---

name: celo-dev

description: End-to-end Celo development playbook (Feb 2026). Prefer viem for all client/transaction code (native fee currency support via CIP-64). Use thirdweb for wallet connection and React dApps. Foundry for smart contract development. Covers fee abstraction (pay gas in USDC/USDT/USDm), MiniPay Mini Apps, stablecoin integration, and AI agent infrastructure (ERC-8004 trust + x402 payments).

user-invocable: true

---

Celo Development Skill (viem-first)

What this Skill is for

Use this Skill when the user asks for:

• Celo dApp UI work (React / Next.js)

• Wallet connection + fee currency selection

• Transactions paying gas in stablecoins (USDC, USDT, USDm)

• MiniPay Mini App development

• Smart contract development, testing, and deployment

• Stablecoin integration (Mento + bridged)

• AI agent infrastructure (ERC-8004 identity/reputation, x402 payments)

Default stack decisions (opinionated)

1. Client SDK: viem first

• viem is REQUIRED for fee abstraction (ethers.js/web3.js don't support feeCurrency)

• Use viem/celo for Celo-specific transaction serialization

• Never use ethers.js for new Celo projects

import { createWalletClient, custom } from "viem"; 

import { celo } from "viem/chains";  



const walletClient = createWalletClient({   

  chain: celo,   

  transport: custom(window.ethereum), 

}); 

2. UI & Wallets: thirdweb

• Use thirdweb SDK for wallet connection and React components

• ConnectButton supports 500+ wallets including MiniPay

• Built-in support for Celo chains

import { ConnectButton } from "thirdweb/react"; 

import { celo } from "thirdweb/chains";  



<ConnectButton client={client} chain={celo} /> 

3. Fee Abstraction: always offer stablecoin gas

Celo's killer feature: pay gas fees in ERC-20 tokens without paymasters or relayers.

• Use adapter addresses for 6-decimal tokens (USDC, USDT) - adapters normalize decimals

• Use token addresses directly for 18-decimal tokens (USDm, EURm, REALm) - no adapter needed

• Requires viem (ethers.js/web3.js don't support feeCurrency)

• Only works with Celo-native wallets (MiniPay) or custom implementations

import { serializeTransaction } from "viem/celo"; 

import { parseGwei, parseEther } from "viem";  



// For 6-decimal tokens (USDC, USDT): use ADAPTER address 

const USDC_ADAPTER = "0x2F25deB3848C207fc8E0c34035B3Ba7fC157602B";  



// For 18-decimal tokens (USDm, EURm): use TOKEN address directly 

const USDM_TOKEN = "0x765DE816845861e75A25fCA122bb6898B8B1282a";  



const serialized = serializeTransaction({   

  chainId: 42220,   

  gas: 21001n,   

  feeCurrency: USDC_ADAPTER, // or USDM_TOKEN for USDm   

  maxFeePerGas: parseGwei("20"),   

  maxPriorityFeePerGas: parseGwei("2"),   

  nonce: 69,   

  to: "0x1234512345123451234512345123451234512345",   

  value: parseEther("0.01"), 

}); 

4. Smart Contracts: Foundry

• Use Foundry (forge, cast, anvil) for all contract development

• Fast compilation, powerful testing, built-in fuzzing

• Native Celo verification support via Celoscan API

# Install Foundry 

curl -L https://foundry.paradigm.xyz | bash && foundryup  



# Create project 

forge init my-project && cd my-project  



# Deploy to Celo Sepolia 

forge script script/Deploy.s.sol \   

  --rpc-url https://forno.celo-sepolia.celo-testnet.org \   

  --broadcast --verify 

5. MiniPay: mobile-first stablecoin UX

• Detect MiniPay via window.ethereum?.isMiniPay

• Users have stablecoins (USDm, USDC), not CELO

• Hide "Connect Wallet" button - connection is implicit

• Test via MiniPay Site Tester with ngrok

function isMiniPay(): boolean {   

  return typeof window !== "undefined" &&          

      window.ethereum?.isMiniPay === true; 

} 

6. AI Agents: ERC-8004 + x402

For AI agent development on Celo:

• ERC-8004: On-chain identity, reputation, and trust verification

• x402: HTTP-native micropayments with stablecoins

// Verify agent trust before interaction 

const summary = await reputationRegistry.getSummary(agentId); 

if (summary.averageScore >= 80) {   

  // Make paid request to trusted agent   

  const response = await fetchWithPayment(serviceUrl); 

} 

Operating procedure

1. Classify the task layer

| Layer | Tools |

|-------|-------|

| UI/wallet/hooks | viem + thirdweb |

| Scripts/backend | viem directly |

| Smart contracts | Foundry (forge) |

| MiniPay apps | MiniPay detection + stablecoin UX |

| AI agents | ERC-8004 + x402 |

2. Pick the right fee currency approach

| Scenario | Approach |

|----------|----------|

| User has MiniPay | Offer fee currency selection |

| User has MetaMask | Must pay in CELO (no fee abstraction) |

| Server-side/scripts | Always use fee currency with viem |

3. Implement with Celo-specific correctness

Always be explicit about:

• Network: Mainnet (42220) vs Sepolia (11142220)

• Fee currency: Adapter address (6-decimal) vs token address (18-decimal)

