Merge remote-tracking branch 'origin/docs/bugs-issue-audit' into fix/sync-engine-containment

# Conflicts:
#	docs/BUGS.md

crates/pdfs-cli/src/journal.rs

@@ -0,0 +1,122 @@
+//! Log priorities for journald.
+//!
+//! journald files each line a service writes at the unit's default priority,
+//! info, unless the line opens with a syslog `<N>` prefix. Without one every
+//! WARN and ERROR the daemon logs is stored as info, and the
+//! `journalctl -p warning` that the troubleshooting guide asks for shows
+//! nothing (`docs/BUGS.md` B258).
+
+use std::fmt;
+use std::os::unix::fs::MetadataExt;
+
+use tracing::{Event, Level, Subscriber};
+use tracing_subscriber::fmt::format::Writer;
+use tracing_subscriber::fmt::{FmtContext, FormatEvent, FormatFields};
+use tracing_subscriber::registry::LookupSpan;
+
+/// Whether standard output is the journal stream systemd connected this
+/// process to.
+///
+/// `JOURNAL_STREAM` alone does not say so: a terminal started from a user unit
+/// inherits it, and every `pdfs` run in that terminal would print the
+/// prefixes. systemd sets it to the stream's `device:inode`, so it is compared
+/// against what fd 1 actually is.
+pub(crate) fn stdout_is_journal() -> bool {
+    let Some(stream) = std::env::var_os("JOURNAL_STREAM") else {
+        return false;
+    };
+    let Ok(stdout) = std::fs::metadata("/proc/self/fd/1") else {
+        return false;
+    };
+    stream
+        .to_str()
+        .is_some_and(|value| names_stream(value, stdout.dev(), stdout.ino()))
+}
+
+/// Whether a `JOURNAL_STREAM` value names the file `dev`:`ino`.
+fn names_stream(value: &str, dev: u64, ino: u64) -> bool {
+    value
+        .split_once(':')
+        .is_some_and(|(d, i)| d.parse() == Ok(dev) && i.parse() == Ok(ino))
+}
+
+/// The syslog priority journald should file a `level` line at.
+fn priority(level: &Level) -> u8 {
+    match *level {
+        Level::ERROR => 3,
+        Level::WARN => 4,
+        Level::INFO => 6,
+        Level::DEBUG | Level::TRACE => 7,
+    }
+}
+
+/// An event format that opens each line with its `<N>` priority, then writes
+/// the line as `F` would.
+pub(crate) struct Prioritized<F>(pub(crate) F);
+
+impl<S, N, F> FormatEvent<S, N> for Prioritized<F>
+where
+    S: Subscriber + for<'a> LookupSpan<'a>,
+    N: for<'a> FormatFields<'a> + 'static,
+    F: FormatEvent<S, N>,
+{
+    fn format_event(
+        &self,
+        ctx: &FmtContext<'_, S, N>,
+        mut writer: Writer<'_>,
+        event: &Event<'_>,
+    ) -> fmt::Result {
+        write!(writer, "<{}>", priority(event.metadata().level()))?;
+        self.0.format_event(ctx, writer, event)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::io;
+    use std::sync::{Arc, Mutex};
+
+    #[derive(Clone)]
+    struct Buf(Arc<Mutex<Vec<u8>>>);
+
+    impl io::Write for Buf {
+        fn write(&mut self, bytes: &[u8]) -> io::Result<usize> {
+            self.0.lock().unwrap().extend_from_slice(bytes);
+            Ok(bytes.len())
+        }
+        fn flush(&mut self) -> io::Result<()> {
+            Ok(())
+        }
+    }
+
+    #[test]
+    fn each_line_opens_with_the_priority_of_its_level() {
+        let buf = Buf(Arc::new(Mutex::new(Vec::new())));
+        let writer = buf.clone();
+        let subscriber = tracing_subscriber::fmt()
+            .with_max_level(Level::DEBUG)
+            .with_ansi(false)
+            .with_writer(move || writer.clone())
+            .event_format(Prioritized(tracing_subscriber::fmt::format()))
+            .finish();
+        tracing::subscriber::with_default(subscriber, || {
+            tracing::error!("e");
+            tracing::warn!("w");
+            tracing::info!("i");
+            tracing::debug!("d");
+        });
+        let out = String::from_utf8(buf.0.lock().unwrap().clone()).unwrap();
+        let prefixes: Vec<&str> = out.lines().map(|line| &line[..3]).collect();
+        assert_eq!(prefixes, ["<3>", "<4>", "<6>", "<7>"]);
+    }
+
+    #[test]
+    fn journal_stream_must_name_the_same_file() {
+        assert!(names_stream("8:12345", 8, 12345));
+        assert!(!names_stream("8:12345", 8, 54321));
+        assert!(!names_stream("9:12345", 8, 12345));
+        assert!(!names_stream("8", 8, 12345));
+        assert!(!names_stream("", 8, 12345));
+    }
+}

crates/pdfs-cli/src/main.rs

@@ -20,6 +20,8 @@ use pdfs_core::control::{
 use pdfs_core::db::Db;
 use pdfs_core::service;
 
+mod journal;
+
 /// `println!` for this binary, shadowing std's, which panics when stdout is
 /// closed: `pdfs ls | head` ended in a "Broken pipe" panic once `head` had its
 /// lines. This one hands the failure to [`stdout_written`] instead.
@@ -879,15 +881,22 @@ fn cli_error(kind: ErrorKind, message: &str) -> String {
 }
 
 fn main() -> Result<()> {
-    tracing_subscriber::fmt()
+    let filter = tracing_subscriber::EnvFilter::try_from_default_env()
-        .with_env_filter(
-            tracing_subscriber::EnvFilter::try_from_default_env()
         // `pgp` logs a benign WARN when it re-serializes a Proton secret-key
         // packet with a longer (but equivalent) length encoding than the
         // original; drop it to error so normal runs stay quiet.
-                .unwrap_or_else(|_| "info,pgp=error".into()),
+        .unwrap_or_else(|_| "info,pgp=error".into());
-        )
+    if journal::stdout_is_journal() {
+        // journalctl colours lines by the priority the prefix gives them, so
+        // the escape codes would only be noise in the stored text.
+        tracing_subscriber::fmt()
+            .with_env_filter(filter)
+            .with_ansi(false)
+            .event_format(journal::Prioritized(tracing_subscriber::fmt::format()))
             .init();
+    } else {
+        tracing_subscriber::fmt().with_env_filter(filter).init();
+    }
 
     let cli = Cli::parse();
     JSON_OUTPUT.store(cli.json, std::sync::atomic::Ordering::Relaxed);
@@ -1556,9 +1565,13 @@ fn cmd_versions(action: VersionCmd) -> Result<()> {
 }
 
 fn cmd_members(path: PathBuf) -> Result<()> {
-    match control_request(CtlRequest::ListShare {
+    let response = control_request(CtlRequest::ListShare {
         path: path_arg(&path)?,
-    })? {
+    })?;
+    if emit_json(&response)? {
+        return Ok(());
+    }
+    match response {
         CtlResponse::Share { entries, link } => {
             if entries.is_empty() {
                 println!("No members or pending invitations.");
@@ -1625,6 +1638,7 @@ fn cmd_public_link(action: PublicLinkCmd) -> Result<()> {
             password,
             expires,
         })? {
+            response if emit_json(&response)? => {}
             CtlResponse::PublicLink { link } => {
                 println!("{}", link.url.as_deref().unwrap_or("(no url returned)"));
             }
@@ -1646,6 +1660,7 @@ fn cmd_public_link(action: PublicLinkCmd) -> Result<()> {
             password: link_change(password, no_password),
             expires: link_change(expires, no_expiry),
         })? {
+            response if emit_json(&response)? => {}
             CtlResponse::PublicLink { link } => {
                 println!("{}", link.url.as_deref().unwrap_or("(no url returned)"));
             }
@@ -3048,9 +3063,13 @@ fn cmd_copy(sources: Vec<PathBuf>, new_parent: PathBuf) -> Result<()> {
 }
 
 fn cmd_du(path: PathBuf) -> Result<()> {
-    match control_request(CtlRequest::FolderSize {
+    let response = control_request(CtlRequest::FolderSize {
         path: path_arg(&path)?,
-    })? {
+    })?;
+    if emit_json(&response)? {
+        return Ok(());
+    }
+    match response {
         CtlResponse::FolderSize { size, items } => {
             let noun = if items == 1 { "item" } else { "items" };
             println!(
@@ -3086,6 +3105,24 @@ fn human_secs(secs: u64) -> String {
     }
 }
 
+/// The sync engine's line in `pdfs diagnostics`: whether it runs, and which
+/// folder's pass it is on.
+fn sync_engine_line(sync: &pdfs_core::control::SyncEngineState) -> String {
+    let mut line = match (sync.running, sync.pass_folder) {
+        (false, _) => "STOPPED; synced folders do not sync until the daemon restarts".to_string(),
+        (true, None) => "idle".to_string(),
+        (true, Some(folder)) => format!(
+            "pass on folder {folder} for {}, last progress {} ago",
+            human_secs(sync.pass_age_secs),
+            human_secs(sync.pass_idle_secs),
+        ),
+    };
+    if sync.panics > 0 {
+        line.push_str(&format!("; {} pass(es) panicked", sync.panics));
+    }
+    line
+}
+
 fn cmd_diagnostics() -> Result<()> {
     let response = control_request(CtlRequest::Diagnostics)?;
     if emit_json(&response)? {
@@ -3121,6 +3158,9 @@ fn cmd_diagnostics() -> Result<()> {
                     human_secs(worker.age_secs)
                 );
             }
+            if let Some(sync) = &d.sync {
+                println!("sync engine: {}", sync_engine_line(sync));
+            }
             if d.inflight.is_empty() {
                 println!("in-flight requests: none");
             } else {

crates/pdfs-core/src/control.rs

@@ -1980,6 +1980,29 @@ pub struct Diagnostics {
     pub control_handler_limit: usize,
     /// Queued mutations not yet drained.
     pub pending_ops: u64,
+    /// The folder-sync engine. `None` from a daemon that predates the field.
+    #[serde(default)]
+    pub sync: Option<SyncEngineState>,
+}
+
+/// What the folder-sync engine is doing, for [`Diagnostics`].
+///
+/// The engine is one thread that runs every synced folder's passes in turn.
+/// Dead or stuck, it looked exactly like an idle one: workers idle, nothing
+/// queued, nothing in the journal (`docs/BUGS.md` B259).
+#[derive(Serialize, Deserialize, Debug, Clone, Default)]
+pub struct SyncEngineState {
+    /// Whether the engine thread is running. Once it has ended, nothing syncs
+    /// until the daemon restarts.
+    pub running: bool,
+    /// The synced folder whose pass is running, if one is.
+    pub pass_folder: Option<i64>,
+    /// How long that pass has been running.
+    pub pass_age_secs: u64,
+    /// How long since that pass last reported progress.
+    pub pass_idle_secs: u64,
+    /// Passes that ended in a panic since the daemon started.
+    pub panics: u64,
 }
 
 /// The daemon's reply to a [`Request`].

crates/pdfs-fuse/src/devices.rs

@@ -989,9 +989,15 @@ impl Core {
                     .db
                     .sync_entries(id)
                     .map_err(|e| SwitchBlocked::Failed(format!("db: {e:?}")))?;
-                if let Some(reason) =
+                let rules = self.ignore_rules(&local);
-                    sync::mirror_tree_unsynced(&local, &baseline, &self.ignore_rules(&local))
+                // Emptied before any pass saw it, the folder is still `idle`, and
-                {
+                // the check below would refuse the switch for good. The push pass
+                // of a queued switch forgets those paths instead (`docs/BUGS.md`
+                // B255).
+                if sync::mirror_tree_gone(&local, &baseline, &rules) {
+                    return Err(SwitchBlocked::NotNow);
+                }
+                if let Some(reason) = sync::mirror_tree_unsynced(&local, &baseline, &rules) {
                     return Err(SwitchBlocked::Failed(format!(
                         "going online-only would delete what is only on this computer: {reason}"
                     )));

crates/pdfs-fuse/src/diagnostics.rs

@@ -163,6 +163,7 @@ impl Core {
             control_handlers: super::control::active_handlers(),
             control_handler_limit: super::control::handler_limit(),
             pending_ops: self.pending_ops_quickly(),
+            sync: Some(self.sync_engine.report()),
         }
     }
 

crates/pdfs-fuse/src/lib.rs

@@ -728,6 +728,8 @@ struct Core {
     /// can say what a pass is doing rather than just "syncing". An entry exists
     /// only while that folder's reconcile pass is running.
     sync_progress: Arc<Mutex<HashMap<i64, SyncProgress>>>,
+    /// Whether the folder-sync engine is alive, and which pass it is on.
+    sync_engine: Arc<sync::EngineHealth>,
     /// Channel to the folder-sync engine: nudges it to
     /// reconcile a folder, reconcile everything, or re-scan its watch set.
     sync_tx: std::sync::mpsc::Sender<sync::SyncMsg>,
@@ -5989,6 +5991,7 @@ impl Core {
         if let Some(p) = self.sync_progress.lock().get_mut(&folder_id) {
             f(p);
         }
+        self.sync_engine.moved();
     }
 
