Worked on improving error handling and validation workflows in the temporalio/sdk-python repository, focusing on backend development and robust testing. Addressed a bug where workflow failure exceptions were incorrectly wrapped in generic RuntimeError instances during argument decoding, which previously obscured the root cause of failures. Enhanced the system to ensure that validation errors, such as those from pydantic, are surfaced as workflow failures, making them more visible and actionable for users. Utilized Python and Jinja to implement these changes, adding targeted tests to verify correct behavior and improving the overall reliability and debuggability of workflow failure propagation within the SDK.