fix(core,app,android,cli,packaging): harden account sign-in and watch-history sync

- Desktop shows Proton's CAPTCHA instead of failing the sign-in: a wry webview in a child process of the app (`pstr-app::verify`), confined to https://*.proton.me, hands the token back and the sign-in is retried. Linux packages and CI gain WebKitGTK 4.1; the Windows zip and MSI ship WebView2Loader.dll, without which a -gnu build does not start. - The desktop keyring splits a secret too long for one entry across several, so a Proton session with many key salts survives Windows' 1280-unit cap. Short secrets stay one entry, so every existing secret still reads. - `WatchSync` runs against a small `HistoryDrive` trait and is tested end to end against an in-memory Drive: two devices, newer wins, no re-upload of an unchanged history, a missing file written again, an unreadable own file never overwritten, a newer-format file left alone. - An installation's file unwritten for 90 days is retired by the next device to sync, after its entries are merged and carried in that device's file. - Removing a share keeps its watch state: sync would bring it back from the other devices anyway, and re-adding the share picks up where it left off. - Watch history syncs once more on desktop exit (bounded to 3 s) and, on Android, through a WorkManager job enqueued when the app leaves the screen. - The second-factor prompts say security keys are not supported.
2026-11-03 16:41:26 +01:00 · 2026-10-06 14:30:15 +02:00
1 parent 26cccd5c63
commit d9ca8f8d60
@@ -23,11 +23,11 @@ jobs:

      - uses: Swatinem/rust-cache@v2.9.1

-      # libmpv for pstr-player.
-      - name: Install libmpv
+      # libmpv for pstr-player, WebKitGTK for the CAPTCHA window.
+      - name: Install libmpv and WebKitGTK
        run: |
          sudo apt-get update
-          sudo apt-get install -y libmpv-dev
+          sudo apt-get install -y libmpv-dev libwebkit2gtk-4.1-dev

      - run: cargo fmt --all -- --check

@@ -76,7 +76,7 @@ jobs:
      - name: Install build dependencies
        run: |
          sudo apt-get update
-          sudo apt-get install -y libmpv-dev rpm
+          sudo apt-get install -y libmpv-dev libwebkit2gtk-4.1-dev rpm

      - name: Gate
        run: |
@@ -107,6 +107,12 @@ windows-sys = "0.61"
 tauri-winrt-notification = "0.8"
 # The exe's own icon resource, which is what Explorer and a taskbar pin draw.
 embed-resource = "3"
+# Proton's CAPTCHA page, which reports success by posting a message to its
+# host, so it needs a webview this app controls. Run in a child process of its
+# own (`pstr-app::verify`): tao and eframe's winit cannot share an event loop.
+# WebKitGTK on Linux, WebView2 on Windows, WKWebView on macOS.
+wry = { version = "0.57", default-features = false, features = ["os-webview"] }
+tao = { version = "0.37", default-features = false, features = ["rwh_06"] }
 rpassword = "7"
 libloading = "0.8"
 lru = "0.18"
@@ -83,7 +83,9 @@ Rust 2024, MSRV 1.96.
 cargo build --release
 ```

-`pstr-player` needs libmpv development headers (`mpv` ≥ 2.0). On Windows those
+`pstr-player` needs libmpv development headers (`mpv` ≥ 2.0), and on Linux
+`pstr-app` needs WebKitGTK 4.1's, for the window Proton's CAPTCHA is shown in.
+On Windows the libmpv ones
 come from the separate **mpv-dev** archive rather than mpv's player build, and
 `libmpv-2.dll` ships next to the executable. The Proton SDK crates come from
 crates.io; nothing here builds against a sibling checkout.
@@ -33,6 +33,7 @@ import io.narl.protonstream.playback.MpvPlaybackState
 import io.narl.protonstream.playback.NativeMpvHost
 import io.narl.protonstream.playback.PlaybackService
 import io.narl.protonstream.settings.SettingsStore
+import io.narl.protonstream.sync.WatchSyncWorker
 import io.narl.protonstream.ui.ProtonStreamApp
 import io.narl.protonstream.ui.theme.AppearanceState
 import io.narl.protonstream.ui.theme.ProtonStreamTheme
@@ -207,6 +208,9 @@ class MainActivity : ComponentActivity() {

    override fun onStop() {
        super.onStop()
+        // Where the viewer stopped is what their other devices want next, and
+        // a process in the background may not live to the next timed sync.
+        if (!isChangingConfigurations) WatchSyncWorker.enqueue(this)
        if (
            !isChangingConfigurations &&
            !isInPictureInPictureMode &&
@@ -0,0 +1,56 @@
+package io.narl.protonstream.sync
+
+import android.content.Context
+import androidx.work.BackoffPolicy
+import androidx.work.Constraints
+import androidx.work.CoroutineWorker
+import androidx.work.ExistingWorkPolicy
+import androidx.work.NetworkType
+import androidx.work.OneTimeWorkRequestBuilder
+import androidx.work.WorkManager
+import androidx.work.WorkerParameters
+import io.narl.protonstream.native.NativeRuntime
+import uniffi.pstr_android.AccountState
+import java.util.concurrent.TimeUnit
+
+/**
+ * One watch-history sync after the app leaves the screen.
+ *
+ * The model's timer only runs while the app is alive, and Android is free to
+ * kill a process in the background without notice — so the position the
+ * viewer stopped at would wait for the next launch to reach their other
+ * devices. Handed to WorkManager instead, it goes as soon as there is a
+ * network, even if the process is gone by then.
+ */
+class WatchSyncWorker(
+    appContext: Context,
+    parameters: WorkerParameters,
+) : CoroutineWorker(appContext, parameters) {
+    override suspend fun doWork(): Result {
+        val engine = NativeRuntime.engine()
+        return runCatching { engine.syncWatchHistory() }.fold(
+            onSuccess = { Result.success() },
+            onFailure = {
+                // Signed out by the engine — the session ended — is not
+                // something a retry fixes; a dropped connection is.
+                val signedOut = runCatching { engine.accountState() }.getOrNull() == AccountState.SignedOut
+                if (signedOut || runAttemptCount >= MAX_ATTEMPTS) Result.failure() else Result.retry()
+            },
+        )
+    }
+
+    companion object {
+        private const val WORK_NAME = "watch-history-sync"
+        private const val MAX_ATTEMPTS = 3
+
+        /** Replacing: one pending sync covers every position saved before it runs. */
+        fun enqueue(context: Context) {
+            val request = OneTimeWorkRequestBuilder<WatchSyncWorker>()
+                .setConstraints(Constraints.Builder().setRequiredNetworkType(NetworkType.CONNECTED).build())
+                .setBackoffCriteria(BackoffPolicy.EXPONENTIAL, 30, TimeUnit.SECONDS)
+                .build()
+            WorkManager.getInstance(context.applicationContext)
+                .enqueueUniqueWork(WORK_NAME, ExistingWorkPolicy.REPLACE, request)
+        }
+    }
+}
@@ -194,13 +194,16 @@ internal fun SignInDialog(account: AccountUiState, actions: AccountActions, onDi
        text = {
            Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
                when (state) {
-                    AccountState.SecondFactor -> OutlinedTextField(
+                    AccountState.SecondFactor -> {
+                        OutlinedTextField(
                            code,
                            { code = it },
-                        label = { Text("Two-factor code") },
+                            label = { Text("Code from your authenticator app") },
                            singleLine = true,
                            keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.NumberPassword),
                        )
+                        Text(SECURITY_KEY_NOTE, style = MaterialTheme.typography.bodySmall)
+                    }
                    AccountState.MailboxPassword -> {
                        Text(
                            "This account has a separate mailbox password. It unlocks your files.",
@@ -329,6 +332,11 @@ private fun VerificationDialog(url: String, onToken: (String) -> Unit, onDismiss
    }
 }

+/** Security keys need WebAuthn, which the sign-in here does not speak. */
+private const val SECURITY_KEY_NOTE =
+    "Security keys are not supported. If your account has only a security key, add an " +
+        "authenticator app in your Proton account settings to sign in here."
+
 /** Installed once per page, at start and again at finish in case the first ran too early. */
 private const val VERIFICATION_BRIDGE = """
 if (!window.__pstrVerification) {
@@ -136,15 +136,15 @@ internal fun SharesScreen(
        )
    }
    removing?.let { share ->
-        // Asked, because it cannot be undone: the link's secret, its offline
-        // files and its watch positions all go (`Catalog::remove_share`).
+        // Asked, because it cannot be undone: the link's secret and its
+        // offline files go. Watch positions stay (`Catalog::remove_share`).
