diff --git a/lib/features/addons/dash_assembler.dart b/lib/features/addons/dash_assembler.dart
index 9e72b91..774d1a8 100644
--- a/lib/features/addons/dash_assembler.dart
+++ b/lib/features/addons/dash_assembler.dart
@@ -22,8 +22,8 @@ class DashAssembler {
   /// Refuse absurd manifests instead of downloading the internet.
   static const int maxSegments = 512;
 
-  /// Segment fetch parallelism.
-  static const int parallelDownloads = 12;
+  /// Segment fetch parallelism (bounded to 6 to prevent memory spikes).
+  static const int parallelDownloads = 6;
 
   /// Assembled-file cache caps (hi-res tracks are ~50–100MB each).
   static const int maxCachedFiles = 16;
@@ -235,4 +235,4 @@ class DashAssembler {
       }
     } catch (_) {}
   }
-}
+}
\ No newline at end of file
diff --git a/lib/features/addons/local_media_server.dart b/lib/features/addons/local_media_server.dart
index e703407..1d588f1 100644
--- a/lib/features/addons/local_media_server.dart
+++ b/lib/features/addons/local_media_server.dart
@@ -32,13 +32,21 @@ class LocalMediaServer {
 
   final Dio _dio;
   HttpServer? _server;
+  String? _authToken;
   final Map<String, _Session> _sessions = {};
 
+  static String _generateAuthToken() {
+    final rand = Random.secure();
+    final bytes = List<int>.generate(16, (_) => rand.nextInt(256));
+    return bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
+  }
+
   Future<int> ensureStarted() async {
     final running = _server;
     if (running != null) return running.port;
     final bound =
         await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
+    _authToken ??= _generateAuthToken();
     bound.listen(_route, onError: (_) {});
     _server = bound;
     return bound.port;
@@ -75,7 +83,8 @@ class LocalMediaServer {
         () => _Session(_dio, safe, manifestXml),
       );
       session.kickoff();
-      return Uri.parse('http://127.0.0.1:$port/a/$safe.m4a');
+      final token = _authToken;
+      return Uri.parse('http://127.0.0.1:$port/a/$safe.m4a?token=$token');
     } catch (_) {
       return null;
     }
@@ -96,11 +105,22 @@ class LocalMediaServer {
 
   Future<void> _route(HttpRequest req) async {
     try {
+      // 1. Enforce GET method
       if (req.method != 'GET') {
         req.response.statusCode = HttpStatus.methodNotAllowed;
         await req.response.close();
         return;
       }
+
+      // 2. Validate ephemeral authentication token
+      final token = req.uri.queryParameters['token'];
+      if (_authToken == null || token != _authToken) {
+        req.response.statusCode = HttpStatus.forbidden;
+        await req.response.close();
+        return;
+      }
+
+      // 3. Validate path structure
       final segs = req.uri.pathSegments;
       if (segs.length != 2 ||
           segs[0] != 'a' ||
@@ -233,7 +253,12 @@ class _Session {
           onSegment: (i, bytes) => slots[i] = bytes,
           onBatch: (base, end) async {
             for (var i = base; i < end; i++) {
-              sink.add(slots[i]!);
+              final chunk = slots[i];
+              if (chunk != null) {
+                sink.add(chunk);
+                // Null out immediately after writing so GC can reclaim the memory
+                slots[i] = null;
+              }
             }
             await sink.flush();
           },
diff --git a/lib/features/audio_output/wasapi_engine.dart b/lib/features/audio_output/wasapi_engine.dart
index e8bf300..8d4eba5 100644
--- a/lib/features/audio_output/wasapi_engine.dart
+++ b/lib/features/audio_output/wasapi_engine.dart
@@ -1,3 +1,4 @@
+import 'dart:async';
 import 'dart:developer' as developer;
 import 'dart:io';
 
@@ -24,75 +25,124 @@ class WasapiEngine {
         return event.map((k, v) => MapEntry(k.toString(), v));
       }
       return <String, dynamic>{};
+    }).handleError((error) {
+      wasapiLog('deviceEvents stream error: $error');
     });
   }
 
