UniswapX

UniswapX is an ERC20 swap settlement protocol that provides swappers with a gasless experience, MEV protection, and access to arbitrary liquidity sources. Swappers generate signed orders which specify the specification of their swap, and fillers compete using arbitrary fill strategies to satisfy these orders.

UniswapX Protocol Architecture

Reactors

Order Reactors settle UniswapX orders. They are responsible for validating orders of a specific type, resolving them into inputs and outputs, and executing them against the filler's strategy, and verifying that the order was successfully fulfilled.

Reactors process orders using the following steps:

• Validate the order
• Resolve the order into inputs and outputs
• Pull input tokens from the swapper to the fillContract using permit2 permitWitnessTransferFrom with the order as witness
• Call reactorCallback on the fillContract
• Transfer output tokens from the fillContract to the output recipients

Reactors implement the IReactor interface which abstracts the specifics of the order specification. This allows for different reactor implementations with different order formats to be used with the same interface, allowing for shared infrastructure and easy extension by fillers.

Current reactor implementations:

• LimitOrderReactor: A reactor that settles simple static limit orders
• DutchOrderReactor: A reactor that settles linear-decay dutch orders
• ExclusiveDutchOrderReactor: A reactor that settles linear-decay dutch orders with a period of exclusivity before decay begins

Fill Contracts

Order fillContracts fill UniswapX orders. They specify the filler's strategy for fulfilling orders and are called by the reactor with reactorCallback when using executeWithCallback or executeBatchWithCallback.

Some sample fillContract implementations are provided in this repository:

• SwapRouter02Executor: A fillContract that uses UniswapV2 and UniswapV3 via the SwapRouter02 router

Direct Fill

If a filler wants to simply fill orders using funds held by an address rather than using a fillContract strategy, they can do so gas efficiently by using execute or executeBatch. These functions cause the reactor to skip the reactorCallback and simply pull tokens from the filler using msg.sender.

Integrating with UniswapX

Jump to the docs for Creating a Filler Integration.

Deployment Addresses

Ethereum Mainnet

Contract	Address	Source
V2 Dutch Order Reactor	0x00000011F84B9aa48e5f8aA8B9897600006289Be	V2DutchOrderReactor
Exclusive Dutch Order Reactor	0x6000da47483062A0D734Ba3dc7576Ce6A0B645C4	ExclusiveDutchOrderReactor
OrderQuoter	0x54539967a06Fc0E3C3ED0ee320Eb67362D13C5fF	OrderQuoter
Permit2	0x000000000022D473030F116dDEE9F6B43aC78BA3	Permit2

Base

Contract	Address	Source
Priority Order Reactor	0x000000001Ec5656dcdB24D90DFa42742738De729	PriorityOrderReactor
OrderQuoter	0x88440407634f89873c5d9439987ac4be9725fea8	OrderQuoter
Permit2	0x000000000022D473030F116dDEE9F6B43aC78BA3	Permit2

Tempo

Contract	Address	Source
V3 Dutch Order Reactor	0x00000000fc1E66C9f582566EAd00108e55F1c0C6	V3DutchOrderReactor
OrderQuoter	0x00000000a3db63Df9078cBF3dF88B4CAdD5a7F58	OrderQuoter
Permit2	0x000000000022D473030F116dDEE9F6B43aC78BA3	Permit2

Both V3DutchOrderReactor and OrderQuoter were deployed via the canonical Arachnid CREATE2 factory (0x4e59b44847b379578588920cA78FbF26c0B4956C) using salts mined with create2crunch — the reactor address has 4 leading zero bytes (5 total) and the quoter has 4 leading zero bytes, saving ~12 gas per zero byte each time those addresses are encoded in calldata.

Deployment notes

UniswapX is being deployed on Tempo (chainId 4217) via V3DutchOrderReactor. Tempo has several EVM-level quirks that integrators and fillers must understand before building or running orders against it:

• ERC20-only — no native token. Tempo has no native gas token. Orders MUST NOT use the NATIVE sentinel address (address(0)) for either the input token or any output token. Both swappers and fillers are expected to operate strictly in ERC20s.
• CALLVALUE / BALANCE / SELFBALANCE always return 0. The payable modifier on reactor entry points (execute, executeBatch, executeWithCallback, executeBatchWithCallback) is a no-op on Tempo because no value can ever be transferred. The leftover-balance refund branch in BaseReactor.sol:126 (the address(this).balance > 0 refund path) is dead code on Tempo — it is harmless but will never execute.
• block.basefee is a constant. On Tempo, block.basefee is fixed at approximately 2e10 in attodollars per gas (note: attodollars, not wei). The V3 gas-adjustment math in _updateWithGasAdjustment remains internally consistent as long as the cosigner sets startingBaseFee = block.basefee and adjustmentPerGweiBaseFee = 0. Setting adjustmentPerGweiBaseFee = 0 makes the gas adjustment unambiguously a no-op and is the recommended cosigner configuration for V3 orders on Tempo.
• block.number is a standard monotonic counter. BlockNumberish.sol requires no changes for Tempo. Block time is roughly 500ms.
• Sample executors are ERC20-only on Tempo. The sample fillers in this repo — UniversalRouterExecutor, SwapRouter02Executor, and MultiFillerSwapRouter02Executor — perform native sweeps via address(this).balance. Those sweep paths are inert on Tempo (the balance is always 0). PMMs and other fillers building executors for Tempo MUST implement ERC20-balance-based sweeps instead of relying on native-balance logic.

The canonical Permit2 (0x000000000022D473030F116dDEE9F6B43aC78BA3) is deployed on Tempo, and V3DutchOrderReactor binds to it via script/DeployDutchV3.s.sol. See that script's header comment for deploy invocation details.

Usage

# install dependencies
forge install

# compile contracts
forge build

# run unit tests
forge test

# run integration tests
FOUNDRY_PROFILE=integration forge test

Fee-on-Transfer Disclaimer

Note that UniswapX handles fee-on-transfer tokens by transferring the amount specified to the recipient. This means that the actual amount received by the recipient will be after fees.

Version Log

Version Number	Commit	Contract Address
1.0	597cf617dd6d32b3f181edbc37aed11bc5648d93	Contract no longer in use. Read more about the bug here.
1.1	cf53fc7dd48029a9189d26812d676a4ea9d08d6c	0x6000da47483062A0D734Ba3dc7576Ce6A0B645C4
2.0	4bacf632512ec5c9504a78ad1b7e1aec7efc6767	0x00000011f84b9aa48e5f8aa8b9897600006289be

Audit

V1

• ABDK

V1.1

• ABDK
• OpenZeppelin

V2

• Spearbit

Bug Bounty

This repository is subject to the Uniswap Labs Bug Bounty program, per the terms defined here.