        AlertDialog(
            onDismissRequest = { removing = null },
            title = { Text("Remove ${share.name}?") },
            text = {
                Text(
-                    "Its titles leave the library, and its offline episodes and watch " +
-                        "progress are deleted. Adding the link again starts it fresh.",
+                    "Its titles leave the library and its offline episodes are deleted. " +
+                        "Watch progress is kept, so adding the link again picks up where you left off.",
                )
            },
            confirmButton = {
@@ -3809,11 +3809,12 @@ mod tests {
        assert!(engine.remove_share(share.id.clone()).is_err());
        assert_eq!(engine.share_generation.load(Ordering::Acquire), 2);
        assert!(engine.shares().expect("shares").is_empty());
+        // Kept, as through a recrawl: sync would bring it back regardless.
        assert!(
            engine
                .watch_state(share.id, "episode".to_owned())
                .expect("watch state")
-                .is_none()
+                .is_some()
        );

        drop(engine);
@@ -33,6 +33,8 @@ serde_json.workspace = true
 directories.workspace = true
 chrono.workspace = true
 souvlaki.workspace = true
+wry.workspace = true
+tao.workspace = true

 [build-dependencies]
 embed-resource.workspace = true
@@ -2118,6 +2118,9 @@ impl eframe::App for App {
        self.playback = None;
        self.engine
            .shutdown_downloads(std::time::Duration::from_secs(3));
+        // After the player: its last position is saved on the way out.
+        self.engine
+            .sync_before_exit(std::time::Duration::from_secs(3));
    }
 }

@@ -35,6 +35,7 @@ use pstr_core::library::{Library, Title, TitleKind};
 use pstr_core::metadata::{EpisodeGuide, MetadataConfig, MetadataRecord, ProviderId};
 use pstr_core::prefs::PlaybackPrefs;
 use pstr_core::proton_drive_rs::ThumbnailType;
+use pstr_core::proton_sdk::api::HumanVerificationCredential;
 use pstr_core::proton_sdk::ids::{LinkId, NodeUid, VolumeId};
 use pstr_core::shares::AccountFolder;
 use pstr_core::sync::{SyncReport, WatchSync};
@@ -704,17 +705,38 @@ impl Engine {
    pub fn sign_in(&self, username: String, password: String) {
        let engine = self.clone();
        self.runtime.spawn(async move {
-            match engine.accounts.sign_in(&username, &password, None).await {
-                Ok(step) => engine.sign_in_step(step),
-                Err(pstr_core::Error::HumanVerification(_)) => {
-                    engine.emit(Event::SignInFailed(
-                        "Proton wants a CAPTCHA before it accepts this sign-in, and this app \
-                         cannot show one. Try again later, or sign in once from the Android app."
+            let mut verification = None;
+            // Twice at most: once as asked, and once more with a solved
+            // CAPTCHA if Proton wanted one. A second gate after that is
+            // Proton refusing the answer, not a puzzle worth repeating.
+            for _ in 0..2 {
+                match engine
+                    .accounts
+                    .sign_in(&username, &password, verification.take())
+                    .await
+                {
+                    Ok(step) => return engine.sign_in_step(step),
+                    Err(pstr_core::Error::HumanVerification(challenge)) => {
+                        let url = challenge.verification_url();
+                        let token = tokio::task::spawn_blocking(move || crate::verify::solve(&url))
+                            .await
+                            .ok()
+                            .flatten();
+                        let Some(token) = token else {
+                            return engine.emit(Event::SignInFailed(
+                                "Proton wants you to confirm you are human before it accepts \
+                                 this sign-in. Sign in again to solve the puzzle."
                                    .to_owned(),
                            ));
+                        };
+                        verification = Some(HumanVerificationCredential::captcha(token));
                    }
-                Err(error) => engine.emit(Event::SignInFailed(error.to_string())),
+                    Err(error) => return engine.emit(Event::SignInFailed(error.to_string())),
                }
+            }
+            engine.emit(Event::SignInFailed(
+                "Proton did not accept the verification. Try again in a while.".to_owned(),
+            ));
        });
    }

@@ -841,6 +863,27 @@ impl Engine {
        });
    }

+    /// Sync once more before the app exits, waiting at most `timeout`.
+    ///
+    /// Where the viewer stopped is what another device wants next, and the
+    /// timer would not get to it. Bounded, because quitting must not hang on
+    /// a slow network; a sync cut short loses nothing, the next launch sends
+    /// the same table.
+    pub fn sync_before_exit(&self, timeout: std::time::Duration) {
+        let (Some(account), Some(sync)) = (self.account.lock().clone(), self.watch_sync.clone())
+        else {
+            return;
+        };
+        let catalog = Arc::clone(&self.catalog);
+        self.runtime.block_on(async move {
+            match tokio::time::timeout(timeout, sync.sync(&account, &catalog)).await {
+                Ok(Ok(_)) => {}
+                Ok(Err(error)) => tracing::warn!("sync watch history on exit: {error}"),
+                Err(_) => tracing::warn!("sync watch history on exit: timed out"),
+            }
+        });
+    }
+
    fn sync_periodically(&self) {
        let engine = self.clone();
        self.runtime.spawn(async move {
@@ -30,5 +30,6 @@ pub mod pacing;
 pub mod playback;
 pub mod theme;
 pub mod ui;
+pub mod verify;
 pub mod video;
 pub mod window;
@@ -16,6 +16,12 @@ use anyhow::Context;
 use pstr_core::config::AppDirs;

 fn main() -> anyhow::Result<()> {
+    // Before anything else: a verification window is a child process of the
+    // app, and must not claim the single instance or open a library.
+    if let Some(code) = pstr_app::verify::run_if_requested() {
+        std::process::exit(code);
+    }
+
    tracing_subscriber::fmt()
        .with_env_filter(
            tracing_subscriber::EnvFilter::try_from_default_env()
@@ -207,6 +207,12 @@ fn code_form(ui: &mut egui::Ui, panel: &mut AccountPanel, actions: &mut Vec<Acti
            .desired_width(160.0),
    );
    field.request_focus();
+    ui.add_space(theme::space::S);
+    // Security keys need WebAuthn, which the sign-in here does not speak.
+    ui.label(ui::muted(
+        "Security keys are not supported. If your account has only a security key, add an \
+         authenticator app in your Proton account settings to sign in here.",
+    ));
    ui.add_space(theme::space::L);
    error_line(ui, panel);
    let ready = !panel.code.trim().is_empty() && !panel.busy;
@@ -0,0 +1,190 @@
+//! Proton's CAPTCHA, in a window of its own.
+//!
+//! Proton puts a CAPTCHA in front of a sign-in it does not recognise — a new
+//! network, a VPN exit. The page reports success by posting a message to its
+//! host rather than by redirecting, so the system browser has nowhere to send
+//! it back to: it needs a webview this app controls, as on Android and in
+//! `proton-drive-linux`.
+//!
+//! The webview runs in a child process — this same executable, started with
+//! [`ARG`] — because its windowing library and eframe's cannot both own the
+//! event loop of one process. The child prints the solved token on stdout and
+//! exits; closing its window exits with nothing printed, which is a cancel.
+
+use std::io::{Read as _, Write as _};
+
+/// The argument that starts this executable as the verification window,
+/// followed by the page's URL.
+pub const ARG: &str = "--human-verification";
+
+/// Forwards every message the page posts to this process. The page targets
+/// `window.parent`, which for a top-level page is the page itself, so a
+/// listener on its own window hears it.
+const BRIDGE: &str = r#"
+window.addEventListener('message', function (event) {
+    try {
+        window.ipc.postMessage(typeof event.data === 'string' ? event.data : JSON.stringify(event.data));
+    } catch (e) {}
+});
+"#;
+
+/// Run the verification window if this process was started for it, returning
+/// the process's exit code; `None` when it was started as the app.
+pub fn run_if_requested() -> Option<i32> {
+    let mut args = std::env::args().skip(1);
+    if args.next().as_deref() != Some(ARG) {
+        return None;
+    }
+    let Some(url) = args.next().filter(|url| is_proton_page(url)) else {
+        eprintln!("{ARG} needs a verification page on proton.me");
+        return Some(2);
+    };
+    Some(match window(&url) {
+        Ok(()) => 0,
+        Err(error) => {
+            eprintln!("the verification window failed: {error}");
+            1
+        }
+    })
+}
+
+/// Present `url` in the verification window and wait for the token it yields.
+///
+/// `None` when the viewer closed the window, or it could not be shown.
+/// Blocking: call it off the UI thread and outside the async runtime.
+pub fn solve(url: &str) -> Option<String> {
+    let exe = std::env::current_exe()
+        .inspect_err(|error| tracing::warn!("locate this executable: {error}"))
+        .ok()?;
+    let mut child = std::process::Command::new(exe)
+        .arg(ARG)
+        .arg(url)
+        .stdin(std::process::Stdio::null())
+        .stdout(std::process::Stdio::piped())
+        .spawn()
+        .inspect_err(|error| tracing::warn!("open the verification window: {error}"))
+        .ok()?;
+    let mut out = String::new();
+    if let Some(mut stdout) = child.stdout.take() {
+        let _ = stdout.read_to_string(&mut out);
+    }
+    let status = child.wait().ok()?;
+    if !status.success() {
+        tracing::warn!("the verification window exited with {status}");
+        return None;
+    }
+    out.lines()
+        .map(str::trim)
+        .rfind(|line| !line.is_empty())
+        .map(str::to_owned)
+}
+
+fn window(url: &str) -> anyhow::Result<()> {
+    use tao::event::{Event, WindowEvent};
+    use tao::event_loop::{ControlFlow, EventLoopBuilder};
+    use tao::window::WindowBuilder;
+    use wry::{NewWindowResponse, WebViewBuilder};
+
+    let event_loop = EventLoopBuilder::<String>::with_user_event().build();
+    let window = WindowBuilder::new()
+        .with_title("Confirm you are human — Proton Stream")
+        .with_inner_size(tao::dpi::LogicalSize::new(440.0, 680.0))
+        .build(&event_loop)?;
+
+    let proxy = event_loop.create_proxy();
+    let builder = WebViewBuilder::new()
+        .with_url(url)
+        .with_initialization_script(BRIDGE)
+        .with_ipc_handler(move |request| {
+            // Every message the page posts lands here, most of them its own
+            // chatter; only a completion carries a token.
