Repaying UNIT

In a two-transaction process, the user returns some of their borrowed UNIT stablecoins to their vault. This reduction in debt lowers the Bitcoin price at which liquidation would be triggered, moving it further from the current price and giving the user a greater margin of safety.

The user initiates a transaction to repay their borrowed UNIT runes, sending them back to their vault UTXO as part of the transaction. The MPC network verifies the repayment amount and processes the return of UNIT runes. The transaction builder then constructs a PSBT that reduces the vault’s borrowed amount while maintaining the same BTC collateral. The output reflects the reduced debt and unchanged collateral in an updated vault UTXO.

In a second transaction, the new vault state is processed, paying the network fees for both transactions to ensure atomic execution. This generates an updated vault token reflecting the reduced borrowed amount and improved collateralisation ratio. The vault UTXO retains both the user update path and the guardian/oracle liquidation path, with the improved ratio reducing the likelihood of liquidation. An OP_RETURN output records the updated vault state, including the reduced borrowed amount and revised collateralisation ratio.

Together with the Open Vault function, these processes form a complete vault management system, allowing users to borrow against, repay, and maintain their BTC-collateralised positions while ensuring proper record-keeping and risk controls throughout.

Repaying UNIT Transaction Diagram