->stats);
 		$writer->write($content);
 		$this->entries[self::norm($path)] = ['t' => 'f', 'b' => $writer->finish(), 's' => strlen($content)];
+		$this->beat();
 	}
 
 	public function addFileAsStream(string $path, $stream): void {
@@ -46,6 +49,7 @@ final class RepositoryExportDestination implements IExportDestination {
 				throw new UserMigrationException('Read error while exporting ' . $path);
 			}
 			$writer->write($chunk);
+			$this->beat();
 		}
 		$this->entries[self::norm($path)] = ['t' => 'f', 'b' => $writer->finish(), 's' => $writer->bytes()];
 	}
@@ -65,8 +69,11 @@ final class RepositoryExportDestination implements IExportDestination {
 				if ($stream === false) {
 					throw new \RuntimeException('Cannot read ' . $node->getPath());
 				}
-				$this->addFileAsStream($target, $stream);
-				fclose($stream);
+				try {
+					$this->addFileAsStream($target, $stream);
+				} finally {
+					fclose($stream);
+				}
 			}
 		}
 	}
@@ -89,6 +96,12 @@ final class RepositoryExportDestination implements IExportDestination {
 		return $this->stats;
 	}
 
+	private function beat(): void {
+		if ($this->heartbeat !== null) {
+			($this->heartbeat)();
+		}
+	}
+
 	private static function norm(string $path): string {
 		return trim($path, '/');
 	}

lib/UserMigration/RepositoryImportSource.php

@@ -8,6 +8,7 @@ declare(strict_types=1);
 namespace OCA\NgBackup\UserMigration;
 
 use OCA\NgBackup\Repository\Repository;
+use OCP\Files\File;
 use OCP\Files\Folder;
 use OCP\UserMigration\IImportSource;
 use OCP\UserMigration\UserMigrationException;
@@ -19,6 +20,8 @@ final class RepositoryImportSource implements IImportSource {
 	public function __construct(
 		private Repository $repo,
 		string $manifestPath,
+		/** Called while blobs are read, to keep the location lease alive. */
+		private ?\Closure $heartbeat = null,
 	) {
 		$this->manifest = json_decode($repo->getObject($manifestPath), true, 512, JSON_THROW_ON_ERROR);
 	}
@@ -30,11 +33,18 @@ final class RepositoryImportSource implements IImportSource {
 		return $data;
 	}
 
+	/** @return resource */
 	public function getFileAsStream(string $path) {
 		$entry = $this->entry($path, 'f');
 		// Phase 0: buffer in php://temp (memory up to 8 MiB, then a temp file for this one file).
 		$stream = fopen('php://temp/maxmemory:' . (8 * 1048576), 'w+b');
+		if ($stream === false) {
+			throw new UserMigrationException('Cannot buffer ' . $path);
+		}
 		foreach ($this->repo->readBlobs($entry['b']) as $data) {
+			if ($this->heartbeat !== null) {
+				($this->heartbeat)();
+			}
 			for ($done = 0, $len = strlen($data); $done < $len; $done += $n) {
 				$n = fwrite($stream, $done === 0 ? $data : substr($data, $done));
 				if ($n === false || $n === 0) {
@@ -51,6 +61,7 @@ final class RepositoryImportSource implements IImportSource {
 		$prefix = trim($path, '/');
 		$prefix = $prefix === '' ? '' : $prefix . '/';
 		$names = [];
+		/** @var string $p */
 		foreach (array_keys($this->manifest['entries']) as $p) {
 			if ($prefix === '' || str_starts_with($p, $prefix)) {
 				$rest = substr($p, strlen($prefix));
@@ -70,6 +81,7 @@ final class RepositoryImportSource implements IImportSource {
 		if (isset($this->manifest['entries'][$p])) {
 			return true;
 		}
+		/** @var string $k */
 		foreach (array_keys($this->manifest['entries']) as $k) {
 			if (str_starts_with($k, $p . '/')) {
 				return true;
@@ -91,13 +103,25 @@ final class RepositoryImportSource implements IImportSource {
 				$this->copyToFolder($sub, $path);
 			} else {
 				$stream = $this->getFileAsStream($path);
-				if ($destination->nodeExists($name)) {
-					$destination->get($name)->putContent($stream);
-				} else {
-					$destination->newFile($name, $stream);
-				}
-				if (is_resource($stream)) {
-					fclose($stream);
+				try {
+					if ($destination->nodeExists($name)) {
+						$existing = $destination->get($name);
+						if (!$existing instanceof File) {
+							throw new UserMigrationException("$path exists and is not a file");
+						}
+						$existing->putContent($stream);
+					} else {
+						$destination->newFile($name, $stream);
+					}
+				} finally {
+					// putContent()/newFile() already close the stream once they've consumed it:
+					// despite the @return resource docblock above, $stream is no longer a
+					// resource by the time we get here (verified against a real storage; a
+					// double fclose() throws a TypeError on PHP 8).
+					/** @psalm-suppress RedundantConditionGivenDocblockType */
+					if (is_resource($stream)) {
+						fclose($stream);
+					}
 				}
 			}
 		}

