fix(player): survive a flaky stream, and don't read 0:00 at EOF

Two MPV-side fixes for the same failure story — a wifi blip during
playback.

The demuxer gave up the moment a read failed and MPV raised
EndFile(ERROR), so a momentary outage killed the track outright. Enabling
ffmpeg's reconnect options handles the common case entirely below our
level, so most outages never reach the recovery path at all. Set
non-fatally: their availability varies with the libmpv/ffmpeg build, and
losing resilience is not a reason to refuse to play anything.

Separately, `time-pos` and `duration` are live properties of the *loaded*
file: at EOF MPV unloads it and both stop resolving. Reading them straight
through returned 0.0/unknown at exactly the moment end-of-file handling
needed to know where playback had reached, so the player appeared to
rewind to 0:00 as a track ended. `ObservedTime` records the last reading
seen while media was loaded and the accessors fall back to it.

src-tauri/src/player/mpv_backend.rs

@@ -2,6 +2,7 @@ use super::backend::{PlayerBackend, PlayerError};
 use super::events::{PlayerEventEmitter, PlayerStatusEvent};
 use super::media::{MediaItem, MediaSource};
 use super::state::PlayerState;
+use super::stream_end::ObservedTime;
 use crate::playback_reporting::{EventThrottler, PlaybackOperation, PlaybackReporter};
 use crate::settings::{AudioSettings, VolumeLevel, EQ_BANDS};
 use crate::utils::conversions::{seconds_to_ticks, volume_to_percent};
@@ -26,6 +27,13 @@ pub struct MpvBackend {
     playback_reporter: Arc<TokioMutex<Option<PlaybackReporter>>>,
     position_throttler: Arc<EventThrottler>,
     last_seek_time: Arc<AtomicU64>,
+    /// Last position/duration seen while a file was loaded.
+    ///
+    /// `time-pos` and `duration` are live properties of the *loaded* file: at
+    /// EOF MPV unloads it and both stop resolving, so reading them straight
+    /// through reported 0.0 / unknown exactly when end-of-file handling needed to
+    /// know where playback reached. See [`ObservedTime`].
+    observed: Arc<Mutex<ObservedTime>>,
 }
 
 struct InternalState {
@@ -139,6 +147,31 @@ impl MpvBackend {
                 message: format!("Failed to set initial volume: {:?}", e),
             })?;
 
+        // Survive a flaky connection instead of dying on it. Without these,
+        // ffmpeg's HTTP demuxer gives up the moment a read fails and MPV raises
+        // EndFile(ERROR) — a blip on wifi kills the track outright. Reconnecting
+        // in the demuxer handles the common case entirely below our level, so
+        // most outages never reach the recovery in `player_recover_stream`.
+        //
+        // Non-fatal: these are ffmpeg-side options whose availability varies with
+        // the libmpv/ffmpeg build, and losing resilience is not a reason to
+        // refuse to play anything (graceful backend init, CLAUDE.md).
+        mpv.set_property(
+            "stream-lavf-o",
+            "reconnect=1,reconnect_streamed=1,reconnect_on_network_error=1,reconnect_delay_max=5",
+        )
+        .unwrap_or_else(|e| {
+            warn!(
+                "[MpvBackend] Could not enable stream reconnection: {:?} — \
+                 playback will not survive network interruptions",
+                e
+            );
+        });
+        mpv.set_property("network-timeout", 15i64)
+            .unwrap_or_else(|e| {
+                warn!("[MpvBackend] Could not set network timeout: {:?}", e);
+            });
+
         let state = Arc::new(Mutex::new(InternalState {
             current_media: None,
             volume: 1.0,
@@ -152,6 +185,7 @@ impl MpvBackend {
             playback_reporter,
             position_throttler,
             last_seek_time: Arc::new(AtomicU64::new(0)),
+            observed: Arc::new(Mutex::new(ObservedTime::default())),
         };
 
