Gasless token swaps: who pays settlement gas
For approved ERC-20 tokens, sign an off-chain order and a solver pays settlement gas. Approvals, native-token orders and other transactions can still need gas.
For a standard ERC-20 swap with sufficient allowance, you sign an off-chain order and a solver submits the settlement transaction. On Ophis (the intent-based DEX aggregator at ophis.fi), that order is EIP-712 typed data signed by your wallet; a competing solver network executes it on-chain and pays the gas, and the fee comes out of the trade. Approval transactions can still require native gas. An unfilled signed ERC-20 order has no settlement fee; any approval gas already spent is not refunded.
The rest of this article is the mechanism: where the gas cost actually goes, the places it can still appear, and why this matters most for new wallets, AI agents, and anyone trading across many chains.
Signing is not sending
A normal swap is a transaction. You build it, you broadcast it, you pay gas for it in the chain’s native token, and you pay whether it succeeds or reverts. Gasless trading replaces the transaction with a message.
An Ophis order pins down the trade: the token you sell, the token you buy, the minimum amount you will accept (a hard limit price), and an expiry. You sign that as EIP-712 typed data. Signing costs nothing, and nothing touches the chain yet: the order sits in an off-chain orderbook.
Execution is someone else’s job. Competing solvers pick up open orders, race each other on price, and the winner settles a whole batch of orders in one on-chain transaction. Ophis is a fork of CoW Protocol’s frontend with a natural-language intent layer and an agent stack, and settlement uses CoW Protocol’s GPv2 design, with Ophis-operated deployments on Optimism, Unichain, Robinhood Chain and Arc. The solver builds the settlement transaction, broadcasts it, and pays its gas.
Note that this is different from gas sponsorship. Sponsorship models (relayers, paymasters) still construct a transaction for you and have a third party pay for it, usually charging the cost back somewhere else. In an intent there is no user transaction to sponsor: the only on-chain transaction is the solver’s batch settlement, which would exist anyway.
The same structure is what makes the flow MEV-protected. Orders travel offchain and clear at a uniform price per token pair. This mitigates common MEV, but the solver’s settlement can still be public and use external pools.
The fee comes out of the trade, not your gas balance
Ophis uses chain-aware pricing. The standard schedule charges a 1 bp base plus capped reference-quote-improvement capture; hosted chains additionally apply CoW Protocol fees upstream. Fees are taken from the trade rather than billed in native gas (the full fee schedule is public; on the chains that settle through CoW Protocol, CoW Protocol’s protocol fee applies on top of the Ophis fee). On a standard sell order that is the token you receive: sell USDC for ETH and the fee is a slice of the ETH. On a buy order, where you name the amount you want to receive, it comes off the token you spend instead. For standard ERC-20 orders, you do not broadcast or directly pay gas for the solver’s settlement. Arc exposes one USDC balance through 18-decimal native and six-decimal ERC-20 interfaces; selling USDC reduces what remains for gas.
The limit you signed still bounds the outcome. Solvers compete to beat the reference quote. Under that standard schedule, Ophis retains 80% of that improvement on volatile pairs (99 bps cap) or 50% on stable pairs (20 bps cap); the trader receives the remainder and everything above the cap. Hosted chains additionally apply CoW Protocol’s upstream fees.
Unfilled signed orders have no settlement fee
A failed on-chain swap still burns gas: you paid the network to execute your revert. A signed order has no equivalent failure cost. If no solver can meet your limit price before the order’s expiry, the signed ERC-20 order expires without a settlement fee. The unsold tokens remain in your wallet, where their market value can still change. Approval or cancellation transactions have separate gas costs.
Where gas can still appear
An ERC-20 sell needs sufficient allowance to the chain’s vault relayer, not an approval to the settlement contract. Resolve that spender through the SDK or app configuration. Approval transactions cost gas; an exact allowance may need renewing after it is consumed. Some tokens and wallets support permits.
Native-token placement through EthFlow, wrapping, hard cancellation, refunds and direct bridge or conversion transactions can also require gas. Native-token orders deposit funds before settlement and need a separate refund if unfilled. This article’s gasless flow is the standard signed ERC-20 order.
Who actually hits the gas wall
New wallets. On most chains, ERC-20 tokens alone do not cover approval gas. A wallet needs an existing allowance or a supported permit flow before gasless signing can help. Once that requirement is met, the solver pays settlement gas.
AI agents. Signed orders remove the need to fund settlement transactions, not all wallet operations. Keep gas available for approvals and other required transactions; the integration pattern is in how to let an AI agent swap tokens.
Multichain traders. The Ophis app supports 14 chains: Ethereum, Optimism, BNB, Gnosis, Unichain, Robinhood Chain, Polygon, Base, Plasma, Arbitrum, Avalanche, Ink, Linea, and Arc. SDK v0.4.3 and the hosted MCP server also include Arc. They do not all share one gas token. Pre-funding a native balance on every chain you might trade on is dead capital and real friction; signed orders remove settlement-gas payment by the trader, not approval or other transaction gas.
FAQ
Do I need ETH to swap?
For a standard signed ERC-20 order, the solver pays settlement gas and the fee comes out of the trade. Approvals, native-token placement, wrapping, hard cancellation, refunds and direct bridge transactions can still require gas.
What if the price moves while my order is open?
Your order carries a hard limit price that you signed, and it cannot settle below that price. If the market never reaches your limit before expiry, the signed ERC-20 order expires without a settlement fee. If the market moves in your favor, solvers still compete for the fill, and improvement beyond the reference quote is shared under the operated-chain capped policy or the hosted CoW policy.
Who pays the solver?
The winning solver pays the gas for the settlement transaction. The trading fee follows the current chain-aware schedule and is taken from the trade; the limit price you signed bounds the outcome either way. Solver compensation is never billed to you in the native token.
Is it custodial?
For standard signed ERC-20 orders, tokens stay in your wallet until the batch that includes your order settles, and they can move only under the allowance you granted and against an order you signed (EIP-712 from a regular wallet, ERC-1271 from a smart-contract wallet). Native-token orders and bridges can require deposits with separate recovery rules. See the FAQ docs.
Try a signed ERC-20 swap
Open swap.ophis.fi, connect a wallet that holds any ERC-20 on a supported chain, and sign an order. You need sufficient allowance to the vault relayer; approval transactions can cost gas and an exact allowance may need renewing. The getting started guide covers the rest.