Merge local and federated similarity results

ARCHITECTURE.md

@@ -123,6 +123,22 @@ The DHT is the distributed index. Nodes publish compact searchable
 descriptions of their local library and query the network without contacting a
 central search service.
 
+Similarity discovery uses a separate schema-independent DHT overlay. A node
+derives a deterministic 256-bit routing signature from every local embedding,
+groups them into fixed two-level LSH buckets, and publishes compact summaries
+containing only fine-bucket representatives, its peer identity, and the ticket
+needed to dial a previously unknown owner. The owner signs every summary with
+its existing transport key, so storage peers can relay and cache it but cannot
+impersonate or modify it. Summaries expire with the ordinary library-record TTL
+and are replaceable federation cache, never local library authority.
+
+A similarity search first performs bounded multi-probe LSH lookups to rank
+likely owners, then sends the existing normalized-vector request directly to
+at most 16 peers initially and 48 on fallback. Known peers remain a rollout
+fallback. The model, preprocessing, durable embeddings, exact cosine search,
+and consent policy remain client-owned; `music-dht` owns only compatible
+routing math, signed records, replication, and wire bounds.
+
 Once a peer is known, communication moves to direct P2P streams provided by
 iroh through `music-dht`. Furumi defines separate application protocols for
 catalog requests, audio transfer, and trusted-device synchronization. This

CHANGELOG.md

@@ -20,12 +20,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Track-seeded similarity search from the track-information popup, including
   bounded federated queries to compatible known peers.
 - The `furumi-fd/similarity/1` protocol in the visible protocol-version status.
+- Decentralized `similarity_dht` routing with signed anonymous two-level LSH
+  summaries, multi-probe lookup beyond the locally known peer set, and known-
+  peer fallback during gradual network upgrades.
 
 ### Changed
 
 - Similarity wire types, bounds, validation, and stream framing now come from
-  the shared `music-dht 0.3.1` API so native, web, and future clients can
+  the shared `music-dht 0.4.0` API so native, web, and future clients can
   interoperate without sharing an embedding implementation.
+- Existing SQLite embeddings are backfilled once with compact 256-bit routing
+  signatures; new embeddings store them immediately without changing exact
+  local cosine search.
 - A similarity result page keeps the source track first as query context while
   excluding it from the actual nearest-neighbor ranking, labels the mode as
   `Search similar to`, and suppresses near-identical embeddings across releases

Cargo.lock

@@ -1520,7 +1520,9 @@ dependencies = [
 
 [[package]]
 name = "federation-net"
-version = "0.2.0"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c3e690b370c505d153bef214b21a8f2aa55d667367ac1e16bde8bc0de88963c2"
 dependencies = [
  "blake3",
  "data-encoding",
@@ -1647,7 +1649,7 @@ dependencies = [
 
 [[package]]
 name = "furumi_tui"
-version = "0.2.5"
+version = "0.2.6"
 dependencies = [
  "anyhow",
  "blake3",
@@ -3138,7 +3140,9 @@ dependencies = [
 
 [[package]]
 name = "music-dht"
-version = "0.3.1"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0c5b429b90a8f1b0980b3a35a6fa5445d7a275c737eb04db18db4d7f14c81478"
 dependencies = [
  "async-trait",
  "blake3",

Cargo.toml

@@ -21,7 +21,7 @@ image = { version = "0.25.10", default-features = false, features = ["jpeg", "pn
 lofty = "0.22"
 # P2P federation: library index in a shared DHT + audio streaming between
 # peers (same protocol as furumi-fd).
-music-dht = "0.3.1"
+music-dht = "0.4.0"
 ratatui = "0.30.1"
 reqwest = { version = "0.12.28", default-features = false, features = ["rustls-tls", "stream"] }
 rhai = { version = "1", features = ["sync"] }

README.md

@@ -72,6 +72,9 @@ without rebuilding the player.
 Optional similarity search calculates versioned embeddings for local tracks
 in the background and keeps them in SQLite. It works offline; after a separate
 privacy consent it can also ask a bounded set of federation peers for matches.
+Compatible peers are selected through signed, anonymous LSH summaries in a
+decentralized DHT; no central recommendation index or shared calibration file
+is required.
 The first selectable model is downloaded on demand and is licensed separately
 by MTG under CC BY-NC-SA 4.0 (a proprietary license is also available from
 MTG); Furumi itself remains WTFPL.

src/app/cmdline.rs

@@ -8,7 +8,6 @@ use crate::app::Runtime;
 use crate::app::command::{self, Command, Parsed};
 use crate::app::event::AppEvent;
 use crate::app::state::{AppState, GlobalView, SearchState, Tab};
-use crate::library::models::SearchResults;
 
 const SEARCH_DEBOUNCE: Duration = Duration::from_millis(180);
 const SEARCH_LIMIT: i64 = 12;
@@ -99,6 +98,10 @@ fn set_view_cursor_zero(state: &mut AppState) {
 /// and the receiver drops responses that arrive out of date.
 pub(super) fn schedule_search(state: &mut AppState, runtime: &Runtime) {
     state.search.similarity_source = None;
+    state.search.similarity_source_track = None;
+    state.search.similarity_tracks.clear();
+    state.search.similarity_stats = None;
+    state.search.similarity_error = None;
     let seq = runtime.search_seq.fetch_add(1, Ordering::SeqCst) + 1;
     let query = state.search.query.clone();
     if query.is_empty() {
@@ -160,6 +163,10 @@ pub(super) fn schedule_similarity_search(
         format!("{} — {artist}", track.title)
     };
     state.search.similarity_source = Some(track.id);
+    state.search.similarity_source_track = Some(track.clone());
+    state.search.similarity_tracks.clear();
+    state.search.similarity_stats = None;
+    state.search.similarity_error = None;
     state.search.loading = true;
     state.search.results = None;
     state.search.fed_tracks.clear();
@@ -178,23 +185,10 @@ pub(super) fn schedule_similarity_search(
     let similarity = Arc::clone(&runtime.similarity);
     let tx = runtime.event_tx.clone();
     let track_id = track.id;
-    let source_track = track.clone();
     tokio::task::spawn_blocking(move || {
         let result = similarity
             .search_track(track_id, 49)
-            .map(|(matches, query)| {
-                let mut tracks = Vec::with_capacity(1 + matches.len());
-                tracks.push(source_track);
-                tracks.extend(matches.into_iter().map(|found| found.track));
-                (
-                    SearchResults {
-                        artists: Vec::new(),
-                        releases: Vec::new(),
-                        tracks,
-                    },
-                    query,
-                )
-            });
+            .map(|(matches, query)| (matches, query));
         let (result, query) = match result {
             Ok((results, query)) => (Ok(results), Some(query)),
             Err(err) => (Err(format!("{err:#}")), None),

src/app/event.rs

@@ -36,9 +36,14 @@ pub enum AppEvent {
     /// text search so stale pages cannot overwrite a newer request.
     SimilaritySearchLoaded {
         seq: u64,
-        result: Result<SearchResults, String>,
+        result: Result<Vec<crate::similarity::SimilarTrack>, String>,
         query: Option<crate::similarity::QueryVector>,
     },
+    /// Federated candidates and diagnostics for a track-seeded search.
+    FedSimilaritySearchLoaded {
+        seq: u64,
+        result: Result<crate::federation::FedSimilaritySearchResults, String>,
+    },
     SimilarityStatus(crate::similarity::SimilarityStatus),
     /// `None` is emitted after clearing every stored embedding.
     SimilarityProfileActivated(Option<String>),

src/app/mod.rs

@@ -44,6 +44,10 @@ pub struct Runtime {
     pub similarity: Arc<crate::similarity::Manager>,
     /// When the last Federation-tab status snapshot was requested.
     pub fed_status_at: Option<std::time::Instant>,
+    /// Keeps the last successful local-data snapshot visible while a newer
+    /// one is calculated and collapses bursts of library-change events.
+    pub local_library_stats_refreshing: Arc<std::sync::atomic::AtomicBool>,
+    pub local_library_stats_refresh_requested: Arc<std::sync::atomic::AtomicBool>,
     pub library_network_refresh_at: Option<std::time::Instant>,
     pub library_network_refreshing: Arc<std::sync::atomic::AtomicBool>,
     pub library_network_cursors:
@@ -102,11 +106,35 @@ fn refresh_local_content_ids(runtime: &Runtime) {
 }
 
 fn refresh_local_library_stats(runtime: &Runtime) {
+    runtime
+        .local_library_stats_refresh_requested
+        .store(true, std::sync::atomic::Ordering::Release);
+    if runtime
+        .local_library_stats_refreshing
+        .swap(true, std::sync::atomic::Ordering::AcqRel)
+    {
+        return;
+    }
     let library = Arc::clone(&runtime.library);
     let tx = runtime.event_tx.clone();
+    let refreshing = Arc::clone(&runtime.local_library_stats_refreshing);
+    let requested = Arc::clone(&runtime.local_library_stats_refresh_requested);
     tokio::task::spawn_blocking(move || {
-        let result = library.local_stats().map_err(err_string);
-        let _ = tx.send(AppEvent::LocalLibraryStatsLoaded(result));
+        loop {
+            requested.store(false, std::sync::atomic::Ordering::Release);
+            let result = library.local_stats().map_err(err_string);
+            let _ = tx.send(AppEvent::LocalLibraryStatsLoaded(result));
+            if requested.load(std::sync::atomic::Ordering::Acquire) {
+                continue;
+            }
+            refreshing.store(false, std::sync::atomic::Ordering::Release);
+            if requested.swap(false, std::sync::atomic::Ordering::AcqRel)
+                && !refreshing.swap(true, std::sync::atomic::Ordering::AcqRel)
+            {
+                continue;
+            }
+            break;
+        }
     });
 }
 
@@ -303,6 +331,8 @@ pub async fn run(
         federation,
         similarity,
         fed_status_at: None,
+        local_library_stats_refreshing: Arc::new(std::sync::atomic::AtomicBool::new(false)),
+        local_library_stats_refresh_requested: Arc::new(std::sync::atomic::AtomicBool::new(false)),
         library_network_refresh_at: None,
         library_network_refreshing: Arc::new(std::sync::atomic::AtomicBool::new(false)),
         library_network_cursors: Arc::new(std::sync::Mutex::new(std::collections::HashMap::new())),
@@ -2746,7 +2776,12 @@ fn on_library_changed(state: &mut AppState, runtime: &mut Runtime) {
     // until then.
     state.likes_loaded = false;
     state.local_content_ids_loaded = false;
-    state.local_library_stats = None;
+    // Refresh in place: status cards keep the last successful snapshot
+    // instead of flashing `loading` for every background library event.
+    if state.local_library_stats.is_none() {
+        state.local_library_stats = Some(state::Loadable::Loading);
+    }
+    refresh_local_library_stats(runtime);
 
