> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt. ## 4.22.1-rc0 **`(feat):`** Lazily validate model serialization to reduce memory consumption. Pydantic 2.11.0 introduced an issue where the model\_serializer decorator set to wrap mode forced it to eagerly do schema validation at import time. Because we had this decorator on the UniversalBaseModel, it would try to validate the schemas of all the Model types at import time. This caused massive memory spikes for more complex SDKs, up to 2.6GB in some cases. This change essentially accomplishes the same logic of wrapping the serialization process and modifying the serialization structure of datetime fields. The difference is that we manually wrap, so we're able to defer model validation until runtime, drastically reducing our memory consumption.