@@ -210,6 +210,29 @@ def read_file_if_exists(path: str) -> str:
         return f.read()
 
 
+def remove_generated_schema_section(
+    schema: dict, def_key: str = "$defs", gen_def_key: str = "generated"
+) -> dict:
+    """Removes the generated section and the allOf entry that points to it.
+
+    aggregate_generated_schemas() merges into an existing generated section and
+    merge_deep() concatenates arrays, so a stale 'required' entry or 'type' would
+    survive every regeneration. Mirrors osl.util.postProcessPage in PageBot.js of
+    mediawiki-extensions-OpenSemanticLab. Modifies schema in place.
+    """
+    gen_def_pointer = f"#/{def_key}/{gen_def_key}"
+    defs = schema.get(def_key)
+    if isinstance(defs, dict):
+        defs.pop(gen_def_key, None)
+    if isinstance(schema.get("allOf"), list):
+        schema["allOf"] = [
+            entry
+            for entry in schema["allOf"]
+            if not (isinstance(entry, dict) and entry.get("$ref") == gen_def_pointer)
+        ]
+    return schema
+
+
 # Reusable type definitions
 class OverwriteOptions(Enum):
     """Options for overwriting properties"""
@@ -2084,9 +2107,17 @@ def store_entity_(
                 if characteristic_types and isinstance(entity_, characteristic_types):
                     mode = AggregateGeneratedSchemasParamMode.DEFINITIONS_SECTION
 
+                stored_schema = page.get_slot_content("jsonschema") or {}
+                # Regenerate the generated section from scratch. Skip this when
+                # the generation failed, so the stored section is kept.
+                if (
+                    mode == AggregateGeneratedSchemasParamMode.DEFINITIONS_SECTION
+                    and len(generated_schemas) > 0
+                ):
+                    remove_generated_schema_section(stored_schema)
                 new_schema = aggregate_generated_schemas(
                     AggregateGeneratedSchemasParam(
-                        schema=page.get_slot_content("jsonschema"),
+                        target_schema=stored_schema,
                         generated_schemas=generated_schemas,
                         mode=mode,
                     )
 