     // Fresh copies of whatever sits in the queue. Federated placeholders
     // and ephemeral tracks (negative ids) are not library rows and keep
@@ -3313,6 +3348,39 @@ fn handle_app_event(state: &mut AppState, runtime: &mut Runtime, event: AppEvent
                 Err(message) => tracing::warn!(%message, "federated search failed"),
             }
         }
+        AppEvent::FedSimilaritySearchLoaded { seq, result } => {
+            if runtime.search_seq.load(std::sync::atomic::Ordering::SeqCst) != seq {
+                return;
+            }
+            state.search.fed_loading = false;
+            let selected_key = state.global.stack.last().and_then(|view| match view {
+                state::GlobalView::Search { cursor } => state.search.similarity_key(*cursor),
+                _ => None,
+            });
+            match result {
+                Ok(results) => {
+                    let remote = results.tracks.into_iter().map(|hit| {
+                        state::SimilaritySearchHit::Federated {
+                            track: hit.track,
+                            score: hit.score,
+                            embedding_signature: hit.embedding_signature,
+                        }
+                    });
+                    state.search.similarity_tracks.extend(remote);
+                    rank_similarity_search_tracks(
+                        &mut state.search.similarity_tracks,
+                        state.similarity.settings.max_tracks_per_artist,
+                    );
+                    state.search.similarity_stats = Some(results.stats);
+                    state.search.similarity_error = None;
+                }
+                Err(message) => {
+                    tracing::warn!(%message, "federated similarity search failed");
+                    state.search.similarity_error = Some(message);
+                }
+            }
+            restore_similarity_cursor(state, selected_key.as_deref());
+        }
         AppEvent::FedTrackResolved {
             placeholder_id,
             resolve_key,
@@ -3661,7 +3729,20 @@ fn handle_app_event(state: &mut AppState, runtime: &mut Runtime, event: AppEvent
             }
             state.search.loading = false;
             match result {
-                Ok(results) => state.search.results = Some(results),
+                Ok(results) => {
+                    state.search.similarity_tracks = results
+                        .into_iter()
+                        .map(|hit| state::SimilaritySearchHit::Local {
+                            track: hit.track,
+                            score: hit.score,
+                            embedding_signature: hit.embedding_signature,
+                        })
+                        .collect();
+                    rank_similarity_search_tracks(
+                        &mut state.search.similarity_tracks,
+                        state.similarity.settings.max_tracks_per_artist,
+                    );
+                }
                 Err(message) => {
                     state.status_message = Some(format!("similarity search failed: {message}"));
                     return;
@@ -3679,7 +3760,7 @@ fn handle_app_event(state: &mut AppState, runtime: &mut Runtime, event: AppEvent
                         .search_similar(query, 50)
                         .await
                         .map_err(|err| format!("{err:#}"));
-                    let _ = tx.send(AppEvent::FedSearchLoaded { seq, result });
+                    let _ = tx.send(AppEvent::FedSimilaritySearchLoaded { seq, result });
                 });
             }
         }
@@ -3792,15 +3873,17 @@ fn handle_app_event(state: &mut AppState, runtime: &mut Runtime, event: AppEvent
                 tracing::warn!(%message, "local content id load failed");
             }
         },
-        AppEvent::LocalLibraryStatsLoaded(result) => {
-            state.local_library_stats = Some(match result {
-                Ok(stats) => state::Loadable::Ready(stats),
-                Err(message) => {
-                    tracing::warn!(%message, "local library stats load failed");
-                    state::Loadable::Failed(message)
+        AppEvent::LocalLibraryStatsLoaded(result) => match result {
+            Ok(stats) => {
+                state.local_library_stats = Some(state::Loadable::Ready(stats));
+            }
+            Err(message) => {
+                tracing::warn!(%message, "local library stats load failed");
+                if !matches!(state.local_library_stats, Some(state::Loadable::Ready(_))) {
+                    state.local_library_stats = Some(state::Loadable::Failed(message));
                 }
-            });
-        }
+            }
+        },
         AppEvent::LocalContentAvailable { content_id } => {
             if let Some(content_id) = music_dht::normalize_content_id(&content_id) {
                 state.local_content_ids.insert(content_id);
@@ -3970,6 +4053,135 @@ fn handle_app_event(state: &mut AppState, runtime: &mut Runtime, event: AppEvent
     }
 }
 
+fn rank_similarity_search_tracks(
+    tracks: &mut Vec<state::SimilaritySearchHit>,
+    max_tracks_per_artist: usize,
+) {
+    const RESULT_LIMIT: usize = 49;
+    const MAX_NEAR_DUPLICATE_SIGNATURE_DISTANCE: u32 = 8;
+
+    tracks.sort_by(|left, right| right.score().total_cmp(&left.score()));
+    let candidates = std::mem::take(tracks);
+    let mut content = std::collections::HashSet::new();
+    let mut signatures = Vec::new();
+    let mut artist_counts: std::collections::HashMap<String, usize> = Default::default();
+    for hit in candidates {
+        if !content.insert(hit.content_key()) {
+            continue;
+        }
+        if hit.embedding_signature().is_some_and(|candidate| {
+            signatures.iter().any(|existing| {
+                music_dht::similarity::signature_distance(&candidate, existing)
+                    <= MAX_NEAR_DUPLICATE_SIGNATURE_DISTANCE
+            })
+        }) {
+            continue;
+        }
+        let artist = hit.primary_artist_key();
+        let count = artist_counts.entry(artist.clone()).or_default();
+        if !artist.is_empty() && *count >= max_tracks_per_artist.clamp(1, RESULT_LIMIT) {
+            continue;
+        }
+        *count += 1;
+        if let Some(signature) = hit.embedding_signature() {
+            signatures.push(signature);
+        }
+        tracks.push(hit);
+        if tracks.len() >= RESULT_LIMIT {
+            break;
+        }
+    }
+}
+
+fn restore_similarity_cursor(state: &mut AppState, selected_key: Option<&str>) {
+    let selected_index = selected_key.and_then(|key| state.search.similarity_index_for_key(key));
+    let len = state.search.similarity_len();
+    if let Some(state::GlobalView::Search { cursor }) = state.global.stack.last_mut() {
+        *cursor = selected_index.unwrap_or(*cursor).min(len.saturating_sub(1));
+    }
+}
+
+#[cfg(test)]
+mod similarity_search_tests {
+    use super::*;
+    use crate::library::models::{ArtistRef, TrackItem};
+
+    fn local_hit(id: i64, artist: &str, score: f32, signature: u8) -> state::SimilaritySearchHit {
+        state::SimilaritySearchHit::Local {
+            track: TrackItem {
+                id,
+                title: format!("local {id}"),
+                track_number: None,
+                disc_number: None,
+                duration_seconds: 1.0,
+                artists: vec![ArtistRef {
+                    id,
+                    name: artist.to_string(),
+                }],
+                featured_artists: Vec::new(),
+                release_id: id,
+                release_title: "release".to_string(),
+                release_year: None,
+                file_path: format!("/music/{id}"),
+                content_id: Some(format!("local-{id}")),
+                cover_path: None,
+                audio_format: None,
+                audio_bitrate: None,
+                audio_sample_rate: None,
+                audio_bit_depth: None,
+                file_size_bytes: None,
+                play_count: 0,
+                fed: None,
+            },
+            score,
+            embedding_signature: [signature; music_dht::similarity::SIMILARITY_SIGNATURE_BYTES],
+        }
+    }
+
+    fn remote_hit(artist: &str, score: f32, signature: u8) -> state::SimilaritySearchHit {
+        state::SimilaritySearchHit::Federated {
+            track: crate::federation::FedTrack {
+                item_id: format!("remote-{signature}"),
+                owner: "peer".to_string(),
+                own: false,
+                title: format!("remote {signature}"),
+                artist_names: vec![artist.to_string()],
+                featured_artist_names: Vec::new(),
+                year: None,
+                duration_seconds: Some(1),
+                content_id: Some(format!("remote-{signature}")),
+                release_title: None,
+                track_number: None,
+                disc_number: None,
+            },
+            score,
+            embedding_signature: Some(
+                [signature; music_dht::similarity::SIMILARITY_SIGNATURE_BYTES],
+            ),
+        }
+    }
+
+    #[test]
+    fn similarity_results_rank_local_and_remote_together_with_one_artist_cap() {
+        let mut tracks = vec![
+            local_hit(1, "same artist", 0.70, 1),
+            remote_hit("other artist", 0.90, 2),
+            remote_hit("same artist", 0.80, 3),
+            local_hit(2, "same artist", 0.60, 4),
+        ];
+
+        rank_similarity_search_tracks(&mut tracks, 1);
+
+        assert_eq!(tracks.len(), 2);
+        assert_eq!(tracks[0].score(), 0.90);
+        assert_eq!(tracks[1].score(), 0.80);
+        assert!(matches!(
+            tracks[0],
+            state::SimilaritySearchHit::Federated { .. }
+        ));
+    }
+}
+
 /// Mirror the playback state to the OS now-playing surface. `force` skips
 /// the position throttle (track switches, pauses).
 fn push_media_update(state: &AppState, runtime: &mut Runtime, force: bool) {

src/app/popup.rs

@@ -592,6 +592,36 @@ fn handle_fed_input(
                         state.popup = Some(Popup::FedInput { field, input });
                     }
                 },
+                FedInputField::SimilarityMinimumScore => match value.parse::<f32>() {
+                    Ok(score) if score.is_finite() && (0.0..=1.0).contains(&score) => {
+                        state.similarity.settings.minimum_score = score;
+                        super::perform_effect(
+                            state,
+                            runtime,
+                            crate::app::update::Effect::SimilarityApplySettings,
+                        );
+                    }
+                    _ => {
+                        state.status_message =
+                            Some("minimum similarity must be a number from 0.00 to 1.00".into());
+                        state.popup = Some(Popup::FedInput { field, input });
+                    }
+                },
+                FedInputField::SimilarityMaxTracksPerArtist => match value.parse::<usize>() {
+                    Ok(limit @ 1..=50) => {
+                        state.similarity.settings.max_tracks_per_artist = limit;
+                        super::perform_effect(
+                            state,
+                            runtime,
+                            crate::app::update::Effect::SimilarityApplySettings,
+                        );
+                    }
+                    _ => {
+                        state.status_message =
+                            Some("tracks per artist must be a number from 1 to 50".into());
+                        state.popup = Some(Popup::FedInput { field, input });
+                    }
+                },
                 FedInputField::ConnectTicket => {
                     if value.is_empty() {
                         state.status_message = Some("ticket is empty".into());

src/app/state.rs

@@ -509,6 +509,8 @@ pub enum TrackSelectionScope {
     Release(i64),
     Playlist(i64),
     Queue,
+    /// The unified local + federated similar-track result list.
+    SimilaritySearch,
     /// The federated section of the search results (its tracks).
     FedSearch,
     /// The tracklist of the open federated release view.
@@ -817,6 +819,8 @@ impl StatusDetailFocus {
 pub enum FedInputField {
     MusicDirectory,
     SimilarityWorkers,
+    SimilarityMinimumScore,
+    SimilarityMaxTracksPerArtist,
     NetworkId,
     ConnectTicket,
     DeviceName,
@@ -829,6 +833,8 @@ impl FedInputField {
         match self {
             FedInputField::MusicDirectory => "Music save directory",
             FedInputField::SimilarityWorkers => "Similarity background workers",
+            FedInputField::SimilarityMinimumScore => "Minimum similarity score",
+            FedInputField::SimilarityMaxTracksPerArtist => "Tracks per artist",
             FedInputField::NetworkId => "Network ID",
             FedInputField::ConnectTicket => "Connect to peer (paste ticket)",
             FedInputField::DeviceName => "Device name",
@@ -845,6 +851,12 @@ impl FedInputField {
             FedInputField::SimilarityWorkers => {
                 "Enter the maximum number of tracks processed in parallel, from 1 to 16. The change takes effect immediately."
             }
+            FedInputField::SimilarityMinimumScore => {
+                "Enter the minimum cosine similarity from 0.00 to 1.00. Lower values show broader matches; higher values hide weak matches. Embeddings are not recalculated."
+            }
+            FedInputField::SimilarityMaxTracksPerArtist => {
+                "Enter how many tracks by one primary artist may appear in similarity results, from 1 to 50. Embeddings are not recalculated."
+            }
             FedInputField::NetworkId => {
                 "A unique network id. It must match exactly on every client that should see and connect to the same peers."
             }
@@ -880,15 +892,19 @@ pub enum SimilarityRow {
     Toggle,
     Model,
     Profile,
+    MinimumScore,
+    MaxTracksPerArtist,
     Workers,
     Clear,
 }
 
 impl SimilarityRow {
-    pub const ALL: [SimilarityRow; 5] = [
+    pub const ALL: [SimilarityRow; 7] = [
         SimilarityRow::Toggle,
         SimilarityRow::Model,
         SimilarityRow::Profile,
+        SimilarityRow::MinimumScore,
+        SimilarityRow::MaxTracksPerArtist,
         SimilarityRow::Workers,
         SimilarityRow::Clear,
     ];
@@ -1211,6 +1227,85 @@ mod cmdline_history_tests {
 }
 