     /// Set the number of items the scan expects to check, from the size of the
@@ -7312,13 +7315,15 @@ mod size_upgrade_tests {
     fn a_listing_waits_for_the_whole_size_batch_but_not_forever() {
         let slot = Arc::new(SizeUpgrade::default());
         let worker = slot.clone();
+        // Read before the spawn: the worker's sleeps can start before this
+        // thread runs again, which made the bound below fail on a busy runner.
+        let started = Instant::now();
         let t = std::thread::spawn(move || {
             std::thread::sleep(Duration::from_millis(30));
             worker.chunk_done();
             std::thread::sleep(Duration::from_millis(60));
             worker.finish();
         });
-        let started = Instant::now();
         slot.wait_finished(started + Duration::from_secs(5));
         // Past the first chunk, up to the end of the batch.
         assert!(started.elapsed() >= Duration::from_millis(90));

crates/pdfs-fuse/src/mount.rs

@@ -507,6 +507,7 @@ pub(crate) fn mount_with(
         events: Arc::new(Default::default()),
         indexing: Arc::new(AtomicBool::new(false)),
         sync_progress: Arc::new(Mutex::new(HashMap::new())),
+        sync_engine: Arc::default(),
         sync_tx,
         mounts: Arc::new(Mutex::new(SecondaryMountRegistry::default())),
         sync_locks: Arc::new(Mutex::new(HashMap::new())),

crates/pdfs-fuse/src/sim/daemon.rs

@@ -130,6 +130,15 @@ impl Daemon {
         }
     }
 
+    /// Whether the mount believes Proton is reachable, as `pdfs status` shows
+    /// it.
+    pub(crate) fn online(&self) -> io::Result<bool> {
+        match self.request(&Request::Status)? {
+            Response::Status { online, .. } => Ok(online),
+            other => Err(io::Error::other(format!("unexpected answer {other:?}"))),
+        }
+    }
+
     /// Send one control request, as the `pdfs` CLI does, and fail on a
     /// refusal.
     pub(crate) fn request(&self, request: &Request) -> io::Result<Response> {
@@ -648,7 +657,19 @@ mod tests {
                 .pending()
                 .is_ok_and(|items| items.iter().any(|item| item.attempts > 0))
         }));
+        // The drain records the failure just before it takes the mount
+        // offline. Left online, only the event poll would, much later.
+        assert!(wait_until(Duration::from_secs(2), || daemon
+            .online()
+            .is_ok_and(|online| !online)));
         daemon.client.set_online(true);
+        // The probe that sees the link return runs 2 s after the drop, then
+        // 6 s, and a loaded run can reach this line after the first one. So
+        // the 3 s below count from the mount being back, not from the link:
+        // an op left on its backoff waits 4 s or more after its failure.
+        assert!(wait_until(Duration::from_secs(30), || daemon
+            .online()
+            .unwrap_or(false)));
         assert!(
             wait_until(Duration::from_secs(3), || {
                 daemon.pending().is_ok_and(|items| items.is_empty())
@@ -2981,4 +3002,69 @@ mod tests {
         assert!(matches!(daemon.stop(), Ok(MountOutcome::Shutdown)));
         let _ = std::fs::remove_dir_all(&dir);
     }
+
+    /// Emptied before any pass saw it, the folder is still `idle`, and the
+    /// switch was refused for good: every path read as "deleted here but not on
+    /// Proton Drive yet" (B255, found by the account run).
+    #[test]
+    #[ignore = "mounts FUSE: run with `cargo test -p pdfs-fuse sim:: -- --ignored`"]
+    fn a_folder_emptied_before_any_pass_still_goes_on_demand() {
+        let drive = FakeDrive::new();
+        let dir = scratch("ondemand-emptied-idle");
+        let daemon = Daemon::start(&dir, drive.client(1, Faults::lan())).unwrap();
+        let local = dir.join("docs");
+        let id = sync_folder(&daemon, &local, "mirror");
+        std::fs::create_dir(local.join("sub")).unwrap();
+        std::fs::write(local.join("sub/a.txt"), b"alpha").unwrap();
+        std::fs::write(local.join("sub/b.txt"), b"beta").unwrap();
+        daemon.request(&Request::SyncNow { id: Some(id) }).unwrap();
+        let on_drive = |name: &str, content: &[u8]| {
+            drive.tree().iter().any(|(path, entry)| {
+                path.ends_with(name) && *entry == Entry::File(Arc::new(content.to_vec()))
+            })
+        };
+        assert!(
+            wait_until(Duration::from_secs(30), || on_drive("sub/a.txt", b"alpha")
+                && on_drive("sub/b.txt", b"beta")
+                && listed_folder(&daemon, id).is_some_and(|f| f.state == "idle")),
+            "the folder synced: {:?}",
+            listed_folder(&daemon, id)
+        );
+
+        // In one rename, so no pass sees half of it, and asked at once, well
+        // inside the watcher's debounce, so no pass sees it empty either.
+        std::fs::rename(local.join("sub"), dir.join("moved-away")).unwrap();
+        let asked = daemon.request(&Request::SetSyncFolderMode {
+            id,
+            mode: "ondemand".into(),
+        });
+        assert!(
+            matches!(asked, Ok(Response::Ok { .. })),
+            "the switch was refused: {asked:?}"
+        );
+        assert!(
+            listed_folder(&daemon, id)
+                .is_some_and(|f| f.pending_mode.as_deref() == Some("ondemand")),
+            "the switch waits for a pass: {:?}",
+            listed_folder(&daemon, id)
+        );
+
+        assert!(
+            wait_until(Duration::from_secs(30), || listed_folder(&daemon, id)
+                .is_some_and(|f| f.mode == "ondemand" && f.pending_mode.is_none())
+                && is_mounted(&local)),
+            "the queued switch landed: {:?}",
+            listed_folder(&daemon, id)
+        );
+        assert_eq!(std::fs::read(local.join("sub/a.txt")).unwrap(), b"alpha");
+        assert_eq!(std::fs::read(local.join("sub/b.txt")).unwrap(), b"beta");
+        assert!(
+            on_drive("sub/a.txt", b"alpha") && on_drive("sub/b.txt", b"beta"),
+            "nothing was trashed on Drive: {:?}",
+            drive.tree().keys().collect::<Vec<_>>()
+        );
+
+        assert!(matches!(daemon.stop(), Ok(MountOutcome::Shutdown)));
+        let _ = std::fs::remove_dir_all(&dir);
+    }
 }

crates/pdfs-fuse/src/supervisor.rs

@@ -36,6 +36,11 @@ const TICK: Duration = Duration::from_secs(15);
 /// would train everyone to ignore the real one.
 const STALL_AFTER: Duration = Duration::from_secs(120);
 
+/// How long a sync pass may go without reporting progress before it is called
+/// out. Much longer than [`STALL_AFTER`]: one large file in a pass reports
+/// nothing until its whole transfer is done.
+const SYNC_STALL_AFTER: Duration = Duration::from_secs(900);
+
 /// How often resident size goes into the log.
 const RSS_EVERY: Duration = Duration::from_secs(300);
 
@@ -137,6 +142,26 @@ fn report_stalls(report: &pdfs_core::control::Diagnostics, last_completed: (u64,
             "the transfer lane has not completed a job since the last check"
         );
     }
+    // The engine is one thread for every synced folder, so a dead or stuck one
+    // stops all of them while the worker pool looks idle (B259).
+    if let Some(sync) = &report.sync {
+        if !sync.running {
+            stalled = true;
+            warn!(
+                "the sync engine is not running; synced folders do not sync until the daemon restarts"
+            );
+        } else if let Some(folder) = sync.pass_folder
+            && sync.pass_idle_secs >= SYNC_STALL_AFTER.as_secs()
+        {
+            stalled = true;
+            warn!(
+                folder,
+                age_secs = sync.pass_age_secs,
+                idle_secs = sync.pass_idle_secs,
+                "a sync pass has not reported progress for a long time"
+            );
+        }
+    }
     stalled
 }
 
@@ -169,7 +194,7 @@ fn probe(control_socket: &Path) -> bool {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use pdfs_core::control::{Diagnostics, InflightRequest, WorkerState};
+    use pdfs_core::control::{Diagnostics, InflightRequest, SyncEngineState, WorkerState};
 
     fn busy_worker(age_secs: u64) -> WorkerState {
         WorkerState {
@@ -226,4 +251,45 @@ mod tests {
         assert!(!report_stalls(&report, (0, 30)));
         assert!(report_stalls(&report, (0, 40)));
     }
+
+    fn with_sync(sync: SyncEngineState) -> Diagnostics {
+        Diagnostics {
+            sync: Some(sync),
+            ..Default::default()
+        }
+    }
+
+    /// A sync engine that has ended stops every synced folder while the
+    /// workers look idle, which is what issue #53 looked like (B259).
+    #[test]
+    fn a_stopped_sync_engine_is_a_stall() {
+        assert!(report_stalls(
+            &with_sync(SyncEngineState::default()),
+            (0, 0)
+        ));
+    }
+
+    /// A pass that keeps reporting progress is working, however long it runs;
+    /// one that has gone quiet past the threshold is not.
+    #[test]
+    fn only_a_quiet_sync_pass_is_a_stall() {
+        let busy = SyncEngineState {
+            running: true,
+            pass_folder: Some(3),
+            pass_age_secs: SYNC_STALL_AFTER.as_secs() * 4,
+            pass_idle_secs: 5,
+            panics: 0,
+        };
+        assert!(!report_stalls(&with_sync(busy.clone()), (0, 0)));
+        let quiet = SyncEngineState {
+            pass_idle_secs: SYNC_STALL_AFTER.as_secs(),
+            ..busy
+        };
+        assert!(report_stalls(&with_sync(quiet), (0, 0)));
+        let idle = SyncEngineState {
+            running: true,
+            ..Default::default()
+        };
+        assert!(!report_stalls(&with_sync(idle), (0, 0)));
+    }
 }

crates/pdfs-fuse/src/sync.rs

@@ -48,8 +48,10 @@ mod engine;
 mod local_scan;
 mod model;
 mod planner;
+#[cfg(test)]
+use engine::Running;
 pub(crate) use engine::SYNC_CONCURRENCY;
-pub(crate) use engine::{SyncMsg, spawn};
+pub(crate) use engine::{EngineHealth, SyncMsg, spawn};
 #[cfg(test)]
 use engine::{classify, event_target, settle_with};
 #[cfg(test)]
@@ -67,6 +69,11 @@ use planner::{
     plan_file, rel_to_path, remote_sig, remote_subtree_changed, revision_moved, tracked_baseline,
     unchanged_remote_size,
 };
+
+/// A pass that took at least this long is logged at info even when it changed
+/// nothing, so the journal says where a slow engine spends its time.
+const SLOW_PASS: Duration = Duration::from_secs(30);
+
 /// What a [`Pending`] op did, so the reconcile can update shared state on the
 /// engine thread (never inside a task).
 enum Applied {
@@ -154,6 +161,14 @@ impl Core {
         // The cost is one small file read against a pass that is about to walk the
         // whole tree.
         let rules = self.ignore_rules(&local_root);
+        // A first pass is the one a user waits on after adding or restoring a
+        // folder, so it is said at info; the poll's passes stay at debug.
+        if folder.last_sync == 0 {
+            info!(id = folder.id, path = %folder.local_path, "sync: first pass starting");
+        } else {
+            debug!(id = folder.id, "sync: pass starting");
+        }
+        let started = Instant::now();
         self.progress_begin(folder.id);
         let result = if push_only {
             self.push_pass(folder.id, &local_root, &remote_root, &rules)
@@ -195,6 +210,18 @@ impl Core {
                     "idle"
                 };
                 let _ = self.db.sync_folder_set_state(folder.id, state, now_secs());
+                let elapsed = started.elapsed();
+                if folder.last_sync == 0 || !outcome.is_empty() || elapsed >= SLOW_PASS {
+                    info!(
+                        id = folder.id,
+                        state,
+                        elapsed_ms = elapsed.as_millis() as u64,
+                        summary = %outcome.summary(),
+                        "sync: pass finished"
+                    );
+                } else {
+                    debug!(id = folder.id, state, "sync: pass finished");
+                }
                 self.report_unscanned(folder.id, name, &outcome.unscanned);
                 // Summarise a pass that actually moved something. A poll over an
                 // unchanged folder does nothing and says nothing — otherwise the
@@ -2253,6 +2280,27 @@ pub(crate) fn mirror_tree_unsynced(
         .map(|r| format!("{r} was deleted here but not on Proton Drive yet"))
 }
 
+/// Whether a mirror folder's local copy is gone in full: the folder is still
+/// there, but not one tracked path of its baseline is.
+///
+/// [`mirror_tree_unsynced`] reads that as deletions not carried up yet, which
+/// would refuse the switch to on-demand for good. It is the wipe guard's case
+/// instead, which the push pass a queued switch runs settles without trashing
+/// anything on Drive (#46), so the switch waits for that pass.
+pub(crate) fn mirror_tree_gone(
+    root: &Path,
+    baseline: &HashMap<String, StoredSyncEntry>,
+    rules: &IgnoreRules,
+) -> bool {
+    let tracked = filter_baseline(baseline, rules);
+    root.is_dir()
+        && !tracked.is_empty()
+        && tracked.keys().all(|rel| {
+            std::fs::symlink_metadata(root.join(rel_to_path(rel)))
+                .is_err_and(|e| e.kind() == std::io::ErrorKind::NotFound)
+        })
+}
+
 /// The walk behind both checks. `rules`, when given, only names an ignored
 /// path as such in the reason; it is still something only this disk has.
 fn unsynced_local(
@@ -2417,6 +2465,50 @@ fn system_mtime_ns(meta: &std::fs::Metadata) -> Option<i64> {
 mod tests {
     use super::*;
 