lib/UserMigration/UserMigrationInstaller.php

@@ -0,0 +1,77 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\UserMigration;
+
+use OCP\App\AppPathNotFoundException;
+use OCP\App\IAppManager;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Helper\QuestionHelper;
+use Symfony\Component\Console\Question\ConfirmationQuestion;
+
+/**
+ * Installs or enables the optional user_migration app, but only when the administrator asked for it
+ * (occ prompt or --install-user-migration). Runs occ in a child process, as the admin would.
+ */
+final class UserMigrationInstaller {
+	private const APP = 'user_migration';
+
+	public function __construct(
+		private IAppManager $appManager,
+	) {
+	}
+
+	public function isEnabled(): bool {
+		return $this->appManager->isEnabledForAnyone(self::APP);
+	}
+
+	private function codeIsPresent(): bool {
+		try {
+			$this->appManager->getAppPath(self::APP);
+			return true;
+		} catch (AppPathNotFoundException) {
+			return false;
+		}
+	}
+
+	/** Installs (from the app store, if missing) and enables user_migration; throws on failure. */
+	public function install(): void {
+		$args = $this->codeIsPresent() ? ['app:enable', self::APP] : ['app:install', self::APP];
+		/** @psalm-suppress UndefinedClass */
+		$occ = \OC::$SERVERROOT . '/occ';
+		$command = implode(' ', array_map('escapeshellarg', [PHP_BINARY, $occ, ...$args])) . ' 2>&1';
+		exec($command, $lines, $code);
+		if ($code !== 0) {
+			throw new \RuntimeException("occ " . implode(' ', $args) . " failed:\n" . implode("\n", $lines));
+		}
+	}
+
+	/**
+	 * Returns when user_migration is enabled. Otherwise asks the administrator (interactive shell) or
+	 * requires --install-user-migration, and throws when neither gives consent.
+	 *
+	 * @throws \RuntimeException
+	 */
+	public function ensureEnabled(InputInterface $input, OutputInterface $output): void {
+		if ($this->isEnabled()) {
+			return;
+		}
+		$consent = $input->getOption('install-user-migration') === true;
+		if (!$consent && $input->isInteractive()) {
+			$consent = (new QuestionHelper())->ask($input, $output, new ConfirmationQuestion(
+				'The user_migration app is not enabled. Install and enable it now? [y/N] ', false)) === true;
+		}
+		if (!$consent) {
+			throw new \RuntimeException('The user_migration app is not enabled; per-user backup/restore needs it. Run "occ '
+				. 'app:install ' . self::APP . '" and "occ app:enable ' . self::APP . '", or repeat with --install-user-migration');
+		}
+		$output->writeln('Installing and enabling user_migration (approved by the administrator)...');
+		$this->install();
+		throw new \RuntimeException('user_migration is installed and enabled; run this command again');
+	}
+}

lib/UserMigration/UserMigrationServiceLocator.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\UserMigration;
+
+use OCP\App\IAppManager;
+use OCP\Server;
+use OCP\UserMigration\UserMigrationException;
+
+/**
+ * Resolves user_migration's own (internal, non-public) UserMigrationService on demand.
+ *
+ * Unlike files_external, user_migration is an optional dependency: without it, only per-user
+ * backup/restore is unavailable, the full backup still works. The class is never autoloaded by
+ * composer; everything that touches it is behind this one class.
+ */
+final class UserMigrationServiceLocator {
+	public function __construct(
+		private IAppManager $appManager,
+	) {
+	}
+
+	/** @throws UserMigrationException when user_migration is not enabled anywhere */
+	public function get(): object {
+		if (!$this->appManager->isEnabledForAnyone('user_migration')) {
+			throw new UserMigrationException('The user_migration app is not enabled; per-user backup/restore is unavailable');
+		}
+		$this->appManager->loadApp('user_migration');
+		return Server::get(\OCA\UserMigration\Service\UserMigrationService::class);
+	}
+}

package-lock.json

@@ -12,6 +12,7 @@
 				"@nextcloud/axios": "^2.5.1",
 				"@nextcloud/dialogs": "^7.4.0",
 				"@nextcloud/l10n": "^3.4.0",
+				"@nextcloud/password-confirmation": "^6.1.0",
 				"@nextcloud/router": "^3.0.1",
 				"@nextcloud/vue": "^9.0.0",
 				"vue": "^3.5.0"
@@ -885,6 +886,24 @@
 				"node": "^20.0.0 || ^22.0.0 || ^24.0.0"
 			}
 		},
+		"node_modules/@nextcloud/password-confirmation": {
+			"version": "6.1.0",
+			"resolved": "https://registry.npmjs.org/@nextcloud/password-confirmation/-/password-confirmation-6.1.0.tgz",
+			"integrity": "sha512-N2ChXDbPcUcQCoAjj1yc65zfc61yiKpdM3qm/y3Y/y//NG7XWNNINwBg85lqJ2SISgmVStpsQ1d0blpFCoQXkQ==",
+			"license": "MIT",
+			"dependencies": {
+				"@nextcloud/auth": "^2.5.3",
+				"@nextcloud/axios": "^2.5.2",
+				"@nextcloud/l10n": "^3.4.1",
+				"@nextcloud/logger": "^3.0.3",
+				"@nextcloud/router": "^3.1.0",
+				"@nextcloud/vue": "^9.6.0",
+				"vue": "^3.5.30"
+			},
+			"engines": {
+				"node": "^20.0.0 || ^22.0.0 || ^24.0.0"
+			}
+		},
 		"node_modules/@nextcloud/paths": {
 			"version": "3.1.0",
 			"resolved": "https://registry.npmjs.org/@nextcloud/paths/-/paths-3.1.0.tgz",

