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Documentation Index

Fetch the complete documentation index at: https://docs.relay.link/llms.txt

Use this file to discover all available pages before exploring further.

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Wallet Detection

When using Protocol v2 on EVM chains, you need to detect whether your user’s wallet is an EOA (Externally Owned Account) or a Smart Wallet to properly set the explicitDeposit parameter in your quote requests.

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Understanding Wallet Types

EOAs (Externally Owned Accounts) are regular wallets controlled by a private key, like MetaMask, Coinbase Wallet, and hardware wallets. These wallets can only execute one transaction at a time and cannot batch multiple operations together. Smart Wallets are contract-based wallets that can execute multiple operations in a single transaction. Examples include Gnosis Safe, Argent, and ERC-4337 compatible wallets. Smart wallets can batch approvals and deposits atomically, making multi-step flows more user-friendly.

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The Problem

Protocol v2 uses the Relay Depository contracts to enable trustless cross-chain payments. For ERC20 token deposits, there are two possible transaction flows: Explicit Deposits (2 transactions):
  1. User approves the Relay Depository contract to spend their tokens
  2. User calls the depositErc20 function to transfer tokens with an order ID
Implicit Deposits (1 transaction):
  1. User transfers tokens directly to the solver with order ID encoded in transaction calldata
The challenge is that implicit deposits only work reliably for EOAs, while explicit deposits work for all wallet types but create poor UX for EOAs who must execute two separate transactions.

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The Solution

By detecting wallet type, you can set the explicitDeposit parameter to choose the optimal flow:
  • explicitDeposit: false - Enables implicit deposits for EOAs (1 transaction)
  • explicitDeposit: true - Uses explicit approval flow for smart wallets (2 transactions, can be batched)
  • Default: true (safe fallback for all wallet types)

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When to Use Wallet Detection

You should implement wallet detection when:
  • Using protocolVersion: "v2" or "preferV2"
  • User is on an EVM chain
  • User is depositing ERC20 tokens (not native ETH)
  • You want to optimize transaction flow for your users
For native ETH deposits, wallet detection is not necessary since no approval is required.

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Detection Methods

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1. Smart Wallet Capabilities (EIP-5792)

Check if the wallet advertises smart wallet capabilities: 
const capabilities = await wallet.getCapabilities({
	account: wallet.account,
	chainId,
});

const hasSmartWalletCapabilities = Boolean(
	capabilities?.atomicBatch?.supported ||
		capabilities?.paymasterService?.supported ||
		capabilities?.auxiliaryFunds?.supported ||
		capabilities?.sessionKeys?.supported
);

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2. Contract Code Detection

Check if the wallet address has deployed contract code: 
const code = await publicClient.getCode({
	address: walletAddress,
});

const hasCode = Boolean(code && code !== "0x");

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3. EIP-7702 Delegation Detection

Check if the wallet uses EIP-7702 delegation (code starts with 0xef01): 
const isEIP7702Delegated = Boolean(
	code && code.toLowerCase().startsWith("0xef01")
);
Note: EIP-7702 delegated accounts are technically EOAs but gain smart wallet capabilities through authorization signatures. They require explicitDeposit: true for reliable batching and execution.

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Final Determination

const isSmartWallet =
	hasSmartWalletCapabilities || hasCode || isEIP7702Delegated;
const isEOA = !isSmartWallet;

// Set explicitDeposit based on wallet type
const explicitDeposit = !isEOA || isEIP7702Delegated;

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Safety Checks

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Zero Native Balance Check

If the user has zero native currency (ETH, MATIC, etc.), force explicitDeposit: true to avoid failed transactions due to insufficient gas: 
if (nativeBalance === 0n) {
	explicitDeposit = true;
}

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Low Transaction Count Check

If the wallet has 1 or fewer transactions on the source chain, force explicitDeposit: true as this may indicate a new wallet requiring explicit handling: 
if (transactionCount <= 1) {
	explicitDeposit = true;
}

