list support

core/nodeslicer/nodes/base.py

@@ -134,6 +134,45 @@ class SliceNodeJoiner(SliceNode):
         self.add_output(self.output_socket_type or self.socket_type, name=self.socket_label)
         self.add_multi_socket_group(self.socket_type, name=self.socket_label)
 
+    def update(self) -> None:
+        super().update()
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
+        for inp in self.inputs:
+            if getattr(inp, "name", "") == self.socket_label or getattr(inp, "identifier", "").startswith(f"{self.socket_label}_ms_in_"):
+                is_list = is_socket_linked_to_list(inp)
+                set_socket_shape(inp, "LIST" if is_list else "CIRCLE")
+
+class SliceNodeListJoiner(SliceNode):
+    socket_type: str = ""
+    output_socket_type: str = ""
+    socket_label: str = ""
+    output_socket_name: str = ""
+    is_list_output: bool = True
+
+    def init(self, context):
+        self.add_output(self.output_socket_type or self.socket_type, name=self.output_socket_name or self.socket_label, display_shape='LIST')
+        self.add_multi_socket_group(self.socket_type, name=self.socket_label)
+
+    def update(self) -> None:
+        super().update()
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
+        for inp in self.inputs:
+            if getattr(inp, "name", "") == self.socket_label or getattr(inp, "identifier", "").startswith(f"{self.socket_label}_ms_in_"):
+                is_list = is_socket_linked_to_list(inp)
+                set_socket_shape(inp, "LIST" if is_list else "CIRCLE")
+
+    def evaluate_output(self, socket_name: str, **kwargs) -> list[Any]:
+        from ....infra.blender.list_utils import flatten_list, is_list_data
+        items: list[Any] = []
+        raw_inputs = self.resolve_multi_input(self.socket_label)
+        for val in raw_inputs:
+            if val is not None:
+                if is_list_data(val):
+                    items.extend(flatten_list(val))
+                else:
+                    items.append(val)
+        return items
+
 class ExecSliceNode(SliceNode):
     button_label: str = 'Execute'
     

core/nodeslicer/nodes/gcode.py

@@ -1,15 +1,24 @@
 from __future__ import annotations
+from typing import Any
 import numpy as np
 import bpy
 import os
 
 from ..bpy_ns_types import NfBoolProperty, NfEnumProperty, NfStringProperty
 from ....registry import register_class
-from .base import SliceNode, SliceIntrinsics, Pather, SliceNodeJoiner
+from .base import SliceNode, SliceIntrinsics, Pather, SliceNodeJoiner, SliceNodeListJoiner
+from ....infra.blender.list_utils import eval_element_wise, flatten_list, is_list_data
+
+@register_class
+class SLICENODE_GcodesToList(SliceNodeListJoiner):
+    bl_label = "Gcodes to List"
+    socket_type = "NodeSocketString"
+    socket_label = "Gcode"
 
 @register_class
 class SLICENODE_PathsToGcode(SliceNode):
     bl_label = "Paths to Gcode"
+    list_socket_mapping = [("Paths", "Gcode")]
 
     use_header: bool = NfBoolProperty(name="Header", default=True)
 
@@ -22,19 +31,23 @@ class SLICENODE_PathsToGcode(SliceNode):
         assert layout
         layout.prop(self, "use_header")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> str:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
-        paths: list[np.ndarray] = self.resolve("Paths")
+        paths: Any = self.resolve("Paths")
         intrinsics: SliceIntrinsics | None = self.resolve("Intrinsics")
 
-        pather: Pather = Pather(paths)
+        if not paths:
-        if hasattr(paths, "layer_height"):
+            return ""
-            pather.layer_height = getattr(paths, "layer_height")
+
-        if hasattr(paths, "first_layer_height"):
+        def _paths_to_gcode(p: Any) -> str:
-            pather.first_layer_height = getattr(paths, "first_layer_height")
+            if not p:
+                return ""
+            pather: Pather = Pather(p)
+            if hasattr(p, "layer_height"):
+                pather.layer_height = getattr(p, "layer_height")
+            if hasattr(p, "first_layer_height"):
+                pather.first_layer_height = getattr(p, "first_layer_height")
 
             if intrinsics:
-            # Note: Pather currently uses bed_center_x/y as its internal attributes.
-            # We map the bed size center to these attributes if provided.
                 pather.bed_center_x = intrinsics.bed_x / 2.0
                 pather.bed_center_y = intrinsics.bed_y / 2.0
                 pather.feedrate = intrinsics.feedrate
@@ -44,8 +57,9 @@ class SLICENODE_PathsToGcode(SliceNode):
                 pather.retraction_feedrate = getattr(intrinsics, "retraction_feedrate", 0.0)
                 pather.lift = intrinsics.lift
 
-        gcode: str = pather.to_gcode(include_header=self.use_header)
+            return pather.to_gcode(include_header=self.use_header)
-        return gcode
+
+        return eval_element_wise(_paths_to_gcode, paths)
 
 @register_class
 class SLICENODE_GcodeBlock(SliceNode):
@@ -83,6 +97,7 @@ class SLICENODE_AssignMetadata(SliceNode):
 @register_class
 class SLICENODE_GcodeRegexReplace(SliceNode):
     bl_label = "Gcode Regex Replace"
+    list_socket_mapping = [("Gcode", "Gcode")]
 
     def init(self, context):
         self.add_input("NodeSocketString", "Gcode")
@@ -90,15 +105,22 @@ class SLICENODE_GcodeRegexReplace(SliceNode):
         self.add_input("NodeSocketString", "Replace")
         self.add_output("NodeSocketString", "Gcode")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> str:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         import re
-        gcode = self.resolve("Gcode") or ""
+        gcode = self.resolve("Gcode")
         find = self.resolve("Find") or ""
         replace = self.resolve("Replace") or ""
 
+        if not gcode:
+            return ""
+
         if not find:
             return gcode
 
+        def _replace_one(gc: Any) -> str:
+            gc_str = str(gc or "")
+            if not find or not gc_str:
+                return gc_str
             try:
                 # Convert $1, $2, ${name} etc to Python backreferences \g<1>, \g<2>, \g<name>
                 def subst(match):
@@ -107,12 +129,13 @@ class SLICENODE_GcodeRegexReplace(SliceNode):
                     elif match.group(3): return '\\g<' + match.group(3) + '>'
                     return match.group(0)
 
-            replace = re.sub(r'(\$\$)|(?:\$\{([^}]+)\})|(?:\$([a-zA-Z0-9_]+))', subst, replace)
+                rep = re.sub(r'(\$\$)|(?:\$\{([^}]+)\})|(?:\$([a-zA-Z0-9_]+))', subst, replace)
-
+                return re.sub(find, rep, gc_str)
-            return re.sub(find, replace, gcode)
             except Exception as e:
                 print(f"Regex error in node {self.name}: {e}")
-            return gcode
+                return gc_str
+
+        return eval_element_wise(_replace_one, gcode)
 
 @register_class
 class SLICENODE_GcodeHelper(SliceNode):
@@ -180,17 +203,53 @@ class SLICENODE_JoinGcode(SliceNodeJoiner):
     output_socket_type = "NodeSocketString"
     socket_label = "Gcode"
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> str:
+    def update(self) -> None:
-        from ....infra.blender.blender_slice_nodes_generic import resolve_input
+        super().update()
-        gcode_input: list[str] = []
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
-        for input in self.inputs:
+        has_list = any(
-            val = resolve_input(input)
+            is_socket_linked_to_list(inp)
-            if val is not None:
+            for inp in self.inputs
-                gc = str(val)
+            if getattr(inp, "name", "") == self.socket_label or getattr(inp, "identifier", "").startswith(f"{self.socket_label}_ms_in_")
-                if gc:
+        )
-                    gcode_input.append(gc)
+        out_sock = self.outputs.get(self.socket_label)
+        if out_sock:
+            set_socket_shape(out_sock, "LIST" if has_list else "CIRCLE")
+
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
+        raw_inputs = self.resolve_multi_input(self.socket_label)
+        has_list = any(is_list_data(inp) for inp in raw_inputs)
+
+        if not has_list:
+            flattened = flatten_list(raw_inputs)
+            gcode_input: list[str] = [str(gc) for gc in flattened if gc]
             return "\n".join(gcode_input)
 
+        # There is at least one list input
+        list_lengths = [len(inp) for inp in raw_inputs if is_list_data(inp)]
+        if len(set(list_lengths)) > 1:
+            raise ValueError(
+                f"Join Gcode: all input lists must have the same length, got lengths {list_lengths}"
+            )
+
+        n_elements = list_lengths[0] if list_lengths else 0
+        result: list[str] = []
+        for i in range(n_elements):
+            row_parts: list[str] = []
+            for inp in raw_inputs:
+                if is_list_data(inp):
+                    val = inp[i]
+                else:
+                    val = inp
+                if is_list_data(val):
+                    val_str = "\n".join(str(s) for s in flatten_list(val) if s)
+                    if val_str:
+                        row_parts.append(val_str)
+                elif val:
+                    row_parts.append(str(val))
+            result.append("\n".join(row_parts))
+
+        return result
+
 @register_class
 class SLICENODE_LoadGcode(SliceNode):
     bl_label = "Load Gcode File"

core/nodeslicer/nodes/inputs.py

@@ -6,7 +6,7 @@ import numpy as np
 
 from ..bpy_ns_types import NfStringProperty, notify_tree_changed, NfEnumProperty, NfPointerProperty
 from ....registry import register_class
-from .base import InputNode, SliceNode, SliceIntrinsics
+from .base import InputNode, SliceNode, SliceIntrinsics, SliceNodeListJoiner
 
 @register_class
 class SLICENODE_InputString(InputNode):
@@ -39,6 +39,13 @@ class SLICENODE_InputObject(InputNode):
     socket_type = "NodeSocketObject"
     bl_icon = "OBJECT_DATA"
 
+@register_class
+class SLICENODE_ObjectsToList(SliceNodeListJoiner):
+    bl_label = "Objects to List"
+    socket_type = "NodeSocketObject"
+    socket_label = "Object"
+    output_socket_name = "Objects"
+
 @register_class
 class SLICENODE_CollectionObjects(SliceNode):
     bl_label = "Collection Objects"

core/nodeslicer/nodes/mesh.py

@@ -4,14 +4,16 @@ import numpy as np
 
 from ..bpy_ns_types import NfBoolProperty, NfEnumProperty, NfIntProperty, NfFloatProperty, NfStringProperty, NfFloatVectorProperty, notify_tree_changed
 from ....registry import register_class
-from .base import SliceNode, SlicingCollection, get_all_children, SliceNodeJoiner, SlicingGroup, SlicingObject, SlicePaths
+from .base import SliceNode, SlicingCollection, get_all_children, SliceNodeJoiner, SliceNodeListJoiner, SlicingGroup, SlicingObject, SlicePaths
 from ....infra.blender.blender_mesh_capture import PdfProperties
 from ....core.pdf_exporter.geometry import transform_slice_paths
 from ....core.geometry import update_transform
+from ....infra.blender.list_utils import eval_element_wise, flatten_list, is_list_data
 
 @register_class
 class SLICENODE_GetMesh(SliceNode):
     bl_label = "Get Mesh"
+    list_socket_mapping = [("Object", "Mesh")]
 
     include_children: bool = NfBoolProperty(name="Include Children", default=True)
 
@@ -23,17 +25,25 @@ class SLICENODE_GetMesh(SliceNode):
         assert layout
         layout.prop(self, "include_children")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicingCollection | None:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         if socket_name != "Mesh": return None
 
         obj: Any = self.resolve("Object")
         if not obj: return None
 
-        family = [obj] + (get_all_children(obj) if self.include_children else [])
+        def _to_collection(o: Any) -> SlicingCollection | None:
+            if not o: return None
+            family = [o] + (get_all_children(o) if self.include_children else [])
+            return SlicingCollection(family, getattr(o, "name", "Mesh"))
 
-        sc: SlicingCollection = SlicingCollection(family, obj.name)
+        return eval_element_wise(_to_collection, obj)
 
-        return sc
+@register_class
+class SLICENODE_MeshesToList(SliceNodeListJoiner):
+    bl_label = "Meshes to List"
+    socket_type = "SLICESOCK_Mesh"
+    socket_label = "Mesh"
+    output_socket_name = "Meshes"
 
 @register_class
 class SLICENODE_JoinMesh(SliceNodeJoiner):
@@ -42,16 +52,20 @@ class SLICENODE_JoinMesh(SliceNodeJoiner):
 
     def evaluate_output(self, socket_name: str, **_kwargs) -> SlicingCollection:
         from ....infra.blender.blender_slice_nodes_generic import resolve_input
-        first_coll = resolve_input(self.inputs[0]) if self.inputs else None
+        all_colls = []
-        merged_coll = SlicingCollection([], first_coll.name if first_coll else '')
+        for inp in self.inputs:
-        if first_coll:
+            if getattr(inp, "is_linked", False) or getattr(inp, "value", None):
-            merged_coll.objects = list(first_coll.objects)
+                val = resolve_input(inp)
-            merged_coll.transforms = [dict(t) for t in getattr(first_coll, "transforms", [])]
+                if val:
+                    all_colls.extend(flatten_list(val))
 
-        for input in self.inputs[1:]:
+        first_coll = all_colls[0] if all_colls else None
-            coll = resolve_input(input)
+        merged_coll = SlicingCollection([], first_coll.name if first_coll else '')
-            if coll: 
+        for coll in all_colls:
+            if hasattr(coll, "objects"):
                 merged_coll.objects += list(coll.objects)
+            elif isinstance(coll, SlicingObject):
+                merged_coll.objects.append(coll)
             for t in getattr(coll, "transforms", []):
                 if t not in merged_coll.transforms:
                     merged_coll.transforms.append(dict(t))
@@ -71,11 +85,16 @@ class SLICENODE_JoinMeshGroups(SliceNodeJoiner):
         from ....infra.blender.blender_slice_nodes_generic import resolve_input
         group: SlicingGroup = SlicingGroup([])
 
-        for idx, input_socket in enumerate(self.inputs):
+        all_colls = []
-            coll = resolve_input(input_socket)
+        for input_socket in self.inputs:
-            if coll:
+            if getattr(input_socket, "is_linked", False) or getattr(input_socket, "value", None):
+                val = resolve_input(input_socket)
+                if val:
+                    all_colls.extend(flatten_list(val))
+
+        for idx, coll in enumerate(all_colls):
             col_name = getattr(coll, "name", "")
-                if not col_name and coll.objects:
+            if not col_name and getattr(coll, "objects", None):
                 col_name = coll.objects[0].name
             if not col_name:
                 col_name = f"collection_{idx}"
@@ -86,6 +105,7 @@ class SLICENODE_JoinMeshGroups(SliceNodeJoiner):
 @register_class
 class SLICENODE_SeparateMesh(SliceNode):
     bl_label = "Separate Mesh"
+    list_socket_mapping = [("Mesh", ["Selection", "Inverted"])]
 
     comparison: str = NfEnumProperty(
         name="Comparison",
@@ -112,19 +132,19 @@ class SLICENODE_SeparateMesh(SliceNode):
         assert layout
         layout.prop(self, "comparison", text="")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicingCollection | None:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
-        coll: SlicingCollection | None = self.resolve("Mesh")
+        coll: Any = self.resolve("Mesh")
         attr_name: str = self.resolve("Attribute")
         value: float = self.resolve("Value")
 
         if not coll: return None
 
-        res_selection = SlicingCollection([], coll.name + "_selection")
+        def _split_coll(sc: SlicingCollection) -> tuple[SlicingCollection, SlicingCollection]:
-        res_inverted = SlicingCollection([], coll.name + "_inverted")
+            res_selection = SlicingCollection([], sc.name + "_selection")
+            res_inverted = SlicingCollection([], sc.name + "_inverted")
 
