fix(analysis): native library backfill coordinator for advanced strategy (#881)

* feat(analysis): native library backfill coordinator for advanced strategy

Move advanced analytics scheduling from the webview loop into a Rust
background worker (configure + spawn_blocking batch/enqueue), matching
cover backfill. Scan hash+BPM gap tracks instead of the full library;
suppress low-priority analysis UI events; limit loudness refresh IPC to
the playback window.

* fix(analysis): flat backfill configure IPC and restore probe track-perf

Use flattened Tauri args like cover backfill so release/prod invoke works;
keep emitting analysis:track-perf for library low-priority work so Performance
Probe tpm/last-track stats update while waveform/enrichment UI events stay suppressed.

* chore(analysis): fix clippy and drop duplicate TS backfill policy

Allow too_many_arguments on library_analysis_backfill_configure for CI;
remove unused frontend batch API and TS watermark helpers now owned in Rust;
clarify analysis_emits_ui_events comment for low-priority track-perf.

* docs: CHANGELOG and credits for PR #881 native analysis backfill

CHANGELOG.md

@@ -413,6 +413,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 
 
+### Analytics — advanced library backfill without webview jank
+
+**By [@cucadmuh](https://github.com/cucadmuh), PR [#881](https://github.com/Psychotoxical/psysonic/pull/881)**
+
+* **Settings → Library → Analytics → Advanced** on large libraries no longer stalls the whole UI (~4 FPS): catalog scheduling runs in a native background worker like cover backfill, not a webview polling loop.
+* Partially analyzed tracks (hash + BPM but missing waveform/loudness) are picked up via a targeted second scan with a reset cursor so the library is not skipped mid-pass.
+* Performance Probe analysis stats still update during background backfill; waveform/enrichment refresh events stay quiet for low-priority work.
+
+
+
 ## [1.46.0] - 2026-05-18
 
 > **🙏 Special thanks to [@zz5zz](https://github.com/zz5zz)** for his tireless quirk-spotting and bug reports on the [Psysonic Discord](https://discord.gg/AMnDRErm4u) — several of the polish fixes in this release landed directly off the back of his messages.

src-tauri/crates/psysonic-analysis/src/analysis_cache/compute.rs

@@ -47,6 +47,7 @@ pub fn seed_from_bytes_execute<R: Runtime>(
     server_id: &str,
     track_id: &str,
     bytes: &[u8],
+    notify_ui: bool,
 ) -> Result<(SeedFromBytesOutcome, AnalysisSeedTimings), String> {
     let seed_started = Instant::now();
     let Some(cache) = app.try_state::<AnalysisCache>() else {
@@ -84,6 +85,7 @@ pub fn seed_from_bytes_execute<R: Runtime>(
             server_id,
             track_id,
             bytes,
+            notify_ui,
         );
         if matches!(enrichment_outcome, TrackEnrichmentOutcome::Failed) {
             let key = TrackKey {
@@ -1233,7 +1235,7 @@ mod tests {
         let app = tauri::test::mock_app();
         let wav = build_mono_pcm16_wav(&sine_440_at_minus_6db(44_100, 0.25), 44_100);
         let handle = app.handle().clone();
-        let (outcome, timings) = seed_from_bytes_execute(&handle, "s", "t", &wav)
+        let (outcome, timings) = seed_from_bytes_execute(&handle, "s", "t", &wav, true)
             .expect("seed execute should return a graceful skip");
         assert_eq!(outcome, SeedFromBytesOutcome::SkippedNoAnalysisCache);
         assert_eq!(timings.seed_ms, 0);
@@ -1248,12 +1250,12 @@ mod tests {
         let handle = app.handle().clone();
 
         let (first, timings_first) =
-            seed_from_bytes_execute(&handle, "server-a", "track-exec", &wav).unwrap();
+            seed_from_bytes_execute(&handle, "server-a", "track-exec", &wav, true).unwrap();
         assert_eq!(first, SeedFromBytesOutcome::Upserted);
         assert!(timings_first.seed_ms <= 30_000);
 
         let (second, timings_second) =
-            seed_from_bytes_execute(&handle, "server-a", "track-exec", &wav).unwrap();
+            seed_from_bytes_execute(&handle, "server-a", "track-exec", &wav, true).unwrap();
         assert_eq!(second, SeedFromBytesOutcome::SkippedWaveformCacheHit);
         assert!(timings_second.seed_ms <= 30_000);
     }

src-tauri/crates/psysonic-analysis/src/analysis_runtime.rs

@@ -4,6 +4,7 @@ use std::sync::{Arc, Mutex, OnceLock};
 
 use tauri::{Emitter, Manager};
 
+use psysonic_core::ports::PlaybackQueryHandle;
 use psysonic_core::user_agent::subsonic_wire_user_agent;
 use psysonic_core::track_enrichment::TrackEnrichmentOutcome;
 
@@ -436,7 +437,14 @@ async fn enqueue_track_analysis_with_fetch(
             content_hash
         );
         let bpm_started = std::time::Instant::now();
-        let outcome = run_track_enrichment_from_bytes(app, server_id, track_id, bytes).await;
+        let outcome = run_track_enrichment_from_bytes(
+            app,
+            server_id,
+            track_id,
+            bytes,
+            analysis_emits_ui_events(priority),
+        )
+        .await;
         if matches!(outcome, TrackEnrichmentOutcome::Failed) {
             if let Some(cache) = app.try_state::<analysis_cache::AnalysisCache>() {
                 let key = analysis_cache::TrackKey {
@@ -464,6 +472,7 @@ pub async fn run_track_enrichment_from_bytes(
     server_id: &str,
     track_id: &str,
     bytes: &[u8],
+    notify_ui: bool,
 ) -> TrackEnrichmentOutcome {
     if server_id.is_empty() {
         return TrackEnrichmentOutcome::SkippedNoServer;
@@ -473,7 +482,7 @@ pub async fn run_track_enrichment_from_bytes(
     let tid = track_id.to_string();
     let data = bytes.to_vec();
     match tokio::task::spawn_blocking(move || {
-        crate::track_enrichment::run_track_enrichment_if_needed(&app, &sid, &tid, &data)
+        crate::track_enrichment::run_track_enrichment_if_needed(&app, &sid, &tid, &data, notify_ui)
     })
     .await
     {
@@ -795,6 +804,118 @@ pub fn analysis_backfill_resolve_priority(
     AnalysisBackfillPriority::Low
 }
 
