LendController

The LendController is the primary user-facing contract for each lending market. Borrowers interact with it to create loans, manage collateral, borrow more, repay, and get liquidated. It wraps the core controller.vy module — which contains all shared loan logic — and extends it with lending-specific features: borrow caps, vault token transfers, and available balance tracking.

Each lending market gets its own LendController instance, deployed by the LendFactory.

LendController.vy

The source code for the LendController.vy contract can be found on GitHub. The core module is controller.vy. The contract is written in Vyper version 0.4.3.

Deployment addresses will be added once contracts are finalized.

info

The LendController exports most of its functions from the controller.vy module. Functions documented below include both module-exported functions and lending-specific extensions. The module pattern means the core loan logic is shared with MintController (used for crvUSD mint markets).

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Loan Management

create_loan

LendController.create_loan(_collateral: uint256, _debt: uint256, _N: uint256)

Creates a new loan by depositing collateral and borrowing tokens. The collateral is distributed across _N bands in the AMM.

Input	Type	Description
_collateral	uint256	Amount of collateral to deposit
_debt	uint256	Amount of borrowed tokens to receive
_N	uint256	Number of bands to distribute collateral across (4–50)

Emits: Borrow event.

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borrow_more

LendController.borrow_more(_d_collateral: uint256, _d_debt: uint256)

Adds additional collateral and/or borrows more tokens against an existing loan.

Input	Type	Description
_d_collateral	uint256	Additional collateral to deposit (can be 0)
_d_debt	uint256	Additional debt to take on (can be 0)

Emits: Borrow event.

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add_collateral

LendController.add_collateral(_d_collateral: uint256, _for: address)

Adds collateral to an existing loan without borrowing more. Can be called by anyone on behalf of a borrower.

Input	Type	Description
_d_collateral	uint256	Amount of collateral to add
_for	address	Address of the borrower to add collateral for

Emits: Borrow event.

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remove_collateral

LendController.remove_collateral(_d_collateral: uint256)

Removes collateral from an existing loan. Reverts if the resulting health would be too low.

Input	Type	Description
_d_collateral	uint256	Amount of collateral to remove

Emits: RemoveCollateral event.

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repay

LendController.repay(_d_debt: uint256, _for: address)

Repays debt for a loan. If _d_debt exceeds the current debt, only the outstanding debt is repaid. Can be called by anyone on behalf of a borrower.

Input	Type	Description
_d_debt	uint256	Amount of debt to repay (use max_value(uint256) to repay all)
_for	address	Address of the borrower to repay for

Emits: Repay event.

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liquidate

LendController.liquidate(_user: address, _min_x: uint256)

Liquidates an unhealthy loan (health < 0). The caller repays the debt and receives the remaining collateral. Supports partial liquidation if the position is partially in soft liquidation.

Input	Type	Description
_user	address	Address of the borrower to liquidate
_min_x	uint256	Minimum amount of collateral to receive (slippage protection)

Emits: Liquidate event.

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---

Loan Info

debt

LendController.debt(_user: address) -> uint256: view

Returns the current debt of a user, including accrued interest.

Input	Type	Description
_user	address	Borrower address

Returns: current debt (uint256).

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health

LendController.health(_user: address, _full: bool) -> int256: view

Returns the health of a user's loan. Health > 0 means the loan is safe; health < 0 means it can be liquidated. If _full is true, returns health assuming the worst-case scenario where all collateral has been soft-liquidated.

Input	Type	Description
_user	address	Borrower address
_full	bool	If true, use full (pessimistic) health calculation

Returns: health value (int256).

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loan_exists

LendController.loan_exists(_user: address) -> bool: view

Returns whether a loan exists for the given user.

Input	Type	Description
_user	address	Borrower address

Returns: whether the loan exists (bool).

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user_state

LendController.user_state(_user: address) -> uint256[4]: view

Returns the full state of a user's loan: [collateral, stablecoin, debt, N].

Input	Type	Description
_user	address	Borrower address

Returns: [collateral, stablecoin, debt, N] (uint256[4]).

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user_prices

LendController.user_prices(_user: address) -> uint256[2]: view

Returns the upper and lower price bounds of a user's collateral bands in the AMM.

Input	Type	Description
_user	address	Borrower address

Returns: [price_upper, price_lower] (uint256[2]).

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users_to_liquidate

LendController.users_to_liquidate(_from: uint256, _limit: uint256) -> IController.Position[]: view

Returns a list of user positions that can be liquidated, paginated.

