diff --git a/electron/mediaTypes.test.ts b/electron/mediaTypes.test.ts
new file mode 100644
index 000000000..50dd99359
--- /dev/null
+++ b/electron/mediaTypes.test.ts
@@ -0,0 +1,15 @@
+import { describe, expect, it } from "vitest";
+import { getMediaContentType, isSupportedLocalMediaPath } from "./mediaTypes";
+
+describe("mediaTypes", () => {
+	it("allows macOS mic and system audio sidecars (.m4a)", () => {
+		expect(isSupportedLocalMediaPath("/tmp/recording-1.mic.m4a")).toBe(true);
+		expect(isSupportedLocalMediaPath("/tmp/recording-1.system.m4a")).toBe(true);
+		expect(getMediaContentType("/tmp/recording-1.mic.m4a")).toBe("audio/mp4");
+	});
+
+	it("still rejects unsupported extensions", () => {
+		expect(isSupportedLocalMediaPath("/tmp/notes.txt")).toBe(false);
+		expect(getMediaContentType("/tmp/notes.txt")).toBe("application/octet-stream");
+	});
+});
diff --git a/electron/mediaTypes.ts b/electron/mediaTypes.ts
index 5c4307b63..a27fb39a1 100644
--- a/electron/mediaTypes.ts
+++ b/electron/mediaTypes.ts
@@ -8,6 +8,7 @@ export const MEDIA_CONTENT_TYPES: Record<string, string> = {
 	".avi": "video/x-msvideo",
 	".wav": "audio/wav",
 	".mp3": "audio/mpeg",
+	".m4a": "audio/mp4",
 	".ogg": "audio/ogg",
 	".png": "image/png",
 	".jpg": "image/jpeg",