Size a Bridge Claim Wallet for the Destination Chain

A bridge claim wallet should hold the destination chain’s native gas token in an amount that covers the current claim estimate plus a modest reserve. The bridged asset waiting in the bridge contract cannot pay for the transaction that releases it. For a Mantle withdrawal claimed on Ethereum, that means ETH on Ethereum; for a transaction claimed on Mantle, it means MNT on Mantle. The right balance depends on the claim transaction and current network conditions, not on the value being withdrawn.

That distinction is easy to miss because a wallet can show the same address on both chains while keeping separate balances on each. A fuller guide to setting up a Mantle Bridge wallet and network covers the preparation; here, the practical question is how to size the balance that pays the final claim. Check which network the claim transaction targets and which token that network accepts for gas.

Which token pays for a bridge claim?

The claim transaction is an on-chain transaction, so its fee is paid in the destination chain’s gas token. The token being claimed is the transaction’s output, not its fee source. A wallet may be due ETH, a stablecoin or another asset, but if the claim executes on Ethereum, the wallet needs ETH on Ethereum before it can submit the claim.

With the canonical Mantle route, withdrawing from Mantle to Ethereum has two distinct on-chain steps. The withdrawal begins on Mantle and uses MNT for gas there. Once the withdrawal becomes claimable, a separate transaction on Ethereum completes the exit and uses ETH for gas. The value in the pending withdrawal does not automatically fund that second transaction. A user with ample MNT on Mantle and no ETH on Ethereum can therefore have a ready withdrawal but still lack the balance needed to finish it.

Other bridges can use different settlement designs. Some execute a destination transaction through a relayer or bundle the claim with another action. That can change who submits the transaction or how a fee is presented, but the relevant check stays the same: identify what the interface asks the connected wallet to sign, which chain will execute it, and whether that flow charges the wallet directly. Do not assume one bridge’s claim rules apply to another.

How much native gas should the wallet hold?

Use the wallet’s estimate for the claim transaction as the starting point, then leave enough extra native token to absorb ordinary changes in the estimate. There is no universal fixed amount: gas usage depends on the transaction’s execution, and the gas price changes with network demand. A number that was sufficient for one claim at one moment may be too low for a later claim.

Wallets commonly show a maximum fee or estimated fee before signing. The maximum is a transaction limit, not necessarily the amount ultimately charged; the actual fee depends on gas used and the price accepted by the network. For sizing, treat the estimate as the minimum operational requirement and keep a reserve above it. The reserve should cover normal estimation error or a change in fee conditions, without leaving a large idle balance on the destination chain.

For a claim that needs a separate approval or another on-chain action, estimate and fund each required transaction. A plain claim usually does not need the same steps as approving an ERC-20 token for transfer, but the bridge interface determines the actual call sequence. If the wallet displays more than one transaction, add the displayed fees rather than budgeting only for the final confirmation.

• Confirm the destination network shown in the wallet before estimating.
• Check the required gas token on that network: ETH on Ethereum, MNT on Mantle.
• Read the claim screen’s estimate and maximum fee, then keep a reserve above the estimate.
• Include any additional transaction the interface requires, such as an approval.

What can stop a claim even when the withdrawal is ready?

A claim can fail to submit when the wallet’s balance of the native gas token is too low, even if the bridge shows the withdrawal as ready and the wallet holds more than enough of the asset being withdrawn. This is a funding problem on the destination chain. Adding the correct gas token to the wallet on the source chain does not solve it; the balance must be available on the network where the claim executes.

A stale estimate can also become inadequate if network fees rise before submission. Recheck the wallet’s current fee estimate when the claim is ready, especially if the withdrawal has been waiting for a long time. If the transaction is rejected for insufficient funds, the bridge withdrawal is not thereby reversed; fund the claim wallet on the destination chain and return to the existing withdrawal record to submit the claim.

Fund close to the live claim cost, with enough headroom to handle normal fee variation. For a Mantle-to-Ethereum withdrawal, keep that reserve as ETH on Ethereum, separate from MNT needed to initiate the withdrawal on Mantle. This avoids stranded claims while limiting how much gas token sits unused in the wallet.