Worked on the medusajs/medusa repository to deliver a tax line data model enhancement supporting jurisdiction breakdown data from custom tax providers. Built end-to-end data flow for provider payloads through cart and order tax line processes, using TypeScript and Node.js to implement new data and metadata fields in tax line models. Developed and executed comprehensive integration and HTTP tests to ensure accurate persistence and retrieval of provider data, with database migrations supporting the new schema. Provided practical integration guidance and examples, enabling richer invoice and order confirmations and improving tax reporting accuracy across providers such as Stripe Tax and TaxJar.