+            if let Some(token) = pstr_core::account::verification_token(request.body()) {
+                let _ = proxy.send_event(token);
+            }
+        })
+        // The bridge above is reachable by whatever the page shows, so the
+        // page stays on Proton.
+        .with_navigation_handler(|url| is_allowed_navigation(&url))
+        .with_new_window_req_handler(|_, _| NewWindowResponse::Deny);
+
+    #[cfg(not(any(target_os = "windows", target_os = "macos")))]
+    let _webview = {
+        use tao::platform::unix::WindowExtUnix as _;
+        use wry::WebViewBuilderExtUnix as _;
+        let vbox = window
+            .default_vbox()
+            .ok_or_else(|| anyhow::anyhow!("the window has no GTK container"))?;
+        builder.build_gtk(vbox)?
+    };
+    #[cfg(any(target_os = "windows", target_os = "macos"))]
+    let _webview = builder.build(&window)?;
+
+    let mut answered = false;
+    event_loop.run(move |event, _, control_flow| {
+        *control_flow = ControlFlow::Wait;
+        match event {
+            Event::UserEvent(token) if !answered => {
+                answered = true;
+                let mut stdout = std::io::stdout().lock();
+                let _ = writeln!(stdout, "{token}");
+                let _ = stdout.flush();
+                *control_flow = ControlFlow::Exit;
+            }
+            Event::WindowEvent {
+                event: WindowEvent::CloseRequested,
+                ..
+            } => *control_flow = ControlFlow::Exit,
+            _ => {}
+        }
+    })
+}
+
+/// Whether `url` is a page of Proton's own, over HTTPS.
+fn is_proton_page(url: &str) -> bool {
+    let Some(rest) = url.strip_prefix("https://") else {
+        return false;
+    };
+    let authority = rest.split(['/', '?', '#']).next().unwrap_or_default();
+    // A user-info part would let `proton.me@evil.example` pass.
+    if authority.contains('@') {
+        return false;
+    }
+    let host = authority.split(':').next().unwrap_or_default();
+    host == "proton.me" || host.ends_with(".proton.me")
+}
+
+/// Whether the webview may go to `url`: Proton's pages, and the documents a
+/// page makes for itself, which have no origin of their own to leave to.
+fn is_allowed_navigation(url: &str) -> bool {
+    is_proton_page(url) || url == "about:blank" || url.starts_with("about:srcdoc")
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn only_proton_pages_over_https_are_proton_pages() {
+        assert!(is_proton_page(
+            "https://verify.proton.me/?embed=1&methods=captcha&token=x"
+        ));
+        assert!(is_proton_page("https://proton.me"));
+        assert!(!is_proton_page("http://verify.proton.me/"));
+        assert!(!is_proton_page("https://proton.me.evil.example/"));
+        assert!(!is_proton_page("https://evilproton.me/"));
+        assert!(!is_proton_page("https://proton.me@evil.example/"));
+        assert!(!is_proton_page(
+            "https://evil.example/?next=https://proton.me"
+        ));
+    }
+
+    #[test]
+    fn the_window_stays_on_proton() {
+        assert!(is_allowed_navigation(
+            "https://verify-api.proton.me/core/v4/captcha"
+        ));
+        assert!(is_allowed_navigation("about:blank"));
+        assert!(!is_allowed_navigation("https://example.com/"));
+        assert!(!is_allowed_navigation("file:///etc/passwd"));
+    }
+}
@@ -1084,7 +1084,6 @@ async fn play(
    Ok(())
 }

-/// Unix seconds, for the "when was this asked" columns.
 /// Walk an interactive sign-in through whatever the account asks for.
 async fn login(accounts: &AccountStore, username: &str) -> Result<()> {
    let password = read_password("Password: ")?;
@@ -1092,10 +1091,12 @@ async fn login(accounts: &AccountStore, username: &str) -> Result<()> {
        Ok(step) => step,
        Err(pstr_core::Error::HumanVerification(challenge)) => {
            // Solving a CAPTCHA needs a browser engine that can hand the
-            // token back, which a terminal does not have.
+            // token back, which a terminal does not have. The desktop app has
+            // one, and keeps its session in the same keyring entry.
            anyhow::bail!(
                "Proton wants a CAPTCHA before it accepts this sign-in. Sign in once in the \
-                 desktop or Android app, or try again later. ({})",
+                 desktop app on this computer, which shows it and shares its session with \
+                 pstr, or try again later. ({})",
                challenge.verification_url()
            );
        }
@@ -1108,7 +1109,8 @@ async fn login(accounts: &AccountStore, username: &str) -> Result<()> {
                return Ok(());
            }
            SignIn::SecondFactor(pending) => {
-                let code = read_password("Two-factor code: ")?;
+                // Security keys need WebAuthn, which this sign-in does not speak.
+                let code = read_password("Code from your authenticator app: ")?;
                pending
                    .second_factor(&code)
                    .await
@@ -513,19 +513,17 @@ impl Catalog {
        Ok(rows.collect::<std::result::Result<_, _>>()?)
    }

-    /// Drop everything a share contributed, watch positions included.
+    /// Drop everything a share contributed except where it was watched.
    ///
-    /// Unlike a recrawl — which replaces rows and deliberately leaves watch
-    /// state alone — this is the viewer saying they are done with the share.
-    /// Keeping positions for files they can no longer reach would only leave
-    /// the "continue watching" row pointing at nothing.
+    /// Watch state stays, as through a recrawl. It is history, and not only
+    /// this device's: with an account signed in, the next sync would bring it
+    /// straight back from the other devices' files, so deleting it here would
+    /// only make it flicker. Nothing shows it — the library pairs positions
+    /// with files, and the files are gone — until the share is added again,
+    /// when it picks up where it left off.
    pub fn remove_share(&mut self, share_id: &str) -> Result<()> {
        let tx = self.conn.transaction()?;
        tx.execute("DELETE FROM nodes WHERE share_id = ?1", params![share_id])?;
-        tx.execute(
-            "DELETE FROM watch_state WHERE share_id = ?1",
-            params![share_id],
-        )?;
        tx.execute(
            "DELETE FROM offline_files WHERE share_id = ?1",
            params![share_id],
@@ -2430,6 +2428,38 @@ mod tests {
        assert_eq!(rows[0].link_id, "film");
    }

+    #[test]
+    fn removing_a_share_keeps_its_watch_state_out_of_sight() {
+        let mut catalog = Catalog::in_memory().expect("open");
+        catalog
+            .replace_share("s1", &[file("s1", "a", "Show S01E01.mkv")])
+            .expect("crawl");
+        let state = WatchState {
+            position_secs: 120.0,
+            duration_secs: Some(1440.0),
+            watched: false,
+            updated_at: 10,
+        };
+        catalog.set_watch_state("s1", "a", &state).expect("set");
+
+        catalog.remove_share("s1").expect("remove");
+        let library = crate::library::Library::build(
+            catalog.all_files().expect("files"),
+            &catalog.all_watch_states().expect("watch"),
+        );
+        assert!(library.titles.is_empty());
+        assert_eq!(catalog.watch_state("s1", "a").expect("read"), Some(state));
+
+        catalog
+            .replace_share("s1", &[file("s1", "a", "Show S01E01.mkv")])
+            .expect("re-add");
+        let library = crate::library::Library::build(
+            catalog.all_files().expect("files"),
+            &catalog.all_watch_states().expect("watch"),
+        );
+        assert_eq!(library.titles[0].seasons[0].episodes[0].watch, Some(state));
+    }
+
    #[test]
    fn merging_takes_only_states_newer_than_the_recorded_ones() {
        let mut catalog = Catalog::in_memory().expect("open");
@@ -55,19 +55,26 @@ pub trait SecretStore: Send + Sync {
 }

 /// The desktop OS credential store.
+///
+/// A value too long for one entry is split across several; see
+/// [`ENTRY_UNITS`].
 #[cfg(not(target_os = "android"))]
 #[derive(Debug, Default)]
 pub struct KeyringSecretStore;

+/// One credential-store entry per key, with no splitting.
 #[cfg(not(target_os = "android"))]
-impl KeyringSecretStore {
+struct KeyringEntries;
+
+#[cfg(not(target_os = "android"))]
+impl KeyringEntries {
    fn entry(key: &str) -> Result<keyring::Entry> {
        Ok(keyring::Entry::new(KEYRING_SERVICE, key)?)