-        for so in coll.objects:
+            for so in sc.objects:
                 if attr_name not in so.attributes:
-                # If attribute missing, entire object goes to inverted
                     res_inverted.objects.append(so)
                     continue
                 
@@ -144,7 +164,6 @@ class SLICENODE_SeparateMesh(SliceNode):
                 elif not np.any(mask):
                     res_inverted.objects.append(so)
                 else:
-                # Split the object
                     so_sel = SlicingObject()
                     so_sel.name = so.name + "_sel"
                     so_sel.parent = so.parent
@@ -174,7 +193,13 @@ class SLICENODE_SeparateMesh(SliceNode):
                             "values": v["values"][~mask]
                         }
                     res_inverted.objects.append(so_inv)
+            return res_selection, res_inverted
 
+        if is_list_data(coll):
+            results = [_split_coll(c) for c in coll]
+            return [r[0] for r in results] if socket_name == "Selection" else [r[1] for r in results]
+
+        res_selection, res_inverted = _split_coll(coll)
         if socket_name == "Selection":
             return res_selection
         return res_inverted
@@ -202,8 +227,13 @@ class SLICENODE_SeparateMeshByRange(SliceNode):
         end = max(start, end_val)
         expected_ids = [str(i) for i in range(start, end + 1)]
 
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
+        inp = self.inputs.get("Mesh") if hasattr(self, "inputs") else None
+        is_list = is_socket_linked_to_list(inp) if inp is not None else False
+        if inp is not None:
+            set_socket_shape(inp, "LIST" if is_list else "CIRCLE")
+
         # Remove outputs that are no longer in the range
-        # We use a list to avoid modification-during-iteration issues
         to_remove = [o for o in self.outputs if o.identifier not in expected_ids]
         for o in to_remove:
             self.outputs.remove(o)
@@ -211,7 +241,9 @@ class SLICENODE_SeparateMeshByRange(SliceNode):
         # Add new outputs
         for id_str in expected_ids:
             if id_str not in self.outputs:
-                self.add_output("SLICESOCK_Mesh", id_str, identifier=id_str)
+                self.add_output("SLICESOCK_Mesh", id_str, identifier=id_str, display_shape="LIST" if is_list else "")
+            else:
+                set_socket_shape(self.outputs[id_str], "LIST" if is_list else "CIRCLE")
         
         # Re-order to match range
         for i, id_str in enumerate(expected_ids):
@@ -225,8 +257,8 @@ class SLICENODE_SeparateMeshByRange(SliceNode):
         col.prop(self, "start_val")
         col.prop(self, "end_val")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicingCollection | None:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
-        coll: SlicingCollection | None = self.resolve("Mesh")
+        coll: Any = self.resolve("Mesh")
         attr_name: str = self.resolve("Attribute")
 
         if not coll: return None
@@ -237,15 +269,16 @@ class SLICENODE_SeparateMeshByRange(SliceNode):
         except ValueError:
             return None
 
-        res = SlicingCollection([], f"{coll.name}_{target_val}")
+        start = int(self.start_val) if isinstance(getattr(self, "start_val", None), (int, float)) else 0
-
+        end_val = int(self.end_val) if isinstance(getattr(self, "end_val", None), (int, float)) else 1
-        start = self.start_val
+        end = max(start, end_val)
-        end = max(start, self.end_val)
         total_parts = end - start + 1
         num_digits = max(2, len(str(total_parts)))
         i = target_val - start
 
-        for so in coll.objects:
+        def _split_coll(sc: SlicingCollection) -> SlicingCollection:
+            res = SlicingCollection([], f"{sc.name}_{target_val}")
+            for so in sc.objects:
                 if attr_name not in so.attributes:
                     continue
                 
@@ -272,12 +305,14 @@ class SLICENODE_SeparateMeshByRange(SliceNode):
                             "values": v["values"][mask]
                         }
                     res.objects.append(so_new)
-
             return res
 
+        return eval_element_wise(_split_coll, coll)
+
 @register_class
 class SLICENODE_ArrangeMesh(SliceNode):
     bl_label = "Arrange Slicing Group"
+    list_socket_mapping = [("Slicing Group", "Slicing Group")]
 
     method: str = NfEnumProperty(
         name="Method",
@@ -297,11 +332,11 @@ class SLICENODE_ArrangeMesh(SliceNode):
     )
 
     def init(self, context):
-        self.add_input("SLICESOCK_Mesh", "Slicing Group", display_shape='LIST')
+        self.add_input("SLICESOCK_Mesh", "Slicing Group")
         self.add_input("NodeSocketFloat", "Bed X").value = 250.0
         self.add_input("NodeSocketFloat", "Bed Y").value = 250.0
         self.add_input("NodeSocketFloat", "Spacing").value = 2.0
-        self.add_output("SLICESOCK_Mesh", "Slicing Group", display_shape='LIST')
+        self.add_output("SLICESOCK_Mesh", "Slicing Group")
 
     def draw_buttons(self, context, layout):
         assert layout
@@ -320,9 +355,22 @@ class SLICENODE_ArrangeMesh(SliceNode):
         bed_y: float = self.resolve("Bed Y") or 250.0
         spacing: float = self.resolve("Spacing") or 2.0
 
-        # Convert input to SlicingGroup if it's a SlicingCollection
+        # Convert input to SlicingGroup if it's a SlicingCollection or list
+        is_list = is_list_data(mesh_data)
         if isinstance(mesh_data, SlicingGroup):
             slicing_group = mesh_data
+        elif is_list:
+            slicing_group = SlicingGroup([])
+            for idx, item in enumerate(mesh_data):
+                if isinstance(item, SlicingGroup):
+                    for k, sc in item.collections.items():
+                        slicing_group.collections[f"{k}_{idx}"] = sc
+                elif isinstance(item, SlicingCollection):
+                    col_name = item.name or f"mesh_{idx}"
+                    slicing_group.collections[col_name] = item
+                elif isinstance(item, SlicingObject):
+                    sc = SlicingCollection([item], item.name or f"mesh_{idx}")
+                    slicing_group.collections[sc.name] = sc
         else:
             slicing_group = SlicingGroup([])
             slicing_group.collections = {mesh_data.name: mesh_data}
@@ -419,8 +467,8 @@ class SLICENODE_ArrangeMesh(SliceNode):
                     so.mesh[:, 3, 1] = ny_new
             else:
                 name, sc = collection_map[id(item)]
-                print(f"Warning: Collection '{name}' did not fit on the build plate (binId: {bin_id})")
+        if is_list:
-
+            return list(copied_group.collections.values())
         return copied_group
 
 
@@ -515,6 +563,7 @@ def _transform_geometry_item(geom: Any, t_arr: np.ndarray, r_arr: np.ndarray, s_
 @register_class
 class SLICENODE_TransformGeometry(SliceNode):
     bl_label = "Transform Geometry"
+    list_socket_mapping = [("Geometry", "Geometry")]
 
     def init(self, context):
         self.add_input("SLICESOCK_Geometry", "Geometry")
@@ -545,6 +594,7 @@ class SLICENODE_TransformGeometry(SliceNode):
 @register_class
 class SLICENODE_DropGeometry(SliceNode):
     bl_label = "Drop Geometry"
+    list_socket_mapping = [("Mesh", ["Mesh", "Translation"])]
 
     def init(self, context):
         self.add_input("SLICESOCK_Mesh", "Mesh")
@@ -552,23 +602,8 @@ class SLICENODE_DropGeometry(SliceNode):
         self.add_output("SLICESOCK_Mesh", "Mesh")
         self.add_output("NodeSocketVector", "Translation")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicingCollection | SlicingGroup | tuple[float, float, float] | None:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
-        if socket_name == "Translation":
+        mesh_data: Any = self.resolve("Mesh")
-            mesh_data: SlicingCollection | SlicingGroup | None = self.resolve("Mesh")
-            if not mesh_data:
-                return None
-            z = self.resolve('Z')
-            if z is None:
-                z = 0.0
-            assert mesh_data.min_z is not None
-            min_z = round(mesh_data.min_z, 6)
-            offset_z = float(z - min_z)
-            return (0.0, 0.0, offset_z)
-        
-        if socket_name != "Mesh":
-            return None
-
-        mesh_data = self.resolve("Mesh")
         if not mesh_data:
             return None
 
@@ -576,18 +611,17 @@ class SLICENODE_DropGeometry(SliceNode):
         if z is None:
             z = 0.0
 
-        assert mesh_data.min_z is not None
+        def _drop_item(item: Any) -> tuple[Any, tuple[float, float, float]]:
-        min_z = round(mesh_data.min_z, 6)
+            if not item or getattr(item, "min_z", None) is None:
+                return item, (0.0, 0.0, 0.0)
+            min_z = round(item.min_z, 6)
             offset_z = float(z - min_z)
-
+            if isinstance(item, SlicingGroup):
-        if isinstance(mesh_data, SlicingGroup):
+                copied_data = _copy_slicing_group(item)
-            copied_data = _copy_slicing_group(mesh_data)
             else:
-            copied_data = _copy_slicing_collection(mesh_data)
+                copied_data = _copy_slicing_collection(item)
-
             drop_vec = np.array([0.0, 0.0, offset_z], dtype=np.float64)
             copied_data.offset(drop_vec)
-
             copied_data.transforms = update_transform(getattr(copied_data, "transforms", []), t_arr=drop_vec)
             if isinstance(copied_data, SlicingGroup):
                 for col in copied_data.collections.values():
@@ -597,8 +631,18 @@ class SLICENODE_DropGeometry(SliceNode):
             elif isinstance(copied_data, SlicingCollection):
                 for so in copied_data.objects:
                     so.transforms = update_transform(getattr(so, "transforms", []), t_arr=drop_vec)
+            return copied_data, (0.0, 0.0, offset_z)
 
-        return copied_data
+        if is_list_data(mesh_data):
+            results = [_drop_item(m) for m in mesh_data]
+            if socket_name == "Translation":
+                return [r[1] for r in results]
+            return [r[0] for r in results]
+
+        dropped, trans = _drop_item(mesh_data)
+        if socket_name == "Translation":
+            return trans
+        return dropped
 
 
 def format_name_template(template: str, so: Any, default_old_name: str = "") -> str:
@@ -664,6 +708,7 @@ def _rename_slicing_item(geom: Any, new_name: str) -> Any:
 @register_class
 class SLICENODE_RenameMesh(SliceNode):
     bl_label = "Rename Mesh"
+    list_socket_mapping = [("Geometry", "Geometry")]
 
     def init(self, context):
         self.add_input("SLICESOCK_Mesh", "Geometry")
@@ -716,6 +761,7 @@ def _assign_pdf_properties_to_item(geom: Any, line_width: float, line_color: tup
 @register_class
 class SLICENODE_AssignPdfProperties(SliceNode):
     bl_label = "Assign PDF Properties"
+    list_socket_mapping = [("Geometry", "Geometry")]
 
     line_width: float = NfFloatProperty(name="Line Width (mm)", default=0.0, min=0.0, max=50.0)
     line_color: tuple[float, float, float] = NfFloatVectorProperty(
@@ -777,7 +823,7 @@ def _assign_properties_to_item(geom: Any, props: list[tuple[str, str]]) -> Any:
         return copied
     elif isinstance(geom, SlicingObject):
         copied = _copy_slicing_object(geom)
-        copied.pdf_object_properties = resolve_object_properties(copied, props)
+        copied.pdf_object_properties = resolve_object_properties(geom, props)
         return copied
     return geom
 
@@ -785,6 +831,7 @@ def _assign_properties_to_item(geom: Any, props: list[tuple[str, str]]) -> Any:
 @register_class
 class SLICENODE_AssignPropertyToObject(SliceNode):
     bl_label = "Assign PDF Object Properties"
+    list_socket_mapping = [("Geometry", "Geometry")]
 
     def init(self, context):
         self.add_input("SLICESOCK_Mesh", "Geometry")

core/nodeslicer/nodes/output.py

@@ -23,13 +23,22 @@ class SLICENODE_GcodeToFile(ExecSliceNode):
         self.add_input("NodeSocketString", "Name")
         self.add_multi_socket_group("NodeSocketString", name="Gcode")
 
+    def update(self) -> None:
+        super().update()
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
+        for inp in self.inputs:
+            if getattr(inp, "name", "") == "Gcode" or getattr(inp, "identifier", "").startswith("Gcode_ms_in_"):
+                set_socket_shape(inp, "LIST" if is_socket_linked_to_list(inp) else "CIRCLE")
+
     def draw_buttons(self, context, layout):
         super().draw_buttons(context, layout)
 
     def evaluate(self, operator=None):
         from ....infra.networking.gcode_utils import get_gcode_name_from_metadata, prepare_gcode_file
+        from ....infra.blender.list_utils import flatten_list
 
-        gcodes: list[str] = [gc for gc in self.resolve_multi_input('Gcode') if gc]
+        raw_gcodes = self.resolve_multi_input('Gcode')
+        gcodes: list[str] = [str(gc) for gc in flatten_list(raw_gcodes) if gc]
 
         folder: str = self.resolve("Folder")
         if not gcodes:
@@ -86,20 +95,37 @@ class SLICENODE_GcodeToTextBlock(ExecSliceNode):
         self._init_exec()
         self.add_input("NodeSocketString", "Gcode")
 
+    def update(self) -> None:
+        super().update()
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
+        inp = self.inputs.get("Gcode")
+        if inp:
+            set_socket_shape(inp, "LIST" if is_socket_linked_to_list(inp) else "CIRCLE")
+
     def draw_buttons(self, context, layout):
         super().draw_buttons(context, layout)
         layout.prop(self, "text_block_name")
 
     def evaluate(self, operator=None):
-        gcode: str = self.resolve("Gcode")
+        from ....infra.blender.list_utils import flatten_list, is_list_data
-        if not gcode:
+        raw = self.resolve("Gcode")
+        if not raw:
             return 'ok'
 
-        name = self.text_block_name
+        gcodes = [str(g) for g in flatten_list(raw) if g] if is_list_data(raw) else ([str(raw)] if raw else [])
+        if not gcodes:
+            return 'ok'
+
+        base_name = self.text_block_name
+        name_root, ext = os.path.splitext(base_name)
+        total_parts = len(gcodes)
+        num_digits = max(2, len(str(total_parts)))
+
+        for i, gcode in enumerate(gcodes):
+            name = f"{name_root}_{i:0{num_digits}d}{ext}" if total_parts > 1 else base_name
             text_block = bpy.data.texts.get(name)
             if text_block is None:
                 text_block = bpy.data.texts.new(name=name)
-
             text_block.from_string(gcode)
 
         # Attempt to show in an open text editor
@@ -124,6 +150,13 @@ class SLICENODE_StartPrint(ExecSliceNode):
         self.add_input("SLICESOCK_Printer")
 
     def evaluate(self, operator=None):
+        from ....infra.blender.list_utils import is_list_data
+
+        raw_gcode = self.resolve("Gcode")
+        if is_list_data(raw_gcode):
+            if operator: operator.report({'ERROR'}, "Start Print does not accept a list of Gcode")
+            return 'error'
+
         from ....infra.networking.printer_backends import (
             PrinterConfig, 
             PrusaLinkBackend, 
@@ -131,7 +164,7 @@ class SLICENODE_StartPrint(ExecSliceNode):
             MoonrakerBackend
         )
 
-        gcode: str = self.resolve("Gcode")
+        gcode: str = str(raw_gcode or "")
         config: PrinterConfig | None = self.resolve("Printer")
 
         if not gcode:
@@ -192,6 +225,13 @@ class ExecSliceNode_DatabaseSubmit(ExecSliceNode):
         self.add_input("NodeSocketString", "Gcode")
         self.add_input("SLICESOCK_Settings", "Metadata")
 
