diff --git a/CLAUDE.md b/CLAUDE.md
index 7f4111a..7e219ce 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -97,6 +97,14 @@ persistence) → GUI (Qt widgets that read the manager and connect to its signal
   so the desktop's media keys / now-playing popup control playback. Spacebar and
   arrow keys are handled locally via `MainWindow.eventFilter`.
 
+- **`lintunes/device_sync.py`** — one-way playlist sync to the Rabbit R1 (Device
+  menu). The Rabbit mounts via **MTP/gvfs** (a FUSE path under
+  `/run/user/<uid>/gvfs`), not mass storage — so plain file I/O, but never
+  copystat and never trust mtimes (diff by name+size). Sync owns exactly
+  `Music/<Playlist Name>/` on the device (creates/overwrites/deletes there,
+  plus an Auxio-importable `.m3u`); it never deletes outside that folder and
+  only ever *reads* local library files.
+
 ## Conventions & gotchas
 
 - **Tests are organized as `tests/test_roundN.py`** — each development round adds
diff --git a/TASKS.md b/TASKS.md
index d552718..fa74571 100644
--- a/TASKS.md
+++ b/TASKS.md
@@ -3,6 +3,40 @@
 Legend: `[ ]` todo · `[~]` in progress · `[x]` done.
 When a round closes, move its finished items to `tasks-done.md`.
 
+
+
+# tasks
+
+- [ ] ability to delete songs from library
+- [ ] archive the done tasks in here to another file, this is crufty....
+
+
+
+
+
+
+
+
+
+
+
+
+
+# old
+
+## Round 26 — Device menu: sync playlist to Rabbit R1 (v0.2.0)
+
+- [x] Device menu (left of Track) with "Sync Playlist to Rabbit"; grayed out on
+  the Library view, while syncing, or when no Rabbit is plugged in.
+- [x] `device_sync.py`: MTP/gvfs detection (the Rabbit mounts via MTP, not mass
+  storage), name+size incremental diff, stale-file deletion scoped to the
+  playlist's own folder, Auxio-importable `.m3u`, chunked-copy worker thread.
+- [x] Up-front free-space check with a needed-vs-available alert.
+- [x] Right-justified sync progress bar in the status bar (version left,
+  totals middle, sync right).
+
+Tests in `tests/test_round26.py`. Feature round → minor bump **0.2.0**.
+
 ## Round 25 — folder highlight while dragging a playlist (v0.1.6)
 
 Tests in `tests/test_round25.py`. Fix round → patch bump **0.1.6**.
diff --git a/lintunes/__init__.py b/lintunes/__init__.py
index a7ab430..672967b 100644
--- a/lintunes/__init__.py
+++ b/lintunes/__init__.py
@@ -1,3 +1,3 @@
 """LinTunes — iTunes-style music library manager and player for Linux."""
 
-__version__ = "0.1.6"
+__version__ = "0.2.0"
diff --git a/lintunes/device_sync.py b/lintunes/device_sync.py
new file mode 100644
index 0000000..f1cde9b
--- /dev/null
+++ b/lintunes/device_sync.py
@@ -0,0 +1,272 @@
+"""One-way playlist sync to a USB-connected media player (Rabbit R1).
+
+The Rabbit mounts over MTP, which gvfs exposes as a FUSE directory under
+/run/user/<uid>/gvfs — so plain file I/O works, with two MTP caveats honored
+throughout: never copy metadata (copystat raises EPERM on gvfs-MTP) and never
+trust mtimes (compare files by name + size instead).
+
+Contract: sync is strictly lintunes → device. LinTunes owns exactly
+``Music/<Playlist Name>/`` on the device — files there are created, replaced,
+and deleted freely to mirror the playlist, but nothing outside that folder is
+ever touched (sibling playlist folders, Android's ``.thumbnails``), and local
+library files are only ever read. A playlist renamed in lintunes syncs to a
+fresh folder; the old one is left for manual cleanup. Alongside the audio
+files an ``.m3u`` (UTF-8, filenames relative to its own folder) carries the
+playlist order — the format Auxio on the Rabbit imports.
