feat: add watch command and pipe view

src/lrx_cli/cache.py

@@ -85,9 +85,15 @@ class CacheEngine:
         self.db_path = db_path
         self._init_db()
 
+    def _connect(self) -> sqlite3.Connection:
+        conn = sqlite3.connect(self.db_path)
+        conn.execute("PRAGMA journal_mode=WAL")
+        conn.execute("PRAGMA busy_timeout=5000")
+        return conn
+
     def _init_db(self) -> None:
         """Create cache tables and run one-time slot/cache migrations."""
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.execute("""
                 CREATE TABLE IF NOT EXISTS credentials (
                     name TEXT PRIMARY KEY,
@@ -256,7 +262,7 @@ class CacheEngine:
             return []
 
         now = int(time.time())
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.execute(
                 "DELETE FROM cache WHERE key = ? AND expires_at IS NOT NULL AND expires_at < ?",
                 (key, now),
@@ -353,7 +359,7 @@ class CacheEngine:
             # Convenience for callers that still pass a single negative result.
             kinds = [SLOT_SYNCED, SLOT_UNSYNCED]
 
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             for kind in kinds:
                 conn.execute(
                     """INSERT OR REPLACE INTO cache
@@ -386,7 +392,7 @@ class CacheEngine:
 
     def clear_all(self) -> None:
         """Remove every entry from the cache."""
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.execute("DELETE FROM cache")
             conn.commit()
         logger.info("Cache cleared.")
@@ -396,7 +402,7 @@ class CacheEngine:
         if not self._track_has_meta(track):
             logger.info(f"No cache entries found for {track.display_name()}.")
             return
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             cur = conn.execute(
                 f"DELETE FROM cache WHERE {_TRACK_WHERE}",
                 _track_where_params(track),
@@ -411,7 +417,7 @@ class CacheEngine:
 
     def prune(self) -> int:
         """Remove all expired entries. Returns the number of rows deleted."""
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             cur = conn.execute(
                 "DELETE FROM cache WHERE expires_at IS NOT NULL AND expires_at < ?",
                 (int(time.time()),),
@@ -439,7 +445,7 @@ class CacheEngine:
             return None
 
         now = int(time.time())
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.row_factory = sqlite3.Row
             rows = conn.execute(
                 f"SELECT status, lyrics, source, confidence FROM cache"
@@ -495,7 +501,7 @@ class CacheEngine:
             return []
 
         now = int(time.time())
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.row_factory = sqlite3.Row
             rows = conn.execute(
                 """SELECT * FROM cache
@@ -557,7 +563,7 @@ class CacheEngine:
         """
         if not self._track_has_meta(track):
             return 0
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             cur = conn.execute(
                 f"UPDATE cache SET confidence = ? WHERE {_TRACK_WHERE} AND source = ?",
                 [confidence] + _track_where_params(track) + [source],
@@ -571,7 +577,7 @@ class CacheEngine:
         """Return all cached rows for a given track (across all sources)."""
         if not self._track_has_meta(track):
             return []
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.row_factory = sqlite3.Row
             return [
                 dict(r)
@@ -586,7 +592,7 @@ class CacheEngine:
     def get_credential(self, name: str) -> Optional[dict]:
         """Return cached credential data if present and not expired."""
         now_ms = int(time.time() * 1000)
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.row_factory = sqlite3.Row
             row = conn.execute(
                 "SELECT data FROM credentials WHERE name = ? AND (expires_at IS NULL OR expires_at > ?)",
@@ -603,7 +609,7 @@ class CacheEngine:
         self, name: str, data: dict, expires_at_ms: Optional[int] = None
     ) -> None:
         """Persist credential data, optionally with an expiry timestamp (Unix ms)."""
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.execute(
                 "INSERT OR REPLACE INTO credentials (name, data, expires_at) VALUES (?, ?, ?)",
                 (name, json.dumps(data), expires_at_ms),
@@ -612,14 +618,14 @@ class CacheEngine:
 
     def query_all(self) -> list[dict]:
         """Return every row in the cache table."""
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             conn.row_factory = sqlite3.Row
             return [dict(r) for r in conn.execute("SELECT * FROM cache").fetchall()]
 
     def stats(self) -> dict:
         """Return aggregate cache statistics."""
         now = int(time.time())
-        with sqlite3.connect(self.db_path) as conn:
+        with self._connect() as conn:
             total = conn.execute("SELECT COUNT(*) FROM cache").fetchone()[0]
             expired = conn.execute(
                 "SELECT COUNT(*) FROM cache WHERE expires_at IS NOT NULL AND expires_at < ?",

src/lrx_cli/cli.py

@@ -7,18 +7,33 @@ Description: CLI interface.
 import sys
 import time
 import os
+import asyncio
+import json
 from pathlib import Path
 from typing import Annotated
 from urllib.parse import quote
 import cyclopts
 from loguru import logger
 
-from .config import DB_PATH, enable_debug
+from .config import (
+    DB_PATH,
+    PLAYER_BLACKLIST,
+    PREFERRED_PLAYER,
+    WATCH_CALIBRATION_INTERVAL_S,
+    WATCH_DEBOUNCE_MS,
+    WATCH_POSITION_TICK_MS,
+    WATCH_SOCKET_PATH,
+    enable_debug,
+)
 from .models import TrackMeta
 from .mpris import get_current_track
 from .core import LrcManager
 from .fetchers import FetcherMethodType
 from .lrc import get_sidecar_path
+from .watch import WatchCoordinator
+from .watch.control import ControlClient, parse_delta
+from .watch.options import WatchOptions
+from .watch.view.pipe import PipeOutput
 
 
 app = cyclopts.App(
@@ -29,6 +44,12 @@ app.register_install_completion_command()
 cache_app = cyclopts.App(name="cache", help="Manage the local SQLite cache.")
 app.command(cache_app)
 
+watch_app = cyclopts.App(name="watch", help="Watch MPRIS and output lyrics.")
+app.command(watch_app)
+
+ctl_app = cyclopts.App(name="ctl", help="Control a running watch session.")
+watch_app.command(ctl_app)
+
 
 # Global state set by the meta launcher
 _player: str | None = None
@@ -38,6 +59,18 @@ _db_path: str | None = None
 manager: LrcManager = None  # type: ignore
 
 
+def _build_watch_options() -> WatchOptions:
+    """Build runtime watch options from CLI composition root."""
+    return WatchOptions(
+        preferred_player=PREFERRED_PLAYER,
+        player_blacklist=tuple(PLAYER_BLACKLIST),
+        debounce_ms=WATCH_DEBOUNCE_MS,
+        position_tick_ms=WATCH_POSITION_TICK_MS,
+        calibration_interval_s=WATCH_CALIBRATION_INTERVAL_S,
+        socket_path=WATCH_SOCKET_PATH,
+    )
+
+
 @app.meta.default
 def launcher(
     *tokens: Annotated[str, cyclopts.Parameter(show=False, allow_leading_hyphen=True)],
@@ -357,6 +390,74 @@ def export(
         sys.exit(1)
 
 
+# watch subcommands
+
+
+@watch_app.command
+def pipe(
+    before: Annotated[
+        int,
+        cyclopts.Parameter(
+            name="--before",
+            help="Number of lyric lines to show before current line.",
+        ),
+    ] = 0,
+    after: Annotated[
+        int,
+        cyclopts.Parameter(
+            name="--after",
+            help="Number of lyric lines to show after current line.",
+        ),
+    ] = 0,
+):
+    """Watch active player and continuously print lyric window to stdout."""
+    logger.info(
+        "Starting watch pipe (player filter: {})",
+        _player or "<none>",
+    )
+    output = PipeOutput(before=max(0, before), after=max(0, after))
+    options = _build_watch_options()
+    try:
+        session = WatchCoordinator(
+            manager,
+            output,
+            player_hint=_player,
+            options=options,
+        )
+        success = asyncio.run(session.run())
+        if not success:
+            sys.exit(1)
+    except KeyboardInterrupt:
+        logger.info("Watch stopped.")
+
+
+@ctl_app.command
+def offset(delta: str) -> None:
+    """Adjust watch offset. Examples: +200, -200, 0."""
+    parsed_ok, parsed_delta, parse_error = parse_delta(delta)
+    if not parsed_ok or parsed_delta is None:
+        logger.error(parse_error or "Invalid offset delta")
+        sys.exit(1)
+
+    response = ControlClient(options=_build_watch_options()).send(
+        {"cmd": "offset", "delta": parsed_delta}
+    )
+    if not response.get("ok"):
+        logger.error(response.get("error", "Unknown error"))
+        sys.exit(1)
+    print(json.dumps(response, indent=2, ensure_ascii=False))
+
+
+@ctl_app.command
+def status() -> None:
+    """Print current watch session status as JSON."""
+    response = ControlClient(options=_build_watch_options()).send({"cmd": "status"})
+    if not response.get("ok"):
+        logger.error(response.get("error", "Unknown error"))
+        sys.exit(1)
+    print(json.dumps(response, indent=2, ensure_ascii=False))
+
+
 # cache subcommands
 
