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Introduction

Turnkey wallets are embedded, web-based wallets that differ from injected wallets (like MetaMask). While injected wallets store private keys locally and decrypt them using a password to sign transactions, embedded wallets rely on UI-based authentication to access private keys that are securely stored and managed by Turnkey. With this concept in mind, we’re going to build a custom Wagmi connector that communicates with an embedded wallet rendered in a popup, enabling integration across multiple dApps.

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System Components Overview

Our system involves three key parts working together: Embedded Wallet (Pop-up): A web application (likely React/Next.js) hosted by you. This UI handles user authentication (passkeys via Turnkey), transaction signing, and communication with the dApp via postMessage. It securely interacts with the Turnkey API. Reference the popup-wallet-demo’s @/apps/wallet provides a concrete example. EIP-1193 Provider: A JavaScript class implementing the EIP-1193 standard. It acts as the intermediary between the dApp and the popup embedded wallet. Reference the popup-wallet-demo’s @/apps/dapp/lib/eip1193-provider.ts provides a concrete example. Wagmi Connector: A custom connector built using Wagmi’s createConnector utility. It wraps our EIP-1193 provider, making the wallet compatible with the Wagmi ecosystem. Reference the popup-wallet-demo’s @/apps/dapp/lib/connector.ts and @/apps/dapp/lib/wagmi.ts provide concrete examples.

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Architecture Flow

The interaction sequence generally follows these steps: Connection:
  • A user on a dApp clicks “Connect Wallet” and selects your wallet.
  • The dApp calls the connect method on your Wagmi connector.
  • The connector initializes the EIP-1193 provider.
  • The connector calls provider.request({ method: 'eth_requestAccounts' }), which opens your Embedded Wallet pop-up.
  • The user authenticates in the pop-up and chooses which wallet account to connect.
  • The pop-up returns the selected account(s) and chainId to the provider via postMessage.
  • The provider resolves eth_requestAccounts, and the connector returns the account(s) and chainId to the dApp.
RPC Request (e.g., eth_sendTransaction):
  • The dApp uses a Wagmi hook (e.g., useSendTransaction) which triggers a request.
  • Wagmi sends the eth_sendTransaction request to your connector.
  • The connector forwards the request to the EIP-1193 provider.
  • The provider identifies this as a signing request and opens the Embedded Wallet pop-up (if not already open), sending the transaction details via postMessage.
  • The user reviews and approves the transaction in the pop-up.
  • The pop-up uses Turnkey to sign the transaction and potentially broadcast it (or return the signed transaction).
  • The pop-up sends the transaction hash (or signed transaction) back to the provider via postMessage.
  • The provider resolves the request promise, returning the result to the dApp via the connector.
RPC Request (e.g., eth_blockNumber):
  • The dApp triggers a read-only request.
  • Wagmi sends the eth_blockNumber request to your connector.
  • The connector forwards it to the EIP-1193 provider.
  • The provider identifies this as a read-only request and forwards it directly to a public RPC node.
  • The public RPC node returns the result.
  • The provider returns the result to the dApp via the connector.

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Flow Diagram

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Connect flow demo

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Building the Embedded Wallet (Pop-up)

The embedded wallet is a standalone web app (often a separate Next.js project) that is opened in a pop-up when the provider executes eth_requestAccounts.

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Create the wallet page

Below is a minimal wallet UI plus a stubbed authentication button, shown side-by-side with Mintlify’s <CodeGroup> component so you can copy either file. 
import { AuthButton } from "@/components/auth";

// A minimal wallet UI that only handles `eth_requestAccounts`
export default function Page({
  searchParams,
}: {
  searchParams: { request?: string };
}) {
  // Decode the JSON-RPC request that the provider placed in the URL
  const rpcRequest = searchParams.request
    ? JSON.parse(decodeURIComponent(searchParams.request))
    : null;