 /// Live search state driven by the `:/query` command.
+#[derive(Debug, Clone)]
+pub enum SimilaritySearchHit {
+    Local {
+        track: TrackItem,
+        score: f32,
+        embedding_signature: [u8; music_dht::similarity::SIMILARITY_SIGNATURE_BYTES],
+    },
+    Federated {
+        track: crate::federation::FedTrack,
+        score: f32,
+        embedding_signature: Option<[u8; music_dht::similarity::SIMILARITY_SIGNATURE_BYTES]>,
+    },
+}
+
+impl SimilaritySearchHit {
+    pub fn score(&self) -> f32 {
+        match self {
+            Self::Local { score, .. } | Self::Federated { score, .. } => *score,
+        }
+    }
+
+    pub fn embedding_signature(
+        &self,
+    ) -> Option<[u8; music_dht::similarity::SIMILARITY_SIGNATURE_BYTES]> {
+        match self {
+            Self::Local {
+                embedding_signature,
+                ..
+            } => Some(*embedding_signature),
+            Self::Federated {
+                embedding_signature,
+                ..
+            } => *embedding_signature,
+        }
+    }
+
+    pub fn track_item(&self) -> TrackItem {
+        match self {
+            Self::Local { track, .. } => track.clone(),
+            Self::Federated { track, .. } => crate::federation::pending_track(track),
+        }
+    }
+
+    pub fn federated_track(&self) -> Option<&crate::federation::FedTrack> {
+        match self {
+            Self::Federated { track, .. } => Some(track),
+            Self::Local { .. } => None,
+        }
+    }
+
+    pub fn primary_artist_key(&self) -> String {
+        match self {
+            Self::Local { track, .. } => track
+                .artists
+                .first()
+                .map(|artist| music_dht::normalize_name(&artist.name))
+                .unwrap_or_default(),
+            Self::Federated { track, .. } => track
+                .artist_names
+                .first()
+                .map(|artist| music_dht::normalize_name(artist))
+                .unwrap_or_default(),
+        }
+    }
+
+    pub fn content_key(&self) -> String {
+        match self {
+            Self::Local { track, .. } => track
+                .content_id
+                .clone()
+                .unwrap_or_else(|| format!("local:{}", track.id)),
+            Self::Federated { track, .. } => track
+                .content_id
+                .clone()
+                .unwrap_or_else(|| format!("remote:{}:{}", track.owner, track.item_id)),
+        }
+    }
+}
+
 #[derive(Debug, Default)]
 pub struct SearchState {
     pub query: String,
@@ -1226,6 +1321,59 @@ pub struct SearchState {
     /// Present only for a track-seeded search; text-search refreshes must not
     /// replace this page with a title query.
     pub similarity_source: Option<i64>,
+    /// The source is pinned at row zero; candidates below it are globally
+    /// ranked across the local library and federation.
+    pub similarity_source_track: Option<TrackItem>,
+    pub similarity_tracks: Vec<SimilaritySearchHit>,
+    pub similarity_stats: Option<crate::federation::SimilaritySearchStats>,
+    pub similarity_error: Option<String>,
+}
+
+impl SearchState {
+    pub fn similarity_len(&self) -> usize {
+        usize::from(self.similarity_source_track.is_some()) + self.similarity_tracks.len()
+    }
+
+    pub fn similarity_track(&self, index: usize) -> Option<TrackItem> {
+        if index == 0 {
+            return self.similarity_source_track.clone();
+        }
+        self.similarity_tracks
+            .get(index.checked_sub(1)?)
+            .map(SimilaritySearchHit::track_item)
+    }
+
+    pub fn similarity_fed_track(&self, index: usize) -> Option<&crate::federation::FedTrack> {
+        self.similarity_tracks
+            .get(index.checked_sub(1)?)?
+            .federated_track()
+    }
+
+    pub fn similarity_key(&self, index: usize) -> Option<String> {
+        if index == 0 {
+            return self
+                .similarity_source_track
+                .as_ref()
+                .map(|track| format!("source:{}", track.id));
+        }
+        self.similarity_tracks
+            .get(index.checked_sub(1)?)
+            .map(SimilaritySearchHit::content_key)
+    }
+
+    pub fn similarity_index_for_key(&self, key: &str) -> Option<usize> {
+        if self
+            .similarity_source_track
+            .as_ref()
+            .is_some_and(|track| key == format!("source:{}", track.id))
+        {
+            return Some(0);
+        }
+        self.similarity_tracks
+            .iter()
+            .position(|hit| hit.content_key() == key)
+            .map(|index| index + 1)
+    }
 }
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]

src/app/update.rs

@@ -905,6 +905,9 @@ fn set_track_scope_cursor(state: &mut AppState, scope: &TrackSelectionScope, val
         TrackSelectionScope::Queue => {
             state.queue_tab.cursor = value;
         }
+        TrackSelectionScope::SimilaritySearch => {
+            set_view_cursor(state, value);
+        }
         TrackSelectionScope::FedSearch => {
             let base = state.search.results.as_ref().map_or(0, |r| r.len())
                 + state.search.fed_artists.len();
@@ -952,6 +955,14 @@ fn current_track_list_context(state: &AppState) -> Option<(TrackSelectionScope,
                 _ => None,
             },
             GlobalView::Search { cursor } => {
+                if state.search.similarity_source.is_some() {
+                    let len = state.search.similarity_len();
+                    return (*cursor < len).then_some((
+                        TrackSelectionScope::SimilaritySearch,
+                        *cursor,
+                        len,
+                    ));
+                }
                 // Only the federated tracks section is selectable here.
                 let base = state.search.results.as_ref().map_or(0, |r| r.len())
                     + state.search.fed_artists.len();
@@ -1044,6 +1055,20 @@ fn current_track_list(state: &AppState) -> Option<(TrackSelectionScope, usize, V
 }
 
 pub fn selected_tracks(state: &AppState) -> Vec<TrackItem> {
+    if state.active_tab == Tab::Global
+        && state.search.similarity_source.is_some()
+        && let Some(GlobalView::Search { cursor }) = state.global.stack.last()
+    {
+        let len = state.search.similarity_len();
+        let indices = state
+            .track_selection
+            .indices(&TrackSelectionScope::SimilaritySearch, len)
+            .unwrap_or_else(|| vec![(*cursor).min(len.saturating_sub(1))]);
+        return indices
+            .into_iter()
+            .filter_map(|index| state.search.similarity_track(index))
+            .collect();
+    }
     // Federated contexts produce queueable placeholders that behave like
     // regular tracks (queue, info, playback-on-demand).
     {
@@ -1276,6 +1301,9 @@ pub fn selected_track(state: &AppState) -> Option<TrackItem> {
                 _ => None,
             },
             GlobalView::Search { cursor } => {
+                if state.search.similarity_source.is_some() {
+                    return state.search.similarity_track(*cursor);
+                }
                 let results = state.search.results.as_ref()?;
                 let offset = cursor.checked_sub(results.artists.len() + results.releases.len())?;
                 match results.tracks.get(offset) {
@@ -1877,10 +1905,13 @@ fn move_selection(state: &mut AppState, dx: isize, dy: isize) {
             refresh_track_selection_cursor(state);
         }
         Some(GlobalView::Search { cursor }) => {
-            // Local results plus the federated section below them.
-            let total = (state.search.results.as_ref().map_or(0, |r| r.len())
-                + state.search.fed_artists.len()
-                + state.search.fed_tracks.len()) as isize;
+            let total = if state.search.similarity_source.is_some() {
+                state.search.similarity_len()
+            } else {
+                state.search.results.as_ref().map_or(0, |r| r.len())
+                    + state.search.fed_artists.len()
+                    + state.search.fed_tracks.len()
+            } as isize;
             if total == 0 {
                 return;
             }
@@ -2000,9 +2031,13 @@ fn current_view_len(state: &AppState) -> usize {
             _ => 0,
         },
         Some(GlobalView::Search { .. }) => {
-            state.search.results.as_ref().map_or(0, |r| r.len())
-                + state.search.fed_artists.len()
-                + state.search.fed_tracks.len()
+            if state.search.similarity_source.is_some() {
+                state.search.similarity_len()
+            } else {
+                state.search.results.as_ref().map_or(0, |r| r.len())
+                    + state.search.fed_artists.len()
+                    + state.search.fed_tracks.len()
+            }
         }
         Some(GlobalView::FedArtist { .. }) => fed_card_len(state),
         Some(GlobalView::FedRelease { index, .. }) => fed_card_release(state, *index)
@@ -2292,31 +2327,47 @@ fn select_current(state: &mut AppState) -> Option<Effect> {
             },
             _ => Outcome::Nothing,
         },
-        Some(GlobalView::Search { cursor }) => match &state.search.results {
-            Some(results) => {
-                let artists = results.artists.len();
-                let releases = results.releases.len();
-                if cursor < artists {
-                    Outcome::Push(GlobalView::Artist {
-                        id: results.artists[cursor].id,
-                        cursor: 0,
-                    })
-                } else if cursor < artists + releases {
-                    Outcome::Push(GlobalView::Release {
-                        id: results.releases[cursor - artists].id,
-                        cursor: 0,
-                    })
-                } else if results.tracks.get(cursor - artists - releases).is_some() {
-                    Outcome::Play {
-                        tracks: results.tracks.clone(),
-                        start: cursor - artists - releases,
-                    }
+        Some(GlobalView::Search { cursor }) => {
+            if state.search.similarity_source.is_some() {
+                let tracks = (0..state.search.similarity_len())
+                    .filter_map(|index| state.search.similarity_track(index))
+                    .collect::<Vec<_>>();
+                if tracks.is_empty() {
+                    Outcome::Nothing
                 } else {
-                    fed_outcome(state, cursor - artists - releases - results.tracks.len())
+                    Outcome::Play {
+                        start: cursor.min(tracks.len() - 1),
+                        tracks,
+                    }
+                }
+            } else {
+                match &state.search.results {
+                    Some(results) => {
+                        let artists = results.artists.len();
+                        let releases = results.releases.len();
+                        if cursor < artists {
+                            Outcome::Push(GlobalView::Artist {
+                                id: results.artists[cursor].id,
+                                cursor: 0,
+                            })
+                        } else if cursor < artists + releases {
+                            Outcome::Push(GlobalView::Release {
+                                id: results.releases[cursor - artists].id,
+                                cursor: 0,
+                            })
+                        } else if results.tracks.get(cursor - artists - releases).is_some() {
+                            Outcome::Play {
+                                tracks: results.tracks.clone(),
+                                start: cursor - artists - releases,
+                            }
+                        } else {
+                            fed_outcome(state, cursor - artists - releases - results.tracks.len())
+                        }
+                    }
+                    None => fed_outcome(state, cursor),
                 }
             }
-            None => fed_outcome(state, cursor),
-        },
+        }
         Some(GlobalView::FedArtist { cursor }) => match &state.fed_artist_view {
             Some((_, Loadable::Ready(card))) => {
                 let release_indices = fed_artist_visible_release_indices(state, card);
@@ -2492,6 +2543,20 @@ pub(crate) fn selected_fed_tracks(state: &AppState) -> Vec<crate::federation::Fe
     if state.active_tab != Tab::Global {
         return Vec::new();
     }
+    if state.search.similarity_source.is_some()
+        && let Some(GlobalView::Search { cursor }) = state.global.stack.last()
+    {
+        let scope = TrackSelectionScope::SimilaritySearch;
+        let len = state.search.similarity_len();
+        let indices = state
+            .track_selection
+            .indices(&scope, len)
+            .unwrap_or_else(|| vec![(*cursor).min(len.saturating_sub(1))]);
+        return indices
+            .into_iter()
+            .filter_map(|index| state.search.similarity_fed_track(index).cloned())
+            .collect();
+    }
     // An active Shift-V range in a federated scope.
     if let Some(scope) = state.track_selection.scope.clone() {
         match scope {
@@ -2796,6 +2861,25 @@ fn federation_select(state: &mut AppState) -> Option<Effect> {
             });
             None
         }
+        SettingsRow::Similarity(SimilarityRow::MinimumScore) => {
+            state.popup = Some(Popup::FedInput {
+                field: FedInputField::SimilarityMinimumScore,
+                input: crate::app::input::LineEdit::new(format!(
+                    "{:.2}",
+                    state.similarity.settings.minimum_score
+                )),
+            });
+            None
+        }
+        SettingsRow::Similarity(SimilarityRow::MaxTracksPerArtist) => {
+            state.popup = Some(Popup::FedInput {
+                field: FedInputField::SimilarityMaxTracksPerArtist,
+                input: crate::app::input::LineEdit::new(
+                    state.similarity.settings.max_tracks_per_artist.to_string(),
+                ),
+            });
+            None
+        }
         SettingsRow::Similarity(SimilarityRow::Workers) => {
             state.popup = Some(Popup::FedInput {
                 field: FedInputField::SimilarityWorkers,