 

src/lrx_cli/config.py

@@ -68,6 +68,17 @@ MUSIXMATCH_COOLDOWN_MS = 600_000  # 10 minutes
 
 # Player preference (used when multiple MPRIS players are active)
 PREFERRED_PLAYER = os.environ.get("PREFERRED_PLAYER", "spotify")
+PLAYER_BLACKLIST = [
+    s.strip() for s in os.environ.get("PLAYER_BLACKLIST", "").split(",") if s.strip()
+]
+
+# Watch mode
+WATCH_DEBOUNCE_MS = int(os.environ.get("WATCH_DEBOUNCE_MS", "400"))
+WATCH_CALIBRATION_INTERVAL_S = float(
+    os.environ.get("WATCH_CALIBRATION_INTERVAL_S", "3.0")
+)
+WATCH_POSITION_TICK_MS = int(os.environ.get("WATCH_POSITION_TICK_MS", "50"))
+WATCH_SOCKET_PATH = Path(CACHE_DIR) / "watch.sock"
 
 
 class _Credentials:

src/lrx_cli/watch/__init__.py

@@ -0,0 +1,5 @@
+"""Watch subsystem public exports."""
+
+from .session import WatchCoordinator
+
+__all__ = ["WatchCoordinator"]

src/lrx_cli/watch/control.py

@@ -0,0 +1,172 @@
+"""Unix-socket control channel for communicating with a running watch session."""
+
+import asyncio
+import json
+from pathlib import Path
+from typing import Protocol, TypeAlias
+
+from loguru import logger
+
+from .options import WatchOptions
+
+
+JSONPrimitive: TypeAlias = str | int | float | bool | None
+JSONValue: TypeAlias = JSONPrimitive | dict[str, "JSONValue"] | list["JSONValue"]
+JSONDict: TypeAlias = dict[str, JSONValue]
+
+
+class ControlSession(Protocol):
+    """Session protocol used by control channel handlers."""
+
+    def handle_offset(self, delta: int) -> JSONDict:
+        """Apply offset delta and return JSON response payload."""
+        ...
+
+    def handle_status(self) -> JSONDict:
+        """Return current session status payload."""
+        ...
+
+
+class ControlServer:
+    """Control server that handles offset/status commands over a Unix socket."""
+
+    _options: WatchOptions
+    _socket_path: Path
+    _server: asyncio.AbstractServer | None
+
+    def __init__(
+        self,
+        options: WatchOptions,
+        socket_path: Path | None = None,
+    ) -> None:
+        """Initialize control server with explicit socket path or runtime options."""
+        self._options = options
+        resolved_socket_path = socket_path or self._options.socket_path
+        self._socket_path: Path = resolved_socket_path
+        self._server: asyncio.AbstractServer | None = None
+
+    async def start(self, session: ControlSession) -> bool:
+        """Start listening for control requests and bind session handlers."""
+        if not await self._prepare_socket_path():
+            return False
+
+        self._socket_path.parent.mkdir(parents=True, exist_ok=True)
+        self._server = await asyncio.start_unix_server(
+            lambda r, w: self._handle(session, r, w),
+            path=str(self._socket_path),
+        )
+        return True
+
+    async def _prepare_socket_path(self) -> bool:
+        """Ensure socket path is usable and reject when another session is active."""
+        if not self._socket_path.exists():
+            return True
+
+        try:
+            reader, writer = await asyncio.open_unix_connection(str(self._socket_path))
+            writer.close()
+            await writer.wait_closed()
+            logger.error(
+                "A watch session is already running. Use 'lrx watch ctl status'."
+            )
+            return False
+        except Exception:
+            try:
+                self._socket_path.unlink(missing_ok=True)
+            except Exception:
+                pass
+            return True
+
+    async def stop(self) -> None:
+        """Stop control server and remove stale socket path."""
+        if self._server is not None:
+            self._server.close()
+            await self._server.wait_closed()
+            self._server = None
+        try:
+            self._socket_path.unlink(missing_ok=True)
+        except Exception:
+            pass
+
+    async def _handle(
+        self,
+        session: ControlSession,
+        reader: asyncio.StreamReader,
+        writer: asyncio.StreamWriter,
+    ) -> None:
+        """Handle one control request and send JSON response."""
+        resp: JSONDict = {"ok": False, "error": "internal error"}
+        try:
+            line = await reader.readline()
+            if not line:
+                resp = {"ok": False, "error": "empty request"}
+            else:
+                req = json.loads(line.decode("utf-8"))
+                cmd = req.get("cmd")
+                if cmd == "offset":
+                    delta = int(req.get("delta", 0))
+                    resp = session.handle_offset(delta)
+                elif cmd == "status":
+                    resp = session.handle_status()
+                else:
+                    resp = {"ok": False, "error": "unknown command"}
+        except Exception as e:
+            resp = {"ok": False, "error": str(e)}
+        finally:
+            writer.write((json.dumps(resp) + "\n").encode("utf-8"))
+            await writer.drain()
+            writer.close()
+            await writer.wait_closed()
+
+
+class ControlClient:
+    """Control client used by CLI commands to talk to active watch session."""
+
+    _options: WatchOptions
+    _socket_path: Path
+
+    def __init__(
+        self,
+        options: WatchOptions,
+        socket_path: Path | None = None,
+    ) -> None:
+        """Initialize control client with explicit socket path or runtime options."""
+        self._options = options
+        resolved_socket_path = socket_path or self._options.socket_path
+        self._socket_path: Path = resolved_socket_path
+
+    async def _send_async(self, cmd: JSONDict) -> JSONDict:
+        """Send one JSON command to control server and return JSON response."""
+        if not self._socket_path.exists():
+            return {"ok": False, "error": "No watch session running."}
+
+        try:
+            reader, writer = await asyncio.open_unix_connection(str(self._socket_path))
+        except Exception:
+            return {"ok": False, "error": "No watch session running."}
+
+        writer.write((json.dumps(cmd) + "\n").encode("utf-8"))
+        await writer.drain()
+        line = await reader.readline()
+        writer.close()
+        await writer.wait_closed()
+        if not line:
+            return {"ok": False, "error": "Empty response."}
+        return json.loads(line.decode("utf-8"))
+
+    def send(self, cmd: JSONDict) -> JSONDict:
+        """Synchronous wrapper around async control request."""
+        return asyncio.run(self._send_async(cmd))
+
+
+def parse_delta(raw: str) -> tuple[bool, int | None, str | None]:
+    """Parse signed millisecond offset delta string for ctl offset command."""
+    value = raw.strip()
+    try:
+        if value.startswith("+"):
+            return True, int(value[1:]), None
+        if value.startswith("-"):
+            return True, -int(value[1:]), None
+        return True, int(value), None
+    except ValueError:
+        return False, None, f"Invalid offset delta: {raw}"

src/lrx_cli/watch/fetcher.py

@@ -0,0 +1,80 @@
+"""Debounced lyric fetch orchestration for watch session."""
+
+import asyncio
+from typing import Awaitable, Callable, Optional
+
+from ..lrc import LRCData
+from ..models import TrackMeta
+from .options import WatchOptions
+
+
+class LyricFetcher:
+    """Debounces track updates and runs at most one lyric fetch task at a time."""
+
+    _options: WatchOptions
+    _fetch_func: Callable[[TrackMeta], Awaitable[Optional[LRCData]]]
+    _on_fetching: Callable[[], Awaitable[None] | None]
+    _on_result: Callable[[Optional[LRCData]], Awaitable[None] | None]
+    _debounce_task: asyncio.Task | None
+    _fetch_task: asyncio.Task | None
+    _pending_track: TrackMeta | None
+
+    def __init__(
+        self,
+        fetch_func: Callable[[TrackMeta], Awaitable[Optional[LRCData]]],
+        on_fetching: Callable[[], Awaitable[None] | None],
+        on_result: Callable[[Optional[LRCData]], Awaitable[None] | None],
+        options: WatchOptions,
+    ) -> None:
+        """Initialize fetch callbacks and runtime options."""
+        self._options = options
+        self._fetch_func = fetch_func
+        self._on_fetching = on_fetching
+        self._on_result = on_result
+        self._debounce_task: asyncio.Task | None = None
+        self._fetch_task: asyncio.Task | None = None
+        self._pending_track: TrackMeta | None = None
+
+    async def stop(self) -> None:
+        """Cancel and await all in-flight debounce/fetch tasks."""
+        for task in (self._debounce_task, self._fetch_task):
+            if task is not None:
+                task.cancel()
+        await asyncio.gather(
+            *[t for t in (self._debounce_task, self._fetch_task) if t is not None],
+            return_exceptions=True,
+        )
+        self._debounce_task = None
+        self._fetch_task = None
+
+    def request(self, track: TrackMeta) -> None:
+        """Request lyrics for track with debounce collapsing."""
+        self._pending_track = track
+        if self._debounce_task is not None:
+            self._debounce_task.cancel()
+        self._debounce_task = asyncio.create_task(self._debounce_then_fetch())
+
+    async def _debounce_then_fetch(self) -> None:
+        """Wait debounce window then start a fresh fetch task for latest pending track."""
+        await asyncio.sleep(self._options.debounce_ms / 1000.0)
+        track = self._pending_track
+        if track is None:
+            return
+
+        if self._fetch_task is not None:
+            self._fetch_task.cancel()
+            await asyncio.gather(self._fetch_task, return_exceptions=True)
+
+        self._fetch_task = asyncio.create_task(self._do_fetch(track))
+
+    async def _do_fetch(self, track: TrackMeta) -> None:
+        """Execute fetch lifecycle callbacks and fetch lyrics for a track."""
+        fetching_callback_result = self._on_fetching()
+        if asyncio.iscoroutine(fetching_callback_result):
+            await fetching_callback_result
+
+        lyrics = await self._fetch_func(track)
+
+        result_callback_result = self._on_result(lyrics)
+        if asyncio.iscoroutine(result_callback_result):
+            await result_callback_result