+    /// A panic in a pass ends that pass and is counted; the engine is not
+    /// left believing the pass still runs (`docs/BUGS.md` B259).
+    #[test]
+    fn a_panicking_pass_is_contained_and_counted() {
+        let health = EngineHealth::default();
+        assert!(!health.contain(7, || panic!("a pass that panics")));
+        let report = health.report();
+        assert_eq!(report.panics, 1);
+        assert_eq!(report.pass_folder, None);
+        assert!(health.contain(7, || {}));
+        assert_eq!(health.report().panics, 1);
+    }
+
+    /// While a pass runs, the report names its folder, which is what tells a
+    /// long pass apart from an idle engine.
+    #[test]
+    fn the_running_pass_is_reported() {
+        let health = EngineHealth::default();
+        let mut seen = None;
+        health.contain(7, || seen = health.report().pass_folder);
+        assert_eq!(seen, Some(7));
+    }
+
+    /// The engine reads as running only while its thread lives, including
+    /// when the thread ends in a panic.
+    #[test]
+    fn the_engine_reads_as_stopped_once_its_thread_ends() {
+        let health = Arc::new(EngineHealth::default());
+        let thread_health = health.clone();
+        let (started_tx, started_rx) = std::sync::mpsc::channel();
+        let (end_tx, end_rx) = std::sync::mpsc::channel::<()>();
+        let thread = std::thread::spawn(move || {
+            let _running = Running::start(&thread_health);
+            started_tx.send(()).unwrap();
+            let _ = end_rx.recv();
+            panic!("the engine thread panics");
+        });
+        started_rx.recv().unwrap();
+        assert!(health.report().running);
+        end_tx.send(()).unwrap();
+        assert!(thread.join().is_err());
+        assert!(!health.report().running);
+    }
+
     /// A removal of something already gone has produced the state the sync
     /// engine wanted, so its baseline is dropped rather than retried forever.
     /// Anything else stays an error and keeps the baseline (`docs/BUGS.md` B42).
@@ -3538,6 +3630,26 @@ mod tests {
         assert!(reason.unwrap().contains("link"));
     }
 
+    /// Emptied before any pass saw it, the folder waits for the push pass that
+    /// forgets those paths, instead of being refused for good (B255).
+    #[test]
+    fn only_a_local_copy_gone_in_full_counts_as_gone() {
+        let (root, baseline) = synced_subtree("evict-gone");
+        let rules = rules_for(&[]);
+        let whole = mirror_tree_gone(&root, &baseline, &rules);
+        std::fs::remove_dir_all(root.join("dir/sub")).unwrap();
+        let partly = mirror_tree_gone(&root, &baseline, &rules);
+        std::fs::remove_dir_all(root.join("dir")).unwrap();
+        let emptied = mirror_tree_gone(&root, &baseline, &rules);
+        let none_synced = mirror_tree_gone(&root, &HashMap::new(), &rules);
+        std::fs::remove_dir_all(&root).unwrap();
+        let no_root = mirror_tree_gone(&root, &baseline, &rules);
+        assert!(!whole && !partly, "a deletion with survivors is a real one");
+        assert!(emptied);
+        assert!(!none_synced, "an empty baseline has nothing to lose");
+        assert!(!no_root, "a missing folder is the pass's error to report");
+    }
+
     /// The same rule one level up: if the sync root itself cannot be read, the
     /// pass sees nothing, and "nothing" must never mean "delete everything".
     #[test]

crates/pdfs-fuse/src/sync/engine.rs

@@ -1,5 +1,11 @@
 //! Filesystem watcher, polling, and debounce control plane.
 
+use std::panic::AssertUnwindSafe;
+use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
+
+use pdfs_core::control::SyncEngineState;
+use tracing::error;
+
 use super::*;
 
 /// How long the watcher must go quiet before a burst counts as finished.
@@ -53,8 +59,124 @@ pub(crate) fn spawn(core: Core, rx: Receiver<SyncMsg>) -> Option<std::thread::Jo
     }
 }
 
+/// Whether the engine is alive and which pass it is on, for
+/// [`Core::diagnostics`] and the supervisor.
+///
+/// A panic in a pass used to end the engine thread. Every later add, sync-now,
+/// file event and poll then went into a channel nobody read, the folder stayed
+/// `syncing`, and nothing said so until a restart (`docs/BUGS.md` B259).
+#[derive(Default)]
+pub(crate) struct EngineHealth {
+    running: AtomicBool,
+    pass: Mutex<Option<PassClock>>,
+    panics: AtomicU64,
+}
+
+#[derive(Clone, Copy)]
+struct PassClock {
+    folder: i64,
+    started: Instant,
+    moved: Instant,
+}
+
+impl EngineHealth {
+    /// Note that the running pass reported progress.
+    pub(crate) fn moved(&self) {
+        if let Some(pass) = self.pass.lock().as_mut() {
+            pass.moved = Instant::now();
+        }
+    }
+
+    /// The engine's state now. `try_lock`, like the rest of the diagnostics:
+    /// a report must not wait on the thing it reports about.
+    pub(crate) fn report(&self) -> SyncEngineState {
+        let pass = self.pass.try_lock().and_then(|pass| *pass);
+        SyncEngineState {
+            running: self.running.load(Ordering::Relaxed),
+            pass_folder: pass.map(|p| p.folder),
+            pass_age_secs: pass.map_or(0, |p| p.started.elapsed().as_secs()),
+            pass_idle_secs: pass.map_or(0, |p| p.moved.elapsed().as_secs()),
+            panics: self.panics.load(Ordering::Relaxed),
+        }
+    }
+
+    /// Run `pass` over `folder` as the current pass. Returns `false` when it
+    /// panicked: the panic ends that pass, not the engine.
+    pub(super) fn contain(&self, folder: i64, pass: impl FnOnce()) -> bool {
+        let now = Instant::now();
+        *self.pass.lock() = Some(PassClock {
+            folder,
+            started: now,
+            moved: now,
+        });
+        let finished = std::panic::catch_unwind(AssertUnwindSafe(pass)).is_ok();
+        *self.pass.lock() = None;
+        if !finished {
+            self.panics.fetch_add(1, Ordering::Relaxed);
+        }
+        finished
+    }
+}
+
+/// Marks the engine running for as long as it lives.
+pub(super) struct Running<'a>(&'a EngineHealth);
+
+impl<'a> Running<'a> {
+    pub(super) fn start(health: &'a EngineHealth) -> Self {
+        health.running.store(true, Ordering::Relaxed);
+        Self(health)
+    }
+}
+
+impl Drop for Running<'_> {
+    fn drop(&mut self) {
+        self.0.running.store(false, Ordering::Relaxed);
+        if std::thread::panicking() {
+            error!("sync engine stopped by a panic; nothing syncs until the daemon restarts");
+        }
+    }
+}
+
+/// One folder's pass, contained: a panic in it sets the folder to `error` and
+/// leaves the engine running for the next one.
+fn run_pass(core: &Core, folder: &StoredSyncFolder) {
+    if core
+        .sync_engine
+        .contain(folder.id, || core.reconcile_folder(folder))
+    {
+        return;
+    }
+    core.progress_end(folder.id);
+    let _ = core
+        .db
+        .sync_folder_set_state(folder.id, "error", folder.last_sync);
+    error!(
+        id = folder.id,
+        path = %folder.local_path,
+        "sync: pass panicked; the folder is set to error and tried again on the next poll"
+    );
+    core.log_activity(
+        ActivityKind::Sync,
+        format!("sync failed for {}", base_name(&folder.local_path)),
+        "an internal error stopped the pass; it is tried again on the next poll",
+        false,
+    );
+}
+
+/// The pass a `Reconcile(id)` asked for. A folder removed since, or one the
+/// database cannot read, is said so rather than dropped in silence.
+fn run_pass_by_id(core: &Core, id: i64) {
+    match core.db.sync_folder_get(id) {
+        Ok(Some(folder)) => run_pass(core, &folder),
+        Ok(None) => debug!(id, "sync: folder removed before its pass; skipping"),
+        Err(e) => warn!(id, error = ?e, "sync: cannot read folder; skipping its pass"),
+    }
+}
+
 /// The engine control loop. Single-threaded so reconcile passes never overlap.
 fn engine_loop(core: Core, rx: Receiver<SyncMsg>) {
+    let health = core.sync_engine.clone();
+    let _running = Running::start(&health);
     // Paths the watcher currently covers, mapped to their folder id, so an event
     // path can be resolved back to the folder it belongs to.
     let watched: Arc<Mutex<Vec<(PathBuf, i64)>>> = Arc::new(Mutex::new(Vec::new()));
@@ -120,9 +242,7 @@ fn engine_loop(core: Core, rx: Receiver<SyncMsg>) {
                 if core.sync_paused() {
                     break;
                 }
-                if let Ok(Some(folder)) = core.db.sync_folder_get(id) {
+                run_pass_by_id(&core, id);
-                    core.reconcile_folder(&folder);
-                }
             }
         }
     }
@@ -159,9 +279,7 @@ fn poll_only_loop(core: &Core, rx: Receiver<SyncMsg>) {
                 if core.sync_paused() {
                     break;
                 }
-                if let Ok(Some(folder)) = core.db.sync_folder_get(id) {
+                run_pass_by_id(core, id);
-                    core.reconcile_folder(&folder);
-                }
             }
         }
     }
@@ -254,7 +372,7 @@ fn reconcile_all(core: &Core) {
         }
     };
     for folder in folders {
-        core.reconcile_folder(&folder);
+        run_pass(core, &folder);
     }
 }
 

docs/BUGS.md

@@ -68,6 +68,20 @@ original wording.
 
 | Entry | Title | What is left |
 |---|---|---|
+| [B273](#b273--a-restore-proposes-another-computers-paths-when-the-two-share-a-hostname) | A restore proposes another computer's paths when the two share a hostname | Not fixed |
+| [B272](#b272--after-a-folder-is-removed-and-added-again-its-file-events-go-to-the-old-id) | After a folder is removed and added again, its file events go to the old id | Not fixed |
+| [B271](#b271--one-failed-listing-makes-a-large-first-sync-start-over-from-nothing) | One failed listing makes a large first sync start over from nothing | Not fixed |
+| [B270](#b270--one-file-left-in-a-mirror-folder-clears-the-wipe-guard-for-all-the-others) | One file left in a mirror folder clears the wipe guard for all the others | Not fixed |
+| [B269](#b269--a-restore-that-skipped-every-folder-reports-success) | A restore that skipped every folder reports success | Not fixed |
+| [B268](#b268--pdfs-diagnose-says-no-problems-found-while-sync-is-stuck) | `pdfs diagnose` says "No problems found" while sync is stuck | Not fixed |
+| [B267](#b267--a-key-failure-at-a-start-from-a-warm-cache-shows-as-offline-for-good) | A key failure at a start from a warm cache shows as offline for good | Not fixed |
+| [B266](#b266--pin-unpin-search-and-node-loads-report-a-database-error-as-offline) | Pin, unpin, search and node loads report a database error as "offline" | Not fixed |
+| [B265](#b265--address-keys-whose-token-is-for-an-inactive-account-key-never-open) | Address keys whose token is for an inactive account key never open | Needs an SDK change; not reproduced |
+| [B264](#b264--a-mount-that-fails-after-starting-its-workers-leaves-them-running) | A mount that fails after starting its workers leaves them running | Not fixed |
+| [B263](#b263--a-mount-that-can-never-succeed-retries-every-5-s-and-tells-only-the-journal) | A mount that can never succeed retries every 5 s and tells only the journal | Not fixed |
+| [B262](#b262--watching-a-large-synced-folder-holds-up-the-sync-engine-and-a-failed-watch-is-never-retried) | Watching a large synced folder holds up the sync engine, and a failed watch is never retried | Not fixed |
+| [B261](#b261--a-folder-that-has-never-synced-reads-up-to-date) | A folder that has never synced reads "up to date" | Not fixed |
+| [B260](#b260--the-poll-pushes-a-new-folders-first-sync-behind-every-other-folder) | The poll pushes a new folder's first sync behind every other folder | Not fixed |
 | [B134](#b134--a-file-deleted-online-while-the-drain-checks-its-write-is-kept-as-a-conflict-copy) | A file deleted online while the drain checks its write is kept as a conflict copy | Only with `local_first` off |
 | [B91](#b91--the-daemon-hung-overnight-and-nothing-could-say-what-it-was-waiting-on) | The daemon hung overnight, and nothing could say what it was waiting on | The cause is not diagnosed; the daemon now reports where it is stuck and is restarted |
 | [B67](#b67--fresh-state-restore-can-silently-select-a-new-device-high-22) | Fresh-state restore can silently select a new device (HIGH-22) | An ambiguous device after a loss of local state is not asked about |
@@ -80,6 +94,7 @@ original wording.
 
 | Entry | Title | What is left |
 |---|---|---|
+| [B259](#b259--the-sync-engine-can-die-or-hang-and-nothing-shows-it-until-a-restart) | The sync engine can die or hang, and nothing shows it until a restart | No pass deadline; an ended engine is reported, not restarted; the trigger in #53 is not known |
 | [B199](#b199--a-stopped-share-stays-on-the-shared-by-me-page-for-minutes) | A stopped share stays on the Shared by me page for minutes | The share itself is not deleted; the SDK has no call for it |
 | [B88](#b88--pdfs-pin-rename-move-delete-and-sharing-still-cannot-name-a-path-under-a-secondary-mount) | `pdfs pin`, `rename`, `move`, `delete` and sharing still cannot name a path under a secondary mount | `pin`, `unpin`, opening a file, thumbnails, uploads, sharing and versions |
 | [B72](#b72--pdfs-trash-never-returns) | `pdfs trash` never returns | The slowness of the first refresh is unmeasured |
@@ -100,6 +115,7 @@ a live account since.
 
 | Entry | Title |
 |---|---|
+| [B258](#b258--journalctl--p-warning-shows-nothing-whatever-the-daemon-logged) | `journalctl -p warning` shows nothing, whatever the daemon logged |
 | [B256](#b256--pdfs-copy-right-after-a-save-copies-the-old-version) | `pdfs copy` right after a save copies the old version |
 | [B255](#b255--a-synced-folder-whose-files-are-all-gone-here-is-stuck-for-good) | A synced folder whose files are all gone here is stuck for good |
 | [B254](#b254--an-edit-in-the-same-second-as-a-new-upload-never-arrives) | An edit in the same second as a new upload never arrives |
@@ -359,6 +375,384 @@ a live account since.
 