src/config/settings.rs

@@ -45,7 +45,7 @@ pub struct LibraryFilters {
     pub source_mode: LibrarySourceMode,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct SimilaritySettings {
     /// Local embedding/search master switch. Network participation follows
     /// federation and additionally requires the explicit privacy consent.
@@ -57,6 +57,14 @@ pub struct SimilaritySettings {
     pub profile: String,
     #[serde(default = "default_similarity_workers")]
     pub workers: usize,
+    /// Requester-side cosine score floor. This is search policy, not part of
+    /// the embedding profile, so changing it never invalidates vectors.
+    #[serde(default = "default_similarity_minimum_score")]
+    pub minimum_score: f32,
+    /// Requester-side diversity cap applied independently to local and
+    /// federated candidates.
+    #[serde(default = "default_similarity_max_tracks_per_artist")]
+    pub max_tracks_per_artist: usize,
     #[serde(default)]
     pub federation_consent: bool,
     /// Exact fingerprint of the last fully usable profile. Keeping this
@@ -73,13 +81,15 @@ impl Default for SimilaritySettings {
             model: default_similarity_model(),
             profile: default_similarity_profile(),
             workers: default_similarity_workers(),
+            minimum_score: default_similarity_minimum_score(),
+            max_tracks_per_artist: default_similarity_max_tracks_per_artist(),
             federation_consent: false,
             active_profile: None,
         }
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct AppSettings {
     #[serde(default = "default_volume")]
     pub volume: u8,
@@ -116,6 +126,11 @@ impl AppSettings {
             self.similarity.profile = default_similarity_profile();
         }
         self.similarity.workers = self.similarity.workers.clamp(1, 16);
+        if !self.similarity.minimum_score.is_finite() {
+            self.similarity.minimum_score = default_similarity_minimum_score();
+        }
+        self.similarity.minimum_score = self.similarity.minimum_score.clamp(0.0, 1.0);
+        self.similarity.max_tracks_per_artist = self.similarity.max_tracks_per_artist.clamp(1, 50);
         self
     }
 }
@@ -138,6 +153,14 @@ fn default_similarity_workers() -> usize {
         .unwrap_or(1)
 }
 
+fn default_similarity_minimum_score() -> f32 {
+    0.70
+}
+
+fn default_similarity_max_tracks_per_artist() -> usize {
+    5
+}
+
 /// The historical permanent-download location, kept as the default for
 /// backward compatibility with existing installations.
 pub fn default_music_dir() -> PathBuf {
@@ -204,5 +227,21 @@ hide_featured_only = true
         assert!(settings.library.hide_featured_only);
         assert_eq!(settings.library.source_mode, LibrarySourceMode::Global);
         assert_eq!(settings.music_dir, default_music_dir());
+        assert_eq!(settings.similarity.minimum_score, 0.70);
+        assert_eq!(settings.similarity.max_tracks_per_artist, 5);
+    }
+
+    #[test]
+    fn similarity_search_policy_is_normalized_without_changing_the_profile() {
+        let mut settings = AppSettings::default();
+        let profile = settings.similarity.profile.clone();
+        settings.similarity.minimum_score = f32::NAN;
+        settings.similarity.max_tracks_per_artist = 0;
+
+        let settings = settings.normalized();
+
+        assert_eq!(settings.similarity.minimum_score, 0.70);
+        assert_eq!(settings.similarity.max_tracks_per_artist, 1);
+        assert_eq!(settings.similarity.profile, profile);
     }
 }

src/federation/capabilities.rs

@@ -171,6 +171,7 @@ mod tests {
             "catalog",
             "audio",
             "similarity",
+            "similarity_dht",
             "device_sync",
             "jam",
         ] {

src/federation/mod.rs

@@ -25,6 +25,8 @@ use std::sync::atomic::{AtomicI64, Ordering};
 use std::time::Duration;
 
 use anyhow::{Context, Result};
+use music_dht::similarity_dht::SimilarityDht;
+use music_dht::similarity_lsh::SIMILARITY_DHT_ALPN;
 use music_dht::{
     ByteStream, ByteStreamConnectionStats, EndpointId, ItemKind, ItemSpec, LibraryItem,
     MusicDhtConfig, MusicDhtService, NetworkId, PeerTicket, PublishStats, RendezvousConfig,
@@ -336,6 +338,27 @@ pub struct FedSearchResults {
     pub tracks: Vec<FedTrack>,
 }
 
+#[derive(Debug, Clone)]
+pub struct ScoredFedTrack {
+    pub track: FedTrack,
+    pub score: f32,
+    pub embedding_signature: Option<[u8; music_dht::similarity::SIMILARITY_SIGNATURE_BYTES]>,
+}
+
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub struct SimilaritySearchStats {
+    pub tracks: usize,
+    pub artists: usize,
+    pub peers_queried: usize,
+    pub elapsed_ms: u64,
+}
+
+#[derive(Debug, Clone, Default)]
+pub struct FedSimilaritySearchResults {
+    pub tracks: Vec<ScoredFedTrack>,
+    pub stats: SimilaritySearchStats,
+}
+
 /// A track found through federated search.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FedTrack {
@@ -413,6 +436,7 @@ pub struct NetworkLibrarySource {
 
 struct Running {
     service: Arc<MusicDhtService>,
+    similarity_dht: Arc<SimilarityDht>,
     network_name: String,
     network_id: NetworkId,
     tasks: Vec<tokio::task::JoinHandle<()>>,
@@ -697,12 +721,15 @@ impl Federation {
             .stream_protocol(AUDIO_ALPN)
             // ...and browse each other's per-artist catalogs over this one.
             .stream_protocol(CATALOG_ALPN)
-            // Anonymous, bounded direct embedding queries.
-            .stream_protocol(SIMILARITY_ALPN)
+            // Anonymous, bounded direct embedding queries have their own
+            // versioned contract and survive catalog-schema upgrades.
+            .schema_independent_stream_protocol(SIMILARITY_ALPN)
             // Personal-device sync (likes, playlists, trusted devices).
             .stream_protocol(crate::devices::SYNC_ALPN)
             // Capability-scoped shared playback control.
             .stream_protocol(crate::jam::JAM_ALPN)
+            // Signed LSH summaries form their own upgrade-safe DHT overlay.
+            .schema_independent_stream_protocol(SIMILARITY_DHT_ALPN)
             // Informational application/protocol versions.
             .schema_independent_stream_protocol(capabilities::CAPABILITIES_ALPN)
             .build()
@@ -717,6 +744,25 @@ impl Federation {
             "federation started"
         );
 
+        let similarity_dht = SimilarityDht::open(
+            Arc::clone(&service),
+            self.data_dir.join("similarity-routing.sqlite3"),
+        )
+        .await
+        .map_err(|err| anyhow::anyhow!("failed to start the similarity DHT: {err}"))?;
+        let similarity_dht_acceptor = service
+            .stream_acceptor(SIMILARITY_DHT_ALPN)
+            .map_err(|err| anyhow::anyhow!("failed to take similarity DHT acceptor: {err}"))?;
+        let similarity_dht_serve_task =
+            tokio::spawn(Arc::clone(&similarity_dht).serve(similarity_dht_acceptor));
+        let similarity_dht_maintenance_task =
+            tokio::spawn(Arc::clone(&similarity_dht).maintenance());
+        let similarity_dht_sync_task = tokio::spawn(similarity_route_sync_loop(
+            Arc::clone(&similarity_dht),
+            Arc::clone(&self.similarity),
+            Arc::clone(&self.library),
+        ));
+
         // Drain DHT events into the log; the channel is bounded.
         let event_task = tokio::spawn(async move {
             while let Some(event) = events.recv().await {
@@ -797,6 +843,7 @@ impl Federation {
 
         *guard = Some(Running {
             service,
+            similarity_dht,
             network_name,
             network_id,
             tasks: vec![
@@ -811,6 +858,9 @@ impl Federation {
                 jam_poll_task,
                 capabilities_serve_task,
                 capabilities_probe_task,
+                similarity_dht_serve_task,
+                similarity_dht_maintenance_task,
+                similarity_dht_sync_task,
             ],
         });
         self.set_error(None);
@@ -835,6 +885,20 @@ impl Federation {
             .context("federation is not running")
     }
 
+    async fn similarity_services(&self) -> Result<(Arc<MusicDhtService>, Arc<SimilarityDht>)> {
+        self.running
+            .lock()
+            .await
+            .as_ref()
+            .map(|running| {
+                (
+                    Arc::clone(&running.service),
+                    Arc::clone(&running.similarity_dht),
+                )
+            })
+            .context("federation is not running")
+    }
+
     fn ensure_connected_devices_enabled(&self) -> Result<()> {
         let settings = self.settings();
         anyhow::ensure!(
@@ -1170,13 +1234,22 @@ impl Federation {
         &self,
         query: crate::similarity::QueryVector,
         limit: usize,
-    ) -> Result<FedSearchResults> {
+    ) -> Result<FedSimilaritySearchResults> {
         anyhow::ensure!(
             self.similarity.network_allowed(),
             "similarity federation has no consent"
         );
-        let service = self.service().await?;
-        similarity::search(service, query, limit, Arc::clone(&self.transport_stats)).await
+        let (service, similarity_dht) = self.similarity_services().await?;
+        let settings = self.similarity.settings();
+        similarity::search(
+            service,
+            similarity_dht,
+            query,
+            limit,
+            settings.minimum_score,
+            Arc::clone(&self.transport_stats),
+        )
+        .await
     }
 
     /// Resolves a share-link content id to one playable federated track.
@@ -2565,6 +2638,77 @@ fn sort_fed_appearances(appearances: &mut [FedAppearsOn]) {
     });
 }
 
+async fn similarity_route_sync_loop(
+    routing: Arc<SimilarityDht>,
+    similarity: Arc<crate::similarity::Manager>,
+    library: Arc<Library>,
+) {
+    let mut interval = tokio::time::interval(SYNC_INTERVAL);
+    interval.set_missed_tick_behavior(tokio::time::MissedTickBehavior::Skip);
+    let mut published_marker: Option<(String, blake3::Hash)> = None;
+    loop {
+        interval.tick().await;
+        if !similarity.network_allowed() {
+            if published_marker.take().is_some() {
+                routing.clear_local_signatures();
+                tracing::info!("local similarity DHT publication disabled");
+            }
+            continue;
+        }
+        let status = similarity.status();
+        let Some(profile_id) = status.active_profile else {
+            continue;
+        };
+        if status.phase != crate::similarity::Phase::Ready {
+            continue;
+        }
+        let library = Arc::clone(&library);
+        let profile_for_task = profile_id.clone();
+        let loaded = tokio::task::spawn_blocking(move || {
+            let signatures = library.similarity_routing_signatures(&profile_for_task)?;
+            let mut hasher = blake3::Hasher::new();
+            for signature in &signatures {
+                hasher.update(signature);
+            }
+            Ok::<_, anyhow::Error>((signatures, hasher.finalize()))
+        })
+        .await;
+        let (signatures, fingerprint) = match loaded {
+            Ok(Ok(loaded)) => loaded,
+            Ok(Err(error)) => {
+                tracing::warn!(%error, %profile_id, "similarity routing signatures unavailable");
+                continue;
+            }
+            Err(error) => {
+                tracing::warn!(%error, "similarity routing signature task failed");
+                continue;
+            }
+        };
+        let marker = (profile_id.clone(), fingerprint);
+        if published_marker.as_ref() == Some(&marker) {
+            continue;
+        }
+        match routing
+            .sync_local_signatures(profile_id.clone(), signatures)
+            .await
+        {
+            Ok(stats) => {
+                tracing::info!(
+                    profile = %profile_id,
+                    records = stats.records,
+                    keys = stats.keys,
+                    remote_nodes = stats.remote_nodes,
+                    "local similarity DHT index synchronized"
+                );
+                published_marker = Some(marker);
+            }
+            Err(error) => {
+                tracing::warn!(%error, %profile_id, "similarity DHT synchronization failed");
+            }
+        }
+    }
+}
+
 async fn stop_running(running: Option<Running>) {
     let Some(running) = running else { return };
     for task in &running.tasks {

src/federation/similarity.rs

@@ -4,24 +4,30 @@
 //! module owns application policy: consent, peer fan-out, local index access,
 //! result conversion, deduplication, and ranking limits.
 