+/// Library backfill uses `Low` — skip waveform / enrichment refresh IPC (`analysis:track-perf` still emits for probes).
+pub fn analysis_emits_ui_events(priority: AnalysisBackfillPriority) -> bool {
+    !matches!(priority, AnalysisBackfillPriority::Low)
+}
+
+/// Enqueue HTTP download + analysis seed (native coordinator + optional UI invoke).
+pub fn enqueue_seed_from_url(
+    app: &tauri::AppHandle,
+    track_id: &str,
+    url: &str,
+    server_id_hint: Option<&str>,
+    explicit_priority: Option<AnalysisBackfillPriority>,
+    force: bool,
+) -> Result<(), String> {
+    if track_id.trim().is_empty() || url.trim().is_empty() {
+        return Ok(());
+    }
+    let server_id = if let Ok(parsed) = reqwest::Url::parse(url) {
+        if parsed.scheme() == "http" || parsed.scheme() == "https" {
+            let host = parsed.host_str().unwrap_or_default();
+            let mut base_path = parsed.path().to_string();
+            if let Some(idx) = base_path.find("/rest") {
+                base_path.truncate(idx);
+            }
+            while base_path.ends_with('/') {
+                base_path.pop();
+            }
+            if host.is_empty() {
+                server_id_hint.unwrap_or("").to_string()
+            } else {
+                let mut base = host.to_string();
+                if let Some(port) = parsed.port() {
+                    base.push_str(&format!(":{port}"));
+                }
+                if !base_path.is_empty() {
+                    base.push_str(&base_path);
+                }
+                base
+            }
+        } else {
+            server_id_hint.unwrap_or("").to_string()
+        }
+    } else {
+        server_id_hint.unwrap_or("").to_string()
+    };
+    if !force {
+        if let Some(playback) = app.try_state::<PlaybackQueryHandle>() {
+            if playback.ranged_loudness_backfill_should_defer(track_id) {
+                crate::app_deprintln!(
+                    "[analysis] backfill skip track_id={} reason=ranged_playback_will_seed",
+                    track_id
+                );
+                return Ok(());
+            }
+        }
+    }
+    if !force {
+        if let Some(cache) = app.try_state::<analysis_cache::AnalysisCache>() {
+            if cache.cpu_seed_redundant_for_track(&server_id, track_id)? {
+                if server_id.is_empty() {
+                    crate::app_deprintln!(
+                        "[analysis] backfill skip (no server scope): {}",
+                        track_id
+                    );
+                    return Ok(());
+                }
+                if !track_analysis_needs_work(app, &server_id, track_id)? {
+                    crate::app_deprintln!(
+                        "[analysis] backfill skip (analysis complete): {}",
+                        track_id
+                    );
+                    return Ok(());
+                }
+                crate::app_deprintln!(
+                    "[analysis] backfill enqueue (analysis pending) track_id={}",
+                    track_id
+                );
+            }
+        }
+    }
+    let tid_log = track_id.to_string();
+    let resolved = analysis_backfill_resolve_priority(app, &server_id, track_id, explicit_priority);
+    let shared = analysis_backfill_shared(app);
+    let kind = {
+        let mut st = shared
+            .state
+            .lock()
+            .map_err(|_| "analysis backfill lock poisoned".to_string())?;
+        st.enqueue(server_id, track_id.to_string(), url.to_string(), resolved)
+    };
+    match kind {
+        AnalysisBackfillEnqueueKind::NewLow
+        | AnalysisBackfillEnqueueKind::NewMiddle
+        | AnalysisBackfillEnqueueKind::NewHigh => {
+            shared.ping_worker();
+            crate::app_deprintln!(
+                "[analysis] backfill enqueued: track_id={} priority={resolved:?}",
+                tid_log,
+            );
+        }
+        AnalysisBackfillEnqueueKind::ReorderedHigher => {
+            shared.ping_worker();
+            crate::app_deprintln!(
+                "[analysis] backfill bumped tier track_id={} priority={resolved:?}",
+                tid_log,
+            );
+        }
+        AnalysisBackfillEnqueueKind::DuplicateSkipped | AnalysisBackfillEnqueueKind::RunningSkipped => {}
+    }
+    Ok(())
+}
+
 // ─── Full-track waveform + loudness: CPU seed queue (parallel decode workers) ─
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
@@ -1131,12 +1252,19 @@ async fn spawn_cpu_seed_slots(app: &tauri::AppHandle, shared: &Arc<AnalysisCpuSe
         let app_for_decode = app.clone();
         let app_for_events = app.clone();
         let shared = shared.clone();
+        let notify_ui = analysis_emits_ui_events(job.priority);
         tauri::async_runtime::spawn(async move {
             let sid = job.server_id.clone();
             let tid = job.track_id.clone();
             let bytes = job.bytes;
             let seed_result = tokio::task::spawn_blocking(move || {
-                analysis_cache::seed_from_bytes_execute(&app_for_decode, &sid, &tid, &bytes)
+                analysis_cache::seed_from_bytes_execute(
+                    &app_for_decode,
+                    &sid,
+                    &tid,
+                    &bytes,
+                    notify_ui,
+                )
             })
             .await
             .unwrap_or_else(|e| Err(format!("cpu-seed spawn_blocking: {e}")));
@@ -1181,7 +1309,7 @@ async fn spawn_cpu_seed_slots(app: &tauri::AppHandle, shared: &Arc<AnalysisCpuSe
                         tid_log,
                         ok
                     );
-                    if ok {
+                    if ok && notify_ui {
                         let _ = app_for_events.emit(
                             "analysis:waveform-updated",
                             WaveformUpdatedPayload {

src-tauri/crates/psysonic-analysis/src/commands.rs

@@ -5,16 +5,10 @@
 
 use std::collections::HashSet;
 
-use tauri::Manager;
-
-use psysonic_core::ports::PlaybackQueryHandle;
-
 use crate::analysis_cache;
 use crate::analysis_runtime::{
-    analysis_backfill_queue_stats, analysis_backfill_resolve_priority, analysis_backfill_shared,
-    analysis_pipeline_queue_stats, prune_analysis_queues, track_analysis_needs_work,
-    AnalysisBackfillEnqueueKind,
-    AnalysisBackfillPriority, PlaybackPriorityHints,
+    analysis_backfill_queue_stats, analysis_pipeline_queue_stats, enqueue_seed_from_url,
+    prune_analysis_queues, AnalysisBackfillPriority, PlaybackPriorityHints,
 };
 
 #[derive(serde::Serialize)]
@@ -313,105 +307,15 @@ pub fn analysis_enqueue_seed_from_url(
     priority: Option<String>,
     app: tauri::AppHandle,
 ) -> Result<(), String> {
-    if track_id.trim().is_empty() || url.trim().is_empty() {
-        return Ok(());
-    }
-    let server_id = if let Ok(parsed) = reqwest::Url::parse(&url) {
-        if parsed.scheme() == "http" || parsed.scheme() == "https" {
-            let host = parsed.host_str().unwrap_or_default();
-            let mut base_path = parsed.path().to_string();
-            if let Some(idx) = base_path.find("/rest") {
-                base_path.truncate(idx);
-            }
-            while base_path.ends_with('/') {
-                base_path.pop();
-            }
-            if host.is_empty() {
-                server_id.unwrap_or_default()
-            } else {
-                let mut base = host.to_string();
-                if let Some(port) = parsed.port() {
-                    base.push_str(&format!(":{port}"));
-                }
-                if !base_path.is_empty() {
-                    base.push_str(&base_path);
-                }
-                base
-            }
-        } else {
-            server_id.unwrap_or_default()
-        }
-    } else {
-        server_id.unwrap_or_default()
-    };
-    let force = force.unwrap_or(false);
-    if !force {
-        if let Some(playback) = app.try_state::<PlaybackQueryHandle>() {
-            if playback.ranged_loudness_backfill_should_defer(&track_id) {
-                crate::app_deprintln!(
-                    "[analysis] backfill skip track_id={} reason=ranged_playback_will_seed",
-                    track_id
-                );
-                return Ok(());
-            }
-        }
-    }
-    if !force {
-        if let Some(cache) = app.try_state::<analysis_cache::AnalysisCache>() {
-            if cache.cpu_seed_redundant_for_track(&server_id, &track_id)? {
-                if server_id.is_empty() {
-                    crate::app_deprintln!(
-                        "[analysis] backfill skip (no server scope): {}",
-                        track_id
-                    );
-                    return Ok(());
-                }
-                if !track_analysis_needs_work(&app, &server_id, &track_id)? {
-                    crate::app_deprintln!(
-                        "[analysis] backfill skip (analysis complete): {}",
-                        track_id
-                    );
-                    return Ok(());
-                }
-                crate::app_deprintln!(
-                    "[analysis] backfill enqueue (analysis pending) track_id={}",
-                    track_id
-                );
-            }
-        }
-    }
-    let tid_log = track_id.clone();
     let explicit = AnalysisBackfillPriority::from_optional_str(priority.as_deref());
-    let resolved =
-        analysis_backfill_resolve_priority(&app, &server_id, &track_id, explicit);
-    let shared = analysis_backfill_shared(&app);
-    let kind = {
-        let mut st = shared
-            .state
-            .lock()
-            .map_err(|_| "analysis backfill lock poisoned".to_string())?;
-        st.enqueue(server_id, track_id, url, resolved)
-    };
-    match kind {
-        AnalysisBackfillEnqueueKind::NewLow
-        | AnalysisBackfillEnqueueKind::NewMiddle
-        | AnalysisBackfillEnqueueKind::NewHigh => {
-            shared.ping_worker();
-            crate::app_deprintln!(
-                "[analysis] backfill enqueued: track_id={} priority={resolved:?}",
-                tid_log,
-            );
-        }
-        AnalysisBackfillEnqueueKind::ReorderedHigher => {
-            shared.ping_worker();
-            crate::app_deprintln!(
-                "[analysis] backfill bumped tier track_id={} priority={resolved:?}",
-                tid_log,
-            );
-        }
-        AnalysisBackfillEnqueueKind::DuplicateSkipped | AnalysisBackfillEnqueueKind::RunningSkipped => {}
-    }
-    Ok(())
+    enqueue_seed_from_url(
+        &app,
+        &track_id,
+        &url,
+        server_id.as_deref(),
+        explicit,
+        force.unwrap_or(false),
+    )
 }
 