 Newest first.
 
+### B273 — A restore proposes another computer's paths when the two share a hostname
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #46.
+**Where:** `saved_folder` in `crates/pdfs-core/src/profile.rs`
+
+**Repro:** Two computers with the same hostname, for example both left at a distribution's
+default `archlinux`, sync the same device. Restore a folder on one of them. The proposed local
+path and mode come from whichever of the two profiles is found first, not from this computer's.
+
+**Cause.** `saved_folder` prefers the profile whose `hostname` matches. The machine id that
+B252 added tells computers apart, but this lookup does not use it.
+
+**Fix.** Not done. Match on the machine id first, then fall back to the hostname for profiles
+written before it existed.
+
+---
+
+### B272 — After a folder is removed and added again, its file events go to the old id
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #53.
+**Where:** `rewatch` in `crates/pdfs-fuse/src/sync/engine.rs`
+
+**Repro:** Remove a synced folder and add the same path again before the engine handles the
+first `Rewatch`, so both land in one burst. Edits in the folder are not synced until the
+two-minute poll, and the same goes for every later edit until the daemon restarts.
+
+**Cause.** `rewatch` matches the watches it has against the ones it wants by path alone. The
+path is still wanted, so the old entry stays with the removed folder's id. Its events become
+`Reconcile(old id)`, `sync_folder_get` finds no row, and the request is dropped.
+
+**Fix.** Not done. Compare `(path, id)` pairs, and update the id of a path that is still
+watched.
+
+---
+
+### B271 — One failed listing makes a large first sync start over from nothing
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #46: a folder of about 19,900 items restored on a
+second computer sat at `scanning…` with nothing downloaded, and the journal showed
+`RequestTimeout (http 408)`.
+**Where:** `walk_remote` in `crates/pdfs-fuse/src/sync.rs`
+
+**Repro:** Restore or add a mirror folder with tens of thousands of items on Drive, on a link
+that drops a request now and then. The pass walks the whole remote tree before it downloads
+anything. When one folder's listing fails after the SDK's retries, the pass fails, and the
+next one walks the whole tree again. On a slow enough link it never gets past the walk.
+
+**Cause.** Each `enumerate_folder_children_node_uids`, `enumerate_nodes_light` and
+`enumerate_nodes` call in the walk ends the whole walk through `?`. Nothing is applied until
+the walk is done. Files that did download keep their baseline rows, so only the walk is lost,
+but on a first sync that is all of it. Progress is also counted only after a folder's full
+listing, so a large folder shows `scanning…` with 0 checked for a long time.
+
+**Fix.** Not done. Record a failed subtree as a gap, as undecryptable nodes already are: no
+deletions under it, and the rest of the pass still applies.
+
+---
+
+### B270 — One file left in a mirror folder clears the wipe guard for all the others
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #46, whose reporter emptied a synced folder
+several times.
+**Where:** `guard_local_wipe` and `guard_remote_wipe` in `crates/pdfs-fuse/src/sync/planner.rs`
+
+**Repro:** Sync a mirror folder with many files. Make all of them but one unavailable here: a
+half-mounted disk, a restored backup that brought back one file, or a script that emptied the
+folder and wrote one file back. The next pass trashes every other file on Drive. On a device
+that two computers sync, the other computer then deletes its copies too.
+
+**Cause.** The guard refuses a pass only when every baseline path is missing. One surviving
+path is enough to clear it, so it guards against an empty folder and nothing short of that.
+The remote guard has the same shape.
+
+**Fix.** Not done. Also refuse when most of a large baseline is missing at once, and leave the
+choice to the user: delete on the other side, or sync from scratch.
+
+---
+
+### B269 — A restore that skipped every folder reports success
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #46: the journal showed `restore complete
+restored=0 skipped=1` several times, and the user saw nothing.
+**Where:** the `RestoreSyncFolders` and `RestoreDeviceFolders` handler in
+`crates/pdfs-fuse/src/control.rs`; `restore_sync_folders` in `crates/pdfs-fuse/src/profile.rs`
+
+**Repro:** Restore a folder from another computer to a path that is already a sync root here,
+for example a folder left over from an earlier attempt. `pdfs devices join` prints `restoring
+folders`, and the app shows the same. Nothing downloads, and no error appears anywhere.
+
+**Cause.** The daemon acks before it works, because a restore outlasts the socket timeout. The
+result, `restored 0 folder(s); skipped: …`, is then logged as a successful activity, so the
+reason is only in the activity text and the journal. When the database insert fails partway,
+the `?` also skips the `Rewatch` for the folders already restored.
+
+**Fix.** Not done. Log a restore that skipped folders as a failure, name the reason in the app
+and the CLI, and offer to replace or reset the folder in the way. Send the `Rewatch` on every
+exit path.
+
+---
+
+### B268 — `pdfs diagnose` says "No problems found" while sync is stuck
+
+**Status:** Open
+**Found:** 2026-10-31, issue #53: a folder that never synced, and `diagnose` found nothing.
+**Where:** `diagnose` in `crates/pdfs-cli/src/main.rs`
+
+**Repro:** Leave a synced folder in `error`, or have queued writes that keep failing, or pause
+sync. `pdfs diagnose` reports every check `[ok]` and exits 0.
+
+**Cause.** The `Status` reply is matched with `..`, which drops `failing_ops`, `failing_error`,
+`parked_uploads`, `staged_oldest_secs` and `paused`. `diagnose` never asks for the synced
+folders or for `Diagnostics`, so a folder in error and a stalled worker are not seen. A
+control socket file with no daemon behind it is also reported `[ok]`; only the next line says
+the daemon does not answer.
+
+**Fix.** Not done. Warn on failing or parked writes, a pause, old staged data and folders in
+error, and report the sync engine's state once B259 exposes it.
+
+---
+
+### B267 — A key failure at a start from a warm cache shows as offline for good
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #40. B202 fixed the same path for a refused
+session only.
+**Where:** `fetch_or_recall_root` in `crates/pdfs-fuse/src/mount.rs`; `run_online_probe` in
+`crates/pdfs-fuse/src/link.rs`
+
+**Repro:** Sign in once so the cache holds the My Files root. Then start the daemon in a state
+where the root cannot be decrypted, for example the address-key failure of B265. The mount
+comes up "offline", the app says you are offline, and it stays so while the network is fine.
+
+**Cause.** Any error from `get_my_files_folder` other than a revoked session becomes
+`Start::Offline` when a cached root exists. The online probe then retries the same call and
+logs its failures at debug level, so the journal at the default level says nothing.
+
+**Fix.** Not done. Use `Start::Offline` only for an error `is_network_error` accepts, and
+report the others as their own state through `Status`.
+
+---
+
+### B266 — Pin, unpin, search and node loads report a database error as "offline"
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #38. B205 fixed the photo upload path only.
+**Where:** `CoreError::from_api` in `crates/pdfs-core/src/error.rs`; its callers in
+`crates/pdfs-fuse/src/lib.rs` (`pin`, `unpin`, the searches, `load node`)
+
+**Repro:** Pin a folder while the cache database is locked or full. The app says "You're
+offline" and drops the reason.
+
+**Cause.** `from_api` classifies any error that is not a `ProtonError` as `Offline`, because
+it was written for SDK calls, where that means a transport error. These callers pass it
+`pdfs_core::Error` values from the cache and the database. A `ProtonError` wrapped in
+`pdfs_core::Error::Proton` also misses the downcast, since the source chain is not walked.
+
+**Fix.** Not done. Use `CoreError::internal` at the database callers, and walk the source
+chain in `from_api` before falling back.
+
+---
+
+### B265 — Address keys whose token is for an inactive account key never open
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #40: a Duo account whose mount failed on every
+start with `fetch My Files root: cryptography error: failed to decrypt: missing key`, after three
+`failed to decrypt address key token` warnings. The web app worked. B210's fix does not apply,
+because the account has an active volume.
+**Where:** `user_keys` and `decrypt_address` in `proton-sdk` (`crates/proton-sdk/src/account.rs`
+in `proton-sdk-rs`)
+
+**Repro:** Not reproduced. An account whose address-key tokens are encrypted to an account key
+that is no longer active cannot open those address keys, and so cannot open the My Files share.
+
+**Cause.** `user_keys` skips every inactive account key, even one the password opens, and the
+address-key tokens are decrypted only with what it returns. `keycheck.rs` in this repository
+already reports "token is for inactive account key", so the case is known. Separately,
+`addresses()` fails as a whole through `?` when one address has no usable primary key, which
+takes the working addresses down with it.
+
+**Fix.** Not done, and it belongs in the SDK. Use every account key that opens for decrypting
+tokens, and only the active ones for signing. Skip and log an address that cannot be opened.
+
+---
+
+### B264 — A mount that fails after starting its workers leaves them running
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #40.
+**Where:** `run_mount` in `crates/pdfs-fuse/src/mount.rs`
+
+**Repro:** Make the mount fail after the workers start: a busy mountpoint, or a control socket
+whose permissions cannot be set. The daemon retries every 5 s, and the drain, sync, sweep,
+probe and index threads of the failed attempt keep running beside the next one.
+
+**Cause.** The early returns after the workers are spawned (the `?` on the socket bind, the
+permission check, a `spawn_session` error, and a `?` on a later thread spawn) skip
+`stop_workers`. The threads hold a `Core`, and the `Core` holds the database. If that keeps
+the `flock` held, every later attempt fails with "another daemon is using cache.db" instead
+of the real error. That part is inferred from the code and not observed.
+
+**Fix.** Not done. Bind the socket and check the mountpoint before any worker starts, and stop
+the workers on every error path.
+
+---
+
+### B263 — A mount that can never succeed retries every 5 s and tells only the journal
+
+**Status:** Open
+**Found:** 2026-10-31, issue #40: the app showed "Connecting… waiting for the Proton Drive
+service" for days, `pdfs diagnose` only reported the control socket missing, and the reporter
+uninstalled.
+**Where:** the mount loop in `crates/pdfs-cli/src/main.rs`; `run_mount` in
+`crates/pdfs-fuse/src/mount.rs`
+
+**Repro:** Start the daemon with a session whose keys cannot open My Files (B265). The journal
+shows `mount failed; retrying in 5s` forever. The app and the tray wait for the service, and
+nothing says why.
+
+**Cause.** Every mount error gets the same 5 s retry, whether it is a network error or one that
+no retry fixes, such as a key or a 4xx answer. Each attempt builds a new client and sends about
+four requests, so a broken account sends tens of thousands a day, which may also feed
+Proton's sign-in blocks (#39). The control socket is bound only after the mount succeeds, and
+the error is written nowhere a front end can read it.
+
+**Fix.** Not done. Back off exponentially, treat key, `KeysLocked` and 4xx errors as permanent
+with a long back-off, and write the last error where the app, the tray and `diagnose` can
+show it (a state file, and `STATUS=` to systemd).
+
+---
+
+### B262 — Watching a large synced folder holds up the sync engine, and a failed watch is never retried
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #53.
+**Where:** `rewatch` and `engine_loop` in `crates/pdfs-fuse/src/sync/engine.rs`
+
+**Repro:** Add a synced folder with many subfolders, or one that holds a symlink to a large
+tree, on a system near `fs.inotify.max_user_watches`. The new folder's first pass waits until
+the recursive watch is set up. When the watch fails, the journal has one `sync: watch failed`
+line, the folder is never watched, and later changes are found only by the two-minute poll.
+
+**Cause.**
+- `rewatch` runs on the engine thread before the reconcile, and notify's recursive watch walks
+  the whole tree, at startup for every folder.
+- notify follows symlinks by default, and the local walk does not.
+- When `watch` fails partway, the watches added before the failure stay registered, but the
+  folder is not recorded as watched. Their events match no folder and become `ReconcileAll`,
+  and they use up watches the next folder needs.
+- Errors the watcher reports later are dropped in its callback.
+
+**Fix.** Not done. Reconcile first, unwatch after a partial failure and retry with a back-off,
+turn off symlink following, and show a watch failure in the folder's state.
+
+---
+
+### B261 — A folder that has never synced reads "up to date"
+
+**Status:** Open
+**Found:** 2026-10-31, issue #53: "In Computers I add the folder. It appears as synced."
+**Where:** `sync_folder` in `crates/pdfs-core/src/db/migrations.rs`; `sync_state_label` in
+`crates/pdfs-gui/src/app/pages/devices.rs`; the location rows in
+`crates/pdfs-gui/src/app/pages/locations.rs`
+
+**Repro:** Add a synced folder. Until its first pass starts, the app shows it as up to date.
+The same happens after a switch from on-demand to mirror, after **Sync From Scratch…**, and for
+every folder while sync is paused for the whole account.
+
+**Cause.** The `state` column defaults to `idle`, and every state the label does not know reads
+"up to date". `last_sync` is 0 for a folder that has never synced, but the rows do not look at
+it, and a test pins the label for that case. The rows only show a folder's own pause, not the
+account-wide one.
+
+**Fix.** Not done. Show "waiting for first sync" when `last_sync` is 0, and show the
+account-wide pause on the folder rows.
+
+---
+
+### B260 — The poll pushes a new folder's first sync behind every other folder
+
+**Status:** Open
+**Found:** 2026-10-31, code audit after issue #53.
+**Where:** `engine_loop` in `crates/pdfs-fuse/src/sync/engine.rs`
+
+**Repro:** Sync a few large mirror folders whose passes take longer than two minutes, then add
+another folder. Its first pass waits until every other folder has been walked again, each
+time.
+
+**Cause.** The poll sends `ReconcileAll` every two minutes whether or not a pass is still
+running. When a burst holds both a `ReconcileAll` and a folder's `Reconcile(id)`, the loop runs
+only `reconcile_all`, which goes in id order. A new folder has the highest id, so it always
+goes last.
+
+**Fix.** Not done. Run the folders asked for by id before the rest, and don't queue a poll
+while a pass runs.
+
+---
+
+### B259 — The sync engine can die or hang, and nothing shows it until a restart
+
+**Status:** Partly fixed. A hung pass is reported but not ended, and a panic outside a pass
+still stops the engine; it is reported, not restarted.
+**Found:** 2026-10-31, issue #53: a newly added folder did not sync until the reporter restarted
+the app. All FUSE workers were idle, nothing was queued, and the warning-level journal was
+empty (B258).
+**Where:** `spawn` and `engine_loop` in `crates/pdfs-fuse/src/sync/engine.rs`;
+`reconcile_pass` in `crates/pdfs-fuse/src/sync.rs`; `crates/pdfs-fuse/src/diagnostics.rs`
+
+**Repro:** Not reproduced. Make one pass panic, or block in a call that does not return. Every
+later add, `pdfs sync now`, file event and poll is dropped without a word. The folder that was
+syncing stays `syncing` with its last progress. A restart runs a pass over every folder, which
+is why it helps.
+
+**Cause.**
+- The engine is one thread, and nothing catches a panic in a pass. When it unwinds, the
+  receiver is gone and every `let _ = sync_tx.send(..)` fails silently. The poll thread stops
+  at its first failed send.
+- The thread's `JoinHandle` is checked only at shutdown.
+- A pass has no overall deadline. Each request is bounded, but a pass is not; B165 dealt with
+  the stop only.
+- Nothing logs a pass starting, or ending without changes. `Diagnostics` covers the FUSE
+  workers and the request queue, not this thread, so "workers idle, nothing queued" says
+  nothing about sync.
+- A database error when the engine reads a folder drops that folder's request without a log.
+
+**Fix.**
+- Each pass runs under `catch_unwind` (`EngineHealth::contain` in
+  `crates/pdfs-fuse/src/sync/engine.rs`). A panic ends that pass only: its progress is cleared,
+  the folder is set to `error`, the activity feed says so, and the next poll tries again.
+- `Diagnostics` carries the engine's state: running or not, the folder of the running pass, how
+  long it has run and how long since it last reported progress, and how many passes panicked.
+  `pdfs diagnostics` prints it as `sync engine: …`.
+- The supervisor warns when the engine thread has ended, and when a pass has reported no
+  progress for 15 minutes.
+- A first pass logs its start and end at info, as does any pass that changed something or
+  took 30 s or more. A request for a folder the database cannot read is logged.
+- Not done: a deadline for a pass, and restarting an engine thread that has ended. The
+  channel's receiver ends with the thread, so a restart needs a new channel in every `Core`
+  clone.
+
+**Test:** `a_panicking_pass_is_contained_and_counted`, `the_running_pass_is_reported` and
+`the_engine_reads_as_stopped_once_its_thread_ends` in `pdfs-fuse`;
+`a_stopped_sync_engine_is_a_stall` and `only_a_quiet_sync_pass_is_a_stall` in the supervisor.
+
+---
+
+### B258 — `journalctl -p warning` shows nothing, whatever the daemon logged
+
+**Status:** Fixed, not verified live
+**Found:** 2026-10-31, issue #53: the reporter ran `journalctl --user -u proton-drive.service -b
+-p warning`, as `docs/TROUBLESHOOTING.md` tells them to, and got `-- No entries --`.
+**Where:** `main` in `crates/pdfs-cli/src/main.rs`; `packaging/proton-drive.service`
+
+**Repro:** Make the daemon log a warning, then run the command above. It prints no entries.
+Without `-p` the warning is there.
+
+**Cause.** The daemon logs with plain `tracing_subscriber::fmt()` to standard output. journald
+stores every line of a service's output at the unit's default priority, info, unless the line
+starts with a `<N>` prefix. So every `WARN` and `ERROR` line is stored as info, and the
+troubleshooting guide's filter hides all of them.
+
+**Fix.** When standard output is the journal stream (`JOURNAL_STREAM` names the same
+device and inode as fd 1), each line starts with the `<N>` prefix for its level, and ANSI colours
+are off. A terminal that merely inherited `JOURNAL_STREAM` keeps the plain format
+(`crates/pdfs-cli/src/journal.rs`).
+
+**Test:** `each_line_opens_with_the_priority_of_its_level` and
+`journal_stream_must_name_the_same_file` in `pdfs-cli`. On 2026-10-31, `pdfs diagnose` run with
+`RUST_LOG=debug` under `systemd-run --user -p StandardOutput=journal` stored its debug lines at
+`PRIORITY=7` and its report at 6.
+
+---
+
 ### B256 — `pdfs copy` right after a save copies the old version
 