-use std::collections::{HashMap, HashSet};
+use std::collections::HashSet;
 use std::sync::Arc;
-use std::time::Duration;
+use std::time::{Duration, Instant};
 
 use anyhow::{Context as _, Result};
 use futures_util::stream::{self, StreamExt as _};
 use music_dht::similarity::{self as wire, SimilarityHit, SimilarityRequest, SimilarityResponse};
-use music_dht::{ByteStream, EndpointId, ItemId, ItemKind, MusicDhtService, StreamAcceptor};
+use music_dht::similarity_dht::SimilarityDht;
+use music_dht::{
+    ByteStream, EndpointId, ItemId, ItemKind, MusicDhtService, PeerTicket, StreamAcceptor,
+};
 
-use crate::federation::{FedSearchResults, FedTrack, TransportStats};
+use crate::federation::{
+    FedSimilaritySearchResults, FedTrack, ScoredFedTrack, SimilaritySearchStats, TransportStats,
+};
 use crate::similarity::{Manager, QueryVector};
 
 pub use music_dht::similarity::SIMILARITY_ALPN;
 
-const MAX_QUERY_PEERS: usize = 16;
-const QUERY_CONCURRENCY: usize = 6;
+const INITIAL_QUERY_PEERS: usize = 16;
+const MAX_QUERY_PEERS: usize = 48;
+const QUERY_CONCURRENCY: usize = 8;
 const QUERY_TIMEOUT: Duration = Duration::from_secs(5);
-const MAX_PER_ARTIST: usize = 3;
+const ROUTING_TIMEOUT: Duration = Duration::from_secs(5);
 const MAX_NEAR_DUPLICATE_SIGNATURE_DISTANCE: u32 = 8;
 
 pub async fn serve_peers(
@@ -57,7 +63,7 @@ async fn serve_one(
         let vector = request.vector;
         let limit = request.limit;
         let matches = tokio::task::spawn_blocking(move || {
-            similarity.search_vector(&profile, &vector, None, None, limit)
+            similarity.search_vector_for_peer(&profile, &vector, limit)
         })
         .await
         .context("local similarity task failed")
@@ -122,20 +128,51 @@ async fn serve_one(
 
 pub async fn search(
     service: Arc<MusicDhtService>,
+    routing: Arc<SimilarityDht>,
     query: QueryVector,
     limit: usize,
+    minimum_score: f32,
     transport: Arc<TransportStats>,
-) -> Result<FedSearchResults> {
+) -> Result<FedSimilaritySearchResults> {
+    let started = Instant::now();
     let own = service.endpoint_id();
-    let mut peers = Vec::new();
+    let routed = match tokio::time::timeout(
+        ROUTING_TIMEOUT,
+        routing.find_peers(&query.profile_id, &query.vector, MAX_QUERY_PEERS),
+    )
+    .await
+    {
+        Ok(Ok(peers)) => peers,
+        Err(_) => {
+            tracing::debug!("similarity DHT lookup timed out; using known peers");
+            Vec::new()
+        }
+        Ok(Err(error)) => {
+            tracing::debug!(%error, "similarity DHT lookup unavailable; using known peers");
+            Vec::new()
+        }
+    };
     let mut seen = HashSet::new();
+    let mut peers: Vec<QueryPeer> = routed
+        .into_iter()
+        .filter_map(|ticket| {
+            let owner = ticket.endpoint_id();
+            (owner != own && seen.insert(owner)).then_some(QueryPeer {
+                owner,
+                ticket: Some(ticket),
+            })
+        })
+        .collect();
     for peer in service
         .connected_peers()
         .into_iter()
         .chain(service.known_peers().into_iter().map(|peer| peer.peer_id))
     {
         if peer != own && seen.insert(peer) {
-            peers.push(peer);
+            peers.push(QueryPeer {
+                owner: peer,
+                ticket: None,
+            });
         }
         if peers.len() >= MAX_QUERY_PEERS {
             break;
@@ -148,36 +185,50 @@ pub async fn search(
         limit.clamp(1, wire::MAX_SIMILARITY_RESULTS),
     )?);
 
-    let responses = stream::iter(peers.into_iter().map(|peer| {
-        let service = Arc::clone(&service);
-        let request = Arc::clone(&request);
-        let transport = Arc::clone(&transport);
-        async move {
-            tokio::time::timeout(
-                QUERY_TIMEOUT,
-                query_peer(service, peer, &request, transport),
-            )
-            .await
-            .map_err(|_| anyhow::anyhow!("similarity peer timed out"))?
-        }
-    }))
-    .buffer_unordered(QUERY_CONCURRENCY)
-    .collect::<Vec<_>>()
-    .await;
-
     let mut hits = Vec::new();
+    let initial = peers.len().min(INITIAL_QUERY_PEERS);
+    let responses = query_peers(
+        Arc::clone(&service),
+        &peers[..initial],
+        Arc::clone(&request),
+        Arc::clone(&transport),
+    )
+    .await;
+    let mut successful = 0usize;
+    let mut peers_queried = initial;
     for response in responses {
         match response {
-            Ok(peer_hits) => hits.extend(peer_hits),
+            Ok(peer_hits) => {
+                successful += 1;
+                hits.extend(peer_hits);
+            }
             Err(err) => tracing::debug!(%err, "similarity peer query skipped"),
         }
     }
+    if initial < peers.len() && (hits.len() < limit || successful < initial.min(4)) {
+        peers_queried = peers.len();
+        for response in query_peers(
+            Arc::clone(&service),
+            &peers[initial..],
+            Arc::clone(&request),
+            Arc::clone(&transport),
+        )
+        .await
+        {
+            match response {
+                Ok(peer_hits) => hits.extend(peer_hits),
+                Err(err) => tracing::debug!(%err, "fallback similarity peer query skipped"),
+            }
+        }
+    }
     hits.sort_by(|left, right| right.1.total_cmp(&left.1));
     let mut dedup = HashSet::new();
     let mut embedding_signatures = vec![query_signature];
-    let mut artist_counts: HashMap<String, usize> = HashMap::new();
     let mut tracks = Vec::new();
-    for (track, _, embedding_signature) in hits {
+    for (track, score, embedding_signature) in hits {
+        if score < minimum_score {
+            break;
+        }
         if query
             .source_content_id
             .as_deref()
@@ -200,46 +251,85 @@ pub async fn search(
         }) {
             continue;
         }
-        let artist = track
-            .artist_names
-            .first()
-            .map(|name| music_dht::normalize_name(name))
-            .unwrap_or_default();
-        let count = artist_counts.entry(artist.clone()).or_default();
-        if !artist.is_empty() && *count >= MAX_PER_ARTIST {
-            continue;
-        }
-        *count += 1;
         if let Some(signature) = embedding_signature {
             embedding_signatures.push(signature);
         }
-        tracks.push(track);
+        tracks.push(ScoredFedTrack {
+            track,
+            score,
+            embedding_signature,
+        });
         if tracks.len() >= limit.min(wire::MAX_SIMILARITY_RESULTS) {
             break;
         }
     }
-    Ok(FedSearchResults {
-        artists: Vec::new(),
+    let artists = tracks
+        .iter()
+        .filter_map(|hit| hit.track.artist_names.first())
+        .map(|name| music_dht::normalize_name(name))
+        .filter(|name| !name.is_empty())
+        .collect::<HashSet<_>>()
+        .len();
+    let elapsed_ms = started.elapsed().as_millis().min(u128::from(u64::MAX)) as u64;
+    Ok(FedSimilaritySearchResults {
+        stats: SimilaritySearchStats {
+            tracks: tracks.len(),
+            artists,
+            peers_queried,
+            elapsed_ms,
+        },
         tracks,
     })
 }
 
+type PeerHits = Vec<(
+    FedTrack,
+    f32,
+    Option<[u8; wire::SIMILARITY_SIGNATURE_BYTES]>,
+)>;
+
+#[derive(Clone)]
+struct QueryPeer {
+    owner: EndpointId,
+    ticket: Option<PeerTicket>,
+}
+
+async fn query_peers(
+    service: Arc<MusicDhtService>,
+    peers: &[QueryPeer],
+    request: Arc<SimilarityRequest>,
+    transport: Arc<TransportStats>,
+) -> Vec<Result<PeerHits>> {
+    stream::iter(peers.iter().cloned().map(|peer| {
+        let service = Arc::clone(&service);
+        let request = Arc::clone(&request);
+        let transport = Arc::clone(&transport);
+        async move {
+            tokio::time::timeout(
+                QUERY_TIMEOUT,
+                query_peer(service, peer, &request, transport),
+            )
+            .await
+            .map_err(|_| anyhow::anyhow!("similarity peer timed out"))?
+        }
+    }))
+    .buffer_unordered(QUERY_CONCURRENCY)
+    .collect()
+    .await
+}
+
 async fn query_peer(
     service: Arc<MusicDhtService>,
-    owner: EndpointId,
+    peer: QueryPeer,
     request: &SimilarityRequest,
     transport: Arc<TransportStats>,
-) -> Result<
-    Vec<(
-        FedTrack,
-        f32,
-        Option<[u8; wire::SIMILARITY_SIGNATURE_BYTES]>,
-    )>,
-> {
-    let mut stream = service
-        .open_stream(owner, SIMILARITY_ALPN)
-        .await
-        .map_err(|err| anyhow::anyhow!("cannot reach similarity peer: {err}"))?;
+) -> Result<PeerHits> {
+    let owner = peer.owner;
+    let mut stream = match peer.ticket {
+        Some(ticket) => service.open_stream_to(&ticket, SIMILARITY_ALPN).await,
+        None => service.open_stream(owner, SIMILARITY_ALPN).await,
+    }
+    .map_err(|err| anyhow::anyhow!("cannot reach similarity peer: {err}"))?;
     super::record_stream_transport(&transport, "similarity", "outbound", "open", &stream);
     let response = wire::exchange(&mut stream, request).await?;
     super::record_stream_transport(&transport, "similarity", "outbound", "done", &stream);

src/library/mod.rs

@@ -207,6 +207,7 @@ CREATE TABLE IF NOT EXISTS track_embeddings (
     profile_id        TEXT NOT NULL REFERENCES similarity_profiles(profile_id) ON DELETE CASCADE,
     dimensions        INTEGER NOT NULL,
     vector            BLOB NOT NULL,
+    routing_signature BLOB,
     source_content_id TEXT,
     computed_at_ms    INTEGER NOT NULL,
     PRIMARY KEY (track_id, profile_id)
@@ -1551,15 +1552,17 @@ impl Library {
             "embedding contains a non-finite value"
         );
         let bytes = embedding_to_bytes(vector);
+        let routing_signature = music_dht::similarity_lsh::routing_signature(vector)?;
         let conn = self.lock();
         conn.execute(
             "INSERT INTO track_embeddings (
-                 track_id, profile_id, dimensions, vector,
+                 track_id, profile_id, dimensions, vector, routing_signature,
                  source_content_id, computed_at_ms
-             ) VALUES (?1, ?2, ?3, ?4, ?5, ?6)
+             ) VALUES (?1, ?2, ?3, ?4, ?5, ?6, ?7)
              ON CONFLICT(track_id, profile_id) DO UPDATE SET
                  dimensions = excluded.dimensions,
                  vector = excluded.vector,
+                 routing_signature = excluded.routing_signature,
                  source_content_id = excluded.source_content_id,
                  computed_at_ms = excluded.computed_at_ms",
             params![
@@ -1567,6 +1570,7 @@ impl Library {
                 profile_id,
                 vector.len() as i64,
                 bytes,
+                routing_signature.as_slice(),
                 track.content_id.as_deref(),
                 now_ms_i64(),
             ],
@@ -1633,6 +1637,65 @@ impl Library {
         Ok(embeddings)
     }
 
