Worked on the zulip/zulip repository to enhance API reliability and maintain backward compatibility in the message sending workflow. Focused on updating and expanding tests for the Message Sending API, specifically ensuring the 'to' parameter is correctly JSON encoded as required by OpenAPI documentation, while also validating support for legacy raw string formats. Used Python for backend development and API testing, implementing changes that reduced the risk of spec drift and improved integration reliability for external clients. The approach prioritized robust unit testing and careful documentation, resulting in clearer API contracts and smoother onboarding for bots and legacy client integrations.