 #[derive(Debug, Clone, serde::Deserialize)]

src-tauri/crates/psysonic-analysis/src/track_enrichment.rs

@@ -35,6 +35,7 @@ pub fn run_track_enrichment_if_needed<R: Runtime>(
     server_id: &str,
     track_id: &str,
     bytes: &[u8],
+    notify_ui: bool,
 ) -> TrackEnrichmentOutcome {
     if server_id.is_empty() {
         return TrackEnrichmentOutcome::SkippedNoServer;
@@ -56,7 +57,9 @@ pub fn run_track_enrichment_if_needed<R: Runtime>(
                 server_id,
                 content_hash
             );
-            emit_enrichment_updated(app, server_id, track_id);
+            if notify_ui {
+                emit_enrichment_updated(app, server_id, track_id);
+            }
             TrackEnrichmentOutcome::Applied
         }
         Err(e) => {

src-tauri/crates/psysonic-integration/src/subsonic/mod.rs

@@ -5,12 +5,14 @@
 pub mod auth;
 pub mod client;
 pub mod error;
+pub mod stream_url;
 pub mod types;
 
 pub use auth::SubsonicCredentials;
 pub use client::{
     fingerprint_sample, SubsonicClient, SUBSONIC_API_VERSION, SUBSONIC_CLIENT_ID,
 };
+pub use stream_url::{build_stream_view_url, rest_base_from_url};
 pub use error::SubsonicError;
 pub use types::{
     Album, AlbumSummary, ArtistIndex, ArtistRef, IndexBucket, ScanStatus, SearchResult, ServerInfo,

src-tauri/crates/psysonic-integration/src/subsonic/stream_url.rs

@@ -0,0 +1,61 @@
+//! Subsonic `stream.view` URLs for native library analysis backfill.
+
+use url::Url;
+
+use super::auth::SubsonicCredentials;
+use super::client::{SUBSONIC_API_VERSION, SUBSONIC_CLIENT_ID};
+
+/// `{origin}/rest` — mirrors frontend `restBaseFromUrl`.
+pub fn rest_base_from_url(server_url: &str) -> String {
+    let trimmed = server_url.trim().trim_end_matches('/');
+    let base = if trimmed.starts_with("http://") || trimmed.starts_with("https://") {
+        trimmed.to_string()
+    } else {
+        format!("http://{trimmed}")
+    };
+    format!("{base}/rest")
+}
+
+/// Authenticated `stream.view` URL for a library track id.
+pub fn build_stream_view_url(
+    server_url: &str,
+    username: &str,
+    password: &str,
+    track_id: &str,
+) -> String {
+    let creds = SubsonicCredentials::from_password(username, password);
+    let base = rest_base_from_url(server_url);
+    let mut url =
+        Url::parse(&format!("{base}/stream.view")).unwrap_or_else(|_| Url::parse("http://invalid/rest/stream.view").unwrap());
+    {
+        let mut q = url.query_pairs_mut();
+        q.append_pair("id", track_id);
+        q.append_pair("u", &creds.username);
+        q.append_pair("t", &creds.token);
+        q.append_pair("s", &creds.salt);
+        q.append_pair("v", SUBSONIC_API_VERSION);
+        q.append_pair("c", SUBSONIC_CLIENT_ID);
+        q.append_pair("f", "json");
+    }
+    url.to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn stream_url_contains_track_and_auth_params() {
+        let url = build_stream_view_url(
+            "https://music.example",
+            "alice",
+            "secret",
+            "tr-42",
+        );
+        assert!(url.contains("stream.view"));
+        assert!(url.contains("id=tr-42"));
+        assert!(url.contains("u=alice"));
+        assert!(url.contains("&t="));
+        assert!(url.contains("&s="));
+    }
+}

src-tauri/crates/psysonic-library/src/analysis_backfill.rs

@@ -31,14 +31,12 @@ pub struct LibraryAnalysisProgressDto {
 
 enum ScanMode {
     Candidates,
-    Full,
+    /// Tracks with hash + BPM that may still need waveform/LUFS/enrichment gaps.
+    HashBpmGaps,
 }
 
-/// Candidate SQL skips tracks that already have `content_hash` and an analysis BPM
-/// fact. Those rows can still need waveform/LUFS — the full-table pass must start
-/// from the first id, not from the last candidate cursor.
-fn begin_full_library_scan() -> (ScanMode, Option<String>) {
-    (ScanMode::Full, None)
+fn begin_hash_bpm_gap_scan() -> (ScanMode, Option<String>) {
+    (ScanMode::HashBpmGaps, None)
 }
 
 pub fn collect_analysis_backfill_batch(
@@ -64,16 +62,18 @@ pub fn collect_analysis_backfill_batch(
             ScanMode::Candidates => {
                 repo.list_analysis_candidate_ids_after(server_id, after.as_deref(), SCAN_CHUNK)?
             }
-            ScanMode::Full => repo.list_track_ids_after(server_id, after.as_deref(), SCAN_CHUNK)?,
+            ScanMode::HashBpmGaps => {
+                repo.list_analysis_hash_bpm_ids_after(server_id, after.as_deref(), SCAN_CHUNK)?
+            }
         };
 
         if page.is_empty() {
             match mode {
                 ScanMode::Candidates => {
-                    (mode, after) = begin_full_library_scan();
+                    (mode, after) = begin_hash_bpm_gap_scan();
                     continue;
                 }
-                ScanMode::Full => {
+                ScanMode::HashBpmGaps => {
                     return Ok(LibraryAnalysisBackfillBatchDto {
                         track_ids: found,
                         next_cursor: after,
@@ -105,9 +105,9 @@ pub fn collect_analysis_backfill_batch(
         if page_len < SCAN_CHUNK {
             match mode {
                 ScanMode::Candidates => {
-                    (mode, after) = begin_full_library_scan();
+                    (mode, after) = begin_hash_bpm_gap_scan();
                 }
-                ScanMode::Full => {
+                ScanMode::HashBpmGaps => {
                     return Ok(LibraryAnalysisBackfillBatchDto {
                         track_ids: found,
                         next_cursor: after,

