Contract Verification Skill

Overview

This Skill helps verify smart contracts on Blockscout (MIDL staging network) using a proven method with 100% success rate. Use this when you need to verify deployed contracts, troubleshoot verification failures, or ensure contracts are publicly verifiable.

When to Use This Skill

Apply this Skill whenever:

•User wants to verify a deployed contract on Blockscout
•User is getting "bytecode doesn't match" errors
•User needs to verify existing contracts
•User is deploying new contracts and wants verification to work

The Proven Method (100% Success Rate)

Key Principle

Deploy and verify with EXACT matching compiler settings!

The bytecode must match perfectly between deployment and verification. Even a tiny difference will cause verification to fail.

Critical Settings That Must Match

•Solidity Version - 0.8.24 vs 0.8.28 produces different bytecode
•Optimizer Setting - enabled vs disabled changes bytecode significantly
•Optimizer Runs - 200 vs 1000 affects optimization
•EVM Version - paris, shanghai, etc.

Network Information

MIDL Staging Network:

•RPC: https://rpc.staging.midl.xyz
•Chain ID: 15001 (0x3a99)
•Blockscout: https://blockscout.staging.midl.xyz
•Blockscout API: https://blockscout.staging.midl.xyz/api

Step-by-Step Verification Process

For New Deployments

Step 1: Use Exact Pragma Versions

❌ Wrong (Ambiguous):

solidity

pragma solidity ^0.8.0;  // Hardhat picks first matching compiler
pragma solidity ^0.8.24; // Still ambiguous!

✅ Correct (Exact):

solidity

pragma solidity 0.8.24;  // Forces specific compiler

Why this matters: With multiple compilers in hardhat.config.ts, Hardhat picks the first one that matches. Exact version = predictable compilation.

Step 2: Deploy Contract

bash

cd midl-example
npx hardhat deploy --network regtest --tags <tag>

Save the contract address!

Step 3: Verify Immediately

bash

# Without constructor args
npx hardhat verify --network regtest <ADDRESS>

# With constructor args
npx hardhat verify --network regtest <ADDRESS> "arg1" arg2 ...

For Existing Contracts

Step 1: Get Contract Address Ask user for the deployed contract address.

Step 2: Decode Compiler Version from Bytecode

bash

# Get deployed bytecode
curl -s -X POST https://rpc.staging.midl.xyz \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_getCode","params":["<ADDRESS>","latest"],"id":1}' \
  | jq -r '.result' | tail -c 20

Decode version from suffix:

•000818 = Solidity 0.8.24
•00081c = Solidity 0.8.28

Formula: 00[major][minor in hex]

•0x18 = 24 decimal → 0.8.24
•0x1c = 28 decimal → 0.8.28

Step 3: Update Contract Pragma Find the contract source file and change pragma to exact version:

solidity

pragma solidity 0.8.24;  // Not ^0.8.24

Step 4: Find Constructor Arguments (if needed)

bash

# Search deployment scripts
grep -r "deploy.*ContractName" midl-example/deploy/

Look for midl.deploy("ContractName", [args...]) and note the arguments.

Step 5: Recompile and Verify

bash

cd midl-example
npx hardhat compile --force
npx hardhat verify --network regtest <ADDRESS> [args...]

Common Issues and Solutions

Issue: "Bytecode doesn't match"

Cause: Compiler version or settings mismatch

Fix:

•Get bytecode from chain
•Decode compiler version
•Update pragma to exact version
•Recompile with --force
•Verify again

Issue: "Contract is being compiled with X but deployed with Y"

Cause: Pragma allows multiple versions (e.g., ^0.8.24)

Fix:

solidity

// Change from
pragma solidity ^0.8.24;

// To exact
pragma solidity 0.8.24;

Issue: Constructor Arguments Missing

Fix:

•Find deployment script
•Extract constructor args from midl.deploy() call
•Add to verify command: npx hardhat verify ... arg1 arg2 ...

Examples of Successful Verifications

SimpleTest (no constructor)

bash

# Contract: 0xde6c29923d7BB9FDbcDfEC54E7e726894B982593
# Compiler: 0.8.24 with optimizer

# 1. Updated pragma
pragma solidity 0.8.24;

# 2. Compiled
npx hardhat compile --force

# 3. Verified
npx hardhat verify --network regtest 0xde6c29923d7BB9FDbcDfEC54E7e726894B982593

CollateralERC20 (with constructor)

bash

# Contract: 0xca0daeff9cB8DED3EEF075Df62aDBb1522479639
# Compiler: 0.8.24 with optimizer
# Constructor: "Test Token", "TT", 100000000000

# 1. Updated pragma
pragma solidity 0.8.24;

# 2. Compiled
npx hardhat compile --force

# 3. Verified with args
npx hardhat verify --network regtest \
  0xca0daeff9cB8DED3EEF075Df62aDBb1522479639 \
  "Test Token" "TT" 100000000000

Verified Contracts (Proof of Success)

All verified on staging network: https://blockscout.staging.midl.xyz

•SimpleTest - 0xde6c29923d7BB9FDbcDfEC54E7e726894B982593 ✅
•MessageBoard - 0x479fa7d6eAE6bF7B4a0Cc6399F7518aA3Cd07580 ✅
•CollateralERC20 - 0xca0daeff9cB8DED3EEF075Df62aDBb1522479639 ✅
•RuneERC20 - 0x29cf3A9B709f94Eb46fBbA67753B90E721ddC9Ed ✅

Success Rate: 4/4 (100%)

Hardhat Configuration Requirements

Your hardhat.config.ts must have:

typescript

import "@nomicfoundation/hardhat-verify";

etherscan: {
  apiKey: {
    regtest: "no-api-key-needed"
  },
  customChains: [
    {
      network: "regtest",
      chainId: 15001,
      urls: {
        apiURL: "https://blockscout.staging.midl.xyz/api",
        browserURL: "https://blockscout.staging.midl.xyz"
      }
    }
  ]
},
sourcify: {
  enabled: false
}

Quick Commands Reference

bash

# Get bytecode version
curl -s -X POST https://rpc.staging.midl.xyz \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","method":"eth_getCode","params":["<ADDRESS>","latest"],"id":1}' \
  | jq -r '.result' | tail -c 20

# Find deployment script
grep -r "deploy.*ContractName" midl-example/deploy/

# Compile and verify
cd midl-example
npx hardhat compile --force
npx hardhat verify --network regtest <ADDRESS> [args...]

Important Reminders

•Always use EXACT pragma versions (0.8.24, not ^0.8.24)
•Verify immediately after deployment when settings are fresh
•Document constructor arguments in deployment scripts
•Check bytecode to determine compiler version for existing contracts
•Recompile with --force before verifying to ensure fresh artifacts

Resources

For detailed guide, see: CONTRACT_VERIFICATION_GUIDE.md in the MIDL MCP repository.