> ## Documentation Index
> Fetch the complete documentation index at: https://www.helius.dev/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# TypeScript SDK Best Practices

> Recommended patterns for AI agents using the Helius TypeScript SDK. Covers transaction history, sending transactions, batching, real-time data, pagination, incremental fetching, common mistakes, and error handling.

Best practices and recommended patterns for agents using the [Helius TypeScript SDK](https://github.com/helius-labs/helius-sdk). For installation and getting started, see the [overview](/agents/typescript-sdk).

## Recommendations for Agents

### Use `getTransactionsForAddress` instead of two-step lookup

`getTransactionsForAddress` combines signature lookup and transaction fetching into a single call with server-side filtering. It supports time/slot ranges, token account filtering, and pagination.

```typescript theme={"system"}
// GOOD: Single call, server-side filtering
const txs = await helius.getTransactionsForAddress([
  "address",
  {
    transactionDetails: "full",
    limit: 100,
    filters: {
      tokenAccounts: "balanceChanged",
      blockTime: { gte: Math.floor(Date.now() / 1000) - 86400 },
    },
  },
]);

// BAD: Two calls, client-side filtering, no token account support
const sigs = await helius.raw.getSignaturesForAddress(address).send();
const txs = await Promise.all(sigs.map(s => helius.raw.getTransaction(s.signature).send()));
```

### Use `sendSmartTransaction` for standard sends

It automatically simulates, estimates compute units, fetches priority fees, and confirms. Do not manually build ComputeBudget instructions — the SDK adds them automatically.

```typescript theme={"system"}
const sig = await helius.tx.sendSmartTransaction({
  instructions: [yourInstruction],
  signers: [walletSigner],
  commitment: "confirmed",
  priorityFeeCap: 100_000,   // Optional: cap fees in microlamports/CU
  bufferPct: 0.1,            // 10% compute unit headroom (default)
});
```

### Use Helius Sender for ultra-low latency

For time-sensitive transactions (arbitrage, sniping, liquidations), use `sendTransactionWithSender`. It routes through Helius's multi-region infrastructure and Jito.

```typescript theme={"system"}
const sig = await helius.tx.sendTransactionWithSender({
  instructions: [yourInstruction],
  signers: [walletSigner],
  region: "US_EAST",          // Default, US_SLC, US_EAST, EU_WEST, EU_CENTRAL, EU_NORTH, AP_SINGAPORE, AP_TOKYO
  swqosOnly: true,            // Route through SWQOS only (lower tip requirement)
  pollTimeoutMs: 60_000,
  pollIntervalMs: 2_000,
});
```

### Use `getAssetBatch` for multiple assets

When fetching more than one asset, batch them. Do not call `getAsset` in a loop.

```typescript theme={"system"}
// GOOD: Single request
const assets = await helius.getAssetBatch({
  ids: ["mint1", "mint2", "mint3"],
  options: { showFungible: true, showCollectionMetadata: true },
});

// BAD: N requests
const assets = await Promise.all(mints.map(id => helius.getAsset({ id })));
```

### Use webhooks or WebSockets instead of polling

Do not poll `getTransactionsForAddress` in a loop. Use webhooks for server-to-server notifications or WebSockets for real-time client-side streaming.

```typescript theme={"system"}
// Webhook: server receives POST on matching transactions
const webhook = await helius.webhooks.create({
  webhookURL: "https://your-server.com/webhook",
  webhookType: "enhanced",
  transactionTypes: ["TRANSFER", "NFT_SALE", "SWAP"],
  accountAddresses: ["address_to_monitor"],
  authHeader: "Bearer your-secret",
});

// WebSocket: stream logs in real-time
const req = await helius.ws.logsNotifications({ mentions: ["address"] });
const stream = await req.subscribe({ abortSignal: controller.signal });
for await (const log of stream) {
  console.log(log);
}
```

## Pagination

The SDK uses different pagination strategies depending on the method.