src-tauri/crates/psysonic-library/src/analysis_backfill_policy.rs

@@ -0,0 +1,64 @@
+//! Library analysis backfill queue watermark — native coordinator (spec: Settings → Library).
+
+pub const LIBRARY_BACKLOG_DEPTH_MULTIPLIER: u32 = 3;
+pub const LIBRARY_BACKLOG_MIN: u32 = 8;
+pub const LIBRARY_BACKLOG_MAX: u32 = 240;
+pub const LIBRARY_ANALYSIS_BACKFILL_BATCH_SIZE: u32 = 20;
+
+#[derive(Debug, Clone, Copy, Default)]
+pub struct PipelineBacklogCounts {
+    pub http_queued: u32,
+    pub http_download_active: u32,
+    pub cpu_queued: u32,
+    pub cpu_decode_active: u32,
+}
+
+impl PipelineBacklogCounts {
+    pub fn total(self) -> u32 {
+        self.http_queued
+            .saturating_add(self.http_download_active)
+            .saturating_add(self.cpu_queued)
+            .saturating_add(self.cpu_decode_active)
+    }
+}
+
+pub fn compute_library_backfill_target_depth(workers: u32) -> u32 {
+    let w = workers.max(1);
+    (w * LIBRARY_BACKLOG_DEPTH_MULTIPLIER).clamp(LIBRARY_BACKLOG_MIN, LIBRARY_BACKLOG_MAX)
+}
+
+pub fn library_backfill_needs_top_up(counts: PipelineBacklogCounts, workers: u32) -> bool {
+    counts.total() < compute_library_backfill_target_depth(workers)
+}
+
+pub fn library_backfill_top_up_limit(counts: PipelineBacklogCounts, workers: u32) -> u32 {
+    let target = compute_library_backfill_target_depth(workers);
+    let deficit = target.saturating_sub(counts.total());
+    if deficit == 0 {
+        return 0;
+    }
+    deficit.min(LIBRARY_ANALYSIS_BACKFILL_BATCH_SIZE)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn target_depth_uses_floor_and_cap() {
+        assert_eq!(compute_library_backfill_target_depth(1), 8);
+        assert_eq!(compute_library_backfill_target_depth(4), 12);
+        assert_eq!(compute_library_backfill_target_depth(100), 240);
+    }
+
+    #[test]
+    fn top_up_when_backlog_below_target() {
+        let counts = PipelineBacklogCounts {
+            http_queued: 2,
+            http_download_active: 1,
+            ..Default::default()
+        };
+        assert!(library_backfill_needs_top_up(counts, 8));
+        assert_eq!(library_backfill_top_up_limit(counts, 8), 20);
+    }
+}

src-tauri/crates/psysonic-library/src/lib.rs

@@ -13,6 +13,8 @@ pub mod album_compilation_filter;
 pub mod browse_support;
 mod advanced_search_mood;
 pub mod analysis_backfill;
+pub mod analysis_backfill_policy;
+pub mod library_readiness;
 pub mod artist_lossless_browse;
 pub mod cover_backfill;
 pub mod cover_resolve;

src-tauri/crates/psysonic-library/src/library_readiness.rs

@@ -0,0 +1,64 @@
+//! When the local library index is safe for background analysis backfill.
+
+use crate::dto::local_tracks_max_updated_ms;
+use crate::repos::{sync_state::SyncStateRepository, TrackRepository};
+use crate::store::LibraryStore;
+
+/// Mirrors frontend `libraryStatusIsReady` / `libraryIsReady` (spec §9.3).
+pub fn library_server_is_ready(store: &LibraryStore, server_id: &str) -> Result<bool, String> {
+    let repo = SyncStateRepository::new(store);
+    let phase = repo
+        .get_sync_phase(server_id, "")
+        .map_err(|e| e.to_string())?;
+
+    let Some(phase) = phase else {
+        return Ok(has_any_local_tracks(store, server_id));
+    };
+
+    if phase == "ready" {
+        return Ok(true);
+    }
+    if phase == "initial_sync" {
+        let local = repo
+            .get_local_track_count(server_id, "")
+            .map_err(|e| e.to_string())?
+            .unwrap_or(0);
+        let server = repo
+            .get_server_track_count(server_id, "")
+            .map_err(|e| e.to_string())?
+            .unwrap_or(0);
+        if server > 0 && (local as f64 / server as f64) >= 0.95 {
+            return Ok(true);
+        }
+        return Ok(false);
+    }
+    if phase == "idle" {
+        if has_any_local_tracks(store, server_id) {
+            return Ok(true);
+        }
+        if repo
+            .has_last_full_sync_at(server_id, "")
+            .map_err(|e| e.to_string())?
+        {
+            return Ok(true);
+        }
+        if local_tracks_max_updated_ms(store, server_id)?
+            .is_some_and(|ms| ms > 0)
+        {
+            return Ok(true);
+        }
+        let local = repo
+            .get_local_track_count(server_id, "")
+            .map_err(|e| e.to_string())?
+            .unwrap_or(0);
+        return Ok(local > 0);
+    }
+    Ok(false)
+}
+
+fn has_any_local_tracks(store: &LibraryStore, server_id: &str) -> bool {
+    TrackRepository::new(store)
+        .count_live_tracks(server_id)
+        .map(|n| n > 0)
+        .unwrap_or(false)
+}

src-tauri/crates/psysonic-library/src/repos/track.rs

@@ -292,6 +292,37 @@ impl<'a> TrackRepository<'a> {
         })
     }
 
+    /// Tracks with `content_hash` and an analysis BPM fact — may still lack waveform/LUFS.
+    /// Confirmed per id via [`TrackAnalysisNeedsWorkQuery`].
+    pub fn list_analysis_hash_bpm_ids_after(
+        &self,
+        server_id: &str,
+        after_id: Option<&str>,
+        limit: usize,
+    ) -> Result<Vec<String>, String> {
+        if limit == 0 {
+            return Ok(vec![]);
+        }
+        let limit = i64::try_from(limit).map_err(|e| e.to_string())?;
+        self.store.with_read_conn(|conn| {
+            let sql = "SELECT t.id FROM track t \
+                       WHERE t.server_id = ?1 AND t.deleted = 0 \
+                         AND (?2 IS NULL OR t.id > ?2) \
+                         AND t.content_hash IS NOT NULL \
+                         AND EXISTS ( \
+                           SELECT 1 FROM track_fact f \
+                           WHERE f.server_id = t.server_id \
+                             AND f.track_id = t.id \
+                             AND f.fact_kind = 'bpm' \
+                             AND f.source_kind = 'analysis' \
+                         ) \
+                       ORDER BY t.id ASC LIMIT ?3";
+            let mut stmt = conn.prepare(sql)?;
+            let rows = stmt.query_map(params![server_id, after_id, limit], |row| row.get(0))?;
+            rows.collect::<rusqlite::Result<Vec<String>>>()
+        })
+    }
+
     /// Cheap SQL prefilter: tracks that never received a playback hash and/or
     /// lack an oximedia BPM fact. Full analysis gaps are confirmed per id via
     /// [`TrackAnalysisNeedsWorkQuery`] in the shell crate.

src-tauri/src/lib.rs

@@ -3,6 +3,7 @@
 
 pub mod cli;
 mod cover_cache;
+mod library_analysis_backfill;
 mod lib_commands;
 
 pub use psysonic_integration::discord;
@@ -123,6 +124,9 @@ pub fn run() {
             cover_cache::init_cover_cache(app.handle())
                 .map_err(|e| format!("cover cache init failed: {e}"))?;
 
+            library_analysis_backfill::init_library_analysis_backfill(app.handle())
+                .map_err(|e| format!("library analysis backfill init failed: {e}"))?;
+
             // ── Library track store (psysonic-library, PR-5a + PR-5b) ─────
             // PR-5a brought up the read-only Tauri surface + LibraryRuntime.
             // PR-5b adds the mutating commands, sync session map, current-job
@@ -734,6 +738,7 @@ pub fn run() {
             psysonic_library::commands::library_migrate_server_index_keys,
             psysonic_library::commands::library_delete_server_data,
             psysonic_library::commands::library_analysis_backfill_batch,
+            library_analysis_backfill::library_analysis_backfill_configure,
             psysonic_library::commands::library_resolve_cover_entry,
             cover_cache::cover_cache_peek_batch,
             cover_cache::cover_cache_ensure,

