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Transaction Reverts

When a transaction fails on the blockchain, it often provides a revert reason. Here are common ones in SwapX.

"TransferHelper: TRANSFER_FROM_FAILED"​

Context: V2 Router, V3 Router, Position Manager Cause:

  1. Allowance: You haven't approved the contract to spend your tokens.
  2. Balance: You don't have enough tokens in your wallet.
  3. Token Logic: The token has a fee on transfer or behaves non-standardly (e.g., USDT on some chains requires reset approval to 0 first).

Fix: Check your token balance and allowances.

"UniswapV2: K" (or "SwapX: K")​

Context: V2 Swaps Cause: The constant product invariant check failed. Usually happens if someone manipulates the pool reserves during your transaction or if there's a logic error in fee calculation. Fix: Usually not user-fixable unless you are interacting directly with the Pair. Ensure you are using the Router.

"STF" (Safe Transfer Failed)​

Context: V3 Pools Cause: Similar to TRANSFER_FROM_FAILED. The pool failed to pull tokens from you or push tokens to you. Fix: Check balances and allowances.

"Old" or "Expired"​

Context: Routers Cause: The deadline parameter you sent is in the past. Fix: Set deadline to Math.floor(Date.now() / 1000) + X where X is seconds in the future.