> For the complete documentation index, see [llms.txt](https://docs.yumi.finance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.yumi.finance/buy-now-pay-later/technical-architecture.md). # Technical architecture ### Using Yumi as a BNPL Option (Onboarding) * The entire flow takes place **within the merchant’s or PSP's UI**; integration is achieved via the SDK, which includes theming support. * The user can l**ink a bank account** (optional) to receive asset statements and transaction + identity data. In the US, this is done via Plaid; in other locations, we use zkTLS. * The user can also **connect** **EVM and/or SVM wallets**. * If a bank is not connected, the user must **complete a zkKYC**. * At least **one financial data source** (a wallet or a bank) is required. * We are currently working to integrate with other data sources to improve coverage. After onboarding, an initial **credit limit** is set based on financial data and **dynamically updated**. ### Payment * The merchant queries Yumi for a **decision (limit/approval)**; the SDK returns a **callback** with the current **credit limit, approval (or rejection),** and additional loan information. The user's limit may change from purchase to purchase and after repayments. * The **user sends 25%** of the purchase amount to the merchant, and **Yumi sends the other 75%**. ### Debt Repayment (Installments) **Every 2 weeks**, Yumi automatically pulls the **scheduled installment** directly from the user’s wallet using the provided allowance (onchain or offchain), until the debt is fully repaid (**3 pulls in total**). If the user’s wallet does not have sufficient balance at the scheduled time, repayment will fail, and the user may incur penalties or risk a lowered credit score.