src-tauri/src/library_analysis_backfill/mod.rs

@@ -0,0 +1,59 @@
+//! Library analysis backfill — native coordinator (advanced analytics strategy).
+
+mod worker;
+
+use std::sync::Arc;
+
+use tauri::{AppHandle, Manager};
+use worker::{
+    spawn_coordinator, setup_library_sync_idle_listener, LibraryAnalysisBackfillSession,
+    LibraryAnalysisBackfillWorker,
+};
+
+
+pub fn init_library_analysis_backfill(app: &AppHandle) -> Result<(), String> {
+    let worker = Arc::new(LibraryAnalysisBackfillWorker::new());
+    app.manage(worker.clone());
+    setup_library_sync_idle_listener(app);
+    spawn_coordinator(app, worker);
+    Ok(())
+}
+
+#[tauri::command]
+#[allow(clippy::too_many_arguments)] // Tauri command surface — args map 1:1 to the JS call (like cover configure + workers).
+pub async fn library_analysis_backfill_configure(
+    app: AppHandle,
+    enabled: bool,
+    server_index_key: String,
+    library_server_id: String,
+    server_url: String,
+    username: String,
+    password: String,
+    workers: u32,
+) -> Result<(), String> {
+    let worker = app
+        .try_state::<Arc<LibraryAnalysisBackfillWorker>>()
+        .ok_or_else(|| "library analysis backfill worker not initialized".to_string())?;
+
+    let session = if enabled
+        && !server_index_key.is_empty()
+        && !library_server_id.is_empty()
+        && !server_url.is_empty()
+    {
+        Some(LibraryAnalysisBackfillSession {
+            server_index_key,
+            library_server_id,
+            server_url,
+            username,
+            password,
+            workers: workers.max(1),
+        })
+    } else {
+        None
+    };
+
+    worker
+        .set_session(enabled && session.is_some(), session)
+        .await;
+    Ok(())
+}

src-tauri/src/library_analysis_backfill/worker.rs

@@ -0,0 +1,343 @@
+//! Native library analysis backfill coordinator (advanced strategy).
+//!
+//! Replaces the webview `while` loop: top-up HTTP/CPU seed backlog without
+//! blocking the UI on `library_analysis_backfill_batch` IPC.
+
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::Arc;
+use std::time::Duration;
+
+use psysonic_analysis::analysis_runtime::{
+    analysis_pipeline_queue_stats, analysis_set_pipeline_parallelism, enqueue_seed_from_url,
+    AnalysisBackfillPriority,
+};
+use psysonic_integration::subsonic::build_stream_view_url;
+use psysonic_library::analysis_backfill::{
+    collect_analysis_backfill_batch, collect_analysis_progress, LibraryAnalysisBackfillBatchDto,
+};
+use psysonic_library::analysis_backfill_policy::{
+    library_backfill_needs_top_up, library_backfill_top_up_limit, PipelineBacklogCounts,
+};
+use psysonic_library::library_readiness::library_server_is_ready;
+use psysonic_library::payload::LibrarySyncProgressPayload;
+use psysonic_library::repos::TrackRepository;
+use psysonic_library::LibraryRuntime;
+use serde::Deserialize;
+use tauri::{AppHandle, Listener, Manager};
+use tokio::sync::Mutex;
+
+const TOP_UP_POLL_MS: u64 = 500;
+const STEADY_POLL_MS: u64 = 2000;
+const READY_POLL_MS: u64 = 5000;
+const EXHAUSTED_PAUSE_MS: u64 = 15_000;
+const EXHAUSTED_PENDING_RESCAN_MS: u64 = 2000;
+const COMPLETED_RECHECK_MS: u64 = 300_000;
+const EXHAUSTED_DONE_STREAK: u32 = 2;
+const SYNC_WAIT_MS: u64 = 5000;
+
+#[derive(Clone)]
+pub struct LibraryAnalysisBackfillSession {
+    pub server_index_key: String,
+    pub library_server_id: String,
+    pub server_url: String,
+    pub username: String,
+    pub password: String,
+    pub workers: u32,
+}
+
+pub struct LibraryAnalysisBackfillWorker {
+    pub enabled: AtomicBool,
+    session: Mutex<Option<LibraryAnalysisBackfillSession>>,
+    cursor: Mutex<Option<String>>,
+    completed_total: Mutex<Option<i64>>,
+    exhausted_streak: Mutex<u32>,
+}
+
+impl LibraryAnalysisBackfillWorker {
+    pub fn new() -> Self {
+        Self {
+            enabled: AtomicBool::new(false),
+            session: Mutex::new(None),
+            cursor: Mutex::new(None),
+            completed_total: Mutex::new(None),
+            exhausted_streak: Mutex::new(0),
+        }
+    }
+
+    pub async fn set_session(&self, enabled: bool, session: Option<LibraryAnalysisBackfillSession>) {
+        self.enabled.store(enabled, Ordering::Relaxed);
+        *self.session.lock().await = session;
+        if !enabled {
+            *self.cursor.lock().await = None;
+            *self.completed_total.lock().await = None;
+            *self.exhausted_streak.lock().await = 0;
+        }
+    }
+}
+
+async fn session_still_focused(
+    worker: &LibraryAnalysisBackfillWorker,
+    expected: &LibraryAnalysisBackfillSession,
+) -> bool {
+    if !worker.enabled.load(Ordering::Relaxed) {
+        return false;
+    }
+    worker
+        .session
+        .lock()
+        .await
+        .as_ref()
+        .is_some_and(|s| s.server_index_key == expected.server_index_key)
+}
+
+fn sync_blocks_backfill(store: &psysonic_library::store::LibraryStore, server_id: &str) -> bool {
+    use psysonic_library::repos::sync_state::SyncStateRepository;
+    let repo = SyncStateRepository::new(store);
+    match repo.get_sync_phase(server_id, "") {
+        Ok(Some(phase)) => phase == "initial_sync" || phase == "probing",
+        _ => false,
+    }
+}
+
+fn session_matches_server(session: &LibraryAnalysisBackfillSession, server_id: &str) -> bool {
+    server_id == session.server_index_key || server_id == session.library_server_id
+}
+
+struct CoordinatorTick {
+    sleep_ms: u64,
+}
+
+async fn run_coordinator_forever(app: AppHandle, worker: Arc<LibraryAnalysisBackfillWorker>) {
+    loop {
+        let tick = coordinator_tick(&app, worker.as_ref()).await;
+        tokio::time::sleep(Duration::from_millis(tick.sleep_ms)).await;
+    }
+}
+
+async fn coordinator_tick(
+    app: &AppHandle,
+    worker: &LibraryAnalysisBackfillWorker,
+) -> CoordinatorTick {
+    if !worker.enabled.load(Ordering::Relaxed) {
+        return CoordinatorTick { sleep_ms: STEADY_POLL_MS };
+    }
+
+    let session = worker.session.lock().await.clone();
+    let Some(session) = session else {
+        return CoordinatorTick { sleep_ms: STEADY_POLL_MS };
+    };
+
+    if !session_still_focused(worker, &session).await {
+        return CoordinatorTick { sleep_ms: STEADY_POLL_MS };
+    }
+
+    analysis_set_pipeline_parallelism(session.workers as usize);
+
+    let runtime = match app.try_state::<LibraryRuntime>() {
+        Some(r) => r,
+        None => return CoordinatorTick { sleep_ms: READY_POLL_MS },
+    };
+
+    if let Some(done_total) = *worker.completed_total.lock().await {
+        let store = runtime.store.clone();
+        let lib_id = session.library_server_id.clone();
+        let still_same = tauri::async_runtime::spawn_blocking(move || {