package.json

@@ -12,6 +12,7 @@
 		"@nextcloud/axios": "^2.5.1",
 		"@nextcloud/dialogs": "^7.4.0",
 		"@nextcloud/l10n": "^3.4.0",
+		"@nextcloud/password-confirmation": "^6.1.0",
 		"@nextcloud/router": "^3.0.1",
 		"@nextcloud/vue": "^9.0.0",
 		"vue": "^3.5.0"

psalm-baseline.xml

@@ -0,0 +1,490 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<files psalm-version="6.19.1@e2ca44251c1f1aa2e35452d426895746b47de64e">
+  <file src="lib/Backend/ExternalStorageFactory.php">
+    <MissingClosureParamType>
+      <code><![CDATA[$p]]></code>
+      <code><![CDATA[$p]]></code>
+    </MissingClosureParamType>
+    <MissingClosureReturnType>
+      <code><![CDATA[fn ($p) => $p->jsonSerialize()]]></code>
+      <code><![CDATA[fn ($p) => $p->jsonSerialize()]]></code>
+    </MissingClosureReturnType>
+  </file>
+  <file src="lib/Backend/IBackend.php">
+    <MissingParamType>
+      <code><![CDATA[$stream]]></code>
+    </MissingParamType>
+  </file>
+  <file src="lib/Backend/LocalBackend.php">
+    <MissingParamType>
+      <code><![CDATA[$stream]]></code>
+    </MissingParamType>
+    <TypeDoesNotContainType>
+      <code><![CDATA[$out !== false]]></code>
+    </TypeDoesNotContainType>
+  </file>
+  <file src="lib/Backend/StorageBackend.php">
+    <MissingParamType>
+      <code><![CDATA[$stream]]></code>
+    </MissingParamType>
+  </file>
+  <file src="lib/BackgroundJob/BackupJob.php">
+    <MissingParamType>
+      <code><![CDATA[$argument]]></code>
+    </MissingParamType>
+  </file>
+  <file src="lib/BackgroundJob/RestoreJob.php">
+    <MissingParamType>
+      <code><![CDATA[$argument]]></code>
+    </MissingParamType>
+  </file>
+  <file src="lib/Command/Browse.php">
+    <InvalidOperand>
+      <code><![CDATA[$b /= 1024]]></code>
+    </InvalidOperand>
+  </file>
+  <file src="lib/Command/KeyConfirm.php">
+    <UndefinedInterfaceMethod>
+      <code><![CDATA[ask]]></code>
+      <code><![CDATA[ask]]></code>
+    </UndefinedInterfaceMethod>
+  </file>
+  <file src="lib/Command/KeyImport.php">
+    <UndefinedInterfaceMethod>
+      <code><![CDATA[ask]]></code>
+    </UndefinedInterfaceMethod>
+  </file>
+  <file src="lib/Command/KeyInit.php">
+    <UndefinedInterfaceMethod>
+      <code><![CDATA[ask]]></code>
+      <code><![CDATA[ask]]></code>
+    </UndefinedInterfaceMethod>
+  </file>
+  <file src="lib/Command/KeySlots.php">
+    <UndefinedInterfaceMethod>
+      <code><![CDATA[ask]]></code>
+      <code><![CDATA[ask]]></code>
+    </UndefinedInterfaceMethod>
+  </file>
+  <file src="lib/Command/Prune.php">
+    <PossiblyFalseOperand>
+      <code><![CDATA[json_encode($this->prune->policy()->toArray())]]></code>
+    </PossiblyFalseOperand>
+  </file>
+  <file src="lib/Command/RunBackup.php">
+    <PossiblyNullArgument>
+      <code><![CDATA[$run->getSnapshotId()]]></code>
+    </PossiblyNullArgument>
+  </file>
+  <file src="lib/Command/Status.php">
+    <RiskyTruthyFalsyComparison>
+      <code><![CDATA[$c]]></code>
+      <code><![CDATA[$r->getFinishedAt()]]></code>
+    </RiskyTruthyFalsyComparison>
+  </file>
+  <file src="lib/Command/TargetAdd.php">
+    <PossiblyNullArgument>
+      <code><![CDATA[$r['target']->getRepositoryId()]]></code>
+    </PossiblyNullArgument>
+    <PossiblyUndefinedArrayOffset>
+      <code><![CDATA[$v]]></code>
+    </PossiblyUndefinedArrayOffset>
+  </file>
+  <file src="lib/Command/TargetBackends.php">
+    <UndefinedClass>
+      <code><![CDATA[Base]]></code>
+    </UndefinedClass>
+  </file>
+  <file src="lib/Command/TargetLimit.php">
+    <InvalidOperand>
+      <code><![CDATA[(float)$m[1] * $factor]]></code>
+    </InvalidOperand>
+  </file>
+  <file src="lib/Command/TargetList.php">
+    <UndefinedClass>
+      <code><![CDATA[Base]]></code>
+    </UndefinedClass>
+  </file>
+  <file src="lib/Command/TargetTrustCurrent.php">
+    <UndefinedInterfaceMethod>
+      <code><![CDATA[ask]]></code>
+    </UndefinedInterfaceMethod>
+  </file>
+  <file src="lib/Command/Trash.php">
+    <RedundantCastGivenDocblockType>
+      <code><![CDATA[(string)($info['time'] ?? '')]]></code>
+    </RedundantCastGivenDocblockType>
+  </file>
+  <file src="lib/Controller/AdminApiController.php">
+    <InvalidOperand>
+      <code><![CDATA[$maxGb * 1073741824]]></code>
+      <code><![CDATA[$maxGb * 1073741824]]></code>
+    </InvalidOperand>
+    <PossiblyNullArgument>
+      <code><![CDATA[$r->getSnapshotId()]]></code>
+    </PossiblyNullArgument>
+  </file>
+  <file src="lib/Crypto/StreamCipher.php">
+    <MissingParamType>
+      <code><![CDATA[$in]]></code>
+      <code><![CDATA[$out]]></code>
+    </MissingParamType>
+    <PossiblyFalseArgument>
+      <code><![CDATA[$in]]></code>
+      <code><![CDATA[$in]]></code>
+      <code><![CDATA[$in]]></code>
+      <code><![CDATA[$in]]></code>
+      <code><![CDATA[$in]]></code>
+      <code><![CDATA[$in]]></code>
+      <code><![CDATA[$out]]></code>
+      <code><![CDATA[$out]]></code>
+      <code><![CDATA[$out]]></code>
+      <code><![CDATA[$out]]></code>
+      <code><![CDATA[$out]]></code>
+      <code><![CDATA[$out]]></code>
+    </PossiblyFalseArgument>
+    <PossiblyInvalidArrayAccess>
+      <code><![CDATA[unpack('N', $len)[1]]]></code>
+    </PossiblyInvalidArrayAccess>
+  </file>
+  <file src="lib/Db/AppConfigCatalogAnchor.php">
