Worked on the openclaw/openclaw repository to address a critical bug affecting provider resolution for vendor-prefixed models. Focused on backend development and API integration using TypeScript and Markdown, the work involved refining error handling to ensure that the explicitly stored provider is always used when resolving session model references. This targeted fix eliminated incorrect API calls and potential billing errors, directly improving reliability and billing accuracy for customers. Comprehensive unit tests were added to verify the new logic and prevent regressions, resulting in a maintainable and robust solution that strengthens the foundation for future vendor-specific integrations within the codebase.