feat(audio): audio output device selection (closes #169)

Adds the ability to choose which audio output device Psysonic plays
through — useful for USB DACs, dedicated soundcards, and multi-device setups.

Rust (audio.rs):
- open_stream_for_device_and_rate(device_name, rate): opens a named
  device by cpal name, falls back to system default if not found
- AudioEngine.selected_device: persists the chosen device across
  stream reopens so hi-res rate switches stay on the right device
- audio_list_devices: Tauri command — returns all output device names
- audio_set_device: Tauri command — switches device immediately,
  drops old sinks, emits audio:device-changed
- start_device_watcher: now handles two cases:
    1. No pinned device + system default changed → reopen on new default
    2. Pinned device disappeared (DAC unplugged) → clear selected_device,
       fall back to system default, emit audio:device-reset

Frontend:
- authStore: audioOutputDevice (string | null), persisted
- playerStore: applies stored device on cold start
- App.tsx: listens to audio:device-reset, clears authStore device
  and restarts playback on the fallback device
- Settings → Audio tab: device dropdown at top (above Hi-Res and EQ),
  uses CustomSelect (portal-based, styled), all 8 locales
- CustomSelect: added disabled prop

Note: exclusive mode (WASAPI exclusive, CoreAudio exclusive) is out
of scope for now.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/App.tsx

@@ -437,6 +437,26 @@ function TauriEventBridge() {
     return () => { unlisten?.(); };
   }, []);
 
+  // Pinned output device was unplugged — Rust already fell back to system default.
+  // Clear the stored device so the Settings dropdown resets to "System Default".
+  useEffect(() => {
+    let unlisten: (() => void) | undefined;
+    listen('audio:device-reset', () => {
+      useAuthStore.getState().setAudioOutputDevice(null);
+      const { currentTrack, currentTime, isPlaying, playTrack, resetAudioPause } = usePlayerStore.getState();
+      if (!currentTrack) return;
+      if (isPlaying) {
+        const pos = currentTime;
+        const dur = currentTrack.duration || 1;
+        playTrack(currentTrack);
+        setTimeout(() => usePlayerStore.getState().seek(pos / dur), 600);
+      } else {
+        resetAudioPause();
+      }
+    }).then(u => { unlisten = u; });
+    return () => { unlisten?.(); };
+  }, []);
+
   // Sync tray-icon visibility with the user's stored setting.
   // Runs once on mount (initial sync) and again whenever the setting changes.
   const showTrayIcon = useAuthStore(s => s.showTrayIcon);

src/components/CustomSelect.tsx

@@ -15,9 +15,10 @@ interface Props {
   onChange: (value: string) => void;
   className?: string;
   style?: React.CSSProperties;
+  disabled?: boolean;
 }
 
-export default function CustomSelect({ value, options, onChange, className = '', style }: Props) {
+export default function CustomSelect({ value, options, onChange, className = '', style, disabled }: Props) {
   const [open, setOpen] = useState(false);
   const triggerRef = useRef<HTMLButtonElement>(null);
   const listRef = useRef<HTMLDivElement>(null);
@@ -80,7 +81,8 @@ export default function CustomSelect({ value, options, onChange, className = '',
         type="button"
         className={`custom-select-trigger ${className}`}
         style={style}
-        onClick={() => setOpen(v => !v)}
+        disabled={disabled}
+        onClick={() => { if (!disabled) setOpen(v => !v); }}
         aria-haspopup="listbox"
         aria-expanded={open}
       >