   Future<List<DacDevice>> enumerateDevices() async {
     if (!isSupported) return const [];
     try {
-      final raw = await _channel.invokeMethod<List<dynamic>>('enumerateDevices');
+      final raw = await _channel
+          .invokeMethod<List<dynamic>>('enumerateDevices')
+          .timeout(const Duration(seconds: 4));
       if (raw == null) return const [];
-      return raw
-          .whereType<Map>()
-          .map(DacDevice.fromJson)
-          .toList();
+      return raw.whereType<Map>().map(DacDevice.fromJson).toList();
+    } on TimeoutException {
+      wasapiLog('enumerateDevices timed out');
+      return const [];
     } on PlatformException catch (e) {
       wasapiLog('enumerateDevices failed: ${e.message}');
       return const [];
+    } catch (e) {
+      wasapiLog('Unexpected error in enumerateDevices: $e');
+      return const [];
     }
   }
 
   Future<DacDevice?> probeDevice(String id) async {
-    if (!isSupported) return null;
+    if (!isSupported || id.trim().isEmpty) return null;
     try {
       final raw = await _channel.invokeMethod<Map<dynamic, dynamic>>(
         'probeDevice',
         {'id': id},
-      );
+      ).timeout(const Duration(seconds: 5));
+
       if (raw == null) return null;
       return DacDevice.fromJson(raw);
+    } on TimeoutException {
+      wasapiLog('probeDevice timed out for device $id');
+      return null;
     } on PlatformException catch (e) {
-      wasapiLog('probeDevice failed: ${e.message}');
+      wasapiLog('probeDevice failed for $id:${e.message}');
+      return null;
+    } catch (e) {
+      wasapiLog('Unexpected error in probeDevice for $id:$e');
       return null;
     }
   }
 
+  /// Verifies whether the specified DAC device supports a given PCM format
+  /// before requesting exclusive mode from libmpv.
+  Future<bool> isFormatSupported({
+    required String id,
+    required int sampleRate,
+    required int channels,
+    required int bitDepth,
+  }) async {
+    if (!isSupported || id.trim().isEmpty) return false;
+    try {
+      final supported = await _channel.invokeMethod<bool>('isFormatSupported', {
+        'id': id,
+        'sampleRate': sampleRate,
+        'channels': channels,
+        'bitDepth': bitDepth,
+      }).timeout(const Duration(seconds: 3));
+
+      return supported ?? false;
+    } catch (e) {
+      wasapiLog('Format check error ($sampleRate Hz, $bitDepth-bit):$e');
+      return false;
+    }
+  }
+
   Future<bool> setHardwareVolume(String id, double scalar) async {
-    if (!isSupported) return false;
+    if (!isSupported || id.trim().isEmpty) return false;
     try {
       await _channel.invokeMethod<void>('setHardwareVolume', {
         'id': id,
         'scalar': scalar.clamp(0.0, 1.0),
-      });
+      }).timeout(const Duration(seconds: 2));
       return true;
     } on PlatformException catch (e) {
       wasapiLog('setHardwareVolume failed: ${e.message}');
       return false;
+    } catch (_) {
+      return false;
     }
   }
 
   Future<double?> getHardwareVolume(String id) async {
-    if (!isSupported) return null;
+    if (!isSupported || id.trim().isEmpty) return null;
     try {
-      final v = await _channel.invokeMethod<num>('getHardwareVolume', {'id': id});
+      final v = await _channel.invokeMethod<num>('getHardwareVolume', {
+        'id': id,
+      }).timeout(const Duration(seconds: 2));
       return v?.toDouble();
     } on PlatformException catch (e) {
       wasapiLog('getHardwareVolume failed: ${e.message}');
       return null;
+    } catch (_) {
+      return null;
     }
   }
 