 **Status:** Fixed, not verified live
@@ -402,14 +796,20 @@ folder lost its files is not known yet.
 
 **Fix.** The push pass for a switch to on-demand forgets the baseline rows of a local copy that
 is gone in full, instead of trashing them on Drive, so the switch goes ahead and the mount shows
-what Drive has. **Sync From Scratch…** in the app and `pdfs sync reset ID` clear a mirror
+what Drive has. A switch asked for before any pass saw the folder empty found it still `idle`,
+and the check for what only this computer has refused it at once: every path read as "deleted
+here but not on Proton Drive yet". The account run found that. Such a switch now waits for the
+same push pass (`mirror_tree_gone` in `crates/pdfs-fuse/src/sync.rs`, checked in
+`apply_sync_folder_mode`). **Sync From Scratch…** in the app and `pdfs sync reset ID` clear a mirror
 folder's baseline, so the next pass compares both sides as on the first sync: one-sided files
 are copied across, files that differ keep both versions, and nothing is deleted. Restore now
 logs why it skipped a folder.
 
 **Test:** The simulations `a_folder_whose_local_copy_is_gone_still_goes_on_demand` (which
-failed in exactly the reported state before the fix) and
+failed in exactly the reported state before the fix),
-`a_folder_whose_local_copy_is_gone_downloads_again_after_a_reset`.
+`a_folder_emptied_before_any_pass_still_goes_on_demand` (which failed with the account run's
+error) and `a_folder_whose_local_copy_is_gone_downloads_again_after_a_reset`; the acceptance case
+"an emptied mirror folder switches to on-demand".
 
 ---
 
@@ -1517,6 +1917,8 @@ what it holds. What was synced in it is still deleted.
 ### B210 — After a password reset, the mount retries "missing key" forever
 
 **Status:** Fixed, not verified live
+**See also:** B265. The account in issue #40 has an active volume, so this fix does not run for
+it; its "missing key" comes from address keys that do not open.
 **Found:** 2026-10-15, issue #40: on a fresh 3.4.0 install the sign-in worked, but the daemon
 logged `mount failed: fetch My Files root: cryptography error: failed to decrypt: missing key`
 every 5 seconds. The app stayed on "Connecting…" because the daemon never got far enough to
@@ -1662,6 +2064,7 @@ front-end is the stale one, and restarting the service would not help.
 ### B205 — A photo upload the SDK refuses says "You're offline"
 
 **Status:** Fixed, not verified live
+**See also:** B266, the same misclassification on the pin, unpin, search and node-load paths.
 **Found:** 2026-10-11, issue #38: uploading an image from the Photos page showed "You're offline"
 while other uploads went through. Each `upload_photo` failed about 5 µs after it started, with no
 request sent, and the journal gave no reason.
@@ -1746,6 +2149,7 @@ taken as this session's, so the daemon keeps writing its later rotations.
 ### B202 — A refused session shows as offline forever, and nothing says to sign in again
 
 **Status:** Fixed, not verified live
+**See also:** B267. Other errors at a start from a warm cache still mount as offline.
 **Found:** 2026-10-09, issue #35: the tray and `pdfs diagnose` said "offline, 3 queued", and
 diagnose also said "keyring session: ok", while every call in the log failed with
 `InvalidRefreshToken (http 400)`. `pdfs sync now` and restarting the service changed nothing.
@@ -2687,6 +3091,8 @@ fix).
 ### B165 — A stop waits on a stuck thread until systemd kills the daemon
 
 **Status:** Fixed (unverified).
+**See also:** B259. A pass still has no deadline while the daemon runs, and a stuck or dead
+sync engine is not reported.
 **Found:** 2026-10-04, by the account run on 2.10.0 (cleanup after on-demand pairing 2). The
 daemon was stopped at 15:53:04 and logged "control socket closing", but never "sync engine
 stopping" or "daemon stopping". systemd killed it 15 s later (`TimeoutStopSec`). The run's

docs/CHANGELOG.md

@@ -11,7 +11,7 @@ scratch (user data in `staging/` and `recovery/` is never touched by this).
 
 ## [Unreleased]
 
-## [3.6.0] — 2026-10-26
+## [3.6.0] — 2026-10-27
 
 Schema: **44**, unchanged.
 
@@ -46,6 +46,9 @@ Schema: **44**, unchanged.
   file on one side only is copied to the other, and a file that differs keeps both versions.
   Nothing is deleted. From the terminal: `pdfs sync reset ID`.
 
+- **`--json` for `pdfs members`, `pdfs du` and `pdfs public-link create` / `update`**, so scripts
+  can read a link's id, role, password flag and expiry, and a folder's size and item count.
+
 ### Changed
 - **Copying a file inside the mount is faster** when the computer already has the file, for
   example with `cp` or a file manager: the copy is made on this computer, about four times
@@ -58,14 +61,19 @@ Schema: **44**, unchanged.
   pages for files, synced folders, Photos, sharing, computers, and the launcher and tray.
   Installation puts the COPR repository first for Fedora and explains updating and uninstalling
   for each kind of package. Each release publishes `docs/` to the wiki.
+- **Acceptance cases for the 3.6.0 features:** `copy_file_range` over several calls and at
+  offsets, `pdfs copy` (including B256), `pdfs du`, `pdfs public-link update`, Sync From Scratch,
+  and the switch of an emptied mirror folder to on-demand (B255). `docs/TESTING.md` lists what to
+  check by hand in the app.
 
 ### Fixed
 
 - **A synced folder whose files were all gone from this computer no longer gets stuck** (#46).
   The sync still refuses to delete everything on Proton Drive, but a switch to online only now
-  goes ahead and shows what Proton Drive has, instead of waiting for good. To download the
+  goes ahead and shows what Proton Drive has, instead of waiting for good. This includes a
-  files again instead, sync the folder from scratch. Restoring folders also logs why it
+  switch asked for right after the files went, which was refused with "… was deleted here but
-  skipped a folder.
+  not on Proton Drive yet". To download the files again instead, sync the folder from scratch.
+  Restoring folders also logs why it skipped a folder.
 