src/locales/de.ts

@@ -499,6 +499,9 @@ export const deTranslation = {
     hotCacheDebounceImmediate: 'Sofort',
     hotCacheDebounceSeconds: '{{n}} s',
     hotCacheClearBtn: 'Hot-Cache leeren',
+    audioOutputDevice: 'Audio-Ausgabegerät',
+    audioOutputDeviceDesc: 'Wähle das Audiogerät, über das Psysonic spielt. Änderungen werden sofort übernommen und starten den aktuellen Track neu.',
+    audioOutputDeviceDefault: 'Systemstandard',
     hiResTitle: 'Native Hi-Res-Wiedergabe',
     hiResEnabled: 'Native Hi-Res-Wiedergabe aktivieren',
     hiResDesc: "Standardmäßig wird auf 44,1 kHz begrenzt (maximale Stabilität). Nur aktivieren, wenn Hardware und Netzwerk zuverlässig hohe Abtastraten (88,2 kHz+) unterstützen.",

src/locales/en.ts

@@ -501,6 +501,9 @@ export const enTranslation = {
     hotCacheDebounceImmediate: 'Immediate',
     hotCacheDebounceSeconds: '{{n}} s',
     hotCacheClearBtn: 'Clear hot cache',
+    audioOutputDevice: 'Audio Output Device',
+    audioOutputDeviceDesc: 'Select which audio device Psysonic plays through. Changes take effect immediately and restart the current track.',
+    audioOutputDeviceDefault: 'System Default',
     hiResTitle: 'Native Hi-Res Playback',
     hiResEnabled: 'Enable native hi-res playback',
     hiResDesc: "Forces 44.1 kHz output by default for maximum stability. Enable only if your hardware and network reliably support high sample rates (88.2 kHz+).",

src/locales/es.ts

@@ -502,6 +502,9 @@ export const esTranslation = {
     hotCacheDebounceImmediate: 'Inmediato',
     hotCacheDebounceSeconds: '{{n}} s',
     hotCacheClearBtn: 'Limpiar caché activa',
+    audioOutputDevice: 'Dispositivo de salida de audio',
+    audioOutputDeviceDesc: 'Selecciona el dispositivo de audio que usa Psysonic. Los cambios surten efecto de inmediato y reinician la pista actual.',
+    audioOutputDeviceDefault: 'Predeterminado del sistema',
     hiResTitle: 'Reproducción Nativa Hi-Res',
     hiResEnabled: 'Habilitar reproducción nativa hi-res',
     hiResDesc: "Fuerza 44.1 kHz de salida por defecto para máxima estabilidad. Habilita solo si tu hardware y red soportan confiablemente altas tasas de muestreo (88.2 kHz+).",

src/locales/fr.ts

@@ -499,6 +499,9 @@ export const frTranslation = {
     hotCacheDebounceImmediate: 'Immédiat',
     hotCacheDebounceSeconds: '{{n}} s',
     hotCacheClearBtn: 'Vider le cache à chaud',
+    audioOutputDevice: 'Périphérique de sortie audio',
+    audioOutputDeviceDesc: 'Choisissez le périphérique audio utilisé par Psysonic. Les changements sont immédiats et relancent la piste en cours.',
+    audioOutputDeviceDefault: 'Défaut système',
     hiResTitle: 'Lecture haute résolution native',
     hiResEnabled: 'Activer la lecture haute résolution native',
     hiResDesc: "Force une sortie à 44,1 kHz par défaut pour une stabilité maximale. N'activer que si le matériel et le réseau prennent en charge les hautes fréquences d'échantillonnage (88,2 kHz+).",

src/locales/nb.ts

@@ -500,6 +500,9 @@ export const nbTranslation = {
     hotCacheDebounceImmediate: 'Umiddelbart',
     hotCacheDebounceSeconds: '{{n}} sek',
     hotCacheClearBtn: 'Tøm varm buffer',
+    audioOutputDevice: 'Lydutgangsenhet',
+    audioOutputDeviceDesc: 'Velg hvilken lydenhet Psysonic spiller gjennom. Endringer trer i kraft umiddelbart og starter gjeldende spor på nytt.',
+    audioOutputDeviceDefault: 'Systemstandard',
     hiResTitle: 'Innebygd hi-res-avspilling',
     hiResEnabled: 'Aktiver innebygd hi-res-avspilling',
     hiResDesc: "Begrenser utdata til 44,1 kHz som standard for maksimal stabilitet. Aktiver kun hvis maskinvare og nettverk støtter høye samplingsrater (88,2 kHz+) pålitelig.",