   Future<String> defaultDeviceId() async {
     if (!isSupported) return '';
     try {
-      return await _channel.invokeMethod<String>('defaultDeviceId') ?? '';
+      return await _channel
+              .invokeMethod<String>('defaultDeviceId')
+              .timeout(const Duration(seconds: 2)) ??
+          '';
     } on PlatformException catch (e) {
       wasapiLog('defaultDeviceId failed: ${e.message}');
       return '';
+    } catch (_) {
+      return '';
     }
   }
 }
 
 void wasapiLog(String message) {
   developer.log(message, name: 'WASAPI');
-}
+}
\ No newline at end of file
diff --git a/lib/features/innertube/signature_decipher.dart b/lib/features/innertube/signature_decipher.dart
index 0a0bb2a..ff8ca22 100644
--- a/lib/features/innertube/signature_decipher.dart
+++ b/lib/features/innertube/signature_decipher.dart
@@ -1,4 +1,5 @@
 import 'dart:convert';
+import 'dart:isolate';
 
 import 'package:dio/dio.dart';
 import 'package:meta/meta.dart';
@@ -154,7 +155,9 @@ class SignatureDecipher {
       ).timeout(const Duration(seconds: 20));
       final js = res.data ?? '';
       if (js.isEmpty) return null;
-      final script = _parse(jsUrl, js);
+
+      // Offload regex parsing to an isolate worker thread to prevent main UI thread stutters
+      final script = await Isolate.run(() => _parse(jsUrl, js));
       if (script == null) return null;
       if (_byJsUrl.length > 8) {
         _byJsUrl.clear();
@@ -260,7 +263,7 @@ class SignatureDecipher {
         '\\.get\\("n"\\)\\)&&\\($_sc=($_mc)(?:\\[(\\d+)\\])?\\($_sc\\)'),
   ];
 
-  PlayerScript? _parse(String jsUrl, String js) {
+  static PlayerScript? _parse(String jsUrl, String js) {
     // STS lives in the player script (NewPipe: signatureTimestamp[=:](\d+)).
     final sts = RegExp(r'signatureTimestamp[=:](\d+)')
         .firstMatch(js)
@@ -339,7 +342,7 @@ class SignatureDecipher {
 
   /// Extract `NAME=function(...)` source with balanced braces
   /// (lexer approach, mirroring NewPipe).
-  _FuncCode _extractFunction(String js, String name) {
+  static _FuncCode _extractFunction(String js, String name) {
     final idx = js.indexOf('$name=function');
     if (idx < 0) throw const FormatException('no func');
     final openIdx = js.indexOf('{', idx);
@@ -362,7 +365,7 @@ class SignatureDecipher {
 
   /// Strip NewPipe-style early-return guards, bind the array
   /// variable + extra literals, and compile op statements.
-  _Prepared _prepare(String js, String body, List<String> params,
+  static _Prepared _prepare(String js, String body, List<String> params,
       {String? extraLiteral}) {
     final env = <String, int>{};
     late final String arrayVar;
@@ -426,7 +429,7 @@ class SignatureDecipher {
     return _Prepared(ops, env, arrayVar);
   }
 
-  String? _findNFunc(String js) {
+  static String? _findNFunc(String js) {
     for (final pattern in _nNamePatterns) {
       final m = pattern.firstMatch(js);
       if (m == null) continue;
@@ -458,7 +461,7 @@ class SignatureDecipher {
 
   // -- helper objects + op classification --------------------------------------
 
-  DecipherOp _resolveOp(String js, String obj, String method,
+  static DecipherOp _resolveOp(String js, String obj, String method,
       String? argSrc, Map<String, int> outerEnv) {
     final helper = _helperBody(js, obj);
     final member = _memberBody(helper, method);
@@ -473,7 +476,7 @@ class SignatureDecipher {
     return _classify(member, env);
   }
 
-  String _helperBody(String js, String obj) {
+  static String _helperBody(String js, String obj) {
     // Helper objects are `var NAME={...};` (2+ char names).
     final m = RegExp('(?:var\\s+)?${RegExp.escape(obj)}\\s*=\\s*\\{')
         .firstMatch(js);
@@ -482,7 +485,7 @@ class SignatureDecipher {
     return _balanced(js, start);
   }
 
-  String _memberBody(String helper, String method) {
+  static String _memberBody(String helper, String method) {
     var m = RegExp(RegExp.escape(method) +
             r'\s*:\s*function\s*\(([^)]*)\)\s*\{')
         .firstMatch(helper);
@@ -500,7 +503,7 @@ class SignatureDecipher {
     throw FormatException('no member $method');
   }
 
