feat(fuse,core,cli,gui): move another computer's backup to this one

A user switching from a Windows PC to Linux had two half answers:
adopting the old device makes this machine back up as it, and restoring
its folders keeps them in the old device's tree. Neither puts the data
under this machine's own device.

Device roots are separate shares on the main volume, so each top-level
folder of the other device can move under this device's root in one
server-side move. Nothing is uploaded again, and the other device stays
registered, without those folders.

- core: `Request::MigrateDevice { uid }` and
  `Db::sync_folder_set_share`
- fuse: `Core::migrate_device` moves every folder, suffixes a name
  already taken here with the other device's name, keeps going past a
  failed folder, and re-points sync folders that already tracked a
  moved folder at the new share
- cli: `pdfs devices migrate UID [--yes]` confirms, moves, then runs
  the ordinary restore picker
- gui: "Move to This Computer…" on another computer's row, followed by
  the restore picker
- i18n: translate the new strings in every catalog
- docs: CLI.md, USER_GUIDE.md, RECOVERY.md, ARCHITECTURE.md, changelog

Cargo.lock

@@ -3474,7 +3474,7 @@ checksum = "2ee67f1008b1ba2321834326597b8e186293b049a023cdef258527550b9935b4"
 
 [[package]]
 name = "pdfs-cli"
-version = "3.1.1"
+version = "3.1.2"
 dependencies = [
  "anyhow",
  "clap",
@@ -3490,7 +3490,7 @@ dependencies = [
 
 [[package]]
 name = "pdfs-core"
-version = "3.1.1"
+version = "3.1.2"
 dependencies = [
  "async-trait",
  "base64 0.23.1",
@@ -3516,7 +3516,7 @@ dependencies = [
 
 [[package]]
 name = "pdfs-fuse"
-version = "3.1.1"
+version = "3.1.2"
 dependencies = [
  "async-trait",
  "base64 0.23.1",
@@ -3538,7 +3538,7 @@ dependencies = [
 
 [[package]]
 name = "pdfs-gui"
-version = "3.1.1"
+version = "3.1.2"
 dependencies = [
  "anyhow",
  "async-channel",

Cargo.toml

@@ -3,7 +3,7 @@ resolver = "2"
 members = ["crates/pdfs-core", "crates/pdfs-fuse", "crates/pdfs-cli", "crates/pdfs-gui"]
 
 [workspace.package]
-version = "3.1.1"
+version = "3.1.2"
 edition = "2024"
 license = "MIT"
 authors = ["Nils Pukropp <contact@narl.io>"]

crates/pdfs-cli/src/main.rs

@@ -628,6 +628,15 @@ enum DeviceCmd {
         #[arg(long, conflicts_with = "uid")]
         clear: bool,
     },
+    /// Move another computer's folders into this computer's backup and sync
+    /// them here. The other computer stays registered, without those folders.
+    Migrate {
+        /// Device uid (from `devices list`).
+        uid: String,
+        /// Skip the confirmation and accept every proposed local path.
+        #[arg(long)]
+        yes: bool,
+    },
 }
 
 #[derive(Subcommand)]
@@ -967,6 +976,24 @@ fn cmd_devices(action: DeviceCmd) -> Result<()> {
             let uid = if clear { None } else { uid };
             ok_or_bail(control_request(CtlRequest::AdoptDevice { uid })?)?
         }
+        DeviceCmd::Migrate { uid, yes } => {
+            if !yes {
+                println!(
+                    "Every folder that device backs up moves into this computer's backup.\n\
+                     The device stays registered, without those folders. Stop Proton Drive\n\
+                     on that computer first, or it sees its folders disappear."
+                );
+                confirm("Move them here?")?;
+            }
+            let response = control_request(CtlRequest::MigrateDevice { uid })?;
+            // A script gets the one reply and runs `sync restore` itself.
+            if emit_json(&response)? {
+                return Ok(());
+            }
+            ok_or_bail(response)?;
+            // The folders are this device's now, so the plain restore offers them.
+            cmd_sync_restore(yes, None)?
+        }
     }
     Ok(())
 }

crates/pdfs-core/src/control.rs

@@ -446,6 +446,13 @@ pub enum Request {
     /// of registering a duplicate. `uid: None` clears the pin.
     /// Replies with [`Response::Ok`].
     AdoptDevice { uid: Option<String> },
+    /// Move every folder another device backs up into this machine's own
+    /// device, as server-side moves on the main volume. The other device stays
+    /// registered, without those folders. Sync folders here that already track
+    /// one of them follow it to its new share. Nothing is downloaded: the moved
+    /// folders are then offered by [`Request::ListRestorableFolders`].
+    /// Replies with [`Response::Ok`].
+    MigrateDevice { uid: String },
 
     // ---- device folder sync ----------------------------------
     /// Add a local folder to this machine's device, uploading its tree and
@@ -3082,6 +3089,9 @@ mod tests {
                 uid: Some("dev-1".into()),
             },
             Request::AdoptDevice { uid: None },
+            Request::MigrateDevice {
+                uid: "dev-2".into(),
+            },
             Request::ListRestorableFolders,
             Request::RestoreSyncFolders {
                 items: vec![RestoreItem {

crates/pdfs-core/src/db/sync.rs

@@ -139,6 +139,17 @@ impl Db {
         Ok(())
     }
 
+    /// Re-point a synced folder at the share that now holds its remote folder,
+    /// after the folder moved to another device without changing its uid.
+    pub fn sync_folder_set_share(&self, id: i64, share_id: &str) -> Result<()> {
+        let conn = self.conn.lock();
+        conn.execute(
+            "UPDATE sync_folder SET remote_share_id = ?2 WHERE id = ?1",
+            params![id, share_id],
+        )?;
+        Ok(())
+    }
+
     /// Queue (or, with `None`, withdraw) a mode the folder should move to once it
     /// is safe to switch.
     pub fn sync_folder_set_pending_mode(&self, id: i64, mode: Option<&str>) -> Result<()> {

crates/pdfs-core/src/db/tests.rs

@@ -4940,6 +4940,28 @@ fn pending_mode_is_queued_until_the_mode_is_reached() {
     assert_eq!(folder.pending_mode, None);
 }
 