+    /// Loads the compact DHT-routing signatures for every current local
+    /// embedding. Rows created before similarity routing existed are
+    /// backfilled in place from their durable vectors.
+    pub fn similarity_routing_signatures(&self, profile_id: &str) -> Result<Vec<[u8; 32]>> {
+        let mut conn = self.lock();
+        let transaction = conn.transaction()?;
+        let missing = {
+            let mut statement = transaction.prepare(
+                "SELECT e.track_id, e.dimensions, e.vector
+             FROM track_embeddings e
+             JOIN tracks t ON t.id = e.track_id
+             WHERE e.profile_id = ?1
+               AND e.source_content_id IS t.content_id
+               AND (e.routing_signature IS NULL OR length(e.routing_signature) != 32)
+             ORDER BY e.track_id",
+            )?;
+            statement
+                .query_map([profile_id], |row| {
+                    Ok((
+                        row.get::<_, i64>(0)?,
+                        row.get::<_, i64>(1)?,
+                        row.get::<_, Vec<u8>>(2)?,
+                    ))
+                })?
+                .collect::<rusqlite::Result<Vec<_>>>()?
+        };
+        for (track_id, dimensions, vector_bytes) in missing {
+            let vector = embedding_from_bytes(dimensions, &vector_bytes)?;
+            let signature = music_dht::similarity_lsh::routing_signature(&vector)?;
+            transaction.execute(
+                "UPDATE track_embeddings
+                 SET routing_signature = ?3
+                 WHERE track_id = ?1 AND profile_id = ?2",
+                params![track_id, profile_id, signature.as_slice()],
+            )?;
+        }
+        transaction.commit()?;
+
+        let mut statement = conn.prepare(
+            "SELECT e.routing_signature
+             FROM track_embeddings e
+             JOIN tracks t ON t.id = e.track_id
+             WHERE e.profile_id = ?1
+               AND e.source_content_id IS t.content_id
+             ORDER BY e.track_id",
+        )?;
+        let stored = statement
+            .query_map([profile_id], |row| row.get::<_, Vec<u8>>(0))?
+            .collect::<rusqlite::Result<Vec<_>>>()?;
+        let signatures = stored
+            .into_iter()
+            .map(|signature| {
+                <[u8; 32]>::try_from(signature)
+                    .map_err(|_| anyhow::anyhow!("invalid similarity routing signature length"))
+            })
+            .collect::<Result<Vec<_>>>()?;
+        Ok(signatures)
+    }
+
     pub fn similarity_storage_stats(&self, profile_id: &str) -> Result<SimilarityStorageStats> {
         let conn = self.lock();
         let total_tracks = conn.query_row("SELECT COUNT(*) FROM tracks", [], |row| {
@@ -3444,6 +3507,16 @@ fn ensure_schema_migrations(conn: &Connection) -> Result<()> {
             [],
         )?;
     }
+    let embedding_columns = table_columns(conn, "track_embeddings")?;
+    if !embedding_columns
+        .iter()
+        .any(|column| column == "routing_signature")
+    {
+        conn.execute(
+            "ALTER TABLE track_embeddings ADD COLUMN routing_signature BLOB",
+            [],
+        )?;
+    }
     let mut rows = conn.prepare("SELECT id, title FROM playlists WHERE sync_id IS NULL")?;
     let missing = rows
         .query_map([], |row| {

src/library/tests.rs

@@ -701,24 +701,47 @@ fn similarity_embeddings_round_trip_and_keep_profiles_separate() {
         .into_iter()
         .find(|track| track.id == track_id)
         .unwrap();
-    lib.store_similarity_embedding(&track, "profile-a", &[0.1, 0.2, 0.3])
+    let first = [0.26726124, 0.5345225, 0.8017837];
+    let second = [0.8017837, 0.5345225, 0.26726124];
+    lib.store_similarity_embedding(&track, "profile-a", &first)
         .unwrap();
-    lib.store_similarity_embedding(&track, "profile-b", &[0.3, 0.2, 0.1])
+    lib.store_similarity_embedding(&track, "profile-b", &second)
         .unwrap();
 
     assert_eq!(
         lib.similarity_embedding(track_id, "profile-a").unwrap(),
-        Some(vec![0.1, 0.2, 0.3])
+        Some(first.to_vec())
     );
     assert_eq!(
         lib.similarity_embedding(track_id, "profile-b").unwrap(),
-        Some(vec![0.3, 0.2, 0.1])
+        Some(second.to_vec())
     );
     let stats = lib.similarity_storage_stats("profile-a").unwrap();
     assert_eq!(stats.total_tracks, 1);
     assert_eq!(stats.embedded_tracks, 1);
     assert_eq!(stats.stored_vectors, 2);
     assert_eq!(stats.stored_bytes, 24);
+    lib.lock()
+        .execute(
+            "UPDATE track_embeddings SET routing_signature = NULL WHERE profile_id = 'profile-a'",
+            [],
+        )
+        .unwrap();
+    assert_eq!(
+        lib.similarity_routing_signatures("profile-a")
+            .unwrap()
+            .len(),
+        1
+    );
+    let stored_signature_bytes: i64 = lib
+        .lock()
+        .query_row(
+            "SELECT length(routing_signature) FROM track_embeddings WHERE profile_id = 'profile-a'",
+            [],
+            |row| row.get(0),
+        )
+        .unwrap();
+    assert_eq!(stored_signature_bytes, 32);
 }
 
 #[test]

src/similarity.rs

@@ -7,7 +7,7 @@
 use std::collections::{HashMap, VecDeque};
 use std::fs::File;
 use std::path::{Path, PathBuf};
-use std::sync::atomic::{AtomicU64, AtomicUsize, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering};
 use std::sync::{Arc, Mutex, RwLock};
 use std::time::Instant;
 
@@ -36,7 +36,7 @@ const EMBEDDING_DIMENSIONS: usize = 1280;
 const MODEL_BATCH: usize = 8;
 const MAX_MODEL_BYTES: usize = 64 * 1024 * 1024;
 const RESULT_LIMIT: usize = 50;
-const MAX_PER_ARTIST: usize = 3;
+const PEER_CANDIDATE_MAX_PER_ARTIST: usize = 10;
 const NEAR_DUPLICATE_COSINE: f32 = 0.995;
 const FULL_TRACK_MAX_SECONDS: u32 = 5 * 60;
 const LONG_TRACK_WINDOW_SECONDS: u32 = 60;
@@ -101,7 +101,7 @@ impl Phase {
     }
 }
 
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
 pub struct SimilarityStatus {
     pub phase: Phase,
     pub active_profile: Option<String>,
@@ -144,6 +144,8 @@ pub struct Manager {
     settings: Mutex<SimilaritySettings>,
     workers: AtomicUsize,
     generation: AtomicU64,
+    pipeline_running: AtomicBool,
+    rescan_requested: AtomicBool,
     status: Mutex<SimilarityStatus>,
     index: RwLock<Index>,
     model: Mutex<Option<(String, RunnableModel)>>,
@@ -169,13 +171,20 @@ impl Manager {
                 Err(err) => tracing::warn!(%err, "similarity index restore failed"),
             }
         }
+        let target_profile = model_by_id(&settings.model)
+            .filter(|_| profile_by_id(&settings.profile).is_some())
+            .map(|model| profile_fingerprint(model, &settings.profile));
+        let restored_profile_is_current = index.profile_id == target_profile;
         let status = SimilarityStatus {
-            phase: if settings.enabled {
-                Phase::Loading
-            } else {
+            phase: if !settings.enabled {
                 Phase::Disabled
+            } else if restored_profile_is_current {
+                Phase::Ready
+            } else {
+                Phase::Loading
             },
             active_profile: index.profile_id.clone(),
+            target_profile,
             model: settings.model.clone(),
             ..SimilarityStatus::default()
         };
@@ -184,6 +193,8 @@ impl Manager {
             event_tx,
             workers: AtomicUsize::new(settings.workers.clamp(1, 16)),
             generation: AtomicU64::new(0),
+            pipeline_running: AtomicBool::new(false),
+            rescan_requested: AtomicBool::new(false),
             settings: Mutex::new(settings),
             status: Mutex::new(status),
             index: RwLock::new(index),
@@ -223,23 +234,51 @@ impl Manager {
             || previous.model != settings.model
             || previous.profile != settings.profile
         {
+            self.generation.fetch_add(1, Ordering::AcqRel);
             self.start();
         }
     }
 
+    /// Requests a scan without cancelling useful work already in progress.
+    /// Bursts of library-change notifications collapse into one follow-up
+    /// pass, so metadata refreshes cannot repeatedly restart the model.
     pub fn start(self: &Arc<Self>) {
-        let generation = self.generation.fetch_add(1, Ordering::AcqRel) + 1;
+        self.rescan_requested.store(true, Ordering::Release);
+        if self.pipeline_running.swap(true, Ordering::AcqRel) {
+            return;
+        }
         let this = Arc::clone(self);
         tokio::spawn(async move {
-            if let Err(err) = this.run_pipeline(generation).await
-                && this.generation.load(Ordering::Acquire) == generation
-            {
-                tracing::error!(%err, "similarity pipeline failed");
-                this.update_status(|status| {
-                    status.phase = Phase::Error;
-                    status.current_track = None;
-                    status.last_error = Some(format!("{err:#}"));
-                });
+            loop {
+                // This pass covers every notification received before it
+                // starts. A notification during the pass requests one more.
+                this.rescan_requested.store(false, Ordering::Release);
+                let generation = this.generation.load(Ordering::Acquire);
+                if let Err(err) = this.run_pipeline(generation).await
+                    && this.generation.load(Ordering::Acquire) == generation
+                {
+                    tracing::error!(%err, "similarity pipeline failed");
+                    this.update_status(|status| {
+                        status.phase = Phase::Error;
+                        status.current_track = None;
+                        status.last_error = Some(format!("{err:#}"));
+                    });
+                }
+
+                if this.rescan_requested.load(Ordering::Acquire) {
+                    continue;
+                }
+
+                this.pipeline_running.store(false, Ordering::Release);
+                // Close the small race between checking the request flag and
+                // releasing ownership of the worker. If another worker has
+                // already claimed it, that worker owns the pending pass.
+                if this.rescan_requested.swap(false, Ordering::AcqRel)
+                    && !this.pipeline_running.swap(true, Ordering::AcqRel)
+                {
+                    continue;
+                }
+                break;
             }
         });
     }
@@ -329,6 +368,52 @@ impl Manager {
         exclude_track_id: Option<i64>,
         exclude_content_id: Option<&str>,
         limit: usize,
+    ) -> Result<Vec<SimilarTrack>> {
+        let settings = lock(&self.settings);
+        let minimum_score = settings.minimum_score;
+        let max_tracks_per_artist = settings.max_tracks_per_artist;
+        drop(settings);
+        self.search_vector_with_policy(
+            profile_id,
+            vector,
+            exclude_track_id,
+            exclude_content_id,
+            limit,
+            minimum_score,
+            max_tracks_per_artist,
+        )
+    }
+
+    /// Returns a wider, policy-neutral candidate set to a remote requester.
+    /// The requester applies its own score threshold and artist diversity
+    /// limit; neither value is part of embedding compatibility.
+    pub(crate) fn search_vector_for_peer(
+        &self,
+        profile_id: &str,
+        vector: &[f32],
+        limit: usize,
+    ) -> Result<Vec<SimilarTrack>> {
+        self.search_vector_with_policy(
+            profile_id,
+            vector,
+            None,
+            None,
+            limit,
+            -1.0,
+            PEER_CANDIDATE_MAX_PER_ARTIST,
+        )
+    }
+
+    #[allow(clippy::too_many_arguments)]
+    fn search_vector_with_policy(
+        &self,
+        profile_id: &str,
+        vector: &[f32],
+        exclude_track_id: Option<i64>,
+        exclude_content_id: Option<&str>,
+        limit: usize,
+        minimum_score: f32,
+        max_tracks_per_artist: usize,
     ) -> Result<Vec<SimilarTrack>> {
         anyhow::ensure!(
             !vector.is_empty() && vector.len() <= 4096,
@@ -357,7 +442,7 @@ impl Manager {
                     entry.vector.as_slice(),
                 )
             })
-            .filter(|(_, score, _, _)| score.is_finite())
+            .filter(|(_, score, _, _)| score.is_finite() && *score >= minimum_score)
             .collect();
         scores.sort_by(|left, right| right.1.total_cmp(&left.1));
 
