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

# Use Lasso with viem or ethers on Base

> Replace one Base RPC URL, verify chain identity, and evaluate Lasso without changing your Ethereum client.

Lasso exposes standard EVM JSON-RPC. Start with one server-side read path in your
Base application and replace its RPC URL with a Lasso endpoint. Keep your client
library and application contract calls.

## Prepare the endpoint

Check [live managed chains](https://lasso.sh/api/v1/agent/chains) for Base before
choosing a managed profile. If you have existing Base provider URLs, configure a
[custom provider pool](/cloud/bring-your-own-rpc) instead. Use the
[quickstart](/cloud/quickstart) or the available [agent workflow](/cloud/agent-flows)
to obtain an endpoint.

Store the complete endpoint as `LASSO_RPC_URL` in your existing server-side secret
manager. Keep the previous RPC URL for rollback. An endpoint containing a key is a
credential; exposing it in a browser bundle lets visitors use its access and quota.

## viem

```typescript theme={null}
import { createPublicClient, http } from "viem";
import { base } from "viem/chains";

const url = process.env.LASSO_RPC_URL;
if (!url) throw new Error("LASSO_RPC_URL is required");

const client = createPublicClient({
  chain: base,
  transport: http(url),
});

if ((await client.getChainId()) !== base.id) {
  throw new Error("Unexpected RPC chain");
}
const blockNumber = await client.getBlockNumber();
console.log({ blockNumber: blockNumber.toString() });
```

See the [viem public client reference](https://viem.sh/docs/clients/public) for
client options. Configure application timeouts and retries around the operations
you actually perform; transaction submission has different recovery needs from a
read.

## ethers v6

```typescript theme={null}
import { JsonRpcProvider } from "ethers";

const url = process.env.LASSO_RPC_URL;
if (!url) throw new Error("LASSO_RPC_URL is required");

const provider = new JsonRpcProvider(url, undefined, {
  batchMaxCount: 1,
  polling: true,
});

try {
  if ((await provider.getNetwork()).chainId !== 8453n) {
    throw new Error("Unexpected RPC chain");
  }
  console.log({ blockNumber: await provider.getBlockNumber() });
} finally {
  provider.destroy();
}
```

This evaluation sends individual requests and uses polling rather than
provider-local HTTP filters. Lasso rejects those filters. Once the flow works,
choose batching within the live Lasso and upstream limits. The
[ethers JSON-RPC provider reference](https://docs.ethers.org/v6/api/providers/jsonrpc/)
describes these options.

## Verify the application flow

Run a representative read with the same block selector against both endpoints.
For related state values, [select one block hash](/cloud/read-at-one-block) so head
movement does not masquerade as a routing discrepancy. Record latency, error rate
and [routing evidence](/cloud/observability) without logging credentials.

Move one request flow first. If its behavior fails your acceptance criteria,
restore the previous URL. Test transaction sending, historical ranges and
WebSocket subscriptions separately; an `eth_blockNumber` response does not
qualify those workloads.