src/locales/nl.ts

@@ -498,6 +498,9 @@ export const nlTranslation = {
     hotCacheDebounceImmediate: 'Direct',
     hotCacheDebounceSeconds: '{{n}} s',
     hotCacheClearBtn: 'Warme cache wissen',
+    audioOutputDevice: 'Audio-uitvoerapparaat',
+    audioOutputDeviceDesc: 'Kies via welk audioapparaat Psysonic afspeelt. Wijzigingen worden direct toegepast en starten het huidige nummer opnieuw.',
+    audioOutputDeviceDefault: 'Systeemstandaard',
     hiResTitle: 'Natieve hi-res-weergave',
     hiResEnabled: 'Natieve hi-res-weergave inschakelen',
     hiResDesc: "Beperkt de uitvoer standaard tot 44,1 kHz voor maximale stabiliteit. Alleen inschakelen als hardware en netwerk hoge samplerates (88,2 kHz+) ondersteunen.",

src/locales/ru.ts

@@ -516,6 +516,9 @@ export const ruTranslation = {
     hotCacheDebounceImmediate: 'Сразу',
     hotCacheDebounceSeconds: '{{n}} с',
     hotCacheClearBtn: 'Очистить горячий кэш',
+    audioOutputDevice: 'Устройство вывода звука',
+    audioOutputDeviceDesc: 'Выберите аудиоустройство для воспроизведения. Изменения применяются немедленно и перезапускают текущий трек.',
+    audioOutputDeviceDefault: 'Системное по умолчанию',
     hiResTitle: 'Нативное воспроизведение Hi-Res',
     hiResEnabled: 'Включить нативное Hi-Res воспроизведение',
     hiResDesc: "По умолчанию вывод ограничен до 44,1 кГц для максимальной стабильности. Включайте только если оборудование и сеть надёжно поддерживают высокие частоты (88,2 кГц+).",

src/locales/zh.ts

@@ -494,6 +494,9 @@ export const zhTranslation = {
     hotCacheDebounceImmediate: '立即',
     hotCacheDebounceSeconds: '{{n}} 秒',
     hotCacheClearBtn: '清空热缓存',
+    audioOutputDevice: '音频输出设备',
+    audioOutputDeviceDesc: '选择 Psysonic 播放音频的设备。更改立即生效并重新开始当前曲目。',
+    audioOutputDeviceDefault: '系统默认',
     hiResTitle: '原生高清晰度播放',
     hiResEnabled: '启用原生高清晰度播放',
     hiResDesc: "默认强制 44.1 kHz 输出以获得最大稳定性。仅在硬件和网络可靠支持高采样率（88.2 kHz+）时启用。",