• Wallet compatibility: MiniPay supports fee abstraction, MetaMask does not

4. Add tests

• Test both CELO and fee currency transactions separately

• Test wallet connection with MiniPay detection

• For contracts, use forge test with fuzzing

• For MiniPay apps, test in Site Tester on real device

5. Deliverables

When implementing changes, provide:

• Exact files changed

• Commands to install/build/test/deploy

• Fee currency addresses used (mainnet vs testnet)

• Wallet compatibility notes

Quick reference

Networks

| Network | Chain ID | RPC Endpoint | Explorer |

|---------|----------|--------------|----------|

| Mainnet | 42220 | https://forno.celo.org | https://celoscan.io |

| Sepolia | 11142220 | https://forno.celo-sepolia.celo-testnet.org | https://sepolia.celoscan.io |

Fee Currency Addresses - Mainnet

Why adapters? Celo's gas calculations use 18 decimals internally. Tokens with different decimals (like USDC/USDT with 6 decimals) need adapter contracts to normalize the decimal conversion. Native Mento stablecoins (USDm, EURm, REALm) are already 18 decimals, so you use their token address directly.

| Token | Decimals | feeCurrency Address | Type |

|-------|----------|---------------------|------|

| USDC | 6 | 0x2F25deB3848C207fc8E0c34035B3Ba7fC157602B | Adapter |

| USDT | 6 | 0x0e2a3e05bc9a16f5292a6170456a710cb89c6f72 | Adapter |

| USDm | 18 | 0x765DE816845861e75A25fCA122bb6898B8B1282a | Token (no adapter needed) |

| EURm | 18 | 0xD8763CBa276a3738E6DE85b4b3bF5FDed6D6cA73 | Token (no adapter needed) |

| REALm | 18 | 0xe8537a3d056DA446677B9E9d6c5dB704EaAb4787 | Token (no adapter needed) |

Fee Currency Addresses - Celo Sepolia

| Token | Decimals | feeCurrency Address | Type |

|-------|----------|---------------------|------|

| USDC | 6 | 0x4822e58de6f5e485eF90df51C41CE01721331dC0 | Adapter |

| USDm | 18 | 0xdE9e4C3ce781b4bA68120d6261cbad65ce0aB00b | Token (no adapter needed) |

| EURm | 18 | 0xA99dC247d6b7B2E3ab48a1fEE101b83cD6aCd82a | Token (no adapter needed) |

Core Protocol Contracts - Mainnet

| Contract | Address |

|----------|---------|

| CELO Token | 0x471EcE3750Da237f93B8E339c536989b8978a438 |

| FeeCurrencyDirectory | 0x15F344b9E6c3Cb6F0376A36A64928b13F62C6276 |

| Registry | 0x000000000000000000000000000000000000ce10 |

Stablecoin Tokens - Mainnet

| Token | Address | Decimals |

|-------|---------|----------|

| USDm | 0x765DE816845861e75A25fCA122bb6898B8B1282a | 18 |

| EURm | 0xD8763CBa276a3738E6DE85b4b3bF5FDed6D6cA73 | 18 |

| USDC | 0xcebA9300f2b948710d2653dD7B07f33A8B32118C | 6 |

| USDT | 0x48065fbbe25f71c9282ddf5e1cd6d6a887483d5e | 6 |

Progressive disclosure (read when needed)

Detailed documentation for each topic is available in the celo-org/agent-skills repository:

Client & Frontend

• viem - TypeScript client with fee currency support

• wagmi - React hooks for Celo dApps

• thirdweb - Full-stack Web3 development

• evm-wallet-integration - Wallet connection patterns

Celo Features

• fee-abstraction - Pay gas with stablecoins

• minipay-integration - MiniPay Mini App development

• celo-stablecoins - USDT, USDC, USDm, EURm, BRLm, XOFm, KESm, PHPm, COPm, NGNm, GHSm, GBPm, ZARm, CADm, AUDm, CHFm, JPYm, BRLA, VCHF, VEUR, VGBP, USDGLO, agEURA + COPM

• celo-rpc - Blockchain interaction via RPC

Smart Contracts

• evm-foundry - Foundry development (recommended)

• contract-verification - Celoscan, Blockscout, Sourcify

AI Agent Infrastructure

• 8004 - ERC-8004 Agent Trust Protocol

• x402 - HTTP-native agent payments

DeFi & Bridging

• celo-defi - DeFi protocol integration

• bridging - Asset bridging to/from Celo

Scaffolding

• celo-composer - Project templates and scaffolding

Official Documentation

• Token Contracts - All token addresses

• Core Contracts - Protocol contract addresses

• Fee Currency - Fee abstraction guide

• MiniPay - Mini App development

Why Celo?

• Fee abstraction: Pay gas in stablecoins without paymasters

• Sub-second finality: ~1 second block times

• Low fees: Gas costs under $0.001

• Mobile-first: MiniPay with 12.6M activations

• AI-native: ERC-8004 trust + x402 payments built for agents

• Stablecoin ecosystem: Native USDT, USDC, USDm, EURm, BRLm, XOFm, KESm, PHPm, COPm, NGNm, GHSm, GBPm, ZARm, CADm, AUDm, CHFm, JPYm, BRLA, VCHF, VEUR, VGBP, USDGLO, agEURA + COPM