Monkey-patch torch to prevent hardcoded CUDA crashes on CPU instances

app.py

@@ -10,10 +10,28 @@ import io
 # (HuggingFace Spaces can use the hf_hub_download mechanism)
 from huggingface_hub import hf_hub_download
 
+# ── HF Token Authentication ────────────────────────────────────────
 print("Downloading SAM 3 model...")
 hf_token = os.environ.get("HF_TOKEN")
 ckpt_path = hf_hub_download(repo_id="facebook/sam3", filename="sam3.pt", token=hf_token)
 
+# ── Monkey Patch SAM 3 CUDA Hardcoding Bug ───────────────────────
+# Meta's SAM 3 repo hardcodes `device="cuda"` in position_encoding.py
+# This intercepts torch.zeros to force "cpu" if no GPU is available.
+original_zeros = torch.zeros
+def patched_zeros(*args, **kwargs):
+    if kwargs.get('device') == 'cuda' and not torch.cuda.is_available():
+        kwargs['device'] = 'cpu'
+    return original_zeros(*args, **kwargs)
+torch.zeros = patched_zeros
+
+original_arange = torch.arange
+def patched_arange(*args, **kwargs):
+    if kwargs.get('device') == 'cuda' and not torch.cuda.is_available():
+        kwargs['device'] = 'cpu'
+    return original_arange(*args, **kwargs)
+torch.arange = patched_arange
+
 # ── SAM 3 Imports ────────────────────────────────────────────────
 try:
     from sam3.model_builder import build_sam3_image_model