    }
 }

 #[cfg(not(target_os = "android"))]
-impl SecretStore for KeyringSecretStore {
+impl SecretStore for KeyringEntries {
    fn set(&self, key: &str, value: &str) -> Result<()> {
        Self::entry(key)?.set_password(value)?;
        Ok(())
@@ -89,6 +96,205 @@ impl SecretStore for KeyringSecretStore {
    }
 }

+#[cfg(not(target_os = "android"))]
+impl SecretStore for KeyringSecretStore {
+    fn set(&self, key: &str, value: &str) -> Result<()> {
+        chunked::set(&KeyringEntries, key, value)
+    }
+
+    fn get(&self, key: &str) -> Result<Option<String>> {
+        chunked::get(&KeyringEntries, key)
+    }
+
+    fn delete(&self, key: &str) -> Result<()> {
+        chunked::delete(&KeyringEntries, key)
+    }
+}
+
+/// The most UTF-16 code units one credential-store entry is given.
+///
+/// Windows caps a credential's blob at 2560 bytes, and `keyring` stores it as
+/// UTF-16: 1280 units. A share secret is far below that, but the account
+/// session — tokens, scopes, the mailbox password and a salt per key — can
+/// pass it, and failing to store a refreshed token signs the viewer out at
+/// the next launch. The margin is for the header.
+#[cfg(any(not(target_os = "android"), test))]
+const ENTRY_UNITS: usize = 1200;
+
+/// Splitting a long secret across several entries of an underlying store.
+///
+/// A short value is one entry, exactly as before splitting existed, so every
+/// secret already stored still reads. A long one is written as `key#0`,
+/// `key#1`, … with `key` itself holding [`HEADER`] and the count. The parts go
+/// first and the header last, so a reader never finds a header naming parts
+/// that are not there yet.
+#[cfg(any(not(target_os = "android"), test))]
+mod chunked {
+    use super::{ENTRY_UNITS, SecretStore};
+    use crate::error::Result;
+
+    /// Marks a split value. A short value that happens to start with it is
+    /// split too, so it cannot be mistaken for a header.
+    const HEADER: &str = "pstr-chunked:";
+
+    fn part(key: &str, index: usize) -> String {
+        format!("{key}#{index}")
+    }
+
+    fn parts_of(header: &str) -> Option<usize> {
+        header.strip_prefix(HEADER)?.parse().ok()
+    }
+
+    /// `value` cut into pieces of at most [`ENTRY_UNITS`] UTF-16 units, never
+    /// inside a character.
+    fn split(value: &str) -> Vec<&str> {
+        let mut pieces = Vec::new();
+        let mut start = 0;
+        let mut units = 0;
+        for (at, ch) in value.char_indices() {
+            if units + ch.len_utf16() > ENTRY_UNITS {
+                pieces.push(&value[start..at]);
+                start = at;
+                units = 0;
+            }
+            units += ch.len_utf16();
+        }
+        pieces.push(&value[start..]);
+        pieces
+    }
+
+    pub(super) fn set(store: &dyn SecretStore, key: &str, value: &str) -> Result<()> {
+        let before = store.get(key)?.as_deref().and_then(parts_of).unwrap_or(0);
+        let fits = value.encode_utf16().count() <= ENTRY_UNITS && !value.starts_with(HEADER);
+        let written = if fits {
+            store.set(key, value)?;
+            0
+        } else {
+            let pieces = split(value);
+            for (index, piece) in pieces.iter().enumerate() {
+                store.set(&part(key, index), piece)?;
+            }
+            store.set(key, &format!("{HEADER}{}", pieces.len()))?;
+            pieces.len()
+        };
+        for index in written..before {
+            store.delete(&part(key, index))?;
+        }
+        Ok(())
+    }
+
+    pub(super) fn get(store: &dyn SecretStore, key: &str) -> Result<Option<String>> {
+        let Some(value) = store.get(key)? else {
+            return Ok(None);
+        };
+        let Some(count) = parts_of(&value) else {
+            return Ok(Some(value));
+        };
+        let mut joined = String::new();
+        for index in 0..count {
+            // A part gone missing is a value that no longer exists whole;
+            // half of a token is worse than none.
+            let Some(piece) = store.get(&part(key, index))? else {
+                return Ok(None);
+            };
+            joined.push_str(&piece);
+        }
+        Ok(Some(joined))
+    }
+
+    pub(super) fn delete(store: &dyn SecretStore, key: &str) -> Result<()> {
+        let count = store.get(key)?.as_deref().and_then(parts_of).unwrap_or(0);
+        store.delete(key)?;
+        for index in 0..count {
+            store.delete(&part(key, index))?;
+        }
+        Ok(())
+    }
+
+    #[cfg(test)]
+    mod tests {
+        use std::collections::BTreeMap;
+
+        use parking_lot::Mutex;
+
+        use super::*;
+
+        /// An underlying store that refuses what Windows would.
+        #[derive(Default)]
+        struct Limited(Mutex<BTreeMap<String, String>>);
+
+        impl SecretStore for Limited {
+            fn set(&self, key: &str, value: &str) -> Result<()> {
+                assert!(
+                    value.encode_utf16().count() <= 1280,
+                    "{key} is too long for one entry"
+                );
+                self.0.lock().insert(key.to_owned(), value.to_owned());
+                Ok(())
+            }
+            fn get(&self, key: &str) -> Result<Option<String>> {
+                Ok(self.0.lock().get(key).cloned())
+            }
+            fn delete(&self, key: &str) -> Result<()> {
+                self.0.lock().remove(key);
+                Ok(())
+            }
+        }
+
+        #[test]
+        fn a_short_secret_is_one_entry_as_it_always_was() {
+            let store = Limited::default();
+            set(&store, "share-a", "fragment").unwrap();
+            assert_eq!(store.0.lock().len(), 1);
+            assert_eq!(get(&store, "share-a").unwrap().as_deref(), Some("fragment"));
+        }
+
+        #[test]
+        fn a_secret_longer_than_an_entry_round_trips() {
+            let store = Limited::default();
+            let long: String = "aé😀".repeat(1500);
+            set(&store, "proton-account", &long).unwrap();
+            assert!(store.0.lock().len() > 2);
+            assert_eq!(get(&store, "proton-account").unwrap(), Some(long));
+        }
+
+        #[test]
+        fn a_shorter_value_leaves_no_parts_of_the_longer_one_behind() {
+            let store = Limited::default();
+            set(&store, "k", &"x".repeat(5000)).unwrap();
+            set(&store, "k", &"y".repeat(1300)).unwrap();
+            assert_eq!(store.0.lock().len(), 3);
+            set(&store, "k", "short").unwrap();
+            assert_eq!(store.0.lock().len(), 1);
+            assert_eq!(get(&store, "k").unwrap().as_deref(), Some("short"));
+        }
+
+        #[test]
+        fn a_value_that_looks_like_a_header_is_not_taken_for_one() {
+            let store = Limited::default();
+            set(&store, "k", "pstr-chunked:3").unwrap();
+            assert_eq!(get(&store, "k").unwrap().as_deref(), Some("pstr-chunked:3"));
+        }
+
+        #[test]
+        fn deleting_a_split_secret_deletes_every_part() {
+            let store = Limited::default();
+            set(&store, "k", &"x".repeat(5000)).unwrap();
+            delete(&store, "k").unwrap();
+            assert!(store.0.lock().is_empty());
+            assert_eq!(get(&store, "k").unwrap(), None);
+        }
+
+        #[test]
+        fn a_split_secret_missing_a_part_reads_as_absent() {
+            let store = Limited::default();
+            set(&store, "k", &"x".repeat(5000)).unwrap();
+            store.delete("k#1").unwrap();
+            assert_eq!(get(&store, "k").unwrap(), None);
+        }
+    }
+}
+
 /// What the app records about a share, minus its secrets.
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 pub struct Share {
@@ -32,7 +32,7 @@
 use std::collections::HashMap;

 use parking_lot::Mutex;
-use proton_drive_rs::{DeviceType, NodeKind};
+use proton_drive_rs::{DeviceType, NodeKind, ProtonDriveClient};
 use proton_sdk::ids::NodeUid;
 use serde::{Deserialize, Serialize};

@@ -120,12 +120,133 @@ pub struct SyncReport {
    pub uploaded: bool,
    /// Other installations whose history was read.
    pub devices: usize,
+    /// Files of installations gone quiet that were moved to the trash, their
+    /// history now carried in this installation's own file.
+    pub retired: usize,
 }

-/// A history file as last read, by the revision it was read at.
+/// How long an installation's file may go unwritten before another
+/// installation retires it.
+///
+/// Reinstalling — routine on Android, where uninstalling wipes the config —
+/// starts a new id, and every file ever written would otherwise be read by
+/// every device forever. Retiring is safe at any age: a file is only trashed
+/// after its entries were merged and this installation's file, which then
+/// holds them too, is written. An installation that was merely idle finds its
+/// file gone on its next sync and writes it again.
+const RETIRE_AFTER_SECS: i64 = 90 * 24 * 60 * 60;
+
+/// One history file in Drive, as listed.
+#[derive(Debug, Clone)]
+pub(crate) struct RemoteFile {
+    pub uid: NodeUid,
+    pub name: String,
+    /// The active revision, which moves with every write.
+    pub revision: Option<String>,
+    /// Last modification, epoch seconds.
