[VPD-675]: Repay Logic Improvement

[Debugger022]

VIP-597: VToken Repayment Logic Improvement

Description

This proposal updates the repayment logic in VToken to automatically cap repayments at the borrower's outstanding debt. The change improves safety, simplifies repayment flows, and prevents unintended over-repayment.

Context

Currently, only a repayment of type(uint256).max is treated as a full repayment. All other over-estimates are processed as-is, which can cause wasteful transactions and requires users to calculate exact debt amounts.

This update generalises the logic so that any repayment exceeding the borrower's debt is capped, improving safety and user experience across repayment and liquidation scenarios.

Proposed Change

Update in VToken.sol (repayBorrowFresh):

Before:

if (repayAmount == type(uint256).max) {
    vars.repayAmount = vars.accountBorrows;
} else {
    vars.repayAmount = repayAmount;
}

After:

vars.repayAmount = repayAmount >= vars.accountBorrows ? vars.accountBorrows : repayAmount;

Impact

• Repayment Functions: Users can safely over-estimate repayments for repayBorrow and repayBorrowBehalf
• Liquidations: Repayments are capped, avoiding overpayment during liquidation
• Events: RepayBorrow events now reflect the actual repaid amount
• Math Safety: Prevents underflow in repayment calculations

Scope

• Contract: VToken
• Function: repayBorrowFresh
• Change Type: Single-line logic update
• Code Impact: Minimal (2 additions, 6 deletions)

Summary

If approved, this VIP will:

• Cap repayments at the borrower's outstanding debt
• Simplify repayment logic and improve user safety
• Prevent overpayment during normal or liquidation flows
• Maintain backward compatibility for standard repayment scenarios

[GitGuru7]

overall LGTM, I think we should also upgrade vXAUM on mainnet. The VIP is currently in the queue, we can still include this upgrade and avoid creating an additional VIP for it later.

[GitGuru7]

Suggested change

	// TODO: Set the correct block number
	const BLOCK_NUMBER = 92753245;
	const BLOCK_NUMBER = 93334375;

[Debugger022]

0d742ea

[fred-venus]

from claude code

VIP description does not disclose flash loan removal. The new implementation completely removes all flash loan infrastructure (~6 functions including transferOutUnderlyingFlashLoan, setFlashLoanEnabled, calculateFlashLoanFee, etc). Flash loans are currently enabled (isFlashLoanEnabled=true) on at least vUSDT, vUSDC, vBTC, vETH, vXVS. Although flashLoanFeeMantissa=0 suggests limited active use, this is a material behavioral change that must be disclosed. Additional undisclosed changes: borrowFresh simplified (removed shouldTransfer param), event emission ordering fixed in _setComptrollerFresh/_setInterestRateModelFresh.

[fred-venus]

i checked, seems yes

existing on-chain

new

[Debugger022]

fixed 8fd80b2

[fred-venus]

venus.io#/governance/proposal/597?chainId=56