1inch Fusion relies on resolvers to fill swaps within Dutch auction terms

A resolver fill requires valid funding and authorization

An executable Fusion order needs valid authorization, sufficient funding, and auction terms that a resolver can satisfy on the selected network. The preparation differs between ordinary off-chain token orders and orders that require an on-chain deposit.

Balance and spending permission

On Ethereum Virtual Machine (EVM) networks, ordinary ERC-20 orders require sufficient token balance and permission for the contract that spends it. An existing allowance can cover that requirement. Supported token permit signatures can authorize spending without a separate approval transaction. Permit2 requires a token allowance to its contract, so an initial approval can still cost gas. Without a suitable allowance or usable permit, an on-chain approval costs gas. An approval permits spending, while the order signature authorizes particular exchange terms. Spending tokens or reducing the necessary allowance before settlement can prevent the resolver from filling the order.

Submission and settlement records

The ordinary EVM token flow uses an off-chain signed order that a relayer makes available to resolvers. Solana Fusion publishes the intent on-chain, locks the input in escrow, and requires a network fee in SOL at creation. Its creation transaction establishes the order, while a subsequent resolver fill establishes the exchange. Order status and confirmed fill transactions distinguish the initial submission from partial or full execution. The amounts that the receiving address actually obtains determine the settled return.

Auction terms connect your return to resolver economics

The Dutch auction can initially require a higher output for the maker, the user who creates the order.

The changing output requirement

For a fixed input amount, the auction generally lowers the required output toward the order's minimum return. The resolver evaluates the tokens that it must deliver against available liquidity and execution costs. Filling earlier can secure an opportunity before another resolver takes it. Waiting can improve the economics for the resolver, although market movement can remove that opportunity. The EVM settlement calculation also adjusts the auction rate using the current base fee and the order's gas estimates.

Eligible resolvers and execution windows

EVM settlement checks who may fill an order at the relevant time. The contract supports per-order resolver access windows and access-token checks outside the order's whitelist. Fusion's governance-dependent whitelisting, farming, and Unicorn Power-based eligibility or exclusivity are currently disabled under 1IP-89. Current resolver onboarding requires identity or business verification, a compliance survey, and access NFTs. This keeps a valid signature from implying that any address can immediately execute the trade. Auction presets carry their own duration, output amounts, and curve parameters. A preset's speed preference cannot compel a resolver to complete an uneconomic fill.

Gasless execution still has a price

Fusion's gasless token-order flow shifts the settlement transaction fee to the resolver, whose execution costs influence the exchange economics. For an ordinary off-chain EVM Fusion order, the resolver pays the gas for the fill transaction. The quote can therefore reflect gas costs without requiring the maker to submit that transaction.

Available liquidity, trade size, and network gas conditions influence the output that resolvers can economically deliver. Matching orders or batching execution can reduce their costs. Fee-enabled EVM settlement can also include integrator fees, protocol fees, and a configured share of positive surplus. These charges depend on the order and its integration. An auction amount or estimated surplus does not establish the amount that reaches the recipient after applicable fees.

Separate preparation costs remain relevant. A required token approval consumes gas. The native-input EVM factory flow uses a funded on-chain creation transaction. Solana intent creation also requires a network fee, even when the auction later produces no fill.

View image file

Partial fills exchange portions under the same order

A partial fill exchanges only a portion of the requested input, with corresponding output under that portion's execution terms. EVM orders have separate settings for partial-fill permission and multiple-fill permission. Allowing multiple fills lets eligible resolvers continue filling the remainder while the order stays valid. Each fill reduces the remaining input that future fills can consume. Different portions can settle at different points on the auction curve, so their effective rates can differ. A partially filled status therefore needs its executed amounts and remaining amount to explain how much of the intended swap has completed.

View image file

Intent settlement changes exposure to transaction ordering

Off-chain EVM Fusion orders avoid the maker's publicly pending swap transaction that can expose a conventional market swap to front-running or sandwich attacks. Resolvers handle execution under the signed order's constraints, and the architecture provides MEV protection. MEV means maximal extractable value and includes gains from transaction ordering. That protection does not guarantee the auction's opening rate or eliminate the influence of changing market liquidity on whether a fill becomes viable.

The signature still authorizes a real exchange. The input asset, output asset, receiving address, and applicable terms belong to that authorization. The contract enforces the authorized terms, including an incorrect asset or recipient that the maker accepted.

Expiry and cancellation govern the unfilled remainder

An order's expiry stops further execution once its validity deadline passes, even when a resolver might otherwise find profitable liquidity. For an ordinary wallet-funded ERC-20 order, the unspent input remains in the wallet. Insufficient balance, insufficient allowance, or an invalid permit can prevent execution before expiry. A fresh quote can reflect different liquidity and gas conditions, so submitting another order creates a new set of terms.

Expiration does not undo a portion that has already settled.

The EVM Limit Order Protocol supports on-chain cancellation, which requires a transaction and its associated gas. A cancellation can stop future fills, while a fill that confirms beforehand remains completed. Checking the existing order's terminal status and executed amounts avoids treating an active remainder as a fresh full-size swap.

Escrow-funded orders require their own cancellation or cleanup mechanism to release remaining funds. On Solana, the maker can cancel through an on-chain instruction that closes the escrow and returns the remaining input. After expiry, a resolver can also cancel; the order parameters determine any cancellation premium. The EVM native-input extension, NativeOrderFactory, lets the original maker cancel and recover the remaining native funds. Eligible resolvers can also clean up expired orders. When a resolver requests compensation, cleanup must wait for the configured delay after expiry, and capped gas compensation comes from the remaining funds.