+    pub modified: i64,
+}
+
+/// The few Drive operations sync needs: the account's Drive in the app, an
+/// in-memory one in the tests.
+pub(crate) trait HistoryDrive: Sync {
+    /// The history folders, creating the device and folder the first time.
+    /// See [`WatchSync::folders`].
+    fn history_folders(&self) -> impl Future<Output = Result<Vec<NodeUid>>> + Send;
+    /// The untrashed `.json` files directly in `folder`.
+    fn list(&self, folder: &NodeUid) -> impl Future<Output = Result<Vec<RemoteFile>>> + Send;
+    fn download(&self, uid: &NodeUid) -> impl Future<Output = Result<Vec<u8>>> + Send;
+    fn create(
+        &self,
+        folder: &NodeUid,
+        name: &str,
+        bytes: &[u8],
+    ) -> impl Future<Output = Result<()>> + Send;
+    fn replace(&self, uid: &NodeUid, bytes: &[u8]) -> impl Future<Output = Result<()>> + Send;
+    fn trash(&self, uids: &[NodeUid]) -> impl Future<Output = Result<()>> + Send;
+}
+
+impl HistoryDrive for ProtonDriveClient {
+    /// Two installations signing in at the same moment can each create the
+    /// device before seeing the other's. Every device of that name is read
+    /// from so neither's history is lost; the oldest is the one written to,
+    /// which is the same one on every installation.
+    async fn history_folders(&self) -> Result<Vec<NodeUid>> {
+        let mut devices: Vec<_> = self
+            .enumerate_devices()
+            .await?
+            .into_iter()
+            .filter(|device| device.name.as_deref().ok() == Some(DEVICE_NAME))
+            .collect();
+        devices.sort_by_key(|device| device.creation_time);
+        if devices.is_empty() {
+            devices.push(self.create_device(DEVICE_NAME, device_type()).await?);
+        }
+        let mut folders = Vec::with_capacity(devices.len());
+        for device in &devices {
+            folders.push(
+                self.create_folder_path(&device.root_folder_uid, FOLDER)
+                    .await?,
+            );
+        }
+        Ok(folders)
+    }
+
+    async fn list(&self, folder: &NodeUid) -> Result<Vec<RemoteFile>> {
+        let uids = self.enumerate_folder_children_node_uids(folder).await?;
+        if uids.is_empty() {
+            return Ok(Vec::new());
+        }
+        Ok(self
+            .enumerate_nodes(&uids)
+            .await?
+            .into_iter()
+            .filter_map(|node| {
+                let NodeKind::File {
+                    active_revision_id, ..
+                } = node.kind
+                else {
+                    return None;
+                };
+                (!node.trashed && node.name.ends_with(".json")).then_some(RemoteFile {
+                    uid: node.uid,
+                    name: node.name,
+                    revision: active_revision_id,
+                    modified: node.modification_time,
+                })
+            })
+            .collect())
+    }
+
+    async fn download(&self, uid: &NodeUid) -> Result<Vec<u8>> {
+        Ok(self.download_file(uid).await?)
+    }
+
+    async fn create(&self, folder: &NodeUid, name: &str, bytes: &[u8]) -> Result<()> {
+        self.upload_file(folder, name, "application/json", bytes)
+            .await?;
+        Ok(())
+    }
+
+    async fn replace(&self, uid: &NodeUid, bytes: &[u8]) -> Result<()> {
+        Ok(self.upload_new_revision(uid, bytes).await?)
+    }
+
+    async fn trash(&self, uids: &[NodeUid]) -> Result<()> {
+        for (uid, outcome) in self.trash_nodes(uids).await? {
+            if let Err(error) = outcome {
+                tracing::warn!(%uid, %error, "a retired watch-history file was not trashed");
+            }
+        }
+        Ok(())
+    }
+}
+
+/// A history file as last read, by the revision it was read at. `None`
+/// entries for one this build could not read.
 struct Seen {
    revision: Option<String>,
-    entries: Vec<HistoryEntry>,
+    entries: Option<Vec<HistoryEntry>>,
 }

 /// Syncs the catalog's watch table with the account's Drive.
@@ -139,7 +260,7 @@ pub struct WatchSync {
    /// the catalog so an unchanged history is not uploaded as a new revision.
    own: Mutex<Option<Vec<HistoryEntry>>>,
    /// The history folders, resolved once per account. Usually one; see
-    /// [`WatchSync::folders`].
+    /// [`HistoryDrive::history_folders`].
    folders: Mutex<Option<Vec<NodeUid>>>,
    /// One sync at a time: two would race on creating the device and the
    /// installation's file.
@@ -182,60 +303,70 @@ impl WatchSync {
        *self.folders.lock() = None;
    }

-    /// Pull every other installation's history into `catalog`, then write
-    /// this one's if it changed.
+    /// Pull every other installation's history into `catalog`, write this
+    /// one's if it changed, then retire the files of installations gone quiet.
    ///
    /// The catalog is locked only around its own reads and writes, never
    /// across a request, so playback can keep saving its position while this
    /// runs.
    pub async fn sync(&self, account: &Account, catalog: &Mutex<Catalog>) -> Result<SyncReport> {
+        let now = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .map_or(0, |since| since.as_secs() as i64);
+        self.sync_with(account.drive(), catalog, now).await
+    }
+
+    pub(crate) async fn sync_with<D: HistoryDrive>(
+        &self,
+        drive: &D,
+        catalog: &Mutex<Catalog>,
+        now: i64,
+    ) -> Result<SyncReport> {
        let _running = self.running.lock().await;
-        let drive = account.drive();
-        let folders = self.folders(account).await?;
+        let folders = self.folders(drive).await?;
        let own_name = format!("{}.json", self.installation);

        let mut own_file = None;
-        let mut remote = Vec::new();
-        let mut devices = 0;
+        let mut others = Vec::new();
        for folder in &folders {
-            let uids = drive.enumerate_folder_children_node_uids(folder).await?;
-            if uids.is_empty() {
-                continue;
+            for file in drive.list(folder).await? {
+                if file.name == own_name {
+                    own_file.get_or_insert(file);
+                } else {
+                    others.push(file);
                }
-            for node in drive.enumerate_nodes(&uids).await? {
-                let NodeKind::File {
-                    active_revision_id, ..
-                } = &node.kind
-                else {
-                    continue;
-                };
-                if node.trashed || !node.name.ends_with(".json") {
-                    continue;
-                }
-                if node.name == own_name {
-                    if own_file.is_none() {
-                        own_file = Some((node.uid.clone(), active_revision_id.clone()));
-                    }
-                    continue;
-                }
-                devices += 1;
-                remote.extend(
-                    self.read(account, &node.uid, active_revision_id.clone())
-                        .await,
-                );
            }
        }

+        let mut remote = Vec::new();
+        // Files whose every entry has been read, and so can be retired once
+        // this installation's file carries them.
+        let mut readable = Vec::new();
+        for file in &others {
+            if let Some(entries) = self.read(drive, file).await {
+                remote.extend(entries);
+                readable.push(file);
+            }
+        }
+
+        // What this installation wrote before is history too: after a
+        // reinstall that kept the config, or a catalog that was deleted. One
+        // that cannot be read now is left alone rather than overwritten with
+        // less than it holds, and read again next time.
+        let mut own_unreadable = false;
        if self.own.lock().is_none() {
            let entries = match &own_file {
-                Some((uid, revision)) => self.read(account, uid, revision.clone()).await,
-                None => Vec::new(),
+                Some(file) => self.read(drive, file).await,
+                None => Some(Vec::new()),
            };
-            // What this installation wrote before is history too: after a
-            // reinstall that kept the config, or a catalog that was deleted.
+            match entries {
+                Some(entries) => {
                    remote.extend(entries.iter().cloned());
                    *self.own.lock() = Some(entries);
                }
+                None => own_unreadable = true,
+            }
+        }

        let incoming: Vec<(String, String, WatchState)> = remote
            .iter()
@@ -254,8 +385,12 @@ impl WatchSync {
            .collect();
        entries.sort_by(|a, b| (&a.share, &a.link).cmp(&(&b.share, &b.link)));

-        let unchanged = self.own.lock().as_ref() == Some(&entries);
-        let uploaded = if unchanged || (entries.is_empty() && own_file.is_none()) {
+        // A file that is missing is written even when what it would hold has
+        // not changed: another installation retired it, or it was deleted by
+        // hand, and either way the history it carried lives only here now.
+        let unchanged = own_file.is_some() && self.own.lock().as_ref() == Some(&entries);
+        let uploaded = if own_unreadable || unchanged || (entries.is_empty() && own_file.is_none())
+        {
            false
        } else {
            let file = HistoryFile {
@@ -266,94 +401,91 @@ impl WatchSync {
            let bytes = serde_json::to_vec(&file)
                .map_err(|e| Error::Config(format!("serialize watch history: {e}")))?;
            match &own_file {
-                Some((uid, _)) => drive.upload_new_revision(uid, &bytes).await?,
-                None => {
-                    drive
-                        .upload_file(&folders[0], &own_name, "application/json", &bytes)
-                        .await?;
-                }
+                Some(file) => drive.replace(&file.uid, &bytes).await?,
+                None => drive.create(&folders[0], &own_name, &bytes).await?,
            }
            *self.own.lock() = Some(entries);
            true
        };

+        // Only now: every entry of a retired file was merged above, and this
+        // installation's file — just written, or already up to date — holds
+        // the merged table.
