When Should You Reprice a Fast Swap?

Reprice a fast swap when the route’s current state no longer supports the quoted output or the transaction’s execution limits. A quote is a calculation against market state at a particular moment; the transaction is checked against state when it executes. Its age is a clue to check, not proof that the price is wrong.

For an aggregator, a quote may combine pool prices, route selection, fees and an estimated output. Before signing, compare the refreshed quote with the one you reviewed, including its minimum output and route. A better price may come from a changed route; a worse one may reflect price movement, liquidity or a different fee estimate. The linked paraswap guide covers how to diagnose a swap that remains pending or fails. That distinction matters before deciding whether to request another quote or submit anything again.

What makes a swap quote stale?

A quote is stale when the market state or execution assumptions used to produce it have changed enough that its expected result no longer describes the transaction you intend to send. On an automated market maker, trades change pool reserves, which changes the price available to the next trade. Other transactions can alter the same pools between a quote and execution; a route spanning several pools can be affected at any hop.

Elapsed time alone does not determine freshness. A quote can remain usable across a quiet interval if relevant pool state and route assumptions have not changed. A quote can become unusable within a short interval if another trade moves the price or consumes liquidity. Block progression can be a useful signal to refresh, but there is no universal age threshold that makes every quote invalid.

Also separate the quoted output from the amount the transaction is allowed to receive. A router often enforces a minimum output, derived from the quoted amount and the user’s slippage tolerance. Slippage tolerance is the permitted shortfall between expected and minimum output. If execution would fall below that minimum, the router reverts instead of completing the swap. A wider tolerance can let a transaction execute after more price movement, but it also permits a worse result.

Which changes justify requesting a new quote?

Request a new quote before signing when the refreshed route or output changes the trade you are willing to make. A new quote can reveal that the original route has lost liquidity, that another route now offers a better result, or that the original minimum output no longer fits the current market. Repricing is a decision point: check the amount you will receive, the route, the fees and the execution limits together.

• The expected output moved. Compare the refreshed output with the original and decide whether the difference is acceptable for the trade size.
• The route changed. Check which pools or venues the new path uses, since a different path can change both price and execution risk.
• The minimum output is no longer acceptable. Do not loosen the limit automatically just to make a transaction more likely to execute.
• The transaction assumptions changed. Refresh if the quote’s gas estimate, fee assumptions or validity window no longer match what your wallet is about to submit.

A quote refresh is most useful before signing, while you can still inspect the transaction. If the refreshed quote is worse, the practical choice may be to wait, reduce the trade size or abandon the swap. Splitting a large trade can reduce its effect on pool price, but it can add transaction and network fees; compare the total cost rather than looking only at the quoted rate.

What should you do if the swap is already pending?

A pending transaction has already been broadcast, so a fresh quote does not replace it. Its eventual execution depends on the transaction’s encoded limits and the state available when a block includes it. If the route still satisfies the minimum output and any deadline, it may execute; if not, it may revert. The wallet’s pending label describes transaction status, not whether the quoted price remains available.

Do not submit a second swap merely because the first one is taking time. If both transactions execute, you may trade twice. First check the original transaction’s status and its limits. If it is still pending and you intend to replace or cancel it, wallet and network behavior matters: replacement typically involves a transaction using the same account nonce, and a cancellation can fail if the original is included first. A failed transaction, by contrast, has been included but reverted; its state change did not complete, though network fees may still be charged.

For a trade you have not signed, refresh when the route or output has moved enough to change your decision, then review the limits before submitting. For a trade already in flight, inspect that transaction before acting on a new quote. That keeps repricing tied to the actual execution state and avoids turning one uncertain swap into two.