An unofficial open-source sync client for ProtonDrive on Linux — built as a native GTK4 desktop app using Proton's official SDK.
MVP release. Core sync workflows are complete and functional. Flathub submission is in progress.
- Authenticate with your Proton account via an embedded browser — no manual token management
- Set up one or more local folders to sync with ProtonDrive
- Two-way sync with conflict detection and automatic conflict copies
- Offline resilience — changes queue while offline and replay on reconnect
- Token expiry recovery — re-auth modal with queued change count, no data loss
- Error surfacing — disk full, permission denied, inotify limit exceeded, file locked
- Multi-pair management — add, remove, and manage multiple sync pairs independently
No native ProtonDrive sync client exists for Linux. Third-party tools either scrape the web API or go unmaintained. This client uses @protontech/drive-sdk — Proton's own SDK, the same one their CLI will use — so it stays compatible as the API evolves.
The embedded WebKitGTK auth approach (localhost callback) was validated directly with the Proton SDK team and confirmed as the canonical pattern for desktop clients.
Flatpak is the only supported installation method for the MVP.
flatpak install flathub io.github.ronki2304.ProtonDriveLinuxClientFlathub submission is pending. Until it lands, install from the bundle in GitHub Releases.
The Flatpak manifest requests broad filesystem access. This is a platform limitation: inotify (the Linux file-watching mechanism used for real-time sync) requires direct filesystem access — the XDG portal FUSE layer does not fire inotify events. This is a confirmed upstream limitation (xdg-desktop-portal #567), not a design choice. A full plain-language justification is in flatpak/PERMISSIONS.md.
Requirements: flatpak, flatpak-builder, GNOME Platform runtime 50.
git clone https://github.com/ronki2304/Linux_Proton_Drive
cd Linux_Proton_Drive
# Build and export to local repo
flatpak-builder --user --force-clean --disable-rofiles-fuse --repo=_repo builddir \
flatpak/io.github.ronki2304.ProtonDriveLinuxClient.yml
# Register the local repo (first time only)
flatpak remote-add --user --no-gpg-verify local-repo _repo
# Install and run
flatpak install --user --reinstall -y local-repo io.github.ronki2304.ProtonDriveLinuxClient
flatpak run io.github.ronki2304.ProtonDriveLinuxClient
--disable-rofiles-fuseis required in most Linux desktop environments — rootless containers and immutable distros typically lack FUSE mount permissions.
See CONTRIBUTING.md for the full development setup, two-terminal launch procedure, and test commands.
To follow engine activity in real time:
# Launch with debug logging enabled
PROTONDRIVE_DEBUG=1 flatpak run io.github.ronki2304.ProtonDriveLinuxClient
# In a second terminal
tail -f ~/.cache/protondrive/engine.logLog file is capped at 5 MB and rotates to engine.log.1. Tokens are never written to the log.
| Area | Status |
|---|---|
| Proton authentication (embedded WebKit + localhost callback) | ✅ |
| First sync pair setup wizard | ✅ |
| Two-way file sync engine | ✅ |
| Offline resilience & change queue | ✅ |
| Conflict detection & copy creation | ✅ |
| Conflict log & reveal in Files | ✅ |
| Token expiry recovery with queued-change count | ✅ |
| Actionable errors (disk full, permissions, inotify, file locked) | ✅ |
| Multi-pair management (add, remove, nesting/overlap validation) | ✅ |
| Missing local folder detection & recovery | ✅ |
| Flatpak manifest, AppStream metainfo, CI/CD pipelines | ✅ |
| Incremental reconciliation via SDK event stream | ✅ |
- System-browser auth — replace embedded WebKit with
Gio.AppInfo.launch_default_for_uri()for the Proton login flow. Improves hardware-key 2FA, password manager autofill, and enables aarch64 support (current WebKitGTK JIT instability on ARM64). Same localhost callback pattern, no server-side changes. - ARM Linux support — blocked on system-browser auth above.
- Selective sync — choose which remote subfolders to sync per pair, rather than syncing the full remote folder.
- Tray icon — background sync with system tray status indicator, without keeping the main window open.
- Per-pair parallel reconciliation — currently the engine reconciles all pairs sequentially and only starts queue processing after all pairs have finished their remote tree walk. Each pair should start uploading/downloading as soon as its own reconciliation is done, independent of other pairs.
- No automated integration tests — Proton's auth requires CAPTCHA; integration tests need a manually captured token (
PROTONDRIVE_DEBUG=1+secret-tool). Documented in CONTRIBUTING.md. - inotify watch limit — the Linux default of 8192 watches may be insufficient for very large sync folders. Increase with
fs.inotify.max_user_watches=524288in/etc/sysctl.d/. The app surfaces this as an actionable error. - Same-day conflict copies — if the same file produces two conflicts on the same calendar day, the second copy overwrites the first. Rare in practice; scheduled for post-MVP hardening.
- Draft-only nodes — if a file upload is interrupted after the remote node is created but before the first revision is committed, the node has no active revision. The engine auto-recovers via a two-pass lookup (typed listing, then unfiltered children walk). Manual deletion from ProtonDrive Web is only needed in the rare case where the SDK does not expose the draft node in any listing.
If you changed your Proton account password in the past, some folders may have their encryption keys sealed with the old key. The Linux client cannot decrypt them with your current credentials, so those folders show "Sync error" while others continue syncing normally.
Fix: Open drive.proton.me in your browser and navigate into the affected folder. Proton's web client automatically re-wraps the folder's key with your current account key. On the next sync cycle the error clears automatically — no restart needed.
GPL-3.0-only — see LICENSE. Bundles @protontech/drive-sdk (GPL-3.0) and openpgp (LGPL-3.0+).