lifinance/lifi-stablecoin-swap

Build a 1:1 Stablecoin Swap with LI.FI Intents

A normal crypto transfer leaks value to gas and spreads — send 100 USDC, ~99.8 arrives. For a neobank, payment processor, or regulated fintech, that's a non-starter: their users expect that sending 100 means 100 arrives.

LI.FI Intents lets you offer exactly that — send 100 USDC, receive 100 USDC (or USDT, or another supported stablecoin), same-chain or cross-chain. A solver from LI.FI's network fronts the destination gas and sources the liquidity, then settles against the user's deposit, so the end user sees one number from start to finish, provable on a public block explorer.

The primary integration is the @lifi/intent TypeScript SDK — it requests the quote, builds the on-chain order, and tracks it. The raw REST API is in §7 for non-TypeScript backends.

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1. Enable 1:1 quoting on your integrator account

1:1 stablecoin quoting is a capability provisioned on your LI.FI integrator account:

1. Register an integrator ID on the LI.FI Partner Portal — https://portal.li.fi
2. Complete an integration agreement with LI.FI. As part of onboarding, 1:1 stablecoin quoting is enabled for your integrator.
3. Quote requests made under your integrator key then return 1:1 amounts for supported stablecoin pairs.

The integration code below is identical regardless — what makes the quote come back 1:1 is your onboarded integrator. See https://docs.li.fi/lifi-intents/introduction or contact LI.FI to enable it.

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2. The flow

order.li.fi is the Intents API. The escrow flow is the recommended default and takes four steps:

1. Quote     getQuotes(...)                              -> guaranteed output amount (1:1)
2. Approve   ERC-20 approve(InputSettlerEscrow, amount)  -> let the settler pull the input token
3. Open      escrow.open(StandardOrder) on-chain         -> locks funds, emits Open(orderId)
4. Track     GET /orders/status?onChainOrderId=...         -> Signed -> Delivered -> Settled

Opening the order emits Open(bytes32 indexed orderId, ...); solvers watch for that event and fill on the destination chain, so the escrow flow needs no order-submission call. You poll status until the funds land, then show the user the destination transaction. The orderId is the receipt — anyone can independently verify the deposit and the delivery matched.

(There is also a Compact / gasless flow — deposit once into The Compact, then sign and submit each order off-chain. Use escrow unless you specifically want gasless after a one-time deposit.)

npm install @lifi/intent viem

(The runnable interface in the quickstart also uses wagmi + @tanstack/react-query for the wallet — its install line includes them.)

Setup note: the SDK uses bigint literals (100_000_000n). create-next-app defaults tsconfig.json to "target": "ES2017", which rejects them — set "target": "ES2020" (or higher).

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3. Quote (1:1)

getQuotes with your integrator key. IntentApi(true) targets mainnet / the production solver network. Amounts are bigint in the token's smallest units (100 USDC = 100_000_000n, 6 decimals). Under a 1:1-enabled integrator on a supported stablecoin pair, the output equals the input.

import { IntentApi } from "@lifi/intent";

const api = new IntentApi(true);

const res = await api.getQuotes({
  user,                                              // the user's 0x address
  userChainId: 8453,                                 // source chain (Base)
  integratorKey: process.env.LIFI_INTEGRATOR_KEY,    // your onboarded integrator key
  inputs:  [{ sender: user,   asset: usdcOnBase, chainId: 8453,  amount: 100_000_000n }],
  outputs: [{ receiver: user, asset: usdcOnArb,  chainId: 42161, amount: 0n }],
});

const quote = res.quotes[0];
if (!quote) throw new Error("No quote available for this pair");
const received = BigInt(quote.preview.outputs[0].amount); // == 100_000_000n for a 1:1 pair
const quoteId = quote.quoteId;

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4. Build & open the order

The SDK builds the StandardOrder for you — pass plain token addresses + chain ids; it computes the nonce, deadlines, oracle, and EIP-7930 encoding. getOracle supplies the verifier oracle (Polymer addresses below). Then call open(order) on the escrow settler the SDK gives you.

import { Intent, type IntentDeps, type StandardEVM } from "@lifi/intent";
import type { WalletClient } from "viem";

const POLYMER_ORACLE = "0x0000003E06000007A224AeE90052fA6bb46d43C9" as const; // mainnet
const deps: IntentDeps = {
  getOracle: (verifier) => (verifier === "polymer" ? POLYMER_ORACLE : undefined),
};

type Tok = { address: `0x${string}`; chainId: number; decimals: number; name: string };
const ctx = (t: Tok, amount: bigint) => ({
  token: { address: t.address, name: t.name, chainId: BigInt(t.chainId),
           decimals: t.decimals, chainNamespace: "eip155" as const },
  amount,
});

const intent = new Intent({
  inputTokens:  [ctx(fromToken, 100_000_000n)],
  outputTokens: [ctx(toToken, received)],   // `received` from the quote
  verifier: "polymer",
  account: user,
  outputRecipient: user,
  lock: { type: "escrow" },
}, deps).order();

// asOrder() is a union (multichain | EVM | Solana); narrow to the single-chain EVM order
// so it matches the OPEN_ABI StandardOrder tuple.
const order   = intent.asOrder() as StandardEVM; // the StandardOrder struct
const orderId = intent.orderId();                // your tracking handle
const settler = intent.inputSettler;             // InputSettlerEscrow (0x000025c3...)

