Trading / Provider Adapters • CoW Protocol Tutorial

The CoW Protocol SDK is designed to work with multiple Ethereum libraries through a provider adapter system. This approach allows you to use the same SDK API regardless of whether you prefer Viem, Ethers v6, or Ethers v5.

What are Provider Adapters?

Provider adapters are wrapper classes that provide a unified interface to different Ethereum libraries. They handle the differences between libraries so you don't have to worry about implementation details.

Supported adapters:

✅ ViemAdapter - For Viem (used in these tutorials)
✅ EthersV6Adapter - For Ethers v6
✅ EthersV5Adapter - For Ethers v5

Adapter Examples

While these tutorials use Viem, here's how you would initialize each adapter:

Viem Adapter

run.ts

import { setGlobalAdapter } from '@cowprotocol/cow-sdk'
import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'
import { createWalletClient, createPublicClient, http, custom } from 'viem'
import { mainnet } from 'viem/chains'

const publicClient = createPublicClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})

const walletClient = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})

const adapter = new ViemAdapter({
  provider: publicClient,
  walletClient
})

setGlobalAdapter(adapter)

EthersV6 Adapter

run.ts

import { setGlobalAdapter } from '@cowprotocol/cow-sdk'
import { EthersV6Adapter } from '@cowprotocol/sdk-ethers-v6-adapter'
import { ethers } from 'ethers' // v6

const provider = new ethers.BrowserProvider(window.ethereum)
const signer = await provider.getSigner()
const adapter = new EthersV6Adapter({ provider, signer })

setGlobalAdapter(adapter)

EthersV5 Adapter

run.ts

import { setGlobalAdapter } from '@cowprotocol/cow-sdk'
import { EthersV5Adapter } from '@cowprotocol/sdk-ethers-v5-adapter'
import { ethers } from 'ethers'

const provider = new ethers.providers.Web3Provider(window.ethereum)
const signer = provider.getSigner()
const adapter = new EthersV5Adapter({ provider, signer })

setGlobalAdapter(adapter)

Note: Future tutorials will cover EthersV5 and EthersV6 adapters in detail. For now, we focus on Viem.

Why Do We Need Adapters?

Different Ethereum libraries have different APIs:

run.ts

// Viem
const publicClient = createPublicClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})
const walletClient = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})

// Ethers v6
const ethersProvider = new ethers.BrowserProvider(window.ethereum)
const ethersSigner = await ethersProvider.getSigner()

// Ethers v5
const ethersV5Provider = new ethers.providers.Web3Provider(window.ethereum)
const ethersV5Signer = ethersV5Provider.getSigner()

Adapters abstract these differences, allowing the SDK to work consistently with any library.

Global Adapter Configuration

When you use @cowprotocol/cow-sdk, the SDK uses a global adapter pattern:

Configure once with setGlobalAdapter()
All SDK classes use it automatically

This means you set up your preferred Ethereum library once, and all SDK components (OrderBookApi, MetadataApi, etc.) automatically use it internally.

Viem Setup

For these tutorials, we'll use Viem:

run.ts

import { setGlobalAdapter } from '@cowprotocol/cow-sdk'
import { ViemAdapter } from '@cowprotocol/sdk-viem-adapter'
import { createPublicClient, createWalletClient, custom } from 'viem'
import { mainnet } from 'viem/chains'

// Create adapter with your provider and wallet client
const publicClient = createPublicClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})

const walletClient = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})

const adapter = new ViemAdapter({
  provider: publicClient,
  walletClient
})

// Set as global adapter (do this once in your app)
setGlobalAdapter(adapter)

// Now all SDK classes from @cowprotocol/cow-sdk use this adapter automatically:
// const orderBookApi = new OrderBookApi({ chainId }) // ✅ Uses the adapter
// const metadataApi = new MetadataApi() // ✅ Uses the adapter

Updating the Wallet Client

If you need to change the wallet client (e.g., user switches accounts), you can update it:

run.ts

// Create a new wallet client with the updated account
const newWalletClient = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum)
})

// Update the adapter with the new wallet client
adapter.setSigner(newWalletClient.account!)

// The adapter now uses the new wallet client for all operations

Testing the Setup

Let's test the adapter configuration by:

Creating an EthersV5Adapter
Setting it as the global adapter
Verifying it works correctly

The adapter handles blockchain operations like getting chain ID, addresses, and signing - all the low-level details you need for trading on CoW Protocol.

Run the code

To run the code, we can press the "Run" button in the bottom right panel (the web container).

When running the script, we may be asked to connect a wallet. We can use Rabby for this.

Accept the connection request in Rabby
Press the "Run" button again
Observe the adapter information returned to the output panel

An example output should look like:

output.json

{
  "adapterInfo": {
	"type": "ViemAdapter",
	"adapterChainId": 100,
	"hasSigner": true
  },
  "chainId": 100,
  "address": "0x...",
  "globalAdapterConfigured": true
}

What's Next?

With adapters configured, you can now use any CoW Protocol SDK component. They'll all automatically use your configured adapter for blockchain interactions.

Next: Quoting

import type { PublicClient, WalletClient } from 'viem';

import { SupportedChainId } from '@cowprotocol/cow-sdk';

export async function run(

	setup: (chainId: SupportedChainId) => Promise<{ publicClient: PublicClient; walletClient: WalletClient }>

): Promise<unknown> {

	const { publicClient, walletClient } = await setup(SupportedChainId.GNOSIS_CHAIN);

	// TODO: create an instance of ViemAdapter using publicClient and walletClient

	return {

		publicClient,

		walletClient

};

initialising