src/pages/Settings.tsx

@@ -5,7 +5,7 @@ import { useNavigate, useLocation } from 'react-router-dom';
 import {
   Wifi, WifiOff, Globe, Music2, Sliders, LogOut, CheckCircle2, FolderOpen,
   Palette, Server, Plus, Trash2, Eye, EyeOff, Info, ExternalLink, Shuffle, X, Play, Type, Keyboard, ChevronDown,
-  GripVertical, PanelLeft, RotateCcw, LayoutGrid, AppWindow, HardDrive, Upload, Download, Waves, Star, Clock, ZoomIn, Sparkles, AlertTriangle, Maximize2
+  GripVertical, PanelLeft, RotateCcw, LayoutGrid, AppWindow, HardDrive, Upload, Download, Waves, Star, Clock, ZoomIn, Sparkles, AlertTriangle, Maximize2, AudioLines
 } from 'lucide-react';
 import i18n from '../i18n';
 import { exportBackup, importBackup } from '../utils/backup';
@@ -260,6 +260,8 @@ export default function Settings() {
   const [imageCacheBytes, setImageCacheBytes] = useState<number | null>(null);
   const [offlineCacheBytes, setOfflineCacheBytes] = useState<number | null>(null);
   const [hotCacheBytes, setHotCacheBytes] = useState<number | null>(null);
+  const [audioDevices, setAudioDevices] = useState<string[]>([]);
+  const [deviceSwitching, setDeviceSwitching] = useState(false);
   const [showClearConfirm, setShowClearConfirm] = useState(false);
   const [clearing, setClearing] = useState(false);
   const [contributorsOpen, setContributorsOpen] = useState(false);
@@ -276,6 +278,12 @@ export default function Settings() {
     invoke<number>('get_hot_cache_size', { customDir: auth.hotCacheDownloadDir || null }).then(setHotCacheBytes).catch(() => setHotCacheBytes(0));
   }, [activeTab, auth.offlineDownloadDir, auth.hotCacheDownloadDir]);
 
+  // Load available audio output devices when Audio tab is open.
+  useEffect(() => {
+    if (activeTab !== 'audio') return;
+    invoke<string[]>('audio_list_devices').then(setAudioDevices).catch(() => {});
+  }, [activeTab]);
+
   /** Live disk usage for hot cache while Audio settings are open (interval + refresh when index changes). */
   useEffect(() => {
     if (activeTab !== 'audio') return;
@@ -490,6 +498,61 @@ export default function Settings() {
       {/* ── Audio ────────────────────────────────────────────────────────────── */}
       {activeTab === 'audio' && (
         <>
+          {/* Audio Output Device */}
+          <section className="settings-section">
+            <div className="settings-section-header">
+              <AudioLines size={18} />
+              <h2>{t('settings.audioOutputDevice')}</h2>
+            </div>
+            <div className="settings-card">
+              <div style={{ fontSize: 12, color: 'var(--text-muted)', marginBottom: '0.75rem' }}>
+                {t('settings.audioOutputDeviceDesc')}
+              </div>
+              <CustomSelect
+                value={auth.audioOutputDevice ?? ''}
+                disabled={deviceSwitching}
+                onChange={async (val) => {
+                  const device = val || null;
+                  setDeviceSwitching(true);
+                  try {
+                    await invoke('audio_set_device', { deviceName: device });
+                    auth.setAudioOutputDevice(device);
+                  } catch { /* device open failed — don't persist */ }
+                  setDeviceSwitching(false);
+                }}
+                options={[
+                  { value: '', label: t('settings.audioOutputDeviceDefault') },
+                  ...audioDevices.map(d => ({ value: d, label: d })),
+                ]}
+              />
+            </div>
+          </section>
+
+          {/* Native Hi-Res Playback */}
+          <section className="settings-section">
+            <div className="settings-section-header">
+              <Waves size={18} />
+              <h2>{t('settings.hiResTitle')}</h2>
+            </div>
+            <div className="settings-card">
+              <div className="settings-toggle-row">
+                <div>
+                  <div style={{ fontWeight: 500 }}>{t('settings.hiResEnabled')}</div>
+                  <div style={{ fontSize: 12, color: 'var(--text-muted)' }}>{t('settings.hiResDesc')}</div>
+                </div>
+                <label className="toggle-switch" aria-label={t('settings.hiResEnabled')}>
+                  <input
+                    type="checkbox"
+                    checked={auth.enableHiRes}
+                    onChange={e => auth.setEnableHiRes(e.target.checked)}
+                    id="hires-enabled-toggle"
+                  />
+                  <span className="toggle-track" />
+                </label>
+              </div>
+            </div>
+          </section>
+
           {/* Equalizer */}
           <section className="settings-section">
             <div className="settings-section-header">
@@ -810,31 +873,6 @@ export default function Settings() {
             </div>
           </section>
 