// 1) ERC-20 approve(settler, amountIn) for the source token if allowance is insufficient
//    (allowance check + ERC20 ABI shown in references/quickstart.md).
// 2) Open the order (full `open` ABI is in references/quickstart.md). viem's writeContract
//    needs `account` and `chain` when the wallet client has none bound:
const txHash = await wallet.writeContract({
  address: settler, abi: OPEN_ABI, functionName: "open", args: [order],
  account: user, chain: wallet.chain,
});

---

5. Track the order to settlement

Poll GET https://order.li.fi/orders/status?onChainOrderId=<orderId>:

const status = await fetch(
  `https://order.li.fi/orders/status?onChainOrderId=${orderId}`,
).then((r) => r.json());
// status.meta.orderStatus: Signed -> Delivered -> Settled (or Expired -> refundable)

| Status | Meaning | |--------|---------| | Signed | Order opened and broadcast to the solver network | | Delivered | Solver has delivered the assets on the destination chain | | Settled | Oracle verified delivery; the user's locked funds released to the solver (terminal) | | Expired | No solver filled before the deadline — the user can claim a refund |

The status response also carries the destination/settlement transaction hashes — surface the destination tx so the user (and your ops/compliance) can verify delivery on a block explorer.

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6. The interface

A clean 1:1 swap UI has three states. Keep gas, spreads, and solver mechanics off the screen.

1. Quote — user picks send token + chain, receive token + chain, and an amount. Call getQuotes and display the received amount; for a 1:1-enabled integrator it reads back equal ("Send 100 USDC → Receive 100 USDC"). Show a single number; no fee field.
2. In progress — after approve + open, show a simple status from /orders/status ("Submitted → Delivered → Settled") with a link to the source transaction.
3. Done — show "Delivered" with the destination transaction link and the orderId as a verifiable receipt. Offer "swap again".

A complete, runnable React / Next.js interface is in references/quickstart.md — including the full open ABI, the ERC-20 approve/allowance step, and the wagmi createConfig + provider wiring the wallet hooks need.

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7. Option 2 — raw REST (any language)

No SDK needed; call order.li.fi directly. The Intents API uses EIP-7930 interoperable addresses for user/asset/receiver (chain embedded in the address) — e.g. USDC on Base (chain id 8453 = 0x2105, token 0x833589…02913) encodes as 0x0001000002210514833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 (0001=version, 0000=EVM, 02=chain-ref len, 2105=chain id, 14=addr len, then the 20-byte address). Amounts are strings in smallest units.

Quote — POST https://order.li.fi/quote/request (under your integrator key):

{
  "user": "<eip7930>",
  "intent": {
    "intentType": "oif-swap",
    "swapType": "exact-input",
    "inputs":  [{ "user": "<eip7930>", "asset": "<eip7930 source token>", "amount": "100000000" }],
    "outputs": [{ "receiver": "<eip7930>", "asset": "<eip7930 dest token>", "amount": null }]
  },
  "supportedTypes": ["oif-escrow-v0"]
}

Read quotes[0].preview.outputs[0].amount (and quoteId, validUntil). Then build the StandardOrder, ABI-encode it, and call open(order) on InputSettlerEscrow. The struct:

tuple(
  address user, uint256 nonce, uint256 originChainId,
  uint32 expires,        // final deadline; refundable after this
  uint32 fillDeadline,   // solver fill cutoff; must be < expires
  address inputOracle,   // Polymer Oracle (below)
  uint256[2][] inputs,   // [tokenId (input token address as uint256), amount]
  tuple(bytes32 oracle, bytes32 settler, uint256 chainId, bytes32 token,
        uint256 amount, bytes32 recipient, bytes callbackData, bytes context)[] outputs
)

outputs[].settler is the Output Settler; recipient/token are bytes32-padded addresses; callbackData/context are 0x for a plain transfer. Track via the same GET /orders/status?onChainOrderId=....

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Contract addresses (same on supported EVM chains)

| Contract | Address | |----------|---------| | InputSettlerEscrow | 0x000025c3226C00B2Cdc200005a1600509f4e00C0 | | Output Settler | 0x0000000000eC36B683C2E6AC89e9A75989C22a2e | | Polymer Oracle (mainnet) | 0x0000003E06000007A224AeE90052fA6bb46d43C9 |

Supported chains and live routes are solver-driven and dynamic — query GET /chains/supported and GET /routes rather than hardcoding.

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Resources

• LI.FI Intents — https://docs.li.fi/lifi-intents/introduction
• Intents quickstart — https://docs.li.fi/lifi-intents/quickstart
• Intents API overview — https://docs.li.fi/lifi-intents/intents-api/api-overview
• Partner Portal (register your integrator) — https://portal.li.fi
• Interactive API spec — https://order.li.fi/docs