Permit / Permit2

// Sign a permit for ERC-20 tokens that support EIP-2612
const permit = await signPermit({
  token: '0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48', // USDC
  owner: walletAddress,
  spender: protocolAddress,
  value: parseUnits('1000', 6),
  deadline: Math.floor(Date.now() / 1000) + 3600, // 1 hour
  signer
});

// permit contains { v, r, s, deadline, value }
// Protocol can now call token.permit(...) + token.transferFrom(...)

// Permit2 works with ANY ERC-20, not just EIP-2612 tokens
const permit2 = await signPermit2({
  token: '0x...', // Any ERC-20
  amount: parseUnits('1000', 18),
  expiration: Math.floor(Date.now() / 1000) + 86400, // 24 hours
  nonce: 0,
  spender: protocolAddress,
  signer
});

// Protocol calls Permit2.permitTransferFrom(...)

// Approve multiple tokens in one signature
const batchPermit = await signBatchPermit2({
  tokens: [
    { token: USDC, amount: parseUnits('1000', 6) },
    { token: WETH, amount: parseUnits('1', 18) },
  ],
  spender: protocolAddress,
  signer
});