+        let retired: Vec<NodeUid> = readable
+            .into_iter()
+            .filter(|file| !own_unreadable && now - file.modified >= RETIRE_AFTER_SECS)
+            .map(|file| file.uid.clone())
+            .collect();
+        if !retired.is_empty() {
+            match drive.trash(&retired).await {
+                Ok(()) => {
+                    let mut seen = self.seen.lock();
+                    for uid in &retired {
+                        seen.remove(uid.link_id.as_str());
+                    }
+                }
+                Err(error) => {
+                    tracing::warn!(%error, "retiring old watch-history files failed");
+                }
+            }
+        }
+
        Ok(SyncReport {
            applied,
            uploaded,
-            devices,
+            devices: others.len(),
+            retired: retired.len(),
        })
    }

    /// The entries of one history file, from the cache when its revision has
-    /// not moved.
+    /// not moved, or `None` when it cannot be read.
    ///
-    /// A file that will not download or parse is logged and read as empty: it
-    /// is another device's, and one bad file must not stop the rest syncing.
-    async fn read(
+    /// A file that will not download or parse is logged and skipped: it is
+    /// another device's, and one bad file must not stop the rest syncing.
+    async fn read<D: HistoryDrive>(
        &self,
-        account: &Account,
-        uid: &NodeUid,
-        revision: Option<String>,
-    ) -> Vec<HistoryEntry> {
-        let key = uid.link_id.as_str().to_owned();
+        drive: &D,
+        file: &RemoteFile,
+    ) -> Option<Vec<HistoryEntry>> {
+        let key = file.uid.link_id.as_str().to_owned();
        if let Some(seen) = self.seen.lock().get(&key)
-            && revision.is_some()
-            && seen.revision == revision
+            && file.revision.is_some()
+            && seen.revision == file.revision
        {
            return seen.entries.clone();
        }
-        let entries = match account.drive().download_file(uid).await {
-            Ok(bytes) => match parse(&bytes) {
-                Some(entries) => entries,
-                None => {
+        let uid = &file.uid;
+        let entries = match drive.download(uid).await {
+            Ok(bytes) => {
+                let entries = parse(&bytes);
+                if entries.is_none() {
                    tracing::warn!(%uid, "skipping a watch-history file this build cannot read");
-                    Vec::new()
                }
-            },
+                entries
+            }
            Err(error) => {
+                // Not cached: a download that failed is tried again next time.
                tracing::warn!(%uid, %error, "a watch-history file could not be downloaded");
-                return Vec::new();
+                return None;
            }
        };
        self.seen.lock().insert(
            key,
            Seen {
-                revision,
+                revision: file.revision.clone(),
                entries: entries.clone(),
            },
        );
        entries
    }

-    /// The history folders, creating the device and folder the first time.
-    ///
-    /// Two installations signing in at the same moment can each create the
-    /// device before seeing the other's. Every device of that name is read
-    /// from so neither's history is lost; the oldest is the one written to,
-    /// which is the same one on every installation.
-    async fn folders(&self, account: &Account) -> Result<Vec<NodeUid>> {
+    /// The history folders, resolved once per account.
+    async fn folders<D: HistoryDrive>(&self, drive: &D) -> Result<Vec<NodeUid>> {
        if let Some(folders) = self.folders.lock().clone() {
            return Ok(folders);
        }
-        let drive = account.drive();
-        let mut devices: Vec<_> = drive
-            .enumerate_devices()
-            .await?
-            .into_iter()
-            .filter(|device| device.name.as_deref().ok() == Some(DEVICE_NAME))
-            .collect();
-        devices.sort_by_key(|device| device.creation_time);
-        if devices.is_empty() {
-            devices.push(drive.create_device(DEVICE_NAME, device_type()).await?);
-        }
-        let mut folders = Vec::with_capacity(devices.len());
-        for device in &devices {
-            folders.push(
-                drive
-                    .create_folder_path(&device.root_folder_uid, FOLDER)
-                    .await?,
-            );
-        }
+        let folders = drive.history_folders().await?;
        *self.folders.lock() = Some(folders.clone());
        Ok(folders)
    }
@@ -398,6 +530,383 @@ mod tests {
        }
    }

+    /// One history folder in memory, standing in for the account's Drive.
+    #[derive(Default)]
+    struct FakeDrive {
+        files: Mutex<Vec<FakeFile>>,
+        /// What the next write is stamped with, epoch seconds.
+        clock: std::sync::atomic::AtomicI64,
+        /// Downloads fail while set, as on a dropped connection.
+        offline: std::sync::atomic::AtomicBool,
+        uploads: std::sync::atomic::AtomicUsize,
+    }
+
+    struct FakeFile {
+        uid: NodeUid,
+        name: String,
+        bytes: Vec<u8>,
+        revision: u32,
+        modified: i64,
+        trashed: bool,
+    }
+
+    fn uid(link: &str) -> NodeUid {
+        NodeUid::new("volume".to_owned().into(), link.to_owned().into())
+    }
+
+    impl FakeDrive {
+        fn at(&self, now: i64) {
+            self.clock.store(now, std::sync::atomic::Ordering::SeqCst);
+        }
+
+        fn names(&self) -> Vec<String> {
+            let mut names: Vec<_> = self
+                .files
+                .lock()
+                .iter()
+                .filter(|file| !file.trashed)
+                .map(|file| file.name.clone())
+                .collect();
+            names.sort();
+            names
+        }
+
+        fn uploads(&self) -> usize {
+            self.uploads.load(std::sync::atomic::Ordering::SeqCst)
+        }
+
+        fn put(&self, name: &str, bytes: Vec<u8>) {
+            let modified = self.clock.load(std::sync::atomic::Ordering::SeqCst);
+            let mut files = self.files.lock();
+            let link = format!("file-{}", files.len());
+            files.push(FakeFile {
+                uid: uid(&link),
+                name: name.to_owned(),
+                bytes,
+                revision: 1,
+                modified,
+                trashed: false,
+            });
+        }
+    }
+
+    impl HistoryDrive for FakeDrive {
+        async fn history_folders(&self) -> Result<Vec<NodeUid>> {
+            Ok(vec![uid("folder")])
+        }
+
+        async fn list(&self, _folder: &NodeUid) -> Result<Vec<RemoteFile>> {
+            Ok(self
+                .files
+                .lock()
+                .iter()
+                .filter(|file| !file.trashed)
+                .map(|file| RemoteFile {
+                    uid: file.uid.clone(),
+                    name: file.name.clone(),
+                    revision: Some(file.revision.to_string()),
+                    modified: file.modified,
+                })
+                .collect())
+        }
+
+        async fn download(&self, uid: &NodeUid) -> Result<Vec<u8>> {
+            if self.offline.load(std::sync::atomic::Ordering::SeqCst) {
+                return Err(Error::NotFound("offline".to_owned()));
+            }
+            self.files
+                .lock()
+                .iter()
+                .find(|file| &file.uid == uid)
+                .map(|file| file.bytes.clone())
+                .ok_or_else(|| Error::NotFound(uid.to_string()))
+        }
+
+        async fn create(&self, _folder: &NodeUid, name: &str, bytes: &[u8]) -> Result<()> {
+            self.uploads
+                .fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+            self.put(name, bytes.to_vec());
+            Ok(())
+        }
+
+        async fn replace(&self, uid: &NodeUid, bytes: &[u8]) -> Result<()> {
+            self.uploads
+                .fetch_add(1, std::sync::atomic::Ordering::SeqCst);
+            let modified = self.clock.load(std::sync::atomic::Ordering::SeqCst);
+            let mut files = self.files.lock();
+            let file = files
+                .iter_mut()
+                .find(|file| &file.uid == uid)
+                .ok_or_else(|| Error::NotFound(uid.to_string()))?;
+            file.bytes = bytes.to_vec();
+            file.revision += 1;
+            file.modified = modified;
+            Ok(())
+        }
+
+        async fn trash(&self, uids: &[NodeUid]) -> Result<()> {
+            for file in self.files.lock().iter_mut() {
+                if uids.contains(&file.uid) {
+                    file.trashed = true;
+                }
+            }
+            Ok(())
+        }
+    }
+
+    /// An installation: its sync and its catalog.