+"""
+
+import os
+import re
+import threading
+from dataclasses import dataclass, field
+from pathlib import Path
+
+from PyQt6.QtCore import QObject, pyqtSignal
+
+CHUNK = 1024 * 1024                 # copy unit; also the progress granularity
+SPACE_MARGIN = 16 * 1024 * 1024     # headroom the free-space check insists on
+
+# Characters Android/FAT-style storage can't take in a filename.
+_FORBIDDEN = re.compile(r'[\\/:*?"<>|\x00-\x1f]')
+
+
+@dataclass
+class Device:
+    name: str        # human name for UI strings, e.g. "Rabbit R1"
+    root: Path       # storage root ("Internal shared storage") — disk_usage target
+    music_dir: Path  # root / "Music"
+
+
+def find_rabbit(gvfs_root: Path | None = None) -> Device | None:
+    """The connected Rabbit R1's storage, or None when it isn't plugged in."""
+    if gvfs_root is None:
+        gvfs_root = Path(f"/run/user/{os.getuid()}/gvfs")
+    try:
+        mounts = list(gvfs_root.iterdir())
+    except OSError:
+        return None
+    for mount in mounts:
+        if not mount.name.startswith("mtp:host=") or "rabbit" not in mount.name.lower():
+            continue
+        try:
+            # The single MTP storage volume ("Internal shared storage").
+            storage = next((c for c in sorted(mount.iterdir()) if c.is_dir()), None)
+        except OSError:
+            continue
+        if storage is not None:
+            return Device("Rabbit R1", storage, storage / "Music")
+    return None
+
+
+def find_device() -> Device | None:
+    """The first supported connected device (only the Rabbit for now)."""
+    return find_rabbit()
+
+
+def sanitize_name(name: str) -> str:
+    """A playlist/track name reduced to a safe cross-filesystem filename."""
+    cleaned = " ".join(_FORBIDDEN.sub(" ", name).split())
+    cleaned = cleaned.strip(". ")[:150].strip(". ")
+    return cleaned or "Untitled"
+
+
+def track_display(track) -> str:
+    """The 'Artist - Title' line shown in the m3u and progress text."""
+    name = track.name or Path(track.location).stem or f"Track {track.track_id}"
+    return f"{track.artist} - {name}" if track.artist else name
+
+
+def track_filename(track) -> str:
+    ext = Path(track.location).suffix
+    return sanitize_name(track_display(track)) + ext
+
+
+def format_bytes(n: int) -> str:
+    for unit in ("B", "KB", "MB", "GB"):
+        if n < 1024 or unit == "GB":
+            return f"{n:.1f} {unit}" if unit != "B" else f"{n} B"
+        n /= 1024
+    return f"{n:.1f} GB"
+
+
+@dataclass
+class SyncItem:
+    track_id: int
+    src: Path
+    dest_name: str
+    size: int
+
+
+@dataclass
+class SyncPlan:
+    device: Device
+    playlist_name: str
+    dest_dir: Path
+    m3u_name: str
+    copies: list = field(default_factory=list)    # SyncItems to (re)copy
+    kept: int = 0                                 # already on device, same size
+    stale: list = field(default_factory=list)     # filenames in dest_dir to delete
+    skipped: int = 0                              # tracks with no usable local file
+    entries: list = field(default_factory=list)   # (dest_name, secs, display) m3u order
+    bytes_to_copy: int = 0
+    bytes_freed: int = 0
+
+
+def plan_sync(playlist_name: str, tracks: list, music_dir: Path,
+              device: Device | None = None) -> SyncPlan:
+    """Diff the playlist against what's already in its device folder.