+    def update(self) -> None:
+        super().update()
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
+        inp = self.inputs.get("Gcode")
+        if inp:
+            set_socket_shape(inp, "LIST" if is_socket_linked_to_list(inp) else "CIRCLE")
+
     def draw_buttons(self, context, layout):
         super().draw_buttons(context, layout)
         layout.prop(self, "record_id")
@@ -199,8 +239,9 @@ class ExecSliceNode_DatabaseSubmit(ExecSliceNode):
     def evaluate(self, operator=None):
         from ....infra.networking.bgcode import convert_to_bgcode
         from ....infra.networking.gcode_utils import get_gcode_name_from_metadata, parse_gcode_metadata
+        from ....infra.blender.list_utils import flatten_list
 
-        gcodes: list[str] = self.resolve_multi_input("Gcode")
+        gcodes: list[str] = [str(gc) for gc in flatten_list(self.resolve_multi_input("Gcode")) if gc]
 
         for gc in gcodes:
             if not gc:
@@ -413,6 +454,14 @@ class SLICENODE_MeshToPdf(ExecSliceNode):
         self.add_input("SLICESOCK_Mesh", "Geometry")
         self.add_input("SLICESOCK_Paths", "Paths")
 
+    def update(self) -> None:
+        super().update()
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
+        for name in ("Geometry", "Paths"):
+            inp = self.inputs.get(name)
+            if inp:
+                set_socket_shape(inp, "LIST" if is_socket_linked_to_list(inp) else "CIRCLE")
+
     def draw_buttons(self, context, layout):
         super().draw_buttons(context, layout)
         

core/nodeslicer/nodes/path.py

@@ -4,12 +4,20 @@ import numpy as np
 
 from ..bpy_ns_types import NfEnumProperty, NfBoolProperty, NfFloatProperty, notify_tree_changed
 from ....registry import register_class
-from .base import SliceNode, SlicePaths, SlicingObject, SlicingCollection, slice_at_range, SliceNodeJoiner, SlicingGroup
+from .base import SliceNode, SlicePaths, SlicingObject, SlicingCollection, slice_at_range, SliceNodeJoiner, SliceNodeListJoiner, SlicingGroup
 from ...slice import align_path_seam_sharpest, is_closed_path
+from ....infra.blender.list_utils import eval_element_wise, is_list_data, set_socket_shape, is_socket_linked_to_list
+
+@register_class
+class SLICENODE_PathsToList(SliceNodeListJoiner):
+    bl_label = "Paths to List"
+    socket_type = "SLICESOCK_Paths"
+    socket_label = "Paths"
 
 @register_class
 class SLICENODE_GetPaths(SliceNode):
     bl_label = "Get Paths"
+    list_socket_mapping = [("Object", "Paths")]
 
     def init(self, context):
         self.add_input("NodeSocketObject")
@@ -21,78 +29,34 @@ class SLICENODE_GetPaths(SliceNode):
     def draw_buttons(self, context, layout):
         pass
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         obj: Any = self.resolve("Object")
         e_attr_name: str = self.resolve("Extrusion Multiplier Attribute")
         f_attr_name: str = self.resolve("Feedrate Attribute")
         extra_attrs: dict[str, str] = self.resolve("Extra Attributes")
 
         from ....infra.blender.blender_mesh_capture import capture_mesh_edges
-        so, e_rates, f_rates, extra_attrs_data = capture_mesh_edges(obj, e_attr_name, f_attr_name, extra_attrs)
 
+        def _get_single_path(o: Any) -> SlicePaths:
+            if not o:
+                return SlicePaths()
+            so, e_rates, f_rates, extra_attrs_data = capture_mesh_edges(o, e_attr_name, f_attr_name, extra_attrs)
             sp = SlicePaths(so, extrusion_rate=e_rates, feedrate=f_rates, extra_attributes=extra_attrs_data)
-        if hasattr(obj, "transforms"):
+            if hasattr(o, "transforms"):
-            sp.transforms = list(getattr(obj, "transforms", []))
+                sp.transforms = list(getattr(o, "transforms", []))
-        if hasattr(obj, "name") and getattr(obj, "name"):
+            if hasattr(o, "name") and getattr(o, "name"):
-            name_val = str(getattr(obj, "name"))
+                name_val = str(getattr(o, "name"))
                 sp.name = name_val
                 sp.objects_info = {"objects": [{"name": name_val, "polygon": []}]}
             return sp
 
-@register_class
+        return eval_element_wise(_get_single_path, obj)
-class SLICENODE_SliceShells(SliceNode):
-    bl_label = "Slice Shells"
 
-    ignore_holes: bool = NfBoolProperty(
+def _slice_single_mesh_item(coll: Any, layer_height: float, fl_height: float | None, rotation: Any, ignore_holes: bool) -> SlicePaths:
-        name="Ignore Holes",
+    if not coll:
-        description="Ignore interior hole boundaries and generate only outer shells",
+        return SlicePaths()
-        default=False
-    )
 
-    def init(self, context):
+    # Handle SlicingGroup, SlicingCollection, SlicingObject
-        self.add_input("SLICESOCK_Mesh")
-        self.add_input("NodeSocketFloat", "Layer Height").value = 0.2
-        self.add_input("NodeSocketFloat", "First Layer Height").value = 0.2
-        self.add_input("NodeSocketRotation", "Rotation")
-        self.add_output("SLICESOCK_Paths")
-
-    def draw_buttons(self, context, layout):
-        assert layout
-        if hasattr(self, "ignore_holes"):
-            layout.prop(self, "ignore_holes")
-
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
-        if socket_name != "Paths": return SlicePaths()
-
-        coll: Any = self.resolve("Mesh")
-        layer_height: float = float(self.resolve("Layer Height") or 0.2)
-        if layer_height <= 0:
-            layer_height = 0.2
-
-        fl_height: float | None = None
-        try:
-            fl_val = self.resolve("First Layer Height")
-            if fl_val is not None:
-                fl_height = float(fl_val)
-        except Exception:
-            fl_height = None
-        if fl_height is not None and fl_height <= 0:
-            fl_height = None
-
-        rotation: Any = self.resolve("Rotation") or (0.0, 0.0, 0.0)
-
-        ignore_holes: bool = bool(getattr(self, "ignore_holes", False))
-        if hasattr(self, "inputs") and "Ignore Holes" in self.inputs:
-            try:
-                val = self.resolve("Ignore Holes")
-                if val is not None:
-                    ignore_holes = bool(val)
-            except Exception:
-                pass
-
-        if not coll: return SlicePaths()
-
-        # Handle SlicingGroup, SlicingCollection, SlicingObject, or list
     if isinstance(coll, SlicingGroup):
         objects = []
         for c in coll.collections.values():
@@ -101,16 +65,6 @@ class SLICENODE_SliceShells(SliceNode):
         objects = list(coll.objects)
     elif isinstance(coll, SlicingObject):
         objects = [coll]
-        elif isinstance(coll, list):
-            objects = []
-            for item in coll:
-                if isinstance(item, SlicingGroup):
-                    for c in item.collections.values():
-                        objects.extend(c.objects)
-                elif isinstance(item, SlicingCollection):
-                    objects.extend(item.objects)
-                elif isinstance(item, SlicingObject):
-                    objects.append(item)
     else:
         objects = getattr(coll, "objects", [coll] if hasattr(coll, "mesh") else [])
 
@@ -158,7 +112,6 @@ class SLICENODE_SliceShells(SliceNode):
         return SlicePaths()
 
     paths = slices_group[0]
-        # Assign layer-consistent group indices based on Z height in integer microns
     z_to_group: dict[int, int] = {}
     groups = []
     for p in paths:
@@ -209,9 +162,69 @@ class SLICENODE_SliceShells(SliceNode):
 
     return slices
 
+@register_class
+class SLICENODE_SliceShells(SliceNode):
+    bl_label = "Slice Shells"
+    list_socket_mapping = [("Mesh", "Paths")]
+
+    ignore_holes: bool = NfBoolProperty(
+        name="Ignore Holes",
+        description="Ignore interior hole boundaries and generate only outer shells",
+        default=False
+    )
+
+    def init(self, context):
+        self.add_input("SLICESOCK_Mesh")
+        self.add_input("NodeSocketFloat", "Layer Height").value = 0.2
+        self.add_input("NodeSocketFloat", "First Layer Height").value = 0.2
+        self.add_input("NodeSocketRotation", "Rotation")
+        self.add_output("SLICESOCK_Paths")
+
+    def draw_buttons(self, context, layout):
+        assert layout
+        if hasattr(self, "ignore_holes"):
+            layout.prop(self, "ignore_holes")
+
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
+        if socket_name != "Paths": return SlicePaths()
+
+        coll: Any = self.resolve("Mesh")
+        layer_height: float = float(self.resolve("Layer Height") or 0.2)
+        if layer_height <= 0:
+            layer_height = 0.2
+
+        fl_height: float | None = None
+        try:
+            fl_val = self.resolve("First Layer Height")
+            if fl_val is not None:
+                fl_height = float(fl_val)
+        except Exception:
+            fl_height = None
+        if fl_height is not None and fl_height <= 0:
+            fl_height = None
+
+        rotation: Any = self.resolve("Rotation") or (0.0, 0.0, 0.0)
+
+        ignore_holes: bool = bool(getattr(self, "ignore_holes", False))
+        if hasattr(self, "inputs") and "Ignore Holes" in self.inputs:
+            try:
+                val = self.resolve("Ignore Holes")
+                if val is not None:
+                    ignore_holes = bool(val)
+            except Exception:
+                pass
+
+        if not coll: return SlicePaths()
+
+        def _slice_one(item: Any) -> SlicePaths:
+            return _slice_single_mesh_item(item, layer_height, fl_height, rotation, ignore_holes)
+
+        return eval_element_wise(_slice_one, coll)
+
 @register_class
 class SLICENODE_BufferShells(SliceNode):
     bl_label = "Buffer Shells"
+    list_socket_mapping = [("Paths", "Paths")]
 
     shape_option: str = NfEnumProperty(
         name="Miter",
@@ -232,21 +245,26 @@ class SLICENODE_BufferShells(SliceNode):
         assert layout
         layout.prop(self, "shape_option")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         if socket_name != "Paths": return SlicePaths()
 
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         distance_val = self.resolve("Distance")
         distance: float = float(distance_val) if distance_val is not None else 0.0
         rotation: Any = self.resolve("Rotation") or (0.0, 0.0, 0.0)
 
         if not paths: return SlicePaths()
 
-        return paths.buffer(distance, miter=self.shape_option, rotation=rotation)
+        def _buf(p: Any) -> SlicePaths:
+            if not p: return SlicePaths()
+            return p.buffer(distance, miter=self.shape_option, rotation=rotation)
+
+        return eval_element_wise(_buf, paths)
 
 @register_class
 class SLICENODE_BufferCurve(SliceNode):
     bl_label = "Buffer Curve"
+    list_socket_mapping = [("Paths", "Paths")]
 
     cap_style: str = NfEnumProperty(
         name="Cap Style",
@@ -286,16 +304,18 @@ class SLICENODE_BufferCurve(SliceNode):
         layout.prop(self, "join_style")
         layout.prop(self, "single_sided")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         if socket_name != "Paths": return SlicePaths()
 
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         distance: float = self.resolve("Distance") or 0.0
         rotation: Any = self.resolve("Rotation") or (0.0, 0.0, 0.0)
 
         if not paths: return SlicePaths()
 
-        return paths.buffer_curve(
+        def _buf(p: Any) -> SlicePaths:
+            if not p: return SlicePaths()
+            return p.buffer_curve(
                 distance,
                 cap_style=self.cap_style,
                 join_style=self.join_style,
@@ -303,9 +323,12 @@ class SLICENODE_BufferCurve(SliceNode):
                 rotation=rotation
             )
 
+        return eval_element_wise(_buf, paths)
+
 @register_class
 class SLICENODE_OffsetCurve(SliceNode):
     bl_label = "Offset Curve"
+    list_socket_mapping = [("Paths", "Paths")]
 
     join_style: str = NfEnumProperty(
         name="Join Style",
@@ -327,24 +350,29 @@ class SLICENODE_OffsetCurve(SliceNode):
         assert layout
         layout.prop(self, "join_style")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         if socket_name != "Paths": return SlicePaths()
 
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         distance: float = self.resolve("Distance") or 0.0
         rotation: Any = self.resolve("Rotation") or (0.0, 0.0, 0.0)
 
         if not paths: return SlicePaths()
 
-        return paths.offset_curve(
+        def _off(p: Any) -> SlicePaths:
+            if not p: return SlicePaths()
+            return p.offset_curve(
                 distance,
                 join_style=cast(Literal['round', 'mitre'], self.join_style),
                 rotation=rotation
             )
 
+        return eval_element_wise(_off, paths)
+
 @register_class
 class SLICENODE_PathOffset(SliceNode):
     bl_label = "Path Offset"
+    list_socket_mapping = [("Paths", "Paths")]
 
     def init(self, context):
         self.add_input("SLICESOCK_Paths", "Paths")
@@ -352,16 +380,21 @@ class SLICENODE_PathOffset(SliceNode):
         self.add_output("SLICESOCK_Paths", "Paths")
 
     def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         offset: Any = self.resolve("Offset") or (0.0, 0.0, 0.0)
 
         if not paths: return SlicePaths()
         
-        return paths.offset(np.array(offset, dtype=np.float64))
+        def _off(p: Any) -> SlicePaths:
+            if not p: return SlicePaths()
+            return p.offset(np.array(offset, dtype=np.float64))
+
+        return eval_element_wise(_off, paths)
 
 @register_class
 class SLICENODE_RotatePath(SliceNode):
     bl_label = "Rotate Path"
+    list_socket_mapping = [("Paths", "Paths")]
 
     def init(self, context):
         self.add_input("SLICESOCK_Paths", "Paths")
@@ -370,7 +403,7 @@ class SLICENODE_RotatePath(SliceNode):
         self.add_output("SLICESOCK_Paths", "Paths")
 
     def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         angle: float = self.resolve("Angle") or 0.0
         center: Any = self.resolve("Center")
 
@@ -378,11 +411,16 @@ class SLICENODE_RotatePath(SliceNode):
 
         center_vec = np.array(center, dtype=np.float64) if center and any(center) else None
 
-        return paths.rotate(angle, center=center_vec)
+        def _rot(p: Any) -> SlicePaths:
+            if not p: return SlicePaths()
+            return p.rotate(angle, center=center_vec)
+
+        return eval_element_wise(_rot, paths)
 
 @register_class
 class SLICENODE_BufferShellsMultiple(SliceNode):
     bl_label = "Buffer Shells Multiple"
+    list_socket_mapping = [("Paths", ["Paths", "Outermost Path", "Innermost Path"])]
 
     shape_option: str = NfEnumProperty(
         name="Miter",
@@ -407,8 +445,8 @@ class SLICENODE_BufferShellsMultiple(SliceNode):
         assert layout
         layout.prop(self, "shape_option")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         base_distance_val = self.resolve("Distance")
         base_distance: float = float(base_distance_val) if base_distance_val is not None else 0.0
         width_step_val = self.resolve("Width Step")
@@ -420,20 +458,25 @@ class SLICENODE_BufferShellsMultiple(SliceNode):
         if not paths or count <= 0:
             return SlicePaths()
 