+    fn device(id: &str) -> (WatchSync, Mutex<Catalog>) {
+        (
+            WatchSync::with_installation(id.to_owned()),
+            Mutex::new(Catalog::in_memory().unwrap()),
+        )
+    }
+
+    fn watched_at(position_secs: f64, updated_at: i64) -> WatchState {
+        WatchState {
+            position_secs,
+            duration_secs: Some(1440.0),
+            watched: false,
+            updated_at,
+        }
+    }
+
+    const DAY: i64 = 24 * 60 * 60;
+
+    #[tokio::test]
+    async fn a_position_saved_on_one_device_resumes_on_another() {
+        let drive = FakeDrive::default();
+        let (laptop, laptop_catalog) = device("laptop");
+        let (phone, phone_catalog) = device("phone");
+        laptop_catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(600.0, 100))
+            .unwrap();
+
+        let first = laptop
+            .sync_with(&drive, &laptop_catalog, 100)
+            .await
+            .unwrap();
+        assert!(first.uploaded);
+        let second = phone.sync_with(&drive, &phone_catalog, 110).await.unwrap();
+
+        assert_eq!(second.applied, 1);
+        assert_eq!(second.devices, 1);
+        assert_eq!(
+            phone_catalog.lock().watch_state("share-a", "ep1").unwrap(),
+            Some(watched_at(600.0, 100))
+        );
+        assert_eq!(drive.names(), ["laptop.json", "phone.json"]);
+    }
+
+    #[tokio::test]
+    async fn the_newer_position_wins_whichever_device_syncs_first() {
+        let drive = FakeDrive::default();
+        let (laptop, laptop_catalog) = device("laptop");
+        let (phone, phone_catalog) = device("phone");
+        laptop_catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(300.0, 100))
+            .unwrap();
+        phone_catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(900.0, 200))
+            .unwrap();
+
+        laptop
+            .sync_with(&drive, &laptop_catalog, 300)
+            .await
+            .unwrap();
+        phone.sync_with(&drive, &phone_catalog, 300).await.unwrap();
+        laptop
+            .sync_with(&drive, &laptop_catalog, 300)
+            .await
+            .unwrap();
+
+        for catalog in [&laptop_catalog, &phone_catalog] {
+            assert_eq!(
+                catalog.lock().watch_state("share-a", "ep1").unwrap(),
+                Some(watched_at(900.0, 200))
+            );
+        }
+    }
+
+    #[tokio::test]
+    async fn an_unchanged_history_is_not_uploaded_again() {
+        let drive = FakeDrive::default();
+        let (laptop, catalog) = device("laptop");
+        catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(60.0, 100))
+            .unwrap();
+
+        laptop.sync_with(&drive, &catalog, 100).await.unwrap();
+        let again = laptop.sync_with(&drive, &catalog, 200).await.unwrap();
+
+        assert!(!again.uploaded);
+        assert_eq!(drive.uploads(), 1);
+    }
+
+    #[tokio::test]
+    async fn nothing_is_uploaded_before_anything_was_watched() {
+        let drive = FakeDrive::default();
+        let (laptop, catalog) = device("laptop");
+        let report = laptop.sync_with(&drive, &catalog, 100).await.unwrap();
+        assert!(!report.uploaded);
+        assert!(drive.names().is_empty());
+    }
+
+    #[tokio::test]
+    async fn a_file_that_went_missing_is_written_again() {
+        let drive = FakeDrive::default();
+        let (laptop, catalog) = device("laptop");
+        catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(60.0, 100))
+            .unwrap();
+        laptop.sync_with(&drive, &catalog, 100).await.unwrap();
+
+        let own: Vec<NodeUid> = drive.files.lock().iter().map(|f| f.uid.clone()).collect();
+        drive.trash(&own).await.unwrap();
+        let report = laptop.sync_with(&drive, &catalog, 200).await.unwrap();
+
+        assert!(report.uploaded);
+        assert_eq!(drive.names(), ["laptop.json"]);
+    }
+
+    #[tokio::test]
+    async fn history_this_installation_wrote_before_comes_back_into_an_empty_catalog() {
+        let drive = FakeDrive::default();
+        let (laptop, catalog) = device("laptop");
+        catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(60.0, 100))
+            .unwrap();
+        laptop.sync_with(&drive, &catalog, 100).await.unwrap();
+
+        // The catalog was deleted; the config, and with it the id, was not.
+        let (relaunched, empty) = device("laptop");
+        let report = relaunched.sync_with(&drive, &empty, 200).await.unwrap();
+
+        assert_eq!(report.applied, 1);
+        assert!(!report.uploaded);
+        assert_eq!(
+            empty.lock().watch_state("share-a", "ep1").unwrap(),
+            Some(watched_at(60.0, 100))
+        );
+    }
+
+    #[tokio::test]
+    async fn an_own_file_that_cannot_be_read_is_not_overwritten() {
+        let drive = FakeDrive::default();
+        let (laptop, catalog) = device("laptop");
+        catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(60.0, 100))
+            .unwrap();
+        laptop.sync_with(&drive, &catalog, 100).await.unwrap();
+
+        let (relaunched, other) = device("laptop");
+        other
+            .lock()
+            .set_watch_state("share-a", "ep2", &watched_at(5.0, 150))
+            .unwrap();
+        drive
+            .offline
+            .store(true, std::sync::atomic::Ordering::SeqCst);
+        let report = relaunched.sync_with(&drive, &other, 200).await.unwrap();
+        assert!(!report.uploaded);
+
+        drive
+            .offline
+            .store(false, std::sync::atomic::Ordering::SeqCst);
+        relaunched.sync_with(&drive, &other, 300).await.unwrap();
+        let state = other.lock().all_watch_states().unwrap();
+        assert_eq!(state.len(), 2, "both episodes survive: {state:?}");
+    }
+
+    #[tokio::test]
+    async fn a_file_from_a_newer_build_is_neither_merged_nor_retired() {
+        let drive = FakeDrive::default();
+        let future = HistoryFile {
+            version: FORMAT_VERSION + 1,
+            installation: "future".to_owned(),
+            entries: vec![entry("ep1", 60.0, 100)],
+        };
+        drive.put("future.json", serde_json::to_vec(&future).unwrap());
+        let (laptop, catalog) = device("laptop");
+        catalog
+            .lock()
+            .set_watch_state("share-a", "ep2", &watched_at(5.0, 100))
+            .unwrap();
+
+        let report = laptop
+            .sync_with(&drive, &catalog, RETIRE_AFTER_SECS + DAY)
+            .await
+            .unwrap();
+
+        assert_eq!(report.applied, 0);
+        assert_eq!(report.retired, 0);
+        assert_eq!(drive.names(), ["future.json", "laptop.json"]);
+    }
+
+    #[tokio::test]
+    async fn a_quiet_installations_file_is_retired_once_its_history_is_carried() {
+        let drive = FakeDrive::default();
+        let (old_phone, old_catalog) = device("old-phone");
+        old_catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(600.0, 100))
+            .unwrap();
+        drive.at(100);
+        old_phone
+            .sync_with(&drive, &old_catalog, 100)
+            .await
+            .unwrap();
+
+        let (phone, catalog) = device("phone");
+        let later = 100 + RETIRE_AFTER_SECS;
+        drive.at(later);
+        let report = phone.sync_with(&drive, &catalog, later).await.unwrap();
+
+        assert_eq!(report.retired, 1);
+        assert_eq!(drive.names(), ["phone.json"]);
+        // Nothing was lost: the newcomer's file carries it now.
+        let (fresh, fresh_catalog) = device("fresh");
+        fresh
+            .sync_with(&drive, &fresh_catalog, later)
+            .await
+            .unwrap();
+        assert_eq!(
+            fresh_catalog.lock().watch_state("share-a", "ep1").unwrap(),
+            Some(watched_at(600.0, 100))
+        );
+    }
+
+    #[tokio::test]
+    async fn a_recent_installations_file_is_kept() {
+        let drive = FakeDrive::default();
+        let (laptop, laptop_catalog) = device("laptop");
+        laptop_catalog
+            .lock()
+            .set_watch_state("share-a", "ep1", &watched_at(600.0, 100))
+            .unwrap();
+        drive.at(100);
+        laptop
+            .sync_with(&drive, &laptop_catalog, 100)
+            .await
+            .unwrap();
+
+        let (phone, catalog) = device("phone");
+        let report = phone
+            .sync_with(&drive, &catalog, 100 + RETIRE_AFTER_SECS - DAY)
+            .await
+            .unwrap();
+
+        assert_eq!(report.retired, 0);
+        assert_eq!(drive.names(), ["laptop.json", "phone.json"]);
+    }
+
    #[test]
    fn an_installation_keeps_the_id_it_was_given() {
        let root =
@@ -108,9 +108,18 @@ an edge case.
  session — tokens, the mailbox password that unlocks the key chain, and the
  key salts a refreshed token can no longer fetch — is one blob in the same
  credential store, under `proton-account`. Refresh tokens are single-use, so
-  every refresh is written back. The account writes exactly one thing: the
-  watch-history files on its own `proton-stream` device (`pstr-core::sync`).
-  Folders of the account added as shares are only ever read.
+  every refresh is written back. On the desktop the blob can outgrow one
+  credential entry — Windows caps one at 1280 UTF-16 units — so
+  `KeyringSecretStore` splits a long value across `key#0`, `key#1`, … under a
+  header in `key`. The account writes exactly one kind of thing: the
+  watch-history files on its own `proton-stream` device (`pstr-core::sync`),
+  including trashing the file of an installation quiet for 90 days once its
+  history is merged into this one's. Folders of the account added as shares
+  are only ever read.
+- A CAPTCHA in front of a sign-in is shown in a webview, because the page
+  reports success by posting a message to its host. On the desktop that is a
+  child process of the app (`pstr-app::verify`, wry): WebKitGTK on Linux,
+  WebView2 on Windows. It may only navigate to `https://*.proton.me`.