src/lrx_cli/watch/options.py

@@ -0,0 +1,16 @@
+"""Watch runtime options passed from CLI composition root."""
+
+from dataclasses import dataclass
+from pathlib import Path
+
+
+@dataclass(frozen=True)
+class WatchOptions:
+    """Runtime settings used by watch components."""
+
+    preferred_player: str
+    player_blacklist: tuple[str, ...]
+    debounce_ms: int
+    position_tick_ms: int
+    calibration_interval_s: float
+    socket_path: Path

src/lrx_cli/watch/player.py

@@ -0,0 +1,411 @@
+"""Player discovery, state monitoring, and active-player selection for watch mode."""
+
+from dataclasses import dataclass
+from typing import Callable, Optional
+import asyncio
+
+from dbus_next.aio.message_bus import MessageBus
+from dbus_next.constants import BusType
+from dbus_next.message import Message
+from loguru import logger
+
+from ..models import TrackMeta
+from .options import WatchOptions
+
+
+def _variant_value(item: object) -> object | None:
+    """Extract .value from DBus variant-like objects when available."""
+    if hasattr(item, "value"):
+        return getattr(item, "value")
+    return None
+
+
+@dataclass(slots=True)
+class PlayerState:
+    """Current observable state for one MPRIS player."""
+
+    bus_name: str
+    status: str
+    track: Optional[TrackMeta]
+
+
+@dataclass(frozen=True, slots=True)
+class PlayerTarget:
+    """Constraint for choosing which players are visible to watch."""
+
+    hint: Optional[str] = None
+    player_blacklist: tuple[str, ...] = ()
+
+    def validation_error(self) -> str | None:
+        """Return validation message when hint conflicts with blacklist, else None."""
+        normalized_hint = self.normalized_hint
+        if not normalized_hint:
+            return None
+        for blocked in self.player_blacklist:
+            normalized_blocked = blocked.strip().lower()
+            if not normalized_blocked:
+                continue
+            if _keyword_match(normalized_hint, normalized_blocked) or _keyword_match(
+                normalized_blocked, normalized_hint
+            ):
+                return (
+                    f"Requested player '{self.hint}' is blocked by "
+                    f"PLAYER_BLACKLIST entry '{blocked}'."
+                )
+        return None
+
+    @property
+    def normalized_hint(self) -> str:
+        """Return normalized lowercase player hint string."""
+        return (self.hint or "").strip().lower()
+
+    def allows(self, bus_name: str) -> bool:
+        """Return whether given MPRIS bus name passes this target constraint."""
+        normalized_hint = self.normalized_hint
+        if not normalized_hint:
+            return True
+        return _keyword_match(bus_name, normalized_hint)
+
+
+def _keyword_match(text: str, keyword: str) -> bool:
+    """Return True when keyword exists in text, case-insensitively."""
+    return keyword.strip().lower() in text.lower()
+
+
+class PlayerMonitor:
+    """Tracks MPRIS players and forwards signal-driven state updates to session callbacks."""
+
+    _options: WatchOptions
+    _on_players_changed: Callable[[], None]
+    _on_seeked: Callable[[str, int], None]
+    _on_playback_status: Callable[[str, str], None]
+    _target: PlayerTarget
+    players: dict[str, PlayerState]
+    _bus: MessageBus | None
+    _props_cache: dict[str, object]
+
+    def __init__(
+        self,
+        on_players_changed: Callable[[], None],
+        on_seeked: Callable[[str, int], None],
+        on_playback_status: Callable[[str, str], None],
+        options: WatchOptions,
+        target: Optional[PlayerTarget] = None,
+    ) -> None:
+        """Initialize monitor callbacks, runtime options, and player target filter."""
+        self._options = options
+        self._on_players_changed = on_players_changed
+        self._on_seeked = on_seeked
+        self._on_playback_status = on_playback_status
+        self._target = target or PlayerTarget(
+            player_blacklist=self._options.player_blacklist
+        )
+        self.players: dict[str, PlayerState] = {}
+        self._bus: MessageBus | None = None
+        self._props_cache: dict[str, object] = {}
+
+    async def start(self) -> None:
+        """Start DBus monitoring and populate initial player snapshot."""
+        self._bus = await MessageBus(bus_type=BusType.SESSION).connect()
+        self._bus.add_message_handler(self._on_message)
+        await self._add_match_rules()
+        await self.refresh()
+
+    async def close(self) -> None:
+        """Stop DBus monitoring and close bus connection."""
+        self._props_cache.clear()
+        if self._bus:
+            self._bus.disconnect()
+            self._bus = None
+
+    async def _get_player_props(self, bus_name: str) -> object | None:
+        """Return cached DBus Properties interface for player, creating it if missing."""
+        if not self._bus:
+            return None
+        if bus_name in self._props_cache:
+            return self._props_cache[bus_name]
+
+        try:
+            introspection = await self._bus.introspect(
+                bus_name, "/org/mpris/MediaPlayer2"
+            )
+            proxy = self._bus.get_proxy_object(
+                bus_name, "/org/mpris/MediaPlayer2", introspection
+            )
+            props = proxy.get_interface("org.freedesktop.DBus.Properties")
+            self._props_cache[bus_name] = props
+            return props
+        except Exception as e:
+            logger.debug(f"Failed to prepare DBus props for {bus_name}: {e}")
+            self._props_cache.pop(bus_name, None)
+            return None
+
+    async def _add_match_rules(self) -> None:
+        """Register signal subscriptions needed by monitor."""
+        if not self._bus:
+            return
+        rules = [
+            "type='signal',interface='org.freedesktop.DBus',member='NameOwnerChanged'",
+            "type='signal',interface='org.freedesktop.DBus.Properties',member='PropertiesChanged'",
+            "type='signal',interface='org.mpris.MediaPlayer2.Player',member='Seeked'",
+        ]
+        for rule in rules:
+            try:
+                await self._bus.call(
+                    Message(
+                        destination="org.freedesktop.DBus",
+                        path="/org/freedesktop/DBus",
+                        interface="org.freedesktop.DBus",
+                        member="AddMatch",
+                        signature="s",
+                        body=[rule],
+                    )
+                )
+            except Exception as e:
+                logger.debug(f"Failed to add DBus match rule {rule}: {e}")
+
+    async def _list_mpris_players(self) -> list[str]:
+        """List visible MPRIS players after applying blacklist and target filter."""
+        if not self._bus:
+            return []
+        try:
+            reply = await self._bus.call(
+                Message(
+                    destination="org.freedesktop.DBus",
+                    path="/org/freedesktop/DBus",
+                    interface="org.freedesktop.DBus",
+                    member="ListNames",
+                )
+            )
+            if not reply or not reply.body:
+                return []
+            out: list[str] = []
+            for name in reply.body[0]:
+                if not name.startswith("org.mpris.MediaPlayer2."):
+                    continue
+                if any(
+                    x.lower() in name.lower() for x in self._options.player_blacklist
+                ):
+                    continue
+                if not self._target.allows(name):
+                    continue
+                out.append(name)
+            return out
+        except Exception as e:
+            logger.debug(f"Failed to list mpris players: {e}")
+            return []
+
+    async def _fetch_player_state(self, bus_name: str) -> Optional[PlayerState]:
+        """Read current playback status and metadata from one player service."""
+        props = await self._get_player_props(bus_name)
+        if props is None:
+            return None
+        try:
+            status_var = await getattr(props, "call_get")(
+                "org.mpris.MediaPlayer2.Player", "PlaybackStatus"
+            )
+            metadata_var = await getattr(props, "call_get")(
+                "org.mpris.MediaPlayer2.Player", "Metadata"
+            )
+            status = status_var.value if status_var else "Stopped"
+            track = self._track_from_metadata(
+                metadata_var.value if metadata_var else {}
+            )
+            return PlayerState(bus_name=bus_name, status=status, track=track)
+        except Exception as e:
+            logger.debug(f"Failed to read state for {bus_name}: {e}")
+            self._props_cache.pop(bus_name, None)
+            return None
+
+    def _track_from_metadata(self, metadata: dict[str, object]) -> Optional[TrackMeta]:
+        """Build TrackMeta object from MPRIS metadata map."""
+        if not metadata:
+            return None
+        trackid = metadata.get("mpris:trackid")
+        if trackid is not None:
+            trackid = _variant_value(trackid)
+            if isinstance(trackid, str) and trackid.startswith("spotify:track:"):
+                trackid = trackid.removeprefix("spotify:track:")
+            elif isinstance(trackid, str) and trackid.startswith("/com/spotify/track/"):
+                trackid = trackid.removeprefix("/com/spotify/track/")
+            elif not isinstance(trackid, str):
+                trackid = None
+
+        length = metadata.get("mpris:length")
+        length_ms = None
+        length_value = _variant_value(length) if length is not None else None
+        if isinstance(length_value, int):
+            length_ms = length_value // 1000
+
+        artist = metadata.get("xesam:artist")
+        artist_v = None
+        artist_value = _variant_value(artist) if artist is not None else None
+        if isinstance(artist_value, list) and artist_value:
+            artist_v = artist_value[0]
+
+        title = metadata.get("xesam:title")
+        album = metadata.get("xesam:album")
+        url = metadata.get("xesam:url")
+
+        title_value = _variant_value(title) if title is not None else None
+        album_value = _variant_value(album) if album is not None else None
+        url_value = _variant_value(url) if url is not None else None
+
+        return TrackMeta(
+            trackid=trackid,
+            length=length_ms,
+            album=album_value if isinstance(album_value, str) else None,
+            artist=artist_v,
+            title=title_value if isinstance(title_value, str) else None,
+            url=url_value if isinstance(url_value, str) else None,
+        )
+
+    async def refresh(self) -> None:
+        """Refresh full player snapshot and notify session when visible set changes."""
+        players = await self._list_mpris_players()
+        updated: dict[str, PlayerState] = {}
+        for bus_name in players:
+            st = await self._fetch_player_state(bus_name)
+            if st is not None:
+                updated[bus_name] = st
+
+        before = set(self.players.keys())
+        after = set(updated.keys())
+        added = sorted(after - before)
+        removed = sorted(before - after)
+
+        for bus_name in removed:
+            self._props_cache.pop(bus_name, None)
+
+        self.players = updated
+
+        if added or removed:
+            logger.info(
+                "MPRIS players updated: added={}, removed={}",
+                added,
+                removed,
+            )
+
+        self._on_players_changed()
+
+    async def _resolve_well_known_name(self, unique_sender: str) -> str | None:
+        """Map a DBus unique sender (e.g. :1.42) to a tracked MPRIS bus name."""
+        if unique_sender in self.players:
+            return unique_sender
+        if not self._bus:
+            return None
+
+        for bus_name in self.players:
+            try:
+                reply = await self._bus.call(
+                    Message(
+                        destination="org.freedesktop.DBus",
+                        path="/org/freedesktop/DBus",
+                        interface="org.freedesktop.DBus",
+                        member="GetNameOwner",
+                        signature="s",
+                        body=[bus_name],
+                    )
+                )
+                if reply and reply.body and str(reply.body[0]) == unique_sender:
+                    return bus_name
+            except Exception:
+                continue
+        return None
+
+    async def _handle_seeked_signal(self, sender: str, position_ms: int) -> None:
+        """Route Seeked signal to session using well-known bus name when possible."""
+        bus_name = await self._resolve_well_known_name(sender)
+        if bus_name is not None:
+            self._on_seeked(bus_name, position_ms)
+            return
+
+        # If we cannot map sender reliably, force a state refresh to converge.
+        await self.refresh()
+
+    def _on_message(self, message: Message) -> bool:
+        """Low-level DBus signal handler for player lifecycle/status/seek events."""
+        try:
+            if (
+                message.interface == "org.freedesktop.DBus"
+                and message.member == "NameOwnerChanged"
+            ):
+                if message.body and str(message.body[0]).startswith(
+                    "org.mpris.MediaPlayer2."
+                ):
+                    asyncio.create_task(self.refresh())
+                return False
+
+            if (
+                message.interface == "org.freedesktop.DBus.Properties"
+                and message.member == "PropertiesChanged"
+            ):
+                # Message.sender is a DBus unique name, so match by path+iface.
+                path_ok = message.path == "/org/mpris/MediaPlayer2"
+                iface = message.body[0] if message.body else None
+                if path_ok and iface == "org.mpris.MediaPlayer2.Player":
+                    asyncio.create_task(self.refresh())
+                return False
+
+            if (
+                message.interface == "org.mpris.MediaPlayer2.Player"
+                and message.member == "Seeked"
+            ):
+                sender = message.sender or ""
+                if sender and message.body:
+                    position_us = int(message.body[0])
+                    asyncio.create_task(
+                        self._handle_seeked_signal(
+                            sender,
+                            max(0, position_us // 1000),
+                        )
+                    )
+                return False
+        except Exception as e:
+            logger.debug(f"PlayerMonitor signal handling error: {e}")
+        return False
+
+    async def get_position_ms(self, bus_name: str) -> Optional[int]:
+        """Read player-reported position in milliseconds."""
+        props = await self._get_player_props(bus_name)
+        if props is None:
+            return None
+        try:
+            position_var = await getattr(props, "call_get")(
+                "org.mpris.MediaPlayer2.Player", "Position"
+            )
+            if position_var is None:
+                return None
+            return max(0, int(position_var.value) // 1000)
+        except Exception as e:
+            logger.debug(f"Failed to read position from {bus_name}: {e}")
+            self._props_cache.pop(bus_name, None)
+            return None
+
+
+class ActivePlayerSelector:
+    @staticmethod
+    def select(
+        players: dict[str, PlayerState],
+        last_active: str | None,
+        options: WatchOptions,
+    ) -> str | None:
+        """Select active player by playing state, preferred keyword, and continuity."""
+        if not players:
+            return None
+
+        playing = [name for name, st in players.items() if st.status == "Playing"]
+        if len(playing) == 1:
+            return playing[0]
+
+        preferred = options.preferred_player.lower().strip()
+        candidates = playing if playing else list(players.keys())
+        if preferred:
+            for name in candidates:
+                if preferred in name.lower():
+                    return name
+
+        if last_active and last_active in players:
+            return last_active
+
+        return candidates[0] if candidates else None

