Most bridges make the user wait while a validator set confirms a transfer. Across makes a professional relayer front the money instantly and take the waiting risk themselves, in exchange for a fee. For the user the transfer settles in seconds; for the relayer it is a financing business.
How settlement actually works
Relayers fill user requests on the destination chain from their own inventory. Periodically they submit a bundle claiming reimbursement from the shared liquidity pool. That claim is subject to UMA's optimistic oracle: it is assumed valid unless disputed within a challenge window, with economic penalties for false claims and false disputes. There is no custom validator set holding your funds.
Why this is a better risk profile
The user is never exposed to a locked collateral pool being drained mid-transfer, because the funds arrive before settlement occurs. The residual risks are the correctness of the optimistic oracle's dispute mechanism and the solvency of the shared pool, both of which are bounded and inspectable.
Costs and coverage
Fees typically run 0.05% to 0.2% depending on route and size, which is competitive, plus gas. Coverage is EVM chains — Ethereum, its major L2s and several sidechains — with no support for Solana or non-EVM ecosystems.
Who should use it
Anyone moving assets between EVM chains, particularly between L2s where speed matters. It is one of the two or three bridges we would use without hesitation.