+    <PossiblyFalseArgument>
+      <code><![CDATA[json_encode(['gen' => $gen, 'hash' => $hash])]]></code>
+    </PossiblyFalseArgument>
+  </file>
+  <file src="lib/Db/DbDumper.php">
+    <InvalidArrayOffset>
+      <code><![CDATA[$info['sha256']]]></code>
+      <code><![CDATA[$manifest['sequences']]]></code>
+    </InvalidArrayOffset>
+    <MissingClosureReturnType>
+      <code><![CDATA[fn ($c) => $end[array_search($c, $columns, true)]]]></code>
+      <code><![CDATA[fn ($c) => $q($c)]]></code>
+      <code><![CDATA[fn (string $c) => $this->db->quoteIdentifier($c)]]></code>
+      <code><![CDATA[fn (string $c) => $this->db->quoteIdentifier($c)]]></code>
+    </MissingClosureReturnType>
+    <PossiblyFalseArgument>
+      <code><![CDATA[$value]]></code>
+    </PossiblyFalseArgument>
+    <PossiblyNullArgument>
+      <code><![CDATA[$columns]]></code>
+    </PossiblyNullArgument>
+    <UndefinedClass>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[$this->db]]></code>
+      <code><![CDATA[TransactionIsolationLevel]]></code>
+      <code><![CDATA[\Doctrine\DBAL\ParameterType]]></code>
+      <code><![CDATA[\Doctrine\DBAL\ParameterType]]></code>
+      <code><![CDATA[\Doctrine\DBAL\ParameterType]]></code>
+      <code><![CDATA[\Doctrine\DBAL\Platforms\PostgreSQLPlatform]]></code>
+      <code><![CDATA[\Doctrine\DBAL\Platforms\PostgreSQLPlatform]]></code>
+      <code><![CDATA[\Doctrine\DBAL\Platforms\PostgreSQLPlatform]]></code>
+      <code><![CDATA[\Doctrine\DBAL\Schema\Table]]></code>
+      <code><![CDATA[\Doctrine\DBAL\Schema\Table]]></code>
+      <code><![CDATA[\Doctrine\DBAL\Schema\Table]]></code>
+      <code><![CDATA[private]]></code>
+    </UndefinedClass>
+  </file>
+  <file src="lib/Db/Run.php">
+    <PropertyNotSetInConstructor>
+      <code><![CDATA[Run]]></code>
+    </PropertyNotSetInConstructor>
+  </file>
+  <file src="lib/Db/Snapshot.php">
+    <PropertyNotSetInConstructor>
+      <code><![CDATA[Snapshot]]></code>
+    </PropertyNotSetInConstructor>
+  </file>
+  <file src="lib/Db/Target.php">
+    <PropertyNotSetInConstructor>
+      <code><![CDATA[Target]]></code>
+    </PropertyNotSetInConstructor>
+  </file>
+  <file src="lib/Job/BackupRun.php">
+    <ArgumentTypeCoercion>
+      <code><![CDATA[$blobs]]></code>
+    </ArgumentTypeCoercion>
+    <MissingParamType>
+      <code><![CDATA[$fh]]></code>
+    </MissingParamType>
+    <PossiblyUndefinedArrayOffset>
+      <code><![CDATA[$mtime]]></code>
+      <code><![CDATA[$state['phase']]]></code>
+      <code><![CDATA[$state['stats']]]></code>
+    </PossiblyUndefinedArrayOffset>
+  </file>
+  <file src="lib/Job/ParentCursor.php">
+    <PossiblyNullReference>
+      <code><![CDATA[next]]></code>
+    </PossiblyNullReference>
+  </file>
+  <file src="lib/Job/TreeWalker.php">
+    <RedundantCastGivenDocblockType>
+      <code><![CDATA[(string)$name]]></code>
+    </RedundantCastGivenDocblockType>
+  </file>
+  <file src="lib/Migration/Version000001Date20261002000000.php">
+    <UndefinedDocblockClass>
+      <code><![CDATA[$schema->createTable('ngb_targets')]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+    </UndefinedDocblockClass>
+  </file>
+  <file src="lib/Migration/Version000002Date20261002010000.php">
+    <UndefinedDocblockClass>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+    </UndefinedDocblockClass>
+  </file>
+  <file src="lib/Migration/Version000003Date20261002020000.php">
+    <UndefinedDocblockClass>
+      <code><![CDATA[$schema->getTable('ngb_targets')]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+    </UndefinedDocblockClass>
+  </file>
+  <file src="lib/Migration/Version000004Date20261002030000.php">
+    <UndefinedDocblockClass>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+    </UndefinedDocblockClass>
+  </file>
+  <file src="lib/Migration/Version000005Date20261002040000.php">
+    <UndefinedDocblockClass>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+      <code><![CDATA[$t]]></code>
+    </UndefinedDocblockClass>
+  </file>
+  <file src="lib/Repository/BlobIndex.php">
+    <PossiblyFalseArgument>
+      <code><![CDATA[$stream]]></code>
+      <code><![CDATA[$stream]]></code>
+    </PossiblyFalseArgument>
+  </file>
+  <file src="lib/Repository/Catalog.php">
+    <PossiblyFalseArgument>
+      <code><![CDATA[$stream]]></code>
+      <code><![CDATA[$stream]]></code>
+    </PossiblyFalseArgument>
+  </file>
+  <file src="lib/Repository/PackWriter.php">
+    <InvalidPropertyAssignmentValue>
+      <code><![CDATA[$this->buffer]]></code>
+    </InvalidPropertyAssignmentValue>
+    <PossiblyFalsePropertyAssignmentValue>
+      <code><![CDATA[fopen('php://temp/maxmemory:' . ($this->targetSize + 8 * 1048576), 'w+b')]]></code>
+    </PossiblyFalsePropertyAssignmentValue>
+    <RedundantPropertyInitializationCheck>
+      <code><![CDATA[isset($this->buffer)]]></code>
+    </RedundantPropertyInitializationCheck>
+  </file>
+  <file src="lib/Repository/Repository.php">
+    <InvalidOperand>
+      <code><![CDATA[strlen($data) * 0.95]]></code>
+    </InvalidOperand>
+    <InvalidReturnStatement>
+      <code><![CDATA[['snapshot' => $snapshotId] + $stats]]></code>
+    </InvalidReturnStatement>
+    <InvalidReturnType>