+            TrackRepository::new(&store)
+                .count_live_tracks(&lib_id)
+                .map(|n| n == done_total)
+        })
+        .await
+        .ok()
+        .and_then(|r| r.ok())
+        .unwrap_or(false);
+        if still_same {
+            return CoordinatorTick {
+                sleep_ms: COMPLETED_RECHECK_MS,
+            };
+        }
+        *worker.completed_total.lock().await = None;
+        *worker.cursor.lock().await = None;
+        *worker.exhausted_streak.lock().await = 0;
+    }
+
+    while sync_blocks_backfill(&runtime.store, &session.library_server_id) {
+        if !worker.enabled.load(Ordering::Relaxed) {
+            return CoordinatorTick { sleep_ms: SYNC_WAIT_MS };
+        }
+        tokio::time::sleep(Duration::from_millis(SYNC_WAIT_MS)).await;
+    }
+
+    let store = runtime.store.clone();
+    let lib_id = session.library_server_id.clone();
+    let ready = tauri::async_runtime::spawn_blocking(move || library_server_is_ready(&store, &lib_id))
+        .await
+        .ok()
+        .and_then(|r| r.ok())
+        .unwrap_or(false);
+    if !ready {
+        return CoordinatorTick { sleep_ms: READY_POLL_MS };
+    }
+
+    let stats = analysis_pipeline_queue_stats();
+    let counts = PipelineBacklogCounts {
+        http_queued: stats.http_queued as u32,
+        http_download_active: stats.http_download_active as u32,
+        cpu_queued: stats.cpu_queued as u32,
+        cpu_decode_active: stats.cpu_decode_active as u32,
+    };
+
+    if !library_backfill_needs_top_up(counts, session.workers) {
+        return CoordinatorTick { sleep_ms: STEADY_POLL_MS };
+    }
+
+    let fetch_limit = library_backfill_top_up_limit(counts, session.workers);
+    if fetch_limit == 0 {
+        return CoordinatorTick { sleep_ms: TOP_UP_POLL_MS };
+    }
+
+    let cursor = worker.cursor.lock().await.clone();
+    let app_for_batch = app.clone();
+    let lib_id = session.library_server_id.clone();
+    let batch: Option<LibraryAnalysisBackfillBatchDto> = tauri::async_runtime::spawn_blocking(
+        move || {
+            let runtime = app_for_batch
+                .try_state::<LibraryRuntime>()
+                .ok_or_else(|| "LibraryRuntime not available".to_string())?;
+            collect_analysis_backfill_batch(
+                &app_for_batch,
+                &runtime,
+                lib_id.trim(),
+                cursor.as_deref().filter(|s| !s.is_empty()),
+                Some(fetch_limit),
+            )
+        },
+    )
+    .await
+    .ok()
+    .and_then(|r| r.ok());
+
+    let Some(batch) = batch else {
+        return CoordinatorTick { sleep_ms: TOP_UP_POLL_MS };
+    };
+
+    *worker.cursor.lock().await = batch.next_cursor.clone();
+
+    let enqueued_count = batch.track_ids.len();
+    let track_ids = batch.track_ids.clone();
+    let index_key = session.server_index_key.clone();
+    let server_url = session.server_url.clone();
+    let username = session.username.clone();
+    let password = session.password.clone();
+    let app_for_enqueue = app.clone();
+
+    let _ = tauri::async_runtime::spawn_blocking(move || {
+        for track_id in &track_ids {
+            let url = build_stream_view_url(&server_url, &username, &password, track_id);
+            let _ = enqueue_seed_from_url(
+                &app_for_enqueue,
+                track_id,
+                &url,
+                Some(index_key.as_str()),
+                Some(AnalysisBackfillPriority::Low),
+                false,
+            );
+        }
+    })
+    .await;
+
+    if enqueued_count > 0 {
+        *worker.exhausted_streak.lock().await = 0;
+    }
+
+    if batch.exhausted {
+        let app_for_progress = app.clone();
+        let lib_id = session.library_server_id.clone();
+        let progress = tauri::async_runtime::spawn_blocking(move || {
+            let runtime = app_for_progress
+                .try_state::<LibraryRuntime>()
+                .ok_or_else(|| "LibraryRuntime not available".to_string())?;
+            collect_analysis_progress(&app_for_progress, &runtime, lib_id.trim())
+        })
+        .await
+        .ok()
+        .and_then(|r| r.ok());
+
+        let pending = progress.as_ref().map(|p| p.pending_tracks).unwrap_or(-1);
+        if pending <= 0 && enqueued_count == 0 {
+            let mut streak = worker.exhausted_streak.lock().await;
+            *streak += 1;
+            if *streak >= EXHAUSTED_DONE_STREAK {
+                if let Some(p) = progress {
+                    *worker.completed_total.lock().await = Some(p.total_tracks);
+                }
+                *worker.cursor.lock().await = None;
+                return CoordinatorTick {
+                    sleep_ms: COMPLETED_RECHECK_MS,
+                };
+            }
+        } else {
+            *worker.exhausted_streak.lock().await = 0;
+        }
+        if pending > 0 {
+            *worker.cursor.lock().await = None;
+            return CoordinatorTick {
+                sleep_ms: EXHAUSTED_PENDING_RESCAN_MS,
+            };
+        }
+        *worker.cursor.lock().await = None;
+        return CoordinatorTick {
+            sleep_ms: EXHAUSTED_PAUSE_MS,
+        };
+    }
+
+    CoordinatorTick { sleep_ms: TOP_UP_POLL_MS }
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct SyncIdlePayload {
+    server_id: String,
+    ok: bool,
+}
+
+fn on_sync_idle(app: &AppHandle, payload: SyncIdlePayload) {
+    if !payload.ok {
+        return;
+    }
+    let app = app.clone();
+    tauri::async_runtime::spawn(async move {
+        let worker = match app.try_state::<Arc<LibraryAnalysisBackfillWorker>>() {
+            Some(w) => w.inner().clone(),
+            None => return,
+        };
+        if !worker.enabled.load(Ordering::Relaxed) {
+            return;
+        }
+        let session = worker.session.lock().await.clone();
+        let Some(session) = session else {
+            return;
+        };
+        if !session_matches_server(&session, &payload.server_id) {
+            return;
+        }
+        *worker.cursor.lock().await = None;
+        *worker.exhausted_streak.lock().await = 0;
+    });
+}
+
+pub fn setup_library_sync_idle_listener(app: &AppHandle) {
+    let app_handle = app.clone();
+    let _ = app.listen(LibrarySyncProgressPayload::IDLE_EVENT_NAME, move |event| {
+        let Ok(payload) = serde_json::from_str::<SyncIdlePayload>(event.payload()) else {
+            return;
+        };
+        on_sync_idle(&app_handle, payload);
+    });
+}
+
+pub fn spawn_coordinator(app: &AppHandle, worker: Arc<LibraryAnalysisBackfillWorker>) {
+    let app = app.clone();
+    tauri::async_runtime::spawn(async move {
+        run_coordinator_forever(app, worker).await;
+    });
+}

