fix: keep embedded audio in legacy mac mic sidecar exports

src/lib/exporter/audioEncoder.test.ts

@@ -161,6 +161,28 @@ describe("AudioProcessor offline render preparation", () => {
 		expect(renderAndMuxOfflineAudio).toHaveBeenCalled();
 	});
 
+	it("avoids the single-sidecar fast path for legacy mac mic sidecars that still need embedded audio", async () => {
+		const processor = new AudioProcessor() as unknown as OfflineRenderTestHarness;
+		const loadAudioFileDemuxer = vi.spyOn(processor, "loadAudioFileDemuxer");
+		const renderAndMuxOfflineAudio = vi
+			.spyOn(processor, "renderAndMuxOfflineAudio")
+			.mockResolvedValue();
+
+		await processor.process(
+			{} as never,
+			{} as never,
+			"file:///tmp/recording.mp4",
+			[],
+			[],
+			undefined,
+			[],
+			["/tmp/recording.mic.m4a"],
+		);
+
+		expect(loadAudioFileDemuxer).not.toHaveBeenCalled();
+		expect(renderAndMuxOfflineAudio).toHaveBeenCalled();
+	});
+
 	it("soft-limits mixed peaks before encoding or WAV conversion", () => {
 		const samples = new Float32Array([
 			-1.6,

src/lib/exporter/audioEncoder.ts

@@ -263,12 +263,18 @@ export class AudioProcessor {
 			videoUrl,
 			sortedSourceAudioFallbackPaths,
 		);
+		const requiresLegacyMacMicSidecarMix =
+			routingPolicy.includeEmbeddedInExport &&
+			!routingPolicy.hasEmbeddedSourceAudio &&
+			routingPolicy.playbackPaths.length === 1 &&
+			routingPolicy.playbackPaths[0]?.toLowerCase().endsWith(".mic.m4a") === true;
 		const hasTimedCompanionAudio = routingPolicy.playbackPaths.some(
 			(audioPath) => (sourceAudioFallbackStartDelayMsByPath?.[audioPath] ?? 0) > 0,
 		);
 		const needsSourceAudioMixing =
 			routingPolicy.playbackPaths.length > 1 ||
 			(routingPolicy.hasEmbeddedSourceAudio && routingPolicy.playbackPaths.length > 0) ||
+			requiresLegacyMacMicSidecarMix ||
 			hasTimedCompanionAudio;
 
 		// When speed edits, audio regions, or multiple audio sources need mixing, use offline AudioContext pipeline.