Learn · Execution

Why swap quotes expire and transactions fail

Written by XAUConnect Labs · Reviewed against live product behavior · Updated August 2026

Quotes are photographs of a pool at a moment in time. Blocks keep happening. If you treat a quote like a limit you already own, you will sign a transaction that reverts, and on EVM you will still pay gas. This is the troubleshooting manual we wanted when “Transaction failed” was the entire error string.

It covers stale quotes, slippage too tight, insufficient allowance, wrong chain, fee-on-transfer tokens, and what to do — in order — so you do not double-submit.

Why quotes go stale

Every swap in that pool, and every sandwich bot watching the mempool, can move price before your transaction is included. Aggregator quotes also depend on third-party APIs that cache for a second or two. Thirty seconds of hesitation on a meme pair is a different market.

Read the revert before you retry

Open the failed hash on the explorer. `STF` / transfer-from failures often mean allowance or a fee-on-transfer token. `Too little received` / slippage errors mean the floor was missed — raise slippage a notch or cut size, do not jump to 12%. Out-of-gas means the estimate was wrong; bump the gas limit, not the priority fee first. If the explorer shows the tx as pending, do not send a second copy with the same nonce intent until you know whether the first will land. Double-sends on Ethereum create nonce queues.

Allowance and the “it worked in the UI” bug

The website can show a quote while your allowance is still for a previous spender. After we rotate routers or you last traded on another aggregator, approve again. Check `GET /swap/allowance` if you are a bot. Humans: look for a second “Approve” button instead of assuming the first swap pop-up is the swap.

Fee-on-transfer and rebasing tokens

Some tokens tax every transfer. A router that assumes it received amount X actually received X minus tax, then the minimum-received check fails. Those tokens need specialized routes or they are simply not worth integrating. If simulation fails only for one token, suspect the token, not Ethereum.

A recovery order that wastes less gas

1) Confirm chain. 2) Re-quote. 3) Cut size in half. 4) Nudge slippage 0.1–0.3% at a time. 5) Check allowance. 6) Try a more liquid output (native USDC) as an intermediate via a two-hop you actually understand. 7) Stop. Going to 5% slippage on a public mempool is how you donate to MEV.

Pending vs failed vs dropped

Pending means the nonce is in the mempool — wait or replace, do not duplicate. Failed/reverted means it landed and undid the swap; gas is gone on EVM. Dropped means it never landed; you can resend. Wallets blur these three. The explorer does not. If you are unsure, paste the hash before you tap anything else. That one habit prevents more lost gas than any slippage preset.

Legal

Risk disclosure

XAUConnect is a non-custodial swap aggregator. Digital assets are volatile and may lose value rapidly. Content on this page is educational and not investment advice. Verify every contract address on the official block explorer before approving a transaction.

Frequently asked questions

Did XAUConnect take a fee on the failed tx?

No platform fee on a reverted swap. You may still have paid network gas on EVM.

The wallet said success but I do not see tokens

Wrong token list, wrong chain view, or you received a wrapped/bridged variant. Check the explorer transfer logs, not the wallet’s favourite tokens.

Can I speed up a pending swap?

Use the wallet’s speed-up/replace if it supports the same nonce with higher fees. Do not build a brand-new swap from the site in parallel unless you know what you are doing.

Solana failed with a simulation error

Usually blockhash expired or slippage. Re-quote and sign quickly; Solana blockhashes are short-lived. Add a modest priority fee during congestion.

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