perf(suggestions): add skip_vector_build option for faster initial load

- Add skip_vector_build config option to SuggestionConfig
- When true, skips ensure_vector calls (which can be very slow)
- Uses only cached/existing vectors for similarity search
- Frontend now uses skip_vector_build=true for initial load

- Add timestamped logging helper in frontend component

src-tauri/src/artist_vectors/suggestions.rs

@@ -34,6 +34,8 @@ pub struct SuggestionConfig {
     pub vector_max_age_days: i64,
     /// Minimum similarity score to include artist
     pub min_similarity: f32,
+    /// Skip building vectors - only use existing cached vectors (faster but may have fewer results)
+    pub skip_vector_build: bool,
 }
 
 impl Default for SuggestionConfig {
@@ -44,6 +46,7 @@ impl Default for SuggestionConfig {
             max_pool_size: 100,
             vector_max_age_days: 7,
             min_similarity: 0.1,
+            skip_vector_build: false,
         }
     }
 }
@@ -136,18 +139,22 @@ impl SuggestionsEngine {
             });
         }
 
-        // 1. Ensure vectors exist for playlist artists
-        log::info!("[SuggestionsEngine] Step 1: Ensuring vectors for {} artists", playlist_artist_mbids.len());
+        // 1. Ensure vectors exist for playlist artists (skip if configured)
         let step1_start = Instant::now();
-        for (i, mbid) in playlist_artist_mbids.iter().enumerate() {
-            let artist_start = Instant::now();
-            let _ = self
-                .builder
-                .ensure_vector(mbid, None, None, self.config.vector_max_age_days)
-                .await;
-            log::debug!("[SuggestionsEngine] ensure_vector {}/{} took {:?}", i + 1, playlist_artist_mbids.len(), artist_start.elapsed());
+        if self.config.skip_vector_build {
+            log::info!("[SuggestionsEngine] Step 1: SKIPPED (skip_vector_build=true), using only cached vectors");
+        } else {
+            log::info!("[SuggestionsEngine] Step 1: Ensuring vectors for {} artists", playlist_artist_mbids.len());
+            for (i, mbid) in playlist_artist_mbids.iter().enumerate() {
+                let artist_start = Instant::now();
+                let _ = self
+                    .builder
+                    .ensure_vector(mbid, None, None, self.config.vector_max_age_days)
+                    .await;
+                log::debug!("[SuggestionsEngine] ensure_vector {}/{} took {:?}", i + 1, playlist_artist_mbids.len(), artist_start.elapsed());
+            }
+            log::info!("[SuggestionsEngine] Step 1 completed in {:?}", step1_start.elapsed());
         }
-        log::info!("[SuggestionsEngine] Step 1 completed in {:?}", step1_start.elapsed());
 
         // 2. Compute combined playlist vector
         log::info!("[SuggestionsEngine] Step 2: Computing playlist vector");

src-tauri/src/commands/playlist_suggestions.rs

@@ -158,8 +158,8 @@ pub async fn get_playlist_suggestions_v2(
 
     // Create the engine with config
     let config = input.config.unwrap_or_default();
-    log::info!("[Suggestions] Config: max_artists={}, tracks_per={}, pool_size={}",
-        config.max_artists, config.tracks_per_artist, config.max_pool_size);
+    log::info!("[Suggestions] Config: max_artists={}, tracks_per={}, pool_size={}, skip_build={}",
+        config.max_artists, config.tracks_per_artist, config.max_pool_size, config.skip_vector_build);
 
     let engine = SuggestionsEngine::new(
         store_state.store.clone(),

src/lib/components/PlaylistSuggestions.svelte

@@ -57,6 +57,12 @@
   // Track the last playlist we loaded for
   let lastLoadedPlaylistId = $state<number | null>(null);
 
+  // Helper for timestamped logs
+  function log(...args: unknown[]) {
+    const ts = new Date().toISOString().slice(11, 23);
+    console.log(`[${ts}] [Suggestions]`, ...args);
+  }
+
   // Load suggestions when playlist/artists change
   $effect(() => {
     const artistCount = artists.length;
@@ -64,7 +70,7 @@
 
     // Only load if we have artists and haven't loaded for this playlist yet
     if (artistCount > 0 && currentPlaylistId !== lastLoadedPlaylistId && !loading) {
-      console.log('[Suggestions] Effect triggered, playlist:', currentPlaylistId, 'artists:', artistCount);
+      log('Effect triggered, playlist:', currentPlaylistId, 'artists:', artistCount);
       lastLoadedPlaylistId = currentPlaylistId;
       hasLoadedOnce = false;
       pool = [];
@@ -74,27 +80,27 @@
 
   async function loadSuggestions(expanded: boolean) {
     if (loading) {
-      console.log('[Suggestions] Already loading, skipping');
+      log('Already loading, skipping');
       return;
     }
 
     const poolSize = expanded ? EXPANDED_POOL : INITIAL_POOL;
-    console.log(`[Suggestions] Starting load (expanded=${expanded}, poolSize=${poolSize}, artists=${artists.length})`);
+    log(`Starting load (expanded=${expanded}, poolSize=${poolSize}, artists=${artists.length})`);
     const startTime = performance.now();
 
     loading = true;
     error = null;
 
     try {
-      console.log('[Suggestions] Calling backend...');
+      log('Calling backend...');
       result = await getPlaylistSuggestionsV2(
         artists,
         excludeTrackIds,
         showReasons,
-        { max_pool_size: poolSize }
+        { max_pool_size: poolSize, skip_vector_build: true }
       );
       const elapsed = ((performance.now() - startTime) / 1000).toFixed(2);
-      console.log(`[Suggestions] Backend returned in ${elapsed}s:`, {
+      log(`Backend returned in ${elapsed}s:`, {
         tracks: result.tracks.length,
         sourceArtists: result.source_artists.length,
         playlistArtists: result.playlist_artists_count,
@@ -105,7 +111,7 @@
       hasLoadedOnce = true;
     } catch (err) {
       const elapsed = ((performance.now() - startTime) / 1000).toFixed(2);
-      console.error(`[Suggestions] Failed after ${elapsed}s:`, err);
+      log(`Failed after ${elapsed}s:`, err);
       error = err instanceof Error ? err.message : 'Failed to load suggestions';
       pool = [];
     } finally {

src/lib/services/playlistSuggestionsService.ts

@@ -15,6 +15,8 @@ export interface SuggestionConfig {
   max_pool_size?: number;
   vector_max_age_days?: number;
   min_similarity?: number;
+  /** Skip building vectors - only use existing cached vectors (faster but may have fewer results) */
+  skip_vector_build?: boolean;
 }
 
 export interface SuggestedTrack {