+
+    Pure planning — nothing is created, copied, or deleted here. Existing
+    device files matching by name + size are kept; everything else in the
+    folder (old m3us included) is marked stale. Subdirectories are never
+    touched.
+    """
+    folder = sanitize_name(playlist_name)
+    plan = SyncPlan(device=device, playlist_name=playlist_name,
+                    dest_dir=music_dir / folder, m3u_name=folder + ".m3u")
+
+    # Resolve each unique track to a real local file.
+    items: dict[int, SyncItem] = {}
+    usable: list = []
+    seen_skipped: set[int] = set()
+    for track in tracks:
+        if track.track_id in items:
+            usable.append(track)
+            continue
+        if track.track_id in seen_skipped:
+            continue
+        src = Path(track.location) if track.location else None
+        if src is None or not src.is_file():
+            seen_skipped.add(track.track_id)
+            continue
+        items[track.track_id] = SyncItem(
+            track.track_id, src, track_filename(track), src.stat().st_size)
+        usable.append(track)
+    plan.skipped = len(seen_skipped)
+
+    # Disambiguate name collisions with a stable [track_id] suffix. Every
+    # member of a colliding group gets the suffix (not just the "second" one)
+    # so names never depend on playlist order or membership history.
+    by_name: dict[str, list[SyncItem]] = {}
+    for item in items.values():
+        by_name.setdefault(item.dest_name, []).append(item)
+    for group in by_name.values():
+        if len(group) > 1:
+            for item in group:
+                stem, ext = os.path.splitext(item.dest_name)
+                item.dest_name = f"{stem} [{item.track_id}]{ext}"
+
+    for track in usable:
+        item = items[track.track_id]
+        plan.entries.append(
+            (item.dest_name, round(track.total_time / 1000), track_display(track)))
+
+    # Diff against the device folder by name + size (mtimes lie over MTP).
+    on_device: dict[str, int] = {}
+    try:
+        for entry in os.scandir(plan.dest_dir):
+            if entry.is_file(follow_symlinks=False):
+                on_device[entry.name] = entry.stat().st_size
+    except FileNotFoundError:
+        pass
+
+    expected = {item.dest_name for item in items.values()} | {plan.m3u_name}
+    for item in items.values():
+        if on_device.get(item.dest_name) == item.size:
+            plan.kept += 1
+        else:
+            plan.copies.append(item)
+            plan.bytes_to_copy += item.size
+    for name, size in on_device.items():
+        if name not in expected:
+            plan.stale.append(name)
+            plan.bytes_freed += size
+    return plan
+
+
+def build_m3u(entries: list) -> str:
+    lines = ["#EXTM3U"]
+    for dest_name, secs, display in entries:
+        lines.append(f"#EXTINF:{secs},{display}")
+        lines.append(dest_name)
+    return "\n".join(lines) + "\n"
+
+
+class DeviceSyncWorker(QObject):
+    """Runs a SyncPlan on a daemon thread, reporting through signals.
+
+    Progress is emitted in KiB (a pyqtSignal(int) is a C int — byte counts
+    overflow past 2 GiB). An unplug mid-copy surfaces as `failed`; the next
+    sync self-heals because the partial file loses the name+size diff.
+    """
+
+    progress = pyqtSignal(int, int, str)  # done_kib, total_kib, "12/240 Artist - Title"
+    finished = pyqtSignal(dict)
+    failed = pyqtSignal(str)
+
+    def __init__(self, plan: SyncPlan, parent=None):
+        super().__init__(parent)
+        self._plan = plan
+        self._busy = False
+
+    def busy(self) -> bool:
+        return self._busy
+
+    def start(self):
+        if self._busy:
+            return
+        self._busy = True
+        threading.Thread(target=self._run_guarded, daemon=True).start()
+
+    def _run_guarded(self):
+        try:
+            self._run()
+        finally:
+            self._busy = False
+
+    def _run(self):
+        plan = self._plan
+        dest = None
+        try:
+            plan.dest_dir.mkdir(parents=True, exist_ok=True)
+            removed = 0
+            for name in plan.stale:
+                try:
+                    (plan.dest_dir / name).unlink()
+                    removed += 1
+                except OSError:
+                    pass  # one stubborn file shouldn't kill the sync
+            total_kib = max(plan.bytes_to_copy // 1024, 1)
+            done = 0
+            for i, item in enumerate(plan.copies, start=1):
+                label = f"{i}/{len(plan.copies)} {Path(item.dest_name).stem}"
+                dest = plan.dest_dir / item.dest_name
+                # Manual chunked copy: byte-accurate progress, and no
+                # copystat (gvfs-MTP rejects it).