@@ -371,7 +456,7 @@ impl Manager {
                 continue;
             }
             let count = artist_counts.entry(artist.to_string()).or_default();
-            if !artist.is_empty() && *count >= MAX_PER_ARTIST {
+            if !artist.is_empty() && *count >= max_tracks_per_artist {
                 continue;
             }
             *count += 1;
@@ -431,7 +516,6 @@ impl Manager {
         )?;
         let stats = self.library.similarity_storage_stats(&profile_id)?;
         self.update_status(|status| {
-            status.phase = Phase::Downloading;
             status.target_profile = Some(profile_id.clone());
             status.model = spec.id.to_string();
             status.total_tracks = stats.total_tracks;
@@ -442,21 +526,18 @@ impl Manager {
             status.current_track = None;
             status.last_error = None;
         });
-        let model_path = self.ensure_model(spec, generation).await?;
-        self.ensure_generation(generation)?;
-        self.update_status(|status| status.phase = Phase::Loading);
-        let model = self.load_model(&profile_id, &model_path).await?;
-        self.ensure_generation(generation)?;
 
         let mut pending: VecDeque<_> = self.library.pending_similarity_tracks(&profile_id)?.into();
-        let pending_total = pending.len();
-        self.update_status(|status| {
-            status.phase = if pending_total == 0 {
-                Phase::Loading
-            } else {
-                Phase::Processing
-            };
-        });
+        if pending.is_empty() {
+            self.ensure_generation(generation)?;
+            return self.activate_profile(profile_id);
+        }
+
+        let model_path = self.ensure_model(spec, generation).await?;
+        self.ensure_generation(generation)?;
+        let model = self.load_model(&profile_id, &model_path).await?;
+        self.ensure_generation(generation)?;
+        self.update_status(|status| status.phase = Phase::Processing);
 
         let mut jobs = tokio::task::JoinSet::new();
         while !pending.is_empty() || !jobs.is_empty() {
@@ -506,6 +587,10 @@ impl Manager {
             }
         }
         self.ensure_generation(generation)?;
+        self.activate_profile(profile_id)
+    }
+
+    fn activate_profile(&self, profile_id: String) -> Result<()> {
         let entries = self.library.load_similarity_index(&profile_id)?;
         let total_tracks = self
             .library
@@ -519,7 +604,12 @@ impl Manager {
             profile_id: Some(profile_id.clone()),
             entries,
         };
-        lock(&self.settings).active_profile = Some(profile_id.clone());
+        let profile_changed = {
+            let mut settings = lock(&self.settings);
+            let changed = settings.active_profile.as_deref() != Some(&profile_id);
+            settings.active_profile = Some(profile_id.clone());
+            changed
+        };
         let stats = self.library.similarity_storage_stats(&profile_id)?;
         self.update_status(|status| {
             status.phase = Phase::Ready;
@@ -531,9 +621,11 @@ impl Manager {
             status.stored_bytes = stats.stored_bytes;
             status.current_track = None;
         });
-        let _ = self
-            .event_tx
-            .send(AppEvent::SimilarityProfileActivated(Some(profile_id)));
+        if profile_changed {
+            let _ = self
+                .event_tx
+                .send(AppEvent::SimilarityProfileActivated(Some(profile_id)));
+        }
         Ok(())
     }
 
@@ -561,6 +653,7 @@ impl Manager {
             tokio::fs::remove_file(&path).await?;
         }
 
+        self.update_status(|status| status.phase = Phase::Downloading);
         let response = reqwest::get(spec.url).await?.error_for_status()?;
         let tmp = path.with_extension(format!("part-{}-{generation}", std::process::id()));
         let mut file = tokio::fs::File::create(&tmp).await?;
@@ -603,6 +696,7 @@ impl Manager {
         {
             return Ok(Arc::clone(model));
         }
+        self.update_status(|status| status.phase = Phase::Loading);
         let path = path.to_path_buf();
         let model = tokio::task::spawn_blocking(move || load_onnx(&path))
             .await
@@ -614,10 +708,13 @@ impl Manager {
     fn update_status(&self, update: impl FnOnce(&mut SimilarityStatus)) {
         let snapshot = {
             let mut status = lock(&self.status);
+            let previous = status.clone();
             update(&mut status);
-            status.clone()
+            (*status != previous).then(|| status.clone())
         };
-        let _ = self.event_tx.send(AppEvent::SimilarityStatus(snapshot));
+        if let Some(snapshot) = snapshot {
+            let _ = self.event_tx.send(AppEvent::SimilarityStatus(snapshot));
+        }
     }
 }
 
@@ -977,6 +1074,14 @@ fn write<T>(lock: &RwLock<T>) -> std::sync::RwLockWriteGuard<'_, T> {
 mod tests {
     use super::*;
 
+    fn unique_test_dir(label: &str) -> PathBuf {
+        let unique = std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap()
+            .as_nanos();
+        std::env::temp_dir().join(format!("furumi-{label}-{}-{unique}", std::process::id()))
+    }
+
     #[test]
     fn profile_fingerprint_changes_with_contract() {
         let model = &MODELS[0];
@@ -1010,6 +1115,43 @@ mod tests {
         assert!(!is_near_duplicate(&distinct, &[&query]));
     }
 
+    #[tokio::test]
+    async fn repeated_rescans_keep_an_up_to_date_profile_ready() {
+        let directory = unique_test_dir("similarity-stable-status");
+        let library = Arc::new(Library::open(&directory.join("library.db")).unwrap());
+        let profile_id = profile_fingerprint(&MODELS[0], DEFAULT_PROFILE_ID);
+        let settings = SimilaritySettings {
+            enabled: true,
+            active_profile: Some(profile_id),
+            ..SimilaritySettings::default()
+        };
+        let (event_tx, mut event_rx) = tokio::sync::mpsc::unbounded_channel();
+        let manager = Manager::new(Arc::clone(&library), event_tx, settings);
+
+        assert_eq!(manager.status().phase, Phase::Ready);
+        for _ in 0..32 {
+            manager.start();
+        }
+        tokio::time::timeout(std::time::Duration::from_secs(2), async {
+            while manager.pipeline_running.load(Ordering::Acquire) {
+                tokio::task::yield_now().await;
+            }
+        })
+        .await
+        .unwrap();
+
+        assert_eq!(manager.status().phase, Phase::Ready);
+        while let Ok(event) = event_rx.try_recv() {
+            if let AppEvent::SimilarityStatus(status) = event {
+                assert_eq!(status.phase, Phase::Ready);
+            }
+        }
+
+        drop(manager);
+        drop(library);
+        std::fs::remove_dir_all(directory).unwrap();
+    }
+
     #[test]
     fn resampling_keeps_a_constant_signal() {
         let output = resample_sinc(&vec![0.25; 441], 44_100, 16_000);

src/ui/federation.rs

@@ -103,6 +103,14 @@ fn draw_settings_rows(frame: &mut Frame, area: Rect, state: &AppState) {
                 "Preprocessing profile",
                 format!("{} (enter for details)", similarity.profile),
             ),
+            SimilarityRow::MinimumScore => (
+                "Minimum similarity",
+                format!("{:.2}", similarity.minimum_score),
+            ),
+            SimilarityRow::MaxTracksPerArtist => (
+                "Tracks per artist",
+                similarity.max_tracks_per_artist.to_string(),
+            ),
             SimilarityRow::Workers => ("Background workers", similarity.workers.to_string()),
             SimilarityRow::Clear => ("Clear all stored embeddings", "↵".to_string()),
         };
@@ -400,6 +408,7 @@ fn protocol_label(id: &str) -> &str {
         "catalog" => "Catalog",
         "audio" => "Audio transfer",
         "similarity" => "Similarity search",
+        "similarity_dht" => "Similarity DHT",
         "device_sync" => "Device sync",
         "jam" => "Jam",
         other => other,
@@ -540,21 +549,20 @@ fn short_id(id: &str) -> String {
 }
 
 fn draw_status_column(frame: &mut Frame, area: Rect, state: &AppState) {
-    if area.height < 12 {
-        draw_status(frame, area, state);
-        return;
-    }
-    let [similarity_area, _, federation_area] = Layout::vertical([
-        Constraint::Length(8),
-        Constraint::Length(1),
-        Constraint::Min(0),
-    ])
-    .areas(area);
-    draw_similarity_status(frame, similarity_area, state);
-    draw_status(frame, federation_area, state);
+    draw_status(frame, area, state);
 }
 
 fn draw_similarity_status(frame: &mut Frame, area: Rect, state: &AppState) {
+    draw_summary_card(
+        frame,
+        area,
+        state,
+        " Similarity Processing ",
+        similarity_summary_lines(state),
+    );
+}
+
+fn similarity_summary_lines(state: &AppState) -> Vec<Line<'static>> {
     let status = &state.similarity.status;
     let progress = if status.total_tracks == 0 {
         "0 / 0".to_string()
@@ -571,34 +579,28 @@ fn draw_similarity_status(frame: &mut Frame, area: Rect, state: &AppState) {
         .as_deref()
         .map(short_id)
         .unwrap_or_else(|| "—".to_string());
-    draw_summary_card(
-        frame,
-        area,
-        state,
-        " Similarity Processing ",
-        vec![
-            status_line("State", status.phase.label().to_string()),
-            status_line("Progress", progress),
-            status_line("Active", active),
-            status_line("Processing", target),
-            status_line(
-                "Stored",
-                format!(
-                    "{} vectors / {}",
-                    status.stored_vectors,
-                    short_bytes_label(status.stored_bytes)
-                ),
+    vec![
+        summary_line("State", status.phase.label().to_string()),
+        summary_line("Progress", progress),
+        summary_line("Active", active),
+        summary_line("Processing", target),
+        summary_line(
+            "Stored",
+            format!(
+                "{} vectors / {}",
+                status.stored_vectors,
+                short_bytes_label(status.stored_bytes)
             ),
-            status_line(
-                "Current / errors",
-                status
-                    .current_track
-                    .clone()
-                    .or_else(|| status.last_error.clone())
-                    .unwrap_or_else(|| format!("{} errors", status.failed_tracks)),
-            ),
-        ],
-    );
+        ),
+        summary_line(
+            "Current",
+            status
+                .current_track
+                .clone()
+                .or_else(|| status.last_error.clone())
+                .unwrap_or_else(|| format!("{} errors", status.failed_tracks)),
+        ),
+    ]
 }
 
 fn draw_status(frame: &mut Frame, area: Rect, state: &AppState) {
@@ -615,69 +617,81 @@ fn draw_status(frame: &mut Frame, area: Rect, state: &AppState) {
         return;
     }
 