 - **The first sync of a folder shows how far its scan got** (#46). Before anything downloads,
   the first pass reads every item on Proton Drive, which takes many minutes for a large folder.

docs/CLI.md

@@ -190,8 +190,9 @@ commands are for scripts and for cases where the mount is not available.
 ## Scripting with `--json`
 
 The global `--json` flag makes query commands print JSON: `status`, `ls`, `pins`, `sync list`,
-`devices list`, `locations`, `transfers`, `activity`, `trash` and `cache inspect`. Commands that change
+`devices list`, `locations`, `transfers`, `activity`, `trash`, `cache inspect`, `members` and `du`.
-something keep their human-readable output; check their exit code.
+`public-link create` and `public-link update` print the link they made or changed. Other commands
+that change something keep their human-readable output; check their exit code.
 
 ```bash
 pdfs --json status | jq -r '.mount.mountpoint'

docs/TESTING.md

@@ -116,7 +116,10 @@ for something a network filesystem cannot do.
    the move cases in every pairing of on-demand and mirror. Before a folder switches to on-demand,
    a new file is written into it; once mounted, the file must be listed with its bytes. In every
    pairing each folder must still hold the file written into it at setup.
-4. Removes everything it made, locally and on Drive, and reports `cleanup`. A run that leaves
+4. Registers a third sync folder for the recovery cases (`account` in `--list`): Sync From Scratch
+   must change nothing that already matched, and a mirror folder whose local files are all gone
+   must still switch to on-demand, with every file intact on Drive (B255).
+5. Removes everything it made, locally and on Drive, and reports `cleanup`. A run that leaves
    anything behind fails.
 
 Cleanup finds remote folders by uid, never by name, so nothing of yours is touched. It removes
@@ -199,6 +202,15 @@ Besides the syscall contract:
   both directions, several sources in one `pdfs move`, and a tree through My files and out again.
   The refusals must move nothing and lose nothing: a name already taken, a folder into itself, a
   mirrored source holding something Drive lacks, a file still open for writing.
+- **`copy_file_range`.** A 17 MiB copy that takes several calls, copies into the middle of a file
+  and past its end, a short copy at the source's end, and a copy from a file whose writes are not
+  released yet. On a live mount the results are also read back from Drive.
+- **Copies, sizes and links on Drive** (My files only). `pdfs copy` of a tree and of a file beside
+  itself, read back as listed and after `pdfs refresh`, with nothing queued; the refusal while a
+  file has writes Drive lacks, and never the version before a save (B256). `pdfs du` counts every
+  item below a folder and keeps counting one moved to the trash. `pdfs public-link update` keeps
+  the URL and every option it was not asked to change, and refuses a link id that is not the
+  folder's.
 - **The CLI.** `pdfs` into a closed pipe exits 0 with nothing on stderr; `pdfs mkdir`, `rename`
   and `rm` by local path, and their refusals.
 
@@ -263,3 +275,21 @@ typo it is. A release run leaves it unset.
 
 What no automated run covers yet is listed under
 [Verification still owed](ROADMAP.md#verification-still-owed).
+
+### By hand in the app
+
+The suite drives the CLI, not the app. Before a release that changes one of these screens, check
+it by hand on a test account:
+
+1. **Make a Copy** on a file in My files: the copy appears beside it with ` (1)`, and opens with
+   the same content. **Copy To…** a folder into another folder: the whole tree arrives.
+2. Make a Copy on a file that is still open in an editor with unsaved changes: the app refuses,
+   and no copy appears.
+3. **Details** of a folder: **Size on Proton Drive** shows a size and an item count, and its
+   tooltip says items in the trash are counted. Details of a file still shows **Size**.
+4. **Share → Link settings** on a link with a password: change **Link role**. The link in the
+   dialog stays the same, and **Remove the password** is still offered. Then remove the password
+   and pick an expiry under **Expires**: the link row shows when it expires.
+5. **Sync From Scratch…** on a mirror folder: after the pass, the folder holds the same files and
+   no conflict copies.
+6. Each of the above in a second language (`LANGUAGE=de pdfs-app`): no English left.

packaging/aur/proton-drive-for-linux-bin/.SRCINFO

@@ -1,6 +1,6 @@
 pkgbase = proton-drive-for-linux-bin
 	pkgdesc = Unofficial Proton Drive client: FUSE files-on-demand mount, CLI, GTK4 app, tray (binaries)
-	pkgver = 3.5.0
+	pkgver = 3.6.0
 	pkgrel = 1
 	url = https://proton-drive.narl.io
 	install = proton-drive.install
@@ -22,21 +22,21 @@ pkgbase = proton-drive-for-linux-bin
 	optdepends = xdg-utils: "Open folder" action in the tray menu
 	optdepends = fzf: search-as-you-type launcher (pdfs-prompt --fzf)
 	optdepends = foot: terminal that hosts pdfs-prompt --fzf when started from a keybinding
-	provides = proton-drive-for-linux=3.5.0
+	provides = proton-drive-for-linux=3.6.0
-	provides = proton-drive-linux=3.5.0
+	provides = proton-drive-linux=3.6.0
 	provides = pdfs
 	conflicts = proton-drive-linux
 	conflicts = proton-drive-for-linux
 	conflicts = proton-drive-for-linux-git
 	options = !strip
 	options = !debug
-	source = proton-drive-linux-3.5.0-x86_64.tar.gz::https://github.com/narrrl/proton-drive-linux/releases/download/v3.5.0/proton-drive-linux-3.5.0-x86_64.tar.gz
+	source = proton-drive-linux-3.6.0-x86_64.tar.gz::https://github.com/narrrl/proton-drive-linux/releases/download/v3.6.0/proton-drive-linux-3.6.0-x86_64.tar.gz
-	source = io.narl.proton-drive-linux-3.5.0.desktop::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.5.0/packaging/io.narl.proton-drive-linux.desktop
+	source = io.narl.proton-drive-linux-3.6.0.desktop::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.6.0/packaging/io.narl.proton-drive-linux.desktop
-	source = io.narl.proton-drive-linux-tray-3.5.0.desktop::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.5.0/packaging/io.narl.proton-drive-linux-tray.desktop
+	source = io.narl.proton-drive-linux-tray-3.6.0.desktop::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.6.0/packaging/io.narl.proton-drive-linux-tray.desktop
-	source = io.narl.proton-drive-linux-3.5.0.svg::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.5.0/packaging/io.narl.proton-drive-linux.svg
+	source = io.narl.proton-drive-linux-3.6.0.svg::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.6.0/packaging/io.narl.proton-drive-linux.svg
-	source = proton-drive-3.5.0.service::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.5.0/packaging/proton-drive.service
+	source = proton-drive-3.6.0.service::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.6.0/packaging/proton-drive.service
-	source = LICENSE-3.5.0::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.5.0/LICENSE
+	source = LICENSE-3.6.0::https://raw.githubusercontent.com/narrrl/proton-drive-linux/v3.6.0/LICENSE
-	sha256sums = 902f60de5f471cb15c84d0ecb29cb4644a0ac52ce36d2be54c16b4befeba8de0
+	sha256sums = 8e9b76b0df238af1c8978c33b4c27c0c548e1faa81b368d0d271ed564d0a76c7
 	sha256sums = d190d6771fff0b975271fb62fd3fb0fa8bbf17d7278c10853c18557855b0c123
 	sha256sums = 1d95e250370220e3bb6aead6ce34d1d6cc759f42c4803b75f1667e78ff47c6c0
 	sha256sums = e598a93c2715c3a9fdc7fb937902083d4a1135e8fbdfe6fe7e37f0383ebbd828

packaging/aur/proton-drive-for-linux-bin/PKGBUILD

@@ -1,7 +1,7 @@
 # Maintainer: Nils Pukropp <contact@narl.io>
 
 pkgname=proton-drive-for-linux-bin
-pkgver=3.5.0
+pkgver=3.6.0
 pkgrel=1
 pkgdesc="Unofficial Proton Drive client: FUSE files-on-demand mount, CLI, GTK4 app, tray (binaries)"
 arch=('x86_64')
@@ -36,7 +36,7 @@ source=("proton-drive-linux-$pkgver-x86_64.tar.gz::$_repo/releases/download/$_ta
         "io.narl.proton-drive-linux-$pkgver.svg::$_raw/packaging/io.narl.proton-drive-linux.svg"
         "proton-drive-$pkgver.service::$_raw/packaging/proton-drive.service"
         "LICENSE-$pkgver::$_raw/LICENSE")
-sha256sums=('902f60de5f471cb15c84d0ecb29cb4644a0ac52ce36d2be54c16b4befeba8de0'
+sha256sums=('8e9b76b0df238af1c8978c33b4c27c0c548e1faa81b368d0d271ed564d0a76c7'
             'd190d6771fff0b975271fb62fd3fb0fa8bbf17d7278c10853c18557855b0c123'
             '1d95e250370220e3bb6aead6ce34d1d6cc759f42c4803b75f1667e78ff47c6c0'
             'e598a93c2715c3a9fdc7fb937902083d4a1135e8fbdfe6fe7e37f0383ebbd828'

packaging/aur/proton-drive-for-linux-git/.SRCINFO

@@ -1,6 +1,6 @@
 pkgbase = proton-drive-for-linux-git
 	pkgdesc = Unofficial Proton Drive client: FUSE files-on-demand mount, CLI, GTK4 app, tray (git)
-	pkgver = 3.5.0.r0.geb25c16
+	pkgver = 3.6.0.r0.g2720191
 	pkgrel = 1
 	url = https://proton-drive.narl.io
 	install = proton-drive.install
@@ -25,8 +25,8 @@ pkgbase = proton-drive-for-linux-git
 	optdepends = xdg-utils: "Open folder" action in the tray menu
 	optdepends = fzf: search-as-you-type launcher (pdfs-prompt --fzf)
 	optdepends = foot: terminal that hosts pdfs-prompt --fzf when started from a keybinding
-	provides = proton-drive-for-linux=3.5.0.r0.geb25c16
+	provides = proton-drive-for-linux=3.6.0.r0.g2720191
-	provides = proton-drive-linux=3.5.0.r0.geb25c16
+	provides = proton-drive-linux=3.6.0.r0.g2720191
 	provides = pdfs
 	conflicts = proton-drive-linux
 	conflicts = proton-drive-for-linux

packaging/aur/proton-drive-for-linux-git/PKGBUILD

@@ -1,7 +1,7 @@
 # Maintainer: Nils Pukropp <contact@narl.io>
 
 pkgname=proton-drive-for-linux-git
-pkgver=3.5.0.r0.geb25c16
+pkgver=3.6.0.r0.g2720191
 pkgrel=1
 pkgdesc="Unofficial Proton Drive client: FUSE files-on-demand mount, CLI, GTK4 app, tray (git)"
 arch=('x86_64')

packaging/aur/proton-drive-for-linux/.SRCINFO

@@ -1,6 +1,6 @@
 pkgbase = proton-drive-for-linux
 	pkgdesc = Unofficial Proton Drive client: files-on-demand FUSE mount, CLI, GTK4 app and tray
-	pkgver = 3.5.0
+	pkgver = 3.6.0
 	pkgrel = 1
 	url = https://proton-drive.narl.io
 	install = proton-drive.install
@@ -24,13 +24,13 @@ pkgbase = proton-drive-for-linux
 	optdepends = xdg-utils: "Open folder" action in the tray menu
 	optdepends = fzf: search-as-you-type launcher (pdfs-prompt --fzf)
 	optdepends = foot: terminal that hosts pdfs-prompt --fzf when started from a keybinding
-	provides = proton-drive-linux=3.5.0
+	provides = proton-drive-linux=3.6.0
 	provides = pdfs
 	conflicts = proton-drive-linux
 	conflicts = proton-drive-for-linux-bin
 	conflicts = proton-drive-for-linux-git
 	options = !lto
-	source = proton-drive-for-linux-3.5.0.tar.gz::https://github.com/narrrl/proton-drive-linux/archive/refs/tags/v3.5.0.tar.gz
+	source = proton-drive-for-linux-3.6.0.tar.gz::https://github.com/narrrl/proton-drive-linux/archive/refs/tags/v3.6.0.tar.gz
-	sha256sums = 5eb0e001ec2301ffb8b2b8429e907fab32810d6eba541bf978a0ea97867d8bc9
+	sha256sums = d9b16b1027816a379d6a11c6396d779f751a6f94becaa16b17439420f561d13d
 
 pkgname = proton-drive-for-linux

packaging/aur/proton-drive-for-linux/PKGBUILD

@@ -1,7 +1,7 @@
 # Maintainer: Nils Pukropp <contact@narl.io>
 
 pkgname=proton-drive-for-linux
-pkgver=3.5.0
+pkgver=3.6.0
 pkgrel=1
 pkgdesc="Unofficial Proton Drive client: files-on-demand FUSE mount, CLI, GTK4 app and tray"
 arch=('x86_64')
@@ -26,7 +26,7 @@ options=('!lto')
 # Stops the running daemon before removal, so the mount stops mirroring deletes.
 install=proton-drive.install
 source=("$pkgname-$pkgver.tar.gz::$_repo/archive/refs/tags/v$pkgver.tar.gz")
-sha256sums=('5eb0e001ec2301ffb8b2b8429e907fab32810d6eba541bf978a0ea97867d8bc9')
+sha256sums=('d9b16b1027816a379d6a11c6396d779f751a6f94becaa16b17439420f561d13d')
 
 _srcname="proton-drive-linux-$pkgver"
 

scripts/fuse-acceptance.py

@@ -566,6 +566,357 @@ def test_mmap_and_copy_paths(ctx: Context) -> None:
         )
 
 
+def _copy_range(ctx: Context, key: str, src: int, dst: int, count: int, offset_src: int, offset_dst: int) -> int | None:
+    """`copy_file_range` until `count` bytes moved or the source ran out.
+
+    Returns how many bytes moved, or None when the first call was refused
+    cleanly. The mount copies at most 16 MiB a call, and `cp` loops the same
+    way, so a large copy reaches it as several calls with growing offsets.
+    """
+    moved = 0
+    first = ctx.probe(
+        key,
+        lambda: os.copy_file_range(src, dst, count, offset_src, offset_dst),
+        allow=CLEAN_UNSUPPORTED | {errno.EXDEV},
+    )
+    if not first.ok:
+        return None
+    step = first.value
+    calls = 1
+    while step and moved + step < count:
+        moved += step
+        step = os.copy_file_range(src, dst, count - moved, offset_src + moved, offset_dst + moved)
+        calls += 1
+    ctx.note(f"{key}.calls", calls)
+    return moved + step
+
+
+def test_copy_file_range_ranges(ctx: Context) -> None:
+    """`copy_file_range` beyond the first call, at offsets, and from an open file.
+
+    The mount answers the call from bytes this machine already has: the write