         // Start event loop in background thread
@@ -250,8 +284,22 @@ impl MpvBackend {
                                 debug!("[MpvBackend] Player quitting, NOT emitting PlaybackEnded");
                                 // Don't emit - player is shutting down
                             } else if reason == MPV_END_FILE_REASON_ERROR {
-                                warn!("[MpvBackend] Track ended with error, NOT emitting PlaybackEnded");
-                                // Don't emit - we should handle errors separately
+                                // NOT PlaybackEnded — the track did not finish, so
+                                // autoplay must not advance. It is an error, and it
+                                // has to be *said*: emitting nothing here left
+                                // playback halted with the UI still showing
+                                // "playing" and no way back. Marked recoverable so
+                                // the frontend echoes it into player_recover_stream,
+                                // which re-opens the stream where it stopped —
+                                // MPV's own reconnect handles shorter blips before
+                                // they ever get this far.
+                                warn!("[MpvBackend] Track ended with an error — reporting as recoverable");
+                                if let Some(emitter) = &event_emitter {
+                                    emitter.emit(PlayerStatusEvent::Error {
+                                        message: "Playback stream failed".to_string(),
+                                        recoverable: true,
+                                    });
+                                }
                             } else {
                                 debug!("[MpvBackend] Unknown end file reason {}, NOT emitting PlaybackEnded", reason);
                             }
@@ -283,6 +331,7 @@ impl MpvBackend {
         let reporter_for_position = reporter.clone();
         let throttler_for_position = throttler.clone();
         let last_seek_time_for_position = self.last_seek_time.clone();
+        let observed_for_position = self.observed.clone();
 
         std::thread::spawn(move || {
             loop {
@@ -294,6 +343,13 @@ impl MpvBackend {
                     mpv_for_position.get_property::<f64>("time-pos"),
                     mpv_for_position.get_property::<f64>("duration"),
                 ) {
+                    // Remember it: both properties belong to the *loaded* file and
+                    // stop resolving the instant MPV unloads it at EOF, which is
+                    // exactly when end-of-file handling asks where playback got to.
+                    // Recorded before the post-seek skip below so a track that ends
+                    // right after a seek still reports the seek target, not zero.
+                    observed_for_position.lock_safe().record(pos, dur);
+
                     // Check if we recently seeked - skip position updates briefly after seeks
                     // to avoid "jumping to zero" visual glitches while MPV is seeking
                     let now = SystemTime::now()
@@ -404,6 +460,9 @@ impl PlayerBackend for MpvBackend {
             let mut state = self.state.lock_safe();
             state.current_media = Some(media.clone());
         }
+        // A different file: the previous one's timestamp must not survive as this
+        // one's "last observed" position.
+        self.observed.lock_safe().reset();
 
         // Load the media file
         self.mpv
@@ -469,6 +528,10 @@ impl PlayerBackend for MpvBackend {
                 message: format!("Failed to seek: {:?}", e),
             })?;
 
+        // The poll thread suppresses updates for 150ms after a seek, so without
+        // this a file ending inside that window would report the pre-seek time.
+        self.observed.lock_safe().record_position(position);
+
         Ok(())
     }
 
@@ -491,15 +554,26 @@ impl PlayerBackend for MpvBackend {
         Ok(())
     }
 
+    /// Current position — the live `time-pos`, or the last one observed while a
+    /// file was loaded.
+    ///
+    /// The fallback is the point: `time-pos` is a property of the *loaded* file,
+    /// so at EOF it stops resolving and a bare `unwrap_or(0.0)` reported 0:00 at
+    /// exactly the moment end-of-file handling asks where playback reached.
+    ///
+    /// TRACES: UR-005 | DR-130 | UT-118
     fn position(&self) -> f64 {
-        self.mpv.get_property::<f64>("time-pos").unwrap_or(0.0)
+        let live = self.mpv.get_property::<f64>("time-pos").ok();
+        self.observed.lock_safe().position_or_last(live)
     }
 
+    /// Total duration — live, or the last one observed. Unloaded at EOF for the
+    /// same reason as `position`.
+    ///
+    /// TRACES: UR-005 | DR-130 | UT-118
     fn duration(&self) -> Option<f64> {
-        self.mpv
-            .get_property::<f64>("duration")
-            .ok()
-            .filter(|d| *d > 0.0)
+        let live = self.mpv.get_property::<f64>("duration").ok();
+        self.observed.lock_safe().duration_or_last(live)
     }
 
     fn state(&self) -> PlayerState {

src-tauri/src/player/stream_end.rs

@@ -102,6 +102,54 @@ pub fn with_start_time(url: &str, position_seconds: f64) -> String {
     format!("{}?{}", base, parts.join("&"))
 }
 