+      <code><![CDATA[array{snapshot:string, files:int, reused:int, read:int, newBlobs:int, dupBlobs:int, uploaded:int}]]></code>
+    </InvalidReturnType>
+    <MissingParamType>
+      <code><![CDATA[$fh]]></code>
+    </MissingParamType>
+    <PossiblyFalseArgument>
+      <code><![CDATA[$encrypted]]></code>
+      <code><![CDATA[$encrypted]]></code>
+      <code><![CDATA[$encrypted]]></code>
+      <code><![CDATA[$encrypted]]></code>
+      <code><![CDATA[$fh]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$plain]]></code>
+      <code><![CDATA[$s]]></code>
+      <code><![CDATA[$s]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+      <code><![CDATA[$tree]]></code>
+    </PossiblyFalseArgument>
+    <PossiblyUndefinedArrayOffset>
+      <code><![CDATA[$stats['files']]]></code>
+      <code><![CDATA[$stats['reused']]]></code>
+    </PossiblyUndefinedArrayOffset>
+    <PropertyNotSetInConstructor>
+      <code><![CDATA[$catalog]]></code>
+    </PropertyNotSetInConstructor>
+  </file>
+  <file src="lib/Service/AlertService.php">
+    <InvalidOperand>
+      <code><![CDATA[$bytes / $limit * 100]]></code>
+      <code><![CDATA[0.8 * $limit]]></code>
+    </InvalidOperand>
+    <PossiblyFalseOperand>
+      <code><![CDATA[json_encode(array_diff_key($params, ['actor' => 1]), JSON_UNESCAPED_SLASHES)]]></code>
+    </PossiblyFalseOperand>
+  </file>
+  <file src="lib/Service/BackupService.php">
+    <InvalidOperand>
+      <code><![CDATA[$deadline - microtime(true) + 120]]></code>
+    </InvalidOperand>
+    <UndefinedClass>
+      <code><![CDATA[\OC]]></code>
+      <code><![CDATA[\OC]]></code>
+    </UndefinedClass>
+    <UndefinedInterfaceMethod>
+      <code><![CDATA[getInner]]></code>
+    </UndefinedInterfaceMethod>
+  </file>
+  <file src="lib/Service/KeyService.php">
+    <ArgumentTypeCoercion>
+      <code><![CDATA[array_diff(range(1, self::MAX_SLOTS), $used)]]></code>
+    </ArgumentTypeCoercion>
+    <LessSpecificReturnStatement>
+      <code><![CDATA[array_map(fn ($s) => ['slot' => $s['slot'], 'label' => $s['label'], 'created' => $s['created']], $this->wrappedKey()['slots'])]]></code>
+    </LessSpecificReturnStatement>
+    <MissingClosureParamType>
+      <code><![CDATA[$s]]></code>
+      <code><![CDATA[$s]]></code>
+    </MissingClosureParamType>
+    <MissingClosureReturnType>
+      <code><![CDATA[static fn (string $c) => strtoupper(preg_replace('/[^A-Za-z0-9]/', '', $c) ?? '')]]></code>
+    </MissingClosureReturnType>
+    <MoreSpecificReturnType>
+      <code><![CDATA[list<array{slot:int, label:string, created:int}>]]></code>
+    </MoreSpecificReturnType>
+    <PossiblyFalseArgument>
+      <code><![CDATA[base64_decode($this->crypto->decrypt($enc), true)]]></code>
+    </PossiblyFalseArgument>
+  </file>
+  <file src="lib/Service/PruneService.php">
+    <LessSpecificReturnStatement>
+      <code><![CDATA[['kept' => $keep, 'forgotten' => $forget, 'purged' => $purged, 'prune' => $prune]]]></code>
+    </LessSpecificReturnStatement>
+    <MissingClosureReturnType>
+      <code><![CDATA[fn () => $fn()]]></code>
+    </MissingClosureReturnType>
+    <MoreSpecificReturnType>
+      <code><![CDATA[array{kept: array<string, list<string>>, forgotten: list<string>, purged: list<string>, prune: array}]]></code>
+    </MoreSpecificReturnType>
+  </file>
+  <file src="lib/Service/RestoreFullService.php">
+    <EmptyArrayAccess>
+      <code><![CDATA[$backupConfig[$key]]]></code>
+    </EmptyArrayAccess>
+    <UndefinedInterfaceMethod>
+      <code><![CDATA[getInner]]></code>
+    </UndefinedInterfaceMethod>
+    <UnresolvableInclude>
+      <code><![CDATA[include $path]]></code>
+    </UnresolvableInclude>
+  </file>
+  <file src="lib/Service/RestoreService.php">
+    <LessSpecificReturnStatement>
+      <code><![CDATA[array_values($children)]]></code>
+    </LessSpecificReturnStatement>
+    <MissingDependency>
+      <code><![CDATA[$this->root]]></code>
+      <code><![CDATA[private]]></code>
+    </MissingDependency>
+    <MoreSpecificReturnType>
+      <code><![CDATA[list<array{name:string, type:string, size:int, mtime:int|null, files:int}>]]></code>
+    </MoreSpecificReturnType>
+    <PossiblyFalseArgument>
+      <code><![CDATA[$in]]></code>
+      <code><![CDATA[$out]]></code>
+      <code><![CDATA[$out]]></code>
+    </PossiblyFalseArgument>
+    <PossiblyNullArrayOffset>
+      <code><![CDATA[$children]]></code>
+      <code><![CDATA[$children]]></code>
+    </PossiblyNullArrayOffset>
+    <RedundantCastGivenDocblockType>
+      <code><![CDATA[(string)$relPath]]></code>
+      <code><![CDATA[(string)$relPath]]></code>
+    </RedundantCastGivenDocblockType>
+  </file>
+  <file src="lib/Service/TargetService.php">
+    <InvalidReturnStatement>
+      <code><![CDATA[$this->factory()->describeBackends()]]></code>
+    </InvalidReturnStatement>
+    <InvalidReturnType>
+      <code><![CDATA[list<array{id:string, name:string, auth:list<string>, parameters:array}>]]></code>
+    </InvalidReturnType>
+    <UndefinedDocblockClass>
+      <code><![CDATA[Server::get(\OCA\Files_External\Service\BackendService::class)]]></code>
+    </UndefinedDocblockClass>
+    <UnresolvableInclude>
+      <code><![CDATA[require_once $path . '/composer/autoload.php']]></code>
+    </UnresolvableInclude>
+  </file>
+</files>