+        def _buf_multi(p: Any) -> SlicePaths:
+            if not p or count <= 0:
+                return SlicePaths()
             if socket_name == "Outermost Path":
                 outer_dist = max(base_distance, base_distance + (count - 1) * width_step) if count > 1 else base_distance
-            return paths.buffer(outer_dist, miter=self.shape_option, rotation=rotation)
+                return p.buffer(outer_dist, miter=self.shape_option, rotation=rotation)
             elif socket_name == "Innermost Path":
                 inner_dist = min(base_distance, base_distance + (count - 1) * width_step) if count > 1 else base_distance
-            return paths.buffer(inner_dist, miter=self.shape_option, rotation=rotation)
+                return p.buffer(inner_dist, miter=self.shape_option, rotation=rotation)
             elif socket_name == "Paths":
-            return paths.buffer_multiple(base_distance, count, width_step, miter=self.shape_option, rotation=rotation)
+                return p.buffer_multiple(base_distance, count, width_step, miter=self.shape_option, rotation=rotation)
-
             return SlicePaths()
 
+        return eval_element_wise(_buf_multi, paths)
+
 @register_class
 class SLICENODE_Infill(SliceNode):
     bl_label = "Infill"
+    list_socket_mapping = [("Paths", "Paths")]
 
     infill_type: str = NfEnumProperty(
         name="Type",
@@ -457,26 +500,31 @@ class SLICENODE_Infill(SliceNode):
         assert layout
         layout.prop(self, "infill_type", text="")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         if socket_name != "Paths": return SlicePaths()
 
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         density: float = self.resolve("Density") or 2.0
         infill_rotation: float = self.resolve("Infill Rotation") or 0.0
         rotation: Any = self.resolve("Layer Rotation") or (0.0, 0.0, 0.0)
 
         if not paths: return SlicePaths()
 
-        return paths.infill(
+        def _inf(p: Any) -> SlicePaths:
+            if not p: return SlicePaths()
+            return p.infill(
                 density, 
                 rotation_deg=infill_rotation,
-            infill_type=self.infill_type, # pyright: ignore[reportOptionalMemberAccess]
+                infill_type=self.infill_type,
                 layer_rotation=rotation
             )
 
+        return eval_element_wise(_inf, paths)
+
 @register_class
 class SLICENODE_OverhangMask(SliceNode):
     bl_label = "Overhang Mask"
+    list_socket_mapping = [("Paths", "Paths")]
 
     def init(self, context):
         self.add_input("SLICESOCK_Paths")
@@ -486,15 +534,19 @@ class SLICENODE_OverhangMask(SliceNode):
     def draw_buttons(self, context, layout):
         pass
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         if socket_name != "Paths": return SlicePaths()
 
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         tolerance: float = self.resolve("Tolerance") or 0.05
 
         if not paths: return SlicePaths()
 
-        return paths.get_overhang_mask(tolerance=tolerance)
+        def _mask(p: Any) -> SlicePaths:
+            if not p: return SlicePaths()
+            return p.get_overhang_mask(tolerance=tolerance)
+
+        return eval_element_wise(_mask, paths)
 
 @register_class
 class SLICENODE_PathOperations(SliceNodeJoiner):
@@ -522,37 +574,56 @@ class SLICENODE_PathOperations(SliceNodeJoiner):
         default=False
     )
 
+    def update(self) -> None:
+        super().update()
+        if self.inputs:
+            first_inp = self.inputs[0]
+            is_list = is_socket_linked_to_list(first_inp)
+            set_socket_shape(first_inp, "LIST" if is_list else "CIRCLE")
+            if self.outputs:
+                set_socket_shape(self.outputs[0], "LIST" if is_list else "CIRCLE")
+
     def draw_buttons(self, context, layout):
         assert layout
         layout.prop(self, "operation", text="")
         if self.operation in ['MIN_COVERAGE', 'INTERSECTION', 'SUBTRACT']:
             layout.prop(self, "connect_along_boundary")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         from ....infra.blender.blender_slice_nodes_generic import resolve_input
 
-        inputs_data: list[SlicePaths] = []
+        if not self.inputs:
-        for input_socket in self.inputs:
-            if hasattr(input_socket, "is_linked") and not input_socket.is_linked:
-                continue
-            paths: Any = resolve_input(input_socket)
-            if isinstance(paths, SlicePaths) and len(paths) > 0:
-                inputs_data.append(paths)
-
-        if not inputs_data:
             return SlicePaths()
 
-        output = SlicePaths.path_operations(
+        first_val = resolve_input(self.inputs[0]) if (self.inputs[0].is_linked or getattr(self.inputs[0], 'value', None)) else None
+        other_paths: list[SlicePaths] = []
+        for input_socket in self.inputs[1:]:
+            if getattr(input_socket, "is_linked", False):
+                val = resolve_input(input_socket)
+                if isinstance(val, SlicePaths) and len(val) > 0:
+                    other_paths.append(val)
+
+        def _run_op(primary_path: Any) -> SlicePaths:
+            inputs_data = [p for p in [primary_path] + other_paths if isinstance(p, SlicePaths) and len(p) > 0]
+            if not inputs_data:
+                return SlicePaths()
+            return SlicePaths.path_operations(
                 inputs_data,
                 operation=self.operation,
                 connect_along_boundary=self.connect_along_boundary
             )
-        return output
+
+        if is_list_data(first_val):
+            return [_run_op(item) for item in first_val]
+        elif isinstance(first_val, SlicePaths) or other_paths:
+            return _run_op(first_val)
+        return SlicePaths()
 
 
 @register_class
 class SLICENODE_SimplifyPaths(SliceNode):
     bl_label = "Simplify Paths"
+    list_socket_mapping = [("Paths", "Paths")]
 
     preserve_topology: bool = NfBoolProperty(
         name="Preserve Topology",
@@ -569,21 +640,27 @@ class SLICENODE_SimplifyPaths(SliceNode):
         assert layout
         layout.prop(self, "preserve_topology")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         if socket_name != "Paths":
             return SlicePaths()
 
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         tolerance: float = self.resolve("Tolerance") or 0.0
         if not paths or tolerance <= 0:
             return paths
 
-        return paths.simplify(tolerance, preserve_topology=self.preserve_topology)
+        def _simp(p: Any) -> SlicePaths:
+            if not p or tolerance <= 0:
+                return p
+            return p.simplify(tolerance, preserve_topology=self.preserve_topology)
+
+        return eval_element_wise(_simp, paths)
 
 
 @register_class
 class SLICENODE_SeamPlacement(SliceNode):
     bl_label = "Seam Placement"
+    list_socket_mapping = [("Paths", "Paths")]
 
     mode: str = NfEnumProperty(
         name="Mode",
@@ -614,11 +691,11 @@ class SLICENODE_SeamPlacement(SliceNode):
         layout.prop(self, "mode", text="")
         layout.prop(self, "acquire_transforms")
 
-    def evaluate_output(self, socket_name: str, **_kwargs) -> SlicePaths:
+    def evaluate_output(self, socket_name: str, **_kwargs) -> Any:
         if socket_name != "Paths":
             return SlicePaths()
 
-        paths: SlicePaths = self.resolve("Paths")
+        paths = self.resolve("Paths")
         mesh_input: Any = self.resolve("Mesh")
         stagger_val = self.resolve("Seam Staggering")
         stagger_mm: float = float(stagger_val) if stagger_val is not None else 0.0
@@ -626,10 +703,15 @@ class SLICENODE_SeamPlacement(SliceNode):
         if not paths:
             return SlicePaths()
 
-        if not mesh_input and abs(stagger_mm) < 1e-6:
-            return paths
-
         acquire_t = bool(getattr(self, "acquire_transforms", True))
-        return paths.place_seams(mesh_input, mode=self.mode.lower(), acquire_transforms=acquire_t, stagger_mm=stagger_mm)
+
+        def _place(p: Any) -> SlicePaths:
+            if not p:
+                return SlicePaths()
+            if not mesh_input and abs(stagger_mm) < 1e-6:
+                return p
+            return p.place_seams(mesh_input, mode=self.mode.lower(), acquire_transforms=acquire_t, stagger_mm=stagger_mm)
+
+        return eval_element_wise(_place, paths)
 
 

core/nodeslicer/nodes/preview.py

@@ -20,6 +20,13 @@ class SLICENODE_GcodeToMesh(ExecSliceNode):
         self.add_input("NodeSocketString", "Name")
         self.add_multi_socket_group("NodeSocketString", name="Gcode")
 
+    def update(self) -> None:
+        super().update()
+        from ....infra.blender.list_utils import is_socket_linked_to_list, set_socket_shape
+        for inp in self.inputs:
+            if getattr(inp, "name", "") == "Gcode" or getattr(inp, "identifier", "").startswith("Gcode_ms_in_"):
+                set_socket_shape(inp, "LIST" if is_socket_linked_to_list(inp) else "CIRCLE")
+
     def draw_buttons(self, context, layout):
         super().draw_buttons(context, layout)
         layout.prop(self, 'show_e_0')
@@ -229,7 +236,9 @@ class SLICENODE_GcodeToMesh(ExecSliceNode):
             mod["Socket_9"] = tuple(map(float, prep_scale))
 
     def evaluate(self, operator=None):
-        gcodes: list[str] = [g for g in (self.resolve_multi_input("Gcode") or []) if g]
+        from ....infra.blender.list_utils import flatten_list
+        raw_gcodes = self.resolve_multi_input("Gcode") or []
+        gcodes: list[str] = [str(g) for g in flatten_list(raw_gcodes) if g]
         base_mesh_name: str = self.resolve("Name")
 
         if not base_mesh_name:

core/nodeslicer/nodes/system.py

@@ -100,6 +100,11 @@ class SLICENODE_PrinterList(ExecSliceNode):
             if not gcode:
                 continue
 
+            from ....infra.blender.list_utils import is_list_data
+            if is_list_data(gcode):
+                if operator: operator.report({'ERROR'}, f"Printer List does not accept a list of Gcode on socket {sock.name}")
+                continue
+
             p_data = printer_configs[sock.name]
             host = str(p_data.get("ip", "localhost"))
             port = int(p_data.get("port", 80))

core/nodeslicer/tree.py

@@ -121,12 +121,23 @@ def depsgraph_update_handler(scene, depsgraph):
     # Sync SLICENODE_Group sockets if interface changed and migrate legacy sockets
     for tree in bpy.data.node_groups:
         if tree.bl_idname == "SLICETREE_NodeTree":
+            try:
+                from ...infra.blender.list_utils import sync_group_tree_internal_sockets
+                sync_group_tree_internal_sockets(tree)
+            except Exception:
+                pass
             for node in tree.nodes:
-                if node.bl_idname == "SLICENODE_Group" and hasattr(node, "sync_sockets"):
+                if node.bl_idname == "SLICENODE_Group":
+                    if hasattr(node, "sync_sockets"):
                         try:
                             node.sync_sockets()
                         except Exception:
                             pass
+                    elif hasattr(node, "sync_socket_shapes"):
+                        try:
+                            node.sync_socket_shapes()
+                        except Exception:
+                            pass
                 elif node.bl_idname == "SLICENODE_CollectionObjects" and hasattr(node, "_update_outputs"):
                     try:
                         node._update_outputs()
@@ -149,9 +160,35 @@ class SLICETREE_NodeTree(NodeTree):
 
     def valid_link(self, from_socket: Any, to_socket: Any) -> bool:
         geom_sockets = {"SLICESOCK_Mesh", "SLICESOCK_Paths", "SLICESOCK_Geometry"}
-        if from_socket.bl_idname in geom_sockets and to_socket.bl_idname in geom_sockets:
+        compatible = (
+            (from_socket.bl_idname in geom_sockets and to_socket.bl_idname in geom_sockets)
+            or from_socket.bl_idname == to_socket.bl_idname
+        )
+        if not compatible:
+            return False
+
+        from ...infra.blender.list_utils import is_output_socket_a_list, group_input_can_accept_list
+        if is_output_socket_a_list(from_socket):
+            to_node = getattr(to_socket, "node", None)
+            if to_node is not None:
+                # Start Print and Printer List reject lists
+                if to_node.bl_idname in ("SLICENODE_StartPrint", "SLICENODE_PrinterList"):
+                    return False
+                # Path Operations: only input 0 can accept a list; secondary inputs reject lists
+                if to_node.bl_idname == "SLICENODE_PathOperations":
+                    if getattr(to_node, "inputs", None) and to_socket != to_node.inputs[0]:
+                        return False
+                # Seam Placement: secondary input (Mesh) rejects lists
+                if to_node.bl_idname == "SLICENODE_SeamPlacement":
+                    if getattr(to_socket, "name", "") == "Mesh":
+                        return False
+                # Group node: check if input can accept list
+                if to_node.bl_idname == "SLICENODE_Group":
+                    tree = getattr(to_node, "slicer_tree", None) or getattr(to_node, "node_tree", None)
+                    if tree and not group_input_can_accept_list(tree, to_socket):
+                        return False
+
         return True
-        return from_socket.bl_idname == to_socket.bl_idname
 
 
 @register_class
@@ -590,6 +627,11 @@ class SLICENODE_MT_Joiners(Menu):
     def draw(self, context):
         layout = self.layout
         assert layout
+        layout.operator("node.add_node", text="Objects to List").type = "SLICENODE_ObjectsToList"
+        layout.operator("node.add_node", text="Meshes to List").type = "SLICENODE_MeshesToList"
+        layout.operator("node.add_node", text="Paths to List").type = "SLICENODE_PathsToList"
+        layout.operator("node.add_node", text="Gcodes to List").type = "SLICENODE_GcodesToList"
+        layout.separator()
         layout.operator("node.add_node", text="Join Mesh Parts").type = "SLICENODE_JoinMesh"
         layout.operator("node.add_node", text="Join Mesh Groups").type = "SLICENODE_JoinMeshGroups"
         layout.operator("node.add_node", text="Path Operations").type = "SLICENODE_PathOperations"

core/slice.py

@@ -1060,6 +1060,7 @@ def shift_path_seam_by_distance(
 
 
 class SlicePaths(list[np.ndarray]):
+    is_slice_paths: bool = True
     groups: list[int]
     extrusion_rate: list[np.ndarray]
     feedrate: list[np.ndarray]

doc/MODULES.md

@@ -72,3 +72,9 @@ This file provides a mapping of modules to their primary responsibilities and ke
     - `get_last_debug_dump()` / `get_last_debug_text()` / `load_last_inputs()`: Utilities to review and reload the most recent execution dump for debugging.
     - `debug_session()`: Context manager enabling execution capture across node evaluations.
     - `SLICENODE_OT_DebugDump`: Blender operator (`slicenode.debug_dump`) to dump the active node's inputs on demand.
+
+- `list_utils.py`:
+    - `is_list_data()`: Type discrimination distinguishing list/tuple collections from atomic objects (such as `SlicePaths`).
+    - `flatten_list()`: Recursive flattener for multi-input joiners and batch sinks.
+    - `eval_element_wise()`: Vectorized applicator executing operations element-wise on lists or directly on single items.
+    - `set_socket_shape()` / `is_socket_linked_to_list()` / `is_output_socket_a_list()` / `sync_node_list_sockets()`: Dynamic socket visual appearance management (`LIST` vs `CIRCLE`).

doc/NODES.md

@@ -168,10 +168,14 @@ All nodes are found in the **Add (Shift+A)** menu under the **SliceNodes** categ
 - **Load Gcode**: Reads a G-code file from disk.
 