src/lrx_cli/watch/session.py

@@ -0,0 +1,403 @@
+"""Watch orchestration with explicit MVVM role boundaries.
+
+- Model: WatchModel stores domain state.
+- ViewModel: WatchViewModel projects model to output-facing state/signature.
+- Coordinator: WatchCoordinator wires services and drives async workflows.
+"""
+
+import asyncio
+from dataclasses import asdict
+from typing import Optional, Protocol
+
+from loguru import logger
+
+from ..fetchers import FetcherMethodType
+from ..lrc import LRCData
+from ..models import LyricResult
+from ..models import TrackMeta
+from .control import ControlServer
+from .fetcher import LyricFetcher
+from .options import WatchOptions
+from .view import BaseOutput, LyricView, WatchState
+from .player import ActivePlayerSelector, PlayerMonitor, PlayerTarget
+from .tracker import PositionTracker
+
+
+class FetchManager(Protocol):
+    """Protocol for lyric fetch manager consumed by watch session."""
+
+    def fetch_for_track(
+        self,
+        track: TrackMeta,
+        force_method: FetcherMethodType | None = None,
+        bypass_cache: bool = False,
+        allow_unsynced: bool = False,
+    ) -> Optional[LyricResult]:
+        """Fetch lyrics for one track."""
+
+
+class WatchModel:
+    """Model layer that owns watch state and lyric timeline representation."""
+
+    offset_ms: int
+    active_player: str | None
+    active_track_key: str | None
+    status: str
+    lyrics: LyricView | None
+
+    def __init__(self) -> None:
+        self.offset_ms = 0
+        self.active_player: str | None = None
+        self.active_track_key: str | None = None
+        self.status: str = "idle"
+        self.lyrics: LyricView | None = None
+
+    def set_lyrics(self, lyrics: LRCData | None) -> None:
+        """Update lyrics and rebuild projection once per lyric object change."""
+        if lyrics is None:
+            self.lyrics = None
+            return
+
+        self.lyrics = LyricView.from_lrc(lyrics)
+
+    def state_signature(self, track: TrackMeta | None, position_ms: int) -> tuple:
+        """Build dedupe signature from model state and current lyric cursor."""
+        track_key = (
+            track.trackid
+            if track and track.trackid
+            else track.display_name()
+            if track
+            else None
+        )
+
+        if self.status != "ok" or self.lyrics is None:
+            return ("status", self.status, self.active_player, track_key)
+        at_ms = position_ms + self.offset_ms
+        cursor = self.lyrics.signature_cursor(at_ms)
+        return ("lyrics", self.active_player, track_key, cursor)
+
+
+class WatchViewModel:
+    """ViewModel that projects WatchModel into view-consumable snapshots."""
+
+    _model: WatchModel
+
+    def __init__(self, model: WatchModel) -> None:
+        self._model = model
+
+    def signature(self, track: TrackMeta | None, position_ms: int) -> tuple:
+        """Build dedupe signature for current projected state."""
+        return self._model.state_signature(track, position_ms)
+
+    def state(self, track: TrackMeta | None, position_ms: int) -> WatchState:
+        """Project model values into immutable WatchState payload."""
+        return WatchState(
+            track=track,
+            lyrics=self._model.lyrics,
+            position_ms=position_ms,
+            offset_ms=self._model.offset_ms,
+            status=self._model.status,  # type: ignore[arg-type]
+        )
+
+
+class WatchCoordinator:
+    """Application/service orchestration layer for watch runtime."""
+
+    _manager: FetchManager
+    _output: BaseOutput
+    _options: WatchOptions
+    _model: WatchModel
+    _view_model: WatchViewModel
+    _player_hint: str | None
+    _last_emit_signature: tuple | None
+    _target: PlayerTarget
+    _control: ControlServer
+    _player_monitor: PlayerMonitor
+    _tracker: PositionTracker
+    _fetcher: LyricFetcher
+    _emit_scheduled: bool
+    _calibration_task: asyncio.Task | None
+
+    def __init__(
+        self,
+        manager: FetchManager,
+        output: BaseOutput,
+        player_hint: str | None,
+        options: WatchOptions,
+    ) -> None:
+        self._manager = manager
+        self._output = output
+        self._options = options
+        self._model = WatchModel()
+        self._view_model = WatchViewModel(self._model)
+        self._player_hint = player_hint
+        self._last_emit_signature: tuple | None = None
+        self._emit_scheduled = False
+        self._calibration_task = None
+
+        self._target = PlayerTarget(
+            hint=player_hint,
+            player_blacklist=self._options.player_blacklist,
+        )
+
+        self._control = ControlServer(options=self._options)
+        self._player_monitor = PlayerMonitor(
+            on_players_changed=self._on_player_change,
+            on_seeked=self._on_seeked,
+            on_playback_status=self._on_playback_status,
+            options=self._options,
+            target=self._target,
+        )
+        self._tracker = PositionTracker(
+            poll_position_ms=self._player_monitor.get_position_ms,
+            options=self._options,
+            on_tick=self._on_tracker_tick,
+        )
+        self._fetcher = LyricFetcher(
+            fetch_func=self._fetch_lyrics,
+            on_fetching=self._on_fetching,
+            on_result=self._on_lyrics_update,
+            options=self._options,
+        )
+
+    async def run(self) -> bool:
+        """Run watch workflow and return success flag."""
+        target_issue = self._target.validation_error()
+        if target_issue:
+            logger.error(target_issue)
+            return False
+
+        logger.info(
+            "watch session starting (player filter: {})",
+            self._player_hint or "<none>",
+        )
+
+        if not await self._control.start(self):
+            return False
+        try:
+            await self._player_monitor.start()
+            await self._tracker.start()
+            self._calibration_task = asyncio.create_task(self._calibration_loop())
+            self._schedule_emit()
+            await asyncio.Event().wait()
+            return True
+        except asyncio.CancelledError:
+            return True
+        except Exception as exc:
+            logger.exception("watch runtime error: {}", exc)
+            return False
+        finally:
+            logger.info("watch session stopping")
+            if self._calibration_task is not None:
+                self._calibration_task.cancel()
+                await asyncio.gather(self._calibration_task, return_exceptions=True)
+                self._calibration_task = None
+            await self._fetcher.stop()
+            await self._tracker.stop()
+            await self._player_monitor.close()
+            await self._control.stop()
+
+    async def _calibration_loop(self) -> None:
+        """Periodically refresh full MPRIS snapshot as fallback calibration."""
+        interval = max(0.1, self._options.calibration_interval_s)
+        while True:
+            await asyncio.sleep(interval)
+            try:
+                await self._player_monitor.refresh()
+            except asyncio.CancelledError:
+                raise
+            except Exception as exc:
+                logger.debug("mpris calibration refresh failed: {}", exc)
+
+    def _active_track(self) -> TrackMeta | None:
+        """Return active track metadata from selected player."""
+        player = self._player_monitor.players.get(self._model.active_player or "")
+        return player.track if player else None
+
+    def _request_fetch_for_active_track(self, reason: str) -> bool:
+        """Trigger lyric fetch for active track when needed."""
+        track = self._active_track()
+        if track is None:
+            return False
+        if self._model.lyrics is not None:
+            return False
+        if self._model.status == "fetching":
+            return False
+        logger.info("fetching lyrics for track ({}): {}", reason, track.display_name())
+        self._fetcher.request(track)
+        return True
+
+    async def _fetch_lyrics(self, track: TrackMeta) -> Optional[LRCData]:
+        """Fetch lyrics in worker thread."""
+        result = await asyncio.to_thread(
+            self._manager.fetch_for_track,
+            track,
+            None,
+            False,
+            True,
+        )
+        if result and result.lyrics:
+            return result.lyrics
+        return None
+
+    def _on_player_change(self) -> None:
+        """React to monitor player snapshot change."""
+        prev_player = self._model.active_player
+        prev_track_key = self._model.active_track_key
+
+        selected = ActivePlayerSelector.select(
+            self._player_monitor.players,
+            self._model.active_player,
+            self._options,
+        )
+        self._model.active_player = selected
+
+        if selected != prev_player:
+            logger.info(
+                "active player changed: {} -> {}",
+                prev_player or "<none>",
+                selected or "<none>",
+            )
+
+        if selected is None:
+            self._model.status = "idle"
+            self._model.active_track_key = None
+            self._model.set_lyrics(None)
+            self._schedule_emit()
+            return
+
+        state = self._player_monitor.players.get(selected)
+        if state is None:
+            self._model.status = "idle"
+            self._model.active_track_key = None
+            self._model.set_lyrics(None)
+            self._schedule_emit()
+            return
+
+        track = state.track
+        track_key = (
+            track.trackid
+            if track and track.trackid
+            else track.display_name()
+            if track
+            else None
+        )
+
+        track_changed = track_key != prev_track_key
+        player_changed = selected != prev_player
+        if track_changed or player_changed:
+            self._model.set_lyrics(None)
+
+        self._model.active_track_key = track_key
+
+        asyncio.create_task(
+            self._tracker.set_active_player(
+                selected,
+                state.status,
+                track_key,
+            )
+        )
+
+        if state.status != "Playing":
+            self._model.status = "paused"
+            self._schedule_emit()
+            return
+
+        started_fetch = False
+        if track is not None and (
+            player_changed or track_changed or self._model.lyrics is None
+        ):
+            started_fetch = self._request_fetch_for_active_track("track-changed")
+
+        if self._model.lyrics is not None:
+            self._model.status = "ok"
+        elif started_fetch:
+            self._model.status = "fetching"
+        else:
+            self._model.status = "paused"
+        self._schedule_emit()
+
+    def _on_seeked(self, bus_name: str, position_ms: int) -> None:
+        """Forward seek event to tracker."""
+        asyncio.create_task(self._tracker.on_seeked(bus_name, position_ms))
+
+    def _on_playback_status(self, bus_name: str, status: str) -> None:
+        """React to playback status change and tracker sync."""
+        if bus_name == self._model.active_player:
+            if status == "Playing":
+                started_fetch = self._request_fetch_for_active_track("resume-playing")
+                if self._model.lyrics is not None:
+                    self._model.status = "ok"
+                elif started_fetch:
+                    self._model.status = "fetching"
+                else:
+                    self._model.status = "paused"
+            else:
+                self._model.status = "paused"
+            self._schedule_emit()
+        asyncio.create_task(self._tracker.on_playback_status(bus_name, status))
+
+    def _on_tracker_tick(self) -> None:
+        """Emit updates from tracker tick only while lyrics are actively rendering."""
+        if self._model.status == "ok":
+            self._schedule_emit()
+
+    def _schedule_emit(self) -> None:
+        """Coalesce frequent events into at most one in-flight emit task."""
+        if self._emit_scheduled:
+            return
+        self._emit_scheduled = True
+        asyncio.create_task(self._run_scheduled_emit())
+
+    async def _run_scheduled_emit(self) -> None:
+        """Run one coalesced emit and release scheduler gate."""
+        try:
+            await self._emit_state()
+        finally:
+            self._emit_scheduled = False
+
+    async def _on_fetching(self) -> None:
+        """Mark model as fetching and emit state."""
+        self._model.status = "fetching"
+        await self._emit_state()
+
+    async def _on_lyrics_update(self, lyrics: Optional[LRCData]) -> None:
+        """Update model with fetched lyrics and emit state."""
+        self._model.set_lyrics(lyrics)
+        self._model.status = "ok" if lyrics is not None else "no_lyrics"
+        logger.info(
+            "lyrics update result: {}",
+            "found" if lyrics is not None else "not found",
+        )
+        await self._emit_state()
+
+    async def _emit_state(self) -> None:
+        """Emit output state only when semantic signature changes."""
+        player = self._player_monitor.players.get(self._model.active_player or "")
+        track = player.track if player else None
+        position = await self._tracker.get_position_ms()
+
+        signature = self._view_model.signature(track, position)
+        if signature == self._last_emit_signature:
+            return
+        self._last_emit_signature = signature
+        state = self._view_model.state(track, position)
+        await self._output.on_state(state)
+
+    def handle_offset(self, delta: int) -> dict:
+        """Apply offset update requested by control channel."""
+        self._model.offset_ms += delta
+        return {"ok": True, "offset_ms": self._model.offset_ms}
+
+    def handle_status(self) -> dict:
+        """Return status payload for control channel."""
+        player = self._player_monitor.players.get(self._model.active_player or "")
+        track = asdict(player.track) if player and player.track else None
+        return {
+            "ok": True,
+            "offset_ms": self._model.offset_ms,
+            "player": self._model.active_player,
+            "track": track,
+            "position_ms": self._tracker.peek_position_ms(),
+            "lyrics_status": self._model.status,
+        }

