fix: handle additionalProperties: None edge case

Author: habema

src/agents/strict_schema.py

@@ -51,6 +51,8 @@ def _ensure_strict_json_schema(
     typ = json_schema.get("type")
     if typ == "object" and "additionalProperties" not in json_schema:
         json_schema["additionalProperties"] = False
+    elif typ == "object" and json_schema.get("additionalProperties") is None:
+        json_schema["additionalProperties"] = False
     elif (
         typ == "object"
         and "additionalProperties" in json_schema

tests/test_strict_schema.py

@@ -156,3 +156,20 @@ def test_null_values_removal():
     assert "maximum" not in param_schema
     assert "items" not in param_schema
     assert "properties" not in param_schema
+
+
+def test_additional_properties_none_handling():
+    """
+    Test that additionalProperties: None is properly converted to False to maintain strictness.
+    """
+    schema_with_none_additional_properties = {
+        "type": "object",
+        "properties": {"param": {"type": "string"}},
+        "additionalProperties": None,
+    }
+
+    result = ensure_strict_json_schema(schema_with_none_additional_properties)
+
+    # additionalProperties should be False, not removed
+    assert result["additionalProperties"] is False
+    assert "additionalProperties" in result