diff --git a/src/lib/exporter/audioProcessorShared.ts b/src/lib/exporter/audioProcessorShared.ts
index a48062a7..261615df 100644
--- a/src/lib/exporter/audioProcessorShared.ts
+++ b/src/lib/exporter/audioProcessorShared.ts
@@ -5,7 +5,8 @@ import type {
 	SourceAudioTrackSettings,
 	TrimRegion,
 } from "@/components/video-editor/types";
-import type { SourceTrackId } from "@/lib/exporter/audioRoutingEngine";
+
+export type SourceTrackId = "mic" | "system" | "mixed";
 
 export const AUDIO_BITRATE = 128_000;
 export const DECODE_BACKPRESSURE_LIMIT = 20;
diff --git a/src/lib/exporter/audioRoutingEngine.test.ts b/src/lib/exporter/audioRoutingEngine.test.ts
new file mode 100644
index 00000000..a915c787
--- /dev/null
+++ b/src/lib/exporter/audioRoutingEngine.test.ts
@@ -0,0 +1,33 @@
+import { describe, expect, it } from "vitest";
+import { buildResolvedAudioPlan, getSourceTrackIdFromPath } from "./audioRoutingEngine";
+
+describe("getSourceTrackIdFromPath", () => {
+	it.each([
+		["/recordings/recording-mic.wav", "mic"],
+		["/recordings/recording-system.wav", "system"],
+		["/recordings/system.mp4", "system"],
+		["/recordings/mic.wav", "mic"],
+	])("classifies companion path %s as %s", (path, trackId) => {
+		expect(getSourceTrackIdFromPath(path)).toBe(trackId);
+	});
+
+	it("routes mic and system companions onto their dedicated playback tracks", () => {
+		const plan = buildResolvedAudioPlan({
+			videoResource: "/recordings/recording.mp4",
+			sourceAudioFallbackPaths: [
+				"/recordings/recording.mp4",
+				"/recordings/recording-mic.wav",
+				"/recordings/system.mp4",
+			],
+		});
+
+		expect(plan.pathsByTrack).toEqual({
+			mic: "/recordings/recording-mic.wav",
+			system: "/recordings/system.mp4",
+		});
+		expect(plan.playbackPaths).toEqual([
+			"/recordings/system.mp4",
+			"/recordings/recording-mic.wav",
+		]);
+	});
+});
diff --git a/src/lib/exporter/audioRoutingEngine.ts b/src/lib/exporter/audioRoutingEngine.ts
index 8f9c7421..7bf618ea 100644
--- a/src/lib/exporter/audioRoutingEngine.ts
+++ b/src/lib/exporter/audioRoutingEngine.ts
@@ -1,8 +1,12 @@
-import type { AudioRegion } from "@/components/video-editor/types";
 import { SOURCE_AUDIO_NORMALIZE_GAIN } from "@/components/video-editor/audio/audioTypes";
+import type { AudioRegion } from "@/components/video-editor/types";
+import { getSourceTrackIdFromPath } from "./audioProcessorShared";
+import type { SourceTrackId } from "./audioProcessorShared";
 import { resolveSourceAudioFallbackPaths } from "./sourceAudioFallback";
 
-export type SourceTrackId = "mic" | "system" | "mixed";
+export { getSourceTrackIdFromPath };
+export type { SourceTrackId };
+
 export type ResolvedAudioTrackKind = "user" | "system" | "mic" | "mixed" | "embedded";
 
 export interface ResolvedAudioTrack {
@@ -29,13 +33,6 @@ export interface ResolvedAudioPlan {
 	masterGain: number;
 }
 
-export function getSourceTrackIdFromPath(audioPath: string): SourceTrackId {
-	const normalized = audioPath.toLowerCase();
-	if (normalized.includes(".mic.")) return "mic";
-	if (normalized.includes(".system.")) return "system";
-	return "mixed";
-}
-
 function clampGain(value: number, max: number) {
 	if (!Number.isFinite(value)) return 1;
 	return Math.max(0, Math.min(max, value));