fix: feature extractor CUDA detection, cache correctness, and short-video crash

- Detect CUDA version at venv creation time and install matching jax[cuda12/13]
  instead of hardcoded jax[cuda13] — was broken on CUDA 12.x (most systems)
- Include fps in cache hash: same video+caption at different fps previously
  returned stale cached features with wrong frame sampling
- Guard frame index lists with max(1,...)/max(8,...) to prevent torch.stack([])
  crash on very short input clips; sync minimum is 8 to match Synchformer's
  segment size requirement
- Remove mediapy from managed venv packages — not imported anywhere
- Warn when caption_cot is empty (produces degenerate text features)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nodes/feature_extractor.py

@@ -13,13 +13,29 @@ _PLUGIN_DIR = os.path.dirname(os.path.dirname(__file__))
 _MANAGED_VENV = os.path.join(_PLUGIN_DIR, "_extract_env")
 _MANAGED_PYTHON = os.path.join(_MANAGED_VENV, "bin", "python")
 
+def _jax_package():
+    """Return the correct jax extra for the current CUDA version."""
+    try:
+        import torch
+        if torch.cuda.is_available():
+            cuda_ver = torch.version.cuda or ""
+            major = int(cuda_ver.split(".")[0]) if cuda_ver else 0
+            if major >= 13:
+                return "jax[cuda13]"
+            elif major >= 12:
+                return "jax[cuda12]"
+    except Exception:
+        pass
+    return "jax"  # CPU fallback
+
+
 _EXTRACT_PACKAGES = [
     "torch", "torchaudio", "torchvision",
     # TF 2.15 only supports Python <=3.11; use >=2.16 for Python 3.12+
     "tensorflow-cpu>=2.16.0",
-    # jax[cuda13] includes jaxlib; pip-managed CUDA libs (no local toolkit needed)
-    "jax[cuda13]", "flax",
-    "transformers", "decord", "einops", "numpy", "mediapy",
+    # jax CUDA extra is resolved at install time based on detected CUDA version
+    _jax_package(), "flax",
+    "transformers", "decord", "einops", "numpy",
     "git+https://github.com/google-deepmind/videoprism.git",
 ]
 
@@ -70,11 +86,12 @@ def _ensure_extract_env():
     return _MANAGED_PYTHON
 
 
-def _hash_inputs(video_tensor, cot_text):
+def _hash_inputs(video_tensor, cot_text, fps):
     """Create a hash of the inputs for caching."""
     h = hashlib.sha256()
     h.update(video_tensor.cpu().numpy().tobytes()[:1024 * 1024])  # First 1MB for speed
     h.update(cot_text.encode())
+    h.update(str(fps).encode())  # fps affects frame sampling — must be part of the key
     return h.hexdigest()[:16]
 
 
@@ -115,6 +132,10 @@ class PrismAudioFeatureExtractor:
         if video_info is not None:
             fps = video_info["loaded_fps"]
 
+        if not caption_cot.strip():
+            print("[PrismAudio] Warning: caption_cot is empty — text features will be degenerate. "
+                  "Provide a descriptive chain-of-thought caption for best results.", flush=True)
+
         # Resolve python binary
         if python_env == "comfyui_env":
             print("[PrismAudio] WARNING: using ComfyUI Python env — JAX/TF/videoprism must already be installed. "
@@ -129,7 +150,7 @@ class PrismAudioFeatureExtractor:
         os.makedirs(cache_dir, exist_ok=True)
 
         # Check cache
-        cache_hash = _hash_inputs(video, caption_cot)
+        cache_hash = _hash_inputs(video, caption_cot, fps)
         cached_path = os.path.join(cache_dir, f"{cache_hash}.npz")
         if os.path.exists(cached_path):
             print(f"[PrismAudio] Using cached features: {cached_path}")