+                with open(item.src, "rb") as fsrc, open(dest, "wb") as fdst:
+                    while True:
+                        chunk = fsrc.read(CHUNK)
+                        if not chunk:
+                            break
+                        fdst.write(chunk)
+                        done += len(chunk)
+                        self.progress.emit(done // 1024, total_kib, label)
+                dest = None
+            # Written last so an interrupted sync leaves the old m3u intact.
+            (plan.dest_dir / plan.m3u_name).write_text(
+                build_m3u(plan.entries), encoding="utf-8")
+            device_name = plan.device.name if plan.device else "device"
+            self.finished.emit({
+                "playlist": plan.playlist_name, "device": device_name,
+                "copied": len(plan.copies), "kept": plan.kept,
+                "removed": removed, "skipped": plan.skipped,
+            })
+        except OSError as e:
+            if dest is not None:
+                try:
+                    dest.unlink()  # drop the half-copied file if the mount survives
+                except OSError:
+                    pass
+            device_name = plan.device.name if plan.device else "device"
+            self.failed.emit(
+                f"Sync failed: {e}. Is the {device_name} still connected?")
diff --git a/lintunes/gui/main_window.py b/lintunes/gui/main_window.py
index 4df36b7..7ffd653 100644
--- a/lintunes/gui/main_window.py
+++ b/lintunes/gui/main_window.py
@@ -1,14 +1,15 @@
+import shutil
 from pathlib import Path
 
 from PyQt6.QtWidgets import (
     QMainWindow, QSplitter, QStackedWidget, QWidget, QVBoxLayout, QLineEdit,
     QPlainTextEdit, QTextEdit, QAbstractSpinBox, QComboBox, QApplication,
-    QLabel, QMessageBox, QFileDialog,
+    QLabel, QMessageBox, QFileDialog, QProgressBar,
 )
 from PyQt6.QtCore import Qt, QEvent, QTimer
 from PyQt6.QtGui import QAction, QKeySequence
 
-from lintunes import mpris, tagging, theme
+from lintunes import device_sync, mpris, tagging, theme
 from lintunes.art_search import AlbumArtFetcher
 from lintunes.eventlog import log_control
 from lintunes.inhibit import SleepInhibitor
@@ -101,6 +102,15 @@ class MainWindow(QMainWindow):
             lambda msg: self.statusBar().showMessage(msg, 8000))
         self._updater.update_applied.connect(self._restart_for_update)
         self._updater.start_checking()
+        # Device-sync progress, right-justified: permanent widgets sit on the
+        # status bar's right and survive showMessage. No stretch (see above)
+        # and hidden while idle so it costs no space.
+        self._sync_progress = QProgressBar()
+        self._sync_progress.setFixedWidth(220)
+        self._sync_progress.setTextVisible(True)
+        self._sync_progress.hide()
+        self.statusBar().addPermanentWidget(self._sync_progress)
+        self._sync_worker = None
 
         # Wiring
         self._transport.play_clicked.connect(self.play_pause)
@@ -226,6 +236,15 @@ class MainWindow(QMainWindow):
         self._add_action(view_menu, "Toggle Column Browser", "Ctrl+B",
                          self._library_view.toggle_browser)
 
+        device_menu = bar.addMenu("&Device")
+        self._sync_action = self._add_action(
+            device_menu, "Sync Playlist to Rabbit", "",
+            self._sync_playlist_to_device)
+        self._sync_action.setEnabled(False)
+        # Re-checked every time the menu opens: cheap (one gvfs listdir), and
+        # always reflects plug/unplug and the current view.
