diff --git a/extra/gen_schema.py b/extra/gen_schema.py
index d83172f7..53aa7d17 100644
--- a/extra/gen_schema.py
+++ b/extra/gen_schema.py
@@ -11,29 +11,43 @@
 
 os.environ["BUMPS_USE_PYDANTIC"] = "True"
 
-from pydantic.schema import get_model, schema as make_schema
-from bumps.parameter import Expression, Parameter  # , UnaryExpression
+from pydantic.json_schema import GenerateJsonSchema, JsonSchemaValue
+from pydantic_core import PydanticOmit, core_schema
+from pydantic import BaseModel
+from pydantic.json_schema import GenerateJsonSchema, JsonSchemaValue
+from pydantic import TypeAdapter
+
+
+class CustomsGenerateJsonSchema(GenerateJsonSchema):
+    def handle_invalid_for_json_schema(self, schema: core_schema.CoreSchema, error_info: str) -> JsonSchemaValue:
+        print(f"Handling invalid schema: {error_info}")
+        raise PydanticOmit
+
+    def generate(self, schema: core_schema.CoreSchema, mode: str = "validation") -> JsonSchemaValue:
+        json_schema = super().generate(schema, mode=mode)
+        # Filter out properties starting with underscore
+        filtered_properties = {k: v for k, v in json_schema.get("properties", {}).items() if not k.startswith("_")}
+        json_schema["properties"] = filtered_properties
+        filtered_requires = [k for k in json_schema.get("required", []) if not k.startswith("_")]
+        json_schema["required"] = filtered_requires
+        return json_schema
 
-from refl1d.names import FitProblem, Repeat, Stack
+    def handle_property(self, property_name: str, property_value: JsonSchemaValue):
+        if property_name.startswith("_"):
+            return JsonSchemaValue(None)
+        return super().handle_property(property_name, property_value)
+
+
+from bumps.parameter import Expression, Parameter  # , UnaryExpression
 
-base_model = get_model(FitProblem)
+from refl1d.bumps_interface.fitproblem import FitProblem
 
-# resolve circular dependencies and self-references
-# TODO: this will be unnecessary in python 3.7+ with
-#     'from __future__ import annotations'
-# and in python 4.0+ presumably that can be removed as well.
-to_resolve = [
-    Expression,
-    Parameter,  # UnaryExpression
-    Repeat,
-    Stack,
-]
-for module in to_resolve:
-    get_model(module).update_forward_refs()
+ta = TypeAdapter(FitProblem)
+ta.rebuild()
 
 schema = {"$schema": "https://json-schema.org/draft-07/schema#", "$id": "refl1d-draft-01"}
 # schema.update(get_model(FitProblem).schema())
-schema.update(FitProblem.schema())
+schema.update(ta.json_schema(schema_generator=CustomsGenerateJsonSchema))
 
 
 def remove_default_typename(schema):
@@ -71,4 +85,5 @@ def convert_inf(obj):
 remove_proptitles(schema)
 schema = convert_inf(schema)
 
+os.makedirs("schema", exist_ok=True)
 open("schema/refl1d.schema.json", "w").write(json.dumps(schema, allow_nan=False, indent=2))
diff --git a/refl1d/names.py b/refl1d/names.py
index c485926a..a26b3d90 100644
--- a/refl1d/names.py
+++ b/refl1d/names.py
@@ -38,7 +38,7 @@
 )
 from .sample.cheby import ChebyVF, FreeformCheby, cheby_approx, cheby_points
 from .sample.flayer import FunctionalMagnetism, FunctionalProfile
-from .sample.layers import Slab, Stack
+from .sample.layers import Slab, Stack, Repeat, Layer
 from .sample.magnetism import FreeMagnetism, Magnetism, MagnetismStack, MagnetismTwist
 from .sample.material import SLD, Compound, Material, Mixture