> For the complete documentation index, see [llms.txt](https://docs.ducatprotocol.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.ducatprotocol.com/how-ducat-works/vaults/borrow-unit.md).
# Borrow UNIT
In a joint, concurrent two-transaction process, the user borrows additional UNIT stablecoins against their existing Bitcoin collateral. This increase in debt raises the Bitcoin price at which liquidation would be triggered.
The user initiates a transaction using their existing vault UTXO, requesting to borrow additional UNIT runes against their BTC collateral. The MPC network verifies the vault’s current collateralisation ratio and the requested borrow amount to ensure it maintains the required safety margin. The transaction builder then constructs a PSBT that updates the vault’s borrowed amount while keeping the BTC collateral locked. The outputs include the user receiving additional UNIT runes and an updated vault UTXO reflecting the new borrowed amount.
In a second transaction, the updated vault state is processed, paying the network fees for both transactions to ensure atomic execution. This generates an updated vault token that records the new borrowed amount and collateralisation ratio. As with the original vault, the UTXO maintains both the user update path and the guardian/oracle liquidation path.
An OP\_RETURN output records the updated vault state, including the new borrowed amount and revised collateralisation ratio.
Borrow UNIT Transaction Diagram
---
# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.
## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:
```
GET https://docs.ducatprotocol.com/how-ducat-works/vaults/borrow-unit.md?ask=&goal=
```
`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.