diff --git a/src/lfx/src/lfx/interface/listing.py b/src/lfx/src/lfx/interface/listing.py
index e051e34c4e..c96bcc519a 100644
--- a/src/lfx/src/lfx/interface/listing.py
+++ b/src/lfx/src/lfx/interface/listing.py
@@ -17,10 +17,14 @@ class AllTypesDict(LazyLoadDictBase):
 
     @override
     def get_type_dict(self):
-        from lfx.custom.utils import get_all_types_dict
+        # Must stay synchronous: this is reached from the sync `all_types_dict` property during
+        # graph build (vertex base_type fallback). Use the sync builder, not the async
+        # `get_all_types_dict` (returning its un-awaited coroutine raised
+        # "'coroutine' object is not a mapping").
+        from lfx.custom.utils import build_custom_components
 
         settings_service = get_settings_service()
-        return get_all_types_dict(settings_service.settings.components_path)
+        return build_custom_components(settings_service.settings.components_path)
 
 
 lazy_load_dict = AllTypesDict()
diff --git a/src/lfx/tests/unit/interface/test_listing.py b/src/lfx/tests/unit/interface/test_listing.py
new file mode 100644
index 0000000000..478ae887d1
--- /dev/null
+++ b/src/lfx/tests/unit/interface/test_listing.py
@@ -0,0 +1,20 @@
+"""Tests for lfx.interface.listing — the synchronous all-types lookup."""
+
+from __future__ import annotations
+
+
+def test_all_types_dict_is_a_mapping_not_a_coroutine():
+    """`all_types_dict` must return a real mapping synchronously.
+
+    Regression: `get_type_dict` called the async `get_all_types_dict` without awaiting it,
+    so the sync `_build_dict` did `{**coroutine}` and raised
+    "'coroutine' object is not a mapping". This path is reached during graph build (a vertex
+    falling back to look up its base_type), so every flow that hit it failed to load.
+    """
+    from lfx.interface.listing import AllTypesDict
+
+    result = AllTypesDict().all_types_dict
+
+    assert isinstance(result, dict)
+    # The sync builder discovers the bundled component categories plus the "Custom" entry.
+    assert "Custom" in result