psalm.xml

@@ -0,0 +1,54 @@
+<?xml version="1.0"?>
+<!-- SPDX-FileCopyrightText: 2026 Dillard Blom -->
+<!-- SPDX-License-Identifier: AGPL-3.0-or-later -->
+<psalm
+    errorLevel="2"
+    resolveFromConfigFile="true"
+    findUnusedBaselineEntry="true"
+    findUnusedCode="false"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+    errorBaseline="psalm-baseline.xml"
+>
+    <projectFiles>
+        <directory name="lib" />
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+
+    <!-- Interface-only stubs for Nextcloud's public API, not autoloaded at runtime: scanned for
+         type resolution only, never reported on. lib/ must only use OCP\, never internal OC\
+         classes, since those differ between the supported Nextcloud versions (PLAN.md section 6). -->
+    <extraFiles>
+        <directory name="vendor/nextcloud/ocp/OCP" />
+        <directory name="vendor/nextcloud/ocp/NCU" />
+    </extraFiles>
+
+    <issueHandlers>
+        <UndefinedClass>
+            <errorLevel type="suppress">
+                <!-- Provided by files_external at runtime; not a composer dependency (PLAN.md 3.5). -->
+                <referencedClass name="OCA\Files_External\**" />
+                <!-- Provided by user_migration at runtime, an optional dependency (PLAN.md 3.8). -->
+                <referencedClass name="OCA\UserMigration\**" />
+            </errorLevel>
+        </UndefinedClass>
+        <UndefinedDocblockClass>
+            <errorLevel type="suppress">
+                <!-- Server::get()'s templated return type resolving the users_migration class-string
+                     constant below; same reason as the UndefinedClass suppression above. -->
+                <referencedClass name="OCA\UserMigration\**" />
+            </errorLevel>
+        </UndefinedDocblockClass>
+        <!-- The #[\Override] attribute convention (PHP 8.3+) adds no behaviour; this app supports
+             PHP 8.1+, and applying it to every interface-implementing method project-wide is pure
+             ceremony with no bug-catching value, so it's suppressed rather than papered over. -->
+        <MissingOverrideAttribute>
+            <errorLevel type="suppress">
+                <directory name="lib" />
+            </errorLevel>
+        </MissingOverrideAttribute>
+    </issueHandlers>
+</psalm>