### Token/Cursor-Based (RPC V2 Methods)

```typescript theme={"system"}
// getTransactionsForAddress uses paginationToken
let paginationToken = null;
const allTxs = [];
do {
  const result = await helius.getTransactionsForAddress([
    "address",
    { limit: 100, paginationToken },
  ]);
  allTxs.push(...result.data);
  paginationToken = result.paginationToken;
} while (paginationToken);

// getProgramAccountsV2 uses paginationKey
let paginationKey = null;
do {
  const result = await helius.getProgramAccountsV2([
    programId,
    { limit: 1000, paginationKey },
  ]);
  // process result.accounts
  paginationKey = result.paginationKey;
} while (paginationKey);
```

### Page-Based (DAS API)

```typescript theme={"system"}
let page = 1;
const allAssets = [];
while (true) {
  const result = await helius.getAssetsByOwner({ ownerAddress: "...", page, limit: 1000 });
  allAssets.push(...result.items);
  if (result.items.length < 1000) break;
  page++;
}
```

## `tokenAccounts` Filter

When querying `getTransactionsForAddress`, the `tokenAccounts` filter controls whether token account activity is included:

| Value              | Behavior                                                | Use When                                                                   |
| ------------------ | ------------------------------------------------------- | -------------------------------------------------------------------------- |
| omitted / `"none"` | Only transactions directly involving the address        | You only care about SOL transfers and program calls                        |
| `"balanceChanged"` | Also includes token transactions that changed a balance | **Recommended for most agents** — shows token sends/receives without noise |
| `"all"`            | Includes all token account transactions                 | You need complete token activity (can return many results)                 |

## `changedSinceSlot` — Incremental Account Fetching

`changedSinceSlot` returns only accounts modified after a given slot. Useful for syncing or indexing workflows. Supported by `getProgramAccountsV2`, `getTokenAccountsByOwnerV2`, `getAccountInfo`, `getMultipleAccounts`, `getProgramAccounts`, and `getTokenAccountsByOwner`.

```typescript theme={"system"}
// First fetch: get all accounts
const baseline = await helius.getProgramAccountsV2([programId, { limit: 10_000 }]);
const lastSlot = currentSlot;

// Later: only get accounts that changed since your last fetch
const updates = await helius.getProgramAccountsV2([
  programId,
  { limit: 10_000, changedSinceSlot: lastSlot },
]);
```

## Common Mistakes

1. **`transactionDetails: "full"` is not the default** — By default, `getTransactionsForAddress` returns signatures only. Set `transactionDetails: "full"` to get full transaction data.

2. **Do not add ComputeBudget instructions with `sendSmartTransaction`** — The SDK adds them automatically. Adding your own causes duplicate instructions and transaction failure.

3. **Priority fees are in microlamports per compute unit** — Not lamports. Values from `getPriorityFeeEstimate` are already in the correct unit for `SetComputeUnitPrice`.

4. **DAS pagination is 1-indexed** — `page: 1` is the first page, not `page: 0`.

5. **`blockTime` is Unix seconds, not milliseconds** — Use `Math.floor(Date.now() / 1000)` when filtering by `blockTime`.

6. **`getAsset` hides fungible tokens by default** — Pass `options: { showFungible: true }` to include them.

7. **WebSocket streams need cleanup** — Always use an AbortController signal and call `helius.ws.close()` when done to avoid connection leaks.

## Error Handling and Retries

The SDK throws native `Error` objects with the HTTP status code embedded in the message string (e.g., `"API error (429): ..."`). There is no `.status` property on the error object, so status detection requires message parsing.

```typescript theme={"system"}
async function withRetry<T>(fn: () => Promise<T>, maxRetries = 3): Promise<T> {
  for (let attempt = 0; attempt <= maxRetries; attempt++) {
    try {
      return await fn();
    } catch (error) {
      const msg = error instanceof Error ? error.message : "";
      const status = msg.match(/\b(\d{3})\b/)?.[1];
      const retryable = status === "429" || (status && status.startsWith("5"));
      if (!retryable || attempt === maxRetries) throw error;
      await new Promise(r => setTimeout(r, 1000 * 2 ** attempt));
    }
  }
  throw new Error("Unreachable");
}
```

| Status | Meaning                        | Action                         |
| ------ | ------------------------------ | ------------------------------ |
| 401    | Invalid or missing API key     | Check API key                  |
| 429    | Rate limited or out of credits | Back off and retry             |
| 5xx    | Server error                   | Retry with exponential backoff |