+    handle's scratch, a pending upload, or the cache. Each answer is a write
+    into the destination, so it has to land exactly where the offsets say,
+    fill a gap past the end with zeros, and survive the upload.
+    """
+    root = ctx.root
+    big = pattern(17 * 1024 * 1024 + 4099, "cfr-big")
+    source = root / "cfr-source.bin"
+    write_durable(source, big)
+
+    def copy(key: str, src_path: Path, dst_path: Path, count: int, offset_src: int = 0, offset_dst: int = 0) -> int | None:
+        src = os.open(src_path, os.O_RDONLY)
+        dst = os.open(dst_path, os.O_CREAT | os.O_WRONLY, 0o600)
+        try:
+            moved = _copy_range(ctx, key, src, dst, count, offset_src, offset_dst)
+            os.fsync(dst)
+        finally:
+            os.close(src)
+            os.close(dst)
+        return moved
+
+    expected: dict[Path, bytes] = {}
+
+    whole = root / "cfr-whole.bin"
+    moved = copy("whole", source, whole, len(big))
+    if moved is not None:
+        check(moved == len(big), f"whole: copy_file_range moved {moved} bytes, expected {len(big)}")
+        expected[whole] = big
+
+    # Into the middle of a file that exists, and past the end of another.
+    middle = root / "cfr-middle.bin"
+    base = pattern(300_000, "cfr-base")
+    write_durable(middle, base)
+    moved = copy("middle", source, middle, 100_000, offset_src=5_000_000, offset_dst=123_457)
+    if moved is not None:
+        check(moved == 100_000, f"middle: copy_file_range moved {moved} bytes, expected {100_000}")
+        expected[middle] = base[:123_457] + big[5_000_000:5_100_000] + base[223_457:]
+    gap = root / "cfr-gap.bin"
+    write_durable(gap, b"head")
+    moved = copy("gap", source, gap, 70_001, offset_src=1, offset_dst=200_000)
+    if moved is not None:
+        check(moved == 70_001, f"gap: copy_file_range moved {moved} bytes, expected {70_001}")
+        expected[gap] = b"head" + bytes(200_000 - 4) + big[1:70_002]
+
+    # Past the source's end the copy is short, and at it nothing moves.
+    tail = root / "cfr-tail.bin"
+    moved = copy("tail", source, tail, 10_000, offset_src=len(big) - 99)
+    if moved is not None:
+        check(moved == 99, f"tail: copy_file_range moved {moved} bytes, expected {99}")
+        expected[tail] = big[-99:]
+
+    # From a file whose last write has not been released yet.
+    unsaved = root / "cfr-unsaved.bin"
+    fresh = pattern(600_001, "cfr-unsaved")
+    writer = os.open(unsaved, os.O_CREAT | os.O_RDWR | os.O_TRUNC, 0o600)
+    try:
+        write_all(writer, fresh)
+        moved = copy("unsaved", unsaved, root / "cfr-from-unsaved.bin", len(fresh))
+    finally:
+        os.close(writer)
+    if moved is not None:
+        check(moved == len(fresh), f"unsaved: copy_file_range moved {moved} bytes, expected {len(fresh)}")
+        expected[root / "cfr-from-unsaved.bin"] = fresh
+
+    def verify(when: str) -> None:
+        for path, data in expected.items():
+            size = os.lstat(path).st_size
+            check(size == len(data), f"{path.name} {when}: {size} bytes, expected {len(data)}")
+            check_bytes(read(path), data, f"{path.name} {when}")
+
+    verify("right after the copy")
+    if not ctx.is_live or ctx.daemon is None:
+        return
+    ctx.daemon.wait_for_queue()
+    verify("after the upload")
+    # A server-side copy has a new uid, so nothing of it is cached: reading
+    # it reads what Drive holds.
+    if _my_files_root(ctx) is None:
+        return
+    landed = root / "cfr-landed"
+    landed.mkdir()
+    ctx.daemon.wait_for_queue()
+    for path in expected:
+        _pdfs_copy(ctx.daemon, path, landed)
+    for path, data in expected.items():
+        check_bytes(read(landed / path.name), data, f"{path.name} as Drive holds it")
+
+
+def _my_files_root(ctx: Context) -> Path | None:
+    """The My files mount the case runs in, or None anywhere else.
+
+    `pdfs copy`, `pdfs du` and public links address a path inside My files;
+    synced folders have no path of their own there.
+    """
+    if ctx.daemon is None:
+        return None
+    mountpoint = (ctx.daemon.status().get("mount") or {}).get("mountpoint")
+    if not mountpoint:
+        return None
+    mountpoint = Path(mountpoint).resolve()
+    return mountpoint if mountpoint in ctx.root.resolve().parents else None
+
+
+def _require_my_files(ctx: Context) -> Daemon:
+    daemon = ctx.require_daemon()
+    if _my_files_root(ctx) is None:
+        raise Skip("needs a root inside My files")
+    return daemon
+
+
+COPIED_TO = re.compile(r"^copied to (.+)$")
+
+
+def _pdfs_copy(daemon: Daemon, source: Path, dest: Path) -> str:
+    """`pdfs copy`, returning the name the copy got."""
+    message = daemon.command("copy", str(source), str(dest)).strip()
+    match = COPIED_TO.match(message)
+    check(match is not None, f"pdfs copy {source.name}: unexpected reply {message!r}")
+    return match[1]
+
+
+def _pdfs_copy_refused(daemon: Daemon, source: Path, dest: Path) -> str | None:
+    """`pdfs copy` expected to be refused for changes Drive lacks: the refusal,
+    or None if the copy went ahead (and returned its name in the log)."""
+    try:
+        daemon.command("copy", str(source), str(dest))
+    except RuntimeError as error:
+        detail = str(error)
+        check("have not reached Proton Drive" in detail, f"pdfs copy {source.name}: unexpected refusal: {detail}")
+        return detail
+    return None
+
+
+def test_server_copy(ctx: Context) -> None:
+    """`pdfs copy` makes an exact copy on Drive and uploads nothing.
+
+    A tree and a lone file are copied; the file into its own folder, where
+    its name is taken and the copy gets the next free one. The copy is read
+    back as listed and again after its listing is dropped, and nothing of it
+    may wait in the queue: Drive made it, so there is nothing to send.
+    """
+    daemon = _require_my_files(ctx)
+    root = ctx.root
+    name = f"tree-{uuid.uuid4().hex[:8]}"
+    files = _move_tree(root, name)
+    dest = root / "copies"
+    dest.mkdir()
+    daemon.wait_for_queue()
+
+    check(_pdfs_copy(daemon, root / name, dest) == name, f"the copy of {name} was renamed")
+    note = root / name / "note.txt"
+    twin = _pdfs_copy(daemon, note, note.parent)
+    check(twin != note.name, f"the copy of {note.name} beside it kept the name {twin!r}")
+    check((note.parent / twin).is_file(), f"{twin} is not listed beside {note.name}")
+    queued = [
+        item
+        for item in daemon.queue()
+        if root.name in (parts := Path(item.get("path", "")).parts) and ("copies" in parts or twin in parts)
+    ]
+    check(not queued, f"a server copy queued work: {_describe_uploads(queued)}")
+
+    def verify(when: str) -> None:
+        for relative, data in files.items():
+            size = os.lstat(dest / relative).st_size
+            check(size == len(data), f"{relative} {when}: {size} bytes, expected {len(data)}")
+            check_bytes(read(dest / relative), data, f"{relative} {when}")
+        check((dest / name / "empty-dir").is_dir(), f"the empty folder is missing {when}")
+        check_bytes(read(note.parent / twin), files[Path(name) / "note.txt"], f"{twin} {when}")
+
+    verify("right after the copy")
+    folders = sorted({dest / relative.parent for relative in files} | {dest / name, note.parent})
+    for folder in folders:
+        daemon.command("refresh", str(folder))
+    verify("after dropping the cached listing")
+    _unchanged_at(root, files, "after copying it")
+
+
+def _unchanged_at(root: Path, files: dict[Path, bytes], what: str) -> None:
+    for relative, data in files.items():
+        check_bytes(read(root / relative), data, f"{relative} {what}")
+
+
+def test_server_copy_never_copies_an_old_version(ctx: Context) -> None:
+    """`pdfs copy` of a file being written is refused, and never copies the
+    version before the last save (B256).
+
+    Drive copies what it holds. A file open with unsaved writes, or saved but
+    not yet uploaded, holds more here than there: the copy has to wait.
+    """
+    daemon = _require_my_files(ctx)
+    root = ctx.root
+    path = root / "being-written.txt"
+    write_durable(path, b"first version")
+    # Its own folder: every case of a run shares the root, and "pdfs copy"
+    # already made "copies" there.
+    dest = root / "b256-copies"
+    dest.mkdir()
+    daemon.wait_for_queue()
+
+    fd = os.open(path, os.O_WRONLY | os.O_TRUNC)
+    try:
+        write_all(fd, b"second version, still open")
+        check(
+            _pdfs_copy_refused(daemon, path, dest) is not None,
+            "pdfs copy went ahead while the file had unsaved writes",
+        )
+        check(not (dest / path.name).exists(), "a refused copy left a file behind")
+    finally:
+        os.close(fd)
+
+    # Right after the close: refused while the upload is owed, then the new
+    # bytes. Never the first version.
+    saved = b"third version, saved"
+    write_durable(path, saved)
+    deadline = time.monotonic() + daemon.timeout
+    refusals = 0
+    while _pdfs_copy_refused(daemon, path, dest) is not None:
+        refusals += 1
+        check(time.monotonic() < deadline, f"pdfs copy was still refused after {daemon.timeout}s")
+        time.sleep(1)
+    ctx.note("refusals before the upload landed", refusals)
+    check_bytes(read(dest / path.name), saved, "the copy made right after a save")
+
+
+def test_folder_size(ctx: Context) -> None:
+    """`pdfs du` counts exactly what is below a folder, trash included.
+
+    Drive adds the size up from encrypted bytes, so it is at least the sum of
+    the files. A file moved to the trash still counts, as `pdfs du` says.
+    """
+    daemon = _require_my_files(ctx)
+    root = ctx.root
+    name = f"sized-{uuid.uuid4().hex[:8]}"
+    files = _move_tree(root, name)
+    folder = root / name
+    items = sum(1 for _ in folder.rglob("*"))
+    daemon.wait_for_queue()
+
+    def size() -> dict:
+        return json.loads(daemon.command("du", str(folder), json_output=True))
+
+    # Drive may add a new tree up a moment after it lands.
+    deadline = time.monotonic() + daemon.timeout
+    while (answer := size())["items"] != items and time.monotonic() < deadline:
+        time.sleep(2)
+    check(answer["items"] == items, f"pdfs du counts {answer['items']} items, expected {items}")
+    total = sum(len(data) for data in files.values())
+    check(answer["size"] >= total, f"pdfs du reports {answer['size']} bytes for {total} bytes of files")
+    ctx.info(f"{answer['size']} bytes on Drive for {total} bytes in {items} items")
+
+    os.unlink(folder / "note.txt")
+    daemon.wait_for_queue()
+    check(size()["items"] == items, "a file moved to the trash stopped counting in pdfs du")
+
+
+def _public_link(daemon: Daemon, path: Path) -> dict | None:
+    return json.loads(daemon.command("members", str(path), json_output=True)).get("link")
+
+
+def _link_token(url: str | None) -> str:
+    """The part of a public link's URL that names the link, without the
+    password fragment."""
+    check(bool(url), "the link has no URL")
+    return url.split("#", 1)[0]
+
+
+def test_public_link_update(ctx: Context) -> None:
+    """`pdfs public-link update` changes a link and keeps its URL.
+
+    Each option changed alone leaves the others as they were: a role change
+    keeps the password, removing the password keeps the expiry. A link id
+    that is not the folder's link is refused.
+    """
+    daemon = _require_my_files(ctx)
+    folder = ctx.root / "linked"
+    folder.mkdir()
+    write_durable(folder / "inside.txt", b"behind a public link")
+    daemon.wait_for_queue()
+
+    password = f"pw-{uuid.uuid4().hex[:12]}"
+    created = json.loads(
+        daemon.command("public-link", "create", str(folder), "--password", password, json_output=True)
+    )["link"]
+    link_id, token = created["id"], _link_token(created["url"])
+    try:
+        check(created["has_password"], "the new link has no password")
+
+        def update(*args: str) -> dict:
+            link = json.loads(
+                daemon.command("public-link", "update", str(folder), link_id, *args, json_output=True)
+            )["link"]
+            check(link["id"] == link_id, f"the update replaced the link: {link['id']} for {link_id}")
+            if link.get("url"):
+                check(_link_token(link["url"]) == token, "the update changed the link's URL")
+            listed = _public_link(daemon, folder)
+            check(listed is not None and listed["id"] == link_id, f"the link is gone after the update: {listed}")
+            return listed
+
+        listed = update("--role", "editor")
+        check(listed["role"] == "editor", f"the role is {listed['role']} after changing it to editor")
+        check(listed["has_password"], "changing the role removed the password")
+
+        expires = int(time.time()) + 7 * 24 * 3600
+        listed = update("--no-password", "--expires", str(expires))
+        check(not listed["has_password"], "--no-password kept the password")
