Learn how OneBalance automatically handles token approvals for DeFi operations while maintaining security best practices.
Important: Never manually call approve() functions when using OneBalance. The platform automatically manages all required approvals as part of the contract call preparation process.

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How Approval Management Works

When you specify allowanceRequirements, OneBalance automatically:
  1. Checks existing allowances - Verifies current approval amounts
  2. Adds approval transactions - Only when needed, for exact amounts
  3. Executes your operations - Runs your contract calls
  4. Removes excess approvals - Cleans up remaining allowances for security
This prevents front-running attacks and ensures optimal gas usage.
OneBalance bundles approvals, your calls, and approval cleanup into a single user operation for atomic execution.

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Basic Example

Here’s how to properly handle approvals for a DEX swap:
swap-with-approval.ts
import { encodeFunctionData, parseAbi, parseUnits } from 'viem';

const USDC_BASE = '0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913';
const UNISWAP_ROUTER = '0x2626664c2603336E57B271c5C0b26F421741e481';

// ✅ Correct - Let OneBalance handle approvals
const prepareRequest = {
  account: {
    sessionAddress: '0x...',
    adminAddress: '0x...',
    accountAddress: '0x...'
  },
  targetChain: 'eip155:8453', // Base
  calls: [{
    to: UNISWAP_ROUTER,
    data: encodeFunctionData({
      abi: parseAbi(['function exactInputSingle((address tokenIn, address tokenOut, uint24 fee, address recipient, uint256 deadline, uint256 amountIn, uint256 amountOutMinimum, uint160 sqrtPriceLimitX96))']),
      functionName: 'exactInputSingle',
      args: [{
        tokenIn: USDC_BASE,
        tokenOut: '0x...',
        fee: 3000,
        recipient: account.accountAddress,
        deadline: Math.floor(Date.now() / 1000) + 3600,
        amountIn: parseUnits('100', 6), // 100 USDC
        amountOutMinimum: 0,
        sqrtPriceLimitX96: 0
      }]
    }),
    value: '0'
  }],
  allowanceRequirements: [{
    assetType: `eip155:8453/erc20:${USDC_BASE}`,
    amount: parseUnits('100', 6).toString(), // Exact amount needed
    spender: UNISWAP_ROUTER
  }],
  tokensRequired: [{
    assetType: `eip155:8453/erc20:${USDC_BASE}`,
    amount: parseUnits('100', 6).toString()
  }]
};

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What NOT to Do

Common Mistake: Including approval calls manually will cause transaction failures.
wrong-approach.ts
// ❌ WRONG - Don't do this!
const badRequest = {
  calls: [
    {
      // This will cause the transaction to fail
      to: USDC_BASE,
      data: encodeFunctionData({
        abi: parseAbi(['function approve(address spender, uint256 amount)']),
        functionName: 'approve',
        args: [UNISWAP_ROUTER, parseUnits('100', 6)]
      }),
      value: '0'
    },
    {
      to: UNISWAP_ROUTER,
      data: swapCallData,
      value: '0'
    }
  ]
  // No allowanceRequirements - this is the problem!
};

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Common Patterns

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DEX Swaps

dex-swap.ts
// Uniswap V3 swap requiring token approval
allowanceRequirements: [{
  assetType: `eip155:8453/erc20:${inputToken}`,
  amount: inputAmount.toString(),
  spender: UNISWAP_V3_ROUTER
}]

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Lending Protocols

aave-deposit.ts
// Aave deposit requiring pool approval
allowanceRequirements: [{
  assetType: `eip155:1/erc20:${asset}`,
  amount: depositAmount.toString(),
  spender: AAVE_POOL_ADDRESS
}]

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Multiple Token Operations

multi-token-defi.ts
// Complex DeFi operation requiring multiple approvals
allowanceRequirements: [
  {
    assetType: `eip155:1/erc20:${tokenA}`,
    amount: amountA.toString(),
    spender: DEX_ROUTER
  },
  {
    assetType: `eip155:1/erc20:${tokenB}`,
    amount: amountB.toString(),
    spender: LENDING_POOL
  }
]

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NFT Purchases

nft-purchase.ts
// NFT marketplace purchase with USDC
allowanceRequirements: [{
  assetType: 'eip155:1/erc20:0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48',
  amount: nftPrice.toString(),
  spender: NFT_MARKETPLACE_ADDRESS
}]

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Special Cases

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Native Tokens (ETH, MATIC, etc.)

Native tokens don’t require approvals - they’re sent directly:
native-token.ts
// No allowanceRequirements needed for ETH
calls: [{
  to: CONTRACT_ADDRESS,
  data: contractCallData,
  value: ethAmount.toString() // Send ETH directly
}],
tokensRequired: [{
  assetType: 'eip155:1/slip44:60', // ETH
  amount: ethAmount.toString()
}]
// No allowanceRequirements array needed

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Existing Allowances

OneBalance optimizes gas by checking existing allowances:

Sufficient Allowance

If current allowance ≥ required amount, no approval transaction is added

Insufficient Allowance

Only approves the exact amount needed, not unlimited approvals

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Security Features

OneBalance’s approval management includes several security measures:
  • Exact Amount Approvals - Never approves more than needed
  • Automatic Cleanup - Removes remaining allowances after execution
  • Front-running Protection - Atomic bundling prevents manipulation
  • Approval Validation - Verifies spender addresses match your calls

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Best Practices

1

Use allowanceRequirements

Always specify token approvals in the allowanceRequirements array, never in calls
2

Specify Exact Amounts

Use precise amounts to minimize approval exposure
3

Verify Spender Addresses

Double-check that spender addresses match your contract calls
4

Test with Small Amounts

Start with small transactions to verify your integration

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TypeScript Interface

interfaces.ts
interface AllowanceRequirement {
  assetType: string;  // Format: "eip155:chainId/erc20:tokenAddress"
  amount: string;     // Amount in smallest unit (e.g., wei)
  spender: string;    // Contract address that needs approval
}

interface PrepareCallRequest {
  account: Account;
  targetChain: string;
  calls: CallData[];
  allowanceRequirements: AllowanceRequirement[];
  tokensRequired: TokenRequirement[];
}

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Troubleshooting

  • Transaction fails with ‘Approval not found’ - Make sure you’re using allowanceRequirements instead of manual approval calls.
  • Gas costs seem high - OneBalance only adds approvals when needed. High gas might indicate multiple tokens or complex operations.
  • Spender address mismatch - Verify that the spender in allowanceRequirements matches the contract address in your calls.
  • Amount calculation errors - Ensure you’re using the correct decimals for the token (e.g., 6 for USDC, 18 for most ERC20s).
Need help? Check the troubleshooting guide for common issues and solutions.