 - Signature verification is absent on the visitor path by design — an anonymous
  visitor cannot read `core/v4/keys/all` to resolve a signer. Decryption still
  proves the bytes were encrypted to the node key. Nodes come back with nothing
@@ -125,10 +134,10 @@ an edge case.
 | Share list | config dir, `shares.json` | **No** — atomic writes, never overwritten when unparseable |
 | Share secrets | OS credential store | **No** |
 | Catalog | data dir, `catalog.db` | Yes — recrawl |
-| Watch state | same DB, own table | **No** — deliberately survives a recrawl; with an account, mirrored to its Drive |
+| Watch state | same DB, own table | **No** — deliberately survives a recrawl and removing the share; with an account, mirrored to its Drive |
 | Proton session | OS credential store, `proton-account` | No — sign in again |
 | Sync identity | config dir, `sync.json` | A new id if missing — the old history file is still read |
-| Watch history in Drive | device `proton-stream`, `watch-history/<id>.json` | One file per installation; merged per episode, newer wins |
+| Watch history in Drive | device `proton-stream`, `watch-history/<id>.json` | One file per installation; merged per episode, newer wins. A file unwritten for 90 days is retired by the next installation to sync, after merging it; a live installation whose file was retired writes it again |
 | Block cache | cache dir, `blocks/` | Yes — must work correctly after deletion |
 | Poster thumbnails | cache dir, `thumbs/` | Yes — refetched per file, one small decrypt each; stored scaled to 640 px |
 | Provider artwork | cache dir, `posters/` | Yes — refetched by URL; stored scaled to 640 px |
@@ -23,7 +23,7 @@ license=('MIT')
 # mpv carries libmpv.so plus its headers on Arch, so it is both the runtime and
 # the build dependency. libsecret is the Secret Service side of the keyring —
 # the share fragment and custom password never touch shares.json.
-depends=('mpv' 'libsecret' 'hicolor-icon-theme')
+depends=('mpv' 'libsecret' 'webkit2gtk-4.1' 'hicolor-icon-theme')
 makedepends=('cargo')
 optdepends=('gnome-keyring: credential storage via Secret Service'
            'kwallet: credential storage via Secret Service on KDE')
@@ -40,6 +40,7 @@ are not Arch.
 |---|---|
 | **libmpv ≥ 0.34** | The player. `pstr-player` links it directly and drives it through `stream_cb`; nothing here shells out to `mpv(1)`, so packages depend on the library, not the player binary. |
 | **libsecret / Secret Service** | The share URL fragment and the custom password are secrets and live in the OS credential store, never in `shares.json`. |
+| **WebKitGTK 4.1** | The window Proton's CAPTCHA is shown in when it gates a sign-in (`pstr-app::verify`). The page reports success by posting a message to its host, so the system browser cannot stand in for it. |
 | **libGL, libxkbcommon, libX11, libwayland-client** | eframe on glow, with both display backends compiled in. |

 Not dependencies, deliberately: **SQLite** (rusqlite is `bundled`) and
@@ -47,11 +48,13 @@ Not dependencies, deliberately: **SQLite** (rusqlite is `bundled`) and

 Per packager that is:

- Debian — `libmpv2 | libmpv1` (trixie | bookworm), `libsecret-1-0`, `libgl1`,
-  `libxkbcommon0`, `libx11-6`, `libwayland-client0`.
- RPM — `mpv-libs`, `libsecret`, `mesa-libGL`, `libxkbcommon`, `libX11`,
-  `libwayland-client`.
- Arch — `mpv` (which carries both `libmpv.so` and its headers), `libsecret`.
+- Debian — `libmpv2 | libmpv1` (trixie | bookworm), `libsecret-1-0`,
+  `libwebkit2gtk-4.1-0`, `libgl1`, `libxkbcommon0`, `libx11-6`,
+  `libwayland-client0`.
+- RPM — `mpv-libs`, `libsecret`, `webkit2gtk4.1`, `mesa-libGL`, `libxkbcommon`,
+  `libX11`, `libwayland-client`.
+- Arch — `mpv` (which carries both `libmpv.so` and its headers), `libsecret`,
+  `webkit2gtk-4.1`.

 The `.deb` and `.rpm` are built from binaries compiled on the packaging host, so
 they inherit its glibc. A package built on Arch installs on Fedora rawhide but
@@ -88,6 +91,13 @@ There is no static libmpv worth shipping, so **"standalone exe" means the exe
 plus `libmpv-2.dll` beside it** — that pair, plus `pstr.exe` and the README, is
 what the portable `.zip` contains and what the `.msi` installs.

+The cross build adds `WebView2Loader.dll` to that set. The CAPTCHA window runs
+on WebView2, and under `-gnu` `webview2-com-sys` links its loader as a DLL —
+without it beside the exe, the app does not start at all. `build-windows.sh`
+takes it from that crate's build output. An `-msvc` build links the loader
+statically and needs no DLL. The WebView2 *runtime* is part of Windows 10 and
+11 and is not shipped.
+
 The MSI needs the WiX toolset; the script installs it (`dotnet tool install
 --global wix`) and adds the UI extension if they are missing. It installs to
 `Program Files\Proton Stream`, puts a Start Menu shortcut on the GUI, and adds
@@ -31,6 +31,7 @@ ExclusiveArch:  x86_64
 # `bundled`) and TLS is rustls, so neither shows up here.
 Requires:       mpv-libs >= 0.34
 Requires:       libsecret
+Requires:       webkit2gtk4.1
 Requires:       mesa-libGL
 Requires:       libxkbcommon
 Requires:       libX11
@@ -149,6 +149,13 @@
            <File Id="MpvDll" Source="$(var.MpvDll)" Name="libmpv-2.dll" KeyPath="yes" />
          </Component>

+          <!-- Loads WebView2 for the CAPTCHA window Proton sometimes puts
+               in front of a sign-in. A -gnu build links it as a DLL; the
+               WebView2 runtime itself comes with Windows. -->
+          <Component Id="WebViewLoader" Guid="3e8a89cf-cf3e-4cc7-b1c6-9d272b3210c3" Win64="yes">
+            <File Id="WebViewLoader" Source="$(var.WebViewLoader)" Name="WebView2Loader.dll" KeyPath="yes" />
+          </Component>
+
          <Component Id="ReadMe" Guid="5bb65b44-f5df-423b-8dcc-a753d7aef565" Win64="yes">
            <File Id="ReadMe" Source="$(var.ReadMe)" Name="README.md" KeyPath="yes" />
          </Component>
@@ -162,6 +169,7 @@
      <ComponentRef Id="AppExe" />
      <ComponentRef Id="CliExe" />
      <ComponentRef Id="MpvDll" />
+      <ComponentRef Id="WebViewLoader" />
      <ComponentRef Id="ReadMe" />
    </Feature>

@@ -232,9 +232,16 @@ stage() {
    [[ -f "$rel/$f" ]] || die "$f missing from $rel — drop --skip-build"
  done

+  # The CAPTCHA window's WebView2 loader. Under -msvc it links statically;
+  # under -gnu, webview2-com-sys links the DLL, which it ships and copies into
+  # its build output, so the exe does not start without it beside it.
+  local loader
+  loader="$(ls -t "$rel"/build/webview2-com-sys-*/out/x64/WebView2Loader.dll 2>/dev/null | head -n1)"
+  [[ -n "$loader" ]] || die "WebView2Loader.dll missing from $rel/build — drop --skip-build"
+
  rm -rf "$OUTDIR"
  mkdir -p "$OUTDIR"
-  install -m755 "$rel/$GUI_BIN" "$rel/$CLI_BIN" "$MPV_DLL" "$OUTDIR/"
+  install -m755 "$rel/$GUI_BIN" "$rel/$CLI_BIN" "$MPV_DLL" "$loader" "$OUTDIR/"
  install -m644 "$ROOT/README.md" "$OUTDIR/"

  if [[ -n "$SIGN_CERT" ]]; then
@@ -295,6 +302,7 @@ make_msi() {
    -D "Version=$VERSION" \
    -D "BinDir=$OUTDIR" \
    -D "MpvDll=$OUTDIR/libmpv-2.dll" \
+    -D "WebViewLoader=$OUTDIR/WebView2Loader.dll" \
    -D "IconFile=$PKG/proton-stream.ico" \
    -D "ReadMe=$OUTDIR/README.md" \
    -o "$out" "$PKG/proton-stream.wixl.wxs"
@@ -229,7 +229,7 @@ Priority: optional
 Architecture: $arch
 Maintainer: Nils Pukropp <contact@narl.io>
 Installed-Size: $size
-Depends: libc6, libmpv2 | libmpv1, libsecret-1-0, libgl1, libxkbcommon0, libx11-6, libwayland-client0
+Depends: libc6, libmpv2 | libmpv1, libsecret-1-0, libwebkit2gtk-4.1-0, libgl1, libxkbcommon0, libx11-6, libwayland-client0
 Recommends: gnome-keyring
 Homepage: https://github.com/narrrl/proton-stream
 Description: Netflix-style desktop client for Proton Drive public links