src/lrx_cli/watch/tracker.py

@@ -0,0 +1,143 @@
+"""Playback position tracking utilities for watch mode."""
+
+import asyncio
+import time
+from typing import Awaitable, Callable, Optional
+
+from .options import WatchOptions
+
+
+class PositionTracker:
+    """Maintains an estimated playback position from seek/status events plus local clock."""
+
+    _options: WatchOptions
+    _poll_position_ms: Callable[[str], Awaitable[Optional[int]]]
+    _active_player: str | None
+    _is_playing: bool
+    _track_key: str | None
+    _position_ms: int
+    _last_tick: float
+    _fast_task: asyncio.Task | None
+    _on_tick: Callable[[], None] | None
+    _lock: asyncio.Lock
+
+    def __init__(
+        self,
+        poll_position_ms: Callable[[str], Awaitable[Optional[int]]],
+        options: WatchOptions,
+        on_tick: Callable[[], None] | None = None,
+    ) -> None:
+        """Initialize tracker with position polling callback and runtime options."""
+        self._options = options
+        self._poll_position_ms = poll_position_ms
+        self._on_tick = on_tick
+        self._active_player: str | None = None
+        self._is_playing = False
+        self._track_key: str | None = None
+        self._position_ms = 0
+        self._last_tick = time.monotonic()
+        self._fast_task: asyncio.Task | None = None
+        self._lock = asyncio.Lock()
+
+    async def start(self) -> None:
+        """Start local monotonic position ticking task."""
+        self._last_tick = time.monotonic()
+        self._fast_task = asyncio.create_task(self._fast_loop())
+
+    async def stop(self) -> None:
+        """Stop tracker tasks and await clean cancellation."""
+        tasks = [t for t in (self._fast_task,) if t is not None]
+        for task in tasks:
+            task.cancel()
+        if tasks:
+            await asyncio.gather(*tasks, return_exceptions=True)
+        self._fast_task = None
+
+    async def set_active_player(
+        self,
+        bus_name: str | None,
+        playback_status: str,
+        track_key: str | None,
+    ) -> None:
+        """Switch active source and calibrate position once when entering a new playing track."""
+        should_calibrate_now = False
+        async with self._lock:
+            player_changed = self._active_player != bus_name
+            track_changed = self._track_key != track_key
+            was_playing = self._is_playing
+            self._active_player = bus_name
+            self._is_playing = playback_status == "Playing"
+            status_changed_to_playing = self._is_playing and not was_playing
+            if player_changed or track_changed:
+                self._position_ms = 0
+            should_calibrate_now = (
+                self._is_playing
+                and bool(self._active_player)
+                and (player_changed or track_changed or status_changed_to_playing)
+            )
+            self._track_key = track_key
+            self._last_tick = time.monotonic()
+
+        if should_calibrate_now and self._active_player:
+            await self._calibrate_once(self._active_player)
+
+    async def on_seeked(self, bus_name: str, position_ms: int) -> None:
+        """Apply explicit seek position update for active player."""
+        async with self._lock:
+            if bus_name != self._active_player:
+                return
+            self._position_ms = max(0, position_ms)
+            self._last_tick = time.monotonic()
+
+    async def on_playback_status(self, bus_name: str, playback_status: str) -> None:
+        """Update playing state and calibrate once on paused-to-playing transition."""
+        should_calibrate_now = False
+        async with self._lock:
+            if bus_name != self._active_player:
+                return
+            was_playing = self._is_playing
+            self._is_playing = playback_status == "Playing"
+            should_calibrate_now = self._is_playing and not was_playing
+            self._last_tick = time.monotonic()
+
+        if should_calibrate_now:
+            await self._calibrate_once(bus_name)
+
+    async def _fast_loop(self) -> None:
+        """Advance position by monotonic clock while active player is playing."""
+        interval = self._options.position_tick_ms / 1000.0
+        while True:
+            await asyncio.sleep(interval)
+            should_notify = False
+            async with self._lock:
+                now = time.monotonic()
+                if self._is_playing and self._active_player:
+                    delta_ms = int((now - self._last_tick) * 1000)
+                    if delta_ms > 0:
+                        self._position_ms += delta_ms
+                        should_notify = True
+                self._last_tick = now
+
+            if should_notify and self._on_tick is not None:
+                self._on_tick()
+
+    async def _calibrate_once(self, bus_name: str) -> None:
+        """Poll player-reported position once and synchronize local tracker state."""
+        polled = await self._poll_position_ms(bus_name)
+        if polled is None:
+            return
+        async with self._lock:
+            if bus_name != self._active_player:
+                return
+            # Drift correction is signal-assisted; polling is fallback.
+            self._position_ms = max(0, polled)
+            self._last_tick = time.monotonic()
+
+    async def get_position_ms(self) -> int:
+        """Return current tracked position in milliseconds."""
+        async with self._lock:
+            return max(0, int(self._position_ms))
+
+    def peek_position_ms(self) -> int:
+        """Return current tracked position without awaiting lock (best-effort snapshot)."""
+        return max(0, int(self._position_ms))

src/lrx_cli/watch/view/__init__.py

@@ -0,0 +1,80 @@
+"""Output abstraction types for watch mode rendering."""
+
+from abc import ABC, abstractmethod
+from bisect import bisect_right
+from dataclasses import dataclass
+from typing import Literal, Optional
+
+from ...lrc import LRCData, LyricLine
+from ...models import TrackMeta
+
+
+@dataclass(slots=True, frozen=True)
+class LyricView:
+    """View-ready immutable lyric data projected from one normalized LRC object."""
+
+    normalized: LRCData
+    lines: tuple[str, ...]
+    timed_line_entries: tuple[tuple[int, int], ...]
+    timestamps: tuple[int, ...]
+
+    @staticmethod
+    def from_lrc(lyrics: LRCData) -> "LyricView":
+        """Build a view projection once from normalized lyrics."""
+        normalized = lyrics.normalize()
+
+        lines: list[str] = []
+        entries: list[tuple[int, int]] = []
+
+        line_index = 0
+        for line in normalized.lines:
+            if not isinstance(line, LyricLine):
+                continue
+            text = line.text
+            lines.append(text)
+            timestamp = line.line_times_ms[0] if line.line_times_ms else 0
+            entries.append((max(0, timestamp), line_index))
+            line_index += 1
+
+        timestamps = tuple(timestamp for timestamp, _ in entries)
+        return LyricView(
+            normalized=normalized,
+            lines=tuple(lines),
+            timed_line_entries=tuple(entries),
+            timestamps=timestamps,
+        )
+
+    def signature_cursor(self, at_ms: int) -> tuple:
+        """Build a stable cursor signature for dedupe decisions."""
+        if not self.timed_line_entries:
+            return ("plain", self.lines)
+
+        first_ts = self.timed_line_entries[0][0]
+        if at_ms < first_ts:
+            return ("before_first", first_ts)
+
+        idx = bisect_right(self.timestamps, at_ms) - 1
+        if idx < 0:
+            idx = 0
+
+        ts, line_idx = self.timed_line_entries[idx]
+        text = self.lines[line_idx] if line_idx < len(self.lines) else ""
+        return ("ok", idx, ts, text)
+
+
+@dataclass(slots=True)
+class WatchState:
+    """Immutable snapshot payload delivered from session to output implementations."""
+
+    track: Optional[TrackMeta]
+    lyrics: Optional[LyricView]
+    position_ms: int
+    offset_ms: int
+    status: Literal["fetching", "ok", "no_lyrics", "paused", "idle"]
+
+
+class BaseOutput(ABC):
+    @abstractmethod
+    async def on_state(self, state: WatchState) -> None:
+        """Render or deliver one watch state frame."""
+        ...

