UPDATE

location_data/block_subdivision.py

@@ -32,7 +32,7 @@ def create_or_get_block_subdivision(
     اگر subdivision این بلوک قبلاً ساخته شده باشد همان را برمی‌گرداند؛
     در غیر این صورت الگوریتم grid + KMeans را اجرا و ذخیره می‌کند.
     """
-    from .models import BlockSubdivision
+    from .models import BlockSubdivision, build_default_sub_block, ensure_block_layout_defaults
 
     existing = BlockSubdivision.objects.filter(
         soil_location=location,
@@ -244,7 +244,7 @@ def render_elbow_plot(
 
 
 def sync_block_layout_with_subdivision(location, subdivision) -> None:
-    layout = location.block_layout or {}
+    layout = ensure_block_layout_defaults(location.block_layout, block_count=location.input_block_count)
     blocks = list(layout.get("blocks") or [])
     target_block = None
     for block in blocks:
@@ -263,7 +263,12 @@ def sync_block_layout_with_subdivision(location, subdivision) -> None:
         blocks.append(target_block)
 
     target_block["needs_subdivision"] = subdivision.centroid_count > 1
-    target_block["sub_blocks"] = list(subdivision.centroid_points or [])
+    target_block["sub_blocks"] = list(subdivision.centroid_points or []) or [
+        build_default_sub_block(
+            str(target_block.get("block_code") or "block-1"),
+            boundary=target_block.get("boundary") or {},
+        )
+    ]
     target_block["subdivision_summary"] = {
         "chunk_size_sqm": subdivision.chunk_size_sqm,
         "grid_point_count": subdivision.grid_point_count,