approveOperationalFee

Grant operational-fee allowances to the gasless fee charger, as the paying sub-account.


import { approveOperationalFee, getOperationalFeeAllowance } from "@symmio/trading-core";
import { parseUnits } from "viem";
 
// A bounded fee budget of 5 collateral tokens, in 18-decimal Core units.
const hash = await approveOperationalFee(config, {
  account: subAccount,
  amounts: [parseUnits("5", 18)],
});
 
// Once the transaction has landed, read the allowance back before relying on it.
const { allowance } = await getOperationalFeeAllowance(config, { payer: subAccount });

The diamond keys allowances by msg.sender, so the call is routed through the AccountLayer _call proxy — the diamond sees the sub-account as the payer. A direct wallet call would grant the allowance from the wrong account. The connected wallet must be the sub-account’s owner. Under the hood this encodes approveOperationalFeeWithMultiplier(chargers[], amounts[], feeMultipliers[]); chargers defaults to the chain’s gasless.gaslessLayerAddress and feeMultipliers to OPERATIONAL_FEE_LIST_PRICE_MULTIPLIER (10000n — list price, in basis points). Because the call always sets a multiplier, omitting feeMultipliers resets a previously set one to list price.

Amounts and what an approval does

Amounts are 18-decimal Core units, the scale of the Core balance fees are drawn from, not the collateral token’s decimals. On a 6-decimal USDC chain parseUnits("5", 18) is a 5 USDC budget, while parseUnits("5", 6) would allow only 0.000000000005 USDC. To start from a token amount, convert it with collateralToCore18.
Each amount replaces the current allowance. It works like ERC-20 approve, not an increment, and every relayed charge decrements it. Choose a bounded budget sized to the operations you intend to relay, not maxUint256: a bounded allowance caps what the charger can ever draw from the payer in fees.
The charger is the GaslessLayer proxy (gasless.gaslessLayerAddress), not the relayer’s executor address. An ERC-20 approve of the collateral token is a different permission and grants nothing here.
Approving adds no balance. The fee is still drawn from the payer’s Core balance after the operation executes, so fund the sub-account as well as approving it.

Grant the allowance before relying on gasless execution. The service simulates every relay before accepting it, so a payer without enough allowance is refused up front, with no request id. Today that arrives as HTTP 400 SIMULATION_REVERTED carrying the Core revert OperationalFee: Allowance exceeded in the vendor detail; a deployment can also report the service code INSUFFICIENT_ALLOWANCE. Read either with parseGaslessErrorDetail. A payer short of Core balance is refused the same way with OperationalFee: Insufficient balance, which no approval fixes. This wallet-paid path is the one that always works; the approval is itself relayable too (pass gasless: true once gasless execution is active). Reducing an existing allowance can be timelocked on-chain — see getOperationalFeeAllowance.

Parameters

accountAddressrequired

The sub-account that pays operational fees; the connected wallet must be its owner.

amountsreadonly bigint[]required

Allowance per charger, parallel to chargers, in 18-decimal Core units. Each value replaces the current allowance. Use a bounded budget.

chargersreadonly Address[]optional

The fee chargers to approve. Defaults to [gasless.gaslessLayerAddress], the GaslessLayer proxy.

feeMultipliersreadonly bigint[]optional

Fee multiplier per charger in basis points; defaults to 10000n (list price) for every charger, replacing any multiplier set before.

gaslessboolean | GaslessWriteOptionsoptional

Relay the approval itself through the gasless service — see Relayable writes.

chainIdnumberoptional

Target chain id. Defaults to the config’s defaultChainId.

fromAddressoptional

Signer override for the wallet-client resolver.

simulateBeforeWritebooleanoptional

Dry-run the _call before broadcasting; defaults to the config’s global setting.

Returns

Promise<Hash>

The submitted transaction hash.

Throws

SymmError("validation", "GASLESS_CHARGER_REQUIRED") — no chargers given and the chain has no gasless block to default from.
SymmError("validation", "OPERATIONAL_FEE_APPROVAL_MISMATCH") — chargers / amounts / feeMultipliers lengths disagree.
SymmError when the chain is unsupported or no wallet client is available; viem errors from the _call write.