Import Fails With `RuntimeError: No link is occupying sort id {multi_input_sort_id}`

[Vollkornaffe]

Happened with the "Radiator" node tree in this file: objects_passing_simulation_zone.zip

Backtrace with debug prints:

...
Tree (Radiator.003) -> COLLECTION (links): linking Math.003, Value to Store Named Attribute.001, Value
Tree (Radiator.003) -> COLLECTION (links): linking Random Value, Value_001 to Math.002, Value
Tree (Radiator.003) -> COLLECTION (links): linking Reroute.004, Output to Distribute Points on Faces, Seed
Tree (Radiator.003) -> COLLECTION (links): linking Math.002, Value to Math.003, Value
Tree (Radiator.003) -> COLLECTION (links): linking Math.001, Value to Math, Value
Traceback (most recent call last):
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/operators_import.py", line 219, in modal
    if _INTERMEDIATE_IMPORT_CACHE.step():
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 642, in step
    self.importer._import_node_tree(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 486, in _import_node_tree
    self._import_obj(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 437, in _import_obj
    self._import_obj_with_deserializer(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 342, in _import_obj_with_deserializer
    deserializer(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 403, in deserializer
    specific_handler(importer, getter, serialization, from_root)
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/specific_abstract.py", line 237, in wrapper
    inst.deserialize()
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/specific_handlers.py", line 209, in deserialize
    self.import_properties_from_id_list([NODE_TREE_LINKS])
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/specific_abstract.py", line 267, in import_properties_from_id_list
    self.importer.import_properties_from_id_list(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 140, in import_properties_from_id_list
    self._import_property(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 304, in _import_property
    return self._import_property_collection(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 253, in _import_property_collection
    self._import_obj(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 437, in _import_obj
    self._import_obj_with_deserializer(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 342, in _import_obj_with_deserializer
    deserializer(
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/import_nodes.py", line 403, in deserializer
    specific_handler(importer, getter, serialization, from_root)
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/specific_abstract.py", line 237, in wrapper
    inst.deserialize()
  File "/home/lars/.config/blender/5.0/extensions/vscode_development/tree_clipper_addon/_vendor/tree_clipper/specific_handlers.py", line 517, in deserialize
    raise RuntimeError("No link is occupying sort id {multi_input_sort_id}")
RuntimeError: No link is occupying sort id {multi_input_sort_id}

The issue appears when this link is imported:

Thanks to @kolibril13 for catching this.

[Vollkornaffe]

Also, the error message shows the format string; it's missing an f before the string literal.

[Vollkornaffe]

Hm, I got confused by the debug prints.

It's this link:

It appears to have multi_input_sort_id 1, even though it's the only one attached.

[Vollkornaffe]

Reduced to this, it still fails:

The link also appears to be offset from the middle.
If it's cut and reconnected, it sits centered, and the index is also correct:

[Vollkornaffe]

2026-01-21.15-15-04.mp4

[Vollkornaffe]

Related: https://projects.blender.org/blender/blender/issues/153169