LayerZero OFT

@mavna/adapter-layerzero, adapter id layerzero, trust model dvn-stack. A token that implements LayerZero's OFT standard moves by message, and a set of verifiers (Decentralized Verifier Networks, DVNs) attests each message. The token's owner chooses that set, so two tokens on this rail can be verified by different parties. On Stellar's main network it carries USDT0.

const layerzero = new LayerZeroAdapter({ network, rpc, baseReserveStroops });

Assets and chainsCopy Anchor Link

On the main network the adapter sends USDT0 from 12 chains. Each chain is only a candidate: every quote reads the chain's endpoint, its OFT contract, the OFT's peer on Stellar and its verifier set, and declines when any of them is missing.

sendableAssets(chainId) answers which assets a quote request names, read from the deployment:

const { from, to } = await layerzero.sendableAssets("arbitrum");
// to.id is "USDT0:GATISXX6BZ6NC7IKQBY37CJD4SOZL3CYZJWXEDG6JVIY4WBS6KXJHN6Q" on mainnet

RecipientsCopy Anchor Link

A route delivers to an account or a contract address. The message carries the recipient as 32 bytes, which is an account key or a contract id, so a muxed address, whose id does not fit, is declined before the quote.

Who verifiesCopy Anchor Link

The adapter refuses two kinds of verifier set: one with no verifier required, and one the token's owner never set, inherited from LayerZero's defaults, which can change without the owner acting. Every send it builds says in its description which verifiers attest it, how many of them must agree, and after how many source-chain confirmations.

Checks on every quoteCopy Anchor Link

• The Stellar OFT is asked which endpoint it is registered on, and the adapter refuses to send when that is not the current endpoint, so a transfer never goes to a superseded deployment.
• The sending OFT's peer for Stellar must be set, and the Stellar side must accept messages from it.
• The Stellar OFT must not be paused, and its inbound limit must have room for the amount.
• The amount must be within the limits the sending OFT's quoteOFT reports.

ApprovalsCopy Anchor Link

Where the source OFT holds the token rather than burning it, as for USDT0 on Ethereum, the build returns three transactions: an approval of zero, an approval of exactly the amount, and the send. USDT refuses to change one non-zero allowance to another, so the reset to zero comes first. It carries skipAlsoWhenExactly: "0", and the approval carries the amount as atLeastBaseUnits, so a caller sends the reset only when an allowance sits between zero and the amount, and neither when the allowance already covers it. Where the OFT burns the token, the build is the send alone.

The feeCopy Anchor Link

LayerZero's fee is paid in the source chain's own currency, on top of the amount. The quote shows the fee quoteSend returns. The build prices it again and attaches a tenth more as the call's value; LayerZero's endpoint refunds whatever is not needed to the sending wallet, and the send's description states the most it attaches.

The minimumCopy Anchor Link

What arrives can be less than what is sent, because a token can take a fee in transit. The sender's minimum is enforced on-chain through minAmountLD, derived from their slippage, so receivesAtLeast is a real floor.

Converting on arrivalCopy Anchor Link

Given an Arrival Contract, the adapter also quotes a second route for the same send: delivered to the Arrival Contract with a message that names the recipient, the asset wanted and the least they accept. The contract converts on Stellar and sends the result on; the route adds no step and no signature.

A route that converts on arrival is declined, with the reason, for a recipient that cannot hold the wanted asset or the arriving token, and for a new account, which is left to the plain route. An integrator fee from 0 to 1000 basis points is taken only on these routes, by the contract, from the converted amount.