getBatchTxValue() doesn't include feeAmount for ETH_FEE_PROXY_CONTRACT, causing "Not enough funds" error

[MantisClone]

Problem

getBatchTxValue() doesn't include feeAmount when calculating the transaction value for ETH_FEE_PROXY_CONTRACT payments. This causes all native ETH batch payments with a fee to fail with "Not enough funds" during gas estimation.

The function calculates: requestAmount only
The contract requires: requestAmount + feeAmount

When a batch contains multiple ETH payments where any has a non-zero feeAmount, the transaction value is short by exactly that fee amount.

Buggy code (batch-conversion-proxy.ts lines 306-319):

const getBatchTxValue = (enrichedRequests: EnrichedRequest[]) => {
  return enrichedRequests.reduce((prev, curr) => {
    if (
      curr.paymentNetworkId !== ExtensionTypes.PAYMENT_NETWORK_ID.ANY_TO_ETH_PROXY &&
      curr.paymentNetworkId !== ExtensionTypes.PAYMENT_NETWORK_ID.ETH_FEE_PROXY_CONTRACT
    )
      return prev;
    return prev.add(
      curr.paymentNetworkId === ExtensionTypes.PAYMENT_NETWORK_ID.ANY_TO_ETH_PROXY
        ? curr.paymentSettings.maxToSpend
        : getAmountToPay(curr.request),  // ❌ Missing feeAmount
    );
  }, BigNumber.from(0));
};

Contract check (BatchNoConversionPayments.sol line 179):

require(address(this).balance >= rD.requestAmount + rD.feeAmount, 'Not enough funds');

Proposed Solution

Include feeAmount for ETH_FEE_PROXY_CONTRACT:

// ETH_FEE_PROXY_CONTRACT: include both amount AND fee
const { feeAmount } = getRequestPaymentValues(curr.request);
return prev.add(getAmountToPay(curr.request)).add(BigNumber.from(feeAmount || '0'));

Considerations

Verified with two test cases (batch of 2 payments: one with feeAmount, one without):

Test	Payment 1	Payment 1 Fee	Payment 2	TX Value	Needed	Shortfall
10 ETH	10 ETH	0.002 ETH	0.005 ETH	10.005 ETH	10.007 ETH	0.002 ETH
1 ETH	1 ETH	0.0002 ETH	0.0005 ETH	1.0005 ETH	1.0007 ETH	0.0002 ETH

Shortfall equals Payment 1's feeAmount in both cases.

Contract execution trace (1 ETH example):

1. Payment 1: require(1.0005 >= 1.0002) ✅ → balance = 0.0003 ETH
2. Payment 2: require(0.0003 >= 0.0005) ❌ FAIL

Impact:

• Severity: High - payments completely blocked
• Scope: All native ETH batch payments where any request has a non-zero feeAmount
• Workaround: None