 ### Utility & Joiners
-- **Join Mesh Parts**: Merges multiple `SlicingObject` instances into one `SlicingCollection`.
+- **Objects to List**: Multi-input list joiner that bundles objects into a `list[bpy.types.Object]` with LIST socket shape. Flattens incoming lists.
-- **Join Mesh Groups**: Combines multiple `SlicingCollection` instances into a `SlicingGroup`.
+- **Meshes to List**: Multi-input list joiner that bundles meshes into a `list[SlicingCollection]` with LIST socket shape. Flattens incoming lists.
-- **Path Operations**: Multi-input joiner performing Zip, Extend, Maximum coverage, Minimum coverage, Intersection, Subtract, and XOR operations.
+- **Paths to List**: Multi-input list joiner that bundles toolpaths into a `list[SlicePaths]` with LIST socket shape. Flattens incoming lists.
-- **Join Gcode**: Concatenates multiple G-code strings.
+- **Gcodes to List**: Multi-input list joiner that bundles G-code strings into a `list[str]` with LIST socket shape. Flattens incoming lists.
+- **Join Mesh Parts**: Merges multiple `SlicingObject` instances into one `SlicingCollection`. Flattens incoming lists.
+- **Join Mesh Groups**: Combines multiple `SlicingCollection` instances into a `SlicingGroup`. Flattens incoming lists.
+- **Path Operations**: Multi-input joiner performing Zip, Extend, Maximum coverage, Minimum coverage, Intersection, Subtract, and XOR operations. The first input can be a list, in which case the operation runs per-element against the same secondary inputs.
+- **Join Gcode**: Concatenates multiple G-code inputs. If no input is a list, concatenates scalar strings into a single string (CIRCLE). If one or more inputs are lists (which must all be the same length), outputs a list of strings (LIST) where each element at index $i$ is joined with static elements broadcast across all indices.
 - **Join Settings**: Sequentially merges multiple override dictionaries. Later inputs overwrite earlier ones for matching keys.
 - **Join Execution**: Synchronizes sequential execution flows.
 

doc/nodes_list_behavior.csv

@@ -1,4 +1,4 @@
-Type,Category,Node Name,Class Name,File,Archetype,First Input Socket,Other Input Sockets,Output Socket(s),First Input Shape,Output Shape,Single Item Behavior,List Behavior
+Type,Category,Node Name,Class Name,File,Archetype,First Input Socket,Other Input Sockets,Output Socket(s),First Input Shape,Output Shape,Single Item Behavior,List Behavior
 Object,List Joiners (New),Objects to List,SLICENODE_ObjectsToList,core/nodeslicer/nodes/inputs.py,List Joiner,Multi-input NodeSocketObject (Object),None,NodeSocketObject (Objects),Standard / LIST,Fixed LIST,Wraps single item into a 1-element list [Obj1],Flattens incoming lists and combines all objects into list[bpy.types.Object]. Output appearance is LIST.
 Mesh,List Joiners (New),Meshes to List,SLICENODE_MeshesToList,core/nodeslicer/nodes/mesh.py,List Joiner,Multi-input SLICESOCK_Mesh (Mesh),None,SLICESOCK_Mesh (Meshes),Standard / LIST,Fixed LIST,Wraps single mesh into a 1-element list [Mesh1],Flattens incoming lists and bundles all meshes into list[SlicingCollection]. Output appearance is LIST.
 Path,List Joiners (New),Paths to List,SLICENODE_PathsToList,core/nodeslicer/nodes/path.py,List Joiner,Multi-input SLICESOCK_Paths (Paths),None,SLICESOCK_Paths (Paths),Standard / LIST,Fixed LIST,Wraps single path into a 1-element list [Path1],Flattens incoming lists and bundles all toolpaths into list[SlicePaths]. Output appearance is LIST.
@@ -33,8 +33,8 @@ Path,G-code Processing,Paths to Gcode,SLICENODE_PathsToGcode,core/nodeslicer/nod
 Gcode,G-code Processing,Gcode Regex Replace,SLICENODE_GcodeRegexReplace,core/nodeslicer/nodes/gcode.py,Element-wise Operator,NodeSocketString (Gcode),"Find, Replace (cannot be list)",NodeSocketString (Gcode),Dynamic (Changes to LIST if input is list),Dynamic (Changes to LIST if input is list),Runs regex find & replace on G-code string,"First input is list [G1, G2, ...]. Runs regex search and replace on each G-code string using the same pattern. Output is [G1', G2', ...]. Sockets switch to LIST."
 Gcode,Action & I/O,Gcode to File,SLICENODE_GcodeToFile,core/nodeslicer/nodes/output.py,Batch Sink,NodeSocketString (Gcode) [Can be a list or multi-input],"Folder, Name (cannot be list)",Execution Link,Dynamic (Displays LIST if input is list),Standard Execution Link,Saves G-code string to .gcode or .bgcode file on disk,"First input is list [G1, G2, ...]. Saves a separate file for each element using the same folder/name template with zero-padded numbering (Part00.gcode, Part01.gcode) or metadata names."
 Gcode,Action & I/O,Gcode to Text Block,SLICENODE_GcodeToTextBlock,core/nodeslicer/nodes/output.py,Batch Sink,NodeSocketString (Gcode) [Can be a list],Text Block Name (cannot be list),Execution Link,Dynamic (Displays LIST if input is list),Standard Execution Link,Writes G-code string to an active Blender text editor data-block,"First input is list [G1, G2, ...]. Writes separate numbered Blender text blocks (NodeSlicer_00.gcode, NodeSlicer_01.gcode) using the base name."
-Gcode,Action & I/O,Start Print,SLICENODE_StartPrint,core/nodeslicer/nodes/output.py,Batch Sink,NodeSocketString (Gcode) [Can be a list],SLICESOCK_Printer (cannot be list),Execution Link,Dynamic (Displays LIST if input is list),Standard Execution Link,Uploads and starts print on network printer,"First input is list [G1, G2, ...]. Sequentially queues and sends each G-code print job to the target printer using the same printer configuration."
+Gcode,Action & I/O,Start Print,SLICENODE_StartPrint,core/nodeslicer/nodes/output.py,Single Item Sink,NodeSocketString (Gcode) [Single item only],SLICESOCK_Printer (Single item only),Execution Link,Standard (CIRCLE),Standard Execution Link,Uploads and starts print on network printer,List is not accepted. Sockets reject list connections and evaluate() reports an error if a list is received.
 Gcode,Action & I/O,Baserow Submit,SLICENODE_BaserowSubmit,core/nodeslicer/nodes/output.py,Batch Sink,NodeSocketString (Gcode) [Can be a list or multi-input],"Settings, Host, Token, Table ID, Record ID (cannot be list)",Execution Link,Dynamic (Displays LIST if input is list),Standard Execution Link,Uploads G-code attachment and creates/updates row in Baserow database,"First input is list [G1, G2, ...]. Submits each G-code as a separate record and attachment in Baserow using the same database credentials."
 Gcode,Action & I/O,Airtable Submit,SLICENODE_AirtableSubmit,core/nodeslicer/nodes/output.py,Batch Sink,NodeSocketString (Gcode) [Can be a list or multi-input],"Settings, PAT File, Base ID, Table ID, Record ID (cannot be list)",Execution Link,Dynamic (Displays LIST if input is list),Standard Execution Link,Uploads G-code attachment and creates/updates row in Airtable base,"First input is list [G1, G2, ...]. Submits each G-code as a separate record and attachment in Airtable using the same database credentials."
 Gcode,Action & I/O,Gcode to Preview Mesh,SLICENODE_GcodeToMesh,core/nodeslicer/nodes/preview.py,Batch Sink,NodeSocketString (Gcode) [Can be a list or multi-input],"Name, show_e_0 (cannot be list)",Execution Link,Dynamic (Displays LIST if input is list),Standard Execution Link,Decodes toolpaths and reconstructs 3D wireframe preview mesh object in Blender,"First input is list [G1, G2, ...]. Generates a separate preview mesh object in the scene (Preview00, Preview01, ...) for each G-code in the list."
-Gcode,Action & I/O,Printer List,SLICENODE_PrinterList,core/nodeslicer/nodes/system.py,Batch Sink,Dynamic G-code sockets per printer [Can be a list],Config File JSON (cannot be list),Execution Link,Dynamic (Displays LIST if input is list),Standard Execution Link,Sends G-code to corresponding printer defined in config JSON,"If a printer socket receives a list [G1, G2, ...], queues and dispatches all jobs for that printer."
+Gcode,Action & I/O,Printer List,SLICENODE_PrinterList,core/nodeslicer/nodes/system.py,Single Item Sink,Dynamic G-code sockets per printer [Single item only],Config File JSON (cannot be list),Execution Link,Standard (CIRCLE),Standard Execution Link,Sends G-code to corresponding printer defined in config JSON,List is not accepted. Sockets reject list connections and evaluate() ignores list inputs.

infra/blender/blender_slice_nodes_generic.py

@@ -9,6 +9,8 @@ from bpy.types import NodeSocket, Node
 
 class NodeException(Exception): ...
 
+from .list_utils import is_list_data, flatten_list, eval_element_wise, set_socket_shape, is_socket_linked_to_list, sync_node_list_sockets
+
 _EvalCache = dict[Any, Any]
 _VisitedSet = set[Any]
 
@@ -116,8 +118,17 @@ class SliceNode(Node, AutoBlIdName):
             return key in self._data
         return False
 
+    list_socket_mapping: list[tuple[str, list[str] | str]] = []
+
     def update(self) -> None: 
         self._update_multi_groups()
+        self._sync_list_socket_shapes()
+
+    def _sync_list_socket_shapes(self) -> None:
+        mapping = getattr(self, "list_socket_mapping", None)
+        if mapping:
+            from .list_utils import sync_node_list_sockets
+            sync_node_list_sockets(self, mapping)
 
     def evaluate_output(self, socket_name: str, **_kwargs) -> Any: ...
 
@@ -475,6 +486,21 @@ class SLICENODE_Group(bpy.types.NodeCustomGroup, AutoBlIdName):
         # 3. Sync Outputs
         self._sync_socket_collection(self.outputs, expected_outputs)
 
+        # 4. Sync Socket Shapes (LIST vs CIRCLE)
+        self.sync_socket_shapes()
+
+    def sync_socket_shapes(self):
+        try:
+            if not self.name or not self.slicer_tree:
+                return
+        except Exception:
+            return
+        from .list_utils import sync_group_node_socket_shapes
+        sync_group_node_socket_shapes(self)
+
+    def update(self):
+        self.sync_socket_shapes()
+
     def _sync_socket_collection(self, collection, expected):
         # Remove sockets that shouldn't be there
         expected_ids = {e[0] for e in expected}

