Why Some Crypto Bridges Require a Separate Claim

A bridge needs a separate claim transaction when the destination chain must verify a completed source-chain transfer before releasing or minting the funds. The first transaction starts the transfer; the claim submits the evidence that lets the destination contract finish it.

Each blockchain keeps its own transaction history and charges its own gas, so a source-chain transaction cannot directly execute a destination-chain action. The bridge must carry a message or proof between them, then have someone submit it where the funds will arrive. A Bungee Bridge checklist for team transfers covers practical checks around using a bridge; the key mechanics here are how the destination verifies and completes a transfer.

What does the claim transaction do?

The claim tells the destination contract which source transfer to complete and supplies the data or proof required by that bridge. The contract checks that the transfer is valid and has not already been claimed, then releases locked assets or mints the destination representation.

In a lock-and-mint design, the source contract may lock tokens while the destination contract mints corresponding tokens after verification. In a burn-and-release design, tokens are burned on the source chain and released from reserves on the destination. In either case, the claim is the destination-side instruction that completes the movement.

• Source transaction: starts the transfer by locking or burning assets and recording its details.
• Finality period: gives the bridge time to establish that the source transaction is settled under its rules.
• Proof or message: carries the transfer details to the destination contract.
• Claim transaction: submits that information and triggers release or minting.

Why can’t the bridge complete both sides at once?

The two chains do not share one transaction processor, so a transaction on one chain cannot atomically commit a change on the other. If the source transfer succeeds but the destination action fails or is delayed, the bridge needs a way to retry or complete the second step without repeating the first.

A separate claim also gives the destination contract a defined verification point. Depending on the bridge, it may check a validator attestation, a cryptographic proof, or a message delivered by a relayer. The bridge’s security model determines who can provide that evidence and how the destination chain decides it is valid.

Who submits the claim, and what does it cost?

The user submits it in some bridges; in others, a relayer does so and may charge a fee or include that cost in the quoted rate. Either way, the destination transaction consumes gas on that chain. If the user must claim directly, they need its native gas token and must use the correct destination wallet and transfer record.

Relayers can make the process feel like one action by advancing funds on the destination chain before final settlement, then seeking reimbursement under the protocol’s rules. That removes a user-facing claim in some designs, but it does not remove cross-chain verification or the costs and risks borne by relayers.

Before bridging, check whether the quote includes destination gas, whether delivery is automatic, and what status the bridge shows if a transfer is pending. A separate claim is an extra transaction, but it can be a necessary step in the bridge’s settlement design; the useful question is who submits it, what evidence it checks, and who pays its gas.