fix: preserve fragments when rewriting variant refs

preprocess_schemas.py

@@ -449,16 +449,21 @@ def rewrite_refs_to_variants(root, op, file_path, variant_needs):
     for node in iter_nodes(root):
         if isinstance(node, dict) and "$ref" in node:
             ref = node["$ref"]
-            if "#" not in ref:  # External file reference
-                abs_target = (file_path.parent / ref).resolve()
-                if (
-                    str(abs_target) in variant_needs
-                    and op in variant_needs[str(abs_target)]
-                ):
-                    ref_path = Path(ref)
-                    node["$ref"] = str(
-                        ref_path.parent / f"{ref_path.stem}_{op}_request.json"
-                    )
+            ref_file, separator, fragment = ref.partition("#")
+            if not ref_file:
+                continue
+            abs_target = (file_path.parent / ref_file).resolve()
+            if (
+                str(abs_target) in variant_needs
+                and op in variant_needs[str(abs_target)]
+            ):
+                ref_path = Path(ref_file)
+                variant_ref = str(
+                    ref_path.parent / f"{ref_path.stem}_{op}_request.json"
+                )
+                node["$ref"] = variant_ref + (
+                    separator + fragment if separator else ""
+                )
 
 
 def _apply_request_rules_to_object(

tests/test_codegen_pipeline.py

@@ -247,6 +247,33 @@ def test_eval_prop_inclusion_applies_operation_overrides(self) -> None:
 class VariantGenerationTest(unittest.TestCase):
     """Tests request variant construction and output."""
 
+    def test_rewrite_external_ref_preserves_fragment(self) -> None:
+        """External refs target variants without losing their fragments."""
+        schema = {
+            "properties": {
+                "child": {"$ref": "nested/child.json#/$defs/item"},
+                "local": {"$ref": "#/$defs/local"},
+            }
+        }
+        file_path = Path("/schemas/parent.json")
+        child_path = str((file_path.parent / "nested" / "child.json").resolve())
+
+        preprocess_schemas.rewrite_refs_to_variants(
+            schema,
+            "create",
+            file_path,
+            {child_path: {"create"}},
+        )
+
+        self.assertEqual(
+            schema["properties"]["child"]["$ref"],
+            "nested/child_create_request.json#/$defs/item",
+        )
+        self.assertEqual(
+            schema["properties"]["local"]["$ref"],
+            "#/$defs/local",
+        )
+
     def test_object_variant_filters_fields_and_rewrites_refs(self) -> None:
         """Object variants filter fields and target child variants."""
         schema = {