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viem-celo

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Viem with Celo chain configuration. Use when working with Celo blockchain interactions, public client setup, contract reads/writes, transaction encoding, or feeCurrency. Triggers on: "viem", "celo client", "publicClient", "readContract", "writeContract", "encodeFunctionData", "feeCurrency", "celo RPC".

QUICK START

How to use this skill

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  2. Copy the prompt below and paste it into your agent.
  3. Review the proposed files and risks before you approve installation.
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I want to install this Agent Skill for this project in Codex.

Source SKILL.md: https://github.com/majiayu000/claude-skill-registry/blob/HEAD/skills/development/viem-celo/SKILL.md

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Project Setup

Public Client (apps/api/src/lib/celo-client.ts)

import { createPublicClient, http } from 'viem';
import { celo } from 'viem/chains';

export const celoClient = createPublicClient({
  chain: celo,
  transport: http(process.env.CELO_RPC_URL || 'https://forno.celo.org'),
});

Chain Config

  • Chain: Celo Mainnet
  • Chain ID: 42220
  • Import: import { celo } from 'viem/chains'
  • Default RPC: https://forno.celo.org
  • Block time: ~5 seconds

Common Patterns

Reading Contracts

const result = await celoClient.readContract({
  address: CONTRACT_ADDRESS,
  abi: contractAbi,
  functionName: 'someFunction',
  args: [arg1, arg2],
});

Encoding Transaction Data

import { encodeFunctionData } from 'viem';

const data = encodeFunctionData({
  abi: contractAbi,
  functionName: 'swapIn',
  args: [provider, exchangeId, tokenIn, tokenOut, amountIn, minAmountOut],
});

Format / Parse Units

import { formatUnits, parseUnits } from 'viem';

// Mento tokens: 18 decimals
formatUnits(1000000000000000000n, 18); // "1.0"
parseUnits('100', 18); // 100000000000000000000n

// USDC/USDT: 6 decimals
formatUnits(1000000n, 6); // "1.0"
parseUnits('100', 6); // 100000000n

Address Types

Always use Address type from viem for addresses:

import type { Address } from 'viem';

const addr: Address = '0x765DE816845861e75A25fCA122bb6898B8B1282a';

Celo-Specific: feeCurrency (CIP-64)

Celo supports paying gas fees in tokens other than CELO. Use the feeCurrency field:

const hash = await walletClient.sendTransaction({
  to: '0x...',
  data: '0x...',
  feeCurrency: '0x765DE816845861e75A25fCA122bb6898B8B1282a', // Pay gas in USDm
});

Common fee currencies on Celo:

  • USDm (cUSD): 0x765DE816845861e75A25fCA122bb6898B8B1282a
  • USDC: 0xcebA9300f2b948710d2653dD7B07f33A8B32118C

Environment Variables

VariableDescription
CELO_RPC_URLCelo RPC endpoint (defaults to https://forno.celo.org)

Important Notes

  • All Mento stablecoin tokens use 18 decimals
  • USDC and USDT on Celo use 6 decimals
  • Use getTokenDecimals() from packages/shared to get correct decimals
  • Always lowercase addresses when using them as map keys
  • The project uses viem v2 — check package.json for exact version