+        device_menu.aboutToShow.connect(self._refresh_device_actions)
+
         track_menu = bar.addMenu("&Track")
         self._add_action(track_menu, "Get Info", "Ctrl+I", self._info_for_current_view)
         self._add_action(track_menu, "Go to Current Song", "Ctrl+L",
@@ -250,6 +269,72 @@ class MainWindow(QMainWindow):
         self._redo_action.setText(
             f"Redo {stack.redo_label()}" if can_redo else "Redo")
 
+    # ---- device sync ----
+
+    def _refresh_device_actions(self):
+        syncing = self._sync_worker is not None and self._sync_worker.busy()
+        on_playlist = (self._content.currentWidget() is self._playlist_view
+                       and bool(self._playlist_view.playlist_id))
+        self._sync_action.setEnabled(
+            not syncing and on_playlist
+            and device_sync.find_device() is not None)
+
+    def _sync_playlist_to_device(self):
+        # Everything may have changed since the menu opened — re-verify.
+        if self._sync_worker is not None and self._sync_worker.busy():
+            return
+        device = device_sync.find_device()
+        playlist = self._manager.library.playlists.get(
+            self._playlist_view.playlist_id)
+        if device is None or playlist is None:
+            return
+        tracks = [self._manager.library.tracks[tid]
+                  for tid in playlist.track_ids
+                  if tid in self._manager.library.tracks]
+        try:
+            plan = device_sync.plan_sync(
+                playlist.name, tracks, device.music_dir, device)
+            free = shutil.disk_usage(device.root).free
+        except OSError as e:
+            QMessageBox.warning(self, "Sync failed",
+                                f"Couldn't read the {device.name}: {e}")
+            return
+        needed = plan.bytes_to_copy + device_sync.SPACE_MARGIN
+        if free + plan.bytes_freed < needed:
+            QMessageBox.warning(
+                self, "Not enough space",
+                f"Syncing “{playlist.name}” needs "
+                f"{device_sync.format_bytes(needed - plan.bytes_freed)}, but the "
+                f"{device.name} only has {device_sync.format_bytes(free)} free.")
+            return
+        self._sync_worker = device_sync.DeviceSyncWorker(plan, self)
+        self._sync_worker.progress.connect(self._on_sync_progress)
+        self._sync_worker.finished.connect(self._on_sync_finished)
+        self._sync_worker.failed.connect(self._on_sync_failed)
+        self._sync_progress.setRange(0, max(plan.bytes_to_copy // 1024, 1))
+        self._sync_progress.setValue(0)
+        self._sync_progress.setFormat(f"Syncing “{playlist.name}”…")
+        self._sync_progress.show()
+        self._sync_worker.start()
+
+    def _on_sync_progress(self, done_kib, total_kib, label):
+        self._sync_progress.setRange(0, total_kib)
+        self._sync_progress.setValue(done_kib)
+        self._sync_progress.setFormat(f"Syncing {label} · %p%")
+
+    def _on_sync_finished(self, summary):
+        self._sync_progress.hide()
+        msg = (f"Synced “{summary['playlist']}” to the {summary['device']}: "
+               f"{summary['copied']} copied, {summary['kept']} up to date, "
+               f"{summary['removed']} removed")
+        if summary["skipped"]:
+            msg += f", {summary['skipped']} skipped (no local file)"
+        self.statusBar().showMessage(msg, 8000)
+
+    def _on_sync_failed(self, message):
+        self._sync_progress.hide()
+        QMessageBox.warning(self, "Sync failed", message)
+
     # ---- view switching ----
 
     def _show_library(self):
diff --git a/tests/test_round26.py b/tests/test_round26.py
new file mode 100644
index 0000000..ed18e22
--- /dev/null
+++ b/tests/test_round26.py
@@ -0,0 +1,224 @@
+"""Round 26: Device menu — sync a playlist to the Rabbit R1.