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Implementation Example

Here’s a complete implementation for detecting wallet types: 
export const detectWalletType = async (
	wallet: WalletClient,
	chainId: number
) => {
	if (!wallet.account) {
		return { isEOA: false, isEIP7702Delegated: false };
	}

	try {
		// Check 1: Smart wallet capabilities
		let hasSmartWalletCapabilities = false;
		try {
			const capabilities = await wallet.getCapabilities({
				account: wallet.account,
				chainId,
			});

			hasSmartWalletCapabilities = Boolean(
				capabilities?.atomicBatch?.supported ||
					capabilities?.paymasterService
						?.supported ||
					capabilities?.auxiliaryFunds
						?.supported ||
					capabilities?.sessionKeys?.supported
			);
		} catch (capabilitiesError) {
			// Wallet doesn't support capabilities API
		}

		// Check 2 & 3: Contract code detection
		const publicClient = createPublicClient({
			chain: getChainById(chainId),
			transport: http(),
		});

		const code = await publicClient.getCode({
			address: wallet.account.address,
		});

		const hasCode = Boolean(code && code !== "0x");
		const isEIP7702Delegated = Boolean(
			code && code.toLowerCase().startsWith("0xef01")
		);

		const isSmartWallet =
			hasSmartWalletCapabilities ||
			hasCode ||
			isEIP7702Delegated;
		const isEOA = !isSmartWallet;

		return { isEOA, isEIP7702Delegated };
	} catch (error) {
		// On error, assume not EOA (safer default)
		return { isEOA: false, isEIP7702Delegated: false };
	}
};

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Example Scenarios

Wallet TypeDetection ResultexplicitDepositUser Experience
Regular EOA (MetaMask, Coinbase)EOA detectedfalse1 transaction
Smart Wallet (Gnosis Safe, Argent)Smart wallet detectedtrue2 transactions (can be batched)
EIP-7702 Delegated EOASmart wallet detectedtrue2 transactions (can be batched)
Detection ErrorUnknowntrue2 transactions (safe fallback)

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API Usage

Include the explicitDeposit parameter in your quote requests: 
const quoteRequest = {
	user: userAddress,
	originChainId: sourceChainId,
	destinationChainId: targetChainId,
	originCurrency: sourceCurrencyAddress,
	destinationCurrency: targetCurrencyAddress,
	recipient: recipientAddress,
	amount: amountInWei,
	tradeType: "EXACT_INPUT",
	protocolVersion: "preferV2",
	explicitDeposit: explicitDepositValue, // Based on your detection
};

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Expected User Experience

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For EOA Users (explicitDeposit: false)

✅ Step 1: Transfer USDC directly to solver with order ID encoded in calldata
✅ One wallet confirmation
✅ Faster execution and lower cost
✅ Simpler, more intuitive user experience

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For Smart Wallet Users (explicitDeposit: true)

✅ Step 1: Approve Relay Depository contract to spend USDC
✅ Step 2: Call depositErc20() to deposit USDC
✅ Steps can be batched into single confirmation (ERC-4337/EIP-5792)
✅ Reliable, predictable execution through Depository architecture
✅ Full smart wallet capabilities (fee sponsorship, session keys, etc.)

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Best Practices

  1. Handle errors gracefully - Return { isEOA: false, isEIP7702Delegated: false } on errors (safer default)
  2. Add timeout - Detection should timeout after ~1 second to avoid blocking UX
  3. Cache results - Cache detection results per wallet/chain combination to avoid repeated calls
  4. Include safety checks - Always check native balance and transaction count as additional safety measures
  5. Only use with Protocol v2 - The explicitDeposit parameter is only relevant for Protocol v2

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Troubleshooting

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Detection Returns Incorrect Results

  • Ensure you’re using the correct chain ID
  • Verify the RPC endpoint is returning accurate data
  • Check that wallet capabilities API is properly supported

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Quote Requests Failing

  • Verify explicitDeposit is only included when using v2 protocol
  • Ensure user has sufficient native currency for gas
  • Check that the wallet address is valid
By implementing proper wallet detection, you can provide optimal user experience for both EOA and smart wallet users while ensuring transaction reliability.