fixes hopefully

Shared/Audio/AudioPlayer.swift

@@ -26,11 +26,12 @@ class AudioPlayer: NSObject, ObservableObject {
     @Published var volume: Float = 0.8
     @Published var repeatMode: RepeatMode = .off
     @Published var shuffleEnabled = false
-    // audioLevels is NOT @Published — avoids 60fps SwiftUI state thrashing.
-    // Instead, levelTick increments every time levels change. The visualizer
-    // observes levelTick: when it changes, body re-evaluates, Canvas re-executes,
-    // and pulls the latest levels via currentLevels(). Guaranteed dependency.
-    @Published private(set) var levelTick: Int = 0
+    // audioLevels is NOT @Published — avoids SwiftUI state thrashing.
+    // The Canvas reads currentLevels() directly on every TimelineView tick.
+    // levelTick is kept as an internal counter but intentionally NOT @Published —
+    // making it @Published caused 30fps objectWillChange on AudioPlayer, forcing
+    // every observing view (NowPlayingView, MainTabView, etc.) to re-evaluate 30x/sec.
+    private(set) var levelTick: Int = 0
     nonisolated(unsafe) private var _audioLevels: [Float] = Array(repeating: 0, count: 30)
 
     func currentLevels() -> [Float] { _audioLevels }
@@ -134,14 +135,11 @@ class AudioPlayer: NSObject, ObservableObject {
     private func suspendVisTimers() {
         stopOfflineVisTimer()
         stopLevelTimer()
-        // Cancel any in-progress offline vis analysis — it's a CPU-intensive FFT
-        // loop that will otherwise run to completion in background, burning ~60% CPU
         analysisTask?.cancel()
         analysisTask = nil
-        // Remove the periodic time observer — it fires at 10Hz updating @Published
-        // currentTime, driving SwiftUI re-evaluation of the entire view tree in background
+        AudioPreFetcher.shared.cancelAll()
         removeTimeObserver()
-        alog("Background: timers + time observer + analysis task suspended")
+        alog("Background: timers + time observer + analysis + prefetch suspended")
     }
 
     private func resumeVisTimers() {
@@ -1234,8 +1232,19 @@ class AudioPlayer: NSObject, ObservableObject {
         offlineVisFPS = VisualizerSettings.shared.effectiveFPS
         let points = VisualizerSettings.shared.nowPlaying.numberOfPoints
         let cutoff = VisualizerSettings.shared.frequencyCutoff
-        
-        analysisTask?.cancel()  // cancel any in-flight analysis from the previous song
+
+        analysisTask?.cancel()
+
+        // Don't start analysis if already in background — it will be triggered
+        // when the app returns to foreground instead (via resumeVisTimers path
+        // or next song load in foreground).
+        #if os(iOS)
+        guard UIApplication.shared.applicationState != .background else {
+            alog("Offline vis: skipping analysis in background for \(songId)")
+            return
+        }
+        #endif
+
         analysisTask = Task {
             let storage = VisualizerStorageManager.shared
             let hasCache = await storage.hasCache(for: songId)

iOS/Data/AudioPreFetcher.swift

@@ -16,7 +16,13 @@ class AudioPreFetcher {
     /// Pre-caches the next `maxPrefetch` tracks that aren't already downloaded.
     func prefetchUpcoming(queue: [Song], currentIndex: Int) {
         guard !queue.isEmpty else { return }
-        
+
+        #if os(iOS)
+        // Don't start prefetch tasks in background — URLSession.shared data tasks
+        // are not background-session tasks and consume CPU/network budget
+        guard UIApplication.shared.applicationState != .background else { return }
+        #endif
+
         let start = currentIndex + 1
         let end = min(start + maxPrefetch, queue.count)
         guard start < end else { return }
@@ -95,6 +101,12 @@ class AudioPreFetcher {
         }
     }
     
+    /// Cancel all in-flight prefetch tasks — called when app enters background
+    func cancelAll() {
+        prefetchTasks.values.forEach { $0.cancel() }
+        prefetchTasks.removeAll()
+    }
+
     func clearCache() {
         let dir = Self.prefetchCacheDir()
         try? FileManager.default.removeItem(at: dir)