+#[test]
+fn moved_sync_folder_points_at_its_new_share() {
+    let db = Db::open_in_memory().unwrap();
+    let id = db
+        .sync_folder_add("/tmp/pdfs-moved-share", "vol~folder", "windows-share")
+        .unwrap();
+    let other = db
+        .sync_folder_add("/tmp/pdfs-unmoved-share", "vol~other", "windows-share")
+        .unwrap();
+
+    db.sync_folder_set_share(id, "linux-share").unwrap();
+
+    let folder = db.sync_folder_get(id).unwrap().unwrap();
+    assert_eq!(folder.remote_share_id, "linux-share");
+    // A move keeps the uid, so nothing but the share changes.
+    assert_eq!(folder.remote_uid, "vol~folder");
+    assert_eq!(
+        db.sync_folder_get(other).unwrap().unwrap().remote_share_id,
+        "windows-share"
+    );
+}
+
 #[test]
 fn mode_commit_clears_only_the_intent_it_satisfies() {
     let db = Db::open_in_memory().unwrap();

crates/pdfs-fuse/src/control.rs

@@ -369,7 +369,7 @@ fn touched_topics(request: &CtlRequest) -> &'static [Topic] {
             RefreshScope::Photos { .. } => &[],
         },
         R::RenameDevice { .. } | R::DeleteDevice { .. } => &[Topic::Devices],
-        R::AdoptDevice { .. } => &[Topic::Devices, Topic::Locations],
+        R::AdoptDevice { .. } | R::MigrateDevice { .. } => &[Topic::Devices, Topic::Locations],
         R::AddSyncFolder { .. }
         | R::RemoveSyncFolder { .. }
         | R::SetSyncFolderMode { .. }
@@ -1297,6 +1297,10 @@ fn handle_control_conn(core: &Core, username: &str, mountpoint: &Path, stream: U
             Ok(message) => CtlResponse::Ok { message },
             Err(e) => CtlResponse::error(e),
         },
+        Ok(CtlRequest::MigrateDevice { uid }) => match core.migrate_device(&uid) {
+            Ok(message) => CtlResponse::Ok { message },
+            Err(e) => CtlResponse::error(e),
+        },
         Ok(CtlRequest::AddSyncFolder { local_path }) => {
             // Registering the device and uploading a folder tree far outlasts the
             // socket read timeout, so ack immediately and work on a background

crates/pdfs-fuse/src/devices.rs

@@ -19,6 +19,7 @@ use pdfs_core::control::{
 };
 use pdfs_core::db::{StoredDevice, StoredSyncFolder};
 use pdfs_core::mounts::MountMode;
+use pdfs_core::profile::PROFILE_DIR_NAME;
 use pdfs_core::{CoreError, CoreResult};
 use proton_drive_rs::proton_sdk::ids::{DeviceUid, NodeUid};
 use proton_drive_rs::{DeviceType, Node};
@@ -114,6 +115,22 @@ pub(crate) fn set_adopted_device_uid(uid: Option<&str>) -> CoreResult<()> {
         .map_err(|e| CoreError::internal(format!("write config: {e}")))
 }
 
+/// The name a folder moved in from `device` takes when `name` is already
+/// taken under this device's root, or `None` when it can keep its own.
+fn migrated_name(name: &str, device: &str, taken: &[String]) -> Option<String> {
+    let free = |candidate: &str| !taken.iter().any(|t| t == candidate);
+    if free(name) {
+        return None;
+    }
+    let base = format!("{name} ({device})");
+    if free(&base) {
+        return Some(base);
+    }
+    (2..)
+        .map(|n| format!("{base} {n}"))
+        .find(|candidate| free(candidate))
+}
+
 impl Core {
     // ---- devices ----------------------------------------------------------
 
@@ -260,6 +277,107 @@ impl Core {
         })
     }
 
+    /// Move every folder another device backs up into this machine's own
+    /// device, so this machine carries on backing them up as itself. The other
+    /// device stays registered, without those folders.
+    ///
+    /// Device roots all live on the main volume, so each folder is one
+    /// server-side move: nothing is downloaded or uploaded, and no quota is
+    /// used twice. A folder whose name is taken here keeps its content under
+    /// "<name> (<device>)". A failed folder does not stop the others, and a
+    /// second run picks up whatever is still left on the other device.
+    ///
+    /// Nothing is synced to this disk here. The moved folders are now this
+    /// device's, so the ordinary restore offers them. Only folders that were
+    /// already synced here from the other device are touched: their uid
+    /// survives the move but their share does not.
+    pub(crate) fn migrate_device(&self, uid: &str) -> CoreResult<String> {
+        let source = self.restore_source(Some(uid))?;
+        let target = self.ensure_device()?;
+        if source.uid == target.uid {
+            return Err(CoreError::invalid(format!(
+                "{} is this computer's own device",
+                source.name
+            )));
+        }
+        let bad_root = |d: &StoredDevice| {
+            parse_uid(&d.root_uid)
+                .ok_or_else(|| CoreError::internal(format!("bad device root uid: {}", d.root_uid)))
+        };
+        let (source_root, target_root) = (bad_root(&source)?, bad_root(&target)?);
+        if source_root.volume_id != target_root.volume_id {
+            return Err(CoreError::invalid(
+                "the two devices are on different Proton Drive volumes; copy it instead",
+            ));
+        }
+
+        let mut taken: Vec<String> = self
+            .device_root_nodes(&target_root)?
+            .into_iter()
+            .filter(|n| !n.trashed)
+            .map(|n| n.name)
+            .collect();
+        let synced = self
+            .db
+            .sync_folder_list()
+            .map_err(|e| CoreError::internal(format!("db: {e:?}")))?;
+
+        let mut moved = 0usize;
+        let mut renamed: Vec<String> = Vec::new();
+        let mut left: Vec<String> = Vec::new();
+        let mut failed: Vec<String> = Vec::new();
+        for node in self.device_root_nodes(&source_root)? {
+            if node.trashed || node.name == PROFILE_DIR_NAME {
+                continue;
+            }
+            // A device root only ever holds folders (B68); anything else was
+            // put there by hand and is left for the user to deal with.
+            if !node.is_folder() {
+                left.push(node.name);
+                continue;
+            }
+            let new_name = migrated_name(&node.name, &source.name, &taken);
+            if let Err(e) = self.move_rename_remote(&node.uid, &target_root, new_name.as_deref()) {
+                warn!(name = %node.name, error = %e, "migrate: could not move folder");
+                failed.push(format!("{}: {e}", node.name));
+                continue;
+            }
+            let landed = new_name.clone().unwrap_or_else(|| node.name.clone());
+            if new_name.is_some() {
+                renamed.push(format!("{} -> {landed}", node.name));
+            }
+            taken.push(landed);
+            moved += 1;
+
+            let uid = node.uid.to_string();
+            for folder in synced.iter().filter(|f| f.remote_uid == uid) {
+                if let Err(e) = self.db.sync_folder_set_share(folder.id, &target.share_id) {
+                    warn!(id = folder.id, error = ?e, "migrate: could not re-point sync folder");
+                }
+                self.sync_now(Some(folder.id));
+            }
+        }
+        self.invalidate_children_of(&source_root);
+        self.invalidate_children_of(&target_root);
+
+        let mut message = format!("moved {moved} folder(s) from {}", source.name);
+        if !renamed.is_empty() {
+            message.push_str(&format!("; renamed: {}", renamed.join(", ")));
+        }
+        if !left.is_empty() {
+            message.push_str(&format!("; left behind: {}", left.join(", ")));
+        }
+        if !failed.is_empty() {
+            message.push_str(&format!("; failed: {}", failed.join(", ")));
+        }
+        info!(from = %source.name, to = %target.name, moved, failed = failed.len(),
+            "device migrated");
+        if moved == 0 && !failed.is_empty() {
+            return Err(CoreError::conflict(message));
+        }
+        Ok(message)
+    }
+
     // ---- device folder sync -------------------------
 