src/lrx_cli/watch/view/pipe.py

@@ -0,0 +1,85 @@
+"""Pipe output implementation for watch mode."""
+
+from bisect import bisect_right
+from dataclasses import dataclass
+import sys
+
+from . import BaseOutput, WatchState
+
+
+@dataclass(slots=True)
+class PipeOutput(BaseOutput):
+    """Render a fixed lyric context window to stdout for streaming/pipe usage."""
+
+    before: int = 0
+    after: int = 0
+
+    def _window_size(self) -> int:
+        """Return rendered lyric window size."""
+        return self.before + 1 + self.after
+
+    def _render_status(self, message: str) -> list[str]:
+        """Render centered status line in fixed-size window."""
+        lines = [""] * self._window_size()
+        lines[self.before] = message
+        return lines
+
+    def _render_lyrics(self, state: WatchState) -> list[str]:
+        """Render context lines centered on current timed lyric entry."""
+        if state.lyrics is None:
+            return self._render_status("[no lyrics]")
+
+        all_lines = state.lyrics.lines
+        if not all_lines:
+            return self._render_status("[no lyrics]")
+        entries = state.lyrics.timed_line_entries
+
+        effective_ms = state.position_ms + state.offset_ms
+        current_line_idx: int | None
+        if entries and effective_ms < entries[0][0]:
+            # Before first timestamp, current lyric is empty and after-window shows upcoming lines.
+            current_line_idx = None
+        else:
+            if not entries:
+                current_line_idx = 0
+            else:
+                current_entry_idx = (
+                    bisect_right(state.lyrics.timestamps, effective_ms) - 1
+                )
+                if current_entry_idx < 0:
+                    current_entry_idx = 0
+                current_line_idx = entries[current_entry_idx][1]
+
+        out: list[str] = []
+        for rel in range(-self.before, self.after + 1):
+            if current_line_idx is None:
+                if rel <= 0:
+                    out.append("")
+                    continue
+                line_idx = rel - 1
+            else:
+                line_idx = current_line_idx + rel
+
+            if 0 <= line_idx < len(all_lines):
+                out.append(all_lines[line_idx])
+            else:
+                out.append("")
+
+        return out
+
+    async def on_state(self, state: WatchState) -> None:
+        """Render and flush one frame for the latest watch state."""
+        if state.status == "fetching":
+            lines = self._render_status("[fetching...]")
+        elif state.status == "no_lyrics":
+            lines = self._render_status("[no lyrics]")
+        elif state.status == "paused":
+            lines = self._render_status("[paused]")
+        elif state.status == "idle":
+            lines = self._render_status("[idle]")
+        else:
+            lines = self._render_lyrics(state)
+
+        for line in lines:
+            print(line)
+        sys.stdout.flush()

