diff --git a/app/worker.py b/app/worker.py
index 9529193..76ad885 100644
--- a/app/worker.py
+++ b/app/worker.py
@@ -24,6 +24,17 @@ WHISPER_DEVICE = os.getenv("WHISPER_DEVICE", "auto").strip()
 WHISPER_DEVICE_INDEX = int(os.getenv("WHISPER_DEVICE_INDEX", "0"))
 WHISPER_CPU_THREADS = int(os.getenv("WHISPER_CPU_THREADS", "4"))
 
+# --- Host load guards / thread limits ---
+# Limit ffmpeg threads (helps keep CPU in check when multiple workers run)
+FFMPEG_THREADS = int(os.getenv("FFMPEG_THREADS", "1"))
+
+# Tame BLAS/threadpools that libraries may spin up implicitly
+import os as _os_threads
+_os_threads.environ.setdefault("OMP_NUM_THREADS", str(WHISPER_CPU_THREADS))
+_os_threads.environ.setdefault("OPENBLAS_NUM_THREADS", "1")
+_os_threads.environ.setdefault("MKL_NUM_THREADS", "1")
+_os_threads.environ.setdefault("NUMEXPR_NUM_THREADS", "1")
+
 # Whisper logging & resume controls
 WHISPER_LOG_SEGMENTS = os.getenv("WHISPER_LOG_SEGMENTS", "1") not in ("0", "false", "False")
 WHISPER_RESUME = os.getenv("WHISPER_RESUME", "1") not in ("0", "false", "False")
@@ -481,7 +492,7 @@ def ensure_sidecar_next_to_media(sidecar: Path, media_path: Path, lang: str = "e
             shutil.copy2(sidecar, dst)
         elif sidecar.suffix.lower() == ".vtt":
             tmp_srt = sidecar.with_suffix(".srt")
-            subprocess.run(["ffmpeg", "-nostdin", "-y", "-i", str(sidecar), str(tmp_srt)], check=True)
+            subprocess.run(["ffmpeg", "-nostdin", "-y", "-threads", str(FFMPEG_THREADS), "-i", str(sidecar), str(tmp_srt)], check=True)
             dst = media_path.with_suffix(f".{lang}.srt")
             shutil.move(str(tmp_srt), dst)
     except Exception as e:
@@ -787,6 +798,7 @@ def extract_audio(src: Path, outdir: Path) -> Path:
     # Force audio-only, mono, 16kHz WAV
     cmd = [
         "ffmpeg", "-nostdin", "-y",
+        "-threads", str(FFMPEG_THREADS),
         "-i", str(src),
         "-vn", "-ac", "1", "-ar", "16000",
         "-f", "wav", str(wav_path),