src/audio/audio_manager.cpp

@@ -512,9 +512,19 @@ namespace radiantwave::audio
         return false;
     }
 
-    // Must be called with mutex_ held. Destroys the current mixer and creates a
-    // fresh one on the given device, recreating the two track slots and
-    // resuming the active track if one was playing.
+    // Must be called with mutex_ held. Creates a fresh mixer on the given
+    // device, recreating the two track slots and resuming the active track if
+    // one was playing.
+    //
+    // The new mixer is created BEFORE the current one is destroyed. Reversing
+    // the order (destroy-then-reopen) quits the whole SDL audio subsystem the
+    // moment the last device closes: MIX_DestroyMixer() follows up with
+    // SDL_QuitSubSystem(SDL_INIT_AUDIO), which tears down SDL's device registry
+    // and renumbers every enumerated device id on the way back up. The id this
+    // switch was asked to open is then stale and the reopen fails with
+    // "Invalid audio device instance ID". Keeping the current device open while
+    // the replacement opens also means a failed switch leaves the current
+    // output playing instead of going permanently mute.
     bool AudioManager::recreateMixerOnDevice(SDL_AudioDeviceID targetId)
     {
         // Capture the playback state we want to preserve across the switch.
@@ -523,7 +533,37 @@ namespace radiantwave::audio
                                 ? slots_[activeSlot_].fadeInDuration
                                 : 0.0f;
 
-        // Tear down the existing mixer (its tracks die with it).
+        // Open the replacement mixer on the target device first, while the
+        // current device (and SDL's device registry) is still alive.
+        MIX_Mixer *newMixer = MIX_CreateMixerDevice(targetId, nullptr);
+        if (!newMixer)
+        {
+            std::string err = SDL_GetError();
+            logger::Logger::instance().error(
+                "Audio",
+                "Could not open audio output device "
+                + mapToFriendlyDeviceName(resolvePlaybackDeviceName(targetId))
+                + "; keeping the current device (MIX_CreateMixerDevice error: "
+                + err + ")");
+            return false;
+        }
+
+        MIX_Track *newTracks[2];
+        for (int i = 0; i < 2; ++i)
+        {
+            newTracks[i] = MIX_CreateTrack(newMixer);
+        }
+        if (!newTracks[0] || !newTracks[1])
+        {
+            MIX_DestroyMixer(newMixer);
+            logger::Logger::instance().error(
+                "Audio", "Could not create mixer tracks; keeping the current device (SDL error: "
+                             + std::string(SDL_GetError()) + ")");
+            return false;
+        }
+
+        // Tear down the existing mixer (its tracks die with it) and adopt the
+        // new one.
         for (int i = 0; i < 2; ++i)
         {
             slots_[i].track = nullptr;
@@ -539,22 +579,9 @@ namespace radiantwave::audio
             mixer_ = nullptr;
         }
 
-        mixer_ = MIX_CreateMixerDevice(targetId, nullptr);
-        if (!mixer_)
-        {
-            initialized_ = false;
-            return false;
-        }
-
-        slots_[0].track = MIX_CreateTrack(mixer_);
-        slots_[1].track = MIX_CreateTrack(mixer_);
-        if (!slots_[0].track || !slots_[1].track)
-        {
-            MIX_DestroyMixer(mixer_);
-            mixer_ = nullptr;
-            initialized_ = false;
-            return false;
-        }
+        mixer_ = newMixer;
+        slots_[0].track = newTracks[0];
+        slots_[1].track = newTracks[1];
 
         float gain = enabled_ ? (volume_ / 100.0f) : 0.0f;
         MIX_SetMixerGain(mixer_, gain);

src/audio/audio_manager.h

@@ -111,8 +111,11 @@ private:
     // Recreates the mixer on the given playback device id (0 = system default).
     // Called with mutex_ held. Preserves playback state: whichever track was
     // playing on the active slot is reloaded and resumed at full gain, an
-    // in-progress fade is restarted. Returns false on failure (previous mixer is
-    // left destroyed but the app remains safe to keep running muted).
+    // in-progress fade is restarted. The replacement mixer is opened before the
+    // current one is destroyed so SDL's device ids stay valid (destroy-first
+    // quits the whole audio subsystem and orphans the id being opened).
+    // Returns false on failure without touching the current mixer, so the
+    // existing output keeps playing.
     bool recreateMixerOnDevice(SDL_AudioDeviceID targetId);
 
     config::ConfigManager* configManager_ = nullptr;

src/audio_settings_page.cpp

@@ -288,7 +288,7 @@ void AudioSettingsPage::applyDeviceSelection() {
     if (ok) {
         statusMessage_ = "Switched to " + devices_[currentDeviceIndex_].friendly_name;
     } else {
-        statusMessage_ = "Device unavailable - using system default";
+        statusMessage_ = "Device unavailable - kept the current output";
     }
     refreshDeviceAndTrackLists();
 }