min_lock_amount is the smallest deposit, after any source swap, that still belongs to the quote. min_amount_out is the least the recipient is paid. A deposit between min_lock_amount and expected_lock_amount is paid in proportion to what arrived, and never less than min_amount_out.
Setting slippage
When you set
slippage_bps, min_amount_out is exactly amount_out less that many basis points. The same budget is split between the two legs in proportion to their market slippage: the tier of src_token and lock_token on the source side, and the tier of the bridged token and dst_token plus any gas surge allowance on the destination side. min_lock_amount is set so that a deposit at the source floor still leaves the destination its share, which keeps every accepted deposit at or above min_amount_out once paid in proportion. A direct deposit, where src_token is lock_token, has no source share: it must arrive in full, and the whole budget goes to the destination. src_slippage_bps is ignored, and the quote returns your slippage_bps as sent.
Omit slippage_bps and the operator applies a tier appropriate to the pair and size on each leg, with src_slippage_bps replacing the source tier when you set it. The quote then returns the actual gap between amount_out and min_amount_out as slippage_bps, so read it from the response. On an expected-output quote the omitted default is 50 bps on both legs instead of the tier.
Where the floors are enforced
min_lock_amount is checked on the source chain. On a source swap the router runs the aggregator call and reverts with InsufficientOutput if the swap returns less, so the user’s funds never leave their wallet on a failed deposit. A direct deposit below min_lock_amount does not belong to the quote and is refunded.
min_amount_out is checked on the destination chain, inside the fulfillment. If the destination swap cannot clear the floor, the fulfillment does not land, and after the attempt limit the order routes to refund rather than delivering less than promised.
Surplus above a floor stays in the vault; it is not delivered to the recipient and not returned to the sender.
Choosing a value
Wider slippage does not cost anything when the market cooperates: the floor is a limit, not a price. It costs when it is too tight, because the deposit reverts or the order refunds, and the user pays gas for nothing either way.For stable-to-stable transfers of the same asset there is no swap leg on either side. The deposit must arrive in full, and the gap between
amount_out and min_amount_out is room for a gas surge on the destination, deducted only if gas spikes between the quote and the fulfillment.Reading the result
min_amount_out next to amount_out in a confirmation screen. It is the number the protocol guarantees; amount_out is the number it expects.