Input	Type	Description
_from	uint256	Starting index
_limit	uint256	Maximum number of positions to return

Returns: array of liquidatable positions (IController.Position[]).

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tokens_to_liquidate

LendController.tokens_to_liquidate(_user: address) -> uint256: view

Returns the amount of borrowed tokens needed to fully liquidate a user's position.

Input	Type	Description
_user	address	Borrower address

Returns: tokens needed for liquidation (uint256).

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total_debt

LendController.total_debt() -> uint256: view

Returns the total outstanding debt across all loans in this market, including accrued interest.

Returns: total debt (uint256).

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n_loans

LendController.n_loans() -> uint256: view

Returns the total number of active loans.

Returns: number of loans (uint256).

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loans

LendController.loans(_index: uint256) -> address: view

Returns the borrower address at a given loan index.

Input	Type	Description
_index	uint256	Loan index

Returns: borrower address (address).

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loan_ix

LendController.loan_ix(_user: address) -> uint256: view

Returns the index of a user's loan in the loans array.

Input	Type	Description
_user	address	Borrower address

Returns: loan index (uint256).

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---

Health Previews

These functions allow UIs to show the health impact of operations before the user submits a transaction.

create_loan_health_preview

LendController.create_loan_health_preview(_user: address, _collateral: uint256, _debt: uint256, _N: uint256, _full: bool) -> int256: view

Previews the health of a loan that would result from calling create_loan.

Input	Type	Description
_user	address	Borrower address
_collateral	uint256	Collateral amount
_debt	uint256	Debt amount
_N	uint256	Number of bands
_full	bool	Full (pessimistic) health

Returns: predicted health (int256).

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borrow_more_health_preview

LendController.borrow_more_health_preview(_user: address, _d_collateral: uint256, _d_debt: uint256, _full: bool) -> int256: view

Previews the health after borrowing more.

Input	Type	Description
_user	address	Borrower address
_d_collateral	uint256	Additional collateral
_d_debt	uint256	Additional debt
_full	bool	Full (pessimistic) health

Returns: predicted health (int256).

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add_collateral_health_preview

LendController.add_collateral_health_preview(_user: address, _d_collateral: uint256, _full: bool) -> int256: view

Previews the health after adding collateral.

Input	Type	Description
_user	address	Borrower address
_d_collateral	uint256	Collateral to add
_full	bool	Full (pessimistic) health

Returns: predicted health (int256).

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remove_collateral_health_preview

LendController.remove_collateral_health_preview(_user: address, _d_collateral: uint256, _full: bool) -> int256: view

Previews the health after removing collateral.

Input	Type	Description
_user	address	Borrower address
_d_collateral	uint256	Collateral to remove
_full	bool	Full (pessimistic) health

Returns: predicted health (int256).

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repay_health_preview

LendController.repay_health_preview(_user: address, _d_debt: uint256, _full: bool) -> int256: view

Previews the health after repaying debt.

Input	Type	Description
_user	address	Borrower address
_d_debt	uint256	Debt to repay
_full	bool	Full (pessimistic) health

Returns: predicted health (int256).

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liquidate_health_preview

LendController.liquidate_health_preview(_user: address, _full: bool) -> int256: view

Previews what a user's health would be after liquidation.

Input	Type	Description
_user	address	Borrower address
_full	bool	Full (pessimistic) health

Returns: predicted health (int256).

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Lending-Specific

These functions are unique to LendController and not part of the shared controller.vy module.

available_balance

LendController.available_balance() -> uint256: view

Returns the amount of borrowed tokens currently available for new loans — i.e., the tokens deposited by lenders minus what's already lent out.

Returns: available balance (uint256).

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borrow_cap

LendController.borrow_cap() -> uint256: view

Returns the maximum total debt allowed for this market. If 0, there is no cap.

Returns: borrow cap (uint256).

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vault

LendController.vault() -> address: view

Returns the address of the associated ERC4626 vault.

Returns: vault address (address).

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set_borrow_cap

LendController.set_borrow_cap(_borrow_cap: uint256)

Guarded Method

This function is only callable by the factory admin.

Sets the maximum total debt cap for this market.

Input	Type	Description
_borrow_cap	uint256	New borrow cap (0 = unlimited)

Emits: SetBorrowCap event.

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set_admin_percentage

LendController.set_admin_percentage(_admin_percentage: uint256)

Guarded Method

This function is only callable by the factory admin.

