How to sign with a browser wallet

This guide shows you how to let a user trade through an injected wallet such as MetaMask instead of a private key held by your code. It assumes a React app with wagmi or another source of a viem WalletClient. For a Node process, use privateKey instead; see Configure the SDK.

Construct without a signer, bind on connect

A browser app has no signer at boot. Construct the exchange for public reads, then bind the wallet when it connects and unbind it when it disconnects.

import { useEffect } from "react";
import { useWalletClient } from "wagmi";
import { exchange } from "./exchange.js"; // the module-scope SomniaMarkets instance

export function SignerBinding() {
  const { data: walletClient } = useWalletClient();
  useEffect(() => {
    exchange.setSigner(walletClient ? { walletClient } : {});
  }, [walletClient]);
  return null;
}

setSigner replaces the trader that every authenticated verb uses and updates exchange.walletAddress. Live watches and market data are unaffected.

After binding, the exchange verbs work as they do with a private key:

const order = await exchange.createOrder("SOMI/USDso", "limit", "buy", 10, 0.11);

What differs from a local key

The wallet signs after a user prompt, sends through eth_sendTransaction, and the SDK reads the receipt on the next block heads instead of in one round-trip. The first order per token also prompts for an approval. Both paths resolve to the same result shape once the transaction is mined. The Configuration reference tabulates the differences.

Make sure the wallet is on the right chain

The SDK does not switch chains. Check walletClient.chain?.id against exchange.client.config.chain.id before a write, and ask the wallet to switch with wagmi's useSwitchChain when they differ. A write from the wrong chain is rejected by the wallet or the node, not by the SDK.

Use the owner-derived trader with a wallet

After setSigner binds the wallet, use the trader owned by the same exchange. It inherits the exchange's chain, read client, addresses, and lifecycle.

await exchange.trader.faucet();

Show the connected account's data

fetchBalance, fetchOpenOrders, watchOrders, and watchMyTrades answer for exchange.walletAddress. In React, prefer the hooks with the account from wagmi's useAccount: useWatchUser(address) plus useLiveUserOrders(pool, address). See Use the React hooks.

Handle a rejected prompt

A user who dismisses the wallet prompt produces an error from the wallet, not from the SDK. It does not extend SomniaMarketsError, so keep a final throw or a wallet-specific branch in your handler. See Handle errors and reverts.