name	description
viem-chains	Use when configuring blockchain chains with viem. Ensures correct chain imports from viem/chains before falling back to defineChain.

Viem Chain Configuration

Workflow

When working with viem chain configurations, ALWAYS follow this order:

1. First, check the official viem chains

   • Fetch: https://github.com/wevm/viem/blob/main/src/chains/index.ts
   • Look for the chain export (e.g., monad, arbitrum, polygon)

2. If the chain exists in viem/chains:

   import { monad } from 'viem/chains'

3. Only if the chain is NOT in viem/chains, use defineChain:

   import { defineChain } from 'viem'
   
   export const customChain = defineChain({
     id: 12345,
     name: 'Custom Chain',
     nativeCurrency: { name: 'ETH', symbol: 'ETH', decimals: 18 },
     rpcUrls: {
       default: { http: ['https://rpc.example.com'] },
     },
   })

Why this matters

• viem maintains up-to-date chain configurations
• Built-in chains include correct RPC URLs, block explorers, and native currency
• Avoids duplicating or misconfiguring chain data
• Ensures compatibility with future viem updates

Reference

Official viem chains source: https://github.com/wevm/viem/blob/main/src/chains/index.ts