Fix SAM3 optional import; upload full code

app.py

@@ -31,6 +31,8 @@ def load_sam3(prompt: str, device: str):
     Cache SAM3 per (prompt, device) to avoid reloading weights.
     Created only inside inference after GPU slice is granted.
     """
+    if SAM3Segmenter is None:
+        raise gr.Error("SAM3 is unavailable in this Space (transformers build missing Sam3Processor/Sam3Model). Disable the SAM3 option.")
     return SAM3Segmenter(text_prompt=prompt, device=device)
 
 

segmenters/__init__.py

@@ -1,21 +1,29 @@
-from segmenters.base_segmenter import BaseSegmenter
-
-
-from segmenters.sam3 import SAM3Segmenter
-
-from segmenters.pca_segmenter import PCASegmenter
+from segmenters.base_segmenter import BaseSegmenter
+
+# SAM3 is optional; import lazily to avoid crashing when the model is unavailable
+try:
+    from segmenters.sam3 import SAM3Segmenter  # type: ignore
+except Exception as _sam3_err:  # pragma: no cover - best-effort optional import
+    SAM3Segmenter = None  # type: ignore
+    _SAM3_IMPORT_ERROR = _sam3_err
+
+from segmenters.pca_segmenter import PCASegmenter
 
 """
 Model registry for segmenters
 """
-_SEGMENTERS = {}
-if SAM3Segmenter is not None:
-    _SEGMENTERS["sam3"] = SAM3Segmenter
-if PCASegmenter is not None:
-    _SEGMENTERS["pca"] = PCASegmenter
-
-
-def get_segmenter(name: str, **kwargs):
-    if name not in _SEGMENTERS:
-        raise ValueError(f"Unknown segmenter '{name}'. Available: {list(_SEGMENTERS)}")
-    return _SEGMENTERS[name](**kwargs)
+_SEGMENTERS = {}
+if SAM3Segmenter is not None:
+    _SEGMENTERS["sam3"] = SAM3Segmenter
+if PCASegmenter is not None:
+    _SEGMENTERS["pca"] = PCASegmenter
+
+
+def get_segmenter(name: str, **kwargs):
+    if name not in _SEGMENTERS:
+        available = list(_SEGMENTERS)
+        msg = f"Unknown segmenter '{name}'. Available: {available}"
+        if name == "sam3" and 'SAM3Segmenter' in globals() and SAM3Segmenter is None:
+            msg += f". SAM3 import error: {_SAM3_IMPORT_ERROR}"
+        raise ValueError(msg)
+    return _SEGMENTERS[name](**kwargs)