tests/test_watch.py

@@ -0,0 +1,462 @@
+from __future__ import annotations
+
+import asyncio
+from pathlib import Path
+
+from lrx_cli.lrc import LRCData
+from lrx_cli.models import TrackMeta
+from lrx_cli.watch.control import ControlClient, ControlServer, parse_delta
+from lrx_cli.watch.view import BaseOutput, LyricView, WatchState
+from lrx_cli.watch.view.pipe import PipeOutput
+from lrx_cli.watch.player import ActivePlayerSelector, PlayerState, PlayerTarget
+from lrx_cli.watch.fetcher import LyricFetcher
+from lrx_cli.watch.options import WatchOptions
+from lrx_cli.watch.tracker import PositionTracker
+from lrx_cli.watch.session import WatchCoordinator
+
+
+TEST_WATCH_OPTIONS = WatchOptions(
+    preferred_player="spotify",
+    player_blacklist=(),
+    debounce_ms=400,
+    position_tick_ms=50,
+    calibration_interval_s=3.0,
+    socket_path=Path("/tmp/lrx-watch-test.sock"),
+)
+
+
+def test_parse_delta_supports_plus_minus_and_reset() -> None:
+    assert parse_delta("+200") == (True, 200, None)
+    assert parse_delta("-150") == (True, -150, None)
+    assert parse_delta("0") == (True, 0, None)
+
+
+def test_player_target_allows_all_when_hint_empty() -> None:
+    target = PlayerTarget()
+
+    assert target.allows("org.mpris.MediaPlayer2.spotify") is True
+    assert target.allows("org.mpris.MediaPlayer2.mpd") is True
+
+
+def test_player_target_filters_by_case_insensitive_substring() -> None:
+    target = PlayerTarget("Spot")
+
+    assert target.allows("org.mpris.MediaPlayer2.spotify") is True
+    assert target.allows("org.mpris.MediaPlayer2.mpd") is False
+
+
+def test_player_target_reports_blacklisted_hint() -> None:
+    target = PlayerTarget("spot", player_blacklist=("spotify",))
+    assert target.validation_error() is not None
+
+
+def test_active_player_selector_prefers_single_playing() -> None:
+    players = {
+        "org.mpris.MediaPlayer2.foo": PlayerState(
+            bus_name="org.mpris.MediaPlayer2.foo",
+            status="Paused",
+            track=TrackMeta(title="A"),
+        ),
+        "org.mpris.MediaPlayer2.bar": PlayerState(
+            bus_name="org.mpris.MediaPlayer2.bar",
+            status="Playing",
+            track=TrackMeta(title="B"),
+        ),
+    }
+    assert (
+        ActivePlayerSelector.select(players, None, TEST_WATCH_OPTIONS)
+        == "org.mpris.MediaPlayer2.bar"
+    )
+
+
+def test_active_player_selector_uses_last_active_when_no_playing() -> None:
+    players = {
+        "org.mpris.MediaPlayer2.foo": PlayerState(
+            bus_name="org.mpris.MediaPlayer2.foo",
+            status="Paused",
+            track=TrackMeta(title="A"),
+        ),
+        "org.mpris.MediaPlayer2.bar": PlayerState(
+            bus_name="org.mpris.MediaPlayer2.bar",
+            status="Stopped",
+            track=TrackMeta(title="B"),
+        ),
+    }
+
+    assert (
+        ActivePlayerSelector.select(
+            players,
+            "org.mpris.MediaPlayer2.bar",
+            TEST_WATCH_OPTIONS,
+        )
+        == "org.mpris.MediaPlayer2.bar"
+    )
+
+
+def test_position_tracker_seeked_calibrates_immediately() -> None:
+    async def _run() -> None:
+        async def _poll(_bus: str):
+            return 1200
+
+        tracker = PositionTracker(_poll, TEST_WATCH_OPTIONS)
+        await tracker.start()
+        await tracker.set_active_player(
+            "org.mpris.MediaPlayer2.foo", "Playing", "track-A"
+        )
+        await tracker.on_seeked("org.mpris.MediaPlayer2.foo", 3500)
+        pos = await tracker.get_position_ms()
+        await tracker.stop()
+        assert pos >= 3500
+
+    asyncio.run(_run())
+
+
+def test_position_tracker_playback_status_pause_stops_fast_growth() -> None:
+    async def _run() -> None:
+        async def _poll(_bus: str):
+            return 0
+
+        tracker = PositionTracker(_poll, TEST_WATCH_OPTIONS)
+        await tracker.start()
+        await tracker.set_active_player(
+            "org.mpris.MediaPlayer2.foo", "Playing", "track-A"
+        )
+        await asyncio.sleep(0.08)
+        before = await tracker.get_position_ms()
+
+        await tracker.on_playback_status("org.mpris.MediaPlayer2.foo", "Paused")
+        await asyncio.sleep(0.08)
+        after = await tracker.get_position_ms()
+        await tracker.stop()
+
+        assert before > 0
+        assert after - before < 20
+
+    asyncio.run(_run())
+
+
+def test_position_tracker_playback_status_playing_calibrates_once() -> None:
+    async def _run() -> None:
+        async def _poll(_bus: str):
+            return 50000
+
+        tracker = PositionTracker(_poll, TEST_WATCH_OPTIONS)
+        await tracker.start()
+        await tracker.set_active_player(
+            "org.mpris.MediaPlayer2.foo", "Paused", "track-A"
+        )
+        await tracker.on_playback_status("org.mpris.MediaPlayer2.foo", "Playing")
+        pos = await tracker.get_position_ms()
+        await tracker.stop()
+
+        assert pos >= 50000
+
+    asyncio.run(_run())
+
+
+def test_position_tracker_set_active_player_playing_calibrates_on_resume() -> None:
+    async def _run() -> None:
+        async def _poll(_bus: str):
+            return 42000
+
+        tracker = PositionTracker(_poll, TEST_WATCH_OPTIONS)
+        await tracker.start()
+        await tracker.set_active_player(
+            "org.mpris.MediaPlayer2.foo", "Paused", "track-A"
+        )
+        await tracker.set_active_player(
+            "org.mpris.MediaPlayer2.foo", "Playing", "track-A"
+        )
+        pos = await tracker.get_position_ms()
+        await tracker.stop()
+
+        assert pos >= 42000
+
+    asyncio.run(_run())
+
+
+def test_control_server_and_client_roundtrip(tmp_path: Path) -> None:
+    async def _run() -> None:
+        class _Session:
+            def __init__(self):
+                self.offset = 0
+
+            def handle_offset(self, delta: int) -> dict:
+                self.offset += delta
+                return {"ok": True, "offset_ms": self.offset}
+
+            def handle_status(self) -> dict:
+                return {"ok": True, "offset_ms": self.offset, "lyrics_status": "idle"}
+
+        socket_path = tmp_path / "watch.sock"
+        server = ControlServer(socket_path=socket_path, options=TEST_WATCH_OPTIONS)
+        session = _Session()
+
+        await server.start(session)
+        client = ControlClient(socket_path=socket_path, options=TEST_WATCH_OPTIONS)
+        r1 = await client._send_async({"cmd": "offset", "delta": 200})
+        r2 = await client._send_async({"cmd": "status"})
+        await server.stop()
+
+        assert r1 == {"ok": True, "offset_ms": 200}
+        assert r2["ok"] is True
+        assert r2["offset_ms"] == 200
+
+    asyncio.run(_run())
+
+
+def test_pipe_output_prints_fixed_window_for_status(capsys) -> None:
+    output = PipeOutput(before=1, after=1)
+    state = WatchState(
+        track=None,
+        lyrics=None,
+        position_ms=0,
+        offset_ms=0,
+        status="fetching",
+    )
+
+    asyncio.run(output.on_state(state))
+
+    printed = capsys.readouterr().out
+    assert printed == "\n[fetching...]\n\n"
+
+
+def test_pipe_output_uses_context_window_for_lyrics(capsys) -> None:
+    output = PipeOutput(before=1, after=1)
+    lyrics = LRCData("[00:01.00]a\n[00:02.00]b\n[00:03.00]c")