     /// Auto-register (or recover) this machine as a Proton Drive Device, caching
@@ -360,21 +478,25 @@ impl Core {
         root_uid: &NodeUid,
         name: &str,
     ) -> CoreResult<Option<NodeUid>> {
+        Ok(self
+            .device_root_nodes(root_uid)?
+            .into_iter()
+            .find(|n| n.is_folder() && !n.trashed && n.name == name)
+            .map(|n| n.uid))
+    }
+
+    /// Everything directly under a device root, trashed nodes included.
+    fn device_root_nodes(&self, root_uid: &NodeUid) -> CoreResult<Vec<Node>> {
         let uids = self
             .rt
             .block_on(self.drive.enumerate_folder_children_node_uids(root_uid))
             .map_err(|e| CoreError::from_api(&e, "list device root"))?;
         if uids.is_empty() {
-            return Ok(None);
+            return Ok(Vec::new());
         }
-        let nodes = self
-            .rt
+        self.rt
             .block_on(self.drive.enumerate_nodes(&uids))
-            .map_err(|e| CoreError::from_api(&e, "resolve device root children"))?;
-        Ok(nodes
-            .into_iter()
-            .find(|n| n.is_folder() && !n.trashed && n.name == name)
-            .map(|n| n.uid))
+            .map_err(|e| CoreError::from_api(&e, "resolve device root children"))
     }
 
     /// Add a local folder to this device's sync set: register the device if
@@ -1107,10 +1229,38 @@ mod tests {
     use pdfs_core::db::StoredSyncFolder;
 
     use super::{
-        ApplicableMountMode, commit_after_teardown, pending_intent_matches,
+        ApplicableMountMode, commit_after_teardown, migrated_name, pending_intent_matches,
         restore_snapshot_matches, select_mode_transition,
     };
 
+    #[test]
+    fn migrated_folder_keeps_its_name_when_it_is_free() {
+        let taken = vec!["Pictures".to_string()];
+        assert_eq!(migrated_name("Documents", "DESKTOP-1", &taken), None);
+    }
+
+    #[test]
+    fn migrated_folder_is_named_after_its_device_on_a_clash() {
+        let taken = vec!["Documents".to_string()];
+        assert_eq!(
+            migrated_name("Documents", "DESKTOP-1", &taken).as_deref(),
+            Some("Documents (DESKTOP-1)")
+        );
+    }
+
+    #[test]
+    fn migrated_folder_is_numbered_when_the_device_name_is_taken_too() {
+        let taken = vec![
+            "Documents".to_string(),
+            "Documents (DESKTOP-1)".to_string(),
+            "Documents (DESKTOP-1) 2".to_string(),
+        ];
+        assert_eq!(
+            migrated_name("Documents", "DESKTOP-1", &taken).as_deref(),
+            Some("Documents (DESKTOP-1) 3")
+        );
+    }
+
     #[test]
     fn unknown_mode_cannot_select_a_destructive_transition() {
         let mut unmounts = 0;

crates/pdfs-gui/src/app/main.rs

@@ -202,12 +202,20 @@ impl Ui {
 }
 
 fn main() -> glib::ExitCode {
-    tracing_subscriber::fmt()
-        .with_env_filter(
-            tracing_subscriber::EnvFilter::try_from_default_env().unwrap_or_else(|_| "info".into()),
-        )
-        .init();
+    let verify = std::env::args().nth(1).as_deref() == Some(VERIFY_ARG);
+    let logs = tracing_subscriber::fmt().with_env_filter(
+        tracing_subscriber::EnvFilter::try_from_default_env().unwrap_or_else(|_| "info".into()),
+    );
+    // The verification window's stdout carries its token back to the app.
+    if verify {
+        logs.with_writer(std::io::stderr).init();
+    } else {
+        logs.init();
+    }
     i18n::init();
+    if verify {
+        return run_verification_window();
+    }
 
