Integrate Lending

Let users supply USDC directly to Morpho, Moonwell, or Aave lending markets on Base.

Let users supply USDC to a third-party money market and manage the resulting protocol position from your app. Your app prepares and simulates each call; the user signs from their own wallet.

Demo

Supply USDC

These examples use viem@2.55.11, @morpho-org/morpho-sdk@5.4.1, @moonwell-fi/moonwell-sdk@0.22.0, and @aave-dao/aave-address-book@4.65.5.

clients.ts creates pinned Base mainnet public and wallet clients from a server-side PRIVATE_KEY; every example imports those concrete clients and is type-checked in the verified DeFi fixtures.

Morpho

Supply to Morpho’s WETH/USDC market. Fetching by market ID avoids hardcoding its oracle, interest-rate model, and LLTV parameters.

supply-morpho.ts

import { publicClient, walletClient } from './clients.js';
import { type MarketId } from '@morpho-org/blue-sdk';
import { fetchMarketParams } from '@morpho-org/blue-sdk-viem';
import {
  isRequirementSignature,
  morphoViemExtension,
} from '@morpho-org/morpho-sdk';
import { parseUnits } from 'viem';
import { base } from 'viem/chains';

const marketId =
  '0x8793cf302b8ffd655ab97bd1c695dbd967807e8367a65cb2f4edaf1380ba1bda' as MarketId;
const user = walletClient.account.address;
const client = publicClient.extend(morphoViemExtension());
const params = await fetchMarketParams(marketId, publicClient);
const market = client.morpho.blue(params, base.id);
const action = market.supply({
  amount: parseUnits('1000', 6),
  userAddress: user,
  marketData: await market.getMarketData(),
});

const signatures = [];
for (const requirement of await action.getRequirements()) {
  if (isRequirementSignature(requirement)) {
    signatures.push(await requirement.sign(walletClient, user));
  } else {
    const hash = await walletClient.sendTransaction(requirement);
    await publicClient.waitForTransactionReceipt({ hash });
  }
}
const request = action.buildTx(signatures);
await publicClient.call({ account: user, ...request });
const hash = await walletClient.sendTransaction(request);
await publicClient.waitForTransactionReceipt({ hash });

Moonwell

Use the Moonwell SDK as the source of current Base deployment addresses, then call the USDC market with viem.

supply-moonwell.ts

import { publicClient, walletClient } from './clients.js';
import { createMoonwellClient } from '@moonwell-fi/moonwell-sdk';
import { parseAbi, parseUnits } from 'viem';

const moonwell = createMoonwellClient({
  networks: { base: { rpcUrls: ['https://mainnet.base.org'] } },
});
const env = moonwell.environments.base;
const usdc = env.tokens.USDC.address;
const mUsdc = env.tokens.MOONWELL_USDC.address;
const amount = parseUnits('1000', 6);

const erc20Abi = parseAbi(['function approve(address,uint256) returns (bool)']);
const marketAbi = parseAbi(['function mint(uint256) returns (uint256)']);
const approval = await publicClient.simulateContract({
  account: walletClient.account,
  address: usdc, abi: erc20Abi, functionName: 'approve', args: [mUsdc, amount],
});
await publicClient.waitForTransactionReceipt({
  hash: await walletClient.writeContract(approval.request),
});

const supply = await publicClient.simulateContract({
  account: walletClient.account,
  address: mUsdc, abi: marketAbi, functionName: 'mint', args: [amount],
});
if (supply.result !== 0n) throw new Error(`Moonwell error code ${supply.result}`);
await publicClient.waitForTransactionReceipt({
  hash: await walletClient.writeContract(supply.request),
});

Aave

Resolve the Base Pool and asset addresses from Aave’s official address book, then approve and supply through the Aave V3 Pool with viem.

supply-aave.ts

import { publicClient, walletClient } from './clients.js';
import { AaveV3Base } from '@aave-dao/aave-address-book';
import { parseAbi, parseUnits } from 'viem';

const user = walletClient.account;
const amount = parseUnits('1000', 6);
const erc20Abi = parseAbi(['function approve(address,uint256) returns (bool)']);
const poolAbi = parseAbi([
  'function supply(address,uint256,address,uint16)',
]);

const approval = await publicClient.simulateContract({
  account: user, address: AaveV3Base.ASSETS.USDC.UNDERLYING,
  abi: erc20Abi, functionName: 'approve', args: [AaveV3Base.POOL, amount],
});
await publicClient.waitForTransactionReceipt({
  hash: await walletClient.writeContract(approval.request),
});

const supply = await publicClient.simulateContract({
  account: user, address: AaveV3Base.POOL, abi: poolAbi,
  functionName: 'supply',
  args: [AaveV3Base.ASSETS.USDC.UNDERLYING, amount, user.address, 0],
});
await publicClient.waitForTransactionReceipt({
  hash: await walletClient.writeContract(supply.request),
});

Supply rates are variable, withdrawals depend on market liquidity, and every integration inherits protocol, oracle, and approval risk. Display current terms and simulate the exact transaction before asking the user to sign.

See also

• Integrate borrowing · Integrate an earn product
• Integrate DeFi overview