@@ -0,0 +1,182 @@
+"""Unit tests for the jsonschema slot regeneration in store_entity().
+
+Regression guard for two defects in the schema aggregation of store_entity():
+
+1. store_entity() passed the stored schema as `schema=`, a field that
+   AggregateGeneratedSchemasParam does not have. Pydantic ignored it, so the
+   aggregation always started from `{}` and every save dropped the hand-written
+   part of the jsonschema slot.
+2. In DEFINITIONS_SECTION mode the new generated schema was merged into the
+   existing `$defs/generated` instead of replacing it, so a `required` entry or a
+   `type` from an earlier save survived every regeneration.
+
+These run fully offline: store_entity() runs with offline=True, the meta category
+is served by a fake site and the overwrite policy is wrapped to put a stored
+jsonschema slot on the page, so no network is required.
+"""
+
+import json
+
+import pytest
+from opensemantic.core.v1 import CharacteristicType
+
+import osw.model.entity as model
+from osw.core import OSW
+from osw.wtsite import WtPage
+
+META_CATEGORY = "Category:OSWMetaCategory"
+GEN_POINTER = "#/$defs/generated"
+
+
+class _FakeMetaCategoryPage:
+    def __init__(self, title, template):
+        self.title = title
+        self._slots = {"schema_template": template, "jsondata": {}}
+
+    def get_slot_content(self, slot_key):
+        return self._slots[slot_key]
+
+
+class _FakeGetPageResult:
+    def __init__(self, pages):
+        self.pages = pages
+
+
+class _FakeSite:
+    def __init__(self, template):
+        self.template = template
+
+    def get_page(self, param):
+        return _FakeGetPageResult([
+            _FakeMetaCategoryPage(t, self.template) for t in param.titles
+        ])
+
+
+@pytest.fixture
+def store(monkeypatch):
+    """Runs store_entity() offline on a page whose jsonschema slot holds `stored`.
+
+    Returns the jsonschema slot that store_entity() wrote.
+    """
+    original_policy = OSW._apply_overwrite_policy
+
+    def _store(entity, template, stored):
+        def policy_with_stored_schema(param):
+            if stored is not None:
+                param.page.set_slot_content(
+                    "jsonschema", json.loads(json.dumps(stored))
+                )
+            return original_policy(param)
+
+        monkeypatch.setattr(
+            OSW, "_apply_overwrite_policy", staticmethod(policy_with_stored_schema)
+        )
+        osw_obj = OSW.construct(site=_FakeSite(template))
+        result = osw_obj.store_entity(
+            OSW.StoreEntityParam(
+                entities=[entity],
+                namespace="Category",
+                meta_category_title=META_CATEGORY,
+                offline=True,
+            )
+        )
+        (page,) = result.pages.values()
+        assert isinstance(page, WtPage)
+        return page.get_slot_content("jsonschema")
+
+    return _store
+
+
+def _characteristic():
+    return CharacteristicType(
+        uuid="efad8086-4a76-47ca-b278-f5f944e5754b",
+        name="TestCharacteristic",
+        label=[{"text": "Test Characteristic"}],
+        # the default resolves a superclass from a wiki
+        subclass_of=[],
+    )
+
+
+def _category():
+    # store_entity() selects ROOT_LEVEL mode for any entity that is not a
+    # characteristic, so a plain Item stored in the Category namespace suffices
+    return model.Item(
+        uuid="0d0c1c35-4c4d-4e3a-9c9a-6f4a1b2c3d4e",
+        name="TestCategory",
+        label=[model.Label(text="Test Category")],
+    )
+
+
+def test_root_level_keeps_hand_written_schema(store):
+    stored = {"title": "hand", "properties": {"manual": {"type": "string"}}}
+    template = '{"title": "{{name}}", "properties": {"gen": {"type": "number"}}}'
+
+    schema = store(_category(), template, stored)
+
+    assert schema["properties"]["manual"] == {"type": "string"}
+    assert schema["properties"]["gen"] == {"type": "number"}
+    assert schema["title"] == "TestCategory"
+
+
+def test_definitions_section_keeps_hand_written_schema(store):
+    stored = {"title": "hand", "$defs": {"manual": {"type": "string"}}}
+    template = '{"title": "{{name}}", "type": "object"}'
+
+    schema = store(_characteristic(), template, stored)
+
+    assert schema["$defs"]["manual"] == {"type": "string"}
+    assert schema["$defs"]["generated"]["type"] == "object"
+    assert schema["allOf"] == [{"$ref": GEN_POINTER}]
+
+
+def test_definitions_section_replaces_stale_generated_section(store):
+    stored = {"title": "hand", "$defs": {"manual": {"type": "string"}}}
+    first_template = (
+        '{"title": "{{name}}", "type": "object", "required": ["type"],'
+        ' "properties": {"type": {"type": "string"}}}'
+    )
+    second_template = (
+        '{"title": "{{name}}", "properties": {"value": {"type": "number"}}}'
+    )
+
+    first = store(_characteristic(), first_template, stored)
+    assert first["$defs"]["generated"]["required"] == ["type"]
+
+    second = store(_characteristic(), second_template, first)
+
+    generated = second["$defs"]["generated"]
+    assert "required" not in generated
+    assert "type" not in generated
+    assert "type" not in generated["properties"]
+    assert generated["properties"]["value"] == {"type": "number"}
+    assert generated["$comment"].count(META_CATEGORY) == 1
+    assert second["allOf"] == [{"$ref": GEN_POINTER}]
+    assert second["$defs"]["manual"] == {"type": "string"}
+
+
+def test_failed_generation_keeps_generated_section(store):
+    stored = {
+        "title": "hand",
+        "allOf": [{"$ref": GEN_POINTER}],
+        "$defs": {"generated": {"type": "object", "required": ["type"]}},
+    }
+    # not valid JSON, so generation fails and produces no generated schema
+    template = '{"title": {{name}}'
+
+    schema = store(_characteristic(), template, stored)
+
+    assert schema == stored
+
+
+def test_root_level_second_save_does_not_duplicate(store):
+    stored = {"title": "hand", "properties": {"manual": {"type": "string"}}}
+    template = (
+        '{"title": "{{name}}", "required": ["gen"],'
+        ' "properties": {"gen": {"type": "number"}}}'
+    )
+
+    first = store(_category(), template, stored)
+    second = store(_category(), template, first)
+
+    assert second == first
+    assert second["required"] == ["gen"]