-  List<String> _memberParams(String helper, String method) {
+  static List<String> _memberParams(String helper, String method) {
     final m = RegExp(RegExp.escape(method) +
             r'\s*(?::\s*function)?\s*\(([^)]*)\)\s*\{')
         .firstMatch(helper);
@@ -513,7 +516,7 @@ class SignatureDecipher {
         .toList();
   }
 
-  DecipherOp _classify(String body, Map<String, int> env) {
+  static DecipherOp _classify(String body, Map<String, int> env) {
     final b = body.replaceAll(RegExp(r'\s+'), '');
     if (b.contains('.reverse(')) return const DecipherOp(DecipherOpType.reverse);
     if (b.contains('.splice(')) {
@@ -559,7 +562,7 @@ class SignatureDecipher {
     throw const FormatException('unknown op');
   }
 
-  DecipherOp _spliceOp(List<String> args, Map<String, int> env) {
+  static DecipherOp _spliceOp(List<String> args, Map<String, int> env) {
     if (args.length >= 2) {
       final start = _evalInt(args[0], env, 0) ?? 0;
       final count = _evalInt(args[1], env, 0) ?? 0;
@@ -570,7 +573,7 @@ class SignatureDecipher {
     return DecipherOp(DecipherOpType.splice, [start]);
   }
 
-  List<String> _splitArgs(String src) {
+  static List<String> _splitArgs(String src) {
     final out = <String>[];
     var depth = 0;
     final buf = StringBuffer();
@@ -589,7 +592,7 @@ class SignatureDecipher {
     return out;
   }
 
-  int? _evalInt(String expr, Map<String, int> env, int len) {
+  static int? _evalInt(String expr, Map<String, int> env, int len) {
     final e = expr.trim();
     final lit = int.tryParse(e);
     if (lit != null) return lit;
@@ -605,7 +608,7 @@ class SignatureDecipher {
     return null;
   }
 
-  String _balanced(String src, int openIdx) {
+  static String _balanced(String src, int openIdx) {
     var depth = 0;
     var inStr = '';
     var escaped = false;
@@ -712,4 +715,4 @@ class _Prepared {
 