-    if area.width >= 60 && area.height >= 20 {
-        let protocols_height =
-            protocol_card_height(state, area.width.saturating_sub(2), area.height);
-        let [top_area, _, bottom_area, _, protocols_area, _] = Layout::vertical([
-            Constraint::Length(7),
-            Constraint::Length(1),
-            Constraint::Length(7),
-            Constraint::Length(1),
-            Constraint::Length(protocols_height),
-            Constraint::Min(0),
-        ])
-        .areas(area);
-        let [status_area, _, local_area] = Layout::horizontal([
-            Constraint::Percentage(50),
-            Constraint::Length(1),
-            Constraint::Percentage(50),
-        ])
-        .areas(top_area);
-        let [transport_area, _, devices_area] = Layout::horizontal([
-            Constraint::Percentage(50),
-            Constraint::Length(1),
-            Constraint::Percentage(50),
-        ])
-        .areas(bottom_area);
-        draw_summary_card(
-            frame,
-            status_area,
-            state,
-            " Status ",
-            node_summary_lines(state),
-        );
-        draw_summary_card(
-            frame,
-            local_area,
-            state,
-            " Local Data ",
-            local_data_summary_lines(state),
-        );
-        draw_summary_card(
-            frame,
-            transport_area,
-            state,
-            " Iroh Transport ",
-            transport_summary_lines(state),
-        );
-        draw_summary_card(
-            frame,
-            devices_area,
-            state,
-            " Connected Devices ",
-            device_summary_lines(state),
-        );
-        draw_summary_card(
-            frame,
-            protocols_area,
-            state,
-            " Protocol Versions ",
-            protocol_summary_lines(state, protocols_area.width.saturating_sub(2)),
-        );
-        return;
+    if area.width >= 60 {
+        let paired_width = area.width.saturating_sub(1) / 2;
+        let paired_height =
+            protocol_card_height(state, paired_width.saturating_sub(2), area.height).max(8);
+        if area.height >= 16 + paired_height {
+            let [top_area, _, middle_area, _, paired_area, _] = Layout::vertical([
+                Constraint::Length(7),
+                Constraint::Length(1),
+                Constraint::Length(7),
+                Constraint::Length(1),
+                Constraint::Length(paired_height),
+                Constraint::Min(0),
+            ])
+            .areas(area);
+            let [status_area, _, local_area] = Layout::horizontal([
+                Constraint::Percentage(50),
+                Constraint::Length(1),
+                Constraint::Percentage(50),
+            ])
+            .areas(top_area);
+            let [transport_area, _, devices_area] = Layout::horizontal([
+                Constraint::Percentage(50),
+                Constraint::Length(1),
+                Constraint::Percentage(50),
+            ])
+            .areas(middle_area);
+            let [similarity_area, _, protocols_area] = Layout::horizontal([
+                Constraint::Percentage(50),
+                Constraint::Length(1),
+                Constraint::Percentage(50),
+            ])
+            .areas(paired_area);
+            draw_summary_card(
+                frame,
+                status_area,
+                state,
+                " Status ",
+                node_summary_lines(state),
+            );
+            draw_summary_card(
+                frame,
+                local_area,
+                state,
+                " Local Data ",
+                local_data_summary_lines(state),
+            );
+            draw_summary_card(
+                frame,
+                transport_area,
+                state,
+                " Iroh Transport ",
+                transport_summary_lines(state),
+            );
+            draw_summary_card(
+                frame,
+                devices_area,
+                state,
+                " Connected Devices ",
+                device_summary_lines(state),
+            );
+            draw_similarity_status(frame, similarity_area, state);
+            draw_summary_card(
+                frame,
+                protocols_area,
+                state,
+                " Protocol Versions ",
+                protocol_summary_lines(state, protocols_area.width.saturating_sub(2)),
+            );
+            return;
+        }
     }
 
-    if area.height < 39 {
+    let protocols_height = protocol_card_height(state, area.width.saturating_sub(2), area.height);
+    let required_vertical_height = 41u16.saturating_add(protocols_height);
+    if area.height < required_vertical_height {
         frame.render_widget(
             Paragraph::new(compact_status_lines(state))
                 .wrap(ratatui::widgets::Wrap { trim: false }),
@@ -695,6 +709,8 @@ fn draw_status(frame: &mut Frame, area: Rect, state: &AppState) {
         _,
         local_area,
         _,
+        similarity_area,
+        _,
         protocols_area,
         _,
     ] = Layout::vertical([
@@ -706,11 +722,9 @@ fn draw_status(frame: &mut Frame, area: Rect, state: &AppState) {
         Constraint::Length(1),
         Constraint::Length(7),
         Constraint::Length(1),
-        Constraint::Length(protocol_card_height(
-            state,
-            area.width.saturating_sub(2),
-            area.height,
-        )),
+        Constraint::Length(8),
+        Constraint::Length(1),
+        Constraint::Length(protocols_height),
         Constraint::Min(0),
     ])
     .areas(area);
@@ -743,6 +757,7 @@ fn draw_status(frame: &mut Frame, area: Rect, state: &AppState) {
         " Local Data ",
         local_data_summary_lines(state),
     );
+    draw_similarity_status(frame, similarity_area, state);
     draw_summary_card(
         frame,
         protocols_area,
@@ -766,6 +781,12 @@ fn compact_status_lines(state: &AppState) -> Vec<Line<'static>> {
     lines.push(Line::styled("Connected Devices", theme::header_for(state)));
     lines.extend(device_summary_lines(state).into_iter().take(2));
     lines.push(Line::default());
+    lines.push(Line::styled(
+        "Similarity Processing",
+        theme::header_for(state),
+    ));
+    lines.extend(similarity_summary_lines(state).into_iter().take(3));
+    lines.push(Line::default());
     lines.push(Line::styled("Protocol Versions", theme::header_for(state)));
     lines.extend(protocol_summary_lines(state, 0).into_iter().take(3));
     lines

src/ui/global.rs

@@ -900,6 +900,9 @@ fn draw_search(frame: &mut Frame, area: Rect, state: &AppState, cursor: usize) {
         title.push_str("· searching… ");
     }
     let inner = bordered(frame, area, state, title);
+    if search.similarity_source.is_some() {
+        return draw_similarity_search(frame, inner, state, cursor);
+    }
 
     let empty_results = SearchResults::default();
     let results = match &search.results {
@@ -1102,6 +1105,156 @@ fn draw_search(frame: &mut Frame, area: Rect, state: &AppState, cursor: usize) {
     }
 }
 
+fn draw_similarity_search(frame: &mut Frame, area: Rect, state: &AppState, cursor: usize) {
+    let search = &state.search;
+    let status = if search.fed_loading {
+        super::loading_line(state, "searching federation…")
+    } else if let Some(stats) = &search.similarity_stats {
+        let elapsed = if stats.elapsed_ms < 1_000 {
+            format!("{} ms", stats.elapsed_ms)
+        } else {
+            format!("{:.2} s", stats.elapsed_ms as f64 / 1_000.0)
+        };
+        Line::from(vec![
+            Span::styled("Federation · ", theme::accent_for(state)),
+            Span::styled(
+                format!(
+                    "{} tracks · {} artists · {} peers queried · {elapsed}",
+                    stats.tracks, stats.artists, stats.peers_queried
+                ),
+                theme::dim(),
+            ),
+        ])
+    } else if search.similarity_error.is_some() {
+        Line::styled(
+            "Federation search failed · showing local results",
+            error_style(),
+        )
+    } else if search.loading {
+        super::loading_line(state, "preparing local similarity search…")
+    } else {
+        Line::styled("Federation disabled · showing local results", theme::dim())
+    };
+    let [status_area, content] =
+        Layout::vertical([Constraint::Length(1), Constraint::Min(0)]).areas(area);
+    frame.render_widget(Paragraph::new(status), status_area);
+
+    let mut rows: Vec<(Line, Option<String>, Option<usize>)> = Vec::new();
+    rows.push((Line::styled("Tracks", theme::header_for(state)), None, None));
+    if let Some(track) = &search.similarity_source_track {
+        let heart = if state.track_liked(track) {
+            Span::styled("♥ ", theme::accent_for(state))
+        } else {
+            Span::raw("  ")
+        };
+        rows.push((
+            Line::from(vec![
+                heart,
+                Span::raw(track.title.clone()),
+                Span::styled(
+                    format!("  {} · {}", track.artist_line(), track.release_title),
+                    theme::dim(),
+                ),
+            ]),
+            Some(super::track_meta_suffix(track, true)),
+            Some(0),
+        ));
+    }
+    for (offset, hit) in search.similarity_tracks.iter().enumerate() {
+        let index = offset + 1;
+        match hit {
+            crate::app::state::SimilaritySearchHit::Local { track, .. } => {
+                let heart = if state.track_liked(track) {
+                    Span::styled("♥ ", theme::accent_for(state))
+                } else {
+                    Span::raw("  ")
+                };
+                rows.push((
+                    Line::from(vec![
+                        heart,
+                        Span::raw(track.title.clone()),
+                        Span::styled(
+                            format!("  {} · {}", track.artist_line(), track.release_title),
+                            theme::dim(),
+                        ),
+                    ]),
+                    Some(super::track_meta_suffix(track, true)),
+                    Some(index),
+                ));
+            }
+            crate::app::state::SimilaritySearchHit::Federated { track, .. } => {
+                let heart = if state.fed_track_liked(track) {
+                    Span::styled("♥ ", theme::accent_for(state))
+                } else {
+                    Span::raw("  ")
+                };
+                let origin = if track.own {
+                    "your library".to_string()
+                } else {
+                    format!("peer {}…", track.owner_short())
+                };
+                let mut meta = track.duration_label();
+                if let Some(year) = track.year {
+                    if !meta.is_empty() {
+                        meta.push_str(" · ");
+                    }
+                    meta.push_str(&year.to_string());
+                }
+                rows.push((
+                    Line::from(vec![
+                        heart,
+                        fed_track_availability_prefix(state, track),
+                        Span::raw(track.title.clone()),
+                        Span::styled(
+                            format!("  {} · {origin}", track.artist_line()),
+                            theme::dim(),
+                        ),
+                    ]),
+                    Some(meta),
+                    Some(index),
+                ));
+            }
+        }
+    }
+
+    let scope = crate::app::state::TrackSelectionScope::SimilaritySearch;
+    let mut selected = std::collections::HashSet::new();
+    if state.track_selection.is_active_for(&scope)
+        && let Some(indices) = state
+            .track_selection
+            .indices(&scope, search.similarity_len())
+    {
+        selected.extend(indices);
+    }
+    let cursor_row = rows
+        .iter()
+        .position(|(_, _, row_cursor)| *row_cursor == Some(cursor))
+        .unwrap_or(0);
+    let visible = usize::from(content.height.max(1));
+    let first = cursor_row
+        .saturating_sub(visible / 2)
+        .min(rows.len().saturating_sub(visible));
+    for (offset, (line, right, row_cursor)) in
+        rows.into_iter().enumerate().skip(first).take(visible)
+    {
+        let rect = Rect {
+            x: content.x,
+            y: content.y + (offset - first) as u16,
+            width: content.width,
+            height: 1,
+        };
+        if let Some(row_index) = row_cursor
+            && selected.contains(&row_index)
+            && row_index != cursor
+        {
+            frame
+                .buffer_mut()
+                .set_style(rect, theme::selection_for(state));
+        }
+        draw_row(frame, rect, state, line, right, row_cursor == Some(cursor));
+    }
+}
+
 // ---------------------------------------------------------------------------
 // Federated artist card (assembled from peer catalogs)
 // ---------------------------------------------------------------------------