     // The tray launches the app with arguments ("--page locations",
     // "--confirm-stop"), which a running instance must receive too.
@@ -303,6 +311,11 @@ fn build_window(app: &adw::Application) {
             return;
         }
     };
+    // On a fresh install the daemon has not run yet to make these, and the
+    // Takeout page keeps its staged archives in the state dir (B194).
+    if let Err(e) = dirs.ensure() {
+        tracing::warn!("cannot create the app's directories: {e}");
+    }
 
     let stack = adw::ViewStack::new();
     let (login_page, login_widgets) = build_login_page();

crates/pdfs-gui/src/app/pages/devices.rs

@@ -439,6 +439,10 @@ fn other_computer_row(ui: &Rc<Ui>, dev: &DeviceInfo) -> adw::ActionRow {
     menu.item(&gettext("Restore to This Computer…"), move || {
         prompt_restore_folders(&ui_c, Some((uid_c.clone(), name_c.clone())))
     });
+    let (ui_c, uid_c, name_c) = (ui.clone(), uid.clone(), name.clone());
+    menu.item(&gettext("Move to This Computer…"), move || {
+        prompt_migrate_device(&ui_c, &uid_c, &name_c)
+    });
     menu.section();
     let (ui_c, uid_c, name_c) = (ui.clone(), uid.clone(), name.clone());
     menu.item(&gettext("Rename…"), move || {
@@ -1096,6 +1100,67 @@ pub(crate) fn prompt_adopt_device(ui: &Rc<Ui>, uid: &str, name: &str) {
     dialog.present(win.as_ref());
 }
 
+/// Ask before moving another computer's folders into this computer's backup,
+/// then offer them for syncing here.
+///
+/// Destructive-looking on purpose: the other computer keeps its device but
+/// loses its folders, and a copy of Proton Drive still running there would
+/// watch them vanish.
+pub(crate) fn prompt_migrate_device(ui: &Rc<Ui>, uid: &str, name: &str) {
+    let win = ui_window(ui);
+    let dialog = adw::AlertDialog::builder()
+        .heading(gettext("Move Backup to This Computer?"))
+        // Translators: {name} is the name of the other computer whose folders move to this one.
+        .body(gettext_f(
+            "The folders backed up by “{name}” move into this computer's backup in Proton Drive, and you choose where they go on this computer. “{name}” stays in your account, without those folders.\n\nStop Proton Drive on “{name}” first. Otherwise it sees its folders disappear.",
+            &[("name", name)],
+        ))
+        .build();
+    dialog.add_response("cancel", &gettext("Cancel"));
+    dialog.add_response("move", &gettext("Move Here"));
+    dialog.set_response_appearance("move", adw::ResponseAppearance::Destructive);
+    dialog.set_default_response(Some("cancel"));
+    dialog.set_close_response("cancel");
+    let ui = ui.clone();
+    let uid = uid.to_string();
+    // Translators: {name} is the name of the computer whose folders moved to this one.
+    let done = gettext_f("Moved the backup of “{name}”", &[("name", name)]);
+    dialog.connect_response(None, move |_, resp| {
+        if resp != "move" {
+            return;
+        }
+        ui.busy_begin();
+        let rx = spawn_request(
+            ui.dirs.control_socket(),
+            Request::MigrateDevice { uid: uid.clone() },
+        );
+        let (ui, done) = (ui.clone(), done.clone());
+        glib::spawn_future_local(async move {
+            let result = rx.recv().await;
+            ui.busy_end();
+            let failed = gettext("Couldn't move that backup");
+            match result {
+                Ok(Ok(Response::Ok { .. })) => {
+                    reload_sync_pages(&ui);
+                    toast(&ui, &done);
+                    // The folders are this computer's now, so its own restore
+                    // picker is where the user chooses their local paths.
+                    prompt_restore_folders(&ui, None);
+                }
+                Ok(Ok(Response::Error { message, kind })) => {
+                    toast_failure(&ui, &failed, &message, kind)
+                }
+                _ => toast_error(
+                    &ui,
+                    &failed,
+                    &gettext("The Proton Drive service didn't respond."),
+                ),
+            }
+        });
+    });
+    dialog.present(win.as_ref());
+}
+
 /// Run a mutation raised from Computers or Locations and reload the page on success.
 pub(crate) fn run_devices_mutation(ui: &Rc<Ui>, req: Request, done: &str, failed: &str) {
     ui.busy_begin();

crates/pdfs-gui/src/app/pages/login.rs

@@ -150,15 +150,27 @@ pub(crate) fn wire_login(ui: &Rc<Ui>) {
         });
 
         // Same shape for human verification: only fires when the API gates the
-        // sign-in, and the worker is blocked on the token until it does.
+        // sign-in, and the worker is blocked on the token until it does. A
+        // window that never came up is told apart from one the user closed, so
+        // the result below can say why the sign-in stopped.
         let ui_hv = ui.clone();
+        let verification_failed = Rc::new(Cell::new(false));
+        let hv_failed = verification_failed.clone();
         glib::spawn_future_local(async move {
             if let Ok((url, token_tx)) = hv_req_rx.recv().await {
                 ui_hv
                     .login
                     .login_status
                     .set_text(&gettext("Complete the verification to continue…"));
-                prompt_human_verification(&ui_hv, &url, token_tx);
+                // Anything but a token drops the sender, which the worker reads
+                // as a cancelled sign-in.
+                match verify_human(url).await {
+                    Verification::Solved(token) => {
+                        let _ = token_tx.send(token);
+                    }
+                    Verification::Cancelled => {}
+                    Verification::Failed => hv_failed.set(true),
+                }
             }
         });
 
@@ -194,6 +206,9 @@ pub(crate) fn wire_login(ui: &Rc<Ui>) {
                     let _ = gio::spawn_blocking(service::enable_start).await;
                     refresh(&ui);
                 }
+                Err(_) if verification_failed.get() => ui.login.login_status.set_text(&gettext(
+                    "The verification page couldn't be opened, so the sign-in was cancelled. Your system may keep the web view's sandbox from starting; the troubleshooting guide explains what to do.",
+                )),
                 Err(e) => ui.login.login_status.set_text(&e),
             }
         });

crates/pdfs-gui/src/app/pages/verify.rs

@@ -1,4 +1,4 @@
-//! The human-verification (CAPTCHA) dialog.
+//! The human-verification (CAPTCHA) window.
 //!
 //! Proton gates logins it does not recognise — a new IP, a VPN exit — behind a
 //! CAPTCHA. The API answers the login with a challenge instead of a session, and
@@ -8,10 +8,26 @@
 //! The page is hosted in a `WebKitWebView` rather than handed to the system
 //! browser because it reports completion by posting a message to its host, not
 //! by redirecting: a browser has nowhere to post it back to.
+//!
+//! The webview runs in a child `pdfs-app` started with [`VERIFY_ARG`], not in the
+//! app itself. WebKit aborts its whole process when its sandbox cannot start, as
+//! on hardened systems that keep bubblewrap from the journal socket
+//! (`docs/BUGS.md` B195); in a child that costs the verification, not the app.
+//! The URL goes to the child on stdin, so it never shows in a process list, and
+//! the token comes back on stdout.
 
