Who Pays Gas in a Sponsored Bridge Transaction?

A sponsored bridge transaction lets a service pay the source-chain gas for an action your wallet authorizes, so your account does not need that chain’s native token for that step. The sponsor pays the network fee; it does not take custody of the assets being bridged or guarantee that the destination transfer will complete. To understand the flow, separate the wallet’s authorization, the source-chain transaction, and the bridge’s cross-chain settlement.

How does a sponsored bridge transaction work?

Your wallet signs an instruction, and a relayer or paymaster submits a transaction that consumes that authorization. The wallet still approves the action. Sponsorship changes who supplies gas and broadcasts the transaction; it does not remove the authorization step.

There are several mechanisms behind this pattern. In an ERC-2771 meta-transaction, a relayer submits a signed request through a trusted forwarder. The recipient contract reads the signer’s address from the forwarded call data, but only if the forwarder is trusted. In ERC-4337 account abstraction, a smart account signs a UserOperation and a bundler submits it through the EntryPoint contract. A paymaster can agree to cover its gas costs after validating the operation. An ordinary externally owned account cannot use that paymaster path by itself; it needs a compatible smart account and supporting infrastructure.

Bridge interfaces can combine these steps behind one button, but the implementation varies. For a route-level account of Mantle’s bridge paths and delays, see Mantle Bridge. That route choice affects how assets move; sponsorship describes how a transaction’s network gas is paid. They are related in the user flow, but they are different mechanisms.

What does the sponsor pay for?

The sponsorship policy defines which transaction costs the sponsor accepts. It may cover the source-chain transaction that initiates the bridge, a token approval, or a smart account operation that batches the approval and deposit. It may cover only some of those actions. A bridge quote or wallet confirmation should make clear which operation is sponsored and whether the sponsor imposes limits or eligibility rules.

Network gas is separate from bridge and token costs. A bridge can charge a service fee or apply a route-specific exchange rate. A token may also impose transfer behavior or fees. Sponsorship does not, by itself, waive those costs. Nor does it mean the sponsor will pay for destination-chain gas: destination execution may be handled by a relayer, paid from bridged funds, or require the recipient to hold the destination network’s native token.

This distinction matters when an interface calls a transfer “gasless.” The wallet may avoid paying gas for one transaction while the overall route still has fees, requires a token approval, or leaves the recipient unable to make a later transaction without destination gas. Treat “sponsored” as a description of a specific transaction’s gas payer, not the whole bridge journey.

What can make a sponsored bridge fail?

A sponsor can reject an operation before it reaches the chain. Its policy may require a supported network, contract, token, amount, or user status. In ERC-4337, the paymaster validates the UserOperation through the EntryPoint; the bundler also checks whether the operation is valid and can be included. If validation fails, the operation may never enter a block.

After submission, the source transaction can revert or the bridge can fail to complete its later settlement. Sponsorship does not make those stages atomic. A successful source-chain deposit can be followed by a delayed or unsuccessful destination action, depending on the bridge’s design and route. Check the source transaction status and the bridge’s own transfer status separately. A wallet reporting that it submitted an operation is not proof that the destination asset arrived.

Before signing, identify the exact operation being authorized and the contracts it calls. Check whether the wallet is asking for an approval as well as a deposit, and whether that approval is limited to the amount needed. Confirm the destination network and token. If the transaction fails, use the bridge’s transfer record and source transaction hash to distinguish a sponsor rejection from an on-chain revert or a pending cross-chain step.

When is sponsorship useful, and what should you check?

Sponsorship is most useful when the user holds the asset to bridge but lacks the source chain’s native token for gas. It removes that funding hurdle for covered operations. The trade-off is reliance on sponsor availability and policy: the service can refuse requests, apply limits, or stop sponsoring. The underlying bridge route still determines settlement behavior, fees, and delays.

Before proceeding, check these points:

• Which transaction or transactions the sponsor covers, including any required approval.
• Whether the wallet is using a trusted-forwarder flow or a smart account with a paymaster.
• Which bridge fees and destination-chain costs remain payable.
• How to verify the source transaction and track the destination settlement if it is delayed.

The practical test is simple: know what your wallet signs, what the sponsor pays, and what the bridge still has to deliver. A sponsored source transaction can make the first step accessible without native gas in the wallet. It cannot make an unsupported operation valid or guarantee that every later bridge step succeeds.