Place bet

placeBet is the core SDK action. It encrypts the user's stake and chosen outcome using Arcium's x25519 + RescueCipher scheme, bundles the deposit and MPC queue instructions into a single transaction, waits for the Arcium callback to finalize entry odds, then returns the result.

Rendering diagram…

Rendering diagram…

const result = await client.actions.placeBet({
  payer: keypair.publicKey,
  user: keypair.publicKey,
  marketId: 42n,
  side: 1,              // 1 = YES for a YesNo market
  amountUsdc: 5_000_000n, // $5.00 USDC (6 decimals)
  onProgress: ({ stage, message }) => console.log(`[${stage}] ${message}`),
});

// Persist the private key immediately
saveSecret(result.position!.market, result.betIndex, result.userKeypair.privateKey);

const result = await client.actions.placeBet({
  payer: keypair.publicKey,
  user: keypair.publicKey,
  marketId: 42n,
  side: 1,              // 1 = YES for a YesNo market
  amountUsdc: 5_000_000n, // $5.00 USDC (6 decimals)
  onProgress: ({ stage, message }) => console.log(`[${stage}] ${message}`),
});

// Persist the private key immediately
saveSecret(result.position!.market, result.betIndex, result.userKeypair.privateKey);

Warning: Call saveSecret (or store result.userKeypair.privateKey) before the page unloads. If the process exits without saving it, you lose the ability to display your side in the UI. Your funds are still safe - you can still claim.

---

Parameters

payer PublicKey required

Transaction fee payer and rent payer. Usually the connected wallet public key.

user PublicKey required

The bettor whose position PDA is created. The position is keyed on user, not payer - in relay flows these can differ. Usually user === payer.

marketId bigint | number required

Numeric market ID (the marketId field on MarketAccount).

side number required

Outcome index to bet on.

Value	YesNo markets	MultiOutcome markets
0	NO	Option 0 (first label)
1	YES	Option 1
2	-	Option 2
3	-	Option 3

amountUsdc bigint | number required

Gross bet in micro-USDC (6 decimal places). 1_000_000n = $1.00. The SDK deducts protocol and LP fees and encrypts the net amount.

userKeypair UserCryptoKeypair

Pre-generated x25519 keypair. If omitted, the SDK generates one via createUserKeypair(). Pass one only if you created and stored it before calling placeBet (e.g., for a pre-flight UX that shows the keypair to the user first).

computationOffset bigint

Arcium computation slot offset. Random by default. Override for testing or retry correlation.

timeoutMs number

Milliseconds to wait for the Arcium callback. Defaults to the SDK global (60_000). Set higher for slow network conditions.

onProgress ProgressCallback

Called at each stage of the flow. Useful for driving a live status UI.

onProgress: ({ stage, message, signature, computationOffset }) => {
  setStatus(`${stage}: ${message}`);
}

onProgress: ({ stage, message, signature, computationOffset }) => {
  setStatus(`${stage}: ${message}`);
}

See the progress stages table below.

---

Return value

signature string

Base58 transaction signature of the bet + queue transaction.

userKeypair UserCryptoKeypair

The x25519 keypair used to encrypt the bet. privateKey is a Uint8Array - persist it immediately.

interface UserCryptoKeypair {
  privateKey: Uint8Array; // 32 bytes - persist this
  publicKey: Uint8Array;  // 32 bytes - stored on-chain
}

interface UserCryptoKeypair {
  privateKey: Uint8Array; // 32 bytes - persist this
  publicKey: Uint8Array;  // 32 bytes - stored on-chain
}

betIndex bigint

The position index assigned to this bet. Users who place multiple bets on the same market get incrementing indices (0n, 1n, 2n, ...). Pass this to saveSecret, claimPayout, and claimRefund.

position EncryptedPositionAccount | null

The position account refetched after the callback ran. null on very rare RPC slowness - the funds are always safe.

computation ComputationResult

Raw Arcium computation result. Contains computationOffset and callback slot info. Useful for debugging.

computationOffset bigint

The Arcium computation slot offset used for this bet.

---

Progress stages

The onProgress callback fires at each of these stages:

Stage	What's happening
validating	Market exists and is Active; amount exceeds min_bet
fetching-state	Fetching GlobalState for fee rates and accepted mint
encrypting	Generating x25519 keypair; encrypting (netAmount, side) with RescueCipher
submitting	Sending the deposit + MPC queue transaction
awaiting-callback	Waiting for Arcium MPC nodes to finalize entry odds (~5-15 sec)
refetching	Fetching the updated position account
done	Bet placed; result returned

---

Persisting the private key

The bet position is fully encrypted on-chain. The only way to display the bet side or stake in your UI later is to re-derive the RescueCipher using the original private key. Store it using the same key format the website uses:

// src/lib/persist-secret.ts
const key = `cypher:pos:${market.toBase58()}:${betIndex}`;

export function saveSecret(market: PublicKey, betIndex: bigint, secret: Uint8Array) {
  const hex = Array.from(secret, (b) => b.toString(16).padStart(2, "0")).join("");
  localStorage.setItem(key, hex);
}

export function loadSecret(market: PublicKey, betIndex: bigint): Uint8Array | null {
  const hex = localStorage.getItem(key);
  if (!hex) return null;
  const arr = new Uint8Array(hex.length / 2);
  for (let i = 0; i < arr.length; i++) {
    arr[i] = parseInt(hex.slice(i * 2, i * 2 + 2), 16);
  }
  return arr;
}

// src/lib/persist-secret.ts
const key = `cypher:pos:${market.toBase58()}:${betIndex}`;

export function saveSecret(market: PublicKey, betIndex: bigint, secret: Uint8Array) {
  const hex = Array.from(secret, (b) => b.toString(16).padStart(2, "0")).join("");
  localStorage.setItem(key, hex);
}

export function loadSecret(market: PublicKey, betIndex: bigint): Uint8Array | null {
  const hex = localStorage.getItem(key);
  if (!hex) return null;
  const arr = new Uint8Array(hex.length / 2);
  for (let i = 0; i < arr.length; i++) {
    arr[i] = parseInt(hex.slice(i * 2, i * 2 + 2), 16);
  }
  return arr;
}

To decrypt and display the position later, see Encryption - Decrypt flow.

---

Multi-bet support

Each user can hold multiple positions per market. The SDK auto-reads user_state.next_bet_index before each bet and retries up to 3 times on concurrent-bet conflicts. You do not need to track betIndex yourself before calling placeBet.

// Two sequential bets on the same market
const r1 = await client.actions.placeBet({ ..., side: 0, amountUsdc: 2_000_000n });
saveSecret(r1.position!.market, r1.betIndex, r1.userKeypair.privateKey); // betIndex = 0n

const r2 = await client.actions.placeBet({ ..., side: 1, amountUsdc: 3_000_000n });
saveSecret(r2.position!.market, r2.betIndex, r2.userKeypair.privateKey); // betIndex = 1n

// Two sequential bets on the same market
const r1 = await client.actions.placeBet({ ..., side: 0, amountUsdc: 2_000_000n });
saveSecret(r1.position!.market, r1.betIndex, r1.userKeypair.privateKey); // betIndex = 0n

const r2 = await client.actions.placeBet({ ..., side: 1, amountUsdc: 3_000_000n });
saveSecret(r2.position!.market, r2.betIndex, r2.userKeypair.privateKey); // betIndex = 1n