 use crate::*;
+use std::io::{BufRead, BufReader, Write as _};
+use std::process::{ExitStatus, Stdio};
 use webkit6::prelude::*;
 
+/// The argument that makes `pdfs-app` the verification window instead of the app.
+pub(crate) const VERIFY_ARG: &str = "--human-verification";
+
+/// Marks the token among whatever else lands on the child's stdout: GLib and
+/// WebKit write debug output there.
+const TOKEN_PREFIX: &str = "hv-token ";
+
 /// Bridge the verification page's `postMessage` to a handler this side can read.
 ///
 /// The page targets its embedding host (`window.parent`), which in a webview is
@@ -26,15 +42,100 @@ window.addEventListener('message', function (event) {
 });
 "#;
 
-/// Present the challenge and hand the solved token back through `token_tx`.
-///
-/// Closing the dialog without solving drops the sender, which the waiting login
-/// worker reads as a cancelled sign-in — the same contract as the 2FA prompt.
-pub(crate) fn prompt_human_verification(
-    ui: &Rc<Ui>,
-    url: &str,
-    token_tx: std::sync::mpsc::Sender<String>,
-) {
+/// How the verification window ended.
+#[derive(Debug, PartialEq, Eq)]
+pub(crate) enum Verification {
+    Solved(String),
+    /// Closed without solving.
+    Cancelled,
+    /// Never came up, or died: most likely WebKit could not start its sandbox.
+    Failed,
+}
+
+/// Show the challenge in the verification window and wait until it closes.
+pub(crate) async fn verify_human(url: String) -> Verification {
+    match gio::spawn_blocking(move || run_verification_child(&url)).await {
+        Ok(Ok(verification)) => verification,
+        Ok(Err(e)) => {
+            tracing::error!("cannot run the verification window: {e}");
+            Verification::Failed
+        }
+        Err(_) => Verification::Failed,
+    }
+}
+
+fn run_verification_child(url: &str) -> std::io::Result<Verification> {
+    let mut child = Command::new(own_exe())
+        .arg(VERIFY_ARG)
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .spawn()?;
+    if let Some(mut stdin) = child.stdin.take() {
+        // A failed write means the child is already gone; its exit status says
+        // how. Dropping `stdin` closes it.
+        let _ = writeln!(stdin, "{url}");
+    }
+    // Stops reading at the token rather than at EOF: WebKit's helper processes
+    // inherit the pipe and may hold it open a moment after the child quits.
+    let token = child
+        .stdout
+        .take()
+        .and_then(|out| find_token(BufReader::new(out)));
+    let status = child.wait()?;
+    Ok(outcome(token, status))
+}
+
+/// This very binary, so a development build opens its own window. After an
+/// upgrade replaced the file, `current_exe` names a deleted path, and the
+/// installed `pdfs-app` is the next best.
+fn own_exe() -> PathBuf {
+    std::env::current_exe()
+        .ok()
+        .filter(|path| path.is_file())
+        .unwrap_or_else(|| PathBuf::from("pdfs-app"))
+}
+
+fn find_token(out: impl BufRead) -> Option<String> {
+    out.lines()
+        .map_while(Result::ok)
+        .find_map(|line| line.strip_prefix(TOKEN_PREFIX).map(str::to_owned))
+}
+
+/// A token wins over the exit status: the user solved the page, even if
+/// WebKit's teardown crashed after it.
+fn outcome(token: Option<String>, status: ExitStatus) -> Verification {
+    match token {
+        Some(token) => Verification::Solved(token),
+        None if status.success() => Verification::Cancelled,
+        None => {
+            tracing::error!(%status, "the verification window failed");
+            Verification::Failed
+        }
+    }
+}
+
+/// Run as the verification window: read the page's URL from stdin, show it, and
+/// print the token once the user has solved it. Closing the window exits
+/// without a token, which the app reads as a cancelled sign-in.
+pub(crate) fn run_verification_window() -> glib::ExitCode {
+    let mut url = String::new();
+    if std::io::stdin().lock().read_line(&mut url).is_err() || url.trim().is_empty() {
+        tracing::error!("{VERIFY_ARG} expects the verification URL on stdin");
+        return glib::ExitCode::FAILURE;
+    }
+    let url = url.trim().to_owned();
+
+    // Not unique: the app that started it already holds APP_ID.
+    let app = adw::Application::builder()
+        .flags(gio::ApplicationFlags::NON_UNIQUE)
+        .build();
+    app.connect_activate(move |app| build_verification_window(app, &url));
+    // GApplication would refuse VERIFY_ARG as an unknown option.
+    let argv0 = std::env::args().next().unwrap_or_default();
+    app.run_with_args(&[argv0])
+}
+
+fn build_verification_window(app: &adw::Application, url: &str) {
     let content = webkit6::UserContentManager::new();
     content.add_script(&webkit6::UserScript::new(
         BRIDGE,
@@ -53,24 +154,19 @@ pub(crate) fn prompt_human_verification(
         .hexpand(true)
         .build();
 
-    let dialog = adw::Dialog::builder()
+    let body = gtk4::Box::new(gtk4::Orientation::Vertical, 0);
+    body.append(&adw::HeaderBar::new());
+    body.append(&webview);
+    let window = adw::ApplicationWindow::builder()
+        .application(app)
         .title(gettext("Verification"))
-        .content_width(420)
-        .content_height(560)
+        .icon_name(APP_ID)
+        .default_width(420)
+        .default_height(560)
+        .content(&body)
         .build();
 
