From 166ddb479917d14abc8ab6f4de18ac441044c35a Mon Sep 17 00:00:00 2001
From: Andrej730 <azhilenkov@gmail.com>
Date: Thu, 13 Nov 2025 18:47:30 +0500
Subject: [PATCH] Fix parametric stair editing after 3617d11 #7355

---
 src/bonsai/bonsai/bim/module/model/prop.py | 9 +++++++--
 src/bonsai/bonsai/tool/model.py            | 5 +++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/bonsai/bonsai/bim/module/model/prop.py b/src/bonsai/bonsai/bim/module/model/prop.py
index bea28085d5..fd5397fe36 100644
--- a/src/bonsai/bonsai/bim/module/model/prop.py
+++ b/src/bonsai/bonsai/bim/module/model/prop.py
@@ -628,14 +628,19 @@ class BIMStairProperties(PropertyGroup):
 
     def set_props_kwargs_from_ifc_data(self, kwargs):
         kwargs = tool.Model.convert_data_to_si_units(kwargs, self.non_si_units_props)
+        tread_run = kwargs.get("tread_run", 0.3)
 
         # Determine lock state based on whether custom treads match tread_run
         # If custom_tread_lock wasn't saved (old files), infer it from the data
         if "custom_tread_lock" not in kwargs:
             custom_treads = kwargs.get("custom_first_last_tread_run", (0.0, 0.0))
-            tread_run = kwargs.get("tread_run", 0.3)
             # Lock is off if either custom tread differs from tread_run and is not 0
-            kwargs["custom_tread_lock"] = not any(ct != 0.0 and ct != tread_run for ct in custom_treads)
+            kwargs["custom_tread_lock"] = all(ct not in (0.0, tread_run) for ct in custom_treads)
+
+        if "custom_first_last_tread_run" in kwargs:
+            custom_treads = kwargs["custom_first_last_tread_run"]
+            custom_treads = [tread_run if v is None else v for v in custom_treads]
+            kwargs["custom_first_last_tread_run"] = custom_treads
 
         for prop_name in kwargs:
             setattr(self, prop_name, kwargs[prop_name])
diff --git a/src/bonsai/bonsai/tool/model.py b/src/bonsai/bonsai/tool/model.py
index e4685c54f4..0627b400ed 100644
--- a/src/bonsai/bonsai/tool/model.py
+++ b/src/bonsai/bonsai/tool/model.py
@@ -142,9 +142,10 @@ class Model(bonsai.core.tool.Model):
         for prop_name in data:
             if prop_name in non_si_props:
                 continue
-            prop_value = data[prop_name]
+            # `None` is used by `custom_first_last_tread_run`.
+            prop_value: Iterable[float | None] | float = data[prop_name]
             if isinstance(prop_value, collections.abc.Iterable):
-                data[prop_name] = [v * si_conversion for v in prop_value]
+                data[prop_name] = [v if v is None else v * si_conversion for v in prop_value]
             else:
                 data[prop_name] = prop_value * si_conversion
         return data