spikes/03-db-dump.php

@@ -48,9 +48,11 @@ $seqStates = static function () use ($db, $prefix): array {
 	return $out;
 };
 // Let one sequence run ahead of the data (deleted rows, rollbacks): MAX+1 would be wrong.
-$fcSeq = $db->fetchOne("SELECT pg_get_serial_sequence(?, 'fileid')", [$prefix . 'filecache']);
-for ($i = 0; $i < 50; $i++) {
-	$db->fetchOne('SELECT nextval(CAST(? AS regclass))', [$fcSeq]);
+if ($db->getDatabasePlatform() instanceof \Doctrine\DBAL\Platforms\PostgreSQLPlatform) {
+	$fcSeq = $db->fetchOne("SELECT pg_get_serial_sequence(?, 'fileid')", [$prefix . 'filecache']);
+	for ($i = 0; $i < 50; $i++) {
+		$db->fetchOne('SELECT nextval(CAST(? AS regclass))', [$fcSeq]);
+	}
 }
 $seqBefore = $seqStates();
 $before = [];
@@ -71,6 +73,17 @@ $dumpBytes = array_sum(array_column($manifest['tables'], 'bytes'));
 printf("dump size (plain JSON lines): %.1f MiB\n", $dumpBytes / 1048576);
 $check('checksums in dump match live tables', array_map(fn ($x) => $x['sha256'], $manifest['tables']) === array_map(fn ($x) => $x['sha256'], $before));
 
+// The same dump in many tiny steps (as under web cron) must give identical table checksums.
+$stepped = $dumper->startDump();
+$stepStats = [];
+while (!$stepped['done']) {
+	$stepped = $dumper->dumpStep($repo, $stepped, microtime(true) + 0.05, $stepStats);
+}
+$sm = $dumper->manifest($stepped);
+printf("stepped dump: %d steps, consistent=%s\n", $stepped['steps'], json_encode($sm['consistent']));
+$check('stepped dump: same checksums as the one-shot dump', array_map(fn ($x) => $x['sha256'], $sm['tables']) === array_map(fn ($x) => $x['sha256'], $manifest['tables']));
+$check('stepped dump is marked as not fully consistent', $stepped['steps'] === 1 || $sm['consistent'] === false);
+
 // Second dump without changes: blobs are reused.
 $stats2 = ['newBlobs' => 0, 'dupBlobs' => 0, 'uploaded' => 0];
 $dumper->dump($repo, $stats2);
@@ -90,8 +103,10 @@ memory_reset_peak_usage();
 $t = microtime(true);
 $repo2 = Repository::open(new LocalBackend($repoDir), 'spike passphrase');
 $m = json_decode($repo2->getObject('db/1'), true, 512, JSON_THROW_ON_ERROR);
-$rows = $dumper->restore($repo2, $m);
-printf("restore: %d rows in %.1fs, peak %.1f MiB\n", $rows, microtime(true) - $t, memory_get_peak_usage() / 1048576);
+$report = [];
+$rows = $dumper->restore($repo2, $m, $report);
+printf("restore: %d rows in %.1fs, peak %.1f MiB, %d tables restored, %d unchanged skipped\n", $rows, microtime(true) - $t, memory_get_peak_usage() / 1048576, count($report['restored']), count($report['skipped']));
+$check('restore only rewrote the damaged tables', count($report['restored']) === count($changed));
 
 $mismatch = [];
 foreach ($tables as $tb) {
@@ -109,7 +124,8 @@ if ($mismatch) {
 // Sequences must be restored exactly (PostgreSQL), including one that ran ahead of the data.
 $seqAfter = $seqStates();
 $diff = array_filter(array_keys($seqBefore), fn ($k) => ($seqAfter[$k] ?? null) !== $seqBefore[$k]);
-$check(sprintf('all %d sequences restored exactly (filecache seq 50 ahead of data)', count($seqBefore)), $diff === [] && count($seqBefore) > 0);
+$isPg = $db->getDatabasePlatform() instanceof \Doctrine\DBAL\Platforms\PostgreSQLPlatform;
+$check(sprintf('all %d sequences restored exactly%s', count($seqBefore), $isPg ? ' (filecache seq 50 ahead of data)' : ' (n/a on this database)'), $diff === [] && (!$isPg || count($seqBefore) > 0));
 if ($diff) {
 	foreach (array_slice($diff, 0, 5) as $k) {
 		echo "$k before=" . json_encode($seqBefore[$k]) . ' after=' . json_encode($seqAfter[$k] ?? null) . "\n";

