compound-patterns

Compound V3 (Comet) Integration

Architecture

Compound V3 (Comet) is a fundamentally different design from V2. Each Comet deployment is a single-asset market — one base asset (e.g., USDC) with multiple collateral assets. There are no cTokens; the Comet contract itself tracks balances.

Component	Description
Comet	Core market contract (one per base asset)
CometRewards	Claims COMP rewards for suppliers/borrowers
Configurator	Governance-controlled parameter updates
BulkerV2	Batch operations including native ETH wrapping

Supply / Withdraw Base Asset

import {IComet} from "./interfaces/IComet.sol";

IComet comet = IComet(COMET_USDC);

// Supply base asset (earn interest)
IERC20(usdc).approve(address(comet), amount);
comet.supply(usdc, amount);

// Withdraw base asset
comet.withdraw(usdc, amount);
// Use type(uint256).max for full withdrawal

Collateral Management

// Supply collateral (does NOT earn interest)
IERC20(weth).approve(address(comet), amount);
comet.supply(weth, amount);

// Withdraw collateral
comet.withdraw(weth, amount);

// Check collateral balance
uint256 collateral = comet.collateralBalanceOf(account, weth);

Borrowing

// Borrow base asset against collateral
// Simply withdraw more base than you supplied
comet.withdraw(usdc, borrowAmount);

// Repay borrow — supply base asset
IERC20(usdc).approve(address(comet), repayAmount);
comet.supply(usdc, repayAmount);

Account State

// Positive = supplying, negative = borrowing
int256 balance = comet.balanceOf(account);

// Check if account is liquidatable
bool isLiquidatable = comet.isLiquidatable(account);

// Get borrow balance (always positive)
uint256 borrowBalance = comet.borrowBalanceOf(account);

// Check if an action is allowed
bool canBorrow = comet.isBorrowCollateralized(account);

Liquidation via Absorb

// Compound V3 uses "absorb" instead of traditional liquidation
// Anyone can call absorb on an underwater account
address[] memory accounts = new address[](1);
accounts[0] = underwaterAccount;
comet.absorb(msg.sender, accounts);

// After absorb, protocol holds the collateral
// Buy collateral at a discount through the Comet contract
uint256 reserves = comet.getCollateralReserves(weth);
comet.buyCollateral(weth, minAmount, baseAmount, recipient);