feat: harden node placement and partial model loading

packages/node/meshnet_node/model_backend.py

@@ -899,12 +899,41 @@ def _load_partial_model_from_snapshot(
                     dtype=dtype,
                 )
 
-    for module in _active_modules_for_shard(model, shard_start, shard_end):
-        if hasattr(module, "to"):
-            module.to(device)
+    _finalize_active_shard_modules_on_device(model, shard_start, shard_end, device)
     return model
 
 
+def _finalize_active_shard_modules_on_device(
+    model: Any, shard_start: int, shard_end: int, device: Any
+) -> None:
+    """Place active shard modules on device without copying unmaterialized meta weights."""
+    for module in _active_modules_for_shard(model, shard_start, shard_end):
+        parameters = getattr(module, "parameters", None)
+        if not callable(parameters):
+            if hasattr(module, "to"):
+                module.to(device)
+            continue
+        params = list(parameters(recurse=True))
+        buffers_fn = getattr(module, "buffers", None)
+        buffers = list(buffers_fn(recurse=True)) if callable(buffers_fn) else []
+        tensors = params + buffers
+        if not tensors:
+            if hasattr(module, "to"):
+                module.to(device)
+            continue
+        if all(tensor.device.type == "meta" for tensor in tensors):
+            to_empty = getattr(module, "to_empty", None)
+            if callable(to_empty):
+                to_empty(device)
+            continue
+        if all(tensor.device.type != "meta" for tensor in tensors):
+            if hasattr(module, "to"):
+                module.to(device)
+            continue
+        # Partially materialized: set_module_tensor_to_device already placed loaded
+        # weights on the target device; leave remaining meta parameters untouched.
+
+
 def _model_load_plan(
     auto_config: Any,
     model_id: str,