src/AdminSettings.vue

@@ -11,12 +11,23 @@
 		</NcSettingsSection>
 
 		<template v-if="status">
-			<KeySetup :status="status" @changed="refresh" />
-			<template v-if="status.key.confirmation">
-				<Locations :status="status" @changed="refresh" />
-				<Backups v-if="status.targets.length" :status="status" @changed="refresh" />
-				<RestoreBrowser v-if="status.targets.length" :status="status" @changed="refresh" />
+			<div class="ngb-tabs">
+				<NcButton :variant="tab === 'backup' ? 'primary' : 'secondary'" @click="tab = 'backup'">{{ t('ng_backup', 'Backup and restore') }}</NcButton>
+				<NcButton :variant="tab === 'settings' ? 'primary' : 'secondary'" @click="tab = 'settings'">{{ t('ng_backup', 'Settings') }}</NcButton>
+			</div>
+
+			<template v-if="tab === 'settings'">
+				<KeySetup :status="status" @changed="refresh" />
+				<Locations v-if="status.key.everConfirmed" :status="status" @changed="refresh" />
 			</template>
+			<template v-else-if="status.key.everConfirmed">
+				<template v-if="status.targets.length">
+					<Backups :status="status" @changed="refresh" />
+					<RestoreBrowser :status="status" @changed="refresh" />
+				</template>
+				<NcNoteCard v-else type="info">{{ t('ng_backup', 'Add a backup location under "Settings" first.') }}</NcNoteCard>
+			</template>
+			<NcNoteCard v-else type="warning">{{ t('ng_backup', 'Set up the backup key under "Settings" first.') }}</NcNoteCard>
 		</template>
 	</div>
 </template>
@@ -24,6 +35,7 @@
 <script setup>
 import { onBeforeUnmount, onMounted, ref } from 'vue'
 import { t } from '@nextcloud/l10n'
+import NcButton from '@nextcloud/vue/components/NcButton'
 import NcLoadingIcon from '@nextcloud/vue/components/NcLoadingIcon'
 import NcNoteCard from '@nextcloud/vue/components/NcNoteCard'
 import NcSettingsSection from '@nextcloud/vue/components/NcSettingsSection'
@@ -35,12 +47,20 @@ import RestoreBrowser from './components/RestoreBrowser.vue'
 
 const status = ref(null)
 const error = ref('')
+const tab = ref('settings')
+let tabInitialized = false
 let timer = null
 
 async function refresh() {
 	try {
 		status.value = await api.status()
 		error.value = ''
+		// Default to the daily-use tab once the key is set up; stay on Settings otherwise.
+		// Only decided on first load, so switching tabs ourselves isn't undone by polling.
+		if (!tabInitialized) {
+			tab.value = status.value.key.everConfirmed ? 'backup' : 'settings'
+			tabInitialized = true
+		}
 	} catch (e) {
 		error.value = e.message
 	}
@@ -59,4 +79,10 @@ onBeforeUnmount(() => clearTimeout(timer))
 .ng-backup :deep(.settings-section) {
 	max-width: 900px;
 }
+.ngb-tabs {
+	display: flex;
+	gap: 8px;
+	/* Same inline margin as NcSettingsSection, so the tabs line up with the section content */
+	margin: 0 calc(var(--default-grid-baseline) * 7) 12px;
+}
 </style>

src/api.js

@@ -17,13 +17,19 @@ async function call(method, path, data) {
 
 export default {
 	status: () => call('get', '/status'),
-	initKey: (passphrase) => call('post', '/key', { passphrase }),
+	initKey: (passphrase, deleteDelayDays, label) => call('post', '/key', { passphrase, deleteDelayDays, label }),
+	addSlot: (passphrase, label) => call('post', '/key/slots', { passphrase, label }),
+	replaceSlot: (slot, passphrase, label) => call('put', `/key/slots/${slot}`, { passphrase, label }),
+	removeSlot: (slot) => call('delete', `/key/slots/${slot}`),
+	trash: (targetId) => call('get', `/targets/${targetId}/trash`),
+	untrash: (targetId, snapshotId) => call('post', `/targets/${targetId}/trash/${snapshotId}`),
 	kitUrl: () => url('/key/kit'),
-	confirmKit: (accepted, phrase) => call('post', '/key/confirm', { accepted, phrase }),
+	confirmKit: (accepted, phrase, code) => call('post', '/key/confirm', { accepted, phrase, code }),
 	backends: () => call('get', '/backends'),
 	addTarget: (target) => call('post', '/targets', target),
 	removeTarget: (id) => call('delete', `/targets/${id}`),
 	testTarget: (id) => call('post', `/targets/${id}/test`),
+	setTargetLimit: (id, maxGb) => call('put', `/targets/${id}/limit`, { maxGb }),
 	startBackup: (targetId, label) => call('post', '/backups', { targetId, label }),
 	setSchedule: (time) => call('put', '/schedule', { time }),
 	snapshots: (targetId) => call('get', `/targets/${targetId}/snapshots`),