-    let header = adw::HeaderBar::new();
-    let body = gtk4::Box::new(gtk4::Orientation::Vertical, 0);
-    body.append(&header);
-    body.append(&webview);
-    dialog.set_child(Some(&body));
-
-    // Taken on the first success *or* on close, so the token is sent at most
-    // once and a cancelled dialog always drops the sender.
-    let token_tx = Rc::new(RefCell::new(Some(token_tx)));
-
-    let tx = token_tx.clone();
-    let dlg_weak = dialog.downgrade();
+    let app = app.downgrade();
     content.connect_script_message_received(Some("hv"), move |_, value| {
         let Some(token) = extract_token(&value.to_str()) else {
             // Every `postMessage` on the page reaches here, most of them the
@@ -78,25 +174,17 @@ pub(crate) fn prompt_human_verification(
             // is simply not ours.
             return;
         };
-        if let Some(tx) = tx.borrow_mut().take() {
-            let _ = tx.send(token);
+        let mut stdout = std::io::stdout().lock();
+        if let Err(e) = writeln!(stdout, "{TOKEN_PREFIX}{token}").and_then(|()| stdout.flush()) {
+            tracing::error!("cannot hand the verification token back: {e}");
         }
-        if let Some(dlg) = dlg_weak.upgrade() {
-            dlg.close();
+        if let Some(app) = app.upgrade() {
+            app.quit();
         }
     });
 
-    // Covers the close button, Escape, and the user giving up.
-    dialog.connect_closed(move |_| {
-        token_tx.borrow_mut().take();
-    });
-
     webview.load_uri(url);
-
-    let parent = ui.login.login_button.root().and_downcast::<gtk4::Window>();
-    // Returns immediately; the login worker stays blocked on the channel until
-    // the handler above sends, or the dialog closes and drops the sender.
-    dialog.present(parent.as_ref());
+    window.present();
 }
 
 /// Pull the verification token out of a message posted by the verification page.
@@ -133,7 +221,12 @@ fn extract_token(raw: &str) -> Option<String> {
 
 #[cfg(test)]
 mod tests {
-    use super::extract_token;
+    use super::{Verification, extract_token, find_token, outcome};
+    use std::os::unix::process::ExitStatusExt as _;
+    use std::process::ExitStatus;
+
+    /// The wait status of a process killed by SIGABRT.
+    const ABORTED: i32 = 6;
 
     #[test]
     fn a_completion_message_yields_its_token() {
@@ -163,4 +256,39 @@ mod tests {
             assert!(extract_token(raw).is_none(), "accepted: {raw}");
         }
     }
+
+    #[test]
+    fn the_token_is_found_among_other_output() {
+        let out = "Gtk-Message: something\nhv-token tok-1\nmore\n";
+        assert_eq!(find_token(out.as_bytes()).as_deref(), Some("tok-1"));
+        assert_eq!(find_token("only chatter\n".as_bytes()), None);
+    }
+
+    #[test]
+    fn a_window_closed_without_a_token_cancels() {
+        assert_eq!(
+            outcome(None, ExitStatus::from_raw(0)),
+            Verification::Cancelled
+        );
+    }
+
+    /// WebKit aborts when its sandbox cannot start (B195). That must read as a
+    /// failure the app explains, not as the user giving up.
+    #[test]
+    fn a_window_that_died_fails() {
+        assert_eq!(
+            outcome(None, ExitStatus::from_raw(ABORTED)),
+            Verification::Failed
+        );
+        let exited_1 = ExitStatus::from_raw(1 << 8);
+        assert_eq!(outcome(None, exited_1), Verification::Failed);
+    }
+
+    #[test]
+    fn a_token_counts_even_if_the_window_died_after_it() {
+        assert_eq!(
+            outcome(Some("tok-1".into()), ExitStatus::from_raw(ABORTED)),
+            Verification::Solved("tok-1".into())
+        );
+    }
 }

crates/pdfs-gui/src/main.rs

@@ -485,6 +485,10 @@ fn main() -> Result<()> {
         return Ok(());
     }
 
+    // The socket lives in the state dir, which nothing has made yet when the app
+    // starts the tray on a fresh install (B194).
+    dirs.ensure().context("create the app's directories")?;
+
     // Ensure only one instance of the tray runs.
     let tray_sock = dirs.tray_socket();
     if std::os::unix::net::UnixStream::connect(&tray_sock).is_ok() {

docs/ARCHITECTURE.md

@@ -377,6 +377,12 @@ Restore lists the device's folders, proposes a local path from the profile, and
 adds a synced folder bound to the remote uid. The download is an ordinary pass against an empty
 baseline. The user side is in [RECOVERY.md](RECOVERY.md).
 
+`Core::migrate_device` moves another device's top-level folders under this machine's device root.
+Device roots are separate shares on the main volume, so each folder is one server-side move that
+keeps its uid. A name already taken here gets the other device's name as a suffix. A synced folder
+that already tracked one of them keeps its `remote_uid` and only has its `remote_share_id`
+re-pointed. The moved folders are then offered by the ordinary restore.
+
 ---
 
 ## 8. Control protocol
@@ -542,7 +548,7 @@ sequenceDiagram
     actor User
     participant UI as pdfs-app
     participant Auth as pdfs-core auth
-    participant Web as WebKitGTK dialog
+    participant Web as pdfs-app --human-verification
     participant API as Proton API
 
     User->>UI: email and password
@@ -550,9 +556,9 @@ sequenceDiagram
     Auth->>API: SRP handshake
     API-->>Auth: 9001, challenge URL
     Auth-->>UI: HumanVerificationRequired
-    UI->>Web: load challenge
+    UI->>Web: challenge URL (stdin)
     User->>Web: solve it
-    Web-->>UI: token (postMessage)
+    Web-->>UI: token (stdout)
     UI->>Auth: login_verified(token)
     Auth->>API: new SRP handshake with the token
     API-->>Auth: session
@@ -561,6 +567,9 @@ sequenceDiagram
 - The challenge used up the first SRP handshake, so the retry starts a new one with the token
   attached.
 - The page may post the token as an object or as a JSON string; both are accepted.
+- The page runs in a WebKitGTK view inside a child `pdfs-app`. WebKit aborts its process when its
+  sandbox cannot start, as on hardened systems such as secureblue (B195). In the child, that ends
+  the verification, and the app says why, instead of closing the app.
 - The CLI has no web view. It fails with a message to sign in once with `pdfs-app`; the stored
   session then works for the CLI and the service.
 

