Fix launcher backend parsing and yt-dlp overrides

src/core/services/youtube/track-probe.test.ts

@@ -48,6 +48,37 @@ async function withFakeYtDlp<T>(
   });
 }
 
+async function withFakeYtDlpCommand<T>(
+  payload: unknown,
+  fn: () => Promise<T>,
+  options: { rawScript?: boolean } = {},
+): Promise<T> {
+  return await withTempDir(async (root) => {
+    const binDir = path.join(root, 'bin');
+    fs.mkdirSync(binDir, { recursive: true });
+    makeFakeYtDlpScript(binDir, payload, options.rawScript === true);
+    const originalPath = process.env.PATH;
+    const originalCommand = process.env.SUBMINER_YTDLP_BIN;
+    process.env.PATH = '';
+    process.env.SUBMINER_YTDLP_BIN =
+      process.platform === 'win32' ? path.join(binDir, 'yt-dlp.cmd') : path.join(binDir, 'yt-dlp');
+    try {
+      return await fn();
+    } finally {
+      if (originalPath === undefined) {
+        delete process.env.PATH;
+      } else {
+        process.env.PATH = originalPath;
+      }
+      if (originalCommand === undefined) {
+        delete process.env.SUBMINER_YTDLP_BIN;
+      } else {
+        process.env.SUBMINER_YTDLP_BIN = originalCommand;
+      }
+    }
+  });
+}
+
 test('probeYoutubeTracks prefers srv3 over vtt for automatic captions', async () => {
   await withFakeYtDlp(
     {
@@ -69,6 +100,28 @@ test('probeYoutubeTracks prefers srv3 over vtt for automatic captions', async ()
   );
 });
 
+test('probeYoutubeTracks honors SUBMINER_YTDLP_BIN when yt-dlp is not on PATH', async () => {
+  if (process.platform === 'win32') {
+    return;
+  }
+
+  await withFakeYtDlpCommand(
+    {
+      id: 'abc123',
+      title: 'Example',
+      subtitles: {
+        ja: [{ ext: 'vtt', url: 'https://example.com/ja.vtt', name: 'Japanese manual' }],
+      },
+    },
+    async () => {
+      const result = await probeYoutubeTracks('https://www.youtube.com/watch?v=abc123');
+      assert.equal(result.videoId, 'abc123');
+      assert.equal(result.tracks[0]?.downloadUrl, 'https://example.com/ja.vtt');
+      assert.equal(result.tracks[0]?.fileExtension, 'vtt');
+    },
+  );
+});
+
 test('probeYoutubeTracks keeps preferring srt for manual captions', async () => {
   await withFakeYtDlp(
     {