+
+The Rabbit connects over MTP/gvfs (a FUSE path), so all sync logic lives in
+device_sync.py as plain file I/O testable against tmp_path stand-ins: a fake
+gvfs tree for detection, a fake device Music dir for planning and copying.
+The diff is name+size (MTP mtimes are unreliable), collision suffixes are
+order-independent, and only files inside the playlist's own folder are ever
+deleted.
+"""
+
+import os
+
+import pytest
+
+from lintunes import device_sync
+from lintunes.device_sync import (
+    DeviceSyncWorker, build_m3u, find_rabbit, plan_sync, sanitize_name,
+    track_filename,
+)
+from lintunes.models import Track
+
+
+def _track(tid, name, artist, path, total_time=180_000):
+    return Track(track_id=tid, name=name, artist=artist,
+                 location=str(path), total_time=total_time)
+
+
+def _audio(tmp_path, filename, data=b"x" * 100):
+    path = tmp_path / "local" / filename
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_bytes(data)
+    return path
+
+
+class TestNames:
+    def test_sanitize_strips_forbidden_chars(self):
+        assert sanitize_name('Road / Trip: "mix"?') == "Road Trip mix"
+
+    def test_sanitize_trims_dots_and_spaces(self):
+        assert sanitize_name("  ..hits..  ") == "hits"
+
+    def test_sanitize_empty_falls_back(self):
+        assert sanitize_name("???") == "Untitled"
+
+    def test_track_filename_artist_and_title(self, tmp_path):
+        src = _audio(tmp_path, "whatever.mp3")
+        track = _track(1, "Song", "Band", src)
+        assert track_filename(track) == "Band - Song.mp3"
+
+    def test_track_filename_no_artist(self, tmp_path):
+        src = _audio(tmp_path, "whatever.m4a")
+        assert track_filename(_track(1, "Song", "", src)) == "Song.m4a"
+
+    def test_track_filename_falls_back_to_stem(self, tmp_path):
+        src = _audio(tmp_path, "raw_rip.mp3")
+        assert track_filename(_track(1, "", "", src)) == "raw_rip.mp3"
+
+
+class TestPlan:
+    def test_fresh_sync_copies_everything(self, tmp_path):
+        a = _audio(tmp_path, "a.mp3", b"a" * 50)
+        b = _audio(tmp_path, "b.mp3", b"b" * 70)
+        tracks = [_track(1, "A", "X", a), _track(2, "B", "Y", b)]
+        plan = plan_sync("Mix", tracks, tmp_path / "Music")
+
+        assert plan.dest_dir == tmp_path / "Music" / "Mix"
+        assert plan.m3u_name == "Mix.m3u"
+        assert [i.dest_name for i in plan.copies] == ["X - A.mp3", "Y - B.mp3"]
+        assert plan.bytes_to_copy == 120
+        assert plan.kept == 0 and not plan.stale and plan.skipped == 0
+
+    def test_incremental_keeps_matching_and_deletes_stale(self, tmp_path):
+        a = _audio(tmp_path, "a.mp3", b"a" * 50)
+        b = _audio(tmp_path, "b.mp3", b"b" * 70)
+        dest = tmp_path / "Music" / "Mix"
+        dest.mkdir(parents=True)
+        (dest / "X - A.mp3").write_bytes(b"a" * 50)   # same size -> kept
+        (dest / "Y - B.mp3").write_bytes(b"old")      # size mismatch -> recopy
+        (dest / "Gone - Track.mp3").write_bytes(b"z" * 30)  # stale
+        (dest / "Old Name.m3u").write_bytes(b"#EXTM3U\n")   # stale old m3u
+        (dest / "subdir").mkdir()                     # never touched
+