docs/BUGS.md

@@ -47,7 +47,7 @@ original wording.
    it in the index in the same change.
 
 ```markdown
-### B194 — What the user sees, in one line
+### B196 — What the user sees, in one line
 
 **Status:** Open
 **Found:** 2026-10-06, how it was found
@@ -100,6 +100,7 @@ a live account since.
 
 | Entry | Title |
 |---|---|
+| [B195](#b195--the-app-crashes-when-proton-asks-for-a-captcha-on-secureblue) | The app crashes when Proton asks for a CAPTCHA on secureblue |
 | [B193](#b193--deleting-a-file-whose-create-failed-can-trash-a-file-of-the-users-on-drive) | Deleting a file whose create failed can trash a file of the user's on Drive |
 | [B191](#b191--a-file-deleted-after-its-create-failed-and-was-written-again-can-stay-on-drive) | A file deleted after its create failed and was written again can stay on Drive |
 | [B190](#b190--a-file-saved-just-before-the-daemon-stops-can-keep-its-old-content-on-drive) | A file saved just before the daemon stops can keep its old content on Drive |
@@ -214,6 +215,7 @@ a live account since.
 
 | Entry | Title |
 |---|---|
+| [B194](#b194--on-a-fresh-install-the-tray-exits-and-the-takeout-page-cannot-remember-its-archives) | On a fresh install the tray exits and the Takeout page cannot remember its archives |
 | [B192](#b192--a-new-file-closed-empty-reaches-drive-only-half-a-minute-later) | A new file closed empty reaches Drive only half a minute later |
 | [B181](#b181--the-app-shows-a-queued-edit-kept-as-a-conflict-copy-in-english) | The app shows a queued edit kept as a conflict copy in English |
 | [B180](#b180--a-stop-waits-10-s-for-a-drain-worker-that-slept-through-it) | A stop waits 10 s for a drain worker that slept through it |
@@ -296,6 +298,60 @@ a live account since.
 
 Newest first.
 
+### B195 — The app crashes when Proton asks for a CAPTCHA on secureblue
+
+**Status:** Fixed (unverified). Nobody has run the fix on secureblue yet.
+**Found:** 2026-10-07, [#29](https://github.com/narrrl/proton-drive-linux/issues/29). On
+secureblue 44 (a hardened Fedora Atomic), `pdfs-app` aborted a few seconds after the sign-in, with
+`bwrap: Can't get type of source /run/systemd/journal/socket: Permission denied` and
+`Failed to fully launch dbus-proxy`.
+**Where:** `crates/pdfs-gui/src/app/pages/verify.rs`, `crates/pdfs-gui/src/app/pages/login.rs`
+
+**Repro:** Sign in on secureblue from a network Proton asks a CAPTCHA for, such as a VPN.
+
+**Cause.** The CAPTCHA page runs in a WebKitGTK view (B8). Before it loads anything, WebKit starts
+its sandbox: bubblewrap, with the journal socket bound in, and `xdg-dbus-proxy`. secureblue keeps
+bubblewrap from the socket, the proxy does not start, and WebKit ends its process with `g_error`.
+The view was in the app's own process, so the whole app went down, and nothing in our code can
+catch that.
+
+**Fix.** The view runs in a child, `pdfs-app --human-verification`, that reads the URL on stdin
+and prints the token on stdout. A child that exits without a token after a crash or a non-zero
+status ends the sign-in with a message that says the page could not be opened. TROUBLESHOOTING.md
+gives the cause and a one-time workaround. The sandbox is not switched off by the app: users choose
+a hardened system for that isolation.
+
+**Test:** unit tests `a_window_that_died_fails`, `a_window_closed_without_a_token_cancels`,
+`a_token_counts_even_if_the_window_died_after_it` and `the_token_is_found_among_other_output`.
+On 2026-10-08 the child ran under real WebKit on Arch against a local page that posts a completion,
+and handed back its token.
+
+---
+
+### B194 — On a fresh install the tray exits and the Takeout page cannot remember its archives
+
+**Status:** Fixed.
+**Found:** 2026-10-07, in the log of [#29](https://github.com/narrrl/proton-drive-linux/issues/29):
+`failed to bind tray single-instance socket: No such file or directory` and
+`cannot remember staged Takeout archives: No such file or directory`.
+**Where:** `crates/pdfs-gui/src/main.rs`, `build_window` in `crates/pdfs-gui/src/app/main.rs`
+
+**Repro:** Start `pdfs-app` with no `~/.local/state/proton-drive-linux`, as on a fresh install. The
+tray is gone, and staging a Takeout archive logs the warning.
+
+**Cause.** Both write to the state directory, and only the daemon and the CLI made it
+(`AppDirs::ensure`). The app starts the tray before the first sign-in, so before the daemon has
+ever run.
+
+**Fix.** `pdfs-tray` and `pdfs-app` call `AppDirs::ensure` at start, which also makes the
+directories owner-only (B6).
+
+**Verified:** 2026-10-08, `pdfs-tray` with `XDG_STATE_HOME`, `XDG_CONFIG_HOME` and
+`XDG_CACHE_HOME` pointing at an empty directory. It exited with the error before the fix, and
+afterwards ran with `tray.sock` in a `0700` state directory.
+
+---
+
 ### B193 — Deleting a file whose create failed can trash a file of the user's on Drive
 
 **Status:** Fixed (unverified).

docs/CHANGELOG.md

@@ -11,6 +11,43 @@ scratch (user data in `staging/` and `recovery/` is never touched by this).
 
 ## [Unreleased]
 
+### Added
+- **Move another computer's backup to this one.** **Move to This Computer…** on the Computers page,
+  or `pdfs devices migrate UID`, moves every folder another computer backs up, for example an old
+  Windows PC, into this computer's backup on Proton Drive. Then it offers them for syncing here. The
+  folders move on Proton Drive itself, so nothing is uploaded again. The other computer stays in the
+  account, without those folders.
+
+## [3.1.2] — 2026-10-08
+
+Schema: **42**, unchanged.
+
+### Fixed
+- **The app crashed when Proton asked for a CAPTCHA on hardened systems.** On secureblue, WebKit
+  cannot start the sandbox for the verification page and ends its process, which took the app
+  down with it. The page now opens in a separate window process: if that process fails, the
+  sign-in stops with a message that says why, and TROUBLESHOOTING.md has a workaround.
+  ([#29](https://github.com/narrrl/proton-drive-linux/issues/29))
