Revert Reasons

UniswapX reactors revert with typed Solidity errors, which can be difficult to decode from a raw transaction receipt. Before submitting a fill transaction, fillers should use the OrderQuoter contract (or the UniswapX SDK wrapper) to simulate the fill and decode the revert reason — this avoids wasted gas and helps attribute failures to the right party.

Order Validation States

The OrderValidation enum in the SDK captures every meaningful validation outcome. The table below describes each state and who is responsible for resolving it.

State	Meaning	Who's Responsible
OK	Order is valid and fillable.	—
Expired	Order deadline has passed.	Filler (timing)
NonceUsed	Order nonce already consumed — order was filled or cancelled.	Protocol / Filler
InsufficientFunds	Swapper wallet lacks sufficient token balance or approval.	Swapper (surface to user)
InvalidSignature	Order signature is invalid or doesn't match the swapper.	Protocol
InvalidOrderFields	One or more order fields are malformed (bad decay times, amounts, reactor address, etc.).	Protocol / Filler
ValidationFailed	External validation contract rejected the order (often exclusivity).	Filler
ExclusivityPeriod	Order is in its exclusivity window and the caller is not the exclusive filler.	Filler (timing / routing)
OrderNotFillableYet	Order's start time hasn't been reached (Priority orders).	Filler (timing)
InvalidGasPrice	Gas price doesn't meet the order's requirements (Priority orders).	Filler
InvalidCosignature	Cosigner signature is missing or invalid (Cosigned orders).	Protocol / Filler
UnknownError	Unrecognized revert — check raw revert data.	—

Error Selector Reference

The table below maps 4-byte error selectors to their corresponding OrderValidation state. Use this as a lookup when decoding raw revert data from the reactor.

Selector	State	Source
8baa579f	InvalidSignature	—
815e1d64	InvalidSignature	—
756688fe	NonceUsed	—
302e5b7c	InvalidOrderFields	Invalid dutch decay time
773a6187	InvalidOrderFields	Invalid dutch decay time
4ddf4a64	InvalidOrderFields	Invalid reactor address
d303758b	InvalidOrderFields	Both input and output decay
7c1f8113	InvalidOrderFields	Incorrect amounts
43133453	InvalidOrderFields	Invalid dutch decay time
48fee69c	InvalidOrderFields	—
70f65caa	Expired	—
ee3b3d4b	NonceUsed	—
0a0b0d79	ValidationFailed / ExclusivityPeriod	Exclusive filler check — maps to ExclusivityPeriod when additionalValidationData encodes an exclusive filler
b9ec1e96	ExclusivityPeriod	—
062dec56	ExclusivityPeriod	—
75c1bb14	ExclusivityPeriod	—
a305df82	InvalidOrderFields	Invalid cosigner output
ac9143e7	InvalidOrderFields	Invalid cosigner input
fff08303	InvalidOrderFields	Duplicate fee output
d7815be1	InvalidCosignature	InvalidCosignature()
TRANSFER_FROM_FAILED	InsufficientFunds	ERC-20 transfer failure
d856fc5a	InvalidOrderFields	Invalid fee escalation amounts
cd21db4f	Expired	Signature expired
769d11e4	Expired	PriorityOrderReactor: InvalidDeadline()
c6035520	OrderNotFillableYet	PriorityOrderReactor: OrderNotFillable()
a6b844f5	InvalidOrderFields	PriorityOrderReactor: InputOutputScaling()
f3eb44e5	InvalidGasPrice	PriorityOrderReactor: InvalidGasPrice()

Using the SDK to Pre-flight Orders

The UniswapX SDK's OrderQuoter class wraps the on-chain quoter contract and decodes the revert reason into the OrderValidation enum. Call it before sending your fill transaction to avoid wasted gas:

import { OrderQuoter, OrderValidation } from '@uniswap/uniswapx-sdk';

const quoter = new OrderQuoter(provider, chainId);
const { validation } = await quoter.validate({ order, signature });

if (validation !== OrderValidation.OK) {
  console.error('Order invalid:', OrderValidation[validation]);
}

Running this simulation before submission lets you skip unwinnable fills, surface InsufficientFunds errors to your UI, and distinguish timing issues (e.g. ExclusivityPeriod) from permanent failures (e.g. InvalidSignature).

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For broader context on building a fill bot — including order polling, execution flow, and webhook registration — see the Filler Integration Guide.