+        tracks = [_track(1, "A", "X", a), _track(2, "B", "Y", b)]
+        plan = plan_sync("Mix", tracks, tmp_path / "Music")
+
+        assert plan.kept == 1
+        assert [i.dest_name for i in plan.copies] == ["Y - B.mp3"]
+        assert sorted(plan.stale) == ["Gone - Track.mp3", "Old Name.m3u"]
+        assert plan.bytes_freed == 30 + len(b"#EXTM3U\n")
+
+    def test_collision_suffixes_are_order_independent(self, tmp_path):
+        a = _audio(tmp_path, "a.mp3")
+        b = _audio(tmp_path, "b.mp3")
+        t1, t2 = _track(1, "Same", "Band", a), _track(2, "Same", "Band", b)
+
+        names = {i.track_id: i.dest_name
+                 for i in plan_sync("Mix", [t1, t2], tmp_path / "Music").copies}
+        reversed_names = {i.track_id: i.dest_name
+                          for i in plan_sync("Mix", [t2, t1],
+                                             tmp_path / "Music").copies}
+        assert names == reversed_names
+        assert names[1] == "Band - Same [1].mp3"
+        assert names[2] == "Band - Same [2].mp3"
+
+    def test_missing_locations_are_skipped(self, tmp_path):
+        real = _audio(tmp_path, "real.mp3")
+        tracks = [
+            _track(1, "Real", "X", real),
+            _track(2, "No file", "X", tmp_path / "nope.mp3"),
+            Track(track_id=3, name="No location", location=""),
+        ]
+        plan = plan_sync("Mix", tracks, tmp_path / "Music")
+        assert plan.skipped == 2
+        assert len(plan.copies) == 1 and len(plan.entries) == 1
+
+    def test_duplicate_track_ids_copy_once_listed_twice(self, tmp_path):
+        a = _audio(tmp_path, "a.mp3")
+        track = _track(1, "A", "X", a)
+        plan = plan_sync("Mix", [track, track], tmp_path / "Music")
+        assert len(plan.copies) == 1
+        assert [e[0] for e in plan.entries] == ["X - A.mp3", "X - A.mp3"]
+
+    def test_folder_and_m3u_use_sanitized_name(self, tmp_path):
+        plan = plan_sync("Road / Trip?", [], tmp_path / "Music")
+        assert plan.dest_dir.name == "Road Trip"
+        assert plan.m3u_name == "Road Trip.m3u"
+
+
+class TestM3u:
+    def test_build_m3u(self):
+        text = build_m3u([("X - A.mp3", 181, "X - A"), ("Y - B.mp3", 45, "Y - B")])
+        assert text == ("#EXTM3U\n"
+                        "#EXTINF:181,X - A\nX - A.mp3\n"
+                        "#EXTINF:45,Y - B\nY - B.mp3\n")
+
+    def test_entry_seconds_round_from_ms(self, tmp_path):
+        a = _audio(tmp_path, "a.mp3")
+        plan = plan_sync("Mix", [_track(1, "A", "X", a, total_time=181_499)],
+                         tmp_path / "Music")
+        assert plan.entries[0][1] == 181
+
+
+class TestWorker:
+    def _synced(self, qapp, plan):
+        worker = DeviceSyncWorker(plan)
+        results = {}
+        worker.finished.connect(lambda s: results.update(s))
+        worker.failed.connect(lambda m: results.update(error=m))
+        worker._run()  # synchronously on the test thread; signals fire directly
+        return results
+
+    def test_end_to_end(self, qapp, tmp_path):
+        a = _audio(tmp_path, "a.mp3", os.urandom(3 * 1024) )
+        b = _audio(tmp_path, "b.mp3", b"b" * 70)
+        dest = tmp_path / "Music" / "Mix"