+- **On a fresh install the tray icon did not start.** The tray and the app now create their state
+  directory themselves instead of waiting for the service to do it. This also lets the Takeout
+  page remember staged archives before the first mount.
+  ([#29](https://github.com/narrrl/proton-drive-linux/issues/29))
+
+## [3.1.1] — 2026-10-07
+
+Schema: **42**, unchanged.
+
+### Changed
+- **The client identifies itself with its release.** Sign-in and every API call used to send the
+  fixed `external-drive-linux@0.1.0-alpha` and `proton-drive-linux/0.1.0`. If Proton retired that
+  version, every release would fail to sign in at once and no update could fix it. The client now
+  sends `external-drive-linux@<version>-stable` and `proton-drive-linux/<version>`. `app_version`
+  and `user_agent` in `config.json` are optional overrides now. The fixed values that releases up
+  to 3.1.0 wrote there count as unset and are removed on the next save. A value you set by hand is
+  kept.
+- The About dialog shows the release version, and its debug info shows the identity that is
+  actually sent.
+
 ## [3.1.0] — 2026-10-07
 
 Schema: **42**, unchanged.
@@ -1635,6 +1672,12 @@ First stable release: FUSE files-on-demand mount, sync daemon under `proton-driv
 - The outstanding FUSE defects tracked in `docs/BUGS.md`, plus a truncate defect, validated
   by a new POSIX compliance suite for the filesystem.
 
+[3.1.2]: https://github.com/narrrl/proton-drive-linux/releases/tag/v3.1.2
+
+[3.1.1]: https://github.com/narrrl/proton-drive-linux/releases/tag/v3.1.1
+
+[3.1.0]: https://github.com/narrrl/proton-drive-linux/releases/tag/v3.1.0
+
 [3.0.0]: https://github.com/narrrl/proton-drive-linux/releases/tag/v3.0.0
 
 [2.10.0]: https://github.com/narrrl/proton-drive-linux/releases/tag/v2.10.0

docs/CLI.md

@@ -103,6 +103,7 @@ commands are for scripts and for cases where the mount is not available.
 | `pdfs devices rename UID NAME` | Rename a computer. |
 | `pdfs devices rm UID` | Remove a computer and its backup from the account. |
 | `pdfs devices adopt UID` | Make this machine continue another computer's backup, for example after a reinstall. `--clear` returns to matching by hostname. |
+| `pdfs devices migrate UID [--yes]` | Move another computer's folders into this computer's backup, then restore them here like `pdfs sync restore`. The other computer stays registered, without those folders. `--yes` skips the confirmation and accepts every proposed path. See [RECOVERY.md](RECOVERY.md). |
 
 ## Trash
 

docs/RECOVERY.md

@@ -133,6 +133,29 @@ pdfs sync restore --device UID
 The folders stay part of the other computer's backup and sync in both directions. This machine
 does not take over that computer's backup.
 
+### Moving another computer's backup here
+
+To switch computers for good, for example from a Windows PC to this Linux machine, move the old
+computer's folders into this computer's backup instead. Use **Move to This Computer…** on that
+computer's row, or:
+
+```bash
+pdfs devices list                 # find the old computer's UID
+pdfs devices migrate UID
+```
+
+Each folder moves on Proton Drive itself, so nothing is uploaded again and no storage is used
+twice. A folder whose name this computer already uses gets the old computer's name added, for
+example `Documents (DESKTOP-1)`. The restore picker then opens, as in
+[Step 3](#step-3-restore-the-folders), so you choose where each folder goes here.
+
+The old computer stays in your account, without those folders. Unlike
+[adoption](#step-2-continue-the-old-computers-backup), this machine keeps its own name and backup.
+
+> [!WARNING]
+> Stop Proton Drive on the old computer first. A client still running there sees its folders
+> disappear, and may upload them again as new.
+
 ## 3. How the restore works
 
 This section is for the curious and for anyone debugging a restore.

docs/TROUBLESHOOTING.md

@@ -72,6 +72,20 @@ pdfs status
 unfamiliar network. The CLI cannot show it. Sign in with `pdfs-app`, which displays the challenge;
 the stored session then works for the CLI too.
 
+**"The verification page couldn't be opened"** — WebKit, which shows the CAPTCHA page, could not
+start its sandbox. Hardened systems such as secureblue keep its bubblewrap from the journal socket,
+and the log then shows `bwrap: Can't get type of source /run/systemd/journal/socket: Permission
+denied` and `Failed to fully launch dbus-proxy`. Check that `bwrap` and `xdg-dbus-proxy` are
+installed. If they are, sign in once with the sandbox switched off for this one run:
+
+```bash
+WEBKIT_DISABLE_SANDBOX_THIS_IS_DANGEROUS=1 pdfs-app
+```
+
+Quit the app first, so this starts a new instance. The page then runs without WebKit's isolation,
+so use this only for the sign-in. The stored session keeps working without it. Signing in from
+your usual network, without a VPN, often avoids the CAPTCHA in the first place.
+
 **Sign-in works but is forgotten after a restart** — no Secret Service provider is running, or its
 keyring is locked. Install and unlock GNOME Keyring, KWallet or KeePassXC (with Secret Service
 enabled). `pdfs diagnose` shows `keyring session` as failing in that case.

docs/USER_GUIDE.md

@@ -278,6 +278,9 @@ Proton Drive keeps earlier versions of every file. **Details → Versions…** i
   **Restore to This Computer…** downloads its folders here.
 - **Continue This Backup Here…** makes this computer take over another computer's backup, for
   example after reinstalling or replacing a machine. See [RECOVERY.md](RECOVERY.md).
+- **Move to This Computer…** moves another computer's folders into this computer's backup, for
+  example when you switch from Windows to Linux, and then offers them for syncing here. The other
+  computer stays in the list, without those folders.
 
 ## Search launcher
 

packaging/PKGBUILD

@@ -9,7 +9,7 @@
 # Build + install:   cd packaging && makepkg -fi
 
 pkgname=proton-drive-linux
-pkgver=3.1.1
+pkgver=3.1.2
 pkgrel=1
 pkgdesc="Unofficial Proton Drive client for Linux: files-on-demand FUSE mount, CLI, GTK4 app + tray"
 arch=('x86_64')