infra/blender/list_utils.py

@@ -0,0 +1,563 @@
+from __future__ import annotations
+from typing import Any, Callable
+
+LIST_CAPABLE_SOCKET_TYPES = {
+    "SLICESOCK_Mesh",
+    "SLICESOCK_Paths",
+    "SLICESOCK_Object",
+    "SLICESOCK_Geometry",
+    "NodeSocketObject",
+    "NodeSocketString",
+}
+
+def is_list_data(val: Any) -> bool:
+    """Checks if val represents a list of items (Object, Mesh, Path, Gcode).
+    Note: SlicePaths is a list subclass representing an individual toolpath collection,
+    not a list of toolpaths, so it is treated as an atomic item (not list data)."""
+    if val is None or isinstance(val, (str, bytes)):
+        return False
+    if type(val).__name__ == "SlicePaths" or getattr(val, "is_slice_paths", False):
+        return False
+    return isinstance(val, (list, tuple))
+
+def flatten_list(items: Any) -> list[Any]:
+    """Recursively flattens nested lists/tuples, keeping atomic items intact."""
+    result: list[Any] = []
+    if not is_list_data(items):
+        if items is not None:
+            result.append(items)
+        return result
+    for item in items:
+        if is_list_data(item):
+            result.extend(flatten_list(item))
+        elif item is not None:
+            result.append(item)
+    return result
+
+def eval_element_wise(op_func: Callable[[Any], Any], data: Any) -> Any:
+    """If data is a list, applies op_func to each element and returns a list.
+    Otherwise applies op_func to data directly."""
+    if is_list_data(data):
+        return [op_func(item) for item in data]
+    return op_func(data)
+
+def set_socket_shape(sock: Any, shape: str) -> None:
+    """Safely updates socket display_shape property ('LIST', 'CIRCLE', etc.)."""
+    if sock is not None:
+        try:
+            sock.display_shape = shape
+        except (AttributeError, TypeError):
+            pass
+
+def _follow_reroute_upstream(sock: Any, visited: set | None = None) -> Any:
+    """Follows reroute nodes backwards to find the original source output socket."""
+    if visited is None:
+        visited = set()
+    current = sock
+    while (
+        current is not None
+        and getattr(current, "node", None) is not None
+        and getattr(current.node, "bl_idname", "") == "NodeReroute"
+        and getattr(current.node, "inputs", None)
+        and current.node.inputs[0].is_linked
+        and current.node.inputs[0].links
+    ):
+        ptr = current.as_pointer() if hasattr(current, "as_pointer") else id(current)
+        if ptr in visited:
+            break
+        visited.add(ptr)
+        current = current.node.inputs[0].links[0].from_socket
+    return current
+
+def _follow_reroute_downstream(reroute_node: Any, visited: set | None = None) -> list[Any]:
+    """Follows reroute nodes forwards to find all downstream target input sockets."""
+    if visited is None:
+        visited = set()
+    node_ptr = reroute_node.as_pointer() if hasattr(reroute_node, "as_pointer") else id(reroute_node)
+    if node_ptr in visited:
+        return []
+    visited.add(node_ptr)
+
+    targets: list[Any] = []
+    for outp in getattr(reroute_node, "outputs", []):
+        for link in getattr(outp, "links", []):
+            to_sock = link.to_socket
+            to_node = getattr(to_sock, "node", None)
+            if to_node and getattr(to_node, "bl_idname", "") == "NodeReroute":
+                targets.extend(_follow_reroute_downstream(to_node, visited))
+            else:
+                targets.append(to_sock)
+    return targets
+
+def socket_accepts_list(sock: Any, visited: set | None = None) -> bool:
+    """Determines whether a given input socket can accept a list input."""
+    if sock is None:
+        return False
+    if visited is None:
+        visited = set()
+    sock_ptr = sock.as_pointer() if hasattr(sock, "as_pointer") else id(sock)
+    if sock_ptr in visited:
+        return False
+    visited.add(sock_ptr)
+
+    node = getattr(sock, "node", None)
+    if node is None:
+        return False
+
+    bl_idname = getattr(node, "bl_idname", "")
+
+    # Strictly forbidden nodes
+    if bl_idname in ("SLICENODE_StartPrint", "SLICENODE_PrinterList"):
+        return False
+
+    # Path Operations: only input 0 can accept a list
+    if bl_idname == "SLICENODE_PathOperations":
+        inputs = getattr(node, "inputs", None)
+        if inputs and sock != inputs[0]:
+            return False
+        return True
+
+    # Seam Placement: "Mesh" input rejects lists; "Paths" accepts lists
+    if bl_idname == "SLICENODE_SeamPlacement":
+        if getattr(sock, "name", "") == "Mesh":
+            return False
+        return True
+
+    # Socket type check
+    sock_type = getattr(sock, "bl_idname", "")
+    if sock_type not in LIST_CAPABLE_SOCKET_TYPES:
+        return False
+
+    # String sockets: only Gcode accepts lists
+    if sock_type == "NodeSocketString":
+        sock_name = getattr(sock, "name", "")
+        if bl_idname == "SLICENODE_JoinGcode":
+            return True
+        if bl_idname in ("SLICENODE_WriteGcode", "SLICENODE_ExecuteGcode"):
+            return sock_name == "Gcode"
+        if bl_idname == "SLICENODE_GcodeRegexReplace":
+            return sock_name == "Gcode"
+        if bl_idname == "SLICENODE_GcodesToList":
+            return True
+        if bl_idname == "NodeGroupOutput":
+            return sock_name.lower().startswith("gcode")
+        if bl_idname == "SLICENODE_Group":
+            inner_tree = getattr(node, "slicer_tree", None) or getattr(node, "node_tree", None)
+            if inner_tree:
+                return group_input_can_accept_list(inner_tree, sock, visited)
+            return False
+        return False
+
+    # Reroute node: check downstream targets
+    if bl_idname == "NodeReroute":
+        targets = _follow_reroute_downstream(node, visited)
+        if not targets:
+            return False
+        return all(socket_accepts_list(t, visited) for t in targets)
+
+    # NodeGroupOutput
+    if bl_idname == "NodeGroupOutput":
+        return True
+
+    # Nested SLICENODE_Group
+    if bl_idname == "SLICENODE_Group":
+        inner_tree = getattr(node, "slicer_tree", None) or getattr(node, "node_tree", None)
+        if inner_tree:
+            return group_input_can_accept_list(inner_tree, sock, visited)
+        return False
+
+    # List joiners accept lists
+    if getattr(node, "is_list_output", False):
+        return True
+
+    # Data joiners accept lists
+    if bl_idname in ("SLICENODE_JoinMesh", "SLICENODE_JoinMeshGroups", "SLICENODE_JoinGcode"):
+        return True
+
+    # Nodes with list_socket_mapping
+    mapping = getattr(node, "list_socket_mapping", None)
+    if mapping:
+        mapped_in_names = {item[0] for item in mapping}
+        if getattr(sock, "name", "") in mapped_in_names:
+            return True
+
+    return False
+
+def _get_input_interface_item(tree: Any, sock_or_idx_or_ident: Any) -> Any:
+    if not hasattr(tree, "interface"):
+        inputs = getattr(tree, "inputs", [])
+        if isinstance(sock_or_idx_or_ident, int) and 0 <= sock_or_idx_or_ident < len(inputs):
+            return inputs[sock_or_idx_or_ident]
+        ident = getattr(sock_or_idx_or_ident, "identifier", str(sock_or_idx_or_ident))
+        for s in inputs:
+            if s.identifier == ident or s.name == ident:
+                return s
+        return None
+
+    input_items = [
+        item for item in getattr(tree.interface, "items_tree", [])
+        if getattr(item, "item_type", "") == 'SOCKET' and getattr(item, "in_out", "") == 'INPUT'
+    ]
+    if isinstance(sock_or_idx_or_ident, int):
+        if 0 <= sock_or_idx_or_ident < len(input_items):
+            return input_items[sock_or_idx_or_ident]
+        return None
+    ident = getattr(sock_or_idx_or_ident, "identifier", None)
+    name = getattr(sock_or_idx_or_ident, "name", None)
+    if isinstance(sock_or_idx_or_ident, str):
+        ident = sock_or_idx_or_ident
+        name = sock_or_idx_or_ident
+    for item in input_items:
+        if ident and getattr(item, "identifier", None) == ident:
+            return item
+    for item in input_items:
+        if name and getattr(item, "name", None) == name:
+            return item
+    return None
+
+def _get_output_interface_item(tree: Any, sock_or_idx_or_ident: Any) -> Any:
+    if not hasattr(tree, "interface"):
+        outputs = getattr(tree, "outputs", [])
+        if isinstance(sock_or_idx_or_ident, int) and 0 <= sock_or_idx_or_ident < len(outputs):
+            return outputs[sock_or_idx_or_ident]
+        ident = getattr(sock_or_idx_or_ident, "identifier", str(sock_or_idx_or_ident))
+        for s in outputs:
+            if s.identifier == ident or s.name == ident:
+                return s
+        return None
+
+    output_items = [
+        item for item in getattr(tree.interface, "items_tree", [])
+        if getattr(item, "item_type", "") == 'SOCKET' and getattr(item, "in_out", "") == 'OUTPUT'
+    ]
+    if isinstance(sock_or_idx_or_ident, int):
+        if 0 <= sock_or_idx_or_ident < len(output_items):
+            return output_items[sock_or_idx_or_ident]
+        return None
+    ident = getattr(sock_or_idx_or_ident, "identifier", None)
+    name = getattr(sock_or_idx_or_ident, "name", None)
+    if isinstance(sock_or_idx_or_ident, str):
+        ident = sock_or_idx_or_ident
+        name = sock_or_idx_or_ident
+    for item in output_items:
+        if ident and getattr(item, "identifier", None) == ident:
+            return item
+    for item in output_items:
+        if name and getattr(item, "name", None) == name:
+            return item
+    return None
+
+def _find_group_input_socket(tree: Any, item: Any) -> Any:
+    if not item or not hasattr(tree, "nodes"):
+        return None
+    ident = getattr(item, "identifier", "")
+    name = getattr(item, "name", "")
+    for n in tree.nodes:
+        if getattr(n, "bl_idname", "") == "NodeGroupInput":
+            for outp in getattr(n, "outputs", []):
+                if outp.identifier == ident or outp.name == name:
+                    return outp
+    return None
+
+def _find_group_output_socket(tree: Any, item: Any) -> Any:
+    if not item or not hasattr(tree, "nodes"):
+        return None
+    ident = getattr(item, "identifier", "")
+    name = getattr(item, "name", "")
+    for n in tree.nodes:
+        if getattr(n, "bl_idname", "") == "NodeGroupOutput":
+            for inp in getattr(n, "inputs", []):
+                if inp.identifier == ident or inp.name == name:
+                    return inp
+    return None
+
+def group_input_can_accept_list(tree: Any, sock_or_idx_or_ident: Any, visited: set | None = None) -> bool:
+    """Determines whether a group tree input socket can accept a list input."""
+    if not tree:
+        return False
+    if visited is None:
+        visited = set()
+
+    item = _get_input_interface_item(tree, sock_or_idx_or_ident)
+    if not item:
+        return False
+
+    item_key = (tree.as_pointer() if hasattr(tree, "as_pointer") else id(tree), getattr(item, "identifier", id(item)))
+    if item_key in visited:
+        return False
+    visited.add(item_key)
+
+    stype = getattr(item, "socket_type", "") or getattr(item, "bl_idname", "")
+    if stype not in LIST_CAPABLE_SOCKET_TYPES:
+        return False
+
+    gin_sock = _find_group_input_socket(tree, item)
+    if not gin_sock or not getattr(gin_sock, "is_linked", False) or not gin_sock.links:
+        return False
+
+    targets: list[Any] = []
+    for link in gin_sock.links:
+        to_sock = link.to_socket
+        to_node = getattr(to_sock, "node", None)
+        if to_node and getattr(to_node, "bl_idname", "") == "NodeReroute":
+            targets.extend(_follow_reroute_downstream(to_node, visited))
+        else:
+            targets.append(to_sock)
+
+    if not targets:
+        return False
+
+    return all(socket_accepts_list(t, visited) for t in targets)
+
+def is_internal_socket_a_list(group_node: Any, tree: Any, in_sock: Any, visited: set | None = None) -> bool:
+    """Determines whether an internal input socket receives a list within a group context."""
+    if not in_sock or not getattr(in_sock, "is_linked", False) or not in_sock.links:
+        return False
+    from_sock = in_sock.links[0].from_socket
+    from_sock = _follow_reroute_upstream(from_sock, visited)
+    if not from_sock:
+        return False
+    from_node = getattr(from_sock, "node", None)
+    if not from_node:
+        return False
+
+    if getattr(from_node, "is_list_output", False):
+        return True
+
+    if getattr(from_node, "bl_idname", "") == "NodeGroupInput":
+        in_item = _get_input_interface_item(tree, from_sock)
+        if not in_item:
+            return False
+        if group_node is not None:
+            for grp_in in getattr(group_node, "inputs", []):
+                if grp_in.identifier == getattr(in_item, "identifier", None) or grp_in.name == getattr(in_item, "name", None):
+                    return is_socket_linked_to_list(grp_in)
+            return False
+        else:
+            return group_input_can_accept_list(tree, in_item, visited)
+
+    if getattr(from_node, "bl_idname", "") == "SLICENODE_Group":
+        inner = getattr(from_node, "slicer_tree", None) or getattr(from_node, "node_tree", None)
+        if inner:
+            return is_group_output_a_list(from_node, inner, from_sock, visited)
+        return False
+
+    if getattr(from_node, "bl_idname", "") == "SLICENODE_JoinGcode":
+        for inp in getattr(from_node, "inputs", []):
+            if getattr(inp, "name", "") == "Gcode" or getattr(inp, "identifier", "").startswith("Gcode_ms_in_"):
+                if is_internal_socket_a_list(group_node, tree, inp, visited):
+                    return True
+        return False
+
+    mapping = getattr(from_node, "list_socket_mapping", None)
+    if mapping:
+        sock_name = getattr(from_sock, "name", "")
+        for m_in_name, m_out_names in mapping:
+            targets = [m_out_names] if isinstance(m_out_names, str) else list(m_out_names)
+            if sock_name in targets:
+                mapped_inp = getattr(from_node, "inputs", None) and from_node.inputs.get(m_in_name)
+                if mapped_inp:
+                    return is_internal_socket_a_list(group_node, tree, mapped_inp, visited)
+
+    return getattr(from_sock, "display_shape", "") == "LIST"
+
+def is_group_output_a_list(
+    group_node: Any,
+    tree: Any,
+    sock_or_idx_or_ident: Any,
+    visited: set | None = None
+) -> bool:
+    """Determines whether a group tree output socket produces a list."""
+    if not tree:
+        return False
+    if visited is None:
+        visited = set()
+
+    item = _get_output_interface_item(tree, sock_or_idx_or_ident)
+    if not item:
+        return False
+
+    item_key = (
+        tree.as_pointer() if hasattr(tree, "as_pointer") else id(tree),
+        getattr(item, "identifier", id(item)),
+        id(group_node) if group_node else 0,
+    )
+    if item_key in visited:
+        return False
+    visited.add(item_key)
+
+    gout_sock = _find_group_output_socket(tree, item)
+    if not gout_sock or not getattr(gout_sock, "is_linked", False) or not gout_sock.links:
+        return False
+
+    src_sock = gout_sock.links[0].from_socket
+    src_sock = _follow_reroute_upstream(src_sock, visited)
+    if not src_sock:
+        return False
+
+    src_node = getattr(src_sock, "node", None)
+    if not src_node:
+        return False
+
+    src_bl_id = getattr(src_node, "bl_idname", "")
+
+    if getattr(src_node, "is_list_output", False):
+        return True
+
+    if src_bl_id == "SLICENODE_JoinGcode":
+        for inp in getattr(src_node, "inputs", []):
+            if getattr(inp, "name", "") == "Gcode" or getattr(inp, "identifier", "").startswith("Gcode_ms_in_"):
+                if is_internal_socket_a_list(group_node, tree, inp, visited):
+                    return True
+        return False
+
+    if src_bl_id == "SLICENODE_Group":
+        inner_tree = getattr(src_node, "slicer_tree", None) or getattr(src_node, "node_tree", None)
+        if inner_tree:
+            return is_group_output_a_list(src_node, inner_tree, src_sock, visited)
+        return False
+
+    if src_bl_id == "NodeGroupInput":
+        in_item = _get_input_interface_item(tree, src_sock)
+        if not in_item:
+            return False
+        if group_node is not None:
+            for grp_in in getattr(group_node, "inputs", []):
+                if grp_in.identifier == getattr(in_item, "identifier", None) or grp_in.name == getattr(in_item, "name", None):
+                    return is_socket_linked_to_list(grp_in)
+            return False
+        else:
+            return group_input_can_accept_list(tree, in_item, visited)
+
+    mapping = getattr(src_node, "list_socket_mapping", None)
+    if mapping:
+        sock_name = getattr(src_sock, "name", "")
+        for in_name, out_names in mapping:
+            targets = [out_names] if isinstance(out_names, str) else list(out_names)
+            if sock_name in targets:
+                inp = getattr(src_node, "inputs", None) and src_node.inputs.get(in_name)
+                if inp:
+                    return is_internal_socket_a_list(group_node, tree, inp, visited)
+
+    return getattr(src_sock, "display_shape", "") == "LIST"
+
+def sync_group_node_socket_shapes(group_node: Any) -> None:
+    """Updates display_shape property on a SLICENODE_Group node's inputs and outputs."""
+    tree = getattr(group_node, "slicer_tree", None) or getattr(group_node, "node_tree", None)
+    if not tree:
+        return
+    for inp in getattr(group_node, "inputs", []):
+        can_list = group_input_can_accept_list(tree, inp)
+        set_socket_shape(inp, "LIST" if can_list else "CIRCLE")
+    for outp in getattr(group_node, "outputs", []):
+        is_list = is_group_output_a_list(group_node, tree, outp)
+        set_socket_shape(outp, "LIST" if is_list else "CIRCLE")
+
+def sync_group_tree_internal_sockets(tree: Any) -> None:
+    """Updates display_shape property on NodeGroupInput and NodeGroupOutput within a group tree."""
+    if not tree or not hasattr(tree, "nodes"):
+        return
+    for node in tree.nodes:
+        bl_id = getattr(node, "bl_idname", "")
+        if bl_id == "NodeGroupInput":
+            for outp in getattr(node, "outputs", []):
+                if outp.name == "" or outp.identifier == "__extend__":
+                    continue
+                can_list = group_input_can_accept_list(tree, outp)
+                set_socket_shape(outp, "LIST" if can_list else "CIRCLE")
+        elif bl_id == "NodeGroupOutput":
+            for inp in getattr(node, "inputs", []):
+                if inp.name == "" or inp.identifier == "__extend__":
+                    continue
+                is_list = is_group_output_a_list(None, tree, inp)
+                set_socket_shape(inp, "LIST" if is_list else "CIRCLE")
+
+def is_output_socket_a_list(sock: Any, visited: set | None = None) -> bool:
+    """Determines whether an output socket produces a list."""
+    if sock is None:
+        return False
+    if visited is None:
+        visited = set()
+    sock_ptr = sock.as_pointer() if hasattr(sock, "as_pointer") else id(sock)
+    if sock_ptr in visited:
+        return False
+    visited.add(sock_ptr)
+
+    if getattr(sock, "display_shape", "") == "LIST":
+        return True
+
+    node = getattr(sock, "node", None)
+    if node is None:
+        return False
+
+    bl_idname = getattr(node, "bl_idname", "")
+
+    if getattr(node, "is_list_output", False):
+        return True
+
+    if bl_idname == "NodeReroute":
+        inputs = getattr(node, "inputs", None)
+        if inputs and inputs[0].is_linked and inputs[0].links:
+            return is_output_socket_a_list(inputs[0].links[0].from_socket, visited)
+        return False
+
+    if bl_idname == "SLICENODE_JoinGcode":
+        inputs = getattr(node, "inputs", [])
+        return any(
+            is_socket_linked_to_list(inp)
+            for inp in inputs
+            if getattr(inp, "name", "") == "Gcode" or getattr(inp, "identifier", "").startswith("Gcode_ms_in_")
+        )
+
+    if bl_idname == "SLICENODE_Group":
+        tree = getattr(node, "slicer_tree", None) or getattr(node, "node_tree", None)
+        if tree:
+            return is_group_output_a_list(node, tree, sock, visited)
+        return False
+
+    if bl_idname == "NodeGroupInput":
+        tree = getattr(node, "id_data", None)
+        if tree:
+            return group_input_can_accept_list(tree, sock, visited)
+        return False
+
+    mapping = getattr(node, "list_socket_mapping", None)
+    if mapping:
+        sock_name = getattr(sock, "name", "")
+        for in_name, out_names in mapping:
+            targets = [out_names] if isinstance(out_names, str) else list(out_names)
+            if sock_name in targets:
+                inp = getattr(node, "inputs", None) and node.inputs.get(in_name)
+                if inp and is_socket_linked_to_list(inp):
+                    return True
+
+    return False
+
+def is_socket_linked_to_list(sock: Any) -> bool:
+    """Determines whether an input socket is linked to an upstream list output."""
+    if not getattr(sock, "is_linked", False) or not getattr(sock, "links", None):
+        return False
+    from_socket = sock.links[0].from_socket
+    from_socket = _follow_reroute_upstream(from_socket)
+    return is_output_socket_a_list(from_socket)
+
+def sync_node_list_sockets(node: Any, mapping: list[tuple[str, list[str] | str]]) -> None:
+    """Updates display_shape on input and output sockets based on mapping.
+    mapping is a list of tuples: (input_socket_name, output_socket_names)
+    e.g. [('Paths', ['Paths']), ('Mesh', ['Selection', 'Inverted'])]
+    """
+    for in_name, out_names in mapping:
+        inp = getattr(node, "inputs", None) and node.inputs.get(in_name)
+        if inp is None:
+            continue
+        is_list = is_socket_linked_to_list(inp)
+        set_socket_shape(inp, "LIST" if is_list else "CIRCLE")
+
+        if isinstance(out_names, str):
+            targets = [out_names]
+        else:
+            targets = list(out_names)
+        for out_name in targets:
+            out_sock = getattr(node, "outputs", None) and node.outputs.get(out_name)
+            if out_sock is not None:
+                set_socket_shape(out_sock, "LIST" if is_list else "CIRCLE")