src/api/analysis.ts

@@ -28,12 +28,6 @@ export interface AnalysisPipelineQueueStatsDto {
   cpuDecodeActiveLow: number;
 }
 
-export interface LibraryAnalysisBackfillBatchDto {
-  trackIds: string[];
-  nextCursor: string | null;
-  exhausted: boolean;
-}
-
 export interface LibraryAnalysisProgressDto {
   totalTracks: number;
   pendingTracks: number;
@@ -52,8 +46,6 @@ export interface AnalysisDeleteServerReportDto {
   loudness: number;
 }
 
-export const LIBRARY_ANALYSIS_BACKFILL_BATCH_SIZE = 20;
-
 function serverIndexKeyForId(serverId: string): string {
   const server = useAuthStore.getState().servers.find(s => s.id === serverId);
   if (!server) return serverId;
@@ -68,19 +60,6 @@ export function analysisGetPipelineQueueStats(): Promise<AnalysisPipelineQueueSt
   return invoke<AnalysisPipelineQueueStatsDto>('analysis_get_pipeline_queue_stats');
 }
 
-export function libraryAnalysisBackfillBatch(
-  serverId: string,
-  cursor?: string | null,
-  limit = LIBRARY_ANALYSIS_BACKFILL_BATCH_SIZE,
-): Promise<LibraryAnalysisBackfillBatchDto> {
-  const indexKey = serverIndexKeyForId(serverId);
-  return invoke<LibraryAnalysisBackfillBatchDto>('library_analysis_backfill_batch', {
-    serverId: indexKey,
-    cursor: cursor ?? null,
-    limit,
-  });
-}
-
 export function libraryAnalysisProgress(
   serverId: string,
 ): Promise<LibraryAnalysisProgressDto> {
@@ -157,3 +136,21 @@ export function analysisEnqueueSeedFromUrl(
   const indexKey = serverIndexKeyForId(serverId);
   return invoke('analysis_enqueue_seed_from_url', { trackId, url, serverId: indexKey, priority });
 }
+
+export type LibraryAnalysisBackfillConfigureArgs = {
+  enabled: boolean;
+  serverIndexKey: string;
+  libraryServerId: string;
+  serverUrl: string;
+  username: string;
+  password: string;
+  workers: number;
+};
+
+/** Start/stop native library analysis backfill (advanced strategy only). */
+export function libraryAnalysisBackfillConfigure(
+  args: LibraryAnalysisBackfillConfigureArgs,
+): Promise<void> {
+  // Flat payload — same as `library_cover_backfill_configure` (not `{ args: … }`).
+  return invoke('library_analysis_backfill_configure', args);
+}

src/config/settingsCredits.ts

@@ -135,6 +135,7 @@ const CONTRIBUTOR_ENTRIES = [
       'Albums: combined browse filters (genre/year/favorites/lossless/compilations), session restore from album detail, favorites reconcile via local index (PR #876)',
       'Artist detail: sort albums by year (newest/oldest) in the Albums section (PR #877)',
       'Cover art: Windows thumbnails, tier fallback, PNG decode, Subsonic coverArt id resolution (PR #878)',
+      'Analytics: native advanced library backfill coordinator — UI stays responsive on large libraries (PR #881)',
     ],
   },
   {

src/hooks/useLibraryAnalysisBackfill.ts

@@ -1,64 +1,38 @@
-import { useEffect, useRef } from 'react';
-import { buildStreamUrlForServer } from '../api/subsonicStreamUrl';
+import { useEffect } from 'react';
 import {
-  analysisEnqueueSeedFromUrl,
-  analysisGetPipelineQueueStats,
   analysisSetPipelineParallelism,
-  libraryAnalysisBackfillBatch,
-  libraryCountLiveTracks,
-  libraryAnalysisProgress,
+  libraryAnalysisBackfillConfigure,
 } from '../api/analysis';
+import { librarySqlServerId } from '../api/coverCache';
 import { useAuthStore } from '../store/authStore';
 import { useAnalysisStrategyStore } from '../store/analysisStrategyStore';
 import { DEFAULT_ADVANCED_PARALLELISM } from '../utils/library/analysisStrategy';
-import {
-  libraryBackfillNeedsTopUp,
-  libraryBackfillTopUpLimit,
-} from '../utils/library/libraryAnalysisBackfillPolicy';
-import { libraryIsReady } from '../utils/library/libraryReady';
+import { serverIndexKeyForProfile } from '../utils/server/serverIndexKey';
 
-const TOP_UP_POLL_MS = 500;
-const STEADY_POLL_MS = 2000;
-const READY_POLL_MS = 5000;
-const EXHAUSTED_PAUSE_MS = 15_000;
-const COMPLETED_RECHECK_MS = 5 * 60_000;
-/** Consecutive exhausted scans with zero enqueue before treating the library as done. */
-const EXHAUSTED_DONE_STREAK = 2;
-
-const EMPTY_PIPELINE_STATS = {
-  pipelineWorkers: 1,
-  httpQueued: 0,
-  httpQueuedHigh: 0,
-  httpQueuedMiddle: 0,
-  httpQueuedLow: 0,
-  httpDownloadActive: 0,
-  httpDownloadActiveHigh: 0,
-  httpDownloadActiveMiddle: 0,
-  httpDownloadActiveLow: 0,
-  cpuQueued: 0,
-  cpuQueuedHigh: 0,
-  cpuQueuedMiddle: 0,
-  cpuQueuedLow: 0,
-  cpuDecodeActive: 0,
-  cpuDecodeActiveHigh: 0,
-  cpuDecodeActiveMiddle: 0,
-  cpuDecodeActiveLow: 0,
-};
+const DISABLED_CONFIGURE = {
+  enabled: false,
+  serverIndexKey: '',
+  libraryServerId: '',
+  serverUrl: '',
+  username: '',
+  password: '',
+  workers: DEFAULT_ADVANCED_PARALLELISM,
+} as const;
 
 /**
- * Advanced analytics strategy: keep the HTTP backfill backlog above worker count
- * (watermark target ≈ workers × 3) so parallel downloads stay busy. Library
- * tracks enqueue at low priority; playback tiers stay ahead in Rust.
+ * Advanced analytics strategy: native coordinator in Rust (see `library_analysis_backfill`).
+ * Webview only passes session + worker count — no planning loop or batch IPC.
  */
 export function useLibraryAnalysisBackfill(enabled = true): void {
   const activeServerId = useAuthStore(s => s.activeServerId);
+  const server = useAuthStore(s =>
+    s.activeServerId ? s.servers.find(srv => srv.id === s.activeServerId) : undefined,
+  );
+  const getBaseUrl = useAuthStore(s => s.getBaseUrl);
   const strategy = useAnalysisStrategyStore(s => s.getStrategyForServer(activeServerId));
   const advancedParallelism = useAnalysisStrategyStore(
     s => s.getAdvancedParallelismForServer(activeServerId),
   );
-  const cursorRef = useRef<string | null>(null);
-  const completedTotalRef = useRef<number | null>(null);
-  const exhaustedIdleStreakRef = useRef(0);
 
   useEffect(() => {
     if (!enabled) return;
@@ -68,110 +42,38 @@ export function useLibraryAnalysisBackfill(enabled = true): void {
   }, [strategy, advancedParallelism, enabled]);
 
   useEffect(() => {
-    if (!enabled || strategy !== 'advanced' || !activeServerId) return;
-
-    let cancelled = false;
-    const serverId = activeServerId;
-
-    void (async () => {
-      while (!cancelled) {
-        if (completedTotalRef.current !== null) {
-          const totalTracks = await libraryCountLiveTracks(serverId).catch(() => null);
-          if (!Number.isFinite(totalTracks)) {
-            await new Promise(r => setTimeout(r, COMPLETED_RECHECK_MS));
-            continue;
-          }
-          if (totalTracks === completedTotalRef.current) {
-            await new Promise(r => setTimeout(r, COMPLETED_RECHECK_MS));
-            continue;
-          }
-          completedTotalRef.current = null;
-          cursorRef.current = null;
-          exhaustedIdleStreakRef.current = 0;
-        }
-
-        if (!(await libraryIsReady(serverId))) {
-          await new Promise(r => setTimeout(r, READY_POLL_MS));
-          continue;
-        }
-
-        const workers = advancedParallelism;
-        const stats = await analysisGetPipelineQueueStats().catch(
-          () => EMPTY_PIPELINE_STATS,
-        );
-
-        if (!libraryBackfillNeedsTopUp(stats, workers)) {
-          await new Promise(r => setTimeout(r, STEADY_POLL_MS));
-          continue;
-        }
-
-        const fetchLimit = libraryBackfillTopUpLimit(stats, workers);
-        if (fetchLimit <= 0) {
-          await new Promise(r => setTimeout(r, TOP_UP_POLL_MS));
-          continue;
-        }
-
-        const batch = await libraryAnalysisBackfillBatch(
-          serverId,
-          cursorRef.current,
-          fetchLimit,
-        ).catch(() => null);
-
-        if (!batch || cancelled) {
-          await new Promise(r => setTimeout(r, TOP_UP_POLL_MS));
-          continue;
-        }
-
-        cursorRef.current = batch.nextCursor;
-
-        await Promise.all(
-          batch.trackIds.map(trackId =>
-            analysisEnqueueSeedFromUrl(
-              trackId,
-              buildStreamUrlForServer(serverId, trackId),
-              serverId,
-              'low',
-            ).catch(() => {
-              /* Rust skips completed tracks */
-            }),
-          ),
-        );
-
-        if (cancelled) return;
-
-        if (batch.trackIds.length > 0) {
-          exhaustedIdleStreakRef.current = 0;
-        }
-
-        if (batch.exhausted) {
-          cursorRef.current = null;
-          const progress = await libraryAnalysisProgress(serverId).catch(() => null);
-          const pending = progress?.pendingTracks ?? -1;
-          if (pending <= 0 && batch.trackIds.length === 0) {
-            exhaustedIdleStreakRef.current += 1;
-            if (exhaustedIdleStreakRef.current >= EXHAUSTED_DONE_STREAK && progress) {
-              completedTotalRef.current = progress.totalTracks;
-              await new Promise(r => setTimeout(r, COMPLETED_RECHECK_MS));
-              continue;
-            }
-          } else {
-            exhaustedIdleStreakRef.current = 0;
-          }
-          if (pending > 0) {
-            continue;
-          }
-          await new Promise(r => setTimeout(r, EXHAUSTED_PAUSE_MS));
-        } else if (batch.trackIds.length === 0) {
-          await new Promise(r => setTimeout(r, TOP_UP_POLL_MS));
-        }
-      }
-    })();
-
-    return () => {
-      cancelled = true;
-      cursorRef.current = null;
-      completedTotalRef.current = null;
-      exhaustedIdleStreakRef.current = 0;
+    const disable = () => {
+      void libraryAnalysisBackfillConfigure(DISABLED_CONFIGURE);
     };
-  }, [strategy, activeServerId, advancedParallelism, enabled]);
+
+    if (!enabled || strategy !== 'advanced' || !activeServerId || !server) {
+      disable();
+      return disable;
+    }
+
+    const indexKey = serverIndexKeyForProfile(server);
+    const baseUrl = getBaseUrl();
+    void libraryAnalysisBackfillConfigure({
+      enabled: true,
+      serverIndexKey: indexKey,
+      libraryServerId: librarySqlServerId(activeServerId),
+      serverUrl: baseUrl,
+      username: server.username,
+      password: server.password,
+      workers: advancedParallelism,
+    }).catch(() => {
+      /* coordinator optional; avoid unhandled rejection noise in release */
+    });
+
+    return disable;
+  }, [
+    enabled,
+    strategy,
+    activeServerId,
+    server?.url,
+    server?.username,
+    server?.password,
+    advancedParallelism,
+    getBaseUrl,
+  ]);
 }

