fix(memory): release retired runtimes and idle download heap

android/app/src/main/kotlin/com/zarz/spotiflac/DownloadService.kt

@@ -1395,6 +1395,7 @@ class DownloadService : Service() {
                     failed = counts.failed,
                 )
                 currentStatus = "finalizing"
+                releaseIdleDownloadMemory()
                 writeNativeWorkerSnapshot(
                     isRunning = false,
                     isPaused = false,
@@ -1702,6 +1703,7 @@ class DownloadService : Service() {
                         failed = counts.failed,
                     )
                 currentStatus = "finalizing"
+                releaseIdleDownloadMemory()
                 writeNativeWorkerSnapshot(
                     isRunning = false,
                     isPaused = false,
@@ -1718,6 +1720,16 @@ class DownloadService : Service() {
         }
     }
 
+    private fun releaseIdleDownloadMemory() {
+        try {
+            // All workers and album tagging have finished. Return unused Go
+            // heap without forcing a collection between individual tracks.
+            Gobackend.releaseMemory()
+        } catch (e: Exception) {
+            android.util.Log.w("SpotiFLAC", "Failed to release idle download memory: ${e.message}")
+        }
+    }
+
     @Synchronized
     private fun ensureWakeLock() {
         val existingWakeLock = wakeLock

go_backend/extension_manager_runtime.go

@@ -201,6 +201,9 @@ func acquireIsolatedExtensionRuntime(ext *loadedExtension) (*goja.Runtime, *exte
 	ext.isolatedPoolMu.Lock()
 	if n := len(ext.isolatedPool); n > 0 {
 		handle := ext.isolatedPool[n-1]
+		// Reslicing alone retains this handle in the backing array. If the
+		// borrowed VM is retired after an error, its heap would stay alive.
+		ext.isolatedPool[n-1] = nil
 		ext.isolatedPool = ext.isolatedPool[:n-1]
 		ext.isolatedPoolMu.Unlock()
 		return handle.vm, handle.runtime, nil

go_backend/memory_release_test.go

@@ -1,10 +1,39 @@
 package gobackend
 
 import (
+	"runtime"
 	"testing"
 	"time"
+	"weak"
 )
 
+func TestDiscardedPooledRuntimeCanBeCollected(t *testing.T) {
+	ext := newTestLoadedExtension(t, ExtensionTypeDownloadProvider)
+	discarded := func() weak.Pointer[extensionRuntime] {
+		vm, rt, err := acquireIsolatedExtensionRuntime(ext)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := vm.Set("temporaryDownloadBytes", vm.NewArrayBuffer(make([]byte, 16<<20))); err != nil {
+			t.Fatal(err)
+		}
+		releaseIsolatedExtensionRuntime(ext, vm, rt, true, true, nil)
+		vm, rt, err = acquireIsolatedExtensionRuntime(ext)
+		if err != nil {
+			t.Fatal(err)
+		}
+		pointer := weak.Make(rt)
+		// An operation error retires the borrowed VM instead of pooling it.
+		releaseIsolatedExtensionRuntime(ext, vm, rt, false, true, nil)
+		return pointer
+	}()
+	runtime.GC()
+	if discarded.Value() != nil {
+		t.Fatal("retired runtime and its download buffer remain reachable from the idle pool")
+	}
+	runtime.KeepAlive(ext)
+}
+
 func TestReleaseMemoryUnderPressureClearsDisposableCaches(t *testing.T) {
 	clearCoverMemoryCache()
 	coverCachePut("https://example.com/cover.jpg", []byte("cover"))

lib/providers/download_queue_provider.dart

@@ -1893,6 +1893,10 @@ class DownloadQueueNotifier extends Notifier<DownloadQueueState> {
       _downloadCount = 0;
     }
 
+    if (!stoppedWhilePaused) {
+      await PlatformBridge.releaseNativeMemory();
+    }
+
     _log.i(
       'Queue stats - completed: $_completedInSession, failed: $_failedInSession, totalAtStart: $_totalQueuedAtStart',
     );