How ERC-2612 Permits Can Bundle a Bridge Deposit

An ERC-2612 permit lets a bridge set a token allowance from a signed message and consume it during the same deposit transaction. The wallet signs the allowance off-chain, then submits a transaction that calls the token’s permit function and the bridge’s deposit function. This removes the separate on-chain approve transaction; it does not remove the deposit transaction or its gas cost.

How does an ERC-2612 permit work?

The token contract adds a permit(owner, spender, value, deadline, v, r, s) function. The owner signs typed data that binds the allowance to a spender, an amount, a deadline and the owner’s current nonce. The token verifies the signature, sets allowance[owner][spender] to value, increments the owner’s nonce and emits an Approval event. A stale deadline, wrong nonce or invalid signature makes the call revert.

The signature authorizes an allowance update; it does not itself transfer tokens or call the bridge. To deposit in one transaction, the bridge or its router must accept the permit data, call permit on the token, then call transferFrom to take the deposit amount. If either step fails, the transaction reverts as a whole, so the allowance update does not persist without the deposit.

The destination of the allowance matters. The spender in the signed message must be the contract that will call transferFrom, which may be a router rather than the bridge contract that ultimately handles the deposit. For route choice and the steps around it, see this Mayan Bridge route-selection walkthrough. That wider choice is separate from the permit: a route that cannot consume the token’s permit still needs a prior approval.

What must the wallet and bridge support?

Both ends of the flow need compatible support. The token must implement ERC-2612, and the bridge’s deposit path must accept and process its permit. A conventional ERC-20 approve allowance does not imply that the token supports permit. Some tokens use a different signature-approval interface, so a wallet’s generic “sign” option cannot make an incompatible token or bridge support ERC-2612.

The message is encoded as typed structured data under EIP-712. Its domain separator ties the signature to the token contract’s domain, typically including the chain ID and verifying contract. Wallets should show the token, spender, allowance value and deadline clearly. A signature for one token contract or spender is not a general instruction to deposit through any bridge.

• Token: confirm the token exposes the expected permit interface on the source chain.
• Spender: compare the signed spender address with the contract that will pull the tokens.
• Amount: check the permitted value against the intended deposit; ERC-2612 sets the allowance to that value.
• Deadline: use a deadline that leaves enough time to submit the transaction without leaving the signature valid longer than needed.

What can make a one-step deposit fail?

A permit can expire before inclusion, use a nonce already consumed by another permit, or target a spender different from the bridge’s transfer path. The bridge call can also fail for its own reasons, such as a rejected token or invalid deposit parameters. In each case, the wallet sees a reverted transaction rather than a completed deposit.

There is a race edge case because ERC-2612 permits can be submitted by anyone who has the signature. If another party submits the permit first, the token consumes its nonce and installs the allowance. A bridge that always calls permit and reverts when that call fails may then reject the user’s deposit even though the allowance is already present. Integrations can handle this by attempting the permit and proceeding only if the required allowance is available. That behavior is an integration choice, not a guarantee of the ERC-2612 interface.

When is a permit the better approval path?

For a supported token and bridge, a permit is useful when the user wants to approve and deposit in one wallet transaction. It saves the separate approval transaction and avoids leaving an allowance from an earlier step if the user abandons the deposit. The bridge still receives an ordinary ERC-20 allowance, and after a successful deposit any unused portion may remain until spent or changed.

Check the actual spender and value in the signature request, then confirm that the wallet is submitting the intended deposit call. If the token or bridge lacks ERC-2612 support, use the bridge’s standard approval flow and verify the spender there. The practical rule is simple: one-step deposit works only when the token’s permit and the bridge’s transfer path are wired to the same allowance.