+        check(listed["expires"] == expires, f"the expiry is {listed['expires']}, expected {expires}")
+        check(listed["role"] == "editor", "removing the password changed the role")
+
+        listed = update("--no-expiry")
+        check(listed["expires"] is None, f"--no-expiry kept the expiry {listed['expires']}")
+
+        try:
+            daemon.command("public-link", "update", str(folder), f"not-{link_id}", "--role", "viewer")
+        except RuntimeError as error:
+            check("not found" in str(error), f"a wrong link id was refused for another reason: {error}")
+        else:
+            check(False, "an update with a wrong link id went ahead")
+        check(_public_link(daemon, folder)["role"] == "editor", "a refused update changed the link")
+    finally:
+        with contextlib.suppress(Exception):
+            daemon.command("public-link", "remove", str(folder), link_id)
+
+
 def test_namespace_and_errors(ctx: Context) -> None:
     root = ctx.root
     a, b = root / "dir-a", root / "dir-b"
@@ -2625,6 +2976,7 @@ TESTS = [
     Case("positioned and vectored I/O", test_positioned_and_vectored_io),
     Case("truncate, growth, sparse ranges, and EOF", test_resize_and_sparse_io),
     Case("mmap and zero-copy copy paths", test_mmap_and_copy_paths),
+    Case("copy_file_range across calls, at offsets, and from an open file", test_copy_file_range_ranges),
     Case("namespace operations and POSIX errors", test_namespace_and_errors),
     Case("open-handle lifetime across unlink and rename", test_open_lifetime),
     Case("names, lookup, stat, and enumeration", test_names_and_enumeration),
@@ -2670,6 +3022,10 @@ TESTS = [
     Case("regression B116: trashing a folder drops the creates queued in its subfolders", test_regression_b116_trashed_folder_drops_deeper_creates, (LIVE,)),
     Case("regression B117: a moved file's queued upload keeps its path", test_regression_b117_moved_upload_keeps_its_path, (LIVE,)),
     Case("regression B119: an uploaded file stays cached", test_regression_b119_uploaded_file_stays_cached, (LIVE,)),
+    Case("pdfs copy: a copy on Drive reads back exactly and uploads nothing", test_server_copy, (LIVE,)),
+    Case("regression B256: pdfs copy never copies the version before a save", test_server_copy_never_copies_an_old_version, (LIVE,)),
+    Case("pdfs du counts what is below a folder, trash included", test_folder_size, (LIVE,)),
+    Case("pdfs public-link update keeps the URL and the options not changed", test_public_link_update, (LIVE,)),
     Case("durability across a daemon restart", test_durability_across_restart, (LIVE,)),
 ]
 
@@ -2942,7 +3298,7 @@ def select_cases(kind: str, pool: list[Case] | None = None) -> list[Case]:
     # typo worth failing on.
     for needle in needles:
         check(
-            any(needle in case.name.lower() for case in TESTS + MOVE_CASES),
+            any(needle in case.name.lower() for case in TESTS + MOVE_CASES + RECOVERY_CASES),
             f"PDFS_ACCEPTANCE_ONLY: {needle!r} matched no tests",
         )
     return [case for case in cases if any(needle in case.name.lower() for needle in needles)]
@@ -3658,30 +4014,36 @@ class Janitor:
         return [
             f"{name} ({entry['uid']}) is still in the trash"
             for entry in matches
-            if not self.purge(entry["uid"], name)
+            if not self.purge(entry["uid"], name, listed=True)
         ]
 
-    def purge(self, uid: str, name: str) -> bool:
+    def purge(self, uid: str, name: str, listed: bool = False) -> bool:
         """Permanently delete one trashed node the run owns, by uid.
 
         By uid and never by name: a name can match something of the user's, a
         uid cannot. The node has to show up in the trash first, which is also
         what proves the trash step before it worked, and it has to be gone from
-        a fresh listing afterwards.
+        a fresh listing afterwards. `listed` says the caller just found it in
+        the trash.
 
         The server's own answer comes first, though: it only deletes a node
         that is in the trash, and it answers per uid. A listing is a whole-trash
         enumeration, which on a large trash can time out on every attempt and
         would otherwise keep a folder the server would delete on request.
         """
-        with contextlib.suppress(Exception):
+        last_error = ""
+        try:
             reply = self.daemon.command("delete-forever", uid, stdin="yes\n")
             if re.search(r"\bpermanently deleted 1 item", reply):
                 print(f"[cleanup] permanently deleted {name}")
                 return True
+        except Exception as error:  # noqa: BLE001 - retried, then reported
+            last_error = f": {error}"
         deadline = time.monotonic() + self.daemon.timeout
-        attempted = False
+        # A node seen in the trash before that delete and gone after it was
-        last_error = ""
+        # deleted by it, whatever it answered. Counting it as never sent kept
+        # waiting for a node that was already gone, and failed the run.
+        attempted = listed
         while True:
             try:
                 if self.daemon.trashed(uid):
@@ -3793,7 +4155,7 @@ class Janitor:
         for entry in trashed:
             if STALE_ROOT.match(entry["name"]) and entry["name"] not in live_names:
                 print(f"[reap] permanently deleting an abandoned root from the trash: {entry['name']}")
-                if not orphan.purge(entry["uid"], entry["name"]):
+                if not orphan.purge(entry["uid"], entry["name"], listed=True):
                     leftovers.append(f"{entry['name']} ({entry['uid']}) is still in the trash")
         return leftovers
 
@@ -3894,7 +4256,7 @@ class ManagedSyncPair:
             raise RuntimeError(
                 f"cannot find {self.pdfs!r}; set PDFS_ACCEPTANCE_PDFS to the CLI binary"
             )
-        if self.paths[0] == self.paths[1]:
+        if len(set(self.paths)) != len(self.paths):
             raise ValueError("managed live paths must be different directories")
         deadline = time.monotonic() + self.timeout
         last_error = None
@@ -4537,6 +4899,138 @@ def run_move_contract(
     return run
 
 
+# --------------------------------------------------------------------------
+# Getting a synced folder unstuck
+# --------------------------------------------------------------------------
+
+
+class RecoveryContext:
+    """One mirror folder of the run's own, for cases that reset or empty it.
+
+    The mode matrix needs its folders' sentinels intact, so these cases get a
+    folder nobody else checks.
+    """
+
+    def __init__(self, pair: ManagedSyncPair, daemon: Daemon) -> None:
+        self.pair = pair
+        self.daemon = daemon
+        self.root = pair.paths[0]
+        self.id = pair.ids[self.root]
+        self.infos: list[str] = []
+
+    def folder(self) -> dict:
+        return next(item for item in self.pair.folders() if Path(item["local_path"]).resolve() == self.root)
+
+    def tree(self) -> tuple[str, dict[Path, bytes]]:
+        """A fresh tree in the folder, with one file named after it, so that a
+        trash entry of it cannot be the user's."""
+        name = f"kept-{uuid.uuid4().hex[:8]}"
+        files = _move_tree(self.root, name)
+        files[Path(name) / f"{name}.txt"] = b"named after its tree " + name.encode()
+        write_durable(self.root / name / f"{name}.txt", files[Path(name) / f"{name}.txt"])
+        return name, files
+
+    def trashed(self, names: set[str]) -> list[str]:
+        self.daemon.command("refresh", "trash")
+        return sorted(entry["name"] for entry in self.daemon.trash() if entry["name"] in names)
+
+
+def test_sync_reset_changes_nothing(rc: RecoveryContext) -> None:
+    """Sync From Scratch compares the folder with Drive again and changes
+    nothing that already matched: no deletes, no conflict copies.
+
+    `pdfs sync reset` forgets the folder's record of what it synced. The next
+    pass then sees every file on both sides with no history, which is the
+    case that must copy what is missing and leave matching files alone.
+    """
+    name, files = rc.tree()
+    rc.pair.force_sync(rc.root)
+    rc.daemon.command("sync", "reset", str(rc.id))
+    # Added after the reset, so the pass after it has to upload it.
+    later = Path(name) / "added-after-the-reset.txt"
+    files[later] = b"only here when the pass starts " + name.encode()
+    write_durable(rc.root / later, files[later])
+    rc.pair.force_sync(rc.root)
+    rc.pair.force_sync(rc.root)
+
+    _unchanged_at(rc.root, files, "after Sync From Scratch")
+    copies = [str(path) for path in rc.root.rglob("*") if "(sync-conflict" in path.name]
+    check(not copies, f"Sync From Scratch made conflict copies: {copies}")
+    trashed = rc.trashed({name, f"{name}.txt"})
+    check(not trashed, f"Sync From Scratch trashed {trashed}")
+    state = rc.folder()
+    check(state["state"] == "idle", f"the folder is {state['state']} after Sync From Scratch")
+
+
+def test_emptied_folder_switches_to_ondemand(rc: RecoveryContext) -> None:
+    """A mirror folder whose local files are all gone switches to online only,
+    and Drive keeps every file (B255, issue #46).
+
+    The wipe guard rightly refuses to pass the local loss on to Drive, but it
+    also blocked the push pass a queued switch runs first, so the switch never
+    landed and the folder stayed in error. Through the mount afterwards, every
+    file has to read back as it was.
+    """
+    names: set[str] = set()
+    files: dict[Path, bytes] = {}
+    for _ in range(2):
+        name, tree = rc.tree()
+        names |= {name, f"{name}.txt"}
+        files.update(tree)
+    rc.pair.force_sync(rc.root)
+    for child in list(rc.root.iterdir()):
+        if child.is_dir() and not child.is_symlink():
+            shutil.rmtree(child)
+        else:
+            child.unlink()
+    rc.daemon.command("sync", "mode", str(rc.id), "ondemand")
+
+    # The folder may pass through error while the guard holds the deletions
+    # back; the switch has to land anyway.
+    deadline = time.monotonic() + rc.pair.timeout
+    while True:
+        state = rc.folder()
+        if state["mode"] == "ondemand" and state.get("pending_mode") is None and is_mountpoint(rc.root):
+            break
+        check(time.monotonic() < deadline, f"the switch to on-demand did not land: {state}")
+        time.sleep(2)
+
+    for relative, data in files.items():
+        data_read = rc.pair.through_outage(lambda relative=relative: read(rc.root / relative), f"reading {relative}", rc.infos)
+        check_bytes(data_read, data, f"{relative} on Drive after the local copy was gone")
+    sentinel = rc.root / "pdfs-mode-preservation.bin"
+    check_bytes(read(sentinel), rc.pair.sentinels[rc.root], f"{sentinel.name} on Drive")
+    trashed = rc.trashed(names)
+    check(not trashed, f"the switch trashed {trashed} on Drive")
+
+
+RECOVERY_CASES = [
+    Case("Sync From Scratch changes nothing that already matched", test_sync_reset_changes_nothing, (LIVE,)),
+    Case("regression B255: an emptied mirror folder switches to on-demand", test_emptied_folder_switches_to_ondemand, (LIVE,)),
+]
+
+
+def run_sync_recovery(janitor: Janitor, args) -> None:
+    """The recovery cases, in a sync folder of their own."""
+    cases = select_cases(LIVE, RECOVERY_CASES)
+    if not cases:
+        return
+    timeout = int(os.environ.get("PDFS_ACCEPTANCE_SYNC_TIMEOUT", "180"))
+    path = janitor.new_sync_folder()
+    pair = ManagedSyncPair([path], timeout)
+    daemon = Daemon.discover(timeout)
+    check(daemon is not None, "the daemon stopped answering")
+    run = Run("sync folder recovery", LIVE, path)
+    REPORT.append(run)
+    announce(run, {"folder": f"mirror, {path}", "cases": describe_cases(LIVE, cases, RECOVERY_CASES)})
+    started = time.monotonic()
+    pair.create()
+    context = RecoveryContext(pair, daemon)
+    run_cases(run, cases, lambda _case: context, max(args.timeout, 8 * timeout), args.fail_fast)
+    run.wall = time.monotonic() - started
+    CONSOLE.fact("result", tally(run.counts(), run.wall))
+
+
 def is_mountpoint(path: Path) -> bool:
     """True for a distinct mount, including FUSE mounts over an existing dir."""
     return os.path.ismount(path)
@@ -4694,6 +5188,8 @@ def main() -> int:
             print(f"{','.join(case.kinds):<18} {case.name}")
         for case in MOVE_CASES:
             print(f"{'managed':<18} {case.name}")
+        for case in RECOVERY_CASES:
+            print(f"{'account':<18} {case.name}")
         return 0
 
     install_interrupt_handlers()
@@ -4814,6 +5310,7 @@ def run_account(reference: Run, args) -> None:
         )
         paths = [janitor.new_sync_folder(), janitor.new_sync_folder()]
         run_managed_matrix(paths, reference, args, janitor)
+        run_sync_recovery(janitor, args)
     finally:
         started = time.monotonic()
         leftovers = janitor.cleanup()