> For the complete documentation index, see [llms.txt](https://docs.fira.money/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fira.money/developers/protocol-contracts/router/action-borrow.md).

# ActionBorrow

ActionBorrow integrates with the lending market for fixed-rate borrowing and repayment in a single transaction.

{% hint style="info" %}
**Source:** `src/fira_bonding/router/ActionBorrow.sol`
{% endhint %}

## Functions

### `supplyAndBorrowSingleToken`

Supply collateral → borrow BT → swap BT to FW → redeem FW to desired token. All in one transaction.

### `borrowSingleToken`

Same flow but assumes collateral is already supplied.

### `repay`

Converts input token to BT and repays the lending market:

* **Pre-expiry:** Input token → FW (mint) → BT (AMM swap) → repay. Refunds excess BT.
* **Post-expiry:** Input token → FW (mint) → BT+CT (via `CT.mintBC`) → repay with BT. CT is minted but has zero value post-expiry.

## Key details

* The borrow position is owned by `msg.sender`, but the router is the token receiver — BT is held transiently and swapped immediately.
* `tokensToRepay` must be ≤ current debt, otherwise reverts with `"AB: repay too much"`.
* Requires the user to have authorized the router on the LendingMarket (`setAuthorization(router, true)`).


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