-          {/* Native Hi-Res Playback */}
-          <section className="settings-section">
-            <div className="settings-section-header">
-              <Waves size={18} />
-              <h2>{t('settings.hiResTitle')}</h2>
-            </div>
-            <div className="settings-card">
-              <div className="settings-toggle-row">
-                <div>
-                  <div style={{ fontWeight: 500 }}>{t('settings.hiResEnabled')}</div>
-                  <div style={{ fontSize: 12, color: 'var(--text-muted)' }}>{t('settings.hiResDesc')}</div>
-                </div>
-                <label className="toggle-switch" aria-label={t('settings.hiResEnabled')}>
-                  <input
-                    type="checkbox"
-                    checked={auth.enableHiRes}
-                    onChange={e => auth.setEnableHiRes(e.target.checked)}
-                    id="hires-enabled-toggle"
-                  />
-                  <span className="toggle-track" />
-                </label>
-              </div>
-            </div>
-          </section>
-
         </>
       )}
 

src/store/authStore.ts

@@ -77,6 +77,8 @@ interface AuthState {
 
   /** Alpha: native hi-res sample rate output (disabled = safe 44.1 kHz mode) */
   enableHiRes: boolean;
+  /** Selected audio output device name. null = system default. */
+  audioOutputDevice: string | null;
 
   /** Alpha: ephemeral queue prefetch cache on disk */
   hotCacheEnabled: boolean;
@@ -197,6 +199,7 @@ interface AuthState {
   setLastSeenChangelogVersion: (v: string) => void;
   setSeekbarStyle: (v: SeekbarStyle) => void;
   setEnableHiRes: (v: boolean) => void;
+  setAudioOutputDevice: (v: string | null) => void;
   setHotCacheEnabled: (v: boolean) => void;
   setHotCacheMaxMb: (v: number) => void;
   setHotCacheDebounceSec: (v: number) => void;
@@ -289,6 +292,7 @@ export const useAuthStore = create<AuthState>()(
       lastSeenChangelogVersion: '',
       seekbarStyle: 'waveform',
       enableHiRes: false,
+      audioOutputDevice: null,
       hotCacheEnabled: false,
       hotCacheMaxMb: 256,
       hotCacheDebounceSec: 30,
@@ -410,6 +414,7 @@ export const useAuthStore = create<AuthState>()(
 
       setSeekbarStyle: (v) => set({ seekbarStyle: v }),
       setEnableHiRes: (v) => set({ enableHiRes: v }),
+      setAudioOutputDevice: (v) => set({ audioOutputDevice: v }),
       setHotCacheEnabled: (v) => set({ hotCacheEnabled: v }),
       setHotCacheMaxMb: (v) => set({ hotCacheMaxMb: v }),
       setHotCacheDebounceSec: (v) => set({ hotCacheDebounceSec: v }),

src/store/playerStore.ts

@@ -575,9 +575,12 @@ export function initAudioListeners(): () => void {
   usePlayerStore.getState().syncLastfmLovedTracks();
 
   // Initial sync of audio settings to Rust engine on startup.
-  const { crossfadeEnabled, crossfadeSecs, gaplessEnabled } = useAuthStore.getState();
+  const { crossfadeEnabled, crossfadeSecs, gaplessEnabled, audioOutputDevice } = useAuthStore.getState();
   invoke('audio_set_crossfade', { enabled: crossfadeEnabled, secs: crossfadeSecs }).catch(() => {});
   invoke('audio_set_gapless', { enabled: gaplessEnabled }).catch(() => {});
+  if (audioOutputDevice) {
+    invoke('audio_set_device', { deviceName: audioOutputDevice }).catch(() => {});
+  }
 
   // Keep audio settings in sync whenever auth store changes.
   const unsubAuth = useAuthStore.subscribe((state) => {