+/// The last playback time actually observed while media was loaded.
+///
+/// Some backends expose position and duration as **live** properties of the
+/// loaded file — MPV's `time-pos` and `duration` stop resolving the moment it
+/// unloads the file at EOF. Reading them straight through means that at exactly
+/// the moment end-of-file handling wants to know where playback got to, the
+/// answer is `0.0` / unknown: the player appears to rewind to 0:00 as it ends.
+///
+/// The polling thread records here, and the accessors fall back to it, so an EOF
+/// reads as the last timestamp rather than as zero.
+#[derive(Debug, Default, Clone, Copy)]
+pub struct ObservedTime {
+    position: f64,
+    duration: Option<f64>,
+}
+
+impl ObservedTime {
+    /// Record a live reading. Non-positive durations are treated as unknown —
+    /// that is how a backend reports "not established yet", not a real zero.
+    pub fn record(&mut self, position: f64, duration: f64) {
+        self.position = position.max(0.0);
+        if duration > 0.0 {
+            self.duration = Some(duration);
+        }
+    }
+
+    /// Record a position alone, e.g. straight after a seek, before the next poll.
+    pub fn record_position(&mut self, position: f64) {
+        self.position = position.max(0.0);
+    }
+
+    /// Forget everything — a different file is loading, and the previous one's
+    /// timestamp must not leak into it.
+    pub fn reset(&mut self) {
+        *self = Self::default();
+    }
+
+    /// The live reading if there is one, else the last observed value.
+    pub fn position_or_last(&self, live: Option<f64>) -> f64 {
+        live.filter(|p| *p >= 0.0).unwrap_or(self.position)
+    }
+
+    /// The live reading if there is one, else the last observed value.
+    pub fn duration_or_last(&self, live: Option<f64>) -> Option<f64> {
+        live.filter(|d| *d > 0.0).or(self.duration)
+    }
+}
+
 /// Budget for consecutive resume attempts that make no progress.
 ///
 /// Held by the player controller across ends of the *same* stream. Any position
@@ -225,6 +273,64 @@ mod tests {
         );
     }
 
+    /// The bug: MPV unloads the file at EOF, so `time-pos` stops resolving and a
+    /// straight read reports 0.0 — the position collapses to zero at precisely
+    /// the moment end-of-file handling needs to know where playback reached.
+    #[test]
+    fn test_eof_reads_as_the_last_observed_timestamp() {
+        let mut observed = ObservedTime::default();
+        observed.record(178.0, 180.0);
+
+        // The file is gone: both live properties fail.
+        assert_eq!(observed.position_or_last(None), 178.0);
+        assert_eq!(observed.duration_or_last(None), Some(180.0));
+    }
+
+    #[test]
+    fn test_live_readings_win_while_the_file_is_loaded() {
+        let mut observed = ObservedTime::default();
+        observed.record(178.0, 180.0);
+
+        assert_eq!(observed.position_or_last(Some(12.0)), 12.0);
+        assert_eq!(observed.duration_or_last(Some(240.0)), Some(240.0));
+    }
+
+    #[test]
+    fn test_unestablished_duration_is_not_recorded_as_zero() {
+        let mut observed = ObservedTime::default();
+        // A backend reports 0.0 for "duration not known yet", not a real zero.
+        observed.record(5.0, 0.0);
+        assert_eq!(observed.duration_or_last(None), None);
+        assert_eq!(observed.position_or_last(None), 5.0);
+
+        observed.record(6.0, 180.0);
+        assert_eq!(observed.duration_or_last(Some(0.0)), Some(180.0));
+    }
+
+    #[test]
+    fn test_reset_stops_the_previous_file_leaking_into_the_next() {
+        let mut observed = ObservedTime::default();
+        observed.record(178.0, 180.0);
+        observed.reset();
+
+        assert_eq!(observed.position_or_last(None), 0.0);
+        assert_eq!(observed.duration_or_last(None), None);
+    }
+
+    #[test]
+    fn test_seek_updates_the_last_position_before_the_next_poll() {
+        let mut observed = ObservedTime::default();
+        observed.record(10.0, 180.0);
+        observed.record_position(120.0);
+
+        assert_eq!(observed.position_or_last(None), 120.0);
+        assert_eq!(
+            observed.duration_or_last(None),
+            Some(180.0),
+            "seeking does not change how long the file is"
+        );
+    }
+
     #[test]
     fn test_resume_tracker_bounds_stalled_retries() {
         let mut tracker = ResumeTracker::default();