fix(download): preserve finalization metadata and library labels

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

@@ -18,8 +18,6 @@ import com.zarz.spotiflac.SafDownloadHandler.normalizeExt
 import com.zarz.spotiflac.NativeFinalizationPolicy.applyQualityVariantFilenameLabel
 import com.zarz.spotiflac.NativeFinalizationPolicy.displayAudioQuality
 import com.zarz.spotiflac.NativeFinalizationPolicy.formatIndexTag
-import com.zarz.spotiflac.NativeFinalizationPolicy.isLosslessAudioCodec
-import com.zarz.spotiflac.NativeFinalizationPolicy.isLossyAudioCodec
 import com.zarz.spotiflac.NativeFinalizationPolicy.normalizeAudioCodec
 import com.zarz.spotiflac.NativeFinalizationPolicy.resolvePreferredDecryptionExtension
 import gobackend.Gobackend
@@ -808,7 +806,11 @@ object NativeDownloadFinalizer {
         try {
             val codec = probePrimaryAudioCodec(localInput, shouldCancel)
             val isAlreadyNativeFlac = codec == "flac" && isNativeFlacFile(localInput)
-            if (!isLosslessAudioCodec(codec)) {
+            if (!NativeFinalizationPolicy.shouldAttemptLosslessContainerConversion(
+                    forceContainerConversion,
+                    codec,
+                )
+            ) {
                 Log.d(TAG, "Preserving native container; audio codec is ${codec.ifBlank { "unknown" }}")
                 // The preserved stream is not FLAC but still carries the
                 // requested .flac name. Rename to the real container so the

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

@@ -158,6 +158,22 @@ internal object NativeFinalizationPolicy {
         )
     }
 
+    /**
+     * Decides whether a stream should enter the lossless container conversion
+     * path. A missing or generic M4A/MP4 codec is inconclusive rather than
+     * proof of lossy audio; an extension capability may explicitly request
+     * that FFmpeg attempt the conversion. Known lossy codecs remain native.
+     */
+    fun shouldAttemptLosslessContainerConversion(
+        forceConversion: Boolean,
+        probedCodec: String?,
+    ): Boolean {
+        if (isLosslessAudioCodec(probedCodec)) return true
+        val normalized = normalizeAudioCodec(probedCodec)
+        val inconclusive = normalized == null || normalized == "m4a"
+        return forceConversion && inconclusive
+    }
+
     fun displayAudioQuality(
         filePath: String,
         fileName: String,

android/app/src/test/kotlin/com/zarz/spotiflac/NativeFinalizationPolicyTest.kt

@@ -101,6 +101,40 @@ class NativeFinalizationPolicyTest {
         assertFalse(NativeFinalizationPolicy.isLosslessAudioCodec("aac"))
     }
 
+    @Test
+    fun forcedContainerConversionAttemptsInconclusiveCodecButPreservesLossy() {
+        assertTrue(
+            NativeFinalizationPolicy.shouldAttemptLosslessContainerConversion(
+                forceConversion = true,
+                probedCodec = null,
+            ),
+        )
+        assertTrue(
+            NativeFinalizationPolicy.shouldAttemptLosslessContainerConversion(
+                forceConversion = true,
+                probedCodec = "m4a",
+            ),
+        )
+        assertTrue(
+            NativeFinalizationPolicy.shouldAttemptLosslessContainerConversion(
+                forceConversion = false,
+                probedCodec = "flac",
+            ),
+        )
+        assertFalse(
+            NativeFinalizationPolicy.shouldAttemptLosslessContainerConversion(
+                forceConversion = true,
+                probedCodec = "aac",
+            ),
+        )
+        assertFalse(
+            NativeFinalizationPolicy.shouldAttemptLosslessContainerConversion(
+                forceConversion = false,
+                probedCodec = null,
+            ),
+        )
+    }
+
     @Test
     fun isoBmffAudioUsesM4aExceptForAc4Passthrough() {
         assertEquals(