Sets the percentage of interest that goes to the protocol (admin fees) rather than lenders.

Input	Type	Description
_admin_percentage	uint256	Admin fee percentage (scaled, max 50%)

Emits: SetAdminPercentage event.

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Calculations

max_borrowable

LendController.max_borrowable(_d_collateral: uint256, _N: uint256, _user: address) -> uint256: view

Returns the maximum amount that can be borrowed given a collateral amount and number of bands, respecting the borrow cap and available balance.

Input	Type	Description
_d_collateral	uint256	Collateral amount
_N	uint256	Number of bands
_user	address	Borrower address (for existing loan context)

Returns: max borrowable amount (uint256).

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min_collateral

LendController.min_collateral(_d_debt: uint256, _N: uint256) -> uint256: view

Returns the minimum collateral required for a given debt amount and number of bands.

Input	Type	Description
_d_debt	uint256	Desired debt amount
_N	uint256	Number of bands

Returns: minimum collateral required (uint256).

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calculate_debt_n1

LendController.calculate_debt_n1(_collateral: uint256, _debt: uint256, _N: uint256) -> int256: view

Calculates the upper band number (n1) for a loan with the given parameters. Used to determine where collateral will be placed in the AMM.

Input	Type	Description
_collateral	uint256	Collateral amount
_debt	uint256	Debt amount
_N	uint256	Number of bands

Returns: upper band number (int256).

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Configuration

set_amm_fee

LendController.set_amm_fee(_fee: uint256)

Guarded Method

This function is only callable by the factory admin.

Sets the swap fee on the associated AMM.

Input	Type	Description
_fee	uint256	New fee value

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set_borrowing_discounts

LendController.set_borrowing_discounts(_loan_discount: uint256, _liquidation_discount: uint256)

Guarded Method

This function is only callable by the factory admin.

Sets the loan discount and liquidation discount. The loan discount determines the maximum LTV, and the liquidation discount determines the threshold for liquidation.

Input	Type	Description
_loan_discount	uint256	New loan discount
_liquidation_discount	uint256	New liquidation discount

Emits: SetBorrowingDiscounts event.

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set_monetary_policy

LendController.set_monetary_policy(_monetary_policy: address)

Guarded Method

This function is only callable by the factory admin.

Sets the monetary policy contract that determines the borrow rate.

Input	Type	Description
_monetary_policy	address	New monetary policy address

Emits: SetMonetaryPolicy event.

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set_price_oracle

LendController.set_price_oracle(_price_oracle: address)

Guarded Method

This function is only callable by the factory admin.

Sets the price oracle for this market.

Input	Type	Description
_price_oracle	address	New price oracle address

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set_callback

LendController.set_callback(_callback: address)

Guarded Method

This function is only callable by the factory admin.

Sets the liquidity mining callback (gauge) for the AMM.

Input	Type	Description
_callback	address	Liquidity mining callback address

Emits: SetLMCallback event.

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Other Methods

amm

LendController.amm() -> address: view

Returns the AMM (LLAMMA) address for this market.

Returns: AMM address (address).

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amm_price

LendController.amm_price() -> uint256: view

Returns the current price from the AMM's internal oracle.

Returns: AMM price (uint256).

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monetary_policy

LendController.monetary_policy() -> address: view

Returns the current monetary policy address.

Returns: monetary policy address (address).

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liquidation_discount

LendController.liquidation_discount() -> uint256: view

Returns the current liquidation discount.

Returns: liquidation discount (uint256).

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loan_discount

LendController.loan_discount() -> uint256: view

Returns the current loan discount.

Returns: loan discount (uint256).

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admin_fees

LendController.admin_fees() -> uint256: view

Returns the amount of uncollected admin fees.

Returns: admin fees (uint256).

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admin_percentage

LendController.admin_percentage() -> uint256: view

Returns the current admin fee percentage.

Returns: admin percentage (uint256).

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collect_fees

LendController.collect_fees()

Collects accumulated admin fees and sends them to the fee receiver set in the factory.

Emits: CollectFees event.

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save_rate

LendController.save_rate()

Updates the stored interest rate from the monetary policy. This is called automatically during loan operations but can also be called externally to keep the rate fresh.

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version

LendController.version() -> String[10]: view

Returns the contract version string (e.g., "2.0.0-lend").

Returns: version string (String[10]).

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factory

LendController.factory() -> address: view

Returns the factory that deployed this controller.

Returns: factory address (address).

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