Focus on speedup and not hanging on large audio files.

src/worker/inference.worker.ts

@@ -232,6 +232,18 @@ async function transcribe(message: TranscribeMessage): Promise<void> {
     chunk_length_s: CHUNK_LENGTH_S,
     stride_length_s: STRIDE_LENGTH_S,
     return_timestamps: true,
+    // With return_timestamps and no explicit max_new_tokens, Transformers.js
+    // 4.2's Whisper generate() takes a seek-loop path that re-decodes each
+    // window's tail (1–3 generate passes per window). Under this pipeline's
+    // own 30 s/5 s chunking that is pure overhead: ~1.4× slower on long
+    // files, duplicated boundary text, on_finalize firing once per pass
+    // (breaking TranscribeProgressTracker's one-finalize-per-window
+    // assumption — the progress bar saturated early, then looked frozen),
+    // and a potential infinite loop when a window's last boundary timestamp
+    // is 0. Setting max_new_tokens selects the classic single-pass path;
+    // 440 ≈ Whisper's 448 decoder positions minus prompt headroom, far more
+    // than any real 30 s window produces.
+    max_new_tokens: 440,
   };
   if (message.stream ?? message.requestId === undefined) {
     // File-flow pass (id-less, or routed through BrowserEngine with an