+    state = WatchState(
+        track=TrackMeta(title="Song"),
+        lyrics=LyricView.from_lrc(lyrics),
+        position_ms=2100,
+        offset_ms=0,
+        status="ok",
+    )
+
+    asyncio.run(output.on_state(state))
+
+    printed = capsys.readouterr().out
+    assert printed == "a\nb\nc\n"
+
+
+def test_pipe_output_shows_upcoming_lines_before_first_timestamp(capsys) -> None:
+    output = PipeOutput(before=1, after=1)
+    lyrics = LRCData("[00:02.00]a\n[00:03.00]b")
+    state = WatchState(
+        track=TrackMeta(title="Song"),
+        lyrics=LyricView.from_lrc(lyrics),
+        position_ms=0,
+        offset_ms=0,
+        status="ok",
+    )
+
+    asyncio.run(output.on_state(state))
+
+    printed = capsys.readouterr().out
+    assert printed == "\n\na\n"
+
+
+def test_pipe_output_first_line_keeps_before_region_empty(capsys) -> None:
+    output = PipeOutput(before=1, after=1)
+    lyrics = LRCData("[00:01.00]a\n[00:02.00]b\n[00:03.00]c")
+    state = WatchState(
+        track=TrackMeta(title="Song"),
+        lyrics=LyricView.from_lrc(lyrics),
+        position_ms=1100,
+        offset_ms=0,
+        status="ok",
+    )
+
+    asyncio.run(output.on_state(state))
+
+    printed = capsys.readouterr().out
+    assert printed == "\na\nb\n"
+
+
+def test_pipe_output_last_line_keeps_after_region_empty(capsys) -> None:
+    output = PipeOutput(before=1, after=1)
+    lyrics = LRCData("[00:01.00]a\n[00:02.00]b\n[00:03.00]c")
+    state = WatchState(
+        track=TrackMeta(title="Song"),
+        lyrics=LyricView.from_lrc(lyrics),
+        position_ms=3100,
+        offset_ms=0,
+        status="ok",
+    )
+
+    asyncio.run(output.on_state(state))
+
+    printed = capsys.readouterr().out
+    assert printed == "b\nc\n\n"
+
+
+def test_pipe_output_repeated_text_uses_correct_timed_occurrence(capsys) -> None:
+    output = PipeOutput(before=1, after=1)
+    lyrics = LRCData("[00:01.00]A\n[00:02.00]X\n[00:03.00]B\n[00:04.00]X\n[00:05.00]C")
+    state = WatchState(
+        track=TrackMeta(title="Song"),
+        lyrics=LyricView.from_lrc(lyrics),
+        position_ms=4100,
+        offset_ms=0,
+        status="ok",
+    )
+
+    asyncio.run(output.on_state(state))
+
+    printed = capsys.readouterr().out
+    assert printed == "B\nX\nC\n"
+
+
+def test_session_fetches_on_resume_playing_without_lyrics() -> None:
+    async def _run() -> None:
+        class _Manager:
+            def fetch_for_track(self, *_args, **_kwargs):
+                return None
+
+        class _Output(BaseOutput):
+            async def on_state(self, state: WatchState) -> None:
+                return None
+
+        class _Fetcher(LyricFetcher):
+            def __init__(self):
+                async def _fetch(_track: TrackMeta):
+                    return None
+
+                async def _on_fetching() -> None:
+                    return None
+
+                async def _on_result(_lyrics) -> None:
+                    return None
+
+                super().__init__(_fetch, _on_fetching, _on_result, TEST_WATCH_OPTIONS)
+                self.requested = []
+
+            def request(self, track: TrackMeta) -> None:
+                self.requested.append(track.display_name())
+
+        session = WatchCoordinator(
+            _Manager(),
+            _Output(),
+            player_hint=None,
+            options=TEST_WATCH_OPTIONS,
+        )
+        fake_fetcher = _Fetcher()
+        session._fetcher = fake_fetcher
+        session._tracker = PositionTracker(
+            lambda _bus: asyncio.sleep(0, result=0),
+            TEST_WATCH_OPTIONS,
+        )
+
+        bus_name = "org.mpris.MediaPlayer2.spotify"
+        track = TrackMeta(title="Song", artist="Artist")
+        session._model.active_player = bus_name
+        session._player_monitor.players = {
+            bus_name: PlayerState(bus_name=bus_name, status="Playing", track=track)
+        }
+        session._model.set_lyrics(None)
+        session._model.status = "paused"
+
+        session._on_playback_status(bus_name, "Playing")
+        await asyncio.sleep(0)
+
+        assert fake_fetcher.requested == ["Artist - Song"]
+        assert session._model.status == "fetching"
+
+    asyncio.run(_run())
+
+
+def test_session_emit_state_only_when_lyric_cursor_changes() -> None:
+    async def _run() -> None:
+        class _Manager:
+            def fetch_for_track(self, *_args, **_kwargs):
+                return None
+
+        class _Output(BaseOutput):
+            def __init__(self):
+                self.count = 0
+
+            async def on_state(self, state: WatchState) -> None:
+                self.count += 1
+
+        output = _Output()
+        session = WatchCoordinator(
+            _Manager(),
+            output,
+            player_hint=None,
+            options=TEST_WATCH_OPTIONS,
+        )
+        session._tracker = PositionTracker(
+            lambda _bus: asyncio.sleep(0, result=0),
+            TEST_WATCH_OPTIONS,
+        )
+
+        bus_name = "org.mpris.MediaPlayer2.spotify"
+        track = TrackMeta(title="Song", artist="Artist")
+        session._model.active_player = bus_name
+        session._player_monitor.players = {
+            bus_name: PlayerState(bus_name=bus_name, status="Playing", track=track)
+        }
+        session._model.set_lyrics(LRCData("[00:01.00]a\n[00:03.00]b"))
+        session._model.status = "ok"
+        await session._tracker.set_active_player(
+            bus_name,
+            "Playing",
+            "Artist - Song",
+        )
+
+        await session._emit_state()
+        await session._emit_state()
+
+        await session._tracker.on_seeked(bus_name, 3200)
+        await session._emit_state()
+
+        assert output.count == 2
+
+    asyncio.run(_run())
+
+
+def test_session_emits_when_crossing_first_timestamp() -> None:
+    async def _run() -> None:
+        class _Manager:
+            def fetch_for_track(self, *_args, **_kwargs):
+                return None
+
+        class _Output(BaseOutput):
+            def __init__(self):
+                self.count = 0
+
+            async def on_state(self, state: WatchState) -> None:
+                self.count += 1
+
+        output = _Output()
+        session = WatchCoordinator(
+            _Manager(),
+            output,
+            player_hint=None,
+            options=TEST_WATCH_OPTIONS,
+        )
+        session._tracker = PositionTracker(
+            lambda _bus: asyncio.sleep(0, result=0),
+            TEST_WATCH_OPTIONS,
+        )
+
+        bus_name = "org.mpris.MediaPlayer2.spotify"
+        track = TrackMeta(title="Song", artist="Artist")
+        session._model.active_player = bus_name
+        session._player_monitor.players = {
+            bus_name: PlayerState(bus_name=bus_name, status="Playing", track=track)
+        }
+        session._model.set_lyrics(LRCData("[00:02.00]a\n[00:03.00]b"))
+        session._model.status = "ok"
+        await session._tracker.set_active_player(
+            bus_name,
+            "Playing",
+            "Artist - Song",
+        )
+
+        await session._emit_state()
+        await session._tracker.on_seeked(bus_name, 2500)
+        await session._emit_state()
+
+        assert output.count == 2
+
+    asyncio.run(_run())