viem

name	viem
description	Viem blockchain client patterns for Ethereum interactions, transactions, signing, encoding, and smart contract calls. Triggers on viem, publicClient, walletClient, chain, abi.
triggers	["viem","ox","publicClient","walletClient","transport","chain","abi","transaction","signature","encode","decode"]

Build blockchain interactions using viem for Ethereum clients, transactions, signing, and smart contract interactions. Viem is the modern replacement for ethers.js with better TypeScript support.

<mcp_first> CRITICAL: Always fetch viem documentation before implementing.

MCPSearch({ query: "select:mcp__plugin_devtools_context7__query-docs" })

// Client patterns
mcp__context7__query_docs({
  context7CompatibleLibraryID: "/wevm/viem",
  topic: "createPublicClient createWalletClient"
})

// Contract interactions
mcp__context7__query_docs({
  context7CompatibleLibraryID: "/wevm/viem",
  topic: "readContract writeContract simulateContract"
})

// Signing
mcp__context7__query_docs({
  context7CompatibleLibraryID: "/wevm/viem",
  topic: "signMessage signTypedData EIP-712"
})

// Encoding
mcp__context7__query_docs({
  context7CompatibleLibraryID: "/wevm/viem",
  topic: "encodeFunctionData decodeFunctionResult encodeAbiParameters"
})

</mcp_first>

<quick_start> Create clients:

import { createPublicClient, createWalletClient, http } from "viem";
import { mainnet } from "viem/chains";
import { privateKeyToAccount } from "viem/accounts";

const publicClient = createPublicClient({
  chain: mainnet,
  transport: http(),
});

const walletClient = createWalletClient({
  chain: mainnet,
  transport: http(),
  account: privateKeyToAccount("0x..."),
});

Read contract:

const balance = await publicClient.readContract({
  address: "0x...",
  abi: erc20Abi,
  functionName: "balanceOf",
  args: [userAddress],
});

Write contract:

const hash = await walletClient.writeContract({
  address: "0x...",
  abi: erc20Abi,
  functionName: "transfer",
  args: [recipient, amount],
});

const receipt = await publicClient.waitForTransactionReceipt({ hash });

</quick_start>

<client_types>

Client	Purpose	Example Use
PublicClient	Reading blockchain data	getBlockNumber(), readContract()
WalletClient	Transaction signing/sending	sendTransaction(), signMessage()
TestClient	Testing and simulation	mine(), setBalance()
BundlerClient	ERC-4337 User Operations	sendUserOperation()
</client_types>

**Unit conversions:**

import { parseEther, formatEther, parseUnits, formatUnits } from "viem";

parseEther("1.5");           // 1500000000000000000n
formatEther(1500000000000000000n);  // "1.5"
parseUnits("100", 6);        // 100000000n (USDC)
formatUnits(100000000n, 6);  // "100"

Address utilities:

import { getAddress, isAddress } from "viem";

getAddress("0xabc...");  // Checksummed address
isAddress("0x...");      // Validates format

**Banned:** SSRF protection for config-sourced URLs (they're developer-controlled)

Required:

• Lazy initialization for chain resolution
• Client caching by network name
• WebSocket cleanup on destroy/refresh
• Type-safe ABI interactions

<success_criteria>

• Context7 docs fetched for current API
• Uses lazy chain resolution
• Caches clients by network name
• Type-safe ABI interactions
• Proper error handling for blockchain ops </success_criteria>