  // Support connection only
  if (rpcRequest?.method !== "eth_requestAccounts") {
    return (
      <main className="flex min-h-screen items-center justify-center">
        <p>Unsupported method</p>
      </main>
    );
  }

  return (
    <main className="flex min-h-screen flex-col items-center justify-center gap-4">
      <h1 className="text-xl font-semibold">Connect Wallet</h1>
      <AuthButton />
    </main>
  );
}
How it works
  1. The provider opens the pop-up at https://<your-wallet-host>/?request=<encoded-json-rpc>.
  2. The page decodes the request query parameter.
    For the connection flow this will look like: 
    {
  "method": "eth_requestAccounts",
  "params": []
}
  3. When the user clicks Connect Wallet the AuthButton performs your authentication logic (Turnkey passkey, email-magic-link, etc.).
  4. Once authenticated, the wallet sends a postMessage back to the opener containing the selected account(s) and chainId.
    We will wire up that message handling in the next section.
With this single page in place you now have a functional authentication UI that the provider can open, fulfilling the first half of the connection flow: 
DApp → Connector → Provider → (opens) Wallet UI → user authenticates → …
Next we will implement the message bridge in the provider and then expand the wallet to handle transaction and message signing.

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Post the account back to the opener

Inside your AuthButton (or wherever your auth logic resolves) send a message with the newly authenticated account:
components/auth.tsx
// ...after you have the accounts array and chainId
window.opener?.postMessage(
  {
    type: "ETH_ACCOUNTS",
    accounts, // e.g. ["0xAbc…"]
    chainId, // e.g. 17000 (Holesky)
  },
  "*"
);
// Optionally close the popup or show a success screen
This keeps the wallet UI decoupled from the provider implementation—any parent window that understands the ETH_ACCOUNTS message can integrate.

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Implement a minimal EIP-1193 provider

Create eip1193-provider.ts in your dApp project. For the connection flow we only need to implement eth_requestAccounts and eth_accounts:
eip1193-provider.ts
import type { EIP1193RequestFn, EIP1193Provider } from "viem";

export function createEIP1193Provider(): EIP1193Provider {
  let popup: Window | null = null;
  let cachedAccounts: readonly `0x${string}`[] = [];

  const request: EIP1193RequestFn = async ({ method, params }) => {
    // Return cache immediately
    if (method === "eth_accounts") return cachedAccounts;

    if (method === "eth_requestAccounts") {
      return new Promise((resolve, reject) => {
        // 1. Listen for postMessage from wallet
        const handleMessage = (event: MessageEvent) => {
          const { type, accounts, chainId } = event.data || {};
          if (type !== "ETH_ACCOUNTS") return;
          window.removeEventListener("message", handleMessage);
          cachedAccounts = accounts;
          resolve(accounts);
        };
        window.addEventListener("message", handleMessage);

        // 2. Open wallet popup (centered)
        const w = 360,
          h = 600,
          left = window.screenX + (window.outerWidth - w) / 2,
          top = window.screenY + (window.outerHeight - h) / 2;
        popup = window.open(
          `http://localhost:3001?request=${encodeURIComponent(
            JSON.stringify({ method, params })
          )}`,
          "Berakin Wallet",
          `width=${w},height=${h},left=${left},top=${top}`
        );
        if (!popup) reject(new Error("Popup blocked"));
      });
    }

    throw new Error(`${method} not implemented in minimal provider`);
  };

  // Very small subset of the provider interface we need for Wagmi
  return {
    request,
    // no-ops for event listeners for now; Wagmi expects them to exist
    on: () => {},
    removeListener: () => {},
  } as EIP1193Provider;
}
This provider:
  1. Caches accounts after the first successful connection.
  2. Opens the wallet pop-up and waits for a postMessage containing ETH_ACCOUNTS.
  3. Resolves the eth_requestAccounts promise and lets Wagmi continue.