+        dest.mkdir(parents=True)
+        (dest / "Stale.mp3").write_bytes(b"old")
+        tracks = [_track(1, "A", "X", a), _track(2, "B", "Y", b)]
+        plan = plan_sync("Mix", tracks, tmp_path / "Music")
+
+        summary = self._synced(qapp, plan)
+
+        assert summary["copied"] == 2 and summary["removed"] == 1
+        assert (dest / "X - A.mp3").read_bytes() == a.read_bytes()
+        assert (dest / "Y - B.mp3").read_bytes() == b.read_bytes()
+        assert not (dest / "Stale.mp3").exists()
+        assert (dest / "Mix.m3u").read_text(encoding="utf-8") == build_m3u(
+            plan.entries)
+
+    def test_progress_reports_kib(self, qapp, tmp_path):
+        a = _audio(tmp_path, "a.mp3", b"a" * (2 * device_sync.CHUNK))
+        plan = plan_sync("Mix", [_track(1, "A", "X", a)], tmp_path / "Music")
+        worker = DeviceSyncWorker(plan)
+        seen = []
+        worker.progress.connect(lambda d, t, l: seen.append((d, t, l)))
+        worker._run()
+        assert seen[-1][0] == seen[-1][1] == 2 * device_sync.CHUNK // 1024
+        assert "1/1" in seen[-1][2]
+
+    def test_source_vanishing_reports_failure(self, qapp, tmp_path):
+        a = _audio(tmp_path, "a.mp3")
+        plan = plan_sync("Mix", [_track(1, "A", "X", a)], tmp_path / "Music")
+        a.unlink()  # unplugged/deleted between plan and run
+        result = self._synced(qapp, plan)
+        assert "Sync failed" in result["error"]
+        # No half-copied file left behind at full-looking size.
+        leftover = plan.dest_dir / "X - A.mp3"
+        assert not leftover.exists() or leftover.stat().st_size != plan.copies[0].size
+
+    def test_empty_playlist_clears_folder(self, qapp, tmp_path):
+        dest = tmp_path / "Music" / "Mix"
+        dest.mkdir(parents=True)
+        (dest / "Old - Song.mp3").write_bytes(b"x")
+        plan = plan_sync("Mix", [], tmp_path / "Music")
+        summary = self._synced(qapp, plan)
+        assert summary["removed"] == 1
+        assert sorted(p.name for p in dest.iterdir()) == ["Mix.m3u"]
+        assert (dest / "Mix.m3u").read_text() == "#EXTM3U\n"
+
+
+class TestFindRabbit:
+    def _gvfs(self, tmp_path, host):
+        storage = tmp_path / "gvfs" / host / "Internal shared storage"
+        (storage / "Music").mkdir(parents=True)
+        return tmp_path / "gvfs"
+
+    def test_finds_rabbit_mount(self, tmp_path):
+        gvfs = self._gvfs(tmp_path, "mtp:host=unknown_Rabbit_R1_919109A4")
+        device = find_rabbit(gvfs)
+        assert device is not None
+        assert device.name == "Rabbit R1"
+        assert device.music_dir == (gvfs / "mtp:host=unknown_Rabbit_R1_919109A4"
+                                    / "Internal shared storage" / "Music")
+
+    def test_match_is_case_insensitive(self, tmp_path):
+        gvfs = self._gvfs(tmp_path, "mtp:host=RABBIT_r1_abc")
+        assert find_rabbit(gvfs) is not None
+
+    def test_ignores_other_mtp_devices(self, tmp_path):
+        gvfs = self._gvfs(tmp_path, "mtp:host=Google_Pixel_8_xyz")
+        assert find_rabbit(gvfs) is None
+
+    def test_no_gvfs_dir_is_none(self, tmp_path):
+        assert find_rabbit(tmp_path / "does-not-exist") is None