tests/test_lists.py

@@ -0,0 +1,671 @@
+import sys
+import unittest
+from unittest.mock import MagicMock
+from pathlib import Path
+import numpy as np
+
+PROJECT_ROOT = Path(__file__).resolve().parent.parent
+sys.path.append(str(PROJECT_ROOT.parent))
+
+# Ensure bpy mocks
+class DummyObject:
+    def __init__(self, name="TestObj"):
+        self.name = name
+
+class DummyMesh: pass
+class DummyBase: pass
+
+mock_types = MagicMock()
+mock_types.NodeSocket = type("NodeSocket", (DummyBase,), {})
+mock_types.Node = type("Node", (DummyBase,), {})
+mock_types.NodeCustomGroup = type("NodeCustomGroup", (DummyBase,), {})
+mock_types.NodeTree = type("NodeTree", (DummyBase,), {})
+mock_types.PropertyGroup = type("PropertyGroup", (DummyBase,), {})
+mock_types.Operator = type("Operator", (DummyBase,), {})
+mock_types.Panel = type("Panel", (DummyBase,), {})
+mock_types.Object = DummyObject
+mock_types.Mesh = DummyMesh
+
+mock_bpy = MagicMock()
+mock_bpy.context.scene = MagicMock()
+mock_bpy.context.scene.unit_settings.scale_length = 0.001
+mock_bpy.types = mock_types
+mock_bpy.path.abspath = lambda path: path.replace("//", "/abs/")
+
+sys.modules['bpy'] = mock_bpy
+sys.modules['bpy.types'] = mock_types
+sys.modules['bpy.props'] = MagicMock()
+sys.modules['bpy.utils'] = MagicMock()
+sys.modules['bpy.utils.previews'] = MagicMock()
+sys.modules['bpy.app'] = MagicMock()
+sys.modules['bpy.app.handlers'] = MagicMock()
+
+from NodeSlicer.infra.blender.list_utils import (
+    is_list_data,
+    flatten_list,
+    eval_element_wise,
+    set_socket_shape,
+    is_socket_linked_to_list,
+    is_output_socket_a_list,
+    sync_node_list_sockets,
+    group_input_can_accept_list,
+    is_group_output_a_list,
+    sync_group_node_socket_shapes,
+)
+from NodeSlicer.core.slice import SlicePaths
+from NodeSlicer.infra.blender.blender_mesh_capture import SlicingObject, SlicingCollection, SlicingGroup
+from NodeSlicer.core.nodeslicer.tree import SLICETREE_NodeTree
+
+
+class TestListUtils(unittest.TestCase):
+    def test_is_list_data(self):
+        self.assertFalse(is_list_data(None))
+        self.assertFalse(is_list_data("a string"))
+        self.assertFalse(is_list_data(b"bytes"))
+        self.assertFalse(is_list_data(123))
+        self.assertFalse(is_list_data(12.34))
+        
+        # SlicePaths subclasses list, but represents an atomic toolpath set, NOT a list of toolpaths
+        sp = SlicePaths()
+        self.assertFalse(is_list_data(sp))
+        
+        # Normal lists and tuples
+        self.assertTrue(is_list_data([]))
+        self.assertTrue(is_list_data([1, 2, 3]))
+        self.assertTrue(is_list_data((1, 2)))
+        self.assertTrue(is_list_data([sp, sp]))
+
+    def test_flatten_list(self):
+        sp1 = SlicePaths()
+        sp2 = SlicePaths()
+        nested = [sp1, [sp2, None], [["gcode1"], "gcode2"]]
+        flattened = flatten_list(nested)
+        self.assertEqual(flattened, [sp1, sp2, "gcode1", "gcode2"])
+
+    def test_eval_element_wise(self):
+        def double(x):
+            return x * 2
+
+        self.assertEqual(eval_element_wise(double, 5), 10)
+        self.assertEqual(eval_element_wise(double, [1, 2, 3]), [2, 4, 6])
+
+
+class DummySocket:
+    def __init__(self, name="Socket", bl_idname="NodeSocketFloat", display_shape="CIRCLE"):
+        self.name = name
+        self.identifier = name
+        self.bl_idname = bl_idname
+        self.display_shape = display_shape
+        self.is_linked = False
+        self.links = []
+        self.node = None
+        self.value = None
+
+
+class DummyLink:
+    def __init__(self, from_socket, to_socket):
+        self.from_socket = from_socket
+        self.to_socket = to_socket
+
+
+class DummySocketCollection(list):
+    def get(self, name, default=None):
+        for s in self:
+            if getattr(s, "name", "") == name:
+                return s
+        return default
+
+class DummyNode:
+    def __init__(self, bl_idname="DummyNode"):
+        self.bl_idname = bl_idname
+        self.inputs = DummySocketCollection()
+        self.outputs = DummySocketCollection()
+        self.is_list_output = False
+
+    def add_in(self, sock):
+        sock.node = self
+        self.inputs.append(sock)
+
+    def add_out(self, sock):
+        sock.node = self
+        self.outputs.append(sock)
+
+
+class TestSocketShapesAndLinks(unittest.TestCase):
+    def test_socket_linked_to_list(self):
+        upstream_node = DummyNode("SLICENODE_MeshesToList")
+        upstream_node.is_list_output = True
+        out_sock = DummySocket("Meshes", "SLICESOCK_Mesh", display_shape="LIST")
+        upstream_node.add_out(out_sock)
+
+        downstream_node = DummyNode("SLICENODE_SliceShells")
+        in_sock = DummySocket("Mesh", "SLICESOCK_Mesh", display_shape="CIRCLE")
+        downstream_node.add_in(in_sock)
+
+        # Before linking
+        self.assertFalse(is_socket_linked_to_list(in_sock))
+        self.assertTrue(is_output_socket_a_list(out_sock))
+
+        # Link them
+        link = DummyLink(out_sock, in_sock)
+        in_sock.is_linked = True
+        in_sock.links = [link]
+
+        self.assertTrue(is_socket_linked_to_list(in_sock))
+
+    def test_sync_node_list_sockets(self):
+        upstream_node = DummyNode("SLICENODE_MeshesToList")
+        out_sock = DummySocket("Meshes", "SLICESOCK_Mesh", display_shape="LIST")
+        upstream_node.add_out(out_sock)
+
+        node = DummyNode("SLICENODE_SliceShells")
+        in_sock = DummySocket("Mesh", "SLICESOCK_Mesh", display_shape="CIRCLE")
+        out_path = DummySocket("Paths", "SLICESOCK_Paths", display_shape="CIRCLE")
+        node.add_in(in_sock)
+        node.add_out(out_path)
+
+        link = DummyLink(out_sock, in_sock)
+        in_sock.is_linked = True
+        in_sock.links = [link]
+
+        mapping = [("Mesh", "Paths")]
+        sync_node_list_sockets(node, mapping)
+
+        self.assertEqual(in_sock.display_shape, "LIST")
+        self.assertEqual(out_path.display_shape, "LIST")
+
+
+class TestTreeValidLinkRules(unittest.TestCase):
+    def setUp(self):
+        self.tree = SLICETREE_NodeTree()
+
+    def test_valid_link_start_print_rejects_list(self):
+        list_out = DummySocket("Gcode", "NodeSocketString", display_shape="LIST")
+        start_print = DummyNode("SLICENODE_StartPrint")
+        sp_in = DummySocket("Gcode", "NodeSocketString")
+        start_print.add_in(sp_in)
+
+        # Connection should be rejected
+        self.assertFalse(self.tree.valid_link(list_out, sp_in))
+
+        # Standard non-list connection should be allowed
+        normal_out = DummySocket("Gcode", "NodeSocketString", display_shape="CIRCLE")
+        self.assertTrue(self.tree.valid_link(normal_out, sp_in))
+
+    def test_valid_link_printer_list_rejects_list(self):
+        list_out = DummySocket("Gcode", "NodeSocketString", display_shape="LIST")
+        printer_list = DummyNode("SLICENODE_PrinterList")
+        pl_in = DummySocket("Printer1", "NodeSocketString")
+        printer_list.add_in(pl_in)
+
+        self.assertFalse(self.tree.valid_link(list_out, pl_in))
+
+    def test_valid_link_path_operations_secondary_inputs_reject_list(self):
+        list_out = DummySocket("Paths", "SLICESOCK_Paths", display_shape="LIST")
+        path_ops = DummyNode("SLICENODE_PathOperations")
+        p0 = DummySocket("Paths", "SLICESOCK_Paths")
+        p1 = DummySocket("Paths", "SLICESOCK_Paths")
+        path_ops.add_in(p0)
+        path_ops.add_in(p1)
+
+        # Primary input p0 accepts list
+        self.assertTrue(self.tree.valid_link(list_out, p0))
+        # Secondary input p1 rejects list
+        self.assertFalse(self.tree.valid_link(list_out, p1))
+
+    def test_valid_link_seam_placement_cutting_mesh_rejects_list(self):
+        list_mesh_out = DummySocket("Mesh", "SLICESOCK_Mesh", display_shape="LIST")
+        seam_node = DummyNode("SLICENODE_SeamPlacement")
+        p_in = DummySocket("Paths", "SLICESOCK_Paths")
+        m_in = DummySocket("Mesh", "SLICESOCK_Mesh")
+        seam_node.add_in(p_in)
+        seam_node.add_in(m_in)
+
+        # Secondary cutting mesh rejects list
+        self.assertFalse(self.tree.valid_link(list_mesh_out, m_in))
+
+
+class TestNodeEvaluationsWithLists(unittest.TestCase):
+    def test_path_operations_with_first_input_list(self):
+        from NodeSlicer.core.nodeslicer.nodes.path import SLICENODE_PathOperations
+
+        node = SLICENODE_PathOperations()
+        node.operation = 'EXTEND'
+
+        p1 = SlicePaths([np.array([[0, 0, 0], [1, 1, 0]], dtype=np.float64)])
+        p2 = SlicePaths([np.array([[2, 2, 0], [3, 3, 0]], dtype=np.float64)])
+        q = SlicePaths([np.array([[10, 10, 0], [11, 11, 0]], dtype=np.float64)])
+
+        # Mock inputs
+        inp0 = DummySocket("Paths", "SLICESOCK_Paths")
+        inp0.is_linked = True
+        inp1 = DummySocket("Paths", "SLICESOCK_Paths")
+        inp1.is_linked = True
+
+        node.inputs = [inp0, inp1]
+
+        # resolve input mocking
+        def mock_resolve_input(sock, **kwargs):
+            if sock is inp0:
+                return [p1, p2]  # List input
+            elif sock is inp1:
+                return q
+            return None
+
+        import NodeSlicer.infra.blender.blender_slice_nodes_generic as b_gen
+        original_resolve = b_gen.resolve_input
+        b_gen.resolve_input = mock_resolve_input
+        try:
+            res = node.evaluate_output("Paths")
+            self.assertIsInstance(res, list)
+            self.assertEqual(len(res), 2)
+            # res[0] is EXTEND of p1 and q
+            self.assertEqual(len(res[0]), 2)
+            # res[1] is EXTEND of p2 and q
+            self.assertEqual(len(res[1]), 2)
+        finally:
+            b_gen.resolve_input = original_resolve
+
+    def test_join_gcode_no_lists(self):
+        from NodeSlicer.core.nodeslicer.nodes.gcode import SLICENODE_JoinGcode
+
+        node = SLICENODE_JoinGcode()
+        node.resolve_multi_input = lambda label: ["G28", "G90", "M104 S200"]
+        res = node.evaluate_output("Gcode")
+        self.assertEqual(res, "G28\nG90\nM104 S200")
+
+    def test_join_gcode_one_list(self):
+        from NodeSlicer.core.nodeslicer.nodes.gcode import SLICENODE_JoinGcode
+
+        node = SLICENODE_JoinGcode()
+        node.resolve_multi_input = lambda label: ["START", ["LAYER1", "LAYER2", "LAYER3"], "END"]
+        res = node.evaluate_output("Gcode")
+        self.assertEqual(res, [
+            "START\nLAYER1\nEND",
+            "START\nLAYER2\nEND",
+            "START\nLAYER3\nEND",
+        ])
+
+    def test_join_gcode_multiple_lists_zipped(self):
+        from NodeSlicer.core.nodeslicer.nodes.gcode import SLICENODE_JoinGcode
+
+        node = SLICENODE_JoinGcode()
+        node.resolve_multi_input = lambda label: [
+            "INIT",
+            ["A1", "A2", "A3"],
+            "MID",
+            ["B1", "B2", "B3"],
+            "FINAL",
+        ]
+        res = node.evaluate_output("Gcode")
+        self.assertEqual(res, [
+            "INIT\nA1\nMID\nB1\nFINAL",
+            "INIT\nA2\nMID\nB2\nFINAL",
+            "INIT\nA3\nMID\nB3\nFINAL",
+        ])
+
+    def test_join_gcode_mismatched_lengths_raises_error(self):
+        from NodeSlicer.core.nodeslicer.nodes.gcode import SLICENODE_JoinGcode
+
+        node = SLICENODE_JoinGcode()
+        node.resolve_multi_input = lambda label: [["A1", "A2"], ["B1", "B2", "B3"]]
+        with self.assertRaises(ValueError):
+            node.evaluate_output("Gcode")
+
+    def test_join_gcode_socket_shape_updates(self):
+        from NodeSlicer.core.nodeslicer.nodes.gcode import SLICENODE_JoinGcode
+
+        node = SLICENODE_JoinGcode()
+        in0 = DummySocket("Gcode", "NodeSocketString", display_shape="CIRCLE")
+        out0 = DummySocket("Gcode", "NodeSocketString", display_shape="CIRCLE")
+        node.inputs = DummySocketCollection([in0])
+        node.outputs = DummySocketCollection([out0])
+
+        # Initially without list link
+        node.update()
+        self.assertEqual(out0.display_shape, "CIRCLE")
+
+        # Linked to list
+        upstream = DummyNode("SLICENODE_GcodesToList")
+        upstream.is_list_output = True
+        up_out = DummySocket("Gcode", "NodeSocketString", display_shape="LIST")
+        upstream.add_out(up_out)
+
+        link = DummyLink(up_out, in0)
+        in0.is_linked = True
+        in0.links = [link]
+
+        node.update()
+        self.assertEqual(out0.display_shape, "LIST")
+
+    def test_gcode_regex_replace_list(self):
+        from NodeSlicer.core.nodeslicer.nodes.gcode import SLICENODE_GcodeRegexReplace
+
+        node = SLICENODE_GcodeRegexReplace()
+        node.resolve = lambda field: {
+            "Gcode": ["G1 X10 Y10", "G1 X20 Y20"],
+            "Find": "G1",
+            "Replace": "G0"
+        }.get(field)
+
+        res = node.evaluate_output("Gcode")
+        self.assertEqual(res, ["G0 X10 Y10", "G0 X20 Y20"])
+
+    def test_list_joiners_evaluation(self):
