Skip to main content
Build an unsigned Solana versioned transaction from an Overpass exact-in quote. 
POST https://api-v1.overpass.ag/v1/swap
The transaction deposits an underlying asset and mints the yield token, or burns the yield token and withdraws the underlying asset. The direction comes from the quote’s mint pair.

​
Request body

FieldTypeRequiredDescription
userPublicKeystringYesWallet that signs and pays for the transaction.
quoteResponseobjectConditionalComplete response returned by GET /v1/quote. Required unless inputMint, outputMint, and amount are supplied directly.
priorityFeeMicroLamportsintegerNoCompute-unit price in micro-lamports. Defaults to 0.
computeUnitLimitintegerNoExplicit compute-unit limit. The API otherwise uses the builder’s suggested limit.
Pass the quote response unchanged. This preserves the quote’s otherAmountThreshold as the minimum acceptable output. 
const response = await fetch("https://api-v1.overpass.ag/v1/swap", {
  method: "POST",
  headers: {
    "content-type": "application/json",
  },
  body: JSON.stringify({
    userPublicKey: wallet.publicKey.toBase58(),
    quoteResponse,
  }),
});

if (!response.ok) {
  const error = await response.json();
  throw new Error(error.message ?? error.error);
}

const swap = await response.json();

​
Response

{
  "swapTransaction": "AQAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...",
  "lastValidBlockHeight": 409970749,
  "prioritizationFeeLamports": 0,
  "priorityFeeMicroLamports": 0,
  "computeUnitLimit": 430000,
  "swapMode": "ExactIn",
  "txVersion": "V0",
  "quoteResponse": {
    "inputMint": "So11111111111111111111111111111111111111112",
    "inAmount": "10000000",
    "outputMint": "HtnnuzVtecjktsUoZjHaZoZ9u4jPAzGpujE82U3v3cAV",
    "outAmount": "9922552",
    "otherAmountThreshold": "9872939",
    "swapMode": "ExactIn",
    "slippageBps": 50,
    "platformFee": null,
    "priceImpactPct": "0",
    "routePlan": [
      {
        "swapInfo": {
          "ammKey": "9iJeZPrNJrBEjj4h7tD9P3hygyM4hpZmyqrQmHjNUpdA",
          "label": "Overpass kamino",
          "inputMint": "So11111111111111111111111111111111111111112",
          "outputMint": "HtnnuzVtecjktsUoZjHaZoZ9u4jPAzGpujE82U3v3cAV",
          "inAmount": "10000000",
          "outAmount": "9922552",
          "feeAmount": "0",
          "feeMint": "So11111111111111111111111111111111111111112"
        },
        "percent": 100
      }
    ],
    "contextSlot": 431902057,
    "timeTaken": 0.029,
    "wrapperMint": "HtnnuzVtecjktsUoZjHaZoZ9u4jPAzGpujE82U3v3cAV",
    "wrapperVault": "9iJeZPrNJrBEjj4h7tD9P3hygyM4hpZmyqrQmHjNUpdA",
    "underlyingMint": "So11111111111111111111111111111111111111112",
    "sourcePool": "HaVsdBb4mMoYQ3vnS7wCdvhixg5xFQALmFwyL9QJm3fn",
    "protocol": "kamino",
    "direction": "deposit",
    "protocolDepositFeeBps": 0,
    "creatorDepositFeeBps": 0,
    "warnings": []
  }
}
FieldDescription
swapTransactionBase64-encoded unsigned versioned transaction.
lastValidBlockHeightLast block height at which the transaction remains valid.
prioritizationFeeLamportsTotal priority fee implied by the compute limit and compute-unit price.
priorityFeeMicroLamportsCompute-unit price included in the transaction.
computeUnitLimitCompute-unit limit included in the transaction.
txVersionTransaction version. Overpass returns V0.
quoteResponseFresh quote used to build the transaction.

​
Sign and send

Deserialize the transaction, ask the wallet to sign it, and submit the signed bytes through your Solana connection. 
import { Connection, VersionedTransaction } from "@solana/web3.js";

const connection = new Connection(SOLANA_RPC_URL, "confirmed");
const transaction = VersionedTransaction.deserialize(
  Uint8Array.from(globalThis.atob(swap.swapTransaction), (character) =>
    character.charCodeAt(0),
  ),
);

const simulation = await connection.simulateTransaction(transaction, {
  sigVerify: false,
});

if (simulation.value.err) {
  throw new Error(`Simulation failed: ${JSON.stringify(simulation.value.err)}`);
}

const signed = await wallet.signTransaction(transaction);
const signature = await connection.sendRawTransaction(signed.serialize(), {
  skipPreflight: false,
  maxRetries: 3,
});

await connection.confirmTransaction(
  {
    signature,
    blockhash: transaction.message.recentBlockhash,
    lastValidBlockHeight: swap.lastValidBlockHeight,
  },
  "confirmed",
);
Request a new quote and transaction when the block height expires or when execution fails because source-pool state changed.

​
Direct request

You can build a transaction without sending a prior quote response by providing the route fields directly: 
{
  "userPublicKey": "BQ72nSv9f3PRyRKCBnHLVrerrv37CYTHm5h3s9VSGQDV",
  "inputMint": "So11111111111111111111111111111111111111112",
  "outputMint": "HtnnuzVtecjktsUoZjHaZoZ9u4jPAzGpujE82U3v3cAV",
  "amount": "10000000",
  "slippageBps": 50,
  "swapMode": "ExactIn"
}
The API computes a fresh quote before building the transaction. Use the quote-first flow when you need to display the expected output, fees, or warnings before execution.

​
Errors

Swap errors use the same { "error", "message" } shape as the quote endpoint.
StatusMeaning
400Missing quote fields, invalid wallet, amount, slippage, or swap mode.
404No Overpass wrapper route exists for the mint pair.
422The route could not be quoted or built.
429The request exceeded the API rate limit.
503Current source-protocol state is unavailable.