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Wire it up in a Wagmi connector

Your minimal connector only needs the connect method to use the provider you just built. The full version from popup-wallet-demo already includes this; here’s the shortened core for reference:
connector.ts
export function berakinWalletConnector() {
  let provider: EIP1193Provider | null = null;

  return createConnector((config) => ({
    id: "berakinWallet",
    name: "Berakin Wallet",

    async connect() {
      provider = provider ?? createEIP1193Provider();
      const accounts = (await provider.request({
        method: "eth_requestAccounts",
      })) as readonly `0x${string}`[];
      return { accounts, chainId: 17000 };
    },

    async getProvider() {
      return provider ?? (provider = createEIP1193Provider());
    },
  }));
}
At this point you can:
  1. Run your wallet project on localhost:3001.
  2. Integrate the minimal provider + connector in a dApp.
  3. Click Connect Wallet in the dApp → the pop-up opens → authenticate → dApp receives the account.
🎉 You now have a working end-to-end connection flow! Next we’ll extend both the wallet UI and the provider to support signing transactions and messages.

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Add transaction and message signing

Connection works. Next, implement signing so the dApp can call useSendTransaction, useSignMessage, and related Wagmi hooks.

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Wallet-side components

"use client";

import { useState } from "react";
import type { Address } from "viem";
import { signAndSend } from "@/lib/turnkey";

interface Props {
  transaction: Record<string, unknown>; // raw tx params
  organizationId: string;
}

export function SignTransaction({ transaction, organizationId }: Props) {
  const [submitting, setSubmitting] = useState(false);
  const [error, setError] = useState<string | null>(null);

  const handleApprove = async () => {
    setSubmitting(true);
    try {
      const txHash = await signAndSend(transaction, organizationId);
      window.opener?.postMessage(
        { type: "RPC_RESPONSE", method: "eth_signTransaction", result: txHash },
        "*"
      );
      window.close();
    } catch (err: unknown) {
      setError(String(err));
    } finally {
      setSubmitting(false);
    }
  };

  return (
    <div className="space-y-4">
      <h2 className="text-lg font-semibold">Review Transaction</h2>
      <pre className="max-h-60 overflow-auto rounded bg-zinc-900 p-2 text-sm">
        {JSON.stringify(transaction, null, 2)}
      </pre>
      {error && <p className="text-red-500">{error}</p>}
      <button
        className="rounded bg-indigo-600 px-4 py-2 text-white"
        onClick={handleApprove}
        disabled={submitting}
      >
        {submitting ? "Signing…" : "Approve & Sign"}
      </button>
    </div>
  );
}

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Provider extensions

Augment the provider so signing requests are routed through the popup.
eip1193-provider.ts (diff)
// inside createEIP1193Provider.request
if (
  method === "eth_signTransaction" ||
  method === "eth_sign" ||
  method === "personal_sign"
) {
  return popupRequest({ method, params });
}

// Convenience: wrap eth_sendTransaction to auto-sign & send raw tx
if (method === "eth_sendTransaction") {
  const [tx] = params as any[];
  const signed = await request({ method: "eth_signTransaction", params: [tx] });
  return request({ method: "eth_sendRawTransaction", params: [signed] });
}
popupRequest is the existing helper that opens/targets the window and resolves the corresponding RPC_RESPONSE.

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Summary

You now handle: • Connection (eth_requestAccounts).
• Transaction signing (eth_signTransaction / eth_sendTransaction).
• Message signing (personal_sign / eth_sign). From here you can layer additional EIP-1193 methods (chain switching, asset watch, etc.) as needed.

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Production considerations

The code samples target a minimal, easy-to-understand prototype. When moving to production, address the following: • Request IDs & queueing – generate a unique id per RPC call, store promises by id, include it in every postMessage so concurrent requests cannot collide.
• Session persistence – cache accounts and chainId in localStorage and return them on subsequent eth_accounts calls without re-authenticating.
• Popup cancellation & timeouts – reject pending promises if the user closes the window or after a reasonable timeout.
• Network switching – implement wallet_switchEthereumChain, update store.chainId, and emit chainChanged.
• Security – validate event.origin, allow-list dApp domains, move hard-coded URLs (localhost:3001, RPC endpoints) into environment variables.
• Additional EIPs – support wallet_watchAsset, eth_addEthereumChain, etc., if dApps require them. Addressing these items will bring the prototype to production-ready quality without altering the core architecture documented above.