 extension _Let<T> on T {
   R let<R>(R Function(T) fn) => fn(this);
-}
+}
\ No newline at end of file
diff --git a/lib/features/player/playback_service.dart b/lib/features/player/playback_service.dart
index 64973f6..f8106ca 100644
--- a/lib/features/player/playback_service.dart
+++ b/lib/features/player/playback_service.dart
@@ -177,7 +177,7 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
       final path = _crumbPath;
       if (path == null) return;
       File(path).writeAsStringSync(
-        '${DateTime.now().toIso8601String()} $line\n',
+        '${DateTime.now().toIso8601String()}$line\n',
         mode: FileMode.append,
         flush: true,
       );
@@ -1364,10 +1364,10 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
     _resolvingIndex = index;
     _playbackAttempt = attempt;
     final totalSw = Stopwatch()..start();
+    final track = state.queue[index];
+    final wantedQueueKey = track.queueKey;
     int resolveMs = 0;
     try {
-      final track = state.queue[index];
-      final wantedQueueKey = track.queueKey;
       _activeQueueKey = wantedQueueKey;
       // Arm the first-audio clock: resolve-start → first playing=true.
       _audioClockStart = DateTime.now();
@@ -1428,6 +1428,9 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
         return;
       }
       if (stream == null) {
+        // Stale check before triggering retry or skip
+        if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
+
         // Retry YouTube-only only when the first pass could have taken
         // the lossless path — otherwise it repeats the identical
         // best-effort search (up to ~15s of spinner for nothing) on
@@ -1440,26 +1443,30 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
           return;
         }
         _unavailable.add(track.queueKey);
+        if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
         await _skipUnavailable(index);
         return;
       }
-      _resolving = false;
+
       final openSw = Stopwatch()..start();
       await _open(track, stream, generation, wantedQueueKey);
       openSw.stop();
       totalSw.stop();
-      if (generation == _resolveGeneration) {
-        _logTiming('play key=$wantedQueueKey path=remote '
-            'playcache_hit=${cached != null} '
-            'resolve_ms=$resolveMs '
-            'mpv_open_ms=${openSw.elapsedMilliseconds} '
-            'total_ms=${totalSw.elapsedMilliseconds}');
-      }
-      if (generation != _resolveGeneration) return;
+
+      // Guard: if user clicked next during _open, exit immediately
+      if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
+
+      _logTiming('play key=$wantedQueueKey path=remote '
+          'playcache_hit=${cached != null} '
+          'resolve_ms=$resolveMs '
+          'mpv_open_ms=${openSw.elapsedMilliseconds} '
+          'total_ms=${totalSw.elapsedMilliseconds}');
+
       _prefetchNeighbors();
       _maybeRefillRadio();
-    } catch (_) {
-      if (generation != _resolveGeneration) return;
+    } catch (e) {
+      // Strictly ignore errors from outdated skip requests
+      if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
       state = state.copyWith(
         isPlaying: false,
         isBuffering: false,
@@ -1467,6 +1474,7 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
         error: 'Could not load this track. Press Play to retry.',
       );
     } finally {
+      // Only release the resolving lock if THIS specific generation is still the latest
       if (generation == _resolveGeneration) {
         _resolving = false;
         _resolvingIndex = -1;
@@ -1898,6 +1906,9 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
       int stopMs = 0;
       int loadMs = 0;
       await _serializedMpv(() async {
+        // Stale check right before native operations
+        if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
+
         // Always tear down before loading: opening over a live stream
         // (or racing its teardown) corrupts the Windows libmpv heap —
         // first track plays, the next dies in ntdll.
@@ -1907,16 +1918,14 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
         } catch (_) {}
         stopSw.stop();
         stopMs = stopSw.elapsedMilliseconds;
-        if (generation != _resolveGeneration) return;
-        if (_activeQueueKey != wantedQueueKey) return;
+        if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
         if (wasDash) {
           // Proven crash window (mpv.log): the previous DASH demuxer
           // is still unwinding when loadfile arrives — the second
           // manifest dies mid-probe ~10ms after open. Bounded grace.
           _crumb('open key=$wantedQueueKey dash-grace');
           await Future.delayed(const Duration(milliseconds: 500));
-          if (generation != _resolveGeneration) return;
-          if (_activeQueueKey != wantedQueueKey) return;
+          if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
         }
         // Stamp open-issue BEFORE the call, not after it returns:
         // mpv events (pause=no) and the open() reply travel on separate
@@ -1926,6 +1935,10 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
             _activeQueueKey == wantedQueueKey) {
           _audioOpenDoneAt = DateTime.now();
         }
+
+        // Final sanity check before issuing native loadfile
+        if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
+
         final loadSw = Stopwatch()..start();
         await _player?.open(
           Media(playUrl, httpHeaders: stream.requestHeaders),
@@ -1937,8 +1950,7 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
       });
       _logTiming('mpv key=$wantedQueueKey kind=$kind '
           'stop_ms=$stopMs load_ms=$loadMs dash_grace=${wasDash ? 500 : 0}');
-      if (generation != _resolveGeneration) return;
-      if (_activeQueueKey != wantedQueueKey) return;
+      if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
       if (state.speed != 1.0) {
         await _player?.setRate(state.speed);
       }
@@ -1950,7 +1962,7 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
         debugPrint('LastWave-Player: open stack: $st');
         _dumpMpvLog('_open.exception');
       }
-      if (generation != _resolveGeneration) return;
+      if (generation != _resolveGeneration || _activeQueueKey != wantedQueueKey) return;
       await _onPlayerError();
     }
   }
@@ -2042,6 +2054,7 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
     _unavailable.add(track.queueKey);
     await _skipUnavailable(state.currentIndex);
   }
+
   Future<void> _skipUnavailable(int failedIndex) async {
     final nextIndex = _nextIndex(skipUnavailable: true);
     if (nextIndex == null) {
@@ -2170,6 +2183,7 @@ class PlaybackService extends StateNotifier<PlayerSnapshot> {
     }
     return null;
   }
+
   int? _prevIndex() {
     if (state.shuffleEnabled && _shuffleOrder.isNotEmpty) {
       final pos = _shuffleOrder.indexOf(state.currentIndex);
@@ -2649,4 +2663,4 @@ final playbackServiceProvider =
     unawaited(service.disposePlayer());
   });
   return service;
-});
+});
\ No newline at end of file