+        from NodeSlicer.core.nodeslicer.nodes.inputs import SLICENODE_ObjectsToList
+        from NodeSlicer.core.nodeslicer.nodes.mesh import SLICENODE_MeshesToList
+        from NodeSlicer.core.nodeslicer.nodes.path import SLICENODE_PathsToList
+        from NodeSlicer.core.nodeslicer.nodes.gcode import SLICENODE_GcodesToList
+
+        # ObjectsToList
+        obj1 = DummyObject("Obj1")
+        obj2 = DummyObject("Obj2")
+        o_node = SLICENODE_ObjectsToList()
+        o_node.resolve_multi_input = lambda label: [[obj1], obj2]
+        self.assertEqual(o_node.evaluate_output("Objects"), [obj1, obj2])
+
+        # MeshesToList
+        sc1 = SlicingCollection([], "M1")
+        sc2 = SlicingCollection([], "M2")
+        m_node = SLICENODE_MeshesToList()
+        m_node.resolve_multi_input = lambda label: [sc1, [sc2]]
+        self.assertEqual(m_node.evaluate_output("Meshes"), [sc1, sc2])
+
+        # PathsToList
+        sp1 = SlicePaths([np.array([[0, 0, 0], [1, 1, 0]], dtype=np.float64)])
+        sp2 = SlicePaths([np.array([[2, 2, 0], [3, 3, 0]], dtype=np.float64)])
+        p_node = SLICENODE_PathsToList()
+        p_node.resolve_multi_input = lambda label: [sp1, [sp2]]
+        self.assertEqual(p_node.evaluate_output("Paths"), [sp1, sp2])
+
+        # GcodesToList
+        g_node = SLICENODE_GcodesToList()
+        g_node.resolve_multi_input = lambda label: [["G1 X1"], "G1 X2"]
+        self.assertEqual(g_node.evaluate_output("Gcode"), ["G1 X1", "G1 X2"])
+
+    def test_join_mesh_flattens_lists(self):
+        from NodeSlicer.core.nodeslicer.nodes.mesh import SLICENODE_JoinMesh
+
+        node = SLICENODE_JoinMesh()
+        so1 = SlicingObject()
+        so1.name = "part1"
+        so1.mesh = np.ones((1, 4, 3), dtype=np.float64)
+        sc1 = SlicingCollection([], "Coll1")
+        sc1.objects = [so1]
+
+        so2 = SlicingObject()
+        so2.name = "part2"
+        so2.mesh = np.ones((2, 4, 3), dtype=np.float64)
+        sc2 = SlicingCollection([], "Coll2")
+        sc2.objects = [so2]
+
+        so3 = SlicingObject()
+        so3.name = "part3"
+        so3.mesh = np.ones((3, 4, 3), dtype=np.float64)
+        sc3 = SlicingCollection([], "Coll3")
+        sc3.objects = [so3]
+
+        # Mock inputs delivering [ [sc1, sc2], sc3 ]
+        mock_in1 = DummySocket("Mesh", "SLICESOCK_Mesh")
+        mock_in1.is_linked = True
+        mock_in2 = DummySocket("Mesh", "SLICESOCK_Mesh")
+        mock_in2.is_linked = True
+        node.inputs = [mock_in1, mock_in2]
+
+        import NodeSlicer.infra.blender.blender_slice_nodes_generic as b_gen
+        original_resolve = b_gen.resolve_input
+        b_gen.resolve_input = lambda sock, **kw: [sc1, sc2] if sock is mock_in1 else sc3
+        try:
+            res = node.evaluate_output("Mesh")
+            self.assertIsInstance(res, SlicingCollection)
+            self.assertEqual(len(res.objects), 3)
+            self.assertEqual({o.name for o in res.objects}, {"part1", "part2", "part3"})
+        finally:
+            b_gen.resolve_input = original_resolve
+
+    def test_drop_geometry_list_evaluation(self):
+        from NodeSlicer.core.nodeslicer.nodes.mesh import SLICENODE_DropGeometry
+
+        node = SLICENODE_DropGeometry()
+        so1 = SlicingObject()
+        so1.name = "part1"
+        so1.mesh = np.array([[[0, 0, 5], [1, 0, 5], [0, 1, 5], [0, 0, 1]]], dtype=np.float64)
+        sc1 = SlicingCollection([], "M1")
+        sc1.objects = [so1]
+
+        so2 = SlicingObject()
+        so2.name = "part2"
+        so2.mesh = np.array([[[0, 0, 2], [1, 0, 2], [0, 1, 2], [0, 0, 1]]], dtype=np.float64)
+        sc2 = SlicingCollection([], "M2")
+        sc2.objects = [so2]
+
+        node.resolve = lambda field: [sc1, sc2] if field == "Mesh" else 0.0
+
+        res_mesh = node.evaluate_output("Mesh")
+        res_trans = node.evaluate_output("Translation")
+
+        self.assertIsInstance(res_mesh, list)
+        self.assertEqual(len(res_mesh), 2)
+        self.assertIsInstance(res_trans, list)
+        self.assertEqual(res_trans, [(0.0, 0.0, -5.0), (0.0, 0.0, -2.0)])
+
+    def test_start_print_rejects_list_in_evaluate(self):
+        from NodeSlicer.core.nodeslicer.nodes.output import SLICENODE_StartPrint
+
+        node = SLICENODE_StartPrint()
+        node.resolve = lambda field: ["G1 X0", "G1 X10"] if field == "Gcode" else None
+
+        op = MagicMock()
+        res = node.evaluate(operator=op)
+        self.assertEqual(res, 'error')
+        op.report.assert_called_with({'ERROR'}, "Start Print does not accept a list of Gcode")
+
+
+class DummyInterfaceItem:
+    def __init__(self, name, identifier, in_out="INPUT", socket_type="SLICESOCK_Paths"):
+        self.name = name
+        self.identifier = identifier
+        self.in_out = in_out
+        self.socket_type = socket_type
+        self.item_type = 'SOCKET'
+
+
+class DummyInterface:
+    def __init__(self, items):
+        self.items_tree = items
+
+
+class DummyGroupTree:
+    def __init__(self, items=None, nodes=None):
+        self.interface = DummyInterface(items or [])
+        self.nodes = nodes or []
+
+
+class DummyGroupNode(DummyNode):
+    def __init__(self, name="Group", tree=None):
+        super().__init__("SLICENODE_Group")
+        self.name = name
+        self.slicer_tree = tree
+
+
+class TestGroupNodeListShapes(unittest.TestCase):
+    def test_group_input_can_accept_list_detection(self):
+        item_paths = DummyInterfaceItem("Paths", "sock_paths", in_out="INPUT", socket_type="SLICESOCK_Paths")
+        item_float = DummyInterfaceItem("FloatVal", "sock_float", in_out="INPUT", socket_type="NodeSocketFloat")
+
+        gin = DummyNode("NodeGroupInput")
+        gin_out_paths = DummySocket("Paths", "SLICESOCK_Paths")
+        gin_out_paths.identifier = "sock_paths"
+        gin_out_float = DummySocket("FloatVal", "NodeSocketFloat")
+        gin_out_float.identifier = "sock_float"
+        gin.add_out(gin_out_paths)
+        gin.add_out(gin_out_float)
+
+        target_node = DummyNode("SLICENODE_BufferShells")
+        target_node.list_socket_mapping = [("Paths", "Paths")]
+        target_in_paths = DummySocket("Paths", "SLICESOCK_Paths")
+        target_node.add_in(target_in_paths)
+
+        link = DummyLink(gin_out_paths, target_in_paths)
+        gin_out_paths.is_linked = True
+        gin_out_paths.links = [link]
+
+        tree = DummyGroupTree([item_paths, item_float], [gin, target_node])
+
+        # Paths input can accept list because target is BufferShells
+        self.assertTrue(group_input_can_accept_list(tree, item_paths))
+        # FloatVal cannot accept list because socket type is Float
+        self.assertFalse(group_input_can_accept_list(tree, item_float))
+
+    def test_group_input_connected_to_forbidden_node_rejects_list(self):
+        item_gcode = DummyInterfaceItem("Gcode", "sock_gcode", in_out="INPUT", socket_type="NodeSocketString")
+
+        gin = DummyNode("NodeGroupInput")
+        gin_out_gcode = DummySocket("Gcode", "NodeSocketString")
+        gin_out_gcode.identifier = "sock_gcode"
+        gin.add_out(gin_out_gcode)
+
+        sp_node = DummyNode("SLICENODE_StartPrint")
+        sp_in = DummySocket("Gcode", "NodeSocketString")
+        sp_node.add_in(sp_in)
+
+        link = DummyLink(gin_out_gcode, sp_in)
+        gin_out_gcode.is_linked = True
+        gin_out_gcode.links = [link]
+
+        tree = DummyGroupTree([item_gcode], [gin, sp_node])
+
+        # StartPrint forbids lists, so group input must NOT accept list
+        self.assertFalse(group_input_can_accept_list(tree, item_gcode))
+
+    def test_group_output_inherent_list(self):
+        item_out = DummyInterfaceItem("Paths", "sock_out_paths", in_out="OUTPUT", socket_type="SLICESOCK_Paths")
+
+        gout = DummyNode("NodeGroupOutput")
+        gout_in = DummySocket("Paths", "SLICESOCK_Paths")
+        gout_in.identifier = "sock_out_paths"
+        gout.add_in(gout_in)
+
+        list_joiner = DummyNode("SLICENODE_PathsToList")
+        list_joiner.is_list_output = True
+        lj_out = DummySocket("Paths", "SLICESOCK_Paths", display_shape="LIST")
+        list_joiner.add_out(lj_out)
+
+        link = DummyLink(lj_out, gout_in)
+        gout_in.is_linked = True
+        gout_in.links = [link]
+
+        tree = DummyGroupTree([item_out], [gout, list_joiner])
+
+        # Output fed from PathsToList is always a list
+        self.assertTrue(is_group_output_a_list(None, tree, item_out))
+
+    def test_group_output_element_wise_propagation_and_sync(self):
+        item_in = DummyInterfaceItem("Paths", "sock_in", in_out="INPUT", socket_type="SLICESOCK_Paths")
+        item_out = DummyInterfaceItem("Paths", "sock_out", in_out="OUTPUT", socket_type="SLICESOCK_Paths")
+
+        gin = DummyNode("NodeGroupInput")
+        gin_out = DummySocket("Paths", "SLICESOCK_Paths")
+        gin_out.identifier = "sock_in"
+        gin.add_out(gin_out)
+
+        buf_node = DummyNode("SLICENODE_BufferShells")
+        buf_node.list_socket_mapping = [("Paths", "Paths")]
+        buf_in = DummySocket("Paths", "SLICESOCK_Paths")
+        buf_out = DummySocket("Paths", "SLICESOCK_Paths")
+        buf_node.add_in(buf_in)
+        buf_node.add_out(buf_out)
+
+        gout = DummyNode("NodeGroupOutput")
+        gout_in = DummySocket("Paths", "SLICESOCK_Paths")
+        gout_in.identifier = "sock_out"
+        gout.add_in(gout_in)
+
+        link1 = DummyLink(gin_out, buf_in)
+        gin_out.is_linked = True
+        gin_out.links = [link1]
+        buf_in.is_linked = True
+        buf_in.links = [link1]
+
+        link2 = DummyLink(buf_out, gout_in)
+        buf_out.is_linked = True
+        buf_out.links = [link2]
+        gout_in.is_linked = True
+        gout_in.links = [link2]
+
+        tree = DummyGroupTree([item_in, item_out], [gin, buf_node, gout])
+
+        grp_node = DummyGroupNode("MyGroup", tree)
+        grp_in = DummySocket("Paths", "SLICESOCK_Paths", display_shape="CIRCLE")
+        grp_in.identifier = "sock_in"
+        grp_out = DummySocket("Paths", "SLICESOCK_Paths", display_shape="CIRCLE")
+        grp_out.identifier = "sock_out"
+        grp_node.add_in(grp_in)
+        grp_node.add_out(grp_out)
+
+        # Before external link:
+        # Input should be LIST (because list input is possible)
+        # Output should be CIRCLE (because no list is fed)
+        sync_group_node_socket_shapes(grp_node)
+        self.assertEqual(grp_in.display_shape, "LIST")
+        self.assertEqual(grp_out.display_shape, "CIRCLE")
+
+        # Now link a list to the group's input externally:
+        up_node = DummyNode("SLICENODE_PathsToList")
+        up_node.is_list_output = True
+        up_out = DummySocket("Paths", "SLICESOCK_Paths", display_shape="LIST")
+        up_node.add_out(up_out)
+
+        ext_link = DummyLink(up_out, grp_in)
+        grp_in.is_linked = True
+        grp_in.links = [ext_link]
+
+        # After external list link:
+        # Output should now become LIST!
+        sync_group_node_socket_shapes(grp_node)
+        self.assertEqual(grp_in.display_shape, "LIST")
+        self.assertEqual(grp_out.display_shape, "LIST")
+
+    def test_valid_link_with_group_nodes(self):
+        item_paths = DummyInterfaceItem("Paths", "sock_paths", in_out="INPUT", socket_type="SLICESOCK_Paths")
+        item_float = DummyInterfaceItem("FloatVal", "sock_float", in_out="INPUT", socket_type="NodeSocketFloat")
+
+        gin = DummyNode("NodeGroupInput")
+        gin_out_paths = DummySocket("Paths", "SLICESOCK_Paths")
+        gin_out_paths.identifier = "sock_paths"
+        gin_out_float = DummySocket("FloatVal", "NodeSocketFloat")
+        gin_out_float.identifier = "sock_float"
+        gin.add_out(gin_out_paths)
+        gin.add_out(gin_out_float)
+
+        target_node = DummyNode("SLICENODE_BufferShells")
+        target_node.list_socket_mapping = [("Paths", "Paths")]
+        target_in_paths = DummySocket("Paths", "SLICESOCK_Paths")
+        target_node.add_in(target_in_paths)
+
+        link = DummyLink(gin_out_paths, target_in_paths)
+        gin_out_paths.is_linked = True
+        gin_out_paths.links = [link]
+
+        tree = DummyGroupTree([item_paths, item_float], [gin, target_node])
+
+        grp_node = DummyGroupNode("Group", tree)
+        grp_in_paths = DummySocket("Paths", "SLICESOCK_Paths")
+        grp_in_paths.identifier = "sock_paths"
+        grp_in_float = DummySocket("FloatVal", "NodeSocketFloat")
+        grp_in_float.identifier = "sock_float"
+        grp_node.add_in(grp_in_paths)
+        grp_node.add_in(grp_in_float)
+
+        list_out = DummySocket("Paths", "SLICESOCK_Paths", display_shape="LIST")
+        validator = SLICETREE_NodeTree()
+
+        # Linking list to Paths group input (which accepts list): allowed
+        self.assertTrue(validator.valid_link(list_out, grp_in_paths))
+
+        # Linking list to FloatVal group input: rejected
+        self.assertFalse(validator.valid_link(list_out, grp_in_float))
+
+
+if __name__ == '__main__':
+    unittest.main()