Worked on the medusajs/medusa repository to deliver a critical fix for shipping price calculations, addressing the association of cart items with their correct shipping profiles and locations. Introduced item-scoping logic in TypeScript and Node.js to ensure each shipping option processes only relevant items, preventing over-counting across multi-location scenarios. Expanded integration testing to cover complex cases involving multiple shipping profiles and fulfillment locations, validating endpoint behavior and supporting accurate per-profile pricing. Collaborated closely with co-authors to strengthen code reliability and maintainability, enhancing the test suite and ensuring robust production adoption. Focused on API development and full stack integration testing.