src/store/audioListenerSetup/audioEngineListeners.ts

@@ -15,6 +15,7 @@ import {
   hasStableLoudness,
   setCachedLoudnessGain,
 } from '../loudnessGainCache';
+import { isTrackInsideLoudnessBackfillWindow } from '../loudnessBackfillWindow';
 import { refreshLoudnessForTrack } from '../loudnessRefresh';
 import { emitNormalizationDebug } from '../normalizationDebug';
 import {
@@ -96,8 +97,19 @@ export function setupAudioEngineListeners(): () => void {
         emitNormalizationDebug('backfill:applied', { trackId: currentId });
         return;
       }
-      // Backfill finished for another id (e.g. next in queue): refresh loudness cache only
-      // so the cached gain is ready before `audio_play` / gapless chain.
+      // Library aggressive backfill completes thousands of tracks — only warm loudness
+      // for the playback window (current + next N). Skip IPC for the rest.
+      const live = usePlayerStore.getState();
+      if (
+        !isTrackInsideLoudnessBackfillWindow(
+          payloadTrackId,
+          live.queueItems,
+          live.queueIndex,
+          live.currentTrack,
+        )
+      ) {
+        return;
+      }
       void refreshLoudnessForTrack(payloadTrackId, { syncPlayingEngine: false });
       emitNormalizationDebug('backfill:applied', { trackId: payloadTrackId });
     }),

src/utils/library/libraryAnalysisBackfillPolicy.test.ts

@@ -1,48 +0,0 @@
-import { describe, it, expect } from 'vitest';
-import {
-  computeLibraryBackfillTargetDepth,
-  libraryBackfillNeedsTopUp,
-  libraryBackfillPipelineBacklog,
-  libraryBackfillTopUpLimit,
-} from './libraryAnalysisBackfillPolicy';
-
-describe('libraryAnalysisBackfillPolicy', () => {
-  it('targets workers × 3 with floor and cap', () => {
-    expect(computeLibraryBackfillTargetDepth(1)).toBe(8);
-    expect(computeLibraryBackfillTargetDepth(4)).toBe(12);
-    expect(computeLibraryBackfillTargetDepth(8)).toBe(24);
-    expect(computeLibraryBackfillTargetDepth(100)).toBe(240);
-  });
-
-  const zeroCpu = { cpuQueued: 0, cpuDecodeActive: 0 };
-
-  it('measures backlog as HTTP plus CPU seed pipeline load', () => {
-    expect(
-      libraryBackfillPipelineBacklog({
-        httpQueued: 5,
-        httpDownloadActive: 3,
-        ...zeroCpu,
-      }),
-    ).toBe(8);
-    expect(
-      libraryBackfillPipelineBacklog({
-        httpQueued: 0,
-        httpDownloadActive: 0,
-        cpuQueued: 4,
-        cpuDecodeActive: 2,
-      }),
-    ).toBe(6);
-  });
-
-  it('requests top-up while backlog stays below target', () => {
-    const stats = { httpQueued: 2, httpDownloadActive: 1, ...zeroCpu };
-    expect(libraryBackfillNeedsTopUp(stats, 8)).toBe(true);
-    expect(libraryBackfillTopUpLimit(stats, 8)).toBe(20);
-  });
-
-  it('stops top-up when backlog meets target', () => {
-    const stats = { httpQueued: 20, httpDownloadActive: 4, ...zeroCpu };
-    expect(libraryBackfillNeedsTopUp(stats, 8)).toBe(false);
-    expect(libraryBackfillTopUpLimit(stats, 8)).toBe(0);
-  });
-});

src/utils/library/libraryAnalysisBackfillPolicy.ts

@@ -1,41 +0,0 @@
-import type { AnalysisPipelineQueueStatsDto } from '../../api/analysis';
-import { LIBRARY_ANALYSIS_BACKFILL_BATCH_SIZE } from '../../api/analysis';
-
-/** Target backlog ≈ workers × multiplier (min floor, max cap). */
-export const LIBRARY_BACKLOG_DEPTH_MULTIPLIER = 3;
-export const LIBRARY_BACKLOG_MIN = 8;
-export const LIBRARY_BACKLOG_MAX = 240;
-
-export function computeLibraryBackfillTargetDepth(workers: number): number {
-  const w = Math.max(1, Math.round(workers));
-  return Math.min(
-    LIBRARY_BACKLOG_MAX,
-    Math.max(LIBRARY_BACKLOG_MIN, w * LIBRARY_BACKLOG_DEPTH_MULTIPLIER),
-  );
-}
-
-type PipelineBacklogStats = Pick<
-  AnalysisPipelineQueueStatsDto,
-  'httpQueued' | 'httpDownloadActive' | 'cpuQueued' | 'cpuDecodeActive'
->;
-
-/** HTTP + in-flight CPU seed jobs (decode backpressure must not look like an empty pipeline). */
-export function libraryBackfillPipelineBacklog(stats: PipelineBacklogStats): number {
-  return (
-    stats.httpQueued
-    + stats.httpDownloadActive
-    + stats.cpuQueued
-    + stats.cpuDecodeActive
-  );
-}
-
-export function libraryBackfillNeedsTopUp(stats: PipelineBacklogStats, workers: number): boolean {
-  return libraryBackfillPipelineBacklog(stats) < computeLibraryBackfillTargetDepth(workers);
-}
-
-export function libraryBackfillTopUpLimit(stats: PipelineBacklogStats, workers: number): number {
-  const target = computeLibraryBackfillTargetDepth(workers);
-  const deficit = target - libraryBackfillPipelineBacklog(stats);
-  if (deficit <= 0) return 0;
-  return Math